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Forests, Volume 8, Issue 5 (May 2017)

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Cover Story We test whether low-cost drones can accurately estimate height and biomass in monoculture [...] Read more.
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Open AccessArticle Potential of Windbreak Trees to Reduce Carbon Emissions by Agricultural Operations in the US
Forests 2017, 8(5), 138; doi:10.3390/f8050138
Received: 1 March 2017 / Revised: 6 April 2017 / Accepted: 18 April 2017 / Published: 26 April 2017
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Abstract
Along with sequestering C in forest, trees on farms are able to contribute to greenhouse mitigation through emission avoidance mechanisms. To evaluate the magnitude of these contributions, emission avoidance contributions for field and farmstead windbreak designs in regions across the United States were
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Along with sequestering C in forest, trees on farms are able to contribute to greenhouse mitigation through emission avoidance mechanisms. To evaluate the magnitude of these contributions, emission avoidance contributions for field and farmstead windbreak designs in regions across the United States were estimated, along with greenhouse gas (GHG) emission budgets for corn, soybean, winter wheat, and potato operations. We looked at farming scenarios with large (600 ha), mid (300 ha), and small-size (60 ha) farms containing farmsteads built before and after 2000, and growing different cropping systems. Windbreak scenarios were assumed to be up to 5% of the crop area for field windbreaks, while emission avoidance for farmstead windbreaks were assumed to provide a 10% and 25% reduction in energy usage for space conditioning and heating, respectively. Total reduction of C equivalent (CE) emissions by windbreaks on farm systems ranged from a low of 0.9 Mg CE year−1 for a 60-ha farm with a home built before 2000 to 39.1 Mg CE year−1 for a 600-ha farm with a home built after 2000. By reducing fossil fuel usage from farm operations, windbreaks provide a promising strategy for reducing GHG emissions from agriculture in the USA. Full article
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Open AccessArticle Modeling Variation in Crown Profile with Tree Status and Cardinal Directions for Planted Larix olgensis Henry Trees in Northeast China
Forests 2017, 8(5), 139; doi:10.3390/f8050139
Received: 25 January 2017 / Revised: 19 April 2017 / Accepted: 19 April 2017 / Published: 26 April 2017
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Abstract
Crown profile models were developed for north, east, south, and west crown directions of dominant trees, intermediate trees, and suppressed trees in planted stands of Larix olgensis Henry in Northeast China. A total of 139 sample trees were randomly selected, and all branches
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Crown profile models were developed for north, east, south, and west crown directions of dominant trees, intermediate trees, and suppressed trees in planted stands of Larix olgensis Henry in Northeast China. A total of 139 sample trees were randomly selected, and all branches of each tree were measured. A segmented power equation, segmented polynomial equation, modified Weibull equation, and Kozak equation were selected as the candidate models. A traditional approach that did not consider the differences between tree status and crown directions was also developed. Three steps were conducted to analyze the effect of tree status (dominant, intermediate, and suppressed tree) and crown direction (north, east, south, and west) on the crown profiles using a dummy variable approach. Step 1 considered only tree status, Step 2 considered only crown direction, and Step 3 took both tree status and crown direction into account. Nonlinear mixed-effects model was used to express the effect of individual tree level on crown shape, and was also compared to the ordinary least-squares and generalized least-squares model. The results demonstrated that the modified Kozak equation showed good performance in the crown profile description. The nonlinear mixed-effects model significantly improved the model performance compared to the ordinary least-squares and generalized least-squares model. There were differences among the crown profiles among the four directions of dominant, intermediate, and suppressed trees. South-oriented crowns had the tendency to be the largest, which is likely to be mainly a result of light conditions. The competition status of the subject tree was the main reason leading to an asymmetric crown. Individual trees with strong competition levels had smaller crowns. Full article
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Open AccessArticle The Influence of Monsoon Climate on Latewood Growth of Southwestern Ponderosa Pine
Forests 2017, 8(5), 140; doi:10.3390/f8050140
Received: 16 March 2017 / Revised: 11 April 2017 / Accepted: 19 April 2017 / Published: 25 April 2017
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Abstract
The North American Monsoon delivers warm season precipitation to much of the southwestern United States, yet the importance of this water source for forested ecosystems in the region is not well understood. While it is widely accepted that trees in southwestern forests use
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The North American Monsoon delivers warm season precipitation to much of the southwestern United States, yet the importance of this water source for forested ecosystems in the region is not well understood. While it is widely accepted that trees in southwestern forests use winter precipitation for earlywood production, the extent to which summer (monsoon season) precipitation supports latewood production is unclear. We used tree ring records, local climate data, and stable isotope analyses (δ18O) of water and cellulose to examine the importance of monsoon precipitation for latewood production in mature ponderosa pine (Pinus ponderosa Dougl.) in northern Arizona. Our analyses identified monsoon season vapor pressure deficit (VPD) and Palmer Drought Severity Index (PDSI) as significant effects on latewood growth, together explaining 39% of latewood ring width variation. Stem water and cellulose δ18O analyses suggest that monsoon precipitation was not directly used for latewood growth. Our findings suggest that mature ponderosa pines in this region utilize winter precipitation for growth throughout the entire year. The influence of monsoon precipitation on growth is indirect and mediated by its effect on atmospheric moisture stress (VPD). Together, summer VPD and antecedent soil moisture conditions have a strong influence on latewood growth. Full article
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Open AccessArticle Riparian Partial Harvesting and Upland Clear Cutting Alter Bird Communities in a Boreal Mixedwood Forest
Forests 2017, 8(5), 141; doi:10.3390/f8050141
Received: 22 February 2017 / Revised: 4 April 2017 / Accepted: 18 April 2017 / Published: 25 April 2017
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Abstract
Forested buffer strips are typically prescribed around water bodies during forest harvesting operations to minimize effects on aquatic communities and to maintain fish and wildlife habitat. It has been argued that the systematic application of these buffer strips in the boreal forest results
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Forested buffer strips are typically prescribed around water bodies during forest harvesting operations to minimize effects on aquatic communities and to maintain fish and wildlife habitat. It has been argued that the systematic application of these buffer strips in the boreal forest results in the creation of an unnatural distribution of linear patterns of older-growth forest which is not consistent with the current emulating natural disturbance paradigm. We conducted a multi-year, temporally and spatially controlled, manipulative experiment to investigate the short-term impacts of an alternative practice of riparian partial harvesting and upland clear cutting on breeding and migrating forest birds. Effects on breeding bird community composition were assessed using a modified point counting method. Effects of harvesting on habitat utilization during fall migration were assessed by mist-netting. Breeding bird communities changed significantly post-harvest, but riparian communities diverged less from the pre-harvest condition than upland communities. Populations of early successional/edge species increased post-harvest and forest dependent species declined. Population declines tended to be smaller in the riparian partial cuts than in the upland clear cuts. Capture rates and movement patterns of fall migrants were unaffected by riparian partial harvesting, but catches of Tennessee Warbler (Oreothlypis peregrina), Nashville Warbler (Oreothlypis ruficapilla), Palm Warbler (Setophaga palmarum) and Yellow-rumped Warbler (Setophaga coronata) increased in upland clear cuts. Our results suggest that partial harvesting in riparian reserves may be a viable management option that accommodates the needs of forest dependent birds. Full article
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Open AccessArticle Ecosystem Service Valuation through Wildfire Risk Mitigation: Design, Governance, and Outcomes of the Flagstaff Watershed Protection Project (FWPP)
Forests 2017, 8(5), 142; doi:10.3390/f8050142
Received: 28 February 2017 / Revised: 17 April 2017 / Accepted: 19 April 2017 / Published: 26 April 2017
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Abstract
The full value of benefits rendered from healthy watersheds is difficult to estimate, and ecosystem service (ES) valuation sometimes necessarily occurs in the form of costs incurred or avoided. Along these lines, social-ecological systems including Payment for Watershed Services (PWS) are increasing in
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The full value of benefits rendered from healthy watersheds is difficult to estimate, and ecosystem service (ES) valuation sometimes necessarily occurs in the form of costs incurred or avoided. Along these lines, social-ecological systems including Payment for Watershed Services (PWS) are increasing in frequency and can help land management entities to bridge budget shortfalls for funding needed watershed restoration forestry treatments. The Flagstaff Watershed Protection Project (FWPP) is a bond-financed wildfire risk mitigation partnership and PWS program in Northern Arizona, the only forest management project that utilizes a municipal bond as the financial mechanism in conjunction with a partnership governance structure to invest in federal land management. The purpose of this research was to describe this new governance structure to understand the potential benefits to communities and federal land management agencies for protecting watershed services. Data were derived from document review and key informant interviews (n = 9). FWPP institutional design and governance structures were tailored to maximize community strengths and encompassed several advantages over traditional federal land management models; these advantages include increased collaboration and institutional support, financial security, and public approval. The FWPP represents an innovative PWS system that can help showcase unique community and federal forest management partnerships that benefit watershed health in western US communities. Full article
(This article belongs to the Special Issue Management Strategies for Forest Ecosystem Services)
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Open AccessArticle Genetic Diversity in Relict and Fragmented Populations of Ulmus glabra Hudson in the Central System of the Iberian Peninsula
Forests 2017, 8(5), 143; doi:10.3390/f8050143
Received: 16 February 2017 / Revised: 19 April 2017 / Accepted: 20 April 2017 / Published: 27 April 2017
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Abstract
Ulmus glabra Hudson, or Wych elm, occurs as fragmented and relict natural populations in the Central System, which acts as a refugium in the Iberian Peninsula. Considering the importance of the Central System populations of U. glabra, the main objective was to
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Ulmus glabra Hudson, or Wych elm, occurs as fragmented and relict natural populations in the Central System, which acts as a refugium in the Iberian Peninsula. Considering the importance of the Central System populations of U. glabra, the main objective was to assess their genetic diversity using nuclear microsatellite markers. A total of 360 different genotypes were detected in the 427 U. glabra individuals analyzed. Wych elm populations showed a highly significant genetic differentiation (24%; p = 0.0001). Of the 22 populations studied, population of Rozas de Puerto Real (ROZ) showed the highest values of effective number of alleles (2.803), mean Shannon’s diversity (1.047) and expected heterozygosity (0.590). Populations of ROZ and Mombeltrán (MOM) showed the highest values of observed heterozygosity (0.838 and 0.709, respectively), and highly negative values for inbreeding coefficient (−0.412 and −0.575, respectively). Also, most of putative hybrids (50 of 55) were observed in these two populations. Demographic analysis revealed signals for recent (four populations) and ancestral (fifteen populations) bottlenecks. Fragmented populations with diminishing number of individuals, along with anthropogenic intervention and Dutch elm disease (DED), are the main threats to U. glabra populations. From a future perspective, the information generated can be considered in the formulation of conservation strategies for U. glabra populations in the Central System. Full article
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Open AccessFeature PaperArticle Invasive Everywhere? Phylogeographic Analysis of the Globally Distributed Tree Pathogen Lasiodiplodia theobromae
Forests 2017, 8(5), 145; doi:10.3390/f8050145
Received: 19 March 2017 / Revised: 20 April 2017 / Accepted: 22 April 2017 / Published: 27 April 2017
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Abstract
Fungi in the Botryosphaeriaceae are important plant pathogens that persist endophytically in infected plant hosts. Lasiodiplodia theobromae is a prominent species in this family that infects numerous plants in tropical and subtropical areas. We characterized a collection of 255 isolates of L. theobromae
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Fungi in the Botryosphaeriaceae are important plant pathogens that persist endophytically in infected plant hosts. Lasiodiplodia theobromae is a prominent species in this family that infects numerous plants in tropical and subtropical areas. We characterized a collection of 255 isolates of L. theobromae from 52 plants and from many parts of the world to determine the global genetic structure and a possible origin of the fungus using sequence data from four nuclear loci. One to two dominant haplotypes emerged across all loci, none of which could be associated with geography or host; and no other population structure or subdivision was observed. The data also did not reveal a clear region of origin of the fungus. This global collection of L. theobromae thus appears to constitute a highly connected population. The most likely explanation for this is the human-mediated movement of plant material infected by this fungus over a long period of time. These data, together with related studies on other Botryosphaeriaceae, highlight the inability of quarantine systems to reduce the spread of pathogens with a prolonged latent phase. Full article
(This article belongs to the Special Issue Forest Pathology and Plant Health)
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Open AccessArticle Spatial Heterogeneity of the Forest Canopy Scales with the Heterogeneity of an Understory Shrub Based on Fractal Analysis
Forests 2017, 8(5), 146; doi:10.3390/f8050146
Received: 15 February 2017 / Revised: 21 April 2017 / Accepted: 25 April 2017 / Published: 27 April 2017
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Abstract
Spatial heterogeneity of vegetation is an important landscape characteristic, but is difficult to assess due to scale-dependence. Here we examine how spatial patterns in the forest canopy affect those of understory plants, using the shrub Canada buffaloberry (Shepherdia canadensis (L.) Nutt.) as
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Spatial heterogeneity of vegetation is an important landscape characteristic, but is difficult to assess due to scale-dependence. Here we examine how spatial patterns in the forest canopy affect those of understory plants, using the shrub Canada buffaloberry (Shepherdia canadensis (L.) Nutt.) as a focal species. Evergreen and deciduous forest canopy and buffaloberry shrub presence were measured with line-intercept sampling along ten 2-km transects in the Rocky Mountain foothills of west-central Alberta, Canada. Relationships between overstory canopy and understory buffaloberry presence were assessed for scales ranging from 2 m to 502 m. Fractal dimensions of both canopy and buffaloberry were estimated and then related using box-counting methods to evaluate spatial heterogeneity based on patch distribution and abundance. Effects of canopy presence on buffaloberry were scale-dependent, with shrub presence negatively related to evergreen canopy cover and positively related to deciduous cover. The effect of evergreen canopy was significant at a local scale between 2 m and 42 m, while that of deciduous canopy was significant at a meso-scale between 150 m and 358 m. Fractal analysis indicated that buffaloberry heterogeneity positively scaled with evergreen canopy heterogeneity, but was unrelated to that of deciduous canopy. This study demonstrates that evergreen canopy cover is a determinant of buffaloberry heterogeneity, highlighting the importance of spatial scale and canopy composition in understanding canopy-understory relationships. Full article
(This article belongs to the Special Issue Successional Dynamics of Forest Structure and Function)
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Open AccessArticle Cross-Talk between Physiological and Metabolic Adjustments Adopted by Quercus cerris to Mitigate the Effects of Severe Drought and Realistic Future Ozone Concentrations
Forests 2017, 8(5), 148; doi:10.3390/f8050148
Received: 31 January 2017 / Revised: 24 April 2017 / Accepted: 26 April 2017 / Published: 29 April 2017
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Abstract
Global climate change represents a moving target for plant acclimation and/or adaptation, especially in the Mediterranean basin. In this study, the interactions of severe drought (20% of the effective daily evapotranspiration) and O3 fumigation (80 ppb, 5 h day−1, for
[...] Read more.
Global climate change represents a moving target for plant acclimation and/or adaptation, especially in the Mediterranean basin. In this study, the interactions of severe drought (20% of the effective daily evapotranspiration) and O3 fumigation (80 ppb, 5 h day−1, for 28 consecutive days) on (i) photosynthetic performance, (ii) cell membrane stability, (iii) hydric relations, (iv) accumulation of compatible solutes, and (v) lipophilic antioxidant compounds were investigated in young Quercus cerris plants. In addition to the typical drought-induced stomatal closure, imposition of water withholding dramatically influenced the profile of stress-associated metabolites, i.e., abscisic acid (ABA), proline, and lipophilic antioxidants. However, plants were not able to delay or prevent the negative effects of water deficit, the greatest impacting factor in this study. This translated into a steep decline of photosynthetic efficiency, leaf hydration, and membrane fluidity and permeability. When water stress was coupled with O3, plants orchestrated cross-talk among ABA, proline, and sugar in fully-expanded mature leaves, partially leading to a premature senescence. Full article
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Open AccessArticle Stakeholder Participation in REDD+ Readiness Activities for Three Collaborative Projects in Lao PDR
Forests 2017, 8(5), 150; doi:10.3390/f8050150
Received: 22 January 2017 / Revised: 27 March 2017 / Accepted: 27 April 2017 / Published: 29 April 2017
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Abstract
A key challenge for reducing emission from deforestation and forest degradation (REDD) in developing countries is to balance the power of various stakeholders in decision making. This study explores the forms of stakeholder participation in the implementation of three pilot projects in Laos,
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A key challenge for reducing emission from deforestation and forest degradation (REDD) in developing countries is to balance the power of various stakeholders in decision making. This study explores the forms of stakeholder participation in the implementation of three pilot projects in Laos, with a focus on who actually makes decisions on project activities. We found that stakeholder roles in making decisions were imbalanced. The central government and development partner organizations were the ones who actually fulfill the roles of decision-makers in most project activities. Although local communities were not the key stakeholders in decision making in most activities, their roles seem to have increased in the activities where participatory approaches were applied. Participation of the private sector, non-governmental organizations, academic and research institutes and mass organizations was limited. Opportunities to reach decision-makers regarding project activities came through service contract agreements. Our findings suggest that an understanding of who fulfills the key roles will support a decentralization of decision making by balancing power and redistributing the roles from dominant to weaker stakeholders. In addition, the private sector’s participation may enhance opportunities to harmonize their investments for supporting REDD+ development and reduce the negative impacts on the forests and the environment. Full article
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Open AccessArticle Accuracy of Photogrammetric UAV-Based Point Clouds under Conditions of Partially-Open Forest Canopy
Forests 2017, 8(5), 151; doi:10.3390/f8050151
Received: 20 December 2016 / Revised: 20 April 2017 / Accepted: 27 April 2017 / Published: 30 April 2017
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Abstract
This study focuses on the horizontal and vertical accuracy of point-clouds based on unmanned aerial vehicle (UAV) imagery. The DJI Phantom 3 Professional unmanned aerial vehicle and Agisoft PhotoScan Professional software were used for the evaluation. Three test sites with differing conditions (canopy
[...] Read more.
This study focuses on the horizontal and vertical accuracy of point-clouds based on unmanned aerial vehicle (UAV) imagery. The DJI Phantom 3 Professional unmanned aerial vehicle and Agisoft PhotoScan Professional software were used for the evaluation. Three test sites with differing conditions (canopy openness, slope, terrain complexity, etc.) were used for comparison. The accuracy evaluation was aimed on positions of points placed on the ground. This is often disregarded under forest conditions as it is not possible to photogrammetrically reconstruct terrain that is covered by a fully-closed forest canopy. Therefore, such a measurement can only be conducted when there are gaps in the canopy or under leaf-off conditions in the case of deciduous forests. The reported sub-decimetre horizontal accuracy and vertical accuracy lower than 20 cm have proven that the method is applicable for survey, inventory, and various other tasks in forests. An analysis of ground control point (GCP) quantity and configuration showed that the quantity had only a minor effect on the accuracy in cases of plots with ~1-hectare area when using the aforementioned software. Therefore, methods increasing quality (precision, accuracy) of GCP positions should be preferred over the increase of quantity alone. Full article
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Open AccessArticle Microsporogenesis and Induction of Unreduced Pollen with High Temperatures in Rubber Tree Clone RRIM 600
Forests 2017, 8(5), 152; doi:10.3390/f8050152
Received: 11 February 2017 / Revised: 24 April 2017 / Accepted: 27 April 2017 / Published: 2 May 2017
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Abstract
In order to induce unreduced pollens, microsporogenesis and male flower bud (MFB) development were compared in rubber tree clone RRIM 600. We observed strong asynchronism in different MFBs in an inflorescence. Asynchronism of microsporogenesis in different microsporangiums from a MFB was also observed.
[...] Read more.
In order to induce unreduced pollens, microsporogenesis and male flower bud (MFB) development were compared in rubber tree clone RRIM 600. We observed strong asynchronism in different MFBs in an inflorescence. Asynchronism of microsporogenesis in different microsporangiums from a MFB was also observed. The relationship between microsporogenesis and external morphology was examined, which was used to estimate microsporogenesis stages of MFBs. Unreduced pollen was successfully induced by high temperature exposure in this study, with the highest production ratio of about 20.17% at 44 °C. Our findings showed that diplotene to metaphase I may be the most effective stage for unreduced pollen induction, and 42–44 °C may be the suitable treatment temperature in rubber trees. Thus, microsporogenesis of MFBs has been elucidated in detail in the rubber tree clone RRIM 600 and will provide a reference for future breeding studies of rubber trees. Full article
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Open AccessArticle The Effect of Urban Green Spaces on the Urban Thermal Environment and Its Seasonal Variations
Forests 2017, 8(5), 153; doi:10.3390/f8050153
Received: 26 January 2017 / Revised: 19 April 2017 / Accepted: 28 April 2017 / Published: 2 May 2017
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Abstract
Urban green spaces have been shown to decrease land surface temperature (LST) significantly. However, few studies have explored the relationships between urban green spaces and LST across different seasons at different spatial scales. In this study, using Changchun, China as a case study,
[...] Read more.
Urban green spaces have been shown to decrease land surface temperature (LST) significantly. However, few studies have explored the relationships between urban green spaces and LST across different seasons at different spatial scales. In this study, using Changchun, China as a case study, landscape ecology and comparative approaches were employed quantitatively to investigate the effects of the composition and configuration of urban green spaces on the urban thermal environments. LST maps were retrieved from Landsat 8 Thermal Infrared Sensor (TIRS) data acquired on four dates that represented four different seasons, and detailed information of urban green spaces was extracted from high resolution imagery GF-1. Normalized differential vegetation index (NDVI) and six landscape metrics at patch, class, and landscape level were used to characterize the spatial patterns of urban green spaces. The results showed that urban green spaces did have significant cooling effects in all seasons, except for winter, but the effects varied considerably across the different seasons and green types, and seemed to depend on the NDVI and size of urban green spaces. Compared to shape metrics, the negative relationships between the LST and the area and the NDVI of urban green spaces were more significant. Both the composition and configuration of urban green spaces can affect the distribution of LST. Based on findings with one city, given a fixed area of urban green spaces, the number of green patches can positively or negatively affect the LST, depending on if the number is larger than a threshold or not, and the threshold varies according to the given area. These findings provide new perspectives, and further research is also suggested, to generate a better understanding of how urban green spaces affect the urban thermal environment. Full article
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Open AccessArticle Tree Climbing Techniques and Volume Equations for Eschweilera (Matá-Matá), a Hyperdominant Genus in the Amazon Forest
Forests 2017, 8(5), 154; doi:10.3390/f8050154
Received: 13 March 2017 / Revised: 14 April 2017 / Accepted: 27 April 2017 / Published: 3 May 2017
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Abstract
The Eschweilera genus has great ecological and economic importance due to its wide abundance in the Amazon basin. One potential use for the Eschweilera genus is in forest management, where just a few trees are removed per hectare. In order to improve the
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The Eschweilera genus has great ecological and economic importance due to its wide abundance in the Amazon basin. One potential use for the Eschweilera genus is in forest management, where just a few trees are removed per hectare. In order to improve the forest management in the Amazon, this study assessed two critical issues: volume equations fitted for a single genus and the development of a non-destructive method using climbing techniques. The equipment used to measure the sample trees included: climbing rope, ascenders, descenders, and carabiners. To carry out the objectives of this study, 64 trees with diameter at breast height (DBH) ≥ 10 cm were selected and measured in ZF-2 Tropical Forestry Station near the city of Manaus, Brazil. Four single input models with DBH and four dual input models with DBH and merchantable height (H) were tested. The Husch model (V = a × DBHb) presented the best performance (R2 = 0.97). This model does not require the merchantable height, which is an important advantage, because of the difficulty in measuring this variable in tropical forests. When the merchantable height data are collected using accurate methods, the Schumacher and Hall model (V = a × DBHb × Hc) is the most appropriated. Tree climbing techniques with the use of ropes, as a non-destructive method, is a good alternative to measure the merchantable height, the diameter along the stem, and also estimate the tree volume (m3) of the Eschweilera genus in the Amazon basin. Full article
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Open AccessArticle The Effects of Shade, Fertilizer, and Pruning on Eastern Hemlock Trees and Hemlock Woolly Adelgid
Forests 2017, 8(5), 156; doi:10.3390/f8050156
Received: 1 March 2017 / Revised: 19 April 2017 / Accepted: 27 April 2017 / Published: 4 May 2017
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Abstract
Hemlock woolly adelgid (HWA), Adelges tsugae Annand, an invasive insect native to the Pacific Northwest and Asia, is responsible for widespread health decline and mortality of native hemlocks (Tsuga spp.) in the eastern United States. Shading and fertilizer has been found to
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Hemlock woolly adelgid (HWA), Adelges tsugae Annand, an invasive insect native to the Pacific Northwest and Asia, is responsible for widespread health decline and mortality of native hemlocks (Tsuga spp.) in the eastern United States. Shading and fertilizer has been found to affect the survival and health of both HWA and hemlocks. These abiotic factors have been studied separately but not in combination. In this three year study, eastern hemlock trees (1–2 m tall) were treated with pruning, fertilizer, and shade to determine their effects on hemlock tree health and HWA survival and density. Shade cloths were erected over individual trees, granulated fertilizer was applied, and trees were pruned annually. The total number of HWA were counted during the sistens and progrediens adult stages on the low, mid, and high branches on the north, east, south, and west sides of each tree for three years. Survival of aestivating sistens was recorded in artificially, naturally, and unshaded hemlocks. The mean of percent tips alive, branches alive, and foliage density was used to calculate a hemlock health index (scale of 0–100). Shade cloth reduced solar radiation to the trees to levels similar to a naturally-forested hemlock canopy, but did not alter temperature. Trees exposed to shade alone and shade plus fertilizer maintained the greatest HWA density. On unshaded trees, branches on the west side of the tree had lower HWA densities and branches high on the tree had the lowest HWA densities. Pruning plus fertilizer and shading plus fertilizer reduced tree health. Shaded trees had reduced branchlet new growth length. Survival of summer aestivating sistens was nearly twice the survival under artificially- and naturally-shaded trees compared to unshaded trees. There was an inverse density-dependent survival response for aestivating HWA under artificially-shaded and unshaded trees but not naturally-shaded trees. Unshaded hemlock trees had lower HWA densities due to increased mortality of summer aestivating sistens. Unshaded trees had better health and longer new growth branchlets due to increased exposure to solar radiation and lower HWA densities. Silvicultural thinning of hemlocks in forest stands could increase direct sunlight reaching the trees and help decrease HWA densities and improve hemlock health. Full article
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Open AccessArticle Understanding Ecosystem Service Preferences across Residential Classifications near Mt. Baker Snoqualmie National Forest, Washington (USA)
Forests 2017, 8(5), 157; doi:10.3390/f8050157
Received: 28 February 2017 / Revised: 21 April 2017 / Accepted: 2 May 2017 / Published: 6 May 2017
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Abstract
Ecosystem services consistently group together both spatially and cognitively into “bundles”. Understanding socio-economic predictors of these bundles is essential to informing a management approach that emphasizes equitable distribution of ecosystem services. We received 1796 completed surveys from stakeholders of the Mt. Baker-Snoqualmie National
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Ecosystem services consistently group together both spatially and cognitively into “bundles”. Understanding socio-economic predictors of these bundles is essential to informing a management approach that emphasizes equitable distribution of ecosystem services. We received 1796 completed surveys from stakeholders of the Mt. Baker-Snoqualmie National Forest (WA, USA) using both in-person workshops and an online platform. Survey respondents rated the importance of 26 ecosystem services. Subsequent analysis revealed six distinct preference bundles of these services: environmental quality, utilitarian values, heritage values, two types of recreational values, and access and roads. Results suggest that the conceptualizations of these bundles are consistent across socio-demographic groups. Resource agencies that seek to frame dialogue around critical values may want to consider these broadly representative bundle sets as a meaningful organizing framework that would resonate with diverse constituents. Full article
(This article belongs to the Special Issue Management Strategies for Forest Ecosystem Services)
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Open AccessArticle Deadwood Decay in a Burnt Mediterranean Pine Reforestation
Forests 2017, 8(5), 158; doi:10.3390/f8050158
Received: 6 March 2017 / Revised: 11 April 2017 / Accepted: 26 April 2017 / Published: 8 May 2017
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Abstract
Dead wood remaining after wildfires represents a biological legacy for forest regeneration, and its decay is both cause and consequence of a large set of ecological processes. However, the rate of wood decomposition after fires is still poorly understood, particularly for Mediterranean-type ecosystems.
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Dead wood remaining after wildfires represents a biological legacy for forest regeneration, and its decay is both cause and consequence of a large set of ecological processes. However, the rate of wood decomposition after fires is still poorly understood, particularly for Mediterranean-type ecosystems. In this study, we analyzed deadwood decomposition following a wildfire in a Mediterranean pine plantation in the Sierra Nevada Natural and National Park (southeast Spain). Three plots were established over an elevational/species gradient spanning from 1477 to 2053 m above sea level, in which burnt logs of three species of pines were experimentally laid out and wood densities were estimated five times over ten years. The logs lost an overall 23% of their density, although this value ranged from an average 11% at the highest-elevation plot (dominated by Pinus sylvestris) to 32% at an intermediate elevation (with P. nigra). Contrary to studies in other climates, large-diameter logs decomposed faster than small-diameter logs. Our results provide one of the longest time series for wood decomposition in Mediterranean ecosystems and suggest that this process provides spatial variability in the post-fire ecosystem at the scale of stands due to variable speeds of decay. Common management practices such as salvage logging diminish burnt wood and influence the rich ecological processes related to its decay. Full article
(This article belongs to the Special Issue Forest Operations, Engineering and Management)
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Open AccessArticle Climate Drives Episodic Conifer Establishment after Fire in Dry Ponderosa Pine Forests of the Colorado Front Range, USA
Forests 2017, 8(5), 159; doi:10.3390/f8050159
Received: 1 March 2017 / Revised: 20 April 2017 / Accepted: 27 April 2017 / Published: 8 May 2017
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Abstract
In recent years, warming climate and increased fire activity have raised concern about post-fire recovery of western U.S. forests. We assessed relationships between climate variability and tree establishment after fire in dry ponderosa pine forests of the Colorado Front Range. We harvested and
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In recent years, warming climate and increased fire activity have raised concern about post-fire recovery of western U.S. forests. We assessed relationships between climate variability and tree establishment after fire in dry ponderosa pine forests of the Colorado Front Range. We harvested and aged over 400 post-fire juvenile ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga menziesii) trees using an improved tree-ring based approach that yielded annually-resolved dates and then assessed relationships between climate variability and pulses of tree establishment. We found that tree establishment was largely concentrated in years of above-average moisture availability in the growing season, including higher amounts of precipitation and more positive values of the Palmer Drought Severity Index. Under continued climate change, drier conditions associated with warming temperatures may limit forest recovery after fire, which could result in lower stand densities or shifts to non-forested vegetation in some areas. Full article
(This article belongs to the Special Issue Post-Disturbance Forest Management and Regeneration Dynamics)
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Open AccessArticle A Mixed Application of Geographically Weighted Regression and Unsupervised Classification for Analyzing Latex Yield Variability in Yunnan, China
Forests 2017, 8(5), 162; doi:10.3390/f8050162
Received: 8 February 2017 / Revised: 18 April 2017 / Accepted: 26 April 2017 / Published: 11 May 2017
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Abstract
This paper introduces a mixed method approach for analyzing the determinants of natural latex yields and the associated spatial variations and identifying the most suitable regions for producing latex. Geographically Weighted Regressions (GWR) and Iterative Self-Organizing Data Analysis Technique (ISODATA) are jointly applied
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This paper introduces a mixed method approach for analyzing the determinants of natural latex yields and the associated spatial variations and identifying the most suitable regions for producing latex. Geographically Weighted Regressions (GWR) and Iterative Self-Organizing Data Analysis Technique (ISODATA) are jointly applied to the georeferenced data points collected from the rubber plantations in Xishuangbanna (in Yunnan province, south China) and other remotely-sensed spatial data. According to the GWR models, Age of rubber tree, Percent of clay in soil, Elevation, Solar radiation, Population, Distance from road, Distance from stream, Precipitation, and Mean temperature turn out statistically significant, indicating that these are the major determinants shaping latex yields at the prefecture level. However, the signs and magnitudes of the parameter estimates at the aggregate level are different from those at the lower spatial level, and the differences are due to diverse reasons. The ISODATA classifies the landscape into three categories: high, medium, and low potential yields. The map reveals that Mengla County has the majority of land with high potential yield, while Jinghong City and Menghai County show lower potential yield. In short, the mixed method can offer a means of providing greater insights in the prediction of agricultural production. Full article
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Open AccessArticle Introducing a Non-Stationary Matrix Model for Stand-Level Optimization, an Even-Aged Pine (Pinus Sylvestris L.) Stand in Finland
Forests 2017, 8(5), 163; doi:10.3390/f8050163
Received: 10 April 2017 / Revised: 5 May 2017 / Accepted: 9 May 2017 / Published: 11 May 2017
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Abstract
In general, matrix models are commonly applied to predict tree growth for size-structured tree populations, whereas empirical–statistical models are designed to predict tree growth based on a vast amount of field observations. From the theoretical point of view, matrix models can be considered
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In general, matrix models are commonly applied to predict tree growth for size-structured tree populations, whereas empirical–statistical models are designed to predict tree growth based on a vast amount of field observations. From the theoretical point of view, matrix models can be considered to be more generic since their dependency on ad hoc growth conditions is far less prevalent than that of empirical–statistical models. On the other hand, the main pitfall of matrix models is their inability to include variation among the individuals within a size class, occasionally resulting in less accurate predictions of tree growth compared to empirical–statistical models. Thus, the relevant question is whether a matrix model can capture essential tree-growth dynamics/characteristics so that the model produces accurate stand projections which can further be applied in practical decision-making. Such a dynamic characteristic in our model is the basal area of trees, which causes nonlinearity in time. Therefore, our matrix model is a nonlinear model. The empirical data for models was based on 20 sample plots representing 8360 tree records. Further, according to the model, stand projections were produced for three Scots pine (Pinus sylvestris L.) sapling stands (age of 25 years, stand density fluctuating from 850 to 1400 stems ha - 1 ). Then, (even-aged) stand management was optimized by applying sequential quadratic programming (SQP) among those growth predictions. The objective function of the optimization task was to maximize the net present value (NPV) of the ongoing rotation. The stands were located in Northern Ostrobothnia, Finland, on nutrient-poor soil type. The results indicated that initial stand density had an effect on optimal solutions—optimal stand management varied with respect to thinnings (timing and intensity) as well as to optimal rotation. Further, an increasing discount rate shortened considerably the optimal rotation period, and relaxing the minimum thinning removal to 30 m 3 ha - 1 resulted in an increase both in number of thinnings and in the maximum net present value. Full article
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Open AccessArticle Influence of Cutting Type and Fertilization in Production of Containerized Poplar Plants
Forests 2017, 8(5), 164; doi:10.3390/f8050164
Received: 1 March 2017 / Revised: 25 April 2017 / Accepted: 8 May 2017 / Published: 11 May 2017
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Abstract
Most poplar plantations are planted on marginal agricultural land, but poplar plantations also hold the potential for increased profits compared to plantations of other species on non-agricultural, previously forested land. To date, the establishment of poplar plantations on previously forested land is limited
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Most poplar plantations are planted on marginal agricultural land, but poplar plantations also hold the potential for increased profits compared to plantations of other species on non-agricultural, previously forested land. To date, the establishment of poplar plantations on previously forested land is limited by the production of suitable containerized poplar stock for planting. The objective of this study is to investigate how different cutting quality and fertilizer treatments influence height, diameter, and root biomass growth and root-to-shoot ratio, all important variables for plant establishment. Our results show that fertilization increases plant growth and that single-bud and two-bud cuttings with cutting diameters of 5 to 10 mm can be used in the production of containerized plants. Root biomass was similar between these plant types but the number of roots per plant was higher if two-bud cuttings were used. In contrast to fertilized plants, only one cutting type (two-bud 10 mm) grew to a sufficient height and diameter for use in poplar plantation establishment. Interestingly, the root-to-shoot ratio for this cutting type was 0.16 while the ratio for the same cutting type is 0.11 if fertilized. Together, these results suggest that most types of poplar cuttings can be used to establish poplar plantations if fertilizer is used and that the largest cutting type (two-bud 10 mm) might be more suitable to establish poplar plantations at harsh sites, thus reducing the cost of poplar plant production. Full article
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Open AccessArticle An Evaluation of Stakeholder Perception Differences in Forest Road Assessment Factors Using the Analytic Hierarchy Process (AHP)
Forests 2017, 8(5), 165; doi:10.3390/f8050165
Received: 7 March 2017 / Revised: 7 May 2017 / Accepted: 9 May 2017 / Published: 11 May 2017
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Abstract
Many factors, with differing priority ratios, need to be assessed in the evaluation of forest roads. Stakeholder perceptions differ in the road assessment process and this research addresses those differences between academic and practitioner groups. The focus was on four main forest road
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Many factors, with differing priority ratios, need to be assessed in the evaluation of forest roads. Stakeholder perceptions differ in the road assessment process and this research addresses those differences between academic and practitioner groups. The focus was on four main forest road assessment factor groups (technical, economic, environmental, and social) within 23 sub-factors to determine the priority ratios using the Analytic Hierarchy Process (AHP) method. Stakeholder groups expressed different priority ratios, indicating varying perceptions of the importance of these factors: forest engineering academic staff identified technical specifications as the most important issue (with a ratio of 39.77%), while environmental issues were most important for forestry department academic staff, mechanical supply technical staff, and forest enterprise chiefs (with ratios of 41.79%, 39.95%, and 37.03%, respectively). Due to differences in stakeholder group perceptions, a participatory forest road assessment approach should be adopted. Full article
Open AccessArticle Patch-Based Forest Change Detection from Landsat Time Series
Forests 2017, 8(5), 166; doi:10.3390/f8050166
Received: 20 February 2017 / Revised: 28 April 2017 / Accepted: 5 May 2017 / Published: 11 May 2017
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Abstract
In the species-rich and structurally complex forests of the Eastern United States, disturbance events are often partial and therefore difficult to detect using remote sensing methods. Here we present a set of new algorithms, collectively called Vegetation Regeneration and Disturbance Estimates through Time
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In the species-rich and structurally complex forests of the Eastern United States, disturbance events are often partial and therefore difficult to detect using remote sensing methods. Here we present a set of new algorithms, collectively called Vegetation Regeneration and Disturbance Estimates through Time (VeRDET), which employ a novel patch-based approach to detect periods of vegetation disturbance, stability, and growth from the historical Landsat image records. VeRDET generates a yearly clear-sky composite from satellite imagery, calculates a spectral vegetation index for each pixel in that composite, spatially segments the vegetation index image into patches, temporally divides the time series into differently sloped segments, and then labels those segments as disturbed, stable, or regenerating. Segmentation at both the spatial and temporal steps are performed using total variation regularization, an algorithm originally designed for signal denoising. This study explores VeRDET’s effectiveness in detecting forest change using four vegetation indices and two parameters controlling the spatial and temporal scales of segmentation within a calibration region. We then evaluate algorithm effectiveness within a 386,000 km2 area in the Eastern United States where VeRDET has overall error of 23% and omission error across disturbances ranging from 22% to 78% depending on agent. Full article
(This article belongs to the Special Issue Remote Sensing of Forest Disturbance)
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Open AccessArticle Thinning of Beech Forests Stocking on Shallow Calcareous Soil Maintains Soil C and N Stocks in the Long Run
Forests 2017, 8(5), 167; doi:10.3390/f8050167
Received: 1 February 2017 / Revised: 7 May 2017 / Accepted: 8 May 2017 / Published: 11 May 2017
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Abstract
Sustainable forest management should avoid disturbance and volatilization of the soil carbon (C) and nitrogen (N) stocks both under present and projected future climate. Earlier studies have shown that thinning of European beech forests induces a strong initial perturbation of the soil C
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Sustainable forest management should avoid disturbance and volatilization of the soil carbon (C) and nitrogen (N) stocks both under present and projected future climate. Earlier studies have shown that thinning of European beech forests induces a strong initial perturbation of the soil C and N cycles in shallow Rendzic Leptosol, which consists of lower soil N retention and strongly enhanced gaseous losses observed over several years. Persistence of these effects could decrease soil organic matter (SOM) levels and associated soil functions such as erosion protection, nutrient retention, and fertility. Therefore, we resampled untreated control and thinned stands a decade after thinning at sites representing both typical present day and projected future climatic conditions for European beech forests. We determined soil organic C and total N stocks, as well as δ13C and δ15N as integrators of changes in soil C and N cycles. Thinning did not alter these parameters at any of the sampled sites, indicating that initial effects on soil C and N cycles constitute short-term perturbations. Consequently, thinning may be considered a sustainable beech forest management strategy with regard to the maintenance of soil organic C and total N stocks both under present and future climate. Full article
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Open AccessArticle Drones as a Tool for Monoculture Plantation Assessment in the Steepland Tropics
Forests 2017, 8(5), 168; doi:10.3390/f8050168
Received: 31 March 2017 / Revised: 2 May 2017 / Accepted: 6 May 2017 / Published: 12 May 2017
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Abstract
Smallholder tree plantations are expanding in the steepland tropics due to demand for timber and interest in ecosystem services, such as carbon storage. Financial mechanisms are developing to compensate vegetation carbon stores. However, measuring biomass—necessary for accessing carbon funds—at small scales is costly
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Smallholder tree plantations are expanding in the steepland tropics due to demand for timber and interest in ecosystem services, such as carbon storage. Financial mechanisms are developing to compensate vegetation carbon stores. However, measuring biomass—necessary for accessing carbon funds—at small scales is costly and time-intensive. Therefore, we test whether low-cost drones can accurately estimate height and biomass in monoculture plantations in the tropics. We used Ecosynth, a drone-based structure from motion technique, to build 3D vegetation models from drone photographs. These data were filtered to create a digital terrain model (DTM) and digital surface model (DSM). Two different canopy height models (CHMs) from the Ecosynth DSM were obtained by subtracting terrain elevations from the Ecosynth DTM and a LIDAR DTM. We compared height and biomass derived from these CHMs to field data. Both CHMs accurately predicted the height of all species combined; however, the CHM from the LiDAR DTM predicted heights and biomass on a per-species basis more accurately. Height and biomass estimates were strong for evergreen single-stemmed trees, and unreliable for small leaf-off species during the dry season. This study demonstrates that drones can estimate plantation biomass for select species when used with an accurate DTM. Full article
(This article belongs to the Special Issue Optimizing Forest Inventories with Remote Sensing Techniques)
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Open AccessArticle Reducing Reforestation Costs in Lebanon: Adaptive Field Trials
Forests 2017, 8(5), 169; doi:10.3390/f8050169
Received: 3 February 2017 / Revised: 20 April 2017 / Accepted: 6 May 2017 / Published: 17 May 2017
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Abstract
Lebanon’s Ministry of Environment initiated a project in 2009 to determine low-cost reforestation techniques for stone pine (Pinus pinea) and Lebanon cedar (Cedrus libani) for large-scale land rehabilitation activities in the arid Middle East. Irrigation (several techniques vs. no
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Lebanon’s Ministry of Environment initiated a project in 2009 to determine low-cost reforestation techniques for stone pine (Pinus pinea) and Lebanon cedar (Cedrus libani) for large-scale land rehabilitation activities in the arid Middle East. Irrigation (several techniques vs. no water), planting (8- to 18-month-old seedlings), seeding, and soil preparation methods were evaluated in three sets of adaptive management field trials. The aim was to reduce reforestation costs while still achieving sufficient regeneration. A key result for management was that non-irrigated seed planting of stone pine and possibly of Lebanon cedar showed promise for cost-effective reforestation and could be competitive with seedlings, given correct seed source and planting conditions. Stone pine seeds collected from nearby mother trees and planted without irrigation on sandy soil showed 35% survival for <600 USD/ha; seedlings planted without irrigation cost about 2500 USD/ha and achieved 50–70% survival (costs based on 800 seedlings/ha). Water supplements increased establishment costs over 2 years without concomitant improvements to survival. Future studies should evaluate how soil texture and soil preparation interact with other factors to affect seed germination and survival for each species. Full article
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Open AccessArticle Comparing Empirical and Semi-Empirical Approaches to Forest Biomass Modelling in Different Biomes Using Airborne Laser Scanner Data
Forests 2017, 8(5), 170; doi:10.3390/f8050170
Received: 10 March 2017 / Revised: 7 May 2017 / Accepted: 12 May 2017 / Published: 16 May 2017
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Abstract
Airborne laser scanner (ALS) data are used operationally to support field inventories and enhance the accuracy of forest biomass estimates. Modelling the relationship between ALS and field data is a fundamental step of such applications and the quality of the model is essential
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Airborne laser scanner (ALS) data are used operationally to support field inventories and enhance the accuracy of forest biomass estimates. Modelling the relationship between ALS and field data is a fundamental step of such applications and the quality of the model is essential for the final accuracy of the estimates. Different modelling approaches and variable transformations have been advocated in the existing literature, but comparisons are few or non-existent. In the present study, two main approaches to modelling were compared: the empirical and semi-empirical approaches. Evaluation of model performance was conducted using a conventional evaluation criterion, i.e., the mean square deviation (MSD). In addition, a novel evaluation criterion, the model error (ME), was proposed. The ME was constructed by combining a MSD expression and a model-based variance estimate. For the empirical approach, multiple regression models were developed with two alternative transformation strategies: square root transformation of the response, and natural logarithmic transformation of both response and predictors. For the semi-empirical approach, a nonlinear regression of a power model form was chosen. Two alternative predictor variables, mean canopy height and top canopy height, were used separately. Results showed that the semi-empirical approach resulted in the smallest MSD in three of five study sites. The empirical approach resulted in smaller ME in the temperate and boreal biomes, while the semi-empirical approach resulted in smaller ME in the tropical biomes. Full article
(This article belongs to the Special Issue Optimizing Forest Inventories with Remote Sensing Techniques)
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Open AccessArticle Performance of a Mobile Star Screen to Improve Woodchip Quality of Forest Residues
Forests 2017, 8(5), 171; doi:10.3390/f8050171
Received: 4 April 2017 / Revised: 2 May 2017 / Accepted: 13 May 2017 / Published: 17 May 2017
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Abstract
Low harvesting costs and increasing demand for forest-derived biomass led to an increased use of full-tree (FT) harvesting in steep terrain areas in Austria. Logging residues, as a by-product of FT harvesting, present an easily accessible bioenergy resource, but high portions of fine
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Low harvesting costs and increasing demand for forest-derived biomass led to an increased use of full-tree (FT) harvesting in steep terrain areas in Austria. Logging residues, as a by-product of FT harvesting, present an easily accessible bioenergy resource, but high portions of fine particles and contaminants like earth particles and stones make them a complex and difficult fuel, as they affect storage capability, conversion efficiency, or emission rates adversely. The present research focuses on the productivity and performance of a star screen, which was used to remove fine and oversize particles from previously chipped, fresh Norway spruce (Picea abies (L.) Karst.) logging residue woodchips. Three screen settings, which differed in terms of different rotation speeds of the fine star elements (1861 rpm, 2239 rpm, 2624 rpm) were analyzed. Time studies of the star screen were carried out to estimate screening productivity and costs. Furthermore, 115 samples were collected from all material streams, which were assessed for particle size distribution, calorific value, ash content, and component and elemental composition. Average productivity was 20.6 tonnes (t) per productive system hour (PSH15), corresponding to screening costs of 9.02 €/t. The results indicated that the screening of chipped logging residues with a star screen influenced material characteristics of the medium fraction, as it decreased the ash content, the incidence of fine particles, and the nutrient content. The different screen settings had a noticeable influence on the quality characteristics of the screening products. An increase of the rotation speed of the fine stars reduced screening costs per unit of screened material in the medium fraction, but also lowered screening quality. Full article
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Open AccessArticle Optimizing the Wood Value Chain in Northern Norway Taking Into Account National and Regional Economic Trade-Offs
Forests 2017, 8(5), 172; doi:10.3390/f8050172
Received: 10 March 2017 / Revised: 27 April 2017 / Accepted: 9 May 2017 / Published: 17 May 2017
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Abstract
As a consequence of past decades of extensive afforestation in Norway, mature forest volumes are increasing. National forestry politics call for sustainable and efficient resource usage and for increased regional processing. Regional policies seek to provide good conditions for such industries to be
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As a consequence of past decades of extensive afforestation in Norway, mature forest volumes are increasing. National forestry politics call for sustainable and efficient resource usage and for increased regional processing. Regional policies seek to provide good conditions for such industries to be competitive and to improve regional value creation. We demonstrate how methods from operations research and regional macro-economics may complement each other to support decision makers in this process. The operations research perspective is concerned with finding an optimally designed wood value chain and an aggregated planning of its operations, taking a holistic perspective on strategic-tactical level. Using Input-Output analysis methods based on statistics and survey data, regional macro-economics helps to estimate each industry actor’s value creation and impact on society beyond immediate value chain activities. Combining these approaches in a common mathematical optimization model, a balance can be struck between industry/business and regional political interests. For a realistic case study from the northern part of coastal Norway, we explore this balance from several perspectives, investigating value chain profits, economic ripple effects and regional resource usage. Full article
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Open AccessArticle Earlywood and Latewood Widths of Picea chihuahuana Show Contrasting Sensitivity to Seasonal Climate
Forests 2017, 8(5), 173; doi:10.3390/f8050173
Received: 28 March 2017 / Revised: 15 May 2017 / Accepted: 16 May 2017 / Published: 18 May 2017
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Abstract
The existence of endangered tree species in Mexico necessitates an understanding of their vulnerability to the predicted climate changes (warming and drying trends). In this study, the sensitivity to climate of earlywood (EW) and latewood (LW) widths of the
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The existence of endangered tree species in Mexico necessitates an understanding of their vulnerability to the predicted climate changes (warming and drying trends). In this study, the sensitivity to climate of earlywood (EW) and latewood (LW) widths of the threatened Picea chihuahuana was determined. The response of EW and LW to climate variables (maximum temperature, minimum temperature, precipitation, evaporation, and a drought index) was analyzed by means of correlation analysis using dendrochronology over the period of 1950–2015. EW and LW production were enhanced by cool and wet conditions during winter prior to the start of growing season. During the growing season, EW and LW production increased in response to cool spring and summer conditions, respectively; temperatures and year-round evaporation, excluding summer and the previous drought in the period prior to the growing season. EW was sensitive to seasonal drought, which is a concern considering the predicted aridification trends for the study area. These results provide further knowledge on the dendroecological potential of Picea chihuahuana. Full article
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Open AccessArticle Drought Influence over Radial Growth of Mexican Conifers Inhabiting Mesic and Xeric Sites
Forests 2017, 8(5), 175; doi:10.3390/f8050175
Received: 23 April 2017 / Revised: 11 May 2017 / Accepted: 16 May 2017 / Published: 19 May 2017
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Abstract
Drought is a major constraint of forest productivity and tree growth across diverse habitat types. In this study, we investigated the drought responses of four conifer species growing within two locations of differing elevation and climatic conditions in northern Mexico. Two species were
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Drought is a major constraint of forest productivity and tree growth across diverse habitat types. In this study, we investigated the drought responses of four conifer species growing within two locations of differing elevation and climatic conditions in northern Mexico. Two species were selected at a mesic site (Cupressus lusitanica Mill., Abies durangensis Martínez) and the other two species were sampled at a xeric site (Pinus engelmannii Carr., Pinus cembroides Zucc.). Using a dendrochronological approach, we correlated the radial-growth series of each species and the climatic variables. All study species positively responded to wet-cool conditions during winter and spring. Despite the close proximity of species at a mesic site, A. durangensis had high responsiveness to hydroclimatic variability, but C. lusitanica was not responsive. At the xeric site, P. engelmannii and P. cembroides were very responsive to drought severity, differentiated only by the longer time scale of the response to accumulated drought of P. engelmannii. The responsiveness to hydroclimate and drought of these tree species seems to be modulated by site conditions, or by the functional features of each species that are still little explored. These findings indicate that differentiating between mesic and xeric habitats is a too coarse approach in diverse forests with a high topographic heterogeneity. Full article
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Open AccessFeature PaperArticle Branch Wood Decomposition of Tree Species in a Deciduous Temperate Forest in Korea
Forests 2017, 8(5), 176; doi:10.3390/f8050176
Received: 11 April 2017 / Revised: 11 May 2017 / Accepted: 12 May 2017 / Published: 19 May 2017
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Abstract
Woody debris, which is supplied by branch litter, is an important component of forest ecosystems as it contains large quantities of organic matter and nutrients. We evaluated changes in branch wood dry weight and nutrient content of six common species (Fraxinus rhynchophylla
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Woody debris, which is supplied by branch litter, is an important component of forest ecosystems as it contains large quantities of organic matter and nutrients. We evaluated changes in branch wood dry weight and nutrient content of six common species (Fraxinus rhynchophylla, Pinus densiflora, Prunus sargentii, Quercus mongolica, Acer pseudosieboldianum, and Symplocos chinensis for. pilosa) in a deciduous temperate forest in Korea for 40 months. Branch wood disk samples 1.4–1.6 cm thick were cut, and mass loss was measured over time using the litterbag method. No significant differences in mass loss were recorded among the six tree species. Further, mass loss was negatively correlated with initial lignin concentration and positively correlated with both initial cellulose concentration and wood density for each species. Species with high wood cellulose content had high wood density while the lignin content in wood was relatively low. Accordingly, cellulose contributed to wood density, creating a relatively lower lignin content, and the decreased lignin concentration increased the wood decomposition rate. Full article
(This article belongs to the Special Issue Coarse Woody Debris of Forests in a Changing World)
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Review

Jump to: Research, Other

Open AccessReview Regeneration Dynamics of Coast Redwood, a Sprouting Conifer Species: A Review with Implications for Management and Restoration
Forests 2017, 8(5), 144; doi:10.3390/f8050144
Received: 15 March 2017 / Revised: 14 April 2017 / Accepted: 21 April 2017 / Published: 27 April 2017
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Abstract
Coast redwood (Sequoia sempervirens (Lamb. ex. D. Don) Endl.) is unique among conifer species because of its longevity, the great sizes of individual trees, and its propensity to reproduce through sprouts. Timber harvesting in the native redwood range along the coast of
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Coast redwood (Sequoia sempervirens (Lamb. ex. D. Don) Endl.) is unique among conifer species because of its longevity, the great sizes of individual trees, and its propensity to reproduce through sprouts. Timber harvesting in the native redwood range along the coast of the western United States has necessitated restoration aimed to promote old forest structures to increase the total amount of old forest, the connectivity between old forests, and to enhance the resiliency of these ecosystems. After disturbance or harvest, healthy redwood stumps sprout vigorously, often producing dozens of sprouts within two years of disturbance. These sprouts form highly aggregated spatial patterns because they are clustered around stumps that may number less than 50 ha−1. Thinning of sprouts can accelerate individual tree growth, providing an effective restoration strategy to accelerate formation of large trees and old forest structures or increase stand growth for timber production. However, management, including restoration activities, is a contentious issue throughout the native range of redwood because of the history of overexploitation of this resource and perceptions that overexploitation is continuing. This paper reviews the science of early stand dynamics in coast redwood and their implications for restoration and other silvicultural strategies. Full article
(This article belongs to the Special Issue Post-Disturbance Forest Management and Regeneration Dynamics)
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Open AccessFeature PaperReview Tree Diseases as a Cause and Consequence of Interacting Forest Disturbances
Forests 2017, 8(5), 147; doi:10.3390/f8050147
Received: 15 March 2017 / Revised: 27 April 2017 / Accepted: 27 April 2017 / Published: 28 April 2017
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Abstract
The disease triangle is a basic and highly flexible tool used extensively in forest pathology. By linking host, pathogen, and environmental factors, the model provides etiological insights into disease emergence. Landscape ecology, as a field, focuses on spatially heterogeneous environments and is most
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The disease triangle is a basic and highly flexible tool used extensively in forest pathology. By linking host, pathogen, and environmental factors, the model provides etiological insights into disease emergence. Landscape ecology, as a field, focuses on spatially heterogeneous environments and is most often employed to understand the dynamics of relatively large areas such as those including multiple ecosystems (a landscape) or regions (multiple landscapes). Landscape ecology is increasingly focused on the role of co-occurring, overlapping, or interacting disturbances in shaping spatial heterogeneity as well as understanding how disturbance interactions mediate ecological impacts. Forest diseases can result in severe landscape-level mortality which could influence a range of other landscape-level disturbances including fire, wind impacts, and land use among others. However, apart from a few important exceptions, these disturbance-disease interactions are not well studied. We unite aspects of forest pathology with landscape ecology by applying the disease-triangle approach from the perspective of a spatially heterogeneous environment. At the landscape-scale, disturbances such as fire, insect outbreak, wind, and other events can be components of the environmental ‘arm’ of the disease triangle, meaning that a rich base of forest pathology can be leveraged to understand how disturbances are likely to impact diseases. Reciprocal interactions between disease and disturbance are poorly studied but landscape ecology has developed tools that can identify how they affect the dynamics of ecosystems and landscapes. Full article
(This article belongs to the Special Issue Forest Pathology and Plant Health)
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Open AccessReview Impacts of Beech Bark Disease and Climate Change on American Beech
Forests 2017, 8(5), 155; doi:10.3390/f8050155
Received: 14 March 2017 / Revised: 25 April 2017 / Accepted: 28 April 2017 / Published: 3 May 2017
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Abstract
American beech (Fagus grandifolia Ehrh.) is a dominant component of forest tree cover over a large portion of eastern North America and this deciduous, mast-bearing tree species plays a key role in these forest ecosystems. Beech bark disease (BBD) is a scale
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American beech (Fagus grandifolia Ehrh.) is a dominant component of forest tree cover over a large portion of eastern North America and this deciduous, mast-bearing tree species plays a key role in these forest ecosystems. Beech bark disease (BBD) is a scale insect-fungus complex that has caused the decline and death of afflicted beech trees. This disease has become a common feature in North American forest landscapes. Resistance to BBD is at the level of the beech scale (Cryptococcus fagisuga Lind.). Beech scale attack predisposes the tree to subsequent infection by Neonectria fungi. The impact of this tree disease has been shown to be significant, particularly in beech dominated forests. Scale-free trees (resistant to BBD) have been reported to range from only 1% to 3% in infested stands, with estimates ranging from 80–95% for overall infestation (for all beech within the current North American range). In addition to BBD, overall beech health will be directly impacted by climate change, if one specifically considers the expected fluctuations in precipitation leading to both drought periods and flooding. Beech is particularly sensitive to both extremes and is less resilient than other broad leaf tree species. Although the increase in global temperatures will likely shift the current range of the American beech, milder winters and less snowpack will favor propagation and survival of the beech scale. This review aims to present the current outlook for American beech in light of climate change. The natural history of the American beech and the onslaught of BBD during the last century will be covered, followed by the potential effects of a changing climate on BBD-infested forests. Evidence from models of European beech (Fagus sylvatica) and other host-pathogen systems will supplement data directly gathered to evaluate BBD in American beech. We present the case that although climate change is likely to be a confounding factor in the continued loss of American beech, increasing our understanding of possible mechanisms of resistance and environmental factors that may influence susceptibility of American beech to BBD can inform proactive management strategies. Full article
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Open AccessReview An Updated Review of Dendrochronological Investigations in Mexico, a Megadiverse Country with a High Potential for Tree-Ring Sciences
Forests 2017, 8(5), 160; doi:10.3390/f8050160
Received: 2 April 2017 / Revised: 30 April 2017 / Accepted: 5 May 2017 / Published: 9 May 2017
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Abstract
Dendrochronology is a very useful science to reconstruct the long-term responses of trees and other woody plants forming annual rings in response to their environment. The present review considered Mexico, a megadiverse country with a high potential for tree-ring sciences given its high
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Dendrochronology is a very useful science to reconstruct the long-term responses of trees and other woody plants forming annual rings in response to their environment. The present review considered Mexico, a megadiverse country with a high potential for tree-ring sciences given its high climatic and environmental variability. We reviewed papers considering Mexican tree species that were published from 2001 to 2016. Most of these studies examined tree species from temperate forests, mainly in the pine and fir species. The review included 31 tree species. The most intensively sampled family and species were the Pinaceae and Douglas fir (Pseudotsuga menziessi (Mirb.) Franco), respectively. Some threatened tree species were also studied. Dendrochronological investigations were mainly conducted in northern and central Mexico, with Durango being the most sampled state. The reviewed studies were mostly developed for hydroclimatic reconstructions, which were mainly based on the tree-ring width as a proxy for the climate. Tree-ring studies were carried out in both national and foreign institutions. Our review identified relevant research gaps for dendrochronologists such as: (i) biomes which are still scarcely studied (e.g., tropical dry forests) and (ii) approaches still rarely applied to Mexican forests as dendroecology. Full article
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Open AccessFeature PaperReview Novelty and Its Ecological Implications to Dry Forest Functioning and Conservation
Forests 2017, 8(5), 161; doi:10.3390/f8050161
Received: 24 February 2017 / Revised: 12 April 2017 / Accepted: 6 May 2017 / Published: 10 May 2017
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Abstract
Tropical and subtropical dry forest life zones support forests with lower stature and species richness than do tropical and subtropical life zones with greater water availability. The number of naturalized species that can thrive and mix with native species to form novel forests
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Tropical and subtropical dry forest life zones support forests with lower stature and species richness than do tropical and subtropical life zones with greater water availability. The number of naturalized species that can thrive and mix with native species to form novel forests in dry forest conditions in Puerto Rico and the US Virgin Islands is lower than in other insular life zones. These novel dry forests are young (<60 years) with low structural development, high species dominance, and variable species density. Species density is low during initial establishment and increases with age. At the 1-ha scale, novel forests can have greater species density than mature native forests. Species groups, such as nitrogen-fixing species, and other naturalized species that dominate novel dry forests, have a disproportional influence on forest element stoichiometry. Novel dry forests, compared to the mean of all forest species assemblages island-wide, tend to have fallen leaf litter with lower than average manganese and sodium concentrations and lower than average C/N and C/P ratios. After accounting for significant differences in stand age, geology, and or precipitation, novel dry forests compared to native dry forests have higher C anomalies, lower Ca and Na anomalies, and lower C/N ratio anomalies. Taken together, these characteristics may influence litter decomposition rates and the species composition, diversity, and food web dynamics in litter and soil. Novel dry forests also contribute to the conservation of native plant species on highly degraded lands. Full article
(This article belongs to the Special Issue Tropical Forest Ecology and Management for the Anthropocene)
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Open AccessFeature PaperReview Responses of Ground-Dwelling Invertebrates to Gap Formation and Accumulation of Woody Debris from Invasive Species, Wind, and Salvage LoggingRunning Title: Perry and Herms: Responses of Ground-Dwelling Invertebrates
Forests 2017, 8(5), 174; doi:10.3390/f8050174
Received: 12 April 2017 / Revised: 12 May 2017 / Accepted: 13 May 2017 / Published: 18 May 2017
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Abstract
Natural and anthropogenic disturbances alter canopy structure, understory vegetation, amount of woody debris, and the litter and soil layers in forest ecosystems. These environmental changes impact forest communities, including ground-dwelling invertebrates that are key regulators of ecosystem processes. Variation in frequency, intensity, duration,
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Natural and anthropogenic disturbances alter canopy structure, understory vegetation, amount of woody debris, and the litter and soil layers in forest ecosystems. These environmental changes impact forest communities, including ground-dwelling invertebrates that are key regulators of ecosystem processes. Variation in frequency, intensity, duration, and spatial scale of disturbances affect the magnitude of these environmental changes and how forest communities and ecosystems are impacted over time. We propose conceptual models that describe the dynamic temporal effects of disturbance caused by invasive insects, wind, and salvage logging on canopy gap formation and accumulation of coarse woody debris (CWD), and their impacts on ground-dwelling invertebrate communities. In the context of this framework, predictions are generated and their implications for ground-dwelling invertebrate communities are discussed. Full article
(This article belongs to the Special Issue Coarse Woody Debris of Forests in a Changing World)
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Open AccessNew Book Received People, Forests, and Change: Lessons from the Pacific Northwest. Edited by Deanna H. Olson and Beatrice Van Horne, Island Press, 2017; 350 Pages. Price: Hardback $90, ISBN 9781610917667; Paperback $45, ISBN 9781610917674
Forests 2017, 8(5), 149; doi:10.3390/f8050149
Received: 20 April 2017 / Revised: 20 April 2017 / Accepted: 28 April 2017 / Published: 28 April 2017
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