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Volume 11
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Forests, Volume 11, Issue 4 (April 2020) – 120 articles

Cover Story (view full-size image): Forest ecosystems sustainability is a major challenge in a world threatened by climate change and alien invasive pathogens. Forest decline triggered by those factors has been identified around the globe in both natural and artificial forest stands. In Spain, for example, Mediterranean Quercus forests are severely affected by tree mortality caused by Phytophthora cinnamomi root rot, causing the loss of mature and young trees in dehesa ecosystems and afforestation stands. Although this syndrome has been extensively studied, there are still many gaps in the study of plant–pathogen–soil interaction. We analyzed the spatial distribution of soil properties and pathogen inoculum density under trees in one afforestation affected by root rot. Our results showed the significant influence of crown cover, with predictable patterns of inoculum density related to soil properties and crown projection.View this paper.
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29 pages, 5190 KiB  
Article
Western Larch Regeneration Responds More Strongly to Site and Indirect Climate Factors Than to Direct Climate Factors
by James E. Steed and Sara A. Goeking
Forests 2020, 11(4), 482; https://doi.org/10.3390/f11040482 - 24 Apr 2020
Cited by 4 | Viewed by 3301
Abstract
Substantial shifts in the distribution of western larch (Larix occidentalis Nutt.) are predicted during the coming decades in response to changing climatic conditions. However, it is unclear how the interplay between direct climate effects, such as warmer, drier conditions, and indirect climate [...] Read more.
Substantial shifts in the distribution of western larch (Larix occidentalis Nutt.) are predicted during the coming decades in response to changing climatic conditions. However, it is unclear how the interplay between direct climate effects, such as warmer, drier conditions, and indirect climate effects, such as predicted increases in fire disturbance, will impact fire-adapted species such as western larch. The objectives of this study were (1) to compare the relative importance of stand, site, and indirect versus direct climatic factors in determining western larch seedling recruitment; (2) to determine whether seedling recruitment rates have changed in recent years in response to disturbance, post-fire weather, and/or climate; and (3) to determine whether seedlings and mature trees are experiencing niche differentiation based on recent climatic shifts. We addressed these objectives using data collected from 1286 national forest inventory plots in the US states of Idaho and Montana. We used statistical models to determine the relative importance of 35 stand, site, and climatic factors for larch seedling recruitment. Our results suggest that the most important predictors of larch seedling recruitment were indicative of early-seral stand conditions, and were often associated with recent fire disturbance and cutting. Despite indications of climatic niche compression, seedling recruitment rates have increased in recent decades, likely due to increased fire disturbance, and were unrelated to post-fire weather. Compared to sites occupied by mature trees, seedling recruitment was positively associated with cooler, drier climatic conditions, and particularly with cooler summer temperatures, but these climatic factors were generally less important than biotic stand variables such as stand age, basal area, and canopy cover. These results suggest that, for fire-dependent species such as western larch, increased heat and drought stress resulting from climatic change may be offset, at least in the near term, by an increase in early-seral stand conditions resulting from increased fire disturbance, although localized range contraction may occur at warm, dry extremes. Full article
(This article belongs to the Section Forest Ecology and Management)
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15 pages, 1867 KiB  
Article
Land Use and Access in Protected Areas: A Hunter’s View of Flexibility
by Ayonghe Akonwi Nebasifu and Ngoindong Majory Atong
Forests 2020, 11(4), 481; https://doi.org/10.3390/f11040481 - 24 Apr 2020
Cited by 2 | Viewed by 3200
Abstract
Anthropologists sometimes ask what flexible practices mean when used in instances of land use and access among protected area regimes which control the land and the indigenous or local people who claim rights to the land. In the Mount Cameroon National Park (MCNP), [...] Read more.
Anthropologists sometimes ask what flexible practices mean when used in instances of land use and access among protected area regimes which control the land and the indigenous or local people who claim rights to the land. In the Mount Cameroon National Park (MCNP), West Africa, this question comes with urgency because of the historical disputes associated with defining access and user-rights to land within this park. In this case, we present an ethnographic study using a transect walk with a native Bakweri hunter to map and analyze his opinions about land use and access into the park. The findings show that, despite State prohibitions for this park, customary practices still occur for mutual reasons, whereas, in situations of disputes, other practices continue on the land unnoticed. We conclude that this flexibility is indicative of reciprocal negotiations and cultural resilience that preserve not only the biodiversity of the park but also the culturally relevant needs of people. Full article
(This article belongs to the Special Issue Protected Areas in Forest Conservation: Challenges and Opportunities)
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19 pages, 2781 KiB  
Article
Coffee, Farmers, and Trees—Shifting Rights Accelerates Changing Landscapes
by Claude A. Garcia, Jérémy Vendé, Nanaya Konerira, Jenu Kalla, Michelle Nay, Anne Dray, Maëlle Delay, Patrick O. Waeber, Natasha Stoudmann, Arshiya Bose, Christophe Le Page, Yenugula Raghuram, Robert Bagchi, Jaboury Ghazoul, Cheppudira G. Kushalappa and Philippe Vaast
Forests 2020, 11(4), 480; https://doi.org/10.3390/f11040480 - 24 Apr 2020
Cited by 10 | Viewed by 5629
Abstract
Deforestation and biodiversity loss in agroecosystems are generally the result of rational choices, not of a lack of awareness or knowledge. Despite both scientific evidence and traditional knowledge that supports the value of diverse production systems for ecosystem services and resilience, a trend [...] Read more.
Deforestation and biodiversity loss in agroecosystems are generally the result of rational choices, not of a lack of awareness or knowledge. Despite both scientific evidence and traditional knowledge that supports the value of diverse production systems for ecosystem services and resilience, a trend of agroecosystem intensification is apparent across tropical regions. These transitions happen in spite of policies that prohibit such transformations. We present a participatory modelling study run to (1) understand the drivers of landscape transition and (2) explore the livelihood and environmental impacts of tenure changes in the coffee agroforestry systems of Kodagu (India). The components of the system, key actors and resources, and their interactions were defined with stakeholders, following the companion modelling (ComMod) approach. The underlying ecological processes driving the system were validated through expert knowledge and scientific literature. The conceptual model was transformed into a role-playing game and validated by eight workshops with a total of 57 participants. Two scenarios were explored, a No Policy Change as baseline, and a Restitution of Rights where rights to cut the native trees are handed over to farmers. Our results suggest that the landscape transition is likely to continue unabated unless there is a change to the current policy framework. However, the Restitution of Rights risks speeding up the process rather than reversing it, as inter alia, the differential growth rate between exotic and native tree species, kick in. Full article
(This article belongs to the Section Forest Ecology and Management)
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19 pages, 5246 KiB  
Article
Modeling and Monitoring of Wood Moisture Content Using Time-Domain Reflectometry
by Joseph Dahlen, Laurence Schimleck and Erik Schilling
Forests 2020, 11(4), 479; https://doi.org/10.3390/f11040479 - 24 Apr 2020
Cited by 15 | Viewed by 3275
Abstract
Time-domain reflectometry (TDR) can monitor the moisture content (MC) of water saturated logs stored in wet-decks where the MC exceeds the range that can be measured using traditional moisture meters (>50%). For this application to become routine, it is required that TDR monitoring [...] Read more.
Time-domain reflectometry (TDR) can monitor the moisture content (MC) of water saturated logs stored in wet-decks where the MC exceeds the range that can be measured using traditional moisture meters (>50%). For this application to become routine, it is required that TDR monitoring of wet-decks occurs after establishment, and tools are needed that automate data collection and analysis. We developed models that predict wood MC using three-rod epoxy encased TDR probes inserted into the transverse surface of bolts (prior wet-deck studies were installed on the tangential surface). Models were developed for southern pine, sweetgum, yellow poplar, hickory, red oak, and white oak using a Campbell Scientific TDR100. For each species, at least 37 bolts were soaked for a minimum of three months and then air dried with TDR waveforms, and MC was periodically recorded. Calibrations were developed between MC and the TDR signal using nonlinear mixed effects models. Fixed effects ranged from excellent (southern pine R2 = 0.93) to poor (red oak R2 = 0.36, hickory R2 = 0.38). Independent of wood species, random effects all had a R2 greater than 0.80, which indicates that TDR detects changes in MC at the individual sample level. Use of TDR combined with a datalogger was demonstrated in an operational wet-deck that monitored changes in MC over 12 months, and in a laboratory trial where bolts were exposed to successive wet-dry cycles over 400 days. Both applications demonstrated the utility of TDR to monitor changes in wood MC in high MC environments where periodic measurement is not feasible due to operational safety concerns. Because a saturated TDR reading indicates a saturated MC, and because of the relatively accurate random effects found here, developing individual species models is not necessary for monitoring purposes. Therefore, application of TDR monitoring can be broadly applied for wet-decks, regardless of the species stored. Full article
(This article belongs to the Section Wood Science and Forest Products)
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12 pages, 2592 KiB  
Article
Impact of Steaming Mode on Chemical Characteristics and Colour of Birch Wood
by Anton Geffert, Jarmila Geffertová, Eva Výbohová and Michal Dudiak
Forests 2020, 11(4), 478; https://doi.org/10.3390/f11040478 - 23 Apr 2020
Cited by 12 | Viewed by 2293
Abstract
The aim of this work was to evaluate the changes of the chemical components in birch wood (Betula pendula Roth) caused by steaming with saturated steam at three temperatures—105 °C, 125 °C and 135 °C. In the samples of the original wood [...] Read more.
The aim of this work was to evaluate the changes of the chemical components in birch wood (Betula pendula Roth) caused by steaming with saturated steam at three temperatures—105 °C, 125 °C and 135 °C. In the samples of the original wood and wood after steaming, select chemical characteristics were determined, and wood, isolated holocellulose and Seiferts’s cellulose were analysed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The greatest changes in the birch wood characteristics were observed in steaming mode III (135 °C). The differential spectra of the birch wood samples indicated that the hemicelluloses were significantly degraded and that the dehydration reactions were able to proceed. A clear increase in both unconjugated and conjugated carbonyls was seen only in mode III. The findings also confirmed the greater sensitivity of the guaiacyl lignin contained in broadleaves to elevated steaming temperatures, as well as the course of the thermal oxidation reactions and the formation of new carboxyls in mode III. The decrease in the ratio of absorbances H 1732/2900 and H 1243/2900 demonstrated the cleavage of acyl (acetyl and formyl) groups from birch wood hemicelluloses. The qualitative and quantitative changes of the hemicelluloses and extractive substances in birch wood during steaming were well-correlated with the measured pH values and wood colour. Full article
(This article belongs to the Section Wood Science and Forest Products)
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19 pages, 6386 KiB  
Article
Spatial Habitat Suitability Models of Mangroves with Kandelia obovata
by Shang-Shu Shih
Forests 2020, 11(4), 477; https://doi.org/10.3390/f11040477 - 23 Apr 2020
Cited by 18 | Viewed by 4000
Abstract
Mangrove forests provide important estuarine ecosystem services but are threatened by rising sea levels and anthropogenic impacts. Understanding the habitat characteristics required for mangrove growth is significant for mangrove restoration and integrated management. This study aims to build spatial habitat suitability index (HSI) [...] Read more.
Mangrove forests provide important estuarine ecosystem services but are threatened by rising sea levels and anthropogenic impacts. Understanding the habitat characteristics required for mangrove growth is significant for mangrove restoration and integrated management. This study aims to build spatial habitat suitability index (HSI) models for Kandelia obovata mangrove trees. Biological and habitat-related environmental data were collected in the Wazwei and Guandu wetlands in northern Taiwan. We adopted inundation frequency, soil sorting coefficient, and water salinity as the key environmental factors to build HSI models. The dependent variable of these environmental factors was the mangrove biomass per unit area. Significant differences were found for the mangrove biomass on different substrata and shore elevations. The tidal creek had the lowest elevation, and mangrove areas were found at the highest elevations. The oxidization level of the substrate under mangrove forests was high, indicating that the root system of mangroves could carry oxygen into the soil and result in oxidation. Human activities were found to lead to the reduced growth conditions of mangroves. The validation of the HSI model, considering the inundation frequency and soil sorting coefficient, proved to be reliable, with an accuracy ranging from 78% to 90%. A better simulation was found after revising the model by incorporating the factor of water salinity. The model forecast of the mangrove responses to the sea-level rise indicated an increase in the inundation frequency and thus an induced shift and shrinkage of the mangrove area. The increased HSI values of the bare mudflat area demonstrate an option for the potential restoration of mangrove trees. Given the findings of this study, we concluded that mangroves could spread from estuaries to upstream areas due to rising sea levels and might be limited by humanmade impacts. Restoring degraded floodplains is suggested for mangrove habitat rehabilitation. Full article
(This article belongs to the Special Issue Climate Change Impacts on the Ecosystem Functions and Services of Mangrove Forests)
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18 pages, 2888 KiB  
Article
Selection and Validation of Reference Genes for the qRT-PCR Assays of Populus ussuriensis Gene Expression under Abiotic Stresses and Related ABA Treatment
by Ming Wei, Yingxi Chen, Mengqiu Zhang, Jingli Yang, Han Lu, Xin Zhang and Chenghao Li
Forests 2020, 11(4), 476; https://doi.org/10.3390/f11040476 - 23 Apr 2020
Cited by 12 | Viewed by 2929
Abstract
Populus ussuriensis Kom. is one of the most important tree species for forest renewal in the eastern mountainous areas of Northeast China due to its fast growth, high yield, and significant commercial and ecological value. The selection of optimal reference genes for the [...] Read more.
Populus ussuriensis Kom. is one of the most important tree species for forest renewal in the eastern mountainous areas of Northeast China due to its fast growth, high yield, and significant commercial and ecological value. The selection of optimal reference genes for the normalization of qRT-PCR data is essential for the analysis of relative gene expression. In this study, fourteen genes were selected and assessed for their expression stability during abiotic stress (drought, high salinity, and cold stress) and after the treatment with the drought-related hormone ABA. Three algorithms were used, geNorm, NormFinder, and BestKeeper, and a comprehensive ranking of candidate reference genes was produced based on their output. The most appropriate reference genes were UBQ10 and RPL24 for drought and ABA treatment, UBQ10 and TUB3 for cold stress, and UBQ10 and 60S rRNA for high salinity. Overall, UBQ10 was the most stable reference gene for use as an internal control, whereas PP2A was the least stable. The expression of two target genes (P5CS2 and GI) was used to further verify that the selected reference genes were suitable for gene expression normalization. This work comprehensively assesses the stability of reference genes in Populus ussuriensis and identifies suitable reference genes for normalization during qRT-PCR analysis. Full article
(This article belongs to the Special Issue Forest Genetics and Tree Improvement)
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11 pages, 1329 KiB  
Article
A Local Initiative to Achieve Global Forest and Landscape Restoration Challenge—Lessons Learned from a Community-Based Forest Restoration Project in Biliran Province, Philippines
by Nestor Gregorio, John Herbohn, Rogelio Tripoli and Arturo Pasa
Forests 2020, 11(4), 475; https://doi.org/10.3390/f11040475 - 23 Apr 2020
Cited by 21 | Viewed by 8168
Abstract
Forest and landscape restoration in the tropics is often undertaken by groups of smallholders and communities whose livelihoods are primarily agricultural and forest-based. In the Philippines, the implementation of forest restoration programs involving people’s organizations showed mixed results. We present a case study [...] Read more.
Forest and landscape restoration in the tropics is often undertaken by groups of smallholders and communities whose livelihoods are primarily agricultural and forest-based. In the Philippines, the implementation of forest restoration programs involving people’s organizations showed mixed results. We present a case study of a pilot community-based forest restoration project that was undertaken in Biliran Province to understand the impediments, and pilot test interventions to improve restoration outcomes. The project was designed using systems thinking, employing smallholder-based best-practice, and applying the principles of a participatory approach. The results revealed that the initial participation of smallholders is mostly driven by short-term financial incentives. However, long-term commitment to managing the trees is attributed mainly to sustainable livelihood, land and tree rights, equitable sharing of benefits, strong leadership, effective governance and improved human and social capitals. The support of extension officers, use of high-quality seedlings, and participation of women are essential for community-based forest restoration success. Key lessons from our research could contribute to fulfilling the forest and landscape restoration commitments of developing countries in the tropics. Full article
(This article belongs to the Special Issue Forest and Landscape Restoration—Making it Happen)
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10 pages, 2538 KiB  
Article
Assessing Seed Handling Processes to Facilitate a Community-Engaged Approach to Regional Forest Restoration
by Meredith Cobb, Michaela J. Woods and Ryan W. McEwan
Forests 2020, 11(4), 474; https://doi.org/10.3390/f11040474 - 23 Apr 2020
Cited by 3 | Viewed by 2362
Abstract
In the Midwestern United States, there is a strong management impetus toward reforestation to replace trees lost to due to tree mortality and to establish forests on previously cleared properties. Here, we describe a public outreach and volunteer effort that aimed to generate [...] Read more.
In the Midwestern United States, there is a strong management impetus toward reforestation to replace trees lost to due to tree mortality and to establish forests on previously cleared properties. Here, we describe a public outreach and volunteer effort that aimed to generate positive, community-engaged restoration outcomes and report on a practical experiment involving seed handling. We obtained tree seeds that were donated by members of the community to local land managers. We evaluated the size of the seeds collected and tested the influence of common stratification media (none, sand and vermiculite) and seed size on germination success of three tree genera involved in restoration efforts: Quercus, Carya and Juglans (oak, hickory and walnut). We found a species-specific effect of media on germination, such that Carya and Quercus showed little response to their stratification media, but Juglans had higher germination rates when stratified with vermiculite. Further, all genera of seeds germinated faster when stratified with either media than without. Thus, we suggest stratifying these seeds with media to promote germination success. We also tested for seed size as a predictor of mortality during stratification, following the logic that a size-based selection criterion might save time and space during stratification. We found species-specific impacts of seed size on germination, but relationships were highly variable, and we suggest avoiding screening seeds based on their size. In addition to these scientific results, we describe the broader forest restoration project, which may be a useful model for engaging the community in restoration efforts. Full article
(This article belongs to the Section Forest Ecology and Management)
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17 pages, 5649 KiB  
Article
Soil Erosion Reduction by Grain for Green Project in Desertification Areas of Northern China
by Wenjun Wei, Bing Wang and Xiang Niu
Forests 2020, 11(4), 473; https://doi.org/10.3390/f11040473 - 22 Apr 2020
Cited by 21 | Viewed by 3325
Abstract
The Grain for Green Project (GGP) encompasses most desertification areas in northern China where fragile soils are susceptible to erosion given the arid and semi-arid climate, low vegetation cover, and strong winds. We collected relevant data through ecological surveys and literature review to [...] Read more.
The Grain for Green Project (GGP) encompasses most desertification areas in northern China where fragile soils are susceptible to erosion given the arid and semi-arid climate, low vegetation cover, and strong winds. We collected relevant data through ecological surveys and literature review to quantify total sand fixation and dust retention in 2015 based on different restoration methods, forest types, ecological function zones, and key desertification areas. Our results showed that cropland and wasteland afforestation increased sand fixation and dust retention, whereas facilitate afforestation was less effective in doing so. Further, sand fixation and dust retention values were higher in ecological and shrub forests compared with economic forests, as well as in wind erosion zones compared with wind-water erosion and water erosion zones. Moreover, 43.28% and 44.75% of total sand fixation and dust retention, respectively, were concentrated in important windbreak and sand fixation areas. Similarly, 60% and 30% of total sand fixation and dust retention, respectively, occurred in sandstorm paths and sources. Lastly, policy factors primarily influenced the spatial distribution patterns of both sand fixation and dust retention. Based on these results, enhancement of GGP efficacy into the future will rely on increased restoration efforts specifically aimed at planting more drought-resistant shrubs and native vegetation as doing so will enhance sand fixation, dust retention, and thus, the ecological integrity of these valuable and fragile desert ecosystems in northern China. Full article
(This article belongs to the Section Forest Ecology and Management)
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23 pages, 2600 KiB  
Article
Embedded Deforestation: The Case Study of the Brazilian–Italian Bovine Leather Trade
by Aynur Mammadova, Mauro Masiero and Davide Pettenella
Forests 2020, 11(4), 472; https://doi.org/10.3390/f11040472 - 22 Apr 2020
Cited by 11 | Viewed by 7365
Abstract
Deforestation and forest degradation driven by Agriculture, Forestry and Other Land Use (AFOLU) are important sources of carbon emissions. Market globalization and trade liberalization policies reinforce this trend and risk deforestation to be embedded in global value chains. Due to the complexity of [...] Read more.
Deforestation and forest degradation driven by Agriculture, Forestry and Other Land Use (AFOLU) are important sources of carbon emissions. Market globalization and trade liberalization policies reinforce this trend and risk deforestation to be embedded in global value chains. Due to the complexity of global production and trade systems, deforestation risk is also embedded in the supply chains of the products and sectors that are not direct deforestation drivers. Bovine leather is a commodity closely entangled in the debates about deforestation as it is a by-product of cattle. This research focuses on leather trade between Brazil and Italy to demonstrate the channels through which Italian imports of Brazilian leather could possess embedded Amazonian deforestation and related risks. The data employed for the analysis was searched at three different levels for the leather trade between Brazil and Italy: (a) the country level annual leather trade statistics for the years 2014–2018 taken from the Comtrade database; (b) the state level leather trade data, for the years 2014–2018 taken from the Comexstat database; and (c) the exporter–importer level leather trade data for the period of August 2017–August 2018, based on customs declarations. The analysis helps to demonstrate that the Italian leather trade with Brazil possesses the risk of deforestation unless the proper traceability and due diligence systems are in place to claim the opposite. The European and Italian leather industry need to be more proactive in acknowledging the existence of the risk at different levels, putting full traceability systems in place and sending out clear market signals that deforestation is not tolerated, and that sustainability is valued. Full article
(This article belongs to the Section Forest Economics, Policy, and Social Science)
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12 pages, 2121 KiB  
Article
The Accessibility of Post-Fire Areas for Mechanized Thinning Operations
by Dariusz Kulak, Janusz M. Sowa, Grzegorz Szewczyk and Arkadiusz Stańczykiewicz
Forests 2020, 11(4), 471; https://doi.org/10.3390/f11040471 - 22 Apr 2020
Cited by 3 | Viewed by 2292
Abstract
In 1992, in Southern Poland, large areas of Silesian forests were affected by the country’s largest forest fire. Stands introduced in the 9000-ha post-fire region are currently undergoing early thinning. Due to the scope of these treatments, the chance for their timely implementation [...] Read more.
In 1992, in Southern Poland, large areas of Silesian forests were affected by the country’s largest forest fire. Stands introduced in the 9000-ha post-fire region are currently undergoing early thinning. Due to the scope of these treatments, the chance for their timely implementation is ensured only by the application of cut-to-length (CTL) technologies, i.e., with the use of harvesters and forwarders. The use of CTL technologies may, however, be difficult due to the fire history of these stands, which could affect the bearing capacity of their soils. The objective of this study is to determine the accessibility of stands for forest machines in relation to the bearing capacity of the soils and changes in soil compaction in the post-fire sites. Soil compaction was measured in terms of penetrometer resistance in the stands introduced in the post-fire area in question, as well as in control stands growing on five different soil types. It was shown that in the topsoil layer—from 8 to 18 cm thick depending on the soil type—differences in soil compaction in the post-fire and control areas were relatively small. The impacts of the forest fire—manifested as a significant increase in the compaction of the forest soils—were still visible, but only in the deeper layers of the soil profile. In all of the compared pairs of forest compartments located in the stands regenerated after the fire, significantly higher values of cone indexes (CI) were found. The average value of this index in the post-fire stands was 2.15 MPa, while in the control stands it was 1.60 MPa, which indicates that in both groups of stands the bearing capacity of the soils should not limit the accessibility for vehicles used for timber harvesting and extraction. Full article
(This article belongs to the Special Issue Forest Operations in Environmentally Sensitive Areas)
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16 pages, 2378 KiB  
Article
Methane Emissions from Subtropical and Tropical Mangrove Ecosystems in Taiwan
by Chiao-Wen Lin, Yu-Chen Kao, Meng-Chun Chou, Hsin-Hsun Wu, Chuan-Wen Ho and Hsing-Juh Lin
Forests 2020, 11(4), 470; https://doi.org/10.3390/f11040470 - 21 Apr 2020
Cited by 23 | Viewed by 4798
Abstract
Mangroves are one of the blue carbon ecosystems. However, greenhouse gas emissions from mangrove soils may reduce the capacity of carbon storage in these systems. In this study, methane (CH4) fluxes and soil properties of the top 10 cm layer were [...] Read more.
Mangroves are one of the blue carbon ecosystems. However, greenhouse gas emissions from mangrove soils may reduce the capacity of carbon storage in these systems. In this study, methane (CH4) fluxes and soil properties of the top 10 cm layer were determined in subtropical (Kandelia obovata) and tropical (Avicennia marina) mangrove ecosystems of Taiwan for a complete seasonal cycle. Our results demonstrate that CH4 emissions in mangroves cannot be neglected when constructing the carbon budgets and estimating the carbon storage capacity. CH4 fluxes were significantly higher in summer than in winter in the Avicennia mangroves. However, no seasonal variation in CH4 flux was observed in the Kandelia mangroves. CH4 fluxes were significantly higher in the mangrove soils of Avicennia than in the adjoining mudflats; this trend, however, was not necessarily recapitulated at Kandelia. The results of multiple regression analyses show that soil water and organic matter content were the main factors regulating the CH4 fluxes in the Kandelia mangroves. However, none of the soil parameters assessed show a significant influence on the CH4 fluxes in the Avicennia mangroves. Since pneumatophores can transport CH4 from anaerobic deep soils, this study suggests that the pneumatophores of Avicennia marina played a more important role than soil properties in affecting soil CH4 fluxes. Our results show that different mangrove tree species and related root structures may affect greenhouse gas emissions from the soils. Full article
(This article belongs to the Special Issue Climate Change Impacts on the Ecosystem Functions and Services of Mangrove Forests)
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15 pages, 3443 KiB  
Article
High Genetic Diversity and Low Differentiation in Michelia shiluensis, an Endangered Magnolia Species in South China
by Yanwen Deng, Tingting Liu, Yuqing Xie, Yaqing Wei, Zicai Xie, Youhai Shi and Xiaomei Deng
Forests 2020, 11(4), 469; https://doi.org/10.3390/f11040469 - 21 Apr 2020
Cited by 22 | Viewed by 3609
Abstract
Research Highlights: This study is the first to examine the genetic diversity of Michelia shiluensis (Magnoliaceae). High genetic diversity and low differentiation were detected in this species. Based on these results, we discuss feasible protection measures to provide a basis for the [...] Read more.
Research Highlights: This study is the first to examine the genetic diversity of Michelia shiluensis (Magnoliaceae). High genetic diversity and low differentiation were detected in this species. Based on these results, we discuss feasible protection measures to provide a basis for the conservation and utilization of M. shiluensis. Background and Objectives: Michelia shiluensis is distributed in Hainan and Guangdong province, China. Due to human disturbance, the population has decreased sharply, and there is thus an urgent need to evaluate genetic variation within this species in order to identify an optimal conservation strategy. Materials and Methods: In this study, we used eight nuclear single sequence repeat (nSSR) markers and two chloroplast DNA (cpDNA) markers to assess the genetic diversity, population structure, and dynamics of 78 samples collected from six populations. Results: The results showed that the average observed heterozygosity (Ho), expected heterozygosity (He), and percentage of polymorphic loci (PPL) from nSSR markers in each population of M. shiluensis were 0.686, 0.718, and 97.92%, respectively. For cpDNA markers, the overall haplotype diversity (Hd) was 0.674, and the nucleotide diversity was 0.220. Analysis of markers showed that the genetic variation between populations was much lower based on nSSR than on cpDNA (10.18% and 77.56%, respectively, based on an analysis of molecular variance (AMOVA)). Analysis of the population structure based on the two markers shows that one of the populations (DL) is very different from the other five. Conclusions: High genetic diversity and low population differentiation of M. shiluensis might be the result of rich ancestral genetic variation. The current decline in population may therefore be due to human disturbance rather than to inbreeding or genetic drift. Management and conservation strategies should focus on maintaining the genetic diversity in situ, and on the cultivation of seedlings ex-situ for transplanting back to their original habitat. Full article
(This article belongs to the Special Issue Genetic and Phenotypic Variation in Tree Crops Biodiversity)
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13 pages, 1448 KiB  
Article
Extracellular Soil Enzyme Activities in High-Elevation Mixed Red Spruce Forests in Central Appalachia, U.S.A.
by Philip M. Crim and Jonathan R. Cumming
Forests 2020, 11(4), 468; https://doi.org/10.3390/f11040468 - 21 Apr 2020
Cited by 6 | Viewed by 2913
Abstract
Anthropogenic emissions have impacted terrestrial forest ecosystem processes in North America since the industrial revolution. With the passage of the Clean Air Act in 1970 in the United States, atmospheric inputs of nitrogen (N) and sulfur (S) into forests in the Appalachian Mountains [...] Read more.
Anthropogenic emissions have impacted terrestrial forest ecosystem processes in North America since the industrial revolution. With the passage of the Clean Air Act in 1970 in the United States, atmospheric inputs of nitrogen (N) and sulfur (S) into forests in the Appalachian Mountains have declined, which have, potentially, mitigated their effects on processes such as decomposition and nutrient cycling. Activities of microbial extracellular soil enzymes (ESEs) mediate many rate-limiting nutrient transformations in forest soils and play important roles in the decomposition of complex organic compounds. Soils in high-elevation red spruce forests are characterized by low pH and high carbon (C):N ratios and, having historically received extremely high levels of N deposition, may exhibit legacy impacts of deposition on nutrient availability and decomposition. We utilized four sites along a modeled gradient of N deposition in central Appalachia to assess contemporary ESEs in bulk soil under Acer rubrum L., Betula alleghaniensis Britt., and Picea rubens Sarg. in May, June, and July 2016. Increasing N deposition led to increases in organic fraction C and N and decreases in phosphorus (P). Sites receiving higher N also exhibited greater mineral fraction C, N, and P. ESEs were highest in organic fractions with acid phosphatases (AP) exhibiting the highest activity. There was little influence of N deposition on organic fraction ESEs, but strong evidence for a positive relationship between N deposition and activities of AP, β-glucosidases (BG), and chitinase (NAG) in mineral fractions. Species effects on ESEs were present with high AP in organic fractions under spruce and high mineral fraction fungal laccase (LAC) under birch. The sampling season demonstrated little effect on ESEs. ESEs were more strongly influenced by plot-level factors, such as tree species diversity and abundance of ectomycorrhizal (ECM) tree species, than temporal or soil factors or nutrient status related to modeled cumulative N deposition across these sites. Decreases in AP, BG, and NAG activities with greater abundance of broadleaf deciduous species and increases in activities with ECM host abundance indicate that microbial communities driven by these plant functional groups are responsible for the differences in ESEs observed in these high-elevation mixed red spruce stands. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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18 pages, 2200 KiB  
Article
Eutypella parasitica and Other Frequently Isolated Fungi in Wood of Dead Branches of Young Sycamore Maple (Acer pseudoplatanus) in Slovenia
by Ana Brglez, Barbara Piškur and Nikica Ogris
Forests 2020, 11(4), 467; https://doi.org/10.3390/f11040467 - 20 Apr 2020
Cited by 8 | Viewed by 4913
Abstract
Eutypella parasitica R.W. Davidson and R.C. Lorenz is the causative agent of Eutypella canker of maple, a destructive disease of maples in Europe and North America. The fungus E. parasitica infects the trunk through a branch stub or bark wound. Because the fungal [...] Read more.
Eutypella parasitica R.W. Davidson and R.C. Lorenz is the causative agent of Eutypella canker of maple, a destructive disease of maples in Europe and North America. The fungus E. parasitica infects the trunk through a branch stub or bark wound. Because the fungal community may have an impact on infection and colonization by E. parasitica, the composition of fungi colonizing wood of dead branches of sycamore maple (Acer pseudoplatanus L.) was investigated in five sampling sites in Slovenia. Forty samples from each sampling site were collected between the November 2017 and March 2018 period. Isolations were made from the wood in the outer part of dead branches and from discoloured wood in the trunk that originated from a dead branch. Pure cultures were divided into morphotypes, and one representative culture per morphotype was selected for further molecular identification. From a total of 2700 cultured subsamples, 1744 fungal cultures were obtained, which were grouped into 212 morphotypes. The investigated samples were colonized by a broad spectrum of fungi. The most frequently isolated species were Eutypa maura (Fr.) Sacc., Eutypa sp. Tul. and C. Tul., Fusarium avenaceum (Fr.) Sacc., Neocucurbitaria acerina Wanas., Camporesi, E.B.G. Jones and K.D. Hyde and E. parasitica. In this study, we distinguished species diversity and the fungal community. There were no significant differences in the diversity of fungal species between the five sampling sites, and branch thickness did not prove to be a statistically significant factor in fungal species diversity. Nevertheless, relatively low Jaccard similarity index values suggested possible differences in the fungal communities from different sampling sites. This was confirmed by an analysis of similarities, which showed that the isolated fungal community distinctly differed between the five sampling sites and between the different isolation sources. Eutypella parasitica was isolated from all five investigated sampling sites, although Eutypella cankers were observed in only three sampling sites, indicating the possibility of asymptomatic infection. Full article
(This article belongs to the Special Issue Emerging Pathogens in Forest Ecosystems)
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18 pages, 3522 KiB  
Article
Heat Treatment of Pine Wood: Possible Effect of Impregnation with Silver Nanosuspension
by Hamid R. Taghiyari, Siavash Bayani, Holger Militz and Antonios N. Papadopoulos
Forests 2020, 11(4), 466; https://doi.org/10.3390/f11040466 - 20 Apr 2020
Cited by 26 | Viewed by 4154
Abstract
The scope of the present work was to study the effects of heat treatment (at different mild temperatures) on the physicomechanical properties of pine wood, and to find out if impregnation with nanosilver may have any potential influence on the impact of heat [...] Read more.
The scope of the present work was to study the effects of heat treatment (at different mild temperatures) on the physicomechanical properties of pine wood, and to find out if impregnation with nanosilver may have any potential influence on the impact of heat treatment. Impregnation of wood with a 400-ppm silver nanosuspension was carried out under an initial vacuum pressure of 0.07 MPa, followed by a pressure of 0.25 MPa for thirty minutes, before heat treatment. Heat treatment was carried out under hot air at three relatively mild temperatures, 145, 165, and 185 °C. Results showed improvement of some properties in heat-treated wood at 145 °C. This was indicative of the improving impact caused by hornification and irreversible hydrogen bonding in the course of water movements due to heat treatment; significant fluctuations in the intensities of FTIR spectra bands at 1750–1500 cm−1 were corroborating evidence of chemical alterations in hemicellulose polymer. The high mass loss at temperature 185 °C, and the extreme thermal degradation thereof, overcame the improving effects of hornification and formation of irreversible hydrogen bonds, consequently mechanical properties decreased significantly. Interaction of different elements involved made it hard to predict properties in specimens modified at 165 °C. Impregnation of specimens with nanosilver suspension resulted in significant increase of mass loss in specimens heat-treated at 185 °C, and significant fluctuations in properties of specimens heat-treated at 145 °C. Full article
(This article belongs to the Special Issue Wood Structure and Properties)
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11 pages, 1715 KiB  
Article
The Possibility of Propolis Extract Application in Wood Protection
by Magdalena Woźniak, Patrycja Kwaśniewska-Sip, Agnieszka Waśkiewicz, Grzegorz Cofta and Izabela Ratajczak
Forests 2020, 11(4), 465; https://doi.org/10.3390/f11040465 - 20 Apr 2020
Cited by 25 | Viewed by 4240
Abstract
Nowadays, there is a growing interest in extending the service life of wood and wood products by applying natural substances that are harmless to humans and the environment. In this paper, propolis was used as an eco-friendly wood preservative. The aim of this [...] Read more.
Nowadays, there is a growing interest in extending the service life of wood and wood products by applying natural substances that are harmless to humans and the environment. In this paper, propolis was used as an eco-friendly wood preservative. The aim of this study was to determine the resistance of Scots pine wood treated with the propolis extract against brown-rot fungus Coniophora puteana. The wood biodegradation was assessed by gravimetric method, as well as by the analysis of ergosterol concentration in decayed wood and by the determination of changes in the wood structure by means of Fourier transform infrared spectroscopy. The results indicated that the impregnation of wood with propolis extract above 12% concentration limited fungal decay. The mass loss of wood treated with 18.9% propolis extract was 2.3% and was over 21 times lower than that for untreated wood. The analysis of ergosterol content and the changes in wood structure also confirmed that the propolis extract above 12% concentration protected wood against decay caused by C. puteana. Moreover, the propolis extract used in wood impregnation was rich in phenolic compounds, mainly chrysin, pinocembrin and galangin, which possess antimicrobial activity. The obtained results indicate that the extract of Polish propolis can be a promising natural wood preservative, safe for humans and the natural environment. Full article
(This article belongs to the Section Wood Science and Forest Products)
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18 pages, 2857 KiB  
Article
Biomass Allocation into Woody Parts and Foliage in Young Common Aspen (Populus tremula L.)—Trees and a Stand-Level Study in the Western Carpathians
by Bohdan Konôpka, Jozef Pajtík, Vladimír Šebeň, Peter Surový and Katarína Merganičová
Forests 2020, 11(4), 464; https://doi.org/10.3390/f11040464 - 20 Apr 2020
Cited by 9 | Viewed by 3258
Abstract
Our research of common aspen (Populus tremula L.) focused on the forested mountainous area in central Slovakia. Forest stands (specifically 27 plots from 9 sites) with ages between 2 and 15 years were included in measurements and sampling. Whole tree biomass of [...] Read more.
Our research of common aspen (Populus tremula L.) focused on the forested mountainous area in central Slovakia. Forest stands (specifically 27 plots from 9 sites) with ages between 2 and 15 years were included in measurements and sampling. Whole tree biomass of aspen individuals was destructively sampled, separated into tree components (leaves, branches, stem, and roots), and then dried and weighed. Subsamples of fresh leaves from three crown parts (upper, middle, and lower) were scanned, dried, and weighed. Allometric biomass models with stem base diameter as an independent variable were derived for individual tree components. Basic foliage traits, i.e., leaf mass, leaf area, and specific leaf area, were modelled with regard to tree size and leaf position within the crown. Moreover, biomass stock of the woody parts and foliage as well as the leaf area index were modelled using mean stand diameter as an independent variable. Foliage traits changed with both tree size and crown part. Biomass models showed that foliage contribution to total tree biomass decreased with tree size. The total foliage area of a tree increased with tree size, reaching its maximum value of about 12 m2 for a tree with a diameter of 120 mm. Leaf area index increased with mean stand diameter, reaching a maximum value of 13.5 m2 m−2. Since no data for biomass allocation for common aspen had been available at either the tree or stand levels, our findings might serve for both theoretical (e.g., modelling of growth processes) and practical (forestry and agro-forestry stakeholders) purposes. Full article
(This article belongs to the Special Issue Growth and Allocation of Woody Biomass in Forest Trees Based on Environmental Conditions)
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15 pages, 2129 KiB  
Article
Stem Damage Modifies the Impact of Wind on Norway Spruces
by Guntars Snepsts, Mara Kitenberga, Didzis Elferts, Janis Donis and Aris Jansons
Forests 2020, 11(4), 463; https://doi.org/10.3390/f11040463 - 19 Apr 2020
Cited by 21 | Viewed by 3707
Abstract
Bark stripping caused by cervids can have a long-lasting negative effect on tree vitality. Such trees of low vitality might be more susceptible to other disturbances. The amplifying effects of disturbance interactions can cause significantly more damage to forest ecosystems than the individual [...] Read more.
Bark stripping caused by cervids can have a long-lasting negative effect on tree vitality. Such trees of low vitality might be more susceptible to other disturbances. The amplifying effects of disturbance interactions can cause significantly more damage to forest ecosystems than the individual effects of each disturbance. Therefore, this study aimed to assess the impact of bark stripping (stem damage) on the probability of wind damage and snapping height for Norway spruces (Picea Abies (L.) H. Karst.). In this study, we used the Latvian National Forest Inventory data from the period 2004–2018. In the analysis, we used data based on 32,856 trees. To analyse the data, we implemented a Bayesian binary logistic generalised linear mixed-effects model and the linear mixed-effects model. Our results showed that stem damage significantly increased the probability of wind damage and affected the snapping height of Norway spruces. Similarly, root damage, the slenderness ratio, the stand age, the stand density, the soil type, and the dominant tree species had a significant influence on the probability of wind damage. In both periods, trees with stem damage had significantly (p < 0.05) higher probability (odd ratio 1.68) to be wind damaged than trees without stem damage. The stem damaged Norway spruce trees snapped in the first 25% of the tree height, while trees without stem damage snapped around half (50%) of the tree height. Our results show that stem damage significantly alters the effect of wind damage on Norway spruces, suggesting that such damage must be incorporated into wind-risk assessment models. Full article
(This article belongs to the Special Issue Natural Disturbance Dynamics Analysis for Forest Ecosystem Management)
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10 pages, 1648 KiB  
Article
Comparative Plastome Analyses and Phylogenetic Applications of the Acer Section Platanoidea
by Tao Yu, Jian Gao, Bing-Hong Huang, Buddhi Dayananda, Wen-Bao Ma, Yu-Yang Zhang, Pei-Chun Liao and Jun-Qing Li
Forests 2020, 11(4), 462; https://doi.org/10.3390/f11040462 - 19 Apr 2020
Cited by 10 | Viewed by 3480
Abstract
The Acer L. (Sapindaceae) is one of the most diverse and widespread genera in the Northern Hemisphere. Section Platanoidea harbours high genetic and morphological diversity and shows the phylogenetic conflict between A. catalpifolium and A. amplum. Chloroplast (cp) genome sequencing is efficient [...] Read more.
The Acer L. (Sapindaceae) is one of the most diverse and widespread genera in the Northern Hemisphere. Section Platanoidea harbours high genetic and morphological diversity and shows the phylogenetic conflict between A. catalpifolium and A. amplum. Chloroplast (cp) genome sequencing is efficient for the enhancement of the understanding of phylogenetic relationships and taxonomic revision. Here, we report complete cp genomes of five species of Acer sect. Platanoidea. The length of Acer sect. Platanoidea cp genomes ranged from 156,262 bp to 157,349 bp and detected the structural variation in the inverted repeats (IRs) boundaries. By conducting a sliding window analysis, we found that five relatively high variable regions (trnH-psbA, psbN-trnD, psaA-ycf3, petA-psbJ and ndhA intron) had a high potential for developing effective genetic markers. Moreover, with an addition of eight plastomes collected from GenBank, we displayed a robust phylogenetic tree of the Acer sect. Platanoidea, with high resolutions for nearly all identified nodes, suggests a promising opportunity to resolve infrasectional relationships of the most species-rich section Platanoidea of Acer. Full article
(This article belongs to the Special Issue Genetic and Phenotypic Variation in Tree Crops Biodiversity)
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16 pages, 2823 KiB  
Article
Mixed Broadleaved Tree Species Increases Soil Phosphorus Availability but Decreases the Coniferous Tree Nutrient Concentration in Subtropical China
by Wen-Sheng Bu, Han-Jiao Gu, Can-can Zhang, Yang Zhang, Anand Narain Singh, Xiang-Min Fang, Jing Fan, Hui-Min Wang and Fu-Sheng Chen
Forests 2020, 11(4), 461; https://doi.org/10.3390/f11040461 - 19 Apr 2020
Cited by 19 | Viewed by 3405
Abstract
Phosphorus (P) is a key limiting nutrient in subtropical forests and mixed forests with broadleaved species have been expected to stimulate P cycling, compared to pure conifer plantations. However, the mixture effect of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and broadleaved species [...] Read more.
Phosphorus (P) is a key limiting nutrient in subtropical forests and mixed forests with broadleaved species have been expected to stimulate P cycling, compared to pure conifer plantations. However, the mixture effect of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and broadleaved species on rhizosphere soil and coniferous tree P dynamics is unclear. In our study, eight plots of a single species of a Chinese fir plantation (pure plantation, PP) and eight mixed plantations (mixed plantation, MP) with broadleaved tree species (Michelia macclurei Dandy in Hunan Province or Schima superba Gardn. et Champ. in Fujian Province) were selected in subtropical China. Six P fractions in the rhizosphere and bulk soils were analyzed by a modified Hedley P fractionation method. Phosphorus fractions and nitrogen (N) concentrations in different root orders, different age fresh needles and twigs, and needle and twig litter of Chinese fir were measured. Our results showed that available P, slowly released P, occluded P, and the total extractable P in rhizosphere soil were significantly higher in MP than PP (p < 0.05). In contrast, P and N concentrations in the transportive roots and two-year old needles were generally higher in PP than MP. Meanwhile, the slowly released P, occluded P, total extractable P, and residual P in rhizosphere soil were negatively correlated with P concentrations in young (absorptive and transportive roots, one- and two-year old needles) but not old tissues (storative roots, three-year old needles and litters). In conclusion, mixture may increase soil P availability through the rhizosphere effect, but can decrease P and N concentration of Chinese fir tissues by competition between Chinese fir and broadleaved species. Clearly, the mixture effect may differ in soil and plant nutrients, and this issue needs be taken into consideration when converting a pure conifer plantation into a mixed-species forest. Full article
(This article belongs to the Special Issue Nutrient Cycling in Forest Ecosystems)
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19 pages, 3747 KiB  
Article
Linking Hydromorphological Degradation with Environmental Status of Riparian Ecosystems: A Case Study in the Stropnice River Basin, Czech Republic
by Jiří Jakubínský, Igor Pelíšek and Pavel Cudlín
Forests 2020, 11(4), 460; https://doi.org/10.3390/f11040460 - 18 Apr 2020
Cited by 3 | Viewed by 2945
Abstract
Recently, increasing attention has been paid to the anthropogenic degradation of the riverbed and its relationship to the ecological status of the adjacent river landscape. The key objective of this research was to determine the extent of the disturbance of the selected small [...] Read more.
Recently, increasing attention has been paid to the anthropogenic degradation of the riverbed and its relationship to the ecological status of the adjacent river landscape. The key objective of this research was to determine the extent of the disturbance of the selected small streams and their riparian zone in a study area located in a forest and forest-agricultural landscape in the Czech Republic. The next step was to analyze the mutual relationships between the ecological status of the riparian vegetation and the hydromorphological status of the riverbed. The main working hypothesis considered the good hydromorphological status of the river as reflected in the favorable environmental status of the surrounding riparian habitats and vice versa. It was found in more than 90% of the total length of studied watercourses that the character of linkages between channel morphology and the ecological status of riparian vegetation is directly influenced by anthropogenic activities. An interesting finding is that the degraded streams in lowland sites are often encompassed by natural or close-to-natural habitats. On the contrary, the natural status of the riverbed was found in a significantly forested headwater area, but the riparian habitats did not reach even a close-to-natural status. This paper contributes to clarifying the significance of human impact on the river morphology, reflected in the reduction of connectivity between the terrestrial and fluvial parts of the river landscape. It helps to explore the most important disturbances affecting mutual interactions between the river and the riparian habitats. Full article
(This article belongs to the Special Issue Spatial and Temporal Patterns and Ecosystem Services of Riparian Forests)
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16 pages, 1336 KiB  
Article
Fungi and Oomycetes in the Irrigation Water of Forest Nurseries
by Adas Marčiulynas, Diana Marčiulynienė, Jūratė Lynikienė, Artūras Gedminas, Miglė Vaičiukynė and Audrius Menkis
Forests 2020, 11(4), 459; https://doi.org/10.3390/f11040459 - 18 Apr 2020
Cited by 17 | Viewed by 3873
Abstract
The aim of the present study was to assess fungal and oomycete communities in the irrigation water of forest nurseries, focusing on plant pathogens in the hope of getting a better understanding of potential pathogenic microorganisms and spreading routes in forest nurseries. The [...] Read more.
The aim of the present study was to assess fungal and oomycete communities in the irrigation water of forest nurseries, focusing on plant pathogens in the hope of getting a better understanding of potential pathogenic microorganisms and spreading routes in forest nurseries. The study sites were at Anykščiai, Dubrava, Kretinga and Trakai state forest nurseries in Lithuania. For the collection of microbial samples, at each nursery five 100-L water samples were collected from the irrigation ponds and filtered. Following DNA isolation from the irrigation water filtrate samples, these were individually amplified using ITS rDNA as a marker and subjected to PacBio high-throughput sequencing. Clustering in the SCATA pipeline and the taxonomic classification of 24,006 high-quality reads showed the presence of 1286 non-singleton taxa. Among those, 895 were representing fungi and oomycetes. The detected fungi were 57.3% Ascomycota, 38.1% Basidiomycota, 3.1% Chytridiomycota, 0.8% Mucoromycota and 0.7% Oomycota. The most common fungi were Malassezia restricta E. Guého, J. Guillot & Midgley (20.1% of all high-quality fungal sequences), Pezizella discreta (P. Karst.) Dennis (10.8%) and Epicoccum nigrum Link (4.9%). The most common oomycetes were Phytopythium cf. citrinum (B. Paul) Abad, de Cock, Bala, Robideau, Lodhi & Lévesque (0.4%), Phytophthora gallica T. Jung & J. Nechwatal (0.05%) and Peronospora sp. 4248_322 (0.05%). The results demonstrated that the irrigation water used by forest nurseries was inhabited by a species-rich but largely site-specific communities of fungi. Plant pathogens were relatively rare, but, under suitable conditions, these can develop rapidly, spread efficiently through the irrigation system and be a threat to the production of high-quality tree seedlings. Full article
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25 pages, 4275 KiB  
Article
Development of Nonlinear Parsimonious Forest Models Using Efficient Expansion of the Taylor Series: Applications to Site Productivity and Taper
by Alexandru Amarioarei, Mihaela Paun and Bogdan Strimbu
Forests 2020, 11(4), 458; https://doi.org/10.3390/f11040458 - 18 Apr 2020
Cited by 4 | Viewed by 2735
Abstract
The parameters of nonlinear forest models are commonly estimated with heuristic techniques, which can supply erroneous values. The use of heuristic algorithms is partially rooted in the avoidance of transformation of the dependent variable, which introduces bias when back-transformed to original units. Efforts [...] Read more.
The parameters of nonlinear forest models are commonly estimated with heuristic techniques, which can supply erroneous values. The use of heuristic algorithms is partially rooted in the avoidance of transformation of the dependent variable, which introduces bias when back-transformed to original units. Efforts were placed in computing the unbiased estimates for some of the power, trigonometric, and hyperbolic functions since only few transformations of the predicted variable have the corrections for bias estimated. The approach that supplies unbiased results when the dependent variable is transformed without heuristic algorithms, but based on a Taylor series expansion requires implementation details. Therefore, the objective of our study is to investigate the efficient expansion of the Taylor series that should be included in applications, such that numerical bias is not present. We found that five functions require more than five terms, whereas the arcsine, arccosine, and arctangent did not. Furthermore, the Taylor series expansion depends on the variance. We illustrated the results on two forest modeling problems, one at the stand level, namely site productivity, and one at individual tree level, namely taper. The models that are presented in the paper are unbiased, more parsimonious, and they have a RMSE comparable with existing less parsimonious models. Full article
(This article belongs to the Special Issue Modeling Forest Stand Dynamics, Growth and Yield)
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18 pages, 1395 KiB  
Article
Restoration of Shortleaf Pine (Pinus echinata)-Hardwood Mixtures in Low Quality Mixed Upland Hardwood Stands Using Cluster Planting and Natural Regeneration
by David Clabo and Wayne Clatterbuck
Forests 2020, 11(4), 457; https://doi.org/10.3390/f11040457 - 17 Apr 2020
Cited by 5 | Viewed by 2603
Abstract
Cluster planting of shortleaf pine, along with various site preparation and release treatments, were tested to restore mixed shortleaf pine (Pinus echinata Mill.)–hardwood stands in areas where the shortleaf pine has diminished in recent years. Shortleaf pine–hardwood mixtures were once a common [...] Read more.
Cluster planting of shortleaf pine, along with various site preparation and release treatments, were tested to restore mixed shortleaf pine (Pinus echinata Mill.)–hardwood stands in areas where the shortleaf pine has diminished in recent years. Shortleaf pine–hardwood mixtures were once a common forest type throughout the Cumberland Mountains and Plateau physiographic regions of the southeastern United States. Knowledge of how to restore shortleaf pine–hardwood mixtures is limited throughout shortleaf pine’s large native range. The objectives of this study were to compare planted shortleaf pine and natural hardwood regeneration survival, growth, and composition following various site preparation and early release treatments. Cluster planting and partial timber harvesting were used to reintroduce shortleaf pine and create two-aged stands in the Cumberland Mountains of Tennessee, USA. Results indicated that shortleaf pine survival, basal diameter, and height growth did not differ following four growing seasons among treatments. Natural regeneration stem densities and heights within shortleaf pine clusters did not differ significantly by treatment. Natural regeneration stem densities differed by species group and height class across the site, while the treatment × species interaction term was also significant. At this early stage of stand development, the brown-and-burn treatment appears poised for greater shortleaf pine growth rates than the other treatments. The herbicide treatment had the fewest regenerating hardwoods per hectare and the most desirable hardwood species composition. Full article
(This article belongs to the Special Issue Silviculture for Restoration and Regeneration)
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20 pages, 2629 KiB  
Article
Impact of Invasive Tree Species on Natural Regeneration Species Composition, Diversity, and Density
by Marcin K. Dyderski and Andrzej M. Jagodziński
Forests 2020, 11(4), 456; https://doi.org/10.3390/f11040456 - 17 Apr 2020
Cited by 45 | Viewed by 7520
Abstract
Invasive tree species decrease ecosystem resilience with negative impacts on natural regeneration. The influence of alien tree species on ecosystems is unevenly recognized and does not always account for different habitat specificity. We assessed the impacts of the three most frequent invasive tree [...] Read more.
Invasive tree species decrease ecosystem resilience with negative impacts on natural regeneration. The influence of alien tree species on ecosystems is unevenly recognized and does not always account for different habitat specificity. We assessed the impacts of the three most frequent invasive tree species in European forests: Prunus serotina Ehrh., Quercus rubra L., and Robinia pseudoacacia L. on natural regeneration diversity, species composition, and density. We hypothesized that invaded forest types, in comparison with non-invaded, will differ in terms of species composition, will have lower taxonomic, functional, and phylogenetic diversity of natural regeneration, and will have lower densities of native tree species. We used a set of 189 study plots (200 m2) in a systematic design, established in various forest types in Wielkopolski National Park (West Poland). We analyzed impacts of forest type, accounting for soil C:N ratio, soil pH, and light availability on natural regeneration (woody species up to 0.5 m height) species composition, diversity, and density. We found an overlap of species composition among invaded and non-invaded forests and low impacts of invasive species on taxonomic diversity and functional richness. We found no impacts on phylogenetic diversity and other functional diversity components. In contrast, we found that the natural regeneration of forest-forming tree species reached lower densities in invaded than non-invaded forest types. However, sub-canopy and shrub species reached higher densities in invaded than non-invaded forest types. We confirmed that invasive tree species affect natural regeneration by decreasing the regeneration density of native tree species (in eight of nine tree species studied), species composition homogenization, and supporting natural regeneration of sub-canopy and shrub species. Therefore, the restoration of invaded forests requires eradication of invasive tree species to decrease propagule pressure and to stop decreases in the abundance of native tree species’ natural regeneration. Full article
(This article belongs to the Special Issue The Effects of Species Invasions and Dispersal on Forest Communities)
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18 pages, 6839 KiB  
Article
Radial Growth Adaptability to Drought in Different Age Groups of Picea schrenkiana Fisch. & C.A. Mey in the Tianshan Mountains of Northwestern China
by Liang Jiao, Xiaoping Liu, Shengjie Wang and Ke Chen
Forests 2020, 11(4), 455; https://doi.org/10.3390/f11040455 - 17 Apr 2020
Cited by 4 | Viewed by 2612
Abstract
Forest ecosystems are strongly impacted by extreme climate, and the age effects of radial growth under drought can provide profound understanding of the adaptation strategy of a tree species to climate change. Schrenk spruce (Picea schrenkiana Fisch. & C.A. Mey) trees of [...] Read more.
Forest ecosystems are strongly impacted by extreme climate, and the age effects of radial growth under drought can provide profound understanding of the adaptation strategy of a tree species to climate change. Schrenk spruce (Picea schrenkiana Fisch. & C.A. Mey) trees of three age groups (young, middle-aged, and old) were collected to establish the tree-ring width chronologies in the eastern Tianshan Mountains of northwestern China. Meanwhile, we analyzed and compared the response and resistance disparities of radial growth to drought in trees of different age groups. The results showed that (1) drought stress caused by increasing temperatures was the main factor limiting the radial growth of Schrenk spruce, (2) the old and young trees were more susceptible to drought stress than the middle-aged trees, as suggested by the responses of Schrenk spruce trees and based on the SPEI (standardized precipitation evapotranspiration index), and (3) the difference of the resistance indexes (resistance, recovery, resilience, and relative resilience) of three age groups to drought supported that the resistance values were in the order middle age > young age > old age, but the recovery, resilience, and relative resilience values were in the order old age > young age > middle age. These results will provide a basis for the ecological restoration and scientific management of dominant coniferous tree species of different age groups in the sub-alpine forest ecosystems of the arid regions under climate change scenarios. Full article
(This article belongs to the Section Forest Ecology and Management)
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16 pages, 12782 KiB  
Article
Spatiotemporal Pattern and Aggregation Effects of Poplar Canker in Northeast China
by He Yan, Liyuan Chen, Quansheng Ge, Chengming Tian and Jixia Huang
Forests 2020, 11(4), 454; https://doi.org/10.3390/f11040454 - 17 Apr 2020
Cited by 2 | Viewed by 2362
Abstract
Research Highlights: This study looks at poplar canker caused by Cytospora chrysosperma as a geographical phenomenon, and it applies spatial statistics to reveal the pattern and aggregation effects of the disease on a large scale in time and space. The incidence area of [...] Read more.
Research Highlights: This study looks at poplar canker caused by Cytospora chrysosperma as a geographical phenomenon, and it applies spatial statistics to reveal the pattern and aggregation effects of the disease on a large scale in time and space. The incidence area of poplar canker in Northeast China has spatial (spatiotemporal) aggregation effects, which emphasize the importance of coordinated prevention. The results of spatial and spatiotemporal clusters can guide specific regional prevention and indicate the possible predisposing factors, respectively. Background and Objectives: Poplar canker, a harmful forest biological disease that is widespread throughout Northeast China, brings enormous ecological and economic losses. The limited cognition of its spatiotemporal pattern and aggregation effects restricts the decision-making for regional prevention and the identification of disease-inducing conditions. This study aims to explore the spatiotemporal pattern and to detect the aggregation effects of the disease, trying to provide references for prevention. Materials and Methods: According to the incidence data of poplar canker reported by each county in Northeast China from 2002 to 2015, we mapped the distribution of the incidence rate in ArcGIS and performed retrospective scan statistics in SaTScan to detect the spatial and spatiotemporal aggregation effects of the incidence area. Results: The spatiotemporal pattern of poplar canker’s incidence rate presents the characteristic of “outbreak-aggregation-spread-stability.” The incidence area of the disease when we performed spatial aggregation scan statistics showed the primary cluster covering Liaoning province (LLR = 86469.86, p < 0.001). The annual spatial scan statistics detected a total of 14 primary clusters and 37 secondary clusters, indicating three phases of aggregation. The incidence area of disease also shows spatiotemporal aggregation effects with the primary cluster located around Liaoning province, appearing from 2009 to 2015 (LLR = 64182.00, p < 0.001). Conclusions: The incidence area of poplar canker presents significant characteristics of spatial and spatiotemporal aggregation, and we suggest attaching importance to the clues provided by the aggregation effects in disease prevention and identification of predisposing factors. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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16 pages, 1405 KiB  
Review
Ectomycorrhizal Fungi: Participation in Nutrient Turnover and Community Assembly Pattern in Forest Ecosystems
by Yanjiao Liu, Xiangzhen Li and Yongping Kou
Forests 2020, 11(4), 453; https://doi.org/10.3390/f11040453 - 17 Apr 2020
Cited by 40 | Viewed by 9339
Abstract
Ectomycorrhizal fungi (EcMF) are involved in soil nutrient cycling in forest ecosystems. These fungi can promote the uptake of nutrients (e.g., nitrogen (N) and phosphorus (P)) and water by host plants, as well as facilitate host plant growth and resistance to stresses and [...] Read more.
Ectomycorrhizal fungi (EcMF) are involved in soil nutrient cycling in forest ecosystems. These fungi can promote the uptake of nutrients (e.g., nitrogen (N) and phosphorus (P)) and water by host plants, as well as facilitate host plant growth and resistance to stresses and diseases, thereby maintaining the aboveground primary productivity of forest ecosystems. Moreover, EcMF can acquire the carbon (C) sources needed for their growth from the host plants. The nutrient regulation mechanisms of EcMF mainly include the decay of soil organic matter via enzymatic degradation, nonenzymatic mechanism (Fenton chemistry), and priming effects, which in turn promote C and N cycling. At the same time, EcMF can secrete organic acids and phosphatases to improve the availability of soil P, or increase mycelium inputs to facilitate plant acquisition of P. The spatiotemporal distribution of EcMF is influenced by a combination of historical factors and contemporary environmental factors. The community of EcMF is associated with various factors, such as climate change, soil conditions, and host distribution. Under global climate change, investigating the relationships between the nutrient cycling functions of EcMF communities and their distribution patterns under various spatiotemporal scales is conducive to more accurate assessments of the ecological effects of EcMF on the sustainable development of forest. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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