Forests, Volume 8, Issue 10 (October 2017) – 51 articles

Schima superba Gardn. et Champ. is a perennial, evergreen tree valued for its eco-protection and commercial values in China. In this study, we investigate the breeding system, reproductive ecology and pollination biology of S. superba in a seed orchard. The flowers are hermaphrodite and protogynous. The viability of the pollen is inactivated rapidly, and the stigma maintains a high receptivity within the flower lifespan. Flowers typically offer pollen and nectar to visitors. The flowers possess a typical insect pollination syndrome, and three visitors (Apis cerana cerana Fabricius, Protaetia brevitarsis Lewis, and Popillia mutans Newman) are observed on flowers during the study period. The visitation frequency per minute and capability of pollen removal and deposition of A. cerana are significantly higher than P. brevitarsis and P. mutans, although the pollinator efficiency is lower than those shown by the two beetles. Fruit set (28.27%) and seed set (6.57%) percentages resulting from open-pollination are significantly lower than those resulting from cross-pollination (fruit/seed set, 43.73%/11.66%), and the pollen limitation index (L) was 0.34, suggesting that seed production is pollen-limited in the seed orchard. The pollen/ovule ratio (P/O) and outcrossing index (OCI) values are 6686.67 and 4, respectively. The self-incompatibility index (ISI) was estimated to be 0.95. Results from hand-pollination, pollen tube growth experiments and the ISI value show that S. superba is late-acting self-incompatible. The synthetic results indicate that A. cerana is the most efficient pollinator of S. superba, and seed production is frequently limited by pollinators, fruit abortion, and pollen quality. Full article

Coarse woody debris (CWD) is an essential component in defining the structure and function of forest ecosystems. Long-term dynamics of CWD characteristics not only affect the release rates of chemical elements from CWD, but also the species diversity of inhabiting plants, animals, insects, and microorganisms as well as the overall health of ecosystems. However, few quantitative studies have been done on the long-term dynamics of CWD characteristics in forest ecosystems in China. In this study, we conducted nine tree censuses between 1996 and 2016 at the Huoditang Experimental Forest in the Qinling Mountains of China. We quantified forest biomass including CWD and CWD characteristics such as decay states and diameter classes during this period and correlated with stand, site, and climatic variables. The forest biomass was dominated by live tree biomass (88%); followed by CWD mass (6%–10%). Understory biomass contributed only a small portion (1%–4%) of the overall biomass. Significant differences in average annual increment of CWD mass were found among forest stands of different species (p < 0.0001). Forest biomass, stand age, forest type, aspect, slope, stand density, annual average temperature, and precipitation were all significantly correlated with CWD mass (p < 0.05), with forest type exhibiting the strongest correlation (r² = 0.8256). Over time, the annual mass of different CWD characteristics increased linearly from 1996–2016 across all forest types. Our study revealed that forest biomass, including CWD characteristics, varied by forest type. Stand and site characteristics (forest biomass, forest type, aspect, slope and stand density) along with temperature and precipitation played a major role in the dynamics of CWD in the studied forest ecosystems. Full article

Pine processionary moth (PPM) is one of the most destructive insect defoliators in the Mediterranean for many conifers, causing losses of growth, vitality and eventually the death of trees during outbreaks. There is a growing need for cost-effective monitoring of the temporal and spatial impacts of PPM in forest ecology to better assess outbreak spread patterns and provide guidance on the development of measures targeting the negative impacts of the species on forests, industry and human health. Remote sensing technology mounted on unmanned aerial systems (UASs) with high-resolution image processing has been proposed to assess insect outbreak impacts at local and forest stand levels. Here, we used UAS-acquired RGB imagery in two pine sites to quantify defoliation at the tree-level and to verify the accuracy of the estimates. Our results allowed the identification of healthy, infested and completely defoliated trees and suggested that pine defoliation estimates using UASs are robust and allow high-accuracy (79%) field-based infestation indexes to be derived that are comparable to those used by forest technicians. When compared to current field-based methods, our approach provides PPM impact assessments with an efficient data acquisition method in terms of time and staff, allowing the quantitative estimation of defoliation at tree-level scale. Furthermore, our method could be expanded to a number of situations and scaled up in combination with satellite remote sensing imagery or citizen science approaches. Full article

Forest attributes such as tree heights, diameter distribution, volumes, and biomass can be modeled utilizing the relationship between remotely sensed metrics as predictor variables, and measurements of forest attributes on the ground. The quality of the models relies on the actual relationship between the forest attributes and the remotely sensed metrics. The processing of airborne laser scanning (ALS) point clouds acquired under heterogeneous terrain conditions introduces a distortion of the three-dimensional shape and structure of the ALS data for tree crowns and thus errors in the derived metrics. In the present study, Procrustean transformation and histogram matching were proposed as a means of countering the distortion of the ALS data. The transformations were tested on a dataset consisting of 192 field plots of 250 m² in size located on a gradient from gentle to steep terrain slopes in western Norway. Regression models with predictor variables derived from (1) Procrustean transformed- and (2) histogram matched point clouds were compared to models with variables derived from untransformed point clouds. Models for timber volume, basal area, dominant height, Lorey’s mean height, basal area weighted mean diameter, and number of stems were assessed. The results indicate that both (1) Procrustean transformation and (2) histogram matching can be used to counter crown distortion in ALS point clouds. Furthermore, both techniques are simple and can easily be implemented in the traditional processing chain of ALS metrics extraction. Full article

Wildfire refugia are forest patches that are minimally-impacted by fire and provide critical habitats for fire-sensitive species and seed sources for post-fire forest regeneration. Wildfire refugia are relatively understudied, particularly concerning the impacts of subsequent fires on existing refugia. We opportunistically re-visited 122 sites classified in 1994 for a prior fire refugia study, which were burned by two wildfires in 2012 in the Cascade mountains of central Washington, USA. We evaluated the fire effects for historically persistent fire refugia and compared them to the surrounding non-refugial forest matrix. Of 122 total refugial (43 plots) and non-refugial (79 plots) sites sampled following the 2012 wildfires, one refugial and five non-refugial plots did not burn in 2012. Refugial sites burned more severely and experienced higher tree mortality than non-refugial plots, potentially due to the greater amount of time since the last fire, producing higher fuel accumulation. Although most sites maintained the pre-fire development stage, 19 percent of sites transitioned to Early development and 31 percent of sites converted from Closed to Open canopy. These structural transitions may contribute to forest restoration in fire-adapted forests where fire has been excluded for over a century, but this requires further analysis. Full article

Identifying the potentially suitable climatic geographical range for Liriodendron chinense (L. chinense) and predicting its responses to climate change is urgently necessary, as L. chinense is an important tertiary relict tree species. In this study, we simulated the potentially suitable climatic habitat of L. chinense in China using maximum entropy (MaxEnt) modeling. We found that the MaxEnt model was highly accurate with an average training Area Under the Curve (AUC) value of 0.912. Annual precipitation and mean temperature of the driest quarter are the main factors controlling the geographical distribution of L. chinense. Currently, the suitable climatic habitat of L. chinense is mainly located in Southeastern China. Forecasted patterns of predicted suitable climatic habitat show a significant change by the 2050s and 2070s, suggesting that the suitable climatic habitat of L. chinense would shift north with future climate change, based on four Representative Concentrations Pathways for carbon dioxide (CO₂) emissions. The southern extent of the current distribution would become unsuitable for L. chinense, pointing to a threat of extinction and highlighting the urgent need for conservation within the next half century. The potentially suitable climatic habitat of L. chinense was predicted to move further north, but those habitat gains may be inaccessible because of dispersal limitations. Our unique findings offer a climatic suitability map for L. chinense in China, which can help to identify locations where L. chinense may already exist, but has not yet been detected; to recognize locations where L. chinense is likely to spread in the future given forecasted climate change; and to select priority areas for its introduction, cultivation, and conservation. Full article

There is limited information on how velvet leaf blueberry (Vaccinium myrtilloides Michx.) responds to fires and existing small forest gaps associated with narrow linear disturbances. We measured the effects of narrow forest linear gaps from seismic lines used for oil and gas exploration versus adjacent (control) forests across a fire severity (% tree mortality) gradient on the presence, abundance (cover), vigor (height), and berry production of Vaccinium myrtilloides in recently (five-year) burned jack pine (Pinus banksiana Lamb.) forests near Fort McMurray, Alberta. Presence was greatest in forests that experienced low to moderately-high fire severities with declines at high fire severity. Abundance did not differ among seismic lines or adjacent forest, nor did it differ along a fire severity gradient. In contrast, vigor and berry production were greater on seismic lines compared to adjacent forests with fire severity positively affecting berry production, but not plant vigor. After controlling for changes in plant cover and vigor, berry production still increased with fire severity and within seismic lines compared with adjacent forests. Our findings suggest that narrow gaps from linear disturbances and fire severity interact to affect the fecundity (berry production) and growth (height) of Vaccinium myrtilloides. This has important implications for assessing the ecological effects of fire on linear disturbances associated with energy exploration in the western boreal forest. Full article

Secondary lucidophyllous forest is one of the dominant forests in human-dominated subtropical/warm-temperate regions in East Asia. There were few direct monitoring techniques to elucidate the following hypotheses: (a) self-thinning may govern the stand development process and (b) wood production decline can be observed during secondary succession in a lucidophyllous forest. We conducted a long-term study at a permanent plot in central Japan, since 1989. The forest consists mainly of Castanopsis cuspidata in a canopy layer, Cleyera japonica, and Eurya japonica in a subtree layer. During the 28-year period, the basal area of the stand significantly increased due to the growth of C. cuspidata, from 29.18 ± 1.84 (87.8% of total) to 38.71 ± 2.22 m² ha⁻¹ (91.9%), while the stem density of C. cuspidata significantly decreased from 666 ± 13 to 404 ± 10 stems ha⁻¹ in proportion to accumulating biomass (117.8 to 166.6 ton ha⁻¹). The annual woody net primary production ranged from 2.40 ± 0.13 to 3.93 ± 0.33 ton ha⁻¹ year⁻¹ as a nearly 70-year-old forest. There was no age-related decline of woody net primary production (NPP) was found during secondary succession, and the growth of individual tree still increased when the self-thinning process governed the stand. Full article

New techniques have recently appeared that can extend the advantages of grapple yarding to fast-growing plantations. The most promising technique consists of an excavator-base un-guyed yarder equipped with new radio-controlled grapple carriages, fed by another excavator stationed on the cut-over. This system is very productive, avoids in-stand traffic, and removes operators from positions of high risk. This paper presents the results of a long-term study conducted on 12 different teams equipped with the new technology, operating in the fast-growing black wattle (Acacia mangium Willd) plantations of Sarawak, Malaysia. Data were collected continuously for almost 8 months and represented 555 shifts, or over 55,000 cycles—each recorded individually. Production, utilization, and machine availability were estimated, respectively at: 63 m³ per productive machine hour (excluding all delays), 63% and 93%. Regression analysis of experimental data yielded a strong productivity forecast model that was highly significant, accounted for 50% of the total variability in the dataset and was validated with a non-significant error estimated at less than 1%. The figures reported in this study are especially robust, because they were obtained from a long-term study that covered multiple teams and accumulated an exceptionally large number of observations. Full article

Individuals and families collectively own more than 118 million ha of forestland in the USA. Using data from the USDA Forest Service’s National Woodland Owners Survey (NWOS), we characterize ecosystem services being produced on family forests as well as the beneficiaries who enjoy them. Approximately half of family forest owners provide one or more provisioning services. With the exception of logs, the provisioning services provided by the majority of owners are enjoyed directly by owners or their close associates (i.e., family, friends, and neighbors). Similarly, while more than half of family forest owners have provided recreational opportunities, a cultural service, to their close associates, fewer than 6% of owners have sold or provided recreational services to the general public. Regulating and supporting services are linked to the maintenance of long-term forest cover. Greater than 80% of family forest owners desire to maintain the forested condition of their land, whereas a much smaller percentage of these owners have entered into conservation easements or have collected money for conservation purposes. In addition, many owners have engaged in activities expected to increase the future capacity of their land to provide multiple ecosystem services, both excludable and non-excludable. Full article

Castanea is a hardwood forest genus of considerable agro-economic importance for both timber and nut production. Chestnuts are one of the most significant nut crops in the temperate zone. However, this species is threatened by pollution, social factors, economical changes, and two major fungal diseases: ink disease (Phytophthora spp.), and chestnut blight canker (Cryphonectria parasitica). Similar to other wood species, chestnuts are difficult to propagate both generatively by seed and vegetatively by means of grafting or cuttings. Biotechnological methods such as in vitro culture have been developed in the last few years as an alternative to conventional vegetative propagation. Biotechnology plays a very important role not only in the propagation of selected individuals (being used at a commercial level), but also in its short-term preservation, and offers the possibility of preserving the propagated material in the medium-term (cold storage) or long-term using cryopreservation. Full article

Rust is a major Eucalyptus spp. disease, which is especially damaging for early-stage plants. The aim of this study was to verify the pre-infection process of Austropuccinia psidii (A. psidii) in the leaves of three phenological stages of Eucalyptus clones with different resistance levels. Plants from the hybrids of Eucalyptus urophylla × Eucalyptus grandis (E. grandis) with variable levels of resistance to this disease were used. The pathogen was inoculated in vitro on abaxial leaf discs of first, third, and fifth leaf stages and maintained under conditions suitable for disease development. Subsequently, samples from these discs were collected 24 and 120 h after inoculation and processed using scanning electron microscopy analysis. No symptoms were seen in any leaf stage of the resistant clone. Additionally, a low incidence of A. psidii germination (1.3–2%) and appressoria (0–0.5%) in three leaf stages was observed. However, the first leaf stage of the susceptible clone presented germination of large numbers of urediniospores (65%) with appressoria (55%) and degradation of the cuticle and wax. From the third stage, the percentage of germinated urediniospores (<15%) and appressoria (<2%) formation of this clone decreased. Protrusions on the leaf surface, associated with the pathogen, were observed on the first and third leaf stages of the resistant clone and on the fifth stage of the susceptible clone, suggesting a possible defensive plant reaction. Full article

The design of forest inventories and development of new sampling methods useful in such inventories normally have a two-fold target of design unbiasedness and minimum variance in mind. Many considerations such as costs go into the choices of sampling method for operational and other levels of inventory. However, the variance in terms of meeting a specified level of precision is always among the most important criteria. Similarly, in designing new sampling methods, one always seeks to decrease the variance of the new method compared to existing methods. This paper provides a review of some graphical methods that may prove useful in these endeavors. In addition, in the case of the comparison of variances between new and existing methods, it introduces the use of wavelet filtering to decompose the sampling variance associated with the estimators under consideration into scale-based components of variance. This yields an analysis of variance of sorts regarding how the methods compare over different distance/area classes. The graphical tools are also shown to be applicable to the wavelet decomposition. These graphical tools may prove useful in summarizing the results for inventory design, while the wavelet results may prove helpful as we begin to look at sampling designs more in light of spatial processes for a given population of trees or downed coarse woody debris. Full article

The methods for measuring vegetation cover in Mexican forest surveys are subjective and imprecise. The objectives of this research were to compare the sampling designs used to measure the vegetation cover and estimate the over and understory cover in different land uses, using digital photography. The study was carried out in 754 circular sampling sites in central Mexico. Four spatial sampling designs were evaluated in three spatial distribution patterns of the trees. The sampling designs with photographic captures in diagonal form had lower values of mean absolute error (MAE < 0.12) and less variation in random and grouped patterns. The Carbon and Biomass Sampling Plot (CBSP) design was chosen due to its smaller error in the different spatial tree patterns. The image processing was performed using threshold segmentation techniques and was automated through an application developed in the Python language. The two proposed methods to estimate vegetation cover through digital photographs were robust and replicable in all sampling plots with different land uses and different illumination conditions. The automation of the process avoided human estimation errors and ensured the reproducibility of the results. This method is working for regional surveys and could be used in national surveys due to its functionality. Full article

Shifting fire regimes alter forest structure assembly in ponderosa pine forests and may produce structural heterogeneity following stand-replacing fire due, in part, to fine-scale variability in growing environments. We mapped tree regeneration in eighteen plots 11 to 15 years after stand-replacing fire in Colorado and South Dakota, USA. We used point pattern analyses to examine the spatial pattern of tree locations and heights as well as the influence of tree interactions and topography on tree patterns. In these sparse, early-seral forests, we found that all species were spatially aggregated, partly attributable to the influence of (1) aspect and slope on conifers; (2) topographic position on quaking aspen; and (3) interspecific attraction between ponderosa pine and other species. Specifically, tree interactions were related to finer-scale patterns whereas topographic effects influenced coarse-scale patterns. Spatial structures of heights revealed conspecific size hierarchies with taller trees in denser neighborhoods. Topography and heterospecific tree interactions had nominal effect on tree height spatial structure. Our results demonstrate how stand-replacing fires create heterogeneous forest structures and suggest that scale-dependent, and often facilitatory, rather than competitive, processes act on regenerating trees. These early-seral processes will establish potential pathways of stand development, affecting future forest dynamics and management options. Full article

Altitude significantly affects vegetation growth and distribution, including the developmental stages of a forest. We used shotgun Illumina sequencing to analyze microbial community composition and functional potential in melojo-oak (Quercus pyrenaica Willd.) rhizospheric soil for three different development stages along an altitudinal gradient: (a) a low altitude, non-optimal site for forest maintenance; (b) an intermediate altitude, optimal site for a forest; and (c) a high altitude, expansion site with isolated trees but without a real forest canopy. We observed that, at each altitude, the same microbial taxa appear both in the taxonomic analysis of the whole metagenome and in the functional analysis of the methane, sulfur and nitrogen metabolisms. Although there were no major differences at the functional level, there were significant differences in the abundance of each taxon at the phylogenetic level between the rhizospheres of the forest (low and intermediate altitudes) and the expansion site. Proteobacteria and Actinobacteria were the most differentially abundant phyla in forest soils compared to the expansion site rhizosphere. Moreover, Verrucomicrobia, Bacteroidetes and Nitrospirae phyla were more highly represented in the non-forest rhizosphere. Our study suggests that rhizospheric microbial communities of the same tree species may be affected by development stage and forest canopy cover via changes in soil pH and the C/N ratio. Full article

The Upper Parana Atlantic Forest (BAAPA) in Paraguay is one of the most threatened tropical forests in the world. The rapid growth of deforestation has resulted in the loss of 91% of its original cover. Numerous efforts have been made to halt deforestation activities, however farmers’ perception towards the forest and its benefits has not been considered either in studies conducted so far or by policy makers. This research provides the first multi-temporal analysis of the dynamics of the forest within the BAAPA region on the one hand, and assesses the way farmers perceive the forest and how this influences forest conservation at the farm level on the other. Remote sensing data acquired from Landsat images from 1999 to 2016 were used to measure the extent of the forest cover and deforestation rates over 17 years. Farmers’ influence on the dynamics of the forest was evaluated by combining earth observation data and household survey results conducted in the BAAPA region in 2016. Outcomes obtained in this study demonstrate a total loss in forest cover of 7500 km². Deforestation rates in protected areas were determined by management regimes. The combination of household level and remote sensing data demonstrated that forest dynamics at the farm level is influenced by farm type, the level of dependency/use of forest benefits and the level of education of forest owners. An understanding of the social value awarded to the forest is a relevant contribution towards preserving natural resources. Full article

Multipurpose trees such as Senegalia senegal are widespread in arid and semi-arid lands that have natural or induced saline soils and poor soil fertility. Such environmental problems impact growth and have the potential to influence plant physiological adaptations. Identifying superior genotypes better adapted to these environmental stresses will be of great importance for tree selection for reclamation of degraded drylands. The main objective of this study was to examine the growth performance, and physiological and morphological adaptations to salinity, and fertility treatments of different Senegalia senegal families. We used five families (DB16, DB14, K4B19, K17B19, NB1) selected from 60 families of a Senegalia senegal progeny trial in Dahra, Senegal. Seedlings were grown under greenhouse conditions by watering all plants for three weeks and then stopping all watering for three more weeks. In a randomized complete block design, a two-level factorial combination was used for salinity (zero and 183.1 mM NaCl added) and fertility (zero and 100 kg/ha N-P-K added) treatments. A significant family × salt × fertilizer interaction was found for all biomass parameters (leaf dry matter, stem dry matter, root dry matter, and leaf area). The fertilizer application resulted in a significant increase of total biomass of all families, ranging from 63% to 237% for NB1 and K17B19, respectively. In contrast, salt only decreased total biomass of NB1 and K17B19 increased growth. Despite similar net photosynthetic rates before treatment started, fertilizer and salinity induced different effects between families. Prior to drought stress, fertilizer did not affect photosynthesis of DB16, while salt significantly decreased stomatal conductance of all families. DB16 and N1B1, despite significant differences of stomata size and density, significantly decreased transpiration, and thereby increased their intrinsic water use efficiency. Under drought, relative growth rate was significantly decreased. Given that genotype differences were found, these families and salinity and fertilizer treatments need to be explored in field trials. Full article

As a multiple function tree species, Cyclocarya paliurus (Batal) Iljinskaja is mainly planted and managed for timber production and medical use. To improve the seed use efficiency and outplanting performance of C. paliurus, the effects of container types and growth medium on the seedling growth and root morphology of C. paliurus were investigated by using a completely randomized block experimental design with a 4 × 3 factorial arrangement during nursery culture. Both container type and growth medium significantly affected the growth, biomass, and root morphological indexes of C. paliurus seedlings, but container size had a greater effect on the seedling quality of C. paliurus than the growth medium formula. The root-collar diameter and height of the seedlings were positively and significantly correlated with the biomass variables and root morphological variables, and could be considered essential attributes for evaluating seedling quality. Based on the results from this study, the management regime used here in C. paliurus seedling production is suggested to ensure good quality seedling delivery. Our study provides not only valuable insights into the container seedling culture of C. paliurus, it also enables nursery managers to optimize seedling production. Full article

The photochemical reflectance index (PRI) and red-edge region of the spectrum are known to be sensitive to plant physiological processes, and through measurement of these optical signals it is possible to use non-invasive remote sensing to monitor the plant photosynthetic status in response to environmental stresses such as drought. We conducted a greenhouse experiment using Quercus ilex, a Mediterranean evergreen oak species, to investigate the links between leaf-level PRI and the red-edge based reflectance ratio (R690/R630) with CO₂ assimilation rates (A), and photochemical efficiency (F_V/F_M and Yield) in response to a gradient of mild to extreme drought treatments (nine progressively enhanced drought levels) and corresponding recovery. PRI and R690/R630 both decreased under enhanced drought stress, and had significant correlations with A, F_V/F_M and Yield. The differential values between recovery and drought treatments of PRI (ΔPRI_recovery) and R690/R630 (ΔR690/R630_recovery) increased with the enhanced drought levels, and significantly correlated with the increases of ΔA_recovery, ΔF_V/F_Mrecovery and ΔYield_recovery. We concluded that both PRI and R690/R630 were not only sensitive to enhanced drought stresses, but also highly sensitive to photosynthetic recovery. Our study makes important progress for remotely monitoring the effect of drought and recovery on photosynthetic regulation using the simple physiological indices of PRI and R690/R630. Full article

Wildfire often causes tremendous changes in ecosystems, particularly in subalpine and alpine areas, which are vulnerable due to severe climate conditions such as cold temperature and strong wind. This study aimed to clarify the effect of tree re-planting on ecosystem services such as the soil microbial community after several decades. We compared the re-planted forest and grassland with the mature forest as a reference in terms of soil microbial biomass C and N (C_mic and N_mic), enzyme activities, phospholipid fatty acids (PLFA) composition, and denaturing gradient gel electrophoresis (DGGE). The C_mic and N_mic did not differ among the grassland, re-planted forest and mature forest soil; however, ratios of C_mic/C_org and N_mic/N_tot decreased from the grassland to re-planted forest and mature forest soil. The total PLFAs and those attributed to bacteria and Gram-positive and Gram-negative bacteria did not differ between the re-planted forest and grassland soil. Principle component analysis of the PLFA content separated the grassland from re-planted forest and mature forest soil. Similarly, DGGE analysis revealed changes in both bacterial and fungal community structures with changes in vegetation. Our results suggest that the microbial community structure changes with the re-planting of trees after a fire event in this subalpine area. Recovery of the soil microbial community to the original state in a fire-damaged site in a subalpine area may require decades, even under a re-planted forest. Full article

Mapping forest types in a natural heterogeneous forest environment using remote sensing data is a long-standing challenge due to similar spectral reflectance from different tree species and significant time and resources are required for acquiring and processing the remote sensing data. The purpose of this research was to determine the optimum number of remote sensing images and map the Sal forest through the analysis of Vegetation Index (VI) signatures. We analyzed the eight days’ composite moderate resolution imaging spectroradiometer (MODIS) time series normalized differential vegetation index (NDVI), and enhanced vegetation index (EVI) for the whole year of 2015. Jeffries-Matusita (J-M) distance was used for the separability index. Performance of EVI and NDVI was tested using random forest (RF) and support vector machine (SVM) classifiers. Boruta algorithm and statistical analysis were performed to identify the optimum set of imageries. We also performed data level five-fold cross validation of the model and field level accuracy assessment of the classification map. The finding confirmed that EVI with SVM (F-score of Sal 0.88) performed better than NDVI with either SVM or RF. The optimum 12 images during growing and post monsoon season significantly decreased processing time (to one-fourth) without much deteriorating accuracy. Accordingly, we were able to map the Sal forest whose area is accounted for about 36% of the 82% forest cover in the study area. The proposed methodology can be extended to produce a temporal forest type classification map in any other location. Full article

Forests in Washington State generate substantial economic revenue from commercial timber harvesting on private lands. To investigate the rates, causes, and spatial and temporal patterns of forest harvest on private tracts throughout the Cascade Mountains, we relied on a new generation of annual land-use/land-cover (LULC) products created from the application of the Continuous Change Detection and Classification (CCDC) algorithm to Landsat satellite imagery collected from 1985 to 2014. We calculated metrics of landscape pattern using patches of intact and harvested forest in each annual layer to identify changes throughout the time series. Patch dynamics revealed four distinct eras of logging trends that align with prevailing regulations and economic conditions. We used multiple logistic regression to determine the biophysical and anthropogenic factors that influence fine-scale selection of harvest stands in each time period. Results show that private lands forest cover became significantly reduced and more fragmented from 1985 to 2014. Variables linked to parameters of site conditions, location, climate, and vegetation greenness consistently distinguished harvest selection for each distinct era. This study demonstrates the utility of annual LULC data for investigating the underlying factors that influence land cover change. Full article

Fine-resolution studies on the stem radius variation at short timescale can provide useful information about the tree growth process and the major environmental variables that trigger and drive stem radius variation. This study investigated the stem radius variation of Larix principis-rupprechtii Mayr growing in the semi-humid Liupan Mountains of Northwest China at daily and seasonal scales using high-resolution automatic band dendrometers from May to October in 2015. The results showed that the stem radius variation of Larix principis-rupprechtii has a clear diurnal pattern which can be divided into contraction, recovery, and increment phases; and also a seasonal pattern which can be divided into three stages: (1) the rapid growth stage in spring (stage 1) with the radius increment of 94.0% of the total in the entire growing period; (2) the persistent shrinkage stage in the dry summer (stage 2) with a negative diurnal radius increment for most days, and a significantly larger amplitude of stem contraction and recovery than other stages; (3) the minimal growth stage in autumn (stage 3), mainly caused by the lowering temperature and leaf area. The amplitude of stem contraction was significantly correlated with air temperature (both the mean and highest value) in all three stages: vapor pressure deficit (VPD) in stage 1; relative humidity (RH), VPD and soil moisture (M_s) in stage 2; and soil temperature (T_s) in stage 3. This indicates that the stem radius contraction was mainly controlled by the factors influencing tree transpiration rate in spring and autumn stages, but jointly controlled by the factors influencing both the tree transpiration rate and the soil moisture availability in the dry summer stage. The factors controlling the stem radius recovery was similar to the stem contraction. The amplitude of stem increment was significantly correlated with the rainfall amount and air temperature (both the mean and highest value) in stage 1 and 3, M_s in stage 2, and the lowest air temperature and T_s in stage 3. This indicates that temperature and precipitation were the key factors controlling the stem radius increment in the spring and autumn stages, and soil moisture was the main factor limiting the stem radius increment in the dry summer stage at the study site with semi-humid climate in Northwest China. Full article

Piptoporus betulinus, a brown-rot parasitic fungus of birch trees (Betula species), has been used as a common anti-parasitic and antibacterial agent. The lack of genetic resource data for P. betulinus has limited the exploration of this species. In this present study, we used Illumina Hiseq 2500 technology to examine the transcriptome assembly of P. betulinus in response to birch sawdust induction. By de novo assembly, 21,882 non-redundant unigenes were yielded, and 21,255 (97.1%) were annotated with known gene sequences. A total of 340 responsive unigenes were highly homologous with putative lignocellulose-degrading enzyme candidates. Additionally, 86 unigenes might be involved in the chemical reaction in xenobiotics biodegradation and metabolism, which suggests that this fungus could convert xenobiotic materials and has the potential ability to clean up environmental pollutants. To our knowledge, this was the first study on transcriptome sequencing and comparative analysis of P. betulinus, which provided a better understanding of molecular mechanisms underlying birch sawdust induction and identified lignocelluloses degrading enzymes. Full article

Rising export of wood pellets from southern United States would bring more land under loblolly pine (Pinus taeda L.) at the expense of other competitive land uses. We developed an approach to project potential changes in existing land uses by integrating site suitability analysis with historical land use dynamics in a watershed located within Oconee River Basin, Georgia, United States. We developed a GIS-based site suitability model to classify land into three categories (High, Medium, and Low) for loblolly pine. Then, we calculated historical rates of land use changes in the selected watershed. Finally, we integrated the output of suitability analysis with the projected rates of land use changes under the two scenarios of wood pellet demand (High and Low) to determine an increase in area under loblolly pine for 2016, 2021, and 2026 in a spatially explicit manner. Relative to 2011, the combined changes in the shrubland and evergreen forest land cover categories under High Demand scenario were 7.6, 14.6, and 21.1% and under Low Demand scenario were 3.8, 7.5, and 11.1% for the years 2016, 2021, and 2026, respectively. The developed approach could be applied in a relatively short time at modest spatial scales. The outputs of this study can also be used to determine the environmental implications of land use changes for ensuring the overall sustainability of wood-based bioenergy development in the United States and beyond. Full article

The relationship between acoustic velocity (v_d) and the dynamic modulus of elasticity (m_e), wood density (w_d), microfibril angle, tracheid wall thickness (w_t,), radial and tangential diameters, fibre coarseness (c_o) and specific surface area (s_a), within standing red pine (Pinus resinosa Ait.) trees, was investigated. The data acquisition phase involved 3 basic steps: (1) random selection of 54 sample trees from 2 intensively-managed 80-year-old plantations in central Canada; (2) attainment of cardinal-based v_d measurements transecting the breast-height position on each sample tree; and (3) felling, sectioning and obtaining cross-sectional samples from the first 5.3 m sawlog from which Silviscan-based area-weighted mean attribute estimates were determined. The data analysis phase consisted of applying graphical and correlation analyses to specify regression models for each of the 8 attribute-acoustic velocity relationships. Results indicated that viable relationships were obtained for m_e, w_d, w_t, c_o and s_a based on a set of statistical measures: goodness-of-fit (42%, 14%, 45%, 27% and 43% of the variability explained, respectively), lack-of-fit (unbiasedness) and predictive precision (±12%, ±8%, ±7%, ±8% and ±6% error tolerance intervals, respectively). Non-destructive approaches for estimating the prerequisite w_d value when deploying the analytical framework were also empirically evaluated. Collectively, the proposed approach and associated results provide the foundation for the development of a comprehensive and precise end-product segregation strategy for use in red pine management. Full article

Hyper-arid regions are expected to undergo climatic change, but only a few research works have so far been conducted on the dynamics of carbon dioxide (CO₂) fluxes and their consequent responses to various bioclimatic factors, which is mainly attributable to a limited set of flux observations. In this study, the CO₂ fluxes exchanged between the forest and the atmosphere have been measured continuously by the eddy covariance approach from June 2013 to December 2016 in a riparian forest, which is a primary body of natural oases located within the lower reaches of inland rivers in China. The present results revealed that the climatic conditions characterized by relatively high mean air temperatures (T_a) with fluctuating annual precipitation (P) during the prescribed study periods were comparable to the historical mean value. The annual net ecosystem productivity (NEP) ranged from approximately 278 g C m⁻² year⁻¹ to 427 g C m⁻² year⁻¹, with a mean value of 334 g C m⁻² year⁻¹. The mean annual ecosystem respiration (Re) and the gross primary productivity (GPP) were found to be 558 and 892 g C m⁻² year⁻¹, respectively. The results also ascertained that the high inter-annual variations in NEP were attributable to Re rather than to GPP, and this result was driven primarily by T_a and the groundwater depth under similar eco-physiological processes. In addition, the CO₂ fluxes were also strongly correlated with the soil temperature and photosynthetically active radiation for the present study site. In conclusion, the desert riparian forest is a considerably significant carbon sink, particularly in the hyper-arid regions. Full article

Forest managers are often required to restore forest stands following natural disturbances, a situation that may become more common and more challenging under global change. In parts of Central Europe, particularly in mountain regions dominated by mixed temperate forests, the use of relatively low intensity, uneven-aged silviculture is a common management approach. Because this type of management is based on mimicking less intense disturbances, the restoration of more severe disturbance patches within forested landscapes has received little attention. The goal of this paper is to synthesize research on the restoration of forests damaged by disturbances in temperate forests of Slovenia and neighbouring regions of Central Europe, where uneven-aged silviculture is practiced. Research indicates that active management aimed at favouring mixed uneven-aged forest reduces the risk of disturbance and improves the resilience of stands. Salvage logging may have positive or negative effects on regeneration, much of which is due to the method applied and the quality of work. The most prominent factors that negatively affect restoration are: lack of advanced regeneration and decomposed woody debris, high altitude, steep slopes, dense ground vegetation, and overbrowsing. Planting or sowing should be applied in post-disturbance forests where many negative factors interact and where a high demand for sustainability of forest ecosystem services is present. Full article

Improved understanding of climate-growth relationships of multiple species is fundamental to understanding and predicting the response of forest growth to future climate change. Forests are mainly composed of conifers in Northwestern Yunnan Plateau, but variations of growth response to climate conditions among the species are not well understood. To detect the growth response of multiple species to climate change, we developed residual chronologies of four major conifers, i.e., George’s fir (Abies georgei Orr), Likiang spruce (Picea likiangensis (Franch.) E.Pritz.), Gaoshan pine (Pinus densata Mast.) and Chinese larch (Larix potaninii Batalin) at the upper distributional limits in Shika Snow Mountain. Using the dendroclimatology method, we analyzed correlations between the residual chronologies and climate variables. The results showed that conifer radial growth was influenced by both temperature and precipitation in Shika Snow Mountain. Previous November temperature, previous July temperature, and current May precipitation were the common climatic factors that had consistent influences on radial growth of the four species. Temperature in the previous post-growing season (September–October) and moisture conditions in the current growing season (June–August) were the common climatic factors that had divergent impacts on the radial growth of the four species. Based on the predictions of climate models and our understanding of the growth response of four species to climate variables, we may understand the growth response to climate change at the species level. It is difficult to predict future forest growth in the study area, since future climate change might cause both increases and decreases for the four species and indirect effects of climate change on forests should be considered. Full article