Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), one of the most commercially important tree species in western North America and one of the most valuable timber trees worldwide, was introduced to Europe in 1827. It became a major species for afforestation in Western Europe after WWII, currently grows in 35 countries on over 0.83 million ha and is one of the most widespread non-native tree species across the continent. A lower sensitivity to drought makes Douglas-fir a potential alternative to the more drought-sensitive Norway spruce so its importance in Europe is expected to increase in the future. It is one of the fastest growing conifer species cultivated in Europe, with the largest reported dimensions of 2.3 m in diameter and 67.5 m in height. Pure stands have high productivity (up to 20 m3 ha−1a−1) and production (over 1000 m3 ha−1). The species is generally regenerated by planting (initial stocking density from less than 1000 seedlings ha−1 to more than 4000 ha−1), using seedlings of European provenance derived from seed orchards or certified seed stands. As the range of end-uses of its wood is very wide, the rotation period of Douglas-fir is highly variable and ranges between 40 and 120 years. When the production of large-sized, knot-free timber is targeted, thinnings are always coupled with pruning up to 6 m. There is an increasing interest in growing Douglas-fir in mixtures and managing stands through close-to-nature silviculture, but the species’ intermediate shade tolerance means that it is best managed through group selection or shelterwood systems.
Forest plays a vital role in the global biogeochemical cycles through a high rate of carbon sequestration and harboring biodiversity. However, local species diversity is declining while also becoming increasingly homogenized across communities. Although effects of local biotic processes (e.g., species α-diversity and stand structural heterogeneity) and environmental factors on aboveground biomass (AGB) have been widely tested, there is a huge knowledge gap for the effect of regional biotic processes (i.e., taxonomic and functional β-diversity) in forests. Here, we hypothesized that regional and local environmental factors along with biotic processes jointly regulate AGB through species shifts in tropical forests. Using piecewise structural equation modeling (pSEM), we linked climatic water availability, soil fertility, stand structural heterogeneity (either tree DBH inequality, height inequality, or stand density), species α-diversity, taxonomic or functional β-diversity (and its two components; β-turnover and β-richness), and AGB across 189 inventory plots in tropical forests of Sri Lanka. Soil fertility and climatic water availability shaped local and regional biotic processes. Stand structural heterogeneity promoted species α-diversity but declined β-diversity (but increased β-taxonomic turnover). Species α-diversity and stand structural heterogeneity promoted AGB whereas taxonomic and functional β-diversity declined (but β-taxonomic turnover increased) AGB. The relationships of AGB with species α-diversity and β-diversity varied from significant to nonsignificant positive depending on the specific combinations of stand structural heterogeneity metrics used. This study shows that local biotic processes could increase AGB due to the local and regional niche complementarity effect whereas the regional biotic processes could restrict AGB due to the regional selection or functional redundancy effect under favorable environmental conditions. We argue that biotic homogenization, as well as drought conditions, may have strong divergent impacts on forest functions and that the impacts of tree diversity loss may greatly reduce carbon sequestration.
Subcanopy tree species are an important component of temperate secondary forests. However, their biomass equations are rarely reported, which forms a “vertical gap” between canopy tree species and understory shrub species. In this study, we destructively sampled six common subcanopy species (Syringa reticulate var. amurensis (Rupr.) Pringle, Padus racemosa (Lam.) Gilib., Acer ginnala Maxim., Malus baccata (Linn.) Borkh., Rhamnus davurica Pall., and Maackia amurensis Rupr. et Maxim.) to establish biomass equations in a temperate forest of Northeast China. The mixed-species and species-specific biomass allometric equations were well fitted against diameter at breast height (DBH). Adding tree height (H) as the second predictor increased the R 2 of the models compared with the DBH-only models by –1% to + 3%. The R 2 of DBH-only and DBH-H equations for the total biomass of mixed-species were 0.985 and 0.986, respectively. On average, the biomass allocation proportions for the six species were in the order of stem (45.5%) > branch (30.1%) > belowground (19.5%) > foliage (4.9%), with a mean root: shoot ratio of 0.24. Biomass allocation to each specific component differed among species, which affected the performance of the mixed-species model for particular biomass component. When estimating the biomass of subcanopy species using the equations for canopy species (e.g., Betula platyphylla Suk., Ulmus davidiana var. japonica (Rehd.) Nakai, and Acer mono Maxim.), the errors in individual biomass estimation increased with tree size (up to 68.8% at 30 cm DBH), and the errors in stand biomass estimation (up to 19.2%) increased with increasing percentage of basal area shared by subcanopy species. The errors caused by selecting such inappropriate models could be removed by multiplying adjustment factors, which were usually power functions of DBH for biomass components. These results provide methodological support for accurate biomass estimation in temperate China and useful guidelines for biomass estimation for subcanopy species in other regions, which can help to improve estimates of forest biomass and carbon stocks.
Non-photosynthetic components within a forest ecosystem account for a large proportion of the canopy but are not involved in photosynthesis. Therefore, the accuracy of gross primary production (GPP) estimates is expected to improve by removing these components. However, their influence in GPP estimations has not been quantitatively evaluated for deciduous forests. Several vegetation indices have been used recently to estimate the fraction of photosynthetically active radiation absorbed by photosynthetic components (
Homeostasis is the adaptability of a species to a changing environment. However, the ecological stoichiometric homeostasis of Robinia pseudoacacia L. in different climatic regions is poorly understood but could provide insights into its adaptability in the loess hilly region. This study sampled 20 year-old R. pseudoacacia plantations at 10 sites along a north–south transect on the Loess Plateau. Variations in the ecological stoichiometric characteristics of leaf and soil carbon, nitrogen, and phosphorus were analysed and homeostatic characteristics of leaf ecological stoichiometric parameters in different climates were identified. Factors affecting leaf stoichiometry were assessed. The results show that R. pseudoacacia leaves were rich in nitrogen and deficient in phosphorous during tree growth and development. Nitrogen and phosphorous levels in the soils of the loess region were lower than the average in soils in the rest of China. All ecological stoichiometric parameters of R. pseudoacacia leaves in two different climates were considered “strictly homeostasis”. Precipitation, available phosphorus, and soil C:P were the main factors affecting the variation of C:N:P stoichiometry of R. pseudoacacia leaves. R. pseudoacacia in the loess hilly region has strong ecologically homeostatic characteristics and suggests that it is well-adapted to the area.
Nitrogen deposition has a considerable impact on biogeochemical cycling in terrestrial ecosystems. However, how litter production and element return respond to N addition remains poorly understood in nitrogen-rich subtropical regions. In this study, a 4-year nitrogen addition experiment explored its effects on foliar litter production and carbon, nitrogen and phosphorus in a subtropical Michelia wilsonii forest. A clear seasonal pattern in foliar litterfall was observed, regardless of nitrogen treatments, with a peak in spring and a smaller one in autumn. Foliar litter increased with increasing nitrogen but did not affect litter carbon concentrations and often decreased nitrogen and phosphorous concentrations. The effect of nitrogen addition was dependent on time (month/year). Carbon, nitrogen and phosphorous return showed similar bimodal seasonal patterns. Nitrogen addition increased carbon and nitrogen return but did not affect phosphorous. Our results suggest that the addition of nitrogen stimulates carbon and nutrient return via litterfall.
Research on the spatial patterns of tree populations is critical for understanding the structure and dynamic processes of forests. However, little is known about how the underlying drivers shape these patterns and species interactions in forest systems. In this study, spatial point pattern analysis investigated the combined effects of intraspecific interactions and environmental heterogeneity on the spatial structure and internal maintenance mechanisms of Picea crassifolia in the Qilian Mountain National Nature Reserve, China. Data were obtained from a 10.2-ha dynamic monitoring plot (DMP) and sixteen 0.04-ha elevation gradient plots (EGPs). Under complete spatial randomness, both mature trees and saplings in the DMP demonstrated large-scale aggregation with negative correlations. In EGPs, saplings were clustered in small mesoscales, mature trees were randomly distributed, and the interactions of saplings-trees at all elevations were not correlated. By eliminating the interference of environmental heterogeneity through the inhomogeneous Poisson process, saplings in the DMP and EGPs were clustered in small scales and trees randomly distributed. Intraspecific associations were negatively correlated, in the DMP and at low elevations, and no correlations in high elevations of EGPs. In the vertical scale, saplings showed a small-scale aggregation pattern with increase in elevation, and the aggregation degree first decreased and then increased. The interactions of saplings-trees and saplings–saplings showed inhibitions at small scales, with the degree of inhibition gradually decreasing. Spatial patterns and associations of adults–adults did not change significantly. The results revealed that intraspecific interactions and environmental heterogeneity regulated the spatial patterns of P. crassifolia at small and large scales, respectively. Environmental heterogeneity might be the most decisive factor affecting the spatial patterns of saplings, while trees were more affected by intraspecific interactions. Moreover, competition between trees in this area could be more common than facilitation for the growth and development of individuals.
Considerable economic losses and ecological damage can be caused by forest fires, and compared to suppression, prevention is a much smarter strategy. Accordingly, this study focuses on developing a novel framework to assess forest fire risks and policy decisions on forest fire management in China. This framework integrated deep learning algorithms, geographic information, and multisource data. Compared to conventional approaches, our framework featured timesaving, easy implementation, and importantly, the use of deep learning that vividly integrates various factors from the environment and human activities. Information on 96,594 forest fire points from 2001 to 2019 was collected on Moderate Resolution Imaging Spectroradiometer (MODIS) fire hotspots from 2001 to 2019 from NASA's Fire Information Resource Management System. The information was classified into factors such as topography, climate, vegetation, and society. The prediction of forest fire risk was generated using a fully connected network model, and spatial autocorrelation used to analyze the spatial aggregation correlation of active fire hotspots in the whole area of China. The results show that high accuracy prediction of fire risks was achieved (accuracy 87.4%, positive predictive value 87.1%, sensitivity 88.9%, area under curve (AUC) 94.1%). Based on this, it was found that Chinese forest fire risk shows significant autocorrelation and agglomeration both in seasons and regions. For example, forest fire risk usually raises dramatically in spring and winter, and decreases in autumn and summer. Compared to the national average, Yunnan Province, Guangdong Province, and the Greater Hinggan Mountains region of Heilongjiang Province have higher fire risks. In contrast, a large region in central China has been recognized as having a long-term, low risk of forest fires. All forest risks in each region were recorded into the database and could contribute to the forest fire prevention. The successful assessment of forest fire risks in this study provides a comprehensive knowledge of fire risks in China over the last 20 years. Deep learning showed its advantage in integrating multiple factors in predicting forest fire risks. This technical framework is expected to be a feasible evaluation tool for the occurrence of forest fires in China.
Thinning is a widely used forest management tool but systematic research has not been carried out to verify its effects on carbon storage and plant diversity at the ecosystem level. In this study, the effect of thinning was assessed across seven thinning intensities (0, 10, 15, 20, 25, 30 and 35%) in a low-quality secondary forest in NE China over a ten-year period. Thinning affected the carbon storage of trees, and shrub, herb, and soil layers (P < 0.05). It first increased and then decreased as thinning intensity increased, reaching its maximum at 30% thinning. Carbon storage of the soil accounted for more than 64% of the total carbon stored in the ecosystem. It was highest in the upper 20-cm soil layer. Thinning increased tree species diversity while decreasing shrub and herb diversities (P < 0.05). Redundancy analysis and a correlation heat map showed that carbon storage of tree and shrub layers was positively correlated with tree diversity but negatively with herb diversity, indicating that the increase in tree diversity increased the carbon storage of natural forest ecosystems. Although thinning decreased shrub and herb diversities, it increased the carbon storage of the overall ecosystem and tree species diversity of secondary forest. Maximum carbon storage and the highest tree diversity were observed at a thinning intensity of 30%. This study provides evidence for the ecological management of natural and secondary forests and improvement of ecosystem carbon sinks and biodiversity.
To explore how to respond to seasonal freeze–thaw cycles on forest ecosystems in the context of climate change through thinning, we assessed the potential impact of thinning intensity on carbon cycle dynamics. By varying the number of temperature cycles, the effects of various thinning intensities in four seasons. The rate of mass, litter organic carbon, and soil organic carbon (SOC) loss in response to temperature variations was examined in two degrees of decomposition. The unfrozen season had the highest decomposition rate of litter, followed by the frozen season. Semi-decomposed litter had a higher decomposition rate than undecomposed litter. The decomposition rate of litter was the highest when the thinning intensity was 10%, while the litter and SOC were low. Forest litter had a good carbon sequestration impact in the unfrozen and freeze–thaw seasons, while the converse was confirmed in the frozen and thaw seasons. The best carbon sequestration impact was identified in litter, and soil layers under a 20–25% thinning intensity, and the influence of undecomposed litter on SOC was more noticeable than that of semi-decomposed litter. Both litter and soil can store carbon: however, carbon is transported from undecomposed litter to semi-decomposed litter and to the soil over time. In summary, the best thinning intensity being 20–25%.
The CO2 efflux of branches and leaves plays an important role in ecosystem carbon balance. Using a carbon flux system, the efflux of Larix gmelinii var. principis-rupprechtii (Dahurian larch) was investigated in 27 years (immature), 31 years (near-mature), and 47 years (mature) stands at diurnal, seasonal, and spatial scales (direction and height) as well as its connection with environmental factors from May to October 2020. Diurnal variation in efflux was a single peak, and the maximum occurring between 14:00 and 16:00. Seasonal variation also exhibited a single peak, with the maximum in late July and the minimum in early October. From May to September, efflux on the south side was the largest among the three stands, and mean values on the south side of 27 year-old, 31 year-old, and 47 year-old trees were 0.50, 0.97 and 1.05 μmol·m–2·s–1, respectively. The minimum occurred on the north side. Except for the maximum in July and September in the 27 year-old stand in the middle of the canopy, the maximum efflux in the upper canopy, and the means in the 27 year-old, 31 year-old, and 47 year-old stands were 0.49, 0.96 and 1.04 μmol·m–2·s–1, respectively; the minimum occurred in the lower canopy. Temperatures and relative humidity influenced seasonal variations in efflux. Seasonal variation in temperature sensitivity coefficient (Q10) was opposite that of temperature, increasing with decreasing temperature. At the spatial scale, maximum Q10 occurred in the mid canopy. With the efflux and temperature data in different locations, it is possible to better estimate efflux variations in each stand.
Urban parks are an important part of urban ecosystems and play an important role in biodiversity conservation. However, it is still unclear how park characteristics affect plant diversity which could hinder the conservation of urban biodiversity due to the ineffective design of urban parks. The diversity of woody plants in 33 parks of Changchun, China, was measured with plot measurements and linked with urban park characteristics (e.g., size and age of the park) to uncover the relationship between them. The results show that urban woody plant species were abundant, with 98 species belonging to 51 genera and 26 families in the snow climate city of Changchun. The variation in woody plant diversity was largely explained by internal patch characteristics (e.g., size, age, shape), and external factors surrounding the park (e.g., land use type and socioeconomic level) accounted for only 16.0% in our study. For internal patch characteristics, older urban parks with larger areas demonstrated a richer level of plant diversity and increased nonlinearly with increasing park area. The threshold size significantly affecting plant diversity variation was approximately 30 ha. Plant diversity had positive linear relationships with the ages of urban parks, supporting the legacy effect. In addition, woody plant diversity nonlinearly decreased with increasing park shape index, which suggested that the plant diversity could also be increased by optimizing the park shape. Regarding the external factors surrounding parks, the spatial distribution of woody plant diversity varied greatly from the urban center to the suburbs. House prices around the park had positive linear relationships with woody plant diversity in parks, supporting the luxury effect. However, building and road proportions, and green space proportion had no relationship with plant diversity in parks. This study can provide a robust reference for enriching plant diversity in urban parks, thus improving the development of urban sustainable cities.
Beech stands are considered part of the ancient forest ecosystems in the northern hemisphere. In mixed stands in beach forest ecosystems, the type of associated tree species can significantly affect soil functions, but their influence on microbial activity, nutrient cycling and belowground properties is unknown. Here, we considered forest patches in northern Iran that are dominated by different tree species: Fagus orientalis Lipsky, Quercus castaneifolia C. A. Mey., Pterocarya fraxinifolia (Lam.), Tilia begonifolia Stev., Zelkova carpinifolia Dippe, Acer cappadocicum Gled, Acer velutinum Boiss., Fraxinus excelsior L., Carpinus betulus L., and Alnus subcordata C. A. Mey. For each forest patch–tree species, litter and soil samples (25× 25 × 10 cm, 100 of each) were analyzed for determine soil and litter properties and their relationship with tree species. The litter decomposition rate during a 1-year experiment was also determined. A PCA showed a clear difference between selected litter and soil characteristics among tree species. F. orientalis, Q. castaneifolia, P. fraxinifolia, T. begonifolia, Z. carpinifolia, A. cappadocicum, and A. velutinum enhanced soil microbial biomass of carbon, whereas patches with F. excelsior, C. betulus and A. subcordata had faster litter decomposition and enhanced biotic activities and C and N dynamics. Thus, soil function indicators were species-specific in the mixed beech forest. A. subcordata (a N-fixing species), C. betulus and F. excelsior were main drivers of microbial activities related to nutrient cycling in the old-growth beech forest.
Warming and nitrogen (N) deposition are two important drivers of global climate changes. Coarse woody debris (CWD) contains a large proportion of the carbon (C) in the total global C pool. The composition of soil microbial communities and environmental changes (i.e., N deposition and warming) are the key drivers of CWD decomposition, but the interactive impact between N deposition and warming on the composition of soil microbial communities and CWD decomposition is still unclear. In a laboratory experiment, we study and simulate respiration during decomposition of the CWD (C98) of Cryptomeria japonica (CR) and Platycarya strobilacea (PL) in response to warming and N deposition over 98 days. Resuts show that either warming or N addition significantly accelerated the C98 of the two tree species by altering the soil microbial community (bacterial:fungi and G+:G–). The combined treatment (warming + N) resulted in a decomposition effect equal to the sum of the individual effects. In addition, the species composition of bacteria and fungi was obviously affected by warming. However, N deposition had a remarkable influence on G+:G–. Our results indicated that N deposition and warming will observably alter the composition and growth of the microbial community and thus work synergistically to accelerate CWD decomposition in forest ecosystems. We also present evidence that N deposition and warming influenced the composition and balance of soil microbial communities and biogeochemical cycling of forest ecosystems.
Research has indicated that introducing Aralia elata into larch plantations forms an agroforestry system which could provide economic benefits for local farmers and improve degraded soils. However, the impact of litter mixtures on soil chemical and microbial properties in this agroforestry system are unclear, which limits efficient management of the agroforestry system. A 365-d incubation experiment examined the effect of litter mixtures of different proportions of larch (L) and A. elata (A) on soil chemical and microbial properties. The results show that levels of mineral N, available P, microbial biomass carbon and nitrogen, cumulative C mineralization, and activities of hydrolases and oxidases increased with an increase of A. elata in the litter mixtures. Concentration of total soil carbon, nitrogen, and phosphorous did not change (except for total nitrogen). Compared with larch litter alone, levels of mineral N, available P, microbial biomass carbon and nitrogen, cumulative C mineralization, and the activities of hydrolases and oxidases increased by 7.6–433.5%. Most chemical and microbial properties were positively correlated with mixed litter proportions and the initial levels of N, P, K, Ca, Mg, Mn, Zn and Cu in the litter, while negatively correlated with the initial concentrations of C, Fe and lignin, C/N and lignin/N ratios. The results indicate that A. elata litter can improve degraded larch soil and the degree depends on the proportion of A. elata litter in the litter mixtures.
Climate change can intensify drought in many regions of the world and lead to more frequent drought events or altered cycles of soil water status. Therefore, it is important to enhance the tolerance to drought and thus health, vigor, and success of transplantation seedlings used in the forestry by modifying fertilization and promoting mycorrhization. Here, we sowed seeds of Japanese larch (Larix kaempferi) in 0.2-L containers with 0.5 g (low fertilization; LF) or 2 g (high fertilization; HF) of slow-release fertilizer early in the growing season. One month later, we irrigated seedlings with non-sterilized ectomycorrhizal inoculum (ECM) or sterilized solution (non-ECM), and after about 2 months, plants were either kept well watered (WW; 500 mL water/plant/week) or subjected to drought (DR; 50 mL water per plant/week) until the end of the growing season. HF largely stimulated plant growth and above- and belowground biomass production, effects that are of practical significance, but caused a small decrease in stomatal conductance (Gs390) and transpiration rate (E 390), which in practice is insignificant. ECM treatment resulted in moderate inhibition of seedling growth and biomass and largely canceled out the enhancement of biomass and foliar K content by HF. DR caused a large decrease in CO2 assimilation, and enhanced stomatal closure and induced senescence. DR also largely depleted foliar Mg and enriched foliar K. Although DR caused a large decrease in foliar P content in LF, it moderately increased P in HF. Likewise, DR increased foliar K in HF but not in LF, and decreased foliar P in ECM plants but not in non-ECM plants. Conversely, ECM plants exhibited a large enrichment in foliar P under WW and had a lower water potential under DR when grown in LF. These results indicate that the drought tolerance and health and vigor of Japanese larch seedlings can be modified by soil fertility and soil microorganisms. This study provides a basis for new multifactorial research programs aimed at producing seedlings of superior quality for forestation under climate change.
As a dynamic ex situ conservation strategy, a clonal seed orchard was started in a nursery in Pomaio (POM) in central Italy in 1993 for an assisted migration experiment of Abies nebrodensis (Lojac.) Mattei. Two artificial ex situ populations were planted with this gene pool: a seedling arboretum in Pieve Santo Stefano (PSS) and a small dendrological collection in Papiano (PAP), both originating from the Sicilian relict population. Here, using AFLP markers, we estimated the relatedness among the relocated genotypes of the three collections to check whether the three collections had sufficient genetic variability to be considered as additional sources of variability to the original gene pool for the assisted migration strategy. High individual genetic variability was found in the collections; each plant had a different genotype and was confirmed to belong to its population of origin. PAP and PSS trees were shown to be only from the original population of A. nebrodensis species and were derived from a limited set of maternal fertile genotypes. Based on the Sicilian fir population inventory, nursery production in Sicily, and structure clustering analysis, close genetic relationships among POM, PAP and several PSS trees (1–35) were evident. Similarly, the PSS group (36–78) was genetically close to tree 1 of POM and in a lesser proportion to plants 7 and 9 of POM. The sampling of seedlings used to form batches in the nursery might have influenced the structure of the resultant plantations. All genotypes will be useful for enriching the original gene pool.
Plant phenotypes are influenced by genetic and environmental factors. In this study, the growth traits of 43 one-year-old poplar clones grown at different sites in northeast China (Dongling State-owned Forest Protection Center, DL; Baicheng State-owned forest farm, BC; and Cuohai Forest farm, CH) were evaluated and analyzed across clones and sites. Results show significant differences in height and base diameter among sites and clones. Phenotypic and genetic variation coefficients ranged from 49.59% (BC) to 58.39% (DL) and from 49.33% (BC) to 58.06% (DL), respectively. Additive main effects and multiplicative interaction (AMMI) analysis showed that the effects of genotype, environment, and genotype ×environment interaction were significantly different. Genetic variation was the main source of variation, accounting for 48.6%. AMMI biplot showed that clone 30 had high and stable yields at the three sites. From an evaluation of multiple traits and GGE biplot that clone 2, clone 30 and clone 25 had higher yield than the other clones at DL, CH and BC, respectively. These clones will provide material for forest regeneration in northeast China.
Sesquiterpenes are the major pharmacodynamic components of agarwood, a precious traditional Chinese medicine obtained from the resinous portions of Aquilaria sinensis trees that form in response to environmental stressors. To characterize the sesquiterpene synthases responsible for sesquiterpene production in A. sinensis, a bioinformatics analysis of the genome of A. sinensis identified six new terpene synthase genes, and 16 sesquiterpene synthase genes were identified as type TPS-a in a phylogenetic analysis. The expression patterns for eight of the sesquiterpene synthase genes after treatment with various hormones or hydrogen peroxide were analyzed by real-time quantitative PCR. The results suggest that 100 μM methyl jasmonate, ethephon, ( ±)-abscisic acid or hydrogen peroxide could be effective short-term effectors to increase the expression of sesquiterpene synthase genes, while 1 mM methyl salicylate may have long-term effects on increasing the expression of specific sesquiterpene synthase genes (e.g., As-SesTPS, AsVS, AsTPS12 and AsTPS29). The expression changes in these genes under various conditions reflected their specific roles during abiotic or biotic stresses. Heterologous expression of a novel A. sinensis sesquiterpene synthase gene, AsTPS2, in Escherichia coli produced a major humulene product, so AsTPS2 is renamed AsHS1. AsHS1 is different from ASS1, AsSesTPS, and AsVS, for mainly producing α-humulene. Based on the predicted space conformation of the AsHS1 model, the small ligand molecule may bind to the free amino acid by hydrogen bonding for the catalytic function of the enzyme, while the substrate farnesyl diphosphate (FPP) probably binds to the free amino acid on one side of the RxR motif. Arg450, Asp453, Asp454, Thr457, and Glu461 from the NSE/DTE motif and D307 and D311 from the DDxxD motif were found to form a polar interaction with two Mg2+ clusters by docking. The Mg2+-bound DDxxD and NSE/DTE motifs and the free RXR motif are jointly directed into the catalytic pocket of AsHS1. Comparison of the tertiary structural models of AsHS1 with ASS1 showed that they differed in structures in several positions, such as surrounding the secondary catalytic pocket, which may lead to differences in catalytic products. Based on the results, biosynthetic pathways for specific sesquiterpenes such as α-humulene in A. sinensis are proposed. This study provides novel insights into the functions of the sesquiterpene synthases of A. sinensis and enriches knowledge on agarwood formation.
The Asian longhorned beetle (ALB), Anoplophora glabripennis, is a well-known stem borer with high polyphagous properties causing frequent outbreaks in northeast China. An attractant-based trap is needed to improve the sensitivity, reliability, and efficiency for detection of the beetle. In this study, the effects of attractants, trap types and color synergy of a trapping system were evaluated. Attractant blends comprised of the male-produced, two-component pheromone plus plant volatiles were used in the field in Hengshui city. Plant volatiles (e.g., 1-pentanol, and 2-pentanol) in combination with male pheromones increased the mean number of trapped ALB compared to the pheromone alone. Males responded better than females to traps baited with plant volatiles alone, whereas traps emitting plant volatiles plus pheromone, regardless of trap type, captured more females than males. The ALB-trapping efficiency of a modified flight intercept panel trap was more than ten times as high as a woodborer panel trap and 1.2 times a flight intercept panel trap. The 1-pentanol and 2-pentanol attractants alone or in combination with male-produced pheromone were more effective for monitoring ALB than common lures. In laboratory Y-tube olfactometer experiments, the color brown was better at increasing attraction of both males and females to 1-pentanol, 2-pentanol, 1-pentanol + pheromone, and 2-pentanol + pheromone compared to the clear-glass control arm. The findings provide a reliable and effective trap system to monitor ALB infestations.
The comprehensive utilization of wood is the main goal of log cutting, but knot defects increase the difficulty of rationally optimizing cutting. Due to the lack of real shape data of knot defects in logs, it is difficult for detection methods to establish a correlation between signal and defect morphology. An image-processing method is proposed for knot inversion based on distance regularized level set segmentation (DRLSE) and spatial vertex clustering, and with the inversion of the defects existing relative board position in the log, an inversion model of the knot defect is established. First, the defect edges of the top and bottom images of the boards are extracted by DRLSE and ellipse fitting, and the major axes of the ellipses made coplanar by angle correction; second, the coordinate points of the top and bottom ellipse edges are extracted to form a spatial straight line; third, to solve the intersection dispersion of spatial straight lines and the major axis plane, K-medoids clustering is used to locate the vertex. Finally, with the vertex and the large ellipse, a 3D cone model is constructed which can be used to invert the shape of knots in the board. The experiment was conducted on ten defective larch boards, and the experimental results showed that this method can accurately invert the shapes of defects in solid wood boards with the advantages of low cost and easy operation.
As the COVID-19 pandemic unfolded, questions arose as to whether the pandemic would amplify or pacify tropical deforestation. Early reports warned of increased deforestation rates; however, these studies were limited to a few months in 2020 or to selected regions. To better understand how the pandemic influenced tropical deforestation globally, this study used historical deforestation data (2004–2019) from the Terra-i pantropical land cover change monitoring system to project expected deforestation trends for 2020, which were used to determine whether observed deforestation deviated from expected trajectories after the first COVID-19 cases were reported. Time series analyses were conducted at the regional level for the Americas, Africa and Asia and at the country level for Brazil, Colombia, Peru, the Democratic Republic of Congo and Indonesia. Our results suggest that the pandemic did not alter the course of deforestation trends in some countries (e.g., Brazil, Indonesia), while it did in others (e.g., Peru). We posit the importance of monitoring the long-term effects of the pandemic on deforestation trends as countries prioritize economic recovery in the aftermath of the pandemic.
Ground-level ozone pollution is a menace for vegetation in the northern hemisphere, limiting photosynthetic pigments and suppressing photosynthesis in trees and other types of plants. Phaeophytinization is the process of converting chlorophylls into phaeophytins, for example by acidification. Ozone is a highly oxidizing molecule and well known to degrade chlorophylls; however, the effect of ozone on phaeophytinization in leaves of higher plants is largely unknown. To reveal ozone effect on phaeophytinization and evaluate the potential of phaeophytinization as an index of ozone stress in trees, the absorbance at the optical density of 665 nm was measured before (OD665) and after (OD665a) acidification in three independent experiments with nearly 30 conditions of ozone exposure. Both current ambient and elevated ozone widely affected phaeophytinization, as indicated by decreases or increases in the phaeophytinization quotient OD665/OD665a. These effects were commonly moderate to large in magnitude and practically significant, and occurred even in ozone-asymptomatic leaves. It emerges that the ozone effect on phaeophytinization is bimodal, likely depending on the intensity of ozone stress. These results indicate a promising feature of OD665/OD665a as a thorough index of ozone stress in the future, but further studies are needed to reveal the underlying biochemical mechanisms of the bimodal effect on phaeophytinization.
Innovation in forestry education is needed to address changing contexts of the positionality of forests. This is particularly significant in the Asia–Pacific region, where deforestation and degradation are high. However, the accessibility of high-quality forestry education to address changing regional and global contexts is lacking. A series of innovative sustainable forest management (SFM) open education resource (OER) courses were developed and implemented to improve the accessibility of SFM education to enhance teaching quality, curriculum, and research capacity of universities in the Asia-Pacific Region. To evaluate the SFM-OER program in terms of student experiences, this study investigated student achievement, perceived success of the pedagogical approach and instructional design, and perceived effectiveness of the learning activities in promoting active and transformative learning through the assessment of a 1,191-course feedback survey between 2018 and 2020, including the global pandemic. This study revealed that the program attracted diverse student demographics, including a higher proportion of female students majoring in forestry, ecology, and other environmental studies. Their primary motivation to participate in the courses was to gain international experience, followed by the flexibility of online learning, mandatory course requirements, and earning course credits. Students were satisfied with the Canvas learning management system. Most students spent less than 5 to 10 h of their weekly time in the course and agreed or strongly agreed that the workloads were manageable. Students reflected positively on various learning activities and assignments, such as watching lecture videos, taking quizzes, reading and summarizing, having discussions, and peer review writing. However, they did not clearly prefer specific learning activities, signifying the importance of using diverse learning activities to satisfy diverse individual learning styles in online settings. This analysis contributes to the further development of student-centered pedagogical development for online learning and provides insight into the ways forward for online higher forestry education, while repurposing existing OER courses in a post-Covid-19 era.
