Objective: Wetland vegetation can purify the environment, regulate climate, and improve the soil, which is of great significance to the ecological security and stability of the wetland system. Wetland vegetation communities are, however, under serious threat from accelerated global warming and human disturbance. Probing the long-term spatial-temporal pattern of wetland vegetation cover change and its response to climate change and human activities are important for informing decisions on wetland protection. Method: It is difficult to collect long-term, reliable optical observations with high spatiotemporal resolution in the Dongting Lake wetland due to its location in the subtropical monsoon climate zone and its frequent cloud and rainy conditions. Firstly, this study used the flexible spatiotemporal data analysis fusion (FSDAF) algorithm to fuse Landsat and MODIS images to obtain the monthly normalized difference vegetation index (NDVI) time series during the study period (2000—2019). To quantify the response of wetland vegetation cover to environmental changes and human disturbance at different time scales, the seasonal and trend components of wetland vegetation NDVI in Dongting Lake were separated by an improved seasonal-trend decomposition procedure based on the loess (STL) time series decomposition method. Based on the linear trend analysis and NDVI seasonal and trend component data with a high spatiotemporal resolution, the spatiotemporal dynamic patterns of wetland vegetation at different scales were identified. Finally, a partial correlation-based approach was used to quantitatively assess the contributions of three major climatic factors (i.e., temperature, precipitation, and solar radiation) and anthropogenic factors to seasonal and trend vegetation changes from 2000 to 2019. Result: 1) From 2000 to 2019, the trend component and seasonal component of NDVI vegetation in Dongting Lake wetland showed spatial differentiation patterns, but overall exhibited a “greening” trend, with a change rate of 4.8×10^?3 a^?1 and 0.4×10^?3 a^?1, respectively. 2) Vegetation growth has a significant positive correlation with temperature and solar radiation, and its seasonal correlation with vegetation change is generally greater than trend correlation. The correlation between precipitation and vegetation is relatively low, and it has a negative correlation with rice (trend component R=?0.27; seasonal component R=?0.42). 3) From 2000 to 2019, human factors and climate change have driven 58% and 42% of the NDVI vegetation changes in the Dongting Lake wetland, respectively. Among them, the relative contribution rates of human factors to the long-term and seasonal growth and restoration of wetland vegetation are 55% and 62%, respectively, while the relative contribution rates of climate change to the long-term and seasonal degradation of wetland vegetation are 53% and 56%, respectively. Conclusion: Human factors have promoted the growth of wetland vegetation and are the main driving force behind the greening of Dongting Lake wetland vegetation from 2000 to 2019, while climate change poses a threat to wetland ecosystems. Adopting appropriate ecological protection and restoration measures is still an important means to achieve sustainable development of the Dongting Lake wetland ecosystem in the future. This study elucidates the response mechanism of Dongting Lake wetland vegetation to climate change and human activities, providing a scientific basis for spatial decision-making on wetland conservation.

Objective: Considering that the unmanned aerial vehicle(UAV) LiDAR-derived canopy height model (CHM) is prone to distortion in areas with complex terrain, which significantly limits the accuracy of the individual tree segmentation, this study aims to propose a new method that utilizes the combination of CHM and digital surface model (DSM) to segment individual tree. Method: By using UAV-LiDAR data and choosing 3 standard plots of middle-aged forest and young forest in steep areas of Cunninghamia lanceolata plantation with middle and high crown density in Yangkou forest farm, Shunchang country, Fujian Province, this paper used the field-measured and visual interpretation data to calculate and analyze the accuracy of treetop detection and individual tree segmentation which were acquired by using local maximum algorithm with 4 fixed window size and extremum controlling watershed algorithm based on the combination of CHM and DSM and compared them with the traditional method of using CHM alone. Result: In the matter of treetop detection, number of detecting treetops and detection percentage for each plot showed a downward trend with window size increasing; The optimal window size of 3 middle-aged forest plots is 0.3 m and the optimal window size of 3 young forest plots is 0.2 m. In this configuration, the individual tree of one-to-one correspondence and the producer’s accuracy are the maxima. By using the CHM alone, the detection percentage are higher but the accuracy of treetop detection are lower than using the combination of CHM and DSM because the CHM-based local maximum method is prone to multiple detecting treetops in the individual tree on the optimal window size. The accuracy of treetop detection in the young forest plots are higher than in the middle-aged forest plots. The reason is that the crown breadth and adjacent distance of individual trees in the young forest plots are more consistent which is more adapted to the local maximum algorithm. In the matter of individual tree segmentation, on the optimal window size, by using the combination of CHM and DSM, the accuracy of individual tree segmentation are higher than using the CHM alone and the accuracy of individual tree segmentation in the young forest plots are higher than the middle-aged forest plots. Conclusion: Because the direct data source of treetop detection and individual tree segmentation is DSM which reflects the crown surface veritably with no distortion, the result represents the real individual tree crown boundary and reaches the high accuracy in the young and middle ages of Cunninghamia lanceolata plantation with middle and high crown density (the detection rate r is more than 88%, the accuracy p is more than 92% and the F-score is more than 91% for each plot). Moreover, in this study, the method integrates into the ArcGIS Model Builder which is helpful to build an accurate, automatic, and integrated platform for individual tree segmentation of UAV-LiDAR.

Objective: This study aims to address the influence of complex factors such as lighting, background, and shooting scale on the accuracy of wildlife image recognition. Method: In this study, the wild animal images captured by infrared triggered cameras in the wild were used as the object: 1) Two publicly available wildlife datasets, ENA24 and NACTI, were used to construct disjoint datasets S1 and S2, comprising a total of 11 animal categories and 25 591 images. 2) To tackle domain shift issues, a ResNet50 network was utilized as a feature extraction module to build a domain adversarial network, effectively alleviating domain bias. 3) A representation learning network incorporating Wasserstein distance and correlation alignment was proposed to establish a transfer learning network for feature extraction and recognition, so as to further exploit transferable features. Result: The performance of different models in wildlife recognition was evaluated using the average accuracy metric. Results indicated that the average accuracy on 11 wildlife categories for eight models, namely ResNet50, DDC, DCORAL, DAN, DANN, CDAN, HAN, and JTN, was 48.4%, 51.6%, 49.6%, 52.6%, 45.2%, 50.9%, 54.6%, and 53.5%, respectively. Upon enhancing the ResNet50 base model with improved residual modules and introducing a representation learning network incorporating Wasserstein distance and correlation alignment, the average accuracy for 11 wildlife categories was improved by 2.7% compared to the existing best result with the comparative methods. Conclusion: The transfer learning method based on Wasserstein distance and correlation alignment has achieved an average accuracy of 57.3% in wildlife recognition. The introduction of representation learning based on Wasserstein distance and correlation alignment can effectively improve the accuracy of the wildlife recognition model.

Objective: Aiming at the problems of large amount of data, high proportion of invalid images, and complex image backgrounds in wild animal images captured by infrared cameras, a model that can automatically and accurately recognize images is proposed, providing more efficient support for biodiversity research and wildlife conservation work. Method: Collect and organize approximately 5 TB of image data captured by infrared cameras at various stations of the Beijing Ecological Observatory Network over the past 4 years. After manual annotation and data augmentation, create a total of 4234 image datasets in 10 categories. Based on ConvNeXt convolutional neural network and combined with the characteristics of wild animal image datasets in Beijing, a BSGG-ConvNeXt model was designed. BlurPool, SENet, global response normalization layer (GRN), and GCNet were used to improve the recognition ability of the model. The impact of training strategies on the recognition accuracy of ConvNeXt network was explored on a self-built dataset. By comparing with other classic models, the advantages of the BSGG-ConvNeXt model are clarified. Verify the generalization ability of the model using publicly available infrared wildlife snapshot serengeti (SS) dataset andcaltech camera traps (CCT) dataset. Result: Taking the ConvNeXt size model of the ConvNeXt model as an example, the accuracy in the self-built dataset is 74.13%, and the multiply add cumulative operands (MACs) are 4.47×10⁹. By applying different improvement schemes, it was found that the accuracy increased by 2.2% and MACs decreased to 1.07×10⁹ after using BlurPool. After using SENet, the accuracy improved by 3.2%. After using GRN and removing the scaling layer, the accuracy improved to 87.18% and the number of parameters increased to 27.88×10⁶. After using GCNet, the accuracy was improved to 75.44% without increasing the computational load, but the number of parameters increased to 28.25×10⁶. The BSGG-ConvNeXt obtained by combining the above improvement schemes is applied to the ConvNeXt-T model to obtain the BSGG-ConvNeXt-T model. Although there is a slight increase in the number of parameters, the MACs are reduced to 1.07×10⁹, and the accuracy of the model is improved to 83.63%, which is higher than the original model. After using pre-trained weights, the accuracy of the BSGG-ConvNeXt-T model can reach 94.07%, which is higher than the accuracy of ResNet-50 (76.39%), ResNeXt-50 (87.60%), MobileViT (90.00%), DenseNet (87.66%), RegNet (69.90%), ConvNeXtv2 (91.93%), SwinTransformer (86.23%), and MobileOne (71.53%) models. After applying the BSGG-ConvNeXt model to four different network sizes of ConvNeXt models, its performance in the self-built dataset is better than that of the unimproved model. The recognition accuracy of the BSGG-ConvNeXt model in the SS dataset can reach 50.28%, and the recognition accuracy in the CCT dataset can reach 56.15%, both of which are higher than the accuracy of the original model. Conclusion: The BSGG-ConvNeXt model has a higher accuracy in recognizing wild animal images captured by infrared cameras, and performs well on both self built and publicly available wild animal infrared image datasets, with a certain degree of generalization ability.

Objective: Based on locations tracked by satelite of Oriental Stork born in the Yellow River Delta, the nation-wide distributions of suitable habitats in both summer and winter were predicted. This study was intended to provide an important scientific basis for the collaborative conservation of Oriental Stork. Method: Using the satellite tracking data of 80 Oriental Storks in the Yellow River Delta of Shandong Province between 2016 and 2022, 5 283 habitat locations in summer and 4 730 habitat locations in winter were selected through spatial auto-correlation analysis. The MaxEnt model was employed to predict the potential suitable habitat distribution for Oriental Storks in both summer and winter, and to rank the suitability habitats. Result: The analysis revealed that the MaxEnt predictions are satisfactory, with AUC values exceeding 0.8 for both the summer (0.866) and winter (0.838). Six environmental factors such as elevation, isotherm, distance to lakes and rivers, average daily temperature range, precipitation seasonality and the land-use type—significantly influence the distribution of Oriental Storks in the Yellow River Delta. In summer, there was a highly suitable habitat area of 14.75×10⁴ km2 for Oriental Storks, constituting 13.01% of the total suitable area. These habitats were predominantly distributed in the Songnen Plain (57.52%), the Bohai Bay (17.50%), the Liaohe Plain (14.94%). The main habitat types in summer included wetlands (35.30%), cropland (33.74%), water (12.43%). The highly suitable winter habitat for Oriental Storks covered an area of 11.63×10⁴ km2, constituting 11.62% of the total suitable area. It was primarily situated in the Middle-Lower Yangtze Plains (49.02%), Hongze Lake of the Huaihe River basin (23.75%), the Bohai Bay (11.52%). The main winter habitats included wetlands (40.56%), cropland (29.68%), water (18.45%). The overlapping area of highly suitable habitat in summer and winter was 2.13×10⁴ km2, primarily concentrated in the Bohai Bay (59.81%), the coastal area of Shandong Peninsula (23.24%) and Jiangsu (9.34%). Conclusion: The results indicate that the suitable habitat in summer extends to Songnen Plain, Sanjiang Plain and Liaohe Plain, challenging conventional understanding about the fledging dispersal for Oriental Storks. for Oriental Storks. This study offers a crucial scientific foundation for the collaborative conservation of this species.

Objective: Effects of different management methods on stand growth and understory vegetation of Larix principis-rupprechtii in Qinling Mountains were discussed in order to improve ecosystem productivity, optimize management technology of Larix principis-rupprechtii in this area, and provide theoretical and practical basis for sustainable forest management. Method: Taking the Larix principis-rupprechtii in Pingheliang, a teaching experimental forest farm of Northwest Sci-Tech University of Agriculture and Forestry, as the research object, according to the technical measures of tending and thinning under the guidance of close to natural management, two management treatments were set: thinning (T1, thinning intensity 20%) and window (T2, only a few reserved trees are left, and other trees are cut out to form a square forest window of 32 m×32 m.), and the unmanaged sample plot was taken as the control (CK). After 7 years of thinning and window management, the effects of different management methods on stand growth and understory regeneration and growth were investigated. Result: After thinning, the average DBH, volume per tree, and total stock of trees were significantly higher than those of control group, but the tree height changed little. The growth and development of understory seedlings under thinning and window treatment were significantly different from those in control group (P<0.05). In the thinning treatment, the survival rate of Pinus armandii and Picea asperata seedlings was higher, but the Betula albosinesis seedlings were all dead. Thinning and window treatment not only promoted the growth of artificial replanting seedlings, but also promoted the natural regeneration of seedlings. Species diversity of understory shrub increased significantly after thinning and window treatment. After thinning and window treatment, the species and coverage of understory shrub increased, and the species richness also increased significantly. The thinning treatment had the best effect. There are fewer common plant species between normal plots and post-management plots, but there are more common species between thinning treatment and forest window treatment, and the similarity coefficient is high. Conclusion: The two management methods of thinning and forest window can promote the growth of Larix principis-rupprechtii, and the effect of thinning management on the growth and seedling renewal of Larix principis-rupprechtii plantation is more obvious, and the species diversity of shrub and grass is also significantly increased after thinning. It is more reasonable to adopt thinning management in the artificial forest of Larix principis-rupprechtii plantation in other regions of Qinling Mountains.

Objective: The study aims to investigate the temporal-spatial variation and drivers of phenological periods in Pinus massoniana and Pinus elliottii forests, in order to provide a theoretical basis for understanding and predicting the temporal-spatial pattern of forest carbon sink in the red soil hilly region. Method: The temporal and spatial dynamics of the effective leaf area index (LAIe) were extracted from a total of 29 plots (18 for P. massoniana and 11 for P. elliottii), based on digital camera time series data collected between 2017 and 2021. A generalized double logistic model of LAIe was used to determine the phenological periods (start time of growing season, SOS; end of growing season, EOS; length of growing season, LOS). The coefficient of variation was used to characterize the spatiotemporal variation amplitude of phenological periods. Pearson correlation analysis and linear mixed model were employed to investigate the driving effects of climate (aridity index, air temperature, precipitation, saturation vapor pressure deficit, photosynthetically active radiation), soil (soil temperature and humidity, soil thickness, soil gravel content) and biological (stand density, understory vegetation richness) factors on phenological periods. Result: 1) The phenological characteristics of P. massoniana and P. elliottii forests exhibited a unimodal curve, with the former lacking an obvious peak. Compared to P. massoniana forest, the P. elliottii forest had later SOS but higher LAIe with greater amplitude of seasonal variation. 2) The phenological periods of P. massoniana forest exhibited greater variability than those of P. elliottii forest at both temporal and spatial scales. P. massoniana forest had greater spatial variation coefficients of SOS, EOS, and LOS and exhibited greate temporal variation coefficient of SOS than those in P. elliottii forest. 3) On an interannual scale, SOS and EOS in P. massoniana forest showed negative and positive correlations with soil moisture at 0–120 cm depth in early spring and dry season, while EOS in P. elliottii forest was positively correlated with soil moisture at 0–60 cm depth in dry season. 4) The spatial variation of phenological periods in P. massoniana forests was influenced by stand density, species richness in the herbaceous layer, and gravel content within the 0–60 cm soil layer. Conclusion: There are significant differences in the phenological characteristics between P. massoniana and P. elliottii forests in terms of curve peak value, SOS, and LAIe amplitude and value. The phenological period in P. elliottii forests is more stable in temporal and spatial scale. The temporal and spatial variation patterns of phenology in P. massoniana forests within the red soil hilly region are jointly influenced by intraspecific and interspecific competition intensity, as well as soil resource heterogeneity.

Objective: 1) To quantify the effects of the“outdated”models on the population parameter estimates. 2) To correct bias due to“outdated”model by model-assisted inference. 3) To quantify the correction effects of the errors-in-variable (EIV) model on the inferential bias. Method: Correcting for the effect of outdated models on estimates (the population mean, and the variance of the population mean) using EIV model under three inference frameworks: design-based inference, model-based inference, and model-assisted inference. Result: 1) Compare the estimates based on model-based inference with the estimates of two-stage sampling. The model-based estimates of the mean, $ \hat{\mu } $, including the regular model and the EIV model, were similar to each other and to the two-stage sampling estimate of the mean, 6.774 m³·hm^?2. The design-based and the model-based estimates of $ \mathrm{\widehat{Var}}\left(\hat{\mu}\right) $ have great disparity, with two-stage sampling of 0.965 and model-based averaging 0.117, meaning that the average precision for model-based was improved by 87.93%. 2) The adverse effects of temporally external independent variables are exacerbated over time with respect to a model and propagate to the population parameter estimation. 3) In the model-assisted inference, the estimates of mean $ \hat{\mu } $, including the regular and the EIV models, range from 6.5 to 6.8, with a small fluctuation range and the same trend, and the differences between the mean estimates of the two are small, but the latter has higher inference accuracy, with an accuracy improvement range of 5.71%?22.50%, with an average of 13.34%. Conclusion: 1) Remotely sensed data as auxiliary information can effectively improve the estimation accuracy. 2) When remote sensing data are“out of date”, the model is invaild, the mean estimate bias increases, and the variance estimate is underestimated. 3) Model-assisted inference solves the problem of inference bias caused by“outdated”model, maintains the approximate unbiasedness of the estimates, and the accuracy is positively correlated with the sample size of the probability sample. 4) EIV model reduces the variance estimates, but the adverse effects of the“outdated”model cannot be eliminated by using the EIV model alone.

Objective: In the context to the global trend of decreasing surface wind speeds, known as "atmospheric stilling", differences in diurnal environmental stability primarily driven by vapor pressure deficit (VPD) and wind speed (v) are becoming increasingly pronounced. However, the biophysical control mechanisms of tree water physiological processes under different environmental stability conditions remain unclear. In this study, an ecological system of poplar plantations was targeted and the biophysical regulation mechanisms of environmental factors and endogenous circadian rhythms on leaf water physiology and trunk sap flow in trees were investigated. This study aims to explore the response patterns and influencing factors of tree water-related physiological processes, such as leaf stomatal conductance, leaf-level transpiration rate, leaf water potential, and trunk sap flow, under different nighttime environmental conditions. Method: The research was conducted in a Populus × euramericana plantation along the Chaobai River in Shunyi District, Beijing. During the growing season, gas exchange at the leaf-level and leaf water potential were measured continuously over seven clear day-night cycles on three sample trees. Simultaneously, sap flux density in the sample trees was monitored using heat diffusion probe technology, with concurrent recording changes in environmental factor, and the impact of diurnal rhythms was quantified using hours after dusk. Result: 1) Nighttime stomatal opening was observed, with synchronized occurrences of leaf transpiration and sap flux. Under stable nocturnal conditions (v=0 and ΔVPD ≤0.1 kPa), tree water physiological indicators were primarily influenced by air and soil temperatures (P<0.05), albeit relatively weak. There was a significant negative correlation between nocturnal sap flux and leaf stomatal conductance (P<0.01), indicating that sap flux was mainly used for stem water replenishment. 2) Under fluctuating nighttime environmental conditions (v>0 or ΔVPD ≥0.1 kPa), leaf stomatal conductance and sap flux density were positively regulated by air temperature (T_a) and VPD, and negatively correlated with relative humidity (RH), with T_a being the dominant factor. Leaf water potential was mainly influenced by T_a, soil water content (SWC), and soil temperature (ST). Nighttime sap flux density showed significant positive correlations with leaf stomatal conductance, transpiration rate, and water potential (R²=0.67). 3) Daytime environmental conditions fluctuated strongly, showing a significantly higher correlation between leaf water physiological indicators and sap flux density compared to nighttime. However, there was a negative correlation between leaf stomatal conductance and VPD, and there was a decoupling phenomenon between stomatal conductance and sap flux density (P=0.078). 4) The impact of the circadian rhythm, as characterized by hours after dusk, varied with changes in nighttime environmental stability. Under stable nocturnal conditions, duration after dusk significantly affected leaf stomatal conductance, leaf water potential, and transpiration (P<0.01). Under fluctuating nocturnal conditions, the influence of this factor on leaf water physiological indicators were reduced, with no significant impact on stomatal conductance and leaf water potential (P₁=0.066, P₂=0.08), indicating that nocturnal environmental fluctuations affected the manner and extent to which the circadian rhythm influenced tree water-related physiological processes. Conclusion: Under varying nighttime environmental stability conditions, there are significant differences in the biophysical processes and regulatory mechanisms of tree water physiology. When environmental fluctuations are minimal, tree water physiology processes are regulated by circadian rhythms, forming a pronounced nocturnal pattern. At this time, its impact on plant hydration should be considered. This research emphasizes the pivotal role of circadian rhythms in controlling forest water usage and recommends formulating irrigation strategies based on temporal factors and environmental stability to optimize water management and adapt to climate change. Furthermore, this study provides theoretical support for understanding forest hydrological cycles and assessing the adaptability of riparian plantations to climate change.

Objective: Plant water regulation strategy, defined as the response of plants under environmental water deficit, plays a crucial role in plant adaptation to stressed environment. Accurately evaluating plant water regulation strategies is instrumental to elaborate the water use characteristics of plants and comprehensively understand the water relations of plants, thereby revealing the adaptive strategies of plants to drought. However, current methods for accurately quantifying and evaluating plant water regulation strategies remains controversial. The objective of this study is to explore and assess the methods for accurately evaluating plant water regulation strategies, so as to provide theoretical basis for a deeper understanding of the physiological mechanisms of fast-growing tree species growing under water deficit sites. Method: Populus tomentosa (B301) was used as the experimental material. Trees were subjected to two different soil water gradients (full irrigation and no irrigation) in different seasons (dry season and wet season), and suitability of different methods quantifying plant water regulation strategy was contrasted and analyzed. Result: 1) The evaluation results of the plant water regulation strategy of P. tomentosa with hydroscape area (HSA) and daily maximum difference between predawn and midday leaf water potential under well-watered conditions (ΔΨ) were the same across different soil moisture conditions and different seasons. The results of both methods showed that the water regulation strategy of non-irrigated treatment was more isohydric than that of the irrigation treatment, and the water regulation strategy of dry season was more isohydric than that of the wet season. The results were in line with the evaluation principles of "consistency" and "homogeneity" water regulation strategies proposed in this study. 2) When the slope method of the relationship between leaf noon water potential and water vapor pressure deficit (K_ΨMD-VPD) was used to evaluate plant water regulation strategies, the results of water regulation strategies obtained from different seasons and irrigation treatments were inconsistent. The results were the same as those produced by HSA and ΔΨ in different seasons, but opposite to those of HSA and ΔΨ under different irrigation treatments. 3) When the slope method for the relationship between pre-dawn and noon leaf water potential (K_ΨPD-ΨMD) was applied, the ranking across season under full irrigation was consistent with that generated by other methods, but the ranking of inter-season evaluation under no irrigation was contrary to that generated by other methods. Conclusion: The evaluation results on the water regulation strategy of P. tomentosa with HSA and ΔΨ are relatively accurate, and the evaluation results conform to the principles of “consistency” and “homogeneity”. Therefore, the HSA and ΔΨ are ideal evaluation indexes for the water regulation strategy of P. tomentosa. However, K_ΨPD-ΨMD and K_ΨMD-VPD are not suitable for evaluating the water regulation strategies of P. tomentosa. The generality of this conclusion will need to be tested in more species in the future. The results of this study can provide methodological reference for the evaluation of plant water regulation strategies.

Objective: Cyclocarya paliurus is a unique medicinal plant in China, and its diploid and autotetraploid individuals coexist in natural populations. This study aims to compare and analyze the differences in leaf morphology, photosynthetic performance and secondary metabolite accumulation between diploidy and tetraploidy, in order to provide a basis for elite genotype selection for leaf-use plantations. Method: The leaf morphology, anatomical structure, and stomatal parameters in diploid and tetraploid adult plants from Hefeng, Hubei Province and Qingliangfeng, Anhui Province were measured. Their photosynthetic physiological parameters were also determined. The seasonal dynamics and differences of secondary metabolite profiles between two ploidies were compared. Result: 1) The length, width, and area of tetraploid leaves were 10.94 cm, 4.57 cm, and 118.84 cm², respectively, which were 19.5%, 61.4%, and 94.2% greater than those of diploid leaves. However, there was no significant difference in specific leaf mass. In similar, various tissues in leaf anatomical structure and stomatal morphology in tetraploidy were also significantly larger than that in diploidy. However, the stomatal density in tetraploidy was 158.36 stomata·mm^?2, which was 43.8% less than that of diploidy. 2) The carotenoid content in tetraploidy was significantly higher than that in diploidy, and there were no significant differences in chlorophyll a and chlorophyll b between the two ploidies. The parameters obtained from fitted curves of light response showed that maximum net photosynthetic rate (P_nmax), dark respiration rate (R_d), light compensation point (LCP), and light saturation point (LSP) in diploid were 8.367, 0.997, 25.905, and 1 527.96 μmol·m^?2s^?1, while were 13.797, 1.573, 32.905, and 1 311.36 μmol·m^?2s^?1 in tetraploidy, respectively. Measurement for instantaneous photosynthesis revealed that net photosynthetic rate, intercellular CO₂ concentration, and transpiration rate in tetraploidy were significantly higher than those in diploidy. There were no significant differences in stomatal conductance and vapor pressure deficit. 3) The accumulation peaks of major bioactive substances in leaves of two ploidies all occurred in May and September, respectively. There were no significant differences in the content of triterpenoids and flavonoids in two harvest seasons (May and September) between ploidies. The polyphenol content of tetraploidy (13.64 mg·g^?1) was significantly higher than that of diploidy (13.29 mg·g^?1) only in May, while the polysaccharide content of tetraploidy remained consistently higher than that of diploidy throughout the entire growing season, reaching 6.80 mg·g^?1 and 8.58 mg·g^?1 in May and September, respectively. Conclusion: The leaf morphology, anatomical structure and photosynthetic physiological characteristics in tetraploidy are significantly better than those of diploidy, thus promoting its leaf biomass production. The polyphenol content in May and polysaccharide content in whole growth seasons in tetraploidy are significantly higher than those in diploidy, but there is no significant difference in flavonoids and triterpenes contents in the main harvest seasons between two ploides. Comprehensively, the tetraploid is the candidate material for leaf-use plantations in low-altitude areas, and can obtain higher yields of bioactive substances in practice.

Objective: This study aims to explore the corresponding relationship between external morphological changes and anatomical structures in the differentiation process of Choerospondias axillaris flower buds, and reveal the relationship between the dynamic changes of nutrients in leaves and the differentiation process of flower buds. Method: The paraffin section method was used to observe the flower buds of C. axillaris, and the contents of soluble protein, soluble starch, soluble sugar, total phosphorus, total nitrogen, total potassium, and organic matter in the leaves near the bud were determined at key differentiation stages. Result: 1) The flower type of C. axillaris was thyrse or solitary, with the male flower as inflorescence, and the female flower as inflorescence or solitary. Most of the flower buds of C. axillaris were mixed buds, with a sprouting rate of 99% for adult male trees and 70% for female trees. 2) The differentiation of C. axillaris flower buds can be divided into 9 stages: undifferentiated stage, physiological differentiation stage, bract formation stage, sepal formation stage, inflorescence formation stage, petal formation stage, stamen formation stage, pistil formation stage, and lateral inflorescence developing stage. The differentiation of C. axillaris flower buds started at the end of March. After bud sprouts in late February, it took about 40 days to enter the physiological differentiation stage. The mid to late June was the peak period for the differentiation of the female and male primordia of flower buds. In early March of the following year, lateral inflorescences of both female and male flowers were fully developed. 3) The growth of horizontal and vertical diameters of flower buds showed a trend of first fast and then obviously slow. The horizontal diameter of female and male flower buds in the physiological differentiation stage increased by 211.36% and 231.11%, respectively, compared to the undifferentiated stage, and the size of flower buds was rapidly rising. Transverse diameters of female and male flower buds in the inflorescence formation stage increased by 5.43% and 10.00%, respectively, compared to the sepal formation stage, suggesting that growth rate slowed down. 4) The soluble protein contents in leaves on the bud base dropped to its lowest in inflorescence primordia differentiation stage, while the contents of soluble protein and soluble starch in female and male leaves reached their peeks in inflorescence primordia differentiation stage, with the values of 2.29 and 2.51, 25.43 and 21.50 mg·g^?1, respectively. During the inflorescence formation stage, the nitrogen content in female and male leaves decreased significantly, with a decrease of 22.88% and 32.51%, respectively, compared to the undifferentiated stage. The total nitrogen contents decreased by 25.35% and 34.09%, and the total phosphorus contents decreased by 41.07% and 39.67%, the total potassium contents decreased by 23.94% and 22.52%, respectively, compared to the undifferentiated stage. The carbon nitrogen ratio of female flower bud leaves ranged from 21.01 to 26.52, while male flower bud leaves ranged from 21.14 to 28.90. Conclusion: It takes about 4 months from the sprouting of the buds to the initial differentiation of pistil and stamen primordia of C. axillaris, and inflorescences are fully developed at the following year of March. The physiological differentiation process of female flowers is about 10 days later than that of male flowers. The nutrients in the leaves proximate to flower bud have great changes in physiological differentiation period. The high contents of nitrogen, phosphorus and potassium in the leaves are conducive to the physiological differentiation of flower buds, and higher carbon-nitrogen ratio can regulate the morphological differentiation process of C. axillaris. During the inflorescence formation period, the leaves need to accumulate more soluble sugar and soluble starch. The physiological differentiation stage (in late April) and inflorescence differentiation stage (in early June) are the most critical periods, when a special attention should paid to effcient irrigation and fertilization management and fruit yield regulation of C. axillaris.

Objective: This study was conducted to investigate the changes in soil nutrient and bacterial community characteristics of Phyllostachys edulis forest soil after edible fungi cultivation, and to provide a basis for the sustainable development of edible fungi cultivation under P. edulis forests afterward. Method: In October 2020, we started the imitating wild cultivation of edible fungi under the P. edulis forest in Yuyao Forestry Farm, and designed four treatments to cultivate three edible fungi, namely Dictyophora indusiata, Stropharia rugosoannulata , Morchella esculenta, and the control ( traditionally operated moso bamboo forest, no edible fungi cultivated in the undergrowth), respectively. The soil after the growth of edible fungi was collected in July 2021, and soil bacterial community diversity was studied using PCR amplification technology. We analyzed the correlation between soil nutrient status and bacterial community α-diversity and to reveal the changing pattern of soil bacterial community. Result: 1) Compared with control treatment, soil nutrients were most enhanced under S. rugosoannulata treatment, with soil organic carbon, available nitrogen, available phosphorus, available potassium, nitrate nitrogen, and ammonium nitrogen contents, increasing by 13.70%, 6.48%, 380.00%, 100.68%, 33.75%, and 20.75%, significantly(P<0.05). 2) Compared with control treatment, the cultivation of M. esculenta under P. edulis forest could better alleviate soil acidification and significantly increase the content of soil available phosphorus (P<0.05), and nitrate nitrogen by 665.60% and 250.31%, respectively. The α diversity of soil bacteria significantly increased, as well as change in the community composition of soil microorganisms in P. edulis woodland, significantly reduce the relative abundance of the phylum Acidobacteria and increase the relative abundance of the phylum Bacteroidetes (P<0.05) after the cultivation of M. esculenta. 3) The D. indusiata treatment had less effect on soil nutrients in P. edulis forests, and the composition of the dominant bacterial community at the generic level was similar to that of the control treatment, but the bacterial amplification feature sequences were of the most complex origin. 4) The dominant soil bacterial phyla were Acidobacteria and Proteobacteria, respectively (P<0.05). 5) The contents of available phosphorus and available potassium were significantly correlated with the relative abundance of bacterial communities in the treated soil (P<0.05), and there was a positive correlation between the relative abundance of the phylum Acidobacterium and soil available nitrogen, ammonium nitrogen and soil organic carbon contents, as well as negatively correlated with soil pH-value. Soil pH-value, available phosphorus, and nitrate nitrogen content were significantly correlated with indices such as Chao1, Shannon-Wiener, and Simpson (P<0.01). Conclusion: The short-term cultivation of S. rugosoannulata in the P. edulis forest has a significant effect on soil nutrient improvement. What’s more, the cultivation of M. esculenta fungi can effectively alleviate soil acidification. In the meanwhile, it has a wide variety of effects on soil bacterial communities, which can be selected for cultivation in production according to field conditions.

Objective: This study investigated the tolerance and removal ability of the plant growth-promoting bacterium Burkholderia contaminans JLS17 to Cd²⁺ and its metabolic response under Cd²⁺ stress, so as to provide a basic theoretical basis for the application of the strain in soil Cd pollution remediation, and to provide data support for exploring molecules and metabolic pathways with anti-cadmium function and the elucidation of the microbial Cd tolerance mechanism. Method: The tolerance of the strain to Cd²⁺ was evaluated by measuring the OD₆₀₀ values of cultures with different Cd²⁺ concentrations, the removal efficiency of Cd²⁺ from LB medium was determined using inductively coupled plasma mass spectrometry (ICP-MS), and the differential metabolites and metabolic pathways of the strain under Cd²⁺ stress were analyzed by untargeted metabolomics (LC-MS). Result: 1) There was a significant inhibition of Cd²⁺ stress on the growth rate and biomass (OD₆₀₀) of strain JLS17 with different levels of Cd²⁺ stress (50 mg·L^?1?800 mg·L^?1), and the inhibition increased with the increasing Cd²⁺ concentration. 2) The removal quantity of Cd²⁺ from LB medium by strain JLS17 increased with the increasing Cd²⁺ concentration (10?100 mg·L^?1) and the highest removal quantity was 55.90 mg·L^?1. However, the removal rate was less affected by Cd²⁺ concentration and maintained at 41.9%?66.0%. 3) The results of LC-MS analysis showed that strain JLS17 had the same expression trend, with 147 differential metabolites, under 50 mg·L^?1 Cd²⁺ treatment and 300 mg·L^?1 Cd²⁺ treatment, of which 92 metabolites were up-regulated and 55 metabolites were down-regulated, mainly covering amino acids and their derivatives, nucleotides and their derivatives, lipids, organic acids and their derivatives, terpenoids, ketones, alkaloids, etc. The results of KEGG enrichment analysis showed that strain JLS17 significantly enriched common metabolic pathways after 50 mg·L^?1 Cd²⁺ treatment and 300 mg·L^?1 Cd²⁺ treatment, including pyrimidine metabolism, aminobenzoate degradation, cysteine and methionine metabolism, tryptophan metabolism, β-alanine metabolism, folate biosynthesis and pentose phosphate pathway, among which pyrimidine metabolism, tryptophan metabolism and pentose phosphate pathway were down-regulated in common and folate biosynthesis was up-regulated in common. Conclusion: 1) The strain JLS17 has excellent adaptability to Cd²⁺ stress and can remove Cd²⁺ from LB medium effectively, showing good potential for application in remediation of Cd pollution. 2) The strain JLS17 can affect metabolic pathways in vivo through changes in the content of amino acids and their derivatives, nucleotides and their derivatives, lipids and other metabolites under Cd²⁺ stress, among which tryptophan metabolism, β-alanine metabolism, cysteine and methionine metabolism, pyrimidine metabolism, pentose phosphate pathway, folate biosynthesis are closely related to the Cd²⁺ tolerance of strain JLS17.

Objective: In this study, the complete mitochondrial genome of Hylurgus ligniperda was characterized and analyzed for the first time, and the phylogenetic relationships between H. ligniperda and closely related coleopteran species was reconstructed at mitochondrial genomic level. This study aims to enrich the mitochondrial genome diversity of curculionids, and facilitate molecular identification, population monitoring and control of the invasive pest species H. ligniperda. Method: The mitochondrial genome of H. ligniperda was sequenced using Illumina Novaseq 6000 platform, and was annotated and characterized based on published mitochondrial genomes of other Coleoptera species. The secondary structures of the tRNA genes were predicted using online tRNA Scan-SE 2.0 search server. Phylogenetic relationships between H. ligniperda and close related coleopterans were reconstructed using the maximum likelihood method based on mitochondrial genomes from a total of 23 species. Result: 1) The complete mitochondrial genome of H. ligniperda is a circular structure, which is 15912 bp in size and contains 37 genes, including 13 protein coding genes (PCGs), 22 tRNA genes and 2 rRNA genes, and a control region. The arrangement of all the 37 genes retains the same order and direction as the ancestral insect mitochondrial genome. 2) Nucleotide composition exhibits distinct AT-bias, with A + T content of 74.50%, G + C content of 23.80%; and the AT-skew value is 0.06, and GC-skew value is -0.24. 3) Except for the gene nad5, the other PCGs have the standard start codon ATN; and the stop codon of all PCGs is TAA or T. Except for trnS1, all tRNA genes display the secondary structures as classic clover-leaf shape. 4) Phylogenetic analysis based on mitochondrial genomes support that all the four subfamilies chosen from Curculionidae in present study are monophyletic, and they are branched as (Entiminae + ((Cryptorhynchinae + Molytinae) + Scolytinae)). Conclusion: Mitochondrial genome of H. ligniperda is conserved in structure and codon usage, and shows distinct A + T biased nucleotide composition. Phylogenetic relationships of H. ligniperda and the close relatives yielded by mitochondrial genomes are consistent with previous morphological investigations.

Objective: Taking poplar wood fiber as material, enhance the reactive sites on the fiber surface by oxidative modification, establish the multi-site network structure of hydroxyl and aldehyde groups on the fiber surface, and prepare high-strength, low-absorbent thickness expansion rate of self-bonding fiberboard, so as to achieve the whole biomass low-carbon and recyclable production and utilization. Method: The surface groups of wood fiber were oxidatively modified by sodium periodate to establish highly reactive aldehyde group network sites, and the aldehyde group content was determined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analyze (TG), and differential scanning calorimetry (DSC), which analyzed the microstructure and chemical structure of wood fiber before and after the reaction, as well as the content of different aldehyde groups. Using chemical bond cross-linking in low temperature hot pressing conditions to prepare self-glued fiberboard, to explore the mechanical properties of dialdehyde wood fibers to prepare self-bonding fiberboards and absorbent thickness expansion rate. Result: The quantitative modification of dialdehyde wood fibers can be realized by controlling the conditions of reaction time, temperature, and concentration of oxidizing agent; comparing with the original fibers, the surface roughness of dialdehyde wood fibers increased, the fiber size became shorter, and the degree of cellulose polymerization decreased, the cellulose-hemicellulose-lignin encapsulation structure was loosened, and a large number of pores were produced on the surface of wood fibers. The cellulose crystallization zone was gradually destroyed with the increase of reaction strength, and the thermal stability of dialdehyde wood fibers increased with the increase of reaction strength. The thermal stability of dialdehyde wood fibers gradually decreases with the increase of aldehyde content, which is conducive to the low-temperature hot compression molding of glueless fiberboard. Dialdehyde wood fibers can realize self-gluing through chemical bond cross-linking in the hot pressing process, the hot pressing temperature and aldehyde content of aldehyde-based wood fibers have a significant effect on the performance of the glueless fiberboards, and the self-bonding fiberboards prepared through the optimization of raw materials and process conditions have excellent mechanical properties and water resistance. Conclusion: Different aldehyde content of dialdehyde wood fibers can be obtained by controlling the reaction conditions, and the controlled modification of aldehyde groups on the surface of wood fibers can be realized; too low a temperature (50 ℃) in the self-gluing process is likely to lead to poor water resistance of dialdehyde wood fibers, and too high a temperature (125 ℃) is likely to cause the degradation of dialdehyde wood fibers, which will lead to blistering, swelling, carbonization, and decrease the mechanical properties of the fiberboards. When the concentration of sodium periodate was 0.07 mol·L^?1, the reaction temperature was 30 ℃, and the reaction time was 6 h, the aldehyde content of the wood fiber was 1.86 mmol·g^?1; at a hot pressing temperature of 100 ℃, a pressure of 20 MPa, and a hot pressing time of 5 min, the mechanical properties of the self-glued dialdehyde wood fiber boards and the water resistance of the fiber boards reached the optimum: the bending strength of 78.36 MPa, the modulus of elasticity of 10.88 GPa, the internal bonding strength of 3.88 GPa, and the water resistance of the fiber boards. The mechanical properties and water resistance of the prepared self-glued dialdehyde wood fiber boards were optimal: flexural strength of 78.36 MPa, modulus of elasticity of 10.88 GPa, internal bonding strength of 3.04 MPa, and the expansion rate of the water-absorbing thickness of 24 h was only 8.01%.

Objective: This paper is proposed to investigate the longitudinal tensile mechanical behavior of earlywood (EW) and latewood (LW) of Pinus massoniana in the hydrothermal environment, with an aim to reveal the mechanism about the softening behavior of wood at the scale of growth ring. Method: The absolute dry density of EW and LW in the 17^th growth ring of the heartwood of Pinus massoniana was measured by X-ray profile densimeter. LR-EW and LR-LW tissue sections were obtained from radial (LR) section of EW and LW, and LT-EW and LT-LW tissue sections were obtained from tangential (LT) section of EW and LW by a slide slicing machine. The microfiber angle (MFA), tensile elastic modulus, tensile strength and tensile strain rate of LR-EW, LR-LW, LT-EW and LT-LW specimens were measured by X-ray diffractometer and dynamic mechanical analysis at 30, 40, 50, 60, 70 and 80 ℃, respectively. Result: 1) The absolute dry density of LW (0.836 g·cm³) was 2.2 times higher than EW (0.388 g·cm³). At each temperature, the MFA of EW was larger than that of LW, and the MFA of specimen in the LR section was larger than that in the LT section. The MFA of water-saturated EW and LW in the LR and LT sections decreased with the increase of temperature. 2) At temperature level of 30 ℃, the tensile elastic modulus of LW in the LR section was manifested that LW was 2.1 times higher than EW, the tensile elastic modulus of LW in the LT section was manifested that LW was 3.3 times higher than EW, respectively. Among the four tissue sections, the tensile strength of LT-LW was the highest; the tensile strength of LR-LW was 2.0 times higher than LR-EW. Absolute dry density and MFA are two key factors affecting the tensile mechanical behavior of EW and LW in the LR and LT sections. 3) When the temperature rose from 30 ℃ to 80 ℃, the tensile elastic modulus and tensile strength of LR-EW, LR-LW, LT-EW and LT-LW were decreased, the decline of tensile elastic modulus and tensile strength of EW was greater than that of LW, and the decline of tensile elastic modulus and tensile strength of specimen in the LT section was greater than that of in the LR section. The tensile elastic modulus and tensile strength of LR-EW, LR-LW, LT-EW and LT-LW of the temperature of turning point was 60 ℃, which was related to the softening of lignin in the wood cell wall. 4) At each loading rate (0.5, 1.0, 2.0 N·min^?1), the tensile strain rate of LR-EW, LR-LW, LT-EW and LT-LW were decreased with the increase of temperature. At the same temperature and loading rate, the tensile strain rate of EW in the LR section was about 2.0 times higher than that of LW, the tensile strain rate of EW in the LT section was about 3.3 times higher than that of LW, respectively. When the loading rate was doubled, the tensile strain rate of specimens showed a doubling trend. Conclusion: The MFA, tensile elastic modulus and tensile strength of LR-EW, LR-LW, LT-EW and LT-LW decreased with the increase of temperature. Compared with LW, the influence of temperature on the tensile modulus and tensile strength of EW was greater. The decline of tensile modulus was inhibited by the decrease of MFA with the increase of temperature, and while the lignin softening was the main factor affecting the decrease of the tensile modulus and tensile strength in the hydrothermal environment above 60 ℃.