Objective: This study aims to systematically analyze the effects of initial planting density, site conditions, and thinning treatments on forest maturity age, clarifying the effects of thinning on the stand volume, net present value (NPV) and saw log production of Pinus sylvestris var. mongolica (Mongolian pine) plantations, so as to provide science-based guidelines for the management of Mongolian pine plantations. Method: Based on the fixed plot data of Mongolian pine, the study first developed a set of growth and harvesting models of Mongolian pine including individual tree diameter growth model and mortality model, height curve model, site index model, maximum-size density line coupled with taper equation, and then integrated them into a stand growth simulator. With the annual average volume, annual average large diameter timber volume, and maximum NPV as the criteria for quantitative maturity, technical maturity, and economic maturity, respectively, the simulator was used to simulate forest growth, and compare the quantitative, technical and economic maturity age (rotation length) of the plantations and the corresponding stand volume, NPV, and large diameter timber at mature stage under different thinning schedules. Result: The simulator was able to accurately simulate the development and thinning of Mongolian pine plantations, with an average relative error of 5% between the simulated values and the measured values of the sample plots. Under natural growth conditions, the quantitative maturity age of the stands at two initial planting densities (3 300 and 2 500 plants·hm^?2) was 44?45 a at SI = 15 m, 38?42 a at SI = 18 m, and 36?40 a at SI = 21 m. The economic maturity age at a discount rate of 3% was 50?54 a at SI = 15 m, 44?43 a at SI = 18 m, and 39?40 a at SI = 21 m. The quantity and economic maturity advanced with the improvement of site quality and the increase of initial planting density, but did not reach technical maturity within 80 years. For stands with medium-to-high site quality, light and moderate thinning delayed both quantitative maturity and economic maturity. The mean annual volume increment of the stands reached 91%–104% of that of unthinned stands at quantitative maturity, the total net present value (NPV) increased to 113%–141% of that of unthinned stands at economic maturity, and the production of large diameter timber advanced. Under severe thinning, the technical maturity for large-diameter timber was advanced to 60–65 years, with the mean annual volume of large-diameter timber at maturity reaching 106%–173% of that in unthinned stands at 80 years. Under this intensity, economic maturity was delayed by 4–7 years, with NPV at maturity being 102%–132% of unthinned stands. Under this intensity of thinning, the quantitative maturity in the stands with high initial planting density was delayed, while that with low initial density was advanced, yet the total stand volume at maturity was only 74%–89% of that of unthinned stands. When the residual stand reached quantitative maturity (their growth potential was fully realized), the mean annual increment volume of the stand was 93%–95% of that of unthinned stands, and the total stand volume recovered to 92%–128%. In contrast, for low-quality sites, after light and moderate thinning, the average annual volume growth of the stand at quantitative mature was 80% to 97% of the unthinned stand, and the NPV of the stand at economic mature was 94% to 107% of that of the unthinned stand. Although severe thinning advanced technical maturity to less than 60 years, the mean annual yield of large-diameter timber at maturity was only 45%–64% of unthinned stands at 80 years. Even when the residual stand reached quantitative maturity, the total stand volume was only 52%–61% of unthinned stands. Moreover, severe thinning on poor sites resulted in 50%–56% lower total stand volume at quantitative maturity and 18%–33% lower economic returns at economic maturity. Therefore, when large-diameter timber production is the management objective, mid-to-high site quality stands should be selected for moderate-to-severe thinning treatments. Particularly under heavy thinning regimes, close monitoring of the residual stands’ quantitative maturity age is essential to fully realize their productivity potential. Conclusion: In the context of efficient cultivation of plantation and construction of reserve forests, it is necessary to explore forest maturity under different thinning schedules based on simulation optimization technology, which can effectively improve stand volume, large diameter timber yield, and economic benefits.

Objective: Through integrating site factors, forest age, and stand density effects, a growth model of arbor carbon storage in typical forest stands in the mid-subtropical zone of China was constructed to accurately analyze growth dynamics in stand carbon storage, providing guidance for estimating forest carbon sequestration potential. Method: This study focused on typical forest types in the mid-subtropical zone of China. The survey data from 30 700 permanent forest plots in three continuous national forest inventories were collected. A site classification algorithm based on stand mean height growth was employed to categorize site class. With the stand mean age, site class, and stand density index as explanatory variables, stand carbon storage growth models were constructed under different forest origins (natural vs. planted) by region and dominant tree species (groups). The study further analyzed the growth dynamics of stand carbon storage. Result: 1) All mean height growth models for mid-subtropical forest stands achieved excellent goodness-of-fit, with R²≥0.931. The total height growth had a positive correlation with site class. The cumulative height growth across five site classes followed an approximately arithmetic sequence, indicating effective classification. 2) The stand carbon storage growth models based on site class, stand mean age and stand density index all reached satisfactory predictive accuracy (R²≥0.633). The model performance for different forest origins varied: for coniferous pure forest, the models showed better fit in plantations than natural forests, while for mixed forest, the models performed better in natural forests. Additionally, the models generally outperformed for coniferous species than broadleaved species. 3) All carbon storage models revealed that asymptotic values followed a decreasing trend (a₁>a₂>a₃>a₄>a₅) across site classes, with nearly constant differences between adjacent grades. Natural forests exhibited higher maximum carbon storage per hectare than plantations, and broadleaved mixed forests consistently demonstrated high carbon storage potential across all origins. 4) Under medium-quality site conditions, both plantation and natural forest carbon storage increased with stand age and tended to stabilize at near-mature and mature stages, though plantations reached their inflection points earlier than natural forests. Conclusion: The established stand mean height growth models and stand carbon storage growth models for various forest types demonstrate satisfactory fitting effect and high predictive accuracy. The developed stand carbon storage growth model, incorporating stand origin, stand age, site class, and stand density index, can effectively predict the dynamic changes of stand carbon storage with age for major tree species (groups) across different site classes in this region. Furthermore, this model can be applied to compile carbon accounting tables for typical forest types in the region.

Objective: The metaverse represents the integrated and highly convergent application of next-generation information technologies such as virtual reality, artificial intelligence, and blockchain. It provides strong momentum for the development of new quality productivity and offers novel solutions for high-quality development in the forestry and grassland sector. However, current forestry and grassland informatization still faces multiple constraints, including insufficient full-coverage perception, limited whole-process simulation capability, and difficulties in multi-stakeholder collaborative governance. This study aims to explore concrete implementation pathways for building a forestry and grassland metaverse, so as to promote the transformation and upgrading of research paradigms and management models, overcome key industry bottlenecks, and comprehensively advance the innovation and development of smart forestry. Method: On the basis of defining the concept and connotation of the forestry and grassland metaverse, an overall design approach was proposed, and a comprehensive framework integrating hardware infrastructure, technical systems, and application systems was constructed. A technology system centered on artificial intelligence, digital twins, and blockchain was systematically reviewed. In conjunction with the development needs of smart forestry, potential applications in resource monitoring, forest genetics, silviculture, forest management, ecological conservation and restoration, equipment development, industrial development, and governmental administration were discussed. Meanwhile, current technical challenges and future development pathways were analyzed from a technological perspective. Result: A forestry and grassland metaverse system framework was established, characterized by hardware infrastructure as the foundation, multi-technology integration as the core, and business scenarios as the orientation. This framework enables dynamic mapping of the real forestry and grassland world, simulation and deduction, immersive interaction, multi-agent collaboration, and intelligent decision-making. It opens up a full-scenario application mode for the forestry and grassland sector and promotes the paradigm shift of smart forestry from “perception–computation–management” to a new model of “immersion–interaction–co-creation.” In addition, this study analyzes the practical challenges currently faced in constructing the forestry and grassland metaverse, and provides directions for subsequent optimization and development. Conclusion: The forestry and grassland metaverse represents an advanced form of deep integration between next-generation information technologies and the forestry and grassland industry. It has the potential to drive the sector’s transformation from traditional static data analysis to an immersive, interactive, and co-creative paradigm. By establishing a new operational model featuring virtual–real mapping, high immersion, and human–machine collaboration, the forestry and grassland metaverse is expected to systematically address key bottlenecks in smart forestry development and further enhance efficiency and governance capacity across the entire industrial chain. Future efforts should focus on breakthroughs in core technologies and innovations in social collaboration mechanisms to accelerate practical implementation and large-scale application.

Objective: This study investigated the driving mechanisms of tree species diversity and environmental factors on soil multifunctionality in the mid-temperate forests of northeast China, and further elucidated the variations in the relationship between tree species diversity and soil multifunctionality along environmental gradients, aiming to provide a scientific basis for forest conservation and management in this region. Method: In this study, based on data from 279 sample plots in mid-temperate forests of northeast China, five soil function indicators, including total organic carbon content, total nitrogen content, total phosphorus content, available nitrogen content, and available phosphorus content, were selected. The averaging method was used to calculate the soil multifunctionality index. Multiple linear regression and structural equation modeling were employed to investigate the effects of atmospheric nitrogen deposition flux, climate, and topographic factors on the relationship between tree species diversity and soil multifunctionality, as well as the driving mechanisms of soil multifunctionality. Additionally, the interactive effects of tree species diversity and the aforementioned environmental factors were analyzed. Result: 1) Tree species diversity had a significant positive effect on soil total organic carbon content, total phosphorus content, total nitrogen content, available nitrogen content, and soil multifunctionality index (β=0.31、0.27、0.34、0.34、0.22, P<0.05), but a significant negative effect on soil available phosphorus content (β=?0.16, P<0.05). Nitrogen deposition flux showed a significant negative correlation with soil total organic carbon content, total phosphorus content, total nitrogen content, available nitrogen content, and soil multifunctionality index (β=?0.14、?0.35、?0.17、?0.22、?0.18, P<0.05). Soil pH was significantly positively correlated with total phosphorus content, available phosphorus content, and soil multifunctionality index (β=0.17、0.44、0.15, P<0.05). Soil carbon-to-nitrogen ratio exhibited a significant positive correlation with total organic carbon content, total nitrogen content, and soil multifunctionality index (β=0.38、0.16、0.13, P<0.05). 2) The relationship between tree species diversity and certain soil single-functionality indicators and soil multifunctionality index was regulated by the interaction between nitrogen deposition flux and soil carbon-to-nitrogen ratio. It was manifested that the positive effects of tree species diversity on soil total organic carbon content, total phosphorus content, total nitrogen content, and soil multifunctionality index weakened with increasing soil carbon-to-nitrogen ratio under medium-to-high nitrogen deposition environments, but strengthened under low nitrogen deposition environments. 3) The structural equation model revealed that nitrogen deposition flux was able to directly negatively affect soil multifunctionality index (β=?0.19, P<0.01), and soil pH and carbon-to-nitrogen ratio also exerted indirect negative effects on the soil multifunctionality index. Climate factors primarily indirectly influenced soil multifunctionality index via tree species diversity and soil pH, while topographic factors indirectly influenced soil multifunctionality index through tree species diversity, soil pH and carbon-to-nitrogen ratio, and soil pH indirectly regulated soil multifunctionality index by affecting tree species diversity. Conclusion: This study reveals that tree species diversity, nitrogen deposition flux, soil pH, and carbon-to-nitrogen ratio are key direct drivers of soil multifunctionality. Climate and topographic factors exert indirect influences by regulating both biotic and abiotic components. Notably, the positive effect of tree species diversity on soil multifunctionality is regulated by nitrogen deposition flux and soil carbon-to-nitrogen ratio. The findings of this study highlight the importance of regulating soil pH and soil carbon-to-nitrogen ratio under the context of atmospheric nitrogen deposition, which contributes to biodiversity conservation and the maintenance of forest ecosystem functions.

Objective: This study aims to explore the water use strategies of Pinus sylvestris var. mongolica plantations in the Mu Us Sandy Land, and analyze the dynamic variation patterns and differences in water sources and water use efficiency of P. sylvestris var. mongolica under the interaction of water table depth gradients and hydrologic year types, so as to provide a scientific basis for the stand structure optimization and sustainable management of artificial forests in arid areas. Method: This study targeted P. sylvestris var. mongolica plantations with initial water table depth (WTD) of 4 m (WTD₄), 9 m (WTD₉) and 13 m (WTD₁₃). Stable isotope techniques (δ²H, δ¹⁸O, and δ¹³C) combined with the MixSIAR model were employed to analyze the response of P. sylvestris var. mongolica water-use strategies to WTD during both dry years and normal precipitation years in the Mu Us Sandy Land. Result: 1) With the increase in WTD and the significant decrease in soil water content (decreasing from 0.029 g·g^–1 in WTD₄ to 0.022 g·g^–1 in WTD₁₃), the proportion of the root mass density of P. sylvestris var. mongolica in the 60?200 cm soil layer to the total root mass density in the 0?200 cm soil profile increased (increasing from 17.3% in WTD₄ to 24.0% in WTD₁₃). 2) Water sources of P. sylvestris var. mongolica differed under different WTD during the same period, and varied across different hydrologic years within the same WTD. The proportion of shallow soil water utilized by P. sylvestris var. mongolica in dry years was lower than that in normal years. 3) Throughout the observation period, P. sylvestris var. mongolica primarily relied on deep soil water (WTD₄: 60?360 cm; WTD₉ and WTD₁₃: 60?400 cm), and its contribution rate gradually increased with the deepening of the WTD (increasing from 34.6% in WTD₄ to 52.6% in WTD₁₃). Concurrently, the water use efficiency also increased (increasing from 102.7 μmol·mol^–1 in WTD₄ to 106.9 μmol·mol^–1 in WTD₁₃). 4) The height, diameter at breast height (DBH), crown width, and stand density of P. sylvestris var. mongolica in areas with deep water table depth (WTD₁₃) were significantly lower than those in areas with shallow water table depth (WTD₄). Conclusion: WTD and hydrologic year type drive P. sylvestris var. mongolica to develop a synergistic adaptation strategy of “root deepening-deeper water sourcing-enhanced water-use efficiency” by influencing soil water conditions, but growth becomes constrained in areas with deeper WTD. Based on this, during the vegetation restoration process, it is necessary to implement different vegetation allocation and density regulation measures according to the changes in water table depth, so as to effectively reduce the excessive consumption of deep soil water by vegetation construction and promote the sustainable development of ecological construction.

Objective: This study aims to elucidate the relationships among the reproduction and dispersal of Bursaphelenchus xylophilus, symptom manifestation, and therapeutic efficacy in infected pine trees, and to explore effective trunk injection techniques for disease control. Method: This study targeted four-year-old Pinus massoniana, eight-year-old Pinus thunbergii, and twenty-year-old naturally infected pine trees, and artificial inoculation and natural infection experiments were conducted. Artificial inoculation was performed using the highly virulent AMA3 strain of B. xylophilus, with doses of 8 000 nematodes per tree for P. massoniana and 5 000 nematodes per tree for P. thunbergii. Stratified sampling was conducted at 5 hours, 1, 3, 5, 10, 20, and 30 days post-inoculation. Quantitative analysis was performed to determine nematode populations in inoculated twigs, main trunks, and adjacent branches, while external symptom development on P. massoniana was simultaneously observed and recorded. In naturally infected forest stands, the symptom severity was graded into five stages: early 1 (beetle feeding marks present, needles not discolored), early 2 (slight discoloration of infected branches), middle 1 (single withered branch), middle 2 (<50% overall wilting), and late (≥50% overall wilting). Trunk injection treatments were administered using 2% emamectin benzoate emulsion (for young trees) and 20% emamectin benzoate soluble liquid (for mature trees), and the treatment efficacy was periodically monitored. Result: 1) Four-year-old P. massoniana: during the asymptomatic phase (5 days post-inoculation), B. xylophilus rapidly disseminated within the tree, invading the main trunk by day 3 and spreading throughout the entire plant by day 5. At this stage, the nematode populations were small, and the survival rate reached 60% following chemical treatment. As the disease progressed to the early symptomatic phase (10 days post-inoculation), nematode numbers increased exponentially, with chlorosis appearing in needles of inoculated branches, and the survival rate declined to 20%. By the full symptomatic phase (20 days post-inoculation), nematode populations peaked, and treatments were ineffective. 2) Eight-year-old P. thunbergii: during the asymptomatic phase (fully green needles), B. xylophilus aggregated in the inoculated branches with a diffusion rate of 2.5 cm·d^?1. In early stage 1 (needle chlorosis), nematodes proliferated within inoculated branches but exhibited reduced diffusion speed (1.7 cm·d^?1). At early stage 2 (needle yellowing), nematodes accelerated their migration toward the main trunk (4.0 cm·d^?1). During the middle stage (red-brown needles accompanied by chlorosis in adjacent branches), nematodes spread bidirectionally along the main trunk, reaching peak population density (4.0 cm·d^?1). In the late stage (whole plant wilting), nematode populations within the tree declined (4.0 cm·d^?1). 3) Twenty-year-old naturally infected pine trees: during early stage 1 (beetle feeding wounds on twigs, no needle discoloration) and early stage 2 (slight discoloration of infected branches), the survival rate reached 100% following chemical treatment. In middle stage 1 (wilting of a single infected branch), the survival rate decreased to 75%. By middle stage 2 (<50% overall needle wilting), the survival rate was only 20%. At the late stage (≥50% overall needle wilting), the treatment was completely ineffective. Conclusion: Based on the symptoms initially manifested in the earliest infected twigs, trunk injection therapy in pine trees aged eight years old or older is theoretically and practically feasible. Moreover, treatment efficacy has a positive correlation with tree size. This injection technique fills a critical technical gap in the management of pine wilt disease.

Objective: This study aims to investigate the spatiotemporal variations of vegetation water use efficiency (WUE) and its responses to environmental factors and drought events, thereby providing scientific support for the sustainable management of regional ecosystems and drought adaptation strategies. Method: Based on vegetation gross primary productivity (GPP) and evapotranspiration (ET) data from 2001 to 2022, and in combination with meteorological observations, water-use efficiency (WUE=GPP/ET) was computed for each pixel at a 500 m resolution. The spatiotemporal patterns of WUE and standardized precipitation evapotranspiration index (SPEI-12, the cumulative severity of drought for each year from January to December) in the study area were analyzed. Partial correlation analysis was employed to explore the relationships between WUE and key environmental factors (temperature and precipitation), as well as drought intensity, and to further examine the response of WUE to drought intensity across different vegetation types. Result: 1) The mean annual WUE in the Three-North regions was (1.12 ± 0.35) g·kg^?1 during 2001—2022. Spatially, WUE showed significant increase (P<0.05) in most northwestern desert region (excluding southern Xinjiang), thehilly and gully region of the Loess Plateau, and the centralagricultural region of northeast and north China plain, while WUE in southern Xinjiang, aeolan sand area, and the northern agricultural region of northeast and north China plain decreased significantly (P<0.05). 2) The response of WUE to precipitation and temperature exhibited marked spatial heterogeneity. WUE in most area of the northwestern desert region, the hilly and gully region of the Loess Plateau, the aeolan sandy region, and the central agricultural region of the northeast and north China plain was primarily influenced by variations in precipitation. In contrast, WUE in the Junggar basin and Tarim basin peripheries, the central hilly and gully region of the Loess Plateau, the Hunshandake and Hulunbuir sandy lands, as well as the southern part of the northeast–north China plain agricultural region was predominantly affected by temperature changes. 3) In humid regions, vegetation WUE increased with the intensification of drought, whereas in arid regions, it showed the opposite trend. Additionally, WUE responses to drought varied across vegetation types, the WUE of forests and grasslands significantly increased under mild and moderate drought conditions, but significantly decreased under severe and extreme drought conditions, with grasslands showing lower sensitivity. The WUE of shrubs significantly increased under mild drought conditions, but significantly decreased under moderate and severe drought conditions. Conclusion: The vegetation WUE in the Three-North Shelterbelt Forest Program Region exhibits a spatial distribution pattern that decreases progressively from east to west. In the humid regions, WUE increases with the intensification of drought, while there are significant differences in the response strategies of WUE to environmental changes and droughts across different vegetation types, with grasslands being particularly sensitive to drought. Therefore, it is essential to develop tailored management strategies based on the natural conditions and vegetation characteristics of each region.

Objective: This study aims to investigate the mutual feedback between decomposition dynamics of Pinus massoniana roots and soil nematode trophic groups, as well as the response to forest window transformation, providing a basis for the close-to-nature management of plantations based on biodiversity maintenance and soil nutrient improvement. Method: Forest gaps with different sizes (100, 200, 400 m²) and control plots were set up in P. massoniana plantations. Through root grading and litter decomposition experiments, the decomposition rate and nutrient release of different grades of P. massoniana roots were analyzed. Morphological methods were used to identify soil nematodes in root decomposition bags, and structural equation modeling was used to systematically explore the regulatory effects of forest gap size on root decomposition, nematode communities and soil chemistry properties. Result: 1) Forest gap size significantly affected the residual rate of root mass. The 1–3 order roots decomposed faster in 200 m² forest gaps than in 100 m² and 400 m² forest gaps, while 4–5 order roots decomposed fastest in 200 m² forest gaps during 0–360 days and 400 m² forest gaps during 360–720 days. The decomposition rate of lower-order roots (1–3 order) was higher than that of higher-order roots (4–5 order). During the decomposition process, root N and P contents generally exhibited a trend of first increasing and then decreasing. 2) Forest gap increased soil nematode abundance. The Shannon-Wiener diversity index, Maturity (c-p 2–5) and biomass of soil nematodes were the highest in forest gap of 200 m², and significantly higher than those in forest gap of 400 m² (P<0.05). With the increase of root decomposition time, the abundance and biomass of soil nematodes showed a trend of first increasing and then decreasing, reaching the highest value on the 210th day. Among them, herbivorous nematodes accounted for the highest proportion in each treatment (50.13%), followed by bacterivores nematodes (21.76%). The proportion of herbivorous nematodes remained the highest across all treatments and showed an overall upward trend with the increase of root decomposition time. 3) Root decomposition and nematode trophic groups formed a two-way feedback. Structural equation modeling revealed that root decomposition time and root mass remaining rate had a significant negative impact on the proportion of omnivorous nematodes, while omnivorous nematodes had a significant positive impact on bacterivorous nematodes, and bacterivorous nematodes had a significant positive impact on root nitrogen content. This constructed a“root-nematode-nutrient”synergistic decomposition pathway. Conclusion: Forest gap significantly affects the decomposition dynamics of P. massoniana roots and changes soil nematode diversity and community structure. P. massoniana roots regulate the composition of soil nematode trophic groups through decomposition rate and nutrient release under forest gap management. Meanwhile, the trophic groups of soil nematodes with high trophic levels control the community structure through predation, thereby affecting root decomposition and soil nutrient cycling. The forest gap of 200 m² shows the best performance in the synergistic improvement of root decomposition and soil nematode diversity. The research results provide a scientific basis for the ecological restoration of degraded P. massoniana and the sustainable management of plantations in subtropical.

Objective: This study monitored the photosynthetic characteristics of Populus tomentosa and the non-structural carbohydrates (NSC) of each organ at different stages after thinning and water and nitrogen addition, and elucidated the response of tree organ-scale NSC content to light, water, and nutrient resources under different treatments, aiming to provide a solid theoretical basis for the precise cultivation and efficient utilization of resources in the P. tomentosa plantations in the region. Method: The triploid P. tomentosa S86 plantation in the North China Plain was taken as the research object, and a two-factor completely randomized block design was adopted. Two thinning intensities were set: row thinning (50% thinning, T50) and row and tree thinning (75% thinning, T75). Three water and nitrogen treatments were implemented: water and nitrogen addition (WN), water addition (W), and no water and no nitrogen addition (CK). The photosynthetic characteristics of forest trees were monitored, and leaves, branches, trunks, and roots were sampled to determine their non-structural carbohydrate, thereby clarifying the response of photosynthetic characteristics and non-structural carbohydrates to thinning and water-nitrogen interactions of P. tomentosa at different stages, and further exploring the coupling relationship between non-structural carbohydrates and photosynthetic characteristics in different periods. Result: 1) From the dry season to the rainy season, the net photosynthetic rate and instantaneous water use efficiency of P. tomentosa leaves significantly decreased. Water and nitrogen treatment mainly regulated the net photosynthetic rate of the leaves, which was also affected by the thinning intensity. In the dry season, low-intensity thinning combined with irrigation plus fertilization, and irrigation was able to increase the net photosynthetic rate of P. tomentosa by 103.51% and 45.16%, respectively. In the rainy season, only high-intensity thinning followed by irrigation was able to increase the net photosynthetic rate by 30.31%. 2) The alternation of dry and rainy seasons led to an increase in the content of soluble sugars, starch, and NSC in leaves, branches, trunks, and roots. However, there were differences in the responses of different organs to thinning and water-nitrogen regulation. Irrigation and fertigation significantly promoted the increase in soluble sugar and NSC contents in leaves and branches during the dry season, but significantly decreased the soluble sugar and NSC contents in roots. 3) Soluble sugars during the growing season were the main NSC storage form in P. tomentosa. The content of soluble sugar and NSC in different organs changed in the same pattern, showing a trend of leaves>branches, roots>stems. The starch formed by the conversion of soluble sugars was mainly concentrated in the branches and roots. 4) There was a significant positive correlation between the soluble sugar content of leaves, branches, and trunks and NSC, while the NSC of roots was jointly affected by soluble sugars and starch. In terms of different organs, there was a high correlation between NSC and its component contents in leaves and roots. 5) In the dry season, transpiration rate was the key factor explaining the variation in NSC content in various organs, with a contribution rate as high as 47.6%. The NSC content of leaves and roots in the dry season was positively regulated by photosynthetic rate, transpiration rate, and stomatal conductance, while the NSC content of leaves and roots in the rainy season was negatively regulated by leaf photosynthetic characteristics. Conclusion: From the dry season to the rainy season, the net photosynthetic rate and instantaneous water use efficiency of P. tomentosa leaves decrease. The regulation of net photosynthetic rate by water and nitrogen treatment is affected by thinning intensity. When the dry and rainy seasons alternate, NSC content of each organ increases, but there are differences in the response of different organs to thinning and water-nitrogen regulation.

Objective: This study aims to develop a low-cost, non-destructive, accurate, and batch method for detecting the oil content and fatty acid composition of Camellia oleifera kernels, to improve the evaluation efficiency of the oil traits. Method: The oil content in kernels of 220 C. oleifera clones was determined by Soxhlet extraction, and the fatty acid composition was determined by gas chromatography, respectively. The near infrared spectra of the kernels in the wavelength range of 1000?2500 nm were collected. After preprocessing the spectral data using 9 methods, the samples were divided into calibration and prediction sets at a ratio of 4:1 by random sampling (RS) and sample set partitioning based on joint X-Y distance (SPXY), respectively. The competitive adaptive reweighted sampling (CARS) was used to select the key wavelengths that were significantly correlated with the oil traits of C. oleifera from the spectral data, and the partial least squares regression (PLSR) prediction models were established for determining the oil content and fatty acid composition of C. oleifera kernels. Result: The variation ranges of oil content and the content of seven fatty acids (C16:0, C16:1, C18:0, C18:1, C18:2, C18:3, C20:1) were in accordance with or close to normal distribution. The established models for predicting oil content had good accuracy and stability. With the RS samples dividing method, the pretreatment method of standard normal variate (SNV) was optimal. With 14 key wavelengths selected, a prediction model of oil content was established with the relative percent deviation (RPD) of 5.2055, prediction set determination coefficient ($R_{\mathrm{p}}^2 $) and root mean square error (RMSE_p) of 0.965 1 and 1.854 8 g·(100 g)^?1, respectively. With the SPXY samples dividing method, the optimal SNV + first derivative (FD) pretreatment, and 25 key wavelengths selected, another prediction model of oil content was established with a RPD of 3.417 0, prediction set $R_{\mathrm{p}}^2 $ and RMSE_p of 0.916 8 and 2.622 4 g·(100 g)^?1, respectively. The models for C18:1, C18:2 and C18:3 contents were optimal under the RS method using second derivative (SD), SNV and continuum removal (CR) pretreatment methods, respectively, with RPD values of 1.939 4, 2.116 4 and 2.338 1, $R_{\mathrm{p}}^2 $ values of 0.738 5, 0.775 4 and 0.831 6, and RMSE_p values of 1.707 1%, 1.370 2% and 0.049 2%, respectively. Conclusion: The prediction model for oil content of C. oleifera kernels has been constructed based on near-infrared spectroscopy in this study. This model has high accuracy and good stability, and can be used for rapid, batch and non-destructive detection of oil content of C. oleifera kernels. The prediction models for C18:1, C18:2 and C18:3 contents can be used for preliminary prediction of unsaturated fatty acid. This study can provide scientific basis for rapid detection of oil content, fatty acid composition and other traits of C. oleifera by near-infrared spectroscopy technology.

Objective: Through genome-wide identification and bioinformatics analysis of PagABP gene family of Populus alba × P. glandulosa, the gene PagABP1 that is highly expressed in young stems, cambium, xylem and phloem was selected to explore its effect on radial and height growth of this poplar. This study aims to provide a theoretical basis for elucidating how the auxin signaling pathway regulates secondary growth of stems by studying the regulatory role of this gene in the radial and height growth of poplars. Method: Bioinformatics and related software were used to identify the members of the PagABP gene family in 84K poplar. The real-time fluorescence quantitative PCR was used to analyze the expression of PagABP1 gene in terminal buds, young leaves, young stems, young roots, mature stems, old roots, root tips, phloem, vascular cambium and xylem. Plant P_PagABP1::GUS promoter vector and overexpressing 35S::PagABP1 vector were constructed by using the PagABP1 promoter and coding region sequences, respectively. Agrobacterium-mediated method was used to create 84K poplar transgenic materials that were used to identify the effects of PagABP1 gene on poplar radial and height growth. Result: Two ABP homologous genes were identified in 84K poplar genome, and the PagABP1 gene showed relatively higher expression levels in the apical bud, young stems, phloem, cambium, and xylem. The expression locations of P_PagABP1::GUS in transgenic poplar were overlapped with those of P_pagDR5::GUS (auxin response reporter gene), mainly in the terminal bud, young stem, cambium, phloem, and primary xylem, suggesting that PagABP1 is involved in auxin-mediated regulation of radial and height growth. The germination number and growth rate of PagABP1-OE lines were significantly higher than those of the control when the truncated seedlings were planted in soil. Analysis of transgenic lines (#17、#26) that overexpressed PagABP1 gene at 60 days showed that the width of the cambium, primary xylem, and phloem of 12th internode, plant height and basal diameter increased by 50.2%, 43.3%, 1.58%, 19.14% and 19.29%, respectively, compared to the control. Conclusion: PagABP1 gene is associated with auxin expression site, mainly expressed in terminal buds, young stem, phloem, cambium, and primary xylem, affecting radial and height growth. This study can lay a foundation for further revealing the molecular mechanism of PagABP1 gene involved in stem growth of 84K poplar.

Objective: This study systematically evaluated the biosafety of first-generation transgenic BtCry1Ac European black poplar (Populus nigra) and its transgenic hybrid F₁ progeny ‘Jingxing 1’ and ‘Jingxing 2’, with a focus on the stability of the exogenous gene expression and insect-resistance traits, and investigated their potential impacts on rhizosphere soil microorganisms and biodiversity within forest stands, thereby providing a scientific basis for the biosafety assessment and industrial application of BtCry1Ac transgenic insect-resistant poplar. Method: PCR and RT-qPCR techniques were used to verify the stability of the target gene in transgenic poplar. Growth performance was evaluated by measuring plant height and diameter at breast height (DBH). Insect resistance was assessed through an 18-days feeding trial with Hyphantria cunea larvae. The pH value and major nutrient contents in the rhizosphere soil of different clones were determined using standard methods. Soil microbial community composition and diversity were profiled using 16SrRNA/ITS high-throughput sequencing. Understory weed and arthropod assemblages were monitored using quadrat surveys and Malaise traps. Result: 1) PCR and RT-qPCR detection results confirmed the stable presence and expression of the BtCry1Ac gene in both the primary transgenic P. nigra and the F₁ transgenic hybrid progeny, with a specific 546 bp amplicon detected. 2) Growth assessments revealed that tree height and DBH of transgenic clone ‘Jingxing 1’ and ‘Jingxing 2’ increased by 9.62% and 7.56%, and 17.57% and 15.07%, respectively, compared to the control 108 poplar (Populus × euramericana ‘Guariento’), though these differences were not statistically significant. 3) Laboratory feeding assays demonstrated that the insect resistance of ‘Jingxing 1’and ‘Jingxing 2’ against H. cunea larvae was significantly higher than that of 108 poplar, with larval mortality rates increasing by 116.24% and 96.21% higher than the control after 18 days. 4) Analysis of the physicochemical properties of rhizosphere soil showed that there was a modest but significant rise in pH in the rhizosphere soil of transgenic clone n208, whereas organic matter, N, P, and K contents remained statistically unchanged. 5) There were no significant alterations in the composition of dominant bacterial (Proteobacteria) and fungal (Ascomycota) phyla. There was no statistically significant difference in α diversity indices of bacterial and fungal community structure among different clones. However, β diversity analysis revealed that there was significant differentiation in fungal community structure, while the bacterial community structure remained stable. 6) Understory surveys recorded 14 weed species (8 families) and 22 arthropod families (6 orders). The expression of BtCry1Ac gene did not have a significant impact on the species richness, Shannon diversity, dominance, nor evenness indices of weed communities. Target Lepidopteran pests declined markedly, yet overall arthropod community composition was highly similar to the control, with no significant changes in key diversity metrics. Conclusion: BtCry1Ac-transgenic poplar stably expresses the exogenous gene and exhibits high insect resistance, with no significant adverse effects on soil nutrient cycling, microbial α diversity, and the stability of understory biological communities. The hybrid progeny ‘Jingxing 1’ and ‘Jingxing 2’ demonstrate promising insect resistance and application potential. This study provides a scientific basis for the environmental biosafety assessment of transgenic poplar, and long-term ecological monitoring is recommended to systematically evaluate their impact on the ecological environment.

Objective: Prunus simingensis, a new species of Prunus subgenus Cerasus, was discovered in Siming Mountain, Ningbo, Zhejiang Province, China. In this study, morphological observations and molecular phylogenetic analyses were used to comprehensively describe and taxonomically identify this species, to determine its phylogenetic status and reveal its morphological distinctions from the closely related species, P. serrulata. Method: Morphological comparisons were conducted based on herbarium specimens of the new species and closely related species, supplemented by field survey data. Phylogenetic relationships within subgenus Cerasus were analyzed based on complete chloroplast genome sequences. Sequences were quality-filtered and aligned using MAFFT. Phylogenetic trees were constructed using maximum likelihood (ML) in IQ-TREE and neighbor-joining (NJ) in MEGA to verify the phylogenetic position of P. simingensis. Result: 1) Morphological studies showed that P. simingensis has green petioles, leaves, pedicels, and sepals, white petals, pubescent pedicels and styles, and red fruits. In contrast, P. serrulata has brown to reddish-brown corresponding organs, petals turning light pink at late flowering, glabrous pedicels and styles, and dark purple-black fruits. 2) Phylogenetic analyses showed that P. simingensis was closely related to P. serrulata, but formed an independent clade, supporting its recognition as a new species of subgenus Cerasus. Conclusion: Based on comprehensive morphological and molecular evidence, this study confirms P. simingensis as a new species in subgenus Cerasus. The discovery increases the diversity of subgenus Cerasus in eastern China, and also provides a reference for classification, evolutionary research, and conservation of subgenus Cerasus plants.

Objective: This study aims to investigate the fecal virus metagenome of captive and wild Asian elephants in Yunnan, so as to provide a theoretical foundation for the conservation of this endangered species. Method: Fresh fecal samples from captive breastfed young elephants, captive adult elephants, and wild adult elephants were collected. The metagenomic sequencing and virus metagenomics analysis methods were used to comprehensively understand the landscape structure of the Asian elephant fecal DNA virus community. Result: The results revealed that Myoviridae emerged as the most prevalent virus family in the fecal matter of calves, whereas Siphoviridae dominated in the adult elephants. Wild adults exhibited clearly higher Podoviridae abundance than captive adults. At the species level, Synechococcus phage S-CRM01 and Erwinia phage Ea35-70 were dominant in calves, whereas uncultured Mediterranean phage uvMED was most prevalent in adults. Wild adults showed notably higher abundance of EBPR podovirus 3 than captive adults. Furthermore, this study uncovered the presence of herpesvirus in the fecal samples of the calves, having the possible association of this virus family with EEHV. Conclusion: There are significant differences in the composition of fecal viral communities between captive and wild elephants, as well as between calves and adults. This work sheds light on the possible risk of EEHV infection among Asian elephant populations in Yunnan, and suggests the need for proactive conservation strategies and continued surveillance efforts.

Objective: The existing automatic forest change detection methods can only detect the change areas, and depend on bitemporal image classification to identify change directions. Most of the data sources are only optical satellite images, so that the frequency of change detection is limited by imaging conditions such as cloudy and foggy weather. The effective synergy of multispectral and SAR images based on data availability to shorten the forest change detection cycle and to build end-to-end models for the change detection of land cover and forest types are essential for dynamically monitoring the forest resource. Method: This study proposes a forest classification and change detection network (FCCDNet), which needs two Sentinel images from different times, either Sentinel-1 or Sentinel-2, as the input and gives three raster maps as output, one with land cover types and one with 0?1 for changed-unchanged classification on each pixel. The model includes a parallel Swin Transformer backbone network automatically for extracting multilevel features of the pre-temporal and post-temporal data, a feature fusion module for generating forest change discrepancy features, and a multitasking learning decoder for simultaneously obtaining the change area and land cover type of the pre-temporal and post-temporal. The model was trained and validated in a study area covering 980 km² in Vastra Gotland in Sweden, using images from Sentinel-1 and Sentinel-2 satellites in 2018 and 2023. A dataset was constructed based on multiple reference data sources, including Swedish national forest inventory data and Swedish forest distribution maps, to train the model. This study compared and validated change detection algorithms such as iterative weighted multivariate change detection (IR-MAD), difference in vegetation index (dVIs), Bitemporal Image Transformer (BIT), and random forest classification comparison method, and analyzed the applicability of forest change detection using different combinations of multispectral and SAR data. Result: The proposed FCCDNet model was able to efficiently and accurately detect forest change areas and directions. When using bitemporal Sentinel-2 images, the classification and change detection accuracies for the two periods of multispectral images were 93.26% and 90.56%, respectively, which were significantly higher than the accuracy using IR-MAD (77.68%), dVIs (78.09), and BIT (79.14%). When the paired Sentinel-1 and Sentinel-2 were used as pre- and post- temporal images, changes were also able to be detected but with lower accuracy (65.94%?76.68%). Conclusion: FCCDNet has achieved the end-to-end forest type change detection with high accuracy and can to some extent solve the problem of forest change detection cycle being limited by the lack of high-quality optical image data, and also shows robustness against salt-and-pepper effects on mapping and exhibits sensitivity to changes with smaller amplitude. The FCCDNet model and data processing framework can support dynamic monitoring of forest resources with high automation and fast response.

Objective: The purpose of this study is to integrate high-resolution UAV data with Sentinel-2 satellite imagery and utilize the Gradient Boosting Regression Tree algorithm to achieve accurate monitoring of sparse forest canopy closure in the Returning Farmland to Forest Project areas, thereby providing technical support for effectiveness assessment of the new round of the project. Method: UAV LiDAR and visible light image data were collected in typical areas of returning farmland to forest. Combined with Sentinel-2 remote sensing images in the growing and non-growing seasons of 2024 and terrain data, a gradient boosting regression tree model was established to estimate the canopy closure of the sparse forest, and its accuracy and discrimination ability were evaluated. Result: With UAV-based LiDAR point cloud and visible light images of 90 open forest plots of land for returning farmland to forests, the canopy height model (CHM) combined with the threshold segmentation method were used to construct 5 764 sparse forest canopy closure sample points. Based on multi-temporal Sentinel-2 remote sensing image features and topographic information, a gradient lifting regression tree model was established to realize the accurate monitoring of sparse forest canopy closure, and the model coefficient of determination (R²) was 0.731, the root mean squared error (RMSE) was 0.028, and the mean absolute error (MAE) was 0.021. The vegetation indexes and reflectance of non-growing seasons and the elevation were the key factors for estimating sparse forest canopy closure. Conclusion: The gradient boosting tree regression model constructed by combining high-precision UAV LiDAR data and Sentinel-2 remote sensing images can better predict the sparse forest canopy closure, and has good stability under the influence of different geographic environments and vegetation types, which is of great significance for the effectiveness assessment of the new round of returning farmland to forest projects in Inner Mongolia.

Objective: This study aims to investigate the forced-vibration responses of walnut trees with different sizes, and to address the problems of low efficiency and a low fruit removal rate in vibratory walnut harvesting. Method: A terrestrial 3D laser scanner was used to acquire point-cloud data of walnut trees. After preprocessing the tree point clouds, tree skeletons were extracted. Siemens NX was employed to perform 3D fitting and reconstruction, and 3D walnut-tree models with different size parameters were established. Material-property parameters were calibrated using measured frequency spectra, and the maximum relative error of resonance frequencies observed in both experiments and simulations was only 0.22%, ensuring the accuracy of the 3D models. ANSYS was used to conduct harmonic response analyses on the 3D model of walnut trees, to investigate the effects of excitation frequency, excitation force, and excitation height on vibration acceleration, and to analyze the displacement and acceleration responses of walnut trees with different sizes under different frequencies. In addition, suitable harvesting frequencies for walnut trees of different sizes were further determined by integrating the displacement and acceleration responses of fruiting branches with the whole-tree responses shown in harmonic-response contour plots. Result: The peak acceleration response decreased with increasing trunk diameter, tree height, and crown width. Higher trees and larger crowns exhibited weaker responses to high-frequency excitation, indicating that the geometric characteristics of the tree significantly affect its vibration characteristics. The vibration harvesting parameters of walnut trees were subjected to the response surface analysis and optimized to obtain an optimal parameter combination. Under the optimal excitation conditions, the walnut harvesting rate exceeded 90% for all tested trees, indicating that the optimised vibration parameters can provide guidance for parameter settings of vibratory walnut-harvesting devices. Conclusion: The walnut-tree modelling method described in this study enables reconstruction of fine lateral branches, and the reconstructed whole-tree models better capture realistic growth morphology. Walnut trees with different trunk diameters, heights, and crown widths show distinct vibration responses. The suitable excitation frequency range is 10–20 Hz, which can be further narrowed according to specific tree-structure parameters.

Objective: This study aims to establish a life cycle dataset for stone-wood-polymer composite flooring to comprehensively quantify the environmental impacts and biological carbon storage of the production process of such flooring, and to compare the environmental performance of this new type of flooring with that of traditional indoor flooring materials to understand its environmental advantages and disadvantages, and to propose measures to enhance the environmental performance of stone-wood-polymer composite flooring, quantify its improvement potential, and provide support for the green and low-carbon development of the industry. Method: This study established a cradle-to-gate life cycle model of stone-wood-polymer composite flooring and quantified its environmental impacts, including primary energy demand (PED), abiotic depletion potential (ADP), global warming potential (GWP), water use (WU), acidification potential (AP), eutrophication potential (EP), respiratory inorganics (RI), ozone depletion potential (ODP), photochemical oxidation formation potential (POFP), ionizing radiation potential (IRP), ecotoxicity (ET), energy conservation and emission reduction (ECER) index, and biogenic carbon stock. Result: The raw material acquisition stage was the largest contributor to midpoint environmental indicators, accounting for over 63% of all indicators. The flooring manufacturing stage contributed 35.76% to the ET, while the transportation stage was a relatively minor contributor. The cradle-to-gate ECER index of 1 m² of stone-wood-polymer composite flooring was 4.12E?11. Polyvinyl chloride and polyethylene were the main environmental hotspots during the raw material acquisition stage, while electricity, natural gas, and diesel were the main hotspots during the flooring manufacturing stage. One square meter of stone-wood-plastic composite flooring had a biogenic carbon stock of 0.12 kg CO₂ eq, accounting for 1.1% of its GWP. To enhance environmental performance, future efforts should focus on improving material efficiency by reducing the consumption of polyvinyl chloride, polyethylene, and calcium carbonate during the production of stone-wood-plastic composite flooring. In addition, energy utilization efficiency should be enhanced by lowering electricity consumption during the manufacturing stage, in order to enhance the environmental performance of stone-wood-polymer composite flooring. Conclusion: This study fills the gap in existing research on the environmental performance of flooring materials. It helps relevant parties such as flooring manufacturers, property developers, designers, consumers, and researchers to understand the comprehensive environmental performance of stone-wood-polymer composite flooring. Based on the production practices of enterprises, feasible improvement measures are proposed, which can provide valuable references for the green and low-carbon development of the stone-wood-polymer composite flooring industry.

Objective: This study aims to quantitatively analyze the mechanism and impact pathways of forest sustainable management on "Four-Repository" security, providing decision-making references for improving forest resource management system construction. Method: Based on panel data from 31 provinces in China from 2011 to 2022, this study comprehensively employed the entropy method, two-stage least squares method, and mediation effect model to construct an evaluation index system for forest “Four-Repository” security and analyze the impact mechanism of forest sustainable management on “Four-Repository” security. Result: 1) Forest sustainable management has a significantly positive impact on “Four-Repository” security, with the greatest impact on forest resource utilization sustainability, and relatively smaller impacts on forest resource protection investment and forest system restoration intervention. 2) Forest sustainable management promotes “Four-Repository” security through two pathways: enhancing forestry green development resilience and strengthening forest ecosystem service value. The impact on forest resource utilization sustainability is mainly exerted through the pathway of enhancing the ecological service value, while the impact on forest resource protection investment and system restoration intervention is significantly operated through both pathways of enhancing forestry green development resilience and strengthening forest ecosystem service value. 3) The impact of forest sustainable management on “Four-Repository” security shows significant differences across different functional zones and economic development level regions. Forest resource utilization sustainability plays the most prominent role in key ecological functional zones, and different economic development level regions exhibit evolutionary characteristics from resource dependence to efficiency improvement and then to ecological service orientation. Conclusion: To deepen the synergistic development of forest sustainable management and “Four-Repository” security, it is necessary to strengthen policy orientation for sustainable utilization of forest resources, construct differentiated regional forest resource management systems, establish synergistic enhancement mechanisms for forest resilience and ecological services, improve institutional systems for forest “Four-Repository” security assurance, and enhance the comprehensive support capacity of forest resources for “Four-Repository” security.

Objective: This study aims to clarify the altitudinal distribution patterns of species diversity of different plant life forms in broadleaved species–Pinus koraiensis forests in Mt. Changbai, and to reveal their environmental implications, thereby providing a scientific basis for the conservation of biodiversity in temperate montane forests. Method: Based on data from 45 established forest community plots (with 50 m elevation intervals), this study explored the variation in plant diversity along the altitudinal gradient in broadleaved species–P. koraiensis forests. Nonlinear regression, correlation analysis, and variance partitioning methods were used to elucidate the differential effects of topographic factors (elevation, slope, aspect), soil properties (pH value, carbon, nitrogen, and phosphorus content), climatic parameters (mean annual temperature), and biotic factors (canopy density, tree height, diameter at breast height, and crown width) on the diversity of trees, shrubs, and herbaceous plants. Result: 1) A total of 40 tree species (12 families, 23 genera), 58 shrub species (17 families, 28 genera), and 105 herb species (41 families, 87 genera) were recorded. The small-diameter trees (DBH ≤ 5 cm) had high proportion, indicating favorable forest regeneration. 2) Within the elevation range of 700–1050 m, shade-tolerant species dominated in terms of individual number and importance value, while the basal area was primarily dominated by the constructive species P. koraiensis and the dominant species Tilia amurensis. The proportion of coniferous tree species increased with elevation. 3) Arbor species richness exhibited a unimodal pattern along the altitudinal gradient, shrub species richness decreased consistently, and herb species richness showed an initial decline followed by an increase. 4) Topographic, soil, and climatic factors jointly influenced the diversity of the arbor layer, with temperature variation driven by elevation explaining 27.0% of the variance. Shrub layer diversity was mainly controlled by topographic factors (30.7%), while herb layer diversity was significantly affected by topography, soil, mean annual temperature, as well as forest canopy density and arbor layer DBH (P<0.05). Conclusion: The altitudinal differentiation of plant diversity in the Changbai Mountain broadleaved species–P. koraiensis forests is jointly driven by multiple factors including topography, climate, soil, and canopy structure. Trees, shrubs, and herbs exhibit distinct response patterns to elevation and environmental factors.