Objective The purpose of this study is to establish biomass and carbon storage models of Chinese fir plantations suitable for different production areas, so as to provide a basis for accurate estimation of biomass and carbon storage of Chinese fir plantations.Method Based on the measured biomass data of stem, bark, branch, leaf, and root of 109 Chinese fir trees in Sichuan, Guangxi, Jiangxi, and Fujian, and the measured biomass and carbon content of stem, branch, leaf, and root of 40 Chinese fir trees in Sichuan, Guangxi, and Fujian, the additive biomass and carbon storage models of mature forests in different production areas, different forest ages, and comprehensive production areas were established. The seemingly unrelated regression (SUR) is used to jointly estimate the parameters in the additive model system, and the fitting accuracy of the model is tested with the adjusted determination coefficient R²_a, and the total relative error TRE.Result 1) The R²_a of the fir biomass models for the four production areas and different stand ages ranged from 0.635 0 to 0.995 8, with TRE ranging from ?17.88% to 21.39 %, and the R²_a of the stem, bark, and whole plant biomass models were above 0.91, which is suitable for biomass prediction of fir plantation forests in the modeled sites. The biomass models fitted to Guangxi sub-lateral roots had R²_a above 0.80 and TRE of ?5.42% to 7.21%, except for the first-grade lateral roots, which can be used to predict the biomass of lateral roots in Guangxi fir plantation forests. The biomass model fitting accuracy of branches, leaves, and roots was lower than that of stem and bark. 2) The carbon stock model R²_a was from 0.805 0 to 0.994 0 and TRE was from ?19.34% to 19.84% for the three production areas of Sichuan, Guangxi, and Fujian, and the R²_a of the stem, root, and whole plant models was above 0.93, which applied to the prediction of carbon stock in cedar plantation forests in all regions. The carbon stock model fitting accuracy of branches and leaves was lower than that of stem and roots. 3) There are differences in the accuracy of the biomass and carbon stock models across different regions. The biomass model of Sichuan, located in the western part of the central subtropics, has the lowest accuracy. On the other hand, the biomass model of Guangxi, located in the southern subtropics, with the skinned stem and the whole-plant biomass model, has better accuracy. Additionally, the biomass models of Fujian and Jiangxi, located in the eastern part of the central subtropics, have similar accuracy and can be used interchangeably. Regarding the carbon stock models, the one in Guangxi has the highest accuracy, whereas the ones in Sichuan and Fujian are only suitable for predicting the carbon stock in their respective regions. 4) The comprehensive biomass model R²_a is 0.733 5?0.966 9. According to the results of the cross-test, the comprehensive model can accurately predict the biomass of stem with bark and the whole plant of mature forests in different production areas, young forests, and middle-aged forests in Fujian, and the TRE is ?10.47%?19.88%. It can also accurately predict the biomass of organs and whole plants except branches of mature forests in Jiangxi, Fujian, and middle-aged forests in Fujian. The comprehensive carbon storage model R²_a is 0.802 9?0.982 6. Except for the relatively large prediction error of branch carbon storage of Chinese fir plantations in Guangxi, the TRE of other test samples is ?9.57%?15.70%, indicating that the model has good universality and can accurately predict the carbon storage of various organs and whole plants of Chinese fir plantations in different production areas.Conclusion The models established in this study apply to the prediction of biomass and carbon storage in the modeling site. The universality of the model is affected by the difference in production areas. The integrated model can be used to predict biomass and carbon storage in different regions.

Objective To study the differential responses of nitrogen contents（NCs） of new branches and leaves (NBL), above-ground biomass increment (AGBI), and nitrogen use efficiency (NUE) of the 3 dominant species in 3 typical forest communities of Larix principis-rupprechtii forest , Betula platyphylla forest and Hippophae rhamnoides forest to different soil nitrogen addition gradients in Guandishan Forest Region. The objectives are: elucidate the different functional characteristics and nitrogen use strategies, and improve the growth of the forests and precision forest management with the increasing global nitrogen deposition. Method Five levels of soil nitrogen addition (0, 9, 18, 27, 36 g·m^?2a^?1) experimentation were implemented in field to compare the responses of nitrogen contents of new branches and leaves, above-ground biomass increment, and nitrogen use efficiency to the different soil nitrogen supplements, and linear models were used to simulated the changes of above-ground biomass increment, nitrogen contents and nitrogen use efficiency with the increment of the soil nitrogen additions. The effective pathway of soil nitrogen addition to above-ground biomass increment in the 3 forest communities was explored by constructional equation model analysis.Result The nitrogen contents of new branches and leaves of the 3 dominant species were totally presented as L. principis-rupprechtii > B. platyphylla > H. rhamnoides. The nitrogen contents of new branches and leaves in July were higher than those in September, and were all increase with nitrogen addition gradient. The differences sequence of the nitrogen contents of new branches and leaves in 3 dominant species between the two growth stages are B. platyphylla>L. principis-rupprechtii > H. rhamnoides. The sequence of the saturated soil nitrogen addition and saturated soil nitrogen contents for the nitrogen contents of new branches and leaves of the 3 forest communities are all L. principis-rupprechtii <B. platyphylla < H. rhamnoides. The new biomass of the 3 forest communities were all increased with increasing soil nitrogen addition, but the response patterns and increasing rates were significantly different as L. principis-rupprechtii > H. rhamnoides > B. platyphylla. The nitrogen use efficiency of the 3 forest communities decreased with increasing soil nitrogen addition, and the decrease sequence was L. principis-rupprechtii> B. platyphylla > H. rhamnoides. And there also decreased with the increase of nitrogen contents in branches and leaves in the 3 forest communities by the decreasing sequence of B. platyphylla > L. principis-rupprechtii??????? > H. rhamnoides. Dominant species and community type determined by community composition directly effected the nitrogen storage in new biomass and community nitrogen use efficiency, also secondly effected by the soil nitrogen additions, and furthermore positively driving the new biomass accumulation in the community. Conclusion The new biomass increment of the three forest communities was mainly determined by the community type and its dominant species but directly affected by the nitrogen use efficiency of the dominant species and the nitrogen contents of the new branches and leaves both regulated by the soil nitrogen supply. Differential nitrogen use strategies of the three communities could be indicated by nitrogen requirement, nitrogen use efficiency, nitrogen sensitivity, and saturated nitrogen supply comprehensively. The three nitrogen use strategy types are in turn: “low demand - high efficiency-high sensitivity - low saturation”, “low demand - low efficiency- high sensitivity - low saturation” and “nitrogen fixing - high demand -low efficiency-low sensitivity-high saturation”. There could provide the principles for the dominant tree species selection, composition regulation and stand site cultivation in precise forest management under different nitrogen deposition scenario or soil nitrogen contents.

Objective This study aimed to explore the water quality characteristics and changes of surface water and groundwater in forested watershed, and provided an important reference for combating regional environmental changes and the development of the ecological environment. Method This study took the Donggou watershed in Dinghushan National Reserve as the object, and relied on the long-term observation of the water quality in flowing surface water and shallow groundwater in the watershed based on the monitoring specification of forest water environment issued by the Chinese Ecosystem Research Network.Result The results showed that during the study period (2005—2018), the precipitation in the Dinghushan watershed was weak acidic (pH: 5.85±1.10). Compared with the acidity in precipitation, surface water showed significant acidification (4.76±0.58, P<0.01), while groundwater had a certain degree of improvement of acidity. On the whole, the salinity in precipitation was lower , and salinity in groundwater was significantly higher than that in precipitation and surface water in both dry and wet seasons (P<0.01). The long-term measurement of dissolved oxygen and chemical oxygen demand also showed that anthropogenic pollution of surface water and groundwater was low, and the water quality was good. Through the comparative analysis of the main ion content, it was found that the Na⁺, K⁺, Ca²⁺, Mg²⁺, SO₄^2?, and Cl^? in groundwater were significantly higher than the corresponding ion content in surface water (especially the Ca²⁺ and K⁺), while the content of NO₃^? in groundwater was significantly lower than that of surface water (P<0.05). In addition, the study also found significant difference in the content of SO₄^2? in groundwater between dry and wet seasons (P=0.03), while the inter-seasonal differences of other ions were not significant.Conclusion The quality of surface water and groundwater in the well-protected Dinghushan forested watershed was good, which can be used as a reference for the management of the water environment in this area.

Objective This study aims to investigate the effects of exogenous calcium addition on soil CO₂ emission and soil carbon pool of organic amendment in improving coastal saline-alkali soil, so as to provide the theoretical basis for the improvement and utilization of coastal saline-alkali soil and the enhancement of carbon sequestration potential. Method In an indoor incubation experiment, the corn straw biochar + chicken manure (BM), and rice straw + chicken manure (SM) were respectively applied to the coastal saline-alkali soil. Calcium hydroxide and calcium silicate were used as calcium sources. Six treatments were established according to the principle of equal calcium content: no exogenous calcium application (CK), 12.4 g·kg^?1 calcium silicate application (Ca1), 24.8 g·kg^?1 calcium silicate application (Ca2), 7.9 g·kg^?1 calcium hydroxide application (Ca3), 15.8 g·kg^?1 calcium hydroxide application (Ca4), 12.4 g·kg^?1 calcium silicate and 7.9 g·kg^?1 calcium hydroxide application (Ca5). All the calcium concentrations were added to the soil, and the incubation experiment lasted for one month. Result The results showed that the addition of exogenous calcium significantly reduced cumulative CO₂ emission during the incubation period. The application of organic amendments led to the loss of SOC (soil organic carbon), while exogenous calcium addition did not significantly affect SOC mineralization but significantly increased SIC (soil inorganic carbon) content, thereby compensating for the loss of SOC and increasing the total carbon content in the soil, achieving the goal of soil carbon sequestration. Proper increase in the amount of calcium hydroxide was able to promote carbon sequestration. The emission reduction was mainly achieved by increasing the absorption of CO₂ produced during mineralization and converting it into the form of calcium carbonate for fixation. Conclusion The above results indicate that the combination of organic amendments with calcium silicate and calcium hydroxide can effectively achieve soil carbon sequestration and emission reduction during the improvement of saline-alkali soil.

Objective The study was intended to explore the response difference of nutrient limitation of typical urban ornamental tree species along the urban and rural environmental gradients, in order to provide a scientific basis for nutrient management of urban forest ornamental tree species under urbanization. Method The mature and defoliated leaves of typical ornamental tree species Acer truncatum and Syringa oblata were collected along the urban-suburban-rural gradients of Beijing in summer and autumn, respectively. Six leaf functional traits (leaf fresh weight, leaf dry weight, leaf area, specific leaf area, leaf mass per unit area and leaf water content) and the contents of six elements [carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg)] were determined. The stoichiometric ratio and nutrient resorption efficiency were calculated. The differences of leaf functional traits, eco-stoichiometric characteristics and nutrient resorption efficiency between Acer truncatum and Syringa oblata were compared. The correlations of environmental factors such as mean annual temperature, mean annual precipitation and mean annual solar radiation with leaf functional traits, eco-stoichiometric characteristics and nutrient resorption efficiency of Acer truncatum and Syringa oblata were analyzed. Result Leaf functional traits, element content and stoichiometric ratio had significant response to urbanization, and there were interspecific differences. In mature stage, along the gradients from the urban area to the rural area, the leaf fresh weight, leaf dry weight, leaf area, specific leaf area and leaf water content of Acer truncatum and Syringa oblata increased as a whole, while the leaf mass per unit area decreased. During the abscission period, the leaf fresh weight and leaf dry weight of Acer truncatum decreased gradually along the gradients between the urban area and the rural area. The leaf dry weight and leaf mass per unit area of Syringa oblata increased at first and then decreased along the gradients from the urban area to the rural area, while the leaf area decreased gradually. The specific leaf area of defoliated leaves of the two tree species decreased at first and then increased along the urban and rural gradient. At mature stage, the N and K contents of Acer truncatum and Syringa oblata in the suburban gradient were lower than those in the urban and rural gradients. The P and Mg contents of mature leaves of Acer truncatum did not change significantly in the urban and rural area, but the P and Mg contents of mature leaves of Syringa oblata in the suburban area were significantly higher than those in the urban and rural gradient. During the defoliation period, the P and Mg contents of Acer truncatum had no obvious change along the gradients between the urban area and the rural area, while the P content of Syringa oblata in the suburban gradient was significantly higher than that in the urban and rural gradients, and the Mg content in the rural area was significantly lower than that in the urban and suburban areas. In defoliating stage, the K content of Acer truncatum and Syringa oblata decreased at first and then increased in the urban and rural areas. There was no significant difference in nutrient resorption efficiency of N, P, K, Ca and Mg between the two tree species along the urban and rural gradients. Conclusion Urbanization leads to smaller leaves of Acer truncatum and Syringa oblata. The growth of Acer truncatum and Syringa oblata were restricted by N, while Acer truncatum in the urban gradient and Syringa oblata in the rural gradient had stronger drought tolerance. The resorption efficiency of K, Ca and Mg of the two tree species in different gradients was lower than the global average, and the element resorption ability of Acer truncatum was stronger than that of Syringa oblata. Compared with leaf nutrient content and nutrient resorption efficiency, leaf functional traits were more closely related to environmental factors.

Objective In order to fully develop and utilize the economic value of Pteroceltis tatarinowii and open up new resources of feed production, the nutritional value of P. tatarinowii leaves for feeding was comprehensively analyzed and evaluated, so as to provide data support for P. tatarinowii to be used as woody feed.Method In this study, the nutritional components, antioxidant activities, components and contents of secondary metabolites and amino acids in leaves of 10 clones were determined, and their feeding characteristics were comprehensively evaluated by quality evaluation indexes.Result 1） There were extremely significant differences in different nutritional indicators of leaves among different clones of P. tatarinowii. Crude protein content ranged from 10.15% to 24.36%, with an average of 17.60%, and among the clones 'Fuyuan' (24.36%) and 'WT' (24.33%) had the highest content. Crude fat ranged from 7.98% to 11.45%, with an average of 9.31%. The crude fiber content was low, with an average of 4.08%. The average value of nitrogen-free extract was 49.69%. The difference of neutral detergent fiber among clones was the greatest, ranging from 17.76% to 67.67%, with an average of 45.51%. The difference of acid detergent fiber was small, with an average of 24.07%. The average total phosphorus content and calcium content were 0.1733% and 5.8633%, respectively. Tannin content was far lower than the standard of antifeeding, with an average of 2.9260 g·kg^?1. 2）There were significant differences in the evaluation indicators of feed quality among clones, and 4 out of 10 clones reached the level 1 standard of AFGC, namely 'WT', 'Jinyuyuan', 'Huiguang' and 'Julong'. 3) The antioxidant activity composite index (APC) showed that leaves of 'Daye', 'Julong' and 'Qinglong' had strong antioxidant capacity, while leaves of 'Wuliang', 'Jinyuyuan' and 'Huiguang' had weak antioxidant capacity. 4) There were significant differences in total flavonoids and five flavonoid substances in the leaves among clones, which provided the basis for screening high bioactive substances. The average content of total flavonoids was 9.92 mg·g^?1. The content of chlorogenic acid was the highest (710.96 μg·g^?1), followed by isorhamnetin (27.12 μg·g^?1), catechin (16.53 μg·g^?1) and quercetin (9.09 μg·g^?1). The caffeic acid content was very low, only 1.73 μg·g^?1. 5) A total of 18 kinds of free amino acids and 19 kinds of hydrolyzed amino acids were detected, with an average total amount of 47.87 mg·g^?1 and 108.20 mg·g^?1, respectively. And the total contents of the two kinds of amino acids were significantly different among clones. The contents of isoleucine and leucine were the highest in the two kinds of amino acids. Conclusion The leaves of P. tatarinowii have high content of crude protein, crude fat and calcium, and low content of crude fiber, neutral detergent fiber, acid detergent fiber and tannin, and the comprehensive grade of feeding evaluation index has reached grade 1 standard. It is concluded that P. tatarinowii has the material foundation to develop into an elite woody fodder species. Three elite clones, 'WT', 'Fuyuan' and 'Julong', have been selected preliminarily.

Objective In this study, the growth and physiological responses of walnut seedlings with different genotypes to salt stress were studied, and their salt tolerance was comprehensively evaluated, which would provide reference for screening salt-tolerant varieties in saline-alkali areas.Method Seedlings derived from 4 genotypes of Juglans regia ‘Xinxin2’ (JX2), J. regia ‘Wen185’ (JW185), J. regia ‘Zha343’ (JZ343), and J. regia ‘Liaoning1’ (JL1) were used as test materials, and subjected to five NaCl concentration gradients (0, 50, 100, 200 and 300 mmol·L^?1). The photosynthetic parameters, membrane permeability, osmotic adjustment substances, enzyme activity and endogenous hormone content of the four genotypes were measured for different days (6, 12, 18 and 24 days), and the salt tolerance of the four genotypes was comprehensively evaluated.Result 1) Under salt stress, the growth of seedlings of four genotypes was affected to different degrees, and the leaves of all genotypes showed different degrees of salt damage symptoms, such as yellowing, curling and shedding. The growth indexes such as seedling height increment, ground diameter increment and plant dry weight showed a downward trend with the increase of NaCl concentration. Among the 4 genotypes, JX2 grew relatively better and was less inhibited. 2) With the increase of salt concentration and the prolongation of stress time, the chlorophyll content and photosynthetic parameters of each genotype generally showed a downward trend, and JX2 showed a smaller decline than the control, and performed better. 3) With the increase of salt concentration and the prolongation of stress time, relative electrical conductivity (REC) and malondialdehyde (MDA) content showed an overall upward trend. Among the 4 genotypes, JX2 had lower the REC value and MDA content, with a smaller increase compared to the control, while JZ343 was the opposite. 4) With the increase of salt concentration and the prolongation of stress time, proline (Pro) content generally showed an upward trend, soluble sugars (SS) and enzyme activities showed an overall increase followed by a decrease. Among the 4 genotypes, JX2 accumulated more Pro and SS, and had higher enzyme activity. 5) In terms of endogenous hormones, salt stress promoted the production of abscisic acid (ABA) and inhibited the synthesis of indole-3-acetic acid (IAA). Conclusion Salt stress significantly affects the growth and photosynthesis of walnut seedlings, by reducing the photosynthesis activity of leaf cells. Seedlings can cope with salt stress by increasing the content of osmotic adjustment substances, improving enzyme activity and regulating their endogenous hormone balance. The comprehensive evaluation of salt tolerance indicates the following order of magnitude of salt tolerance among the four genotypes: JX2 > JW185 > JL1 > JZ343.

Objective Distant hybridization is an important way for germplasm innovation which can achieve the aggregation of favorable genes. Cross-incompatibility often occurs in some of Populus sects, and interspecific hybrids are difficult to distinguish from its morphology. In this study, species-specific InDel markers were developed to identify the interspecific hybrids from different sects of Populus, so as to lay a foundation for the new germplasm innovation in poplar. Method The primers were developed from species-specific InDel sites in P. deltoides and P. simonii and were used to blast sequentially the genomes of P. euphratica, P. davidiana, P. simonii and P. lasiocarpa using SeqHunter2. Natural individuals from different sects were used to verify the species-specific primers in intra species conservation and inter species polymorphism by PCR amplification test, and the identified species-specific primer sequences for different sects of Populus were screened, and the authenticity of interspecies hybrid progenies among any combinations from the five species in different Populus sects was identified.Result Five thousands of InDel primers were designed from the genome of P. deltoides and used to blast sequentially the genomes of P. euphratica, P. davidiana, P. simonii and P. lasiocarpa. A total of 341 primer pairs were detected as universal markers among the five species. A total of 48 primer pairs from different chromosome were selected and synthesized, and 43 were identified as universal in five species from different sects, of which 19 primer pairs were conservative within individual species and produced length polymorphism of amplified bands in different species. The mixed DNA from natural population was used to test the 19 pairs of universal primers for interspecific polymorphism and intraspecific conservation by PCR amplification, and 4 pairs of polymorphic primers were preliminarily obtained. Finally, natural population DNA was used to amplify and detect these 4 pairs of primers, and it was found that primer pairs of Chr12_4341229 and Chr13_10582756 were species-specific, and could be used to amplify clear and unique bands in P. deltoides, P. simonii, P. davidiana, P. lasiocarpa and P. euphratica. Primer pairs of Chr12_4341229 could be used to amplify the bands with length of 148, 152, 113, 152 and 159 bp, and primer pairs of Chr13_10582756 could be used to amplify the bands with length of 140, 144, 116, 140 and 159 bp separately in the species of P. deltoides, P. simonii, P. davidiana, P. lasiocarpa and P. euphratica. Primers Chr12_4341229 and Chr13_10582756 were used to identify the inter-specific hybrids of P. simonii × P. euphratica, P. deltoides × P. euphratica, and P. deltoides × P. simonii, showing that all the three inter-specific hybrids could amplify two bands which were inherited from the parents used for hybridization. The above two primers were able to be used for verifying the authenticity of progenies from any combination of the five species in different Populus sects.Conclusion In this study, two pairs of species-specific InDel markers have been identified conservative within species and with length polymorphism in the five species from different Populus sects, and can be used to identify inter-specific hybrids from any combination among the five species in Populus. The development of the two species-specific InDel markers will provide technical support for the further germplasm innovation by distant hybridization in Populus.

Objective UFO is the first F-box protein discovered in angiosperms, and plays a role in determining floral meristem identity and floral organ growth. In this study, the expression profile and heterologous expression phenotypic traits in A. thaliana were analyzed to explore the gene function of CpUFO and provide a basis for molecular mechanism of floral development in wintersweet (Chimonanthus praecox). Method Based on the constructed transcriptome data of C. Praecox, the CpUFO gene was cloned and the sequence alignment of its encoded protein and phylogenetic analysis were conducted. Quantitative real-time RT-PCR (qRT-PCR) was performed to identify transcript level of CpUFO in different tissues, organs and annual flower buds in different flower development stages. The effects of CpUFO on flowering time and flower organ development of Arabidopsis thaliana were explored by analyzing the phenotypes and relative gene expression of endogenous flowering related gene between the 35S∷CpUFO transgenic Arabidopsis lines and the wild type. Result The obtained cDNA of CpUFO gene was 1 655 bp in full-length, encoding a protein of 403 amino acids residues with highly conserved F-box domain. The expression level of CpUFO was relatively highest in the outer tepal, followed by the inner tepal, and the expression level was lower in fruit, stem, leaf, axillary bud and stamen. Transcript level of CpUFO in annual flower buds showed that relative expression of CpUFO in flower buds of display tepals (DT), initial blooming (IB) and open flower (OF) stages after chilling-induced dormancy breaking was obviously higher than that in the other developmental periods. Compared with Arabidopsis Col-0, 35S::CpUFO transgenic Arabidopsis lines had less rosette leaves and early flowering. Moreover, the endogenous genes of AP1 and FUL in A. thaliana were significantly up-regulated, while TFL1 was significantly down-regulated. Conclusion CpUFO is expressed in different tissues, organs and annual flower buds, and the highest relative expression level is found in the outer tepals and flower buds of open period after dormancy breaking. Meanwhile, overexpression of CpUFO promotes early flowering in Arabidopsis and affects its floral organ development．

Objective When using convolutional neural network models for automatic image recognition, a large number of training samples are usually required to prevent model overfitting. In this study, we propose a tree species recognition method that fuses generative adversarial networks with convolutional neural networks to improve the accuracy of tree species recognition and expand the image samples based on the original leaf images to ensure the training quality.Method Under the framework of Pytorch, images of the leaves of 10 common tree species (aspen, ash maple, house elm, locust, clove, eucommia, torch tree, mountain wattle, ash willow, red endosperm) were collected as research objects. First, the images were pre-processed using mean filter denoising and size normalization. Second, the datasets are expanded with images generated by generative adversarial network, in which the residual conditional deep convolutional generative adversarial network (RC-DCGAN) model is built based on and improved by the deep convolutional generative adversarial network (DCGAN) model, which takes random noise and category labels as the input of the generator to control the sample generation process; the residual structure is embedded in the generator so that the generative model learn more feature information to improve the quality of the generated images. Then, the original and augmented images are used as the training set of the convolutional neural network (CNN). On the one hand, 11 400 images were expanded using the RC-DCGAN model and traditional image expansion methods such as rotation, mirroring, and changing contrast, respectively. On the other hand, the original and generated images, the original and traditional expanded images were inputted to the CNN for training, and 50 images in each category of the original images were randomly selected to test the model to verify the feasibility of the generative adversarial networks to improve the recognition accuracy. Finally, the CNN classification model suitable for the experimental requirements are determined and compared with the recognition effect of AlexNet model, VGG-16 model, VGG-19 model and ResNet18 model to test the feasibility of the method in this study.Result The RC-DCGAN model generates higher quality images than the DCGAN model, which fit the real image; the training accuracy is 99.03% and the average validation recognition accuracy is 97.20% using the generative adversarial network augmented image method with the ResNet30 tree recognition model; while the recognition rate of the traditional image augmentation method is 95.50% under the same tree recognition model; under the same dataset, the recognition rates obtained by AlexNet model, VGG-16 model, VGG-19 model, and ResNet18 model were 86.52%, 87.57%, 91.43%, and 93.25%, respectively, which were lower than that of the models in this study.Conclusion The method of combining generative adversarial network and convolutional neural network has the highest recognition accuracy for the leaf images of 10 tree species in this study, which overcomes the problem of decreasing the generalization ability of the model by using the traditional image processing augmentation method, and shows that the method of image amplification by generating adversarial network is feasible and effective, which can provide reference significance for related research work.

The decomposition of woody debris is an important part of the forest carbon cycle, and microorganisms are the key factor influencing its decomposition rate. In recent years, the mechanisms of microbial community building in woody debris have gradually become an important topic in the study of carbon cycling in forest ecosystems. However, current microbial research on woody debris is fragmented. Hence, this paper reviews the formation mechanism of woody debris microbial communities. 1) Microorganisms maintain a dynamic balance of communities by continuously colonising woody debris. The microbial sources of woody debris mainly stem from the debris itself, the atmosphere and the soil. The colonization process occurs at all stages of decomposition and consists mainly of competition and resource capture that occurs when microorganisms colonizing the substrate. 2) Soil, properties of woody debris and climate are three important factors influencing the formation of microbial communities of woody debris, all of which act on the microbial sources and the colonisation process. 3) The soil environment affects the soil microbial community and changes the properties of the debris with which it comes into contact. Differences in woody debris properties affect the availability of resources and thus the microbial community. As decomposition proceeds, microbial community assembly changes from an initial dominance of stochastic processes to a dominance of deterministic processes. Climate affect the soil and woody debris through both temperature and humidity climate factors, mainly in the form of macroclimate, microclimate and global climate change. Finally, the paper summarised the issues that need to be addressed in future research in this area and identifies the need to: 1) focus on the impact of early colonizers and soil microorganisms at different stages of decomposition on the microbial community of woody debris; 2) strengthen the study of changes in woody debris resources and the function of the dominant species in the corresponding microbial community; 3) link woody debris decomposition to global climate change and nutrient cycling; 4) select more precise techniques for the decomposition of woody debris. In summary, this paper summarised the basic ideas, framework and prospects for the study of microbial community formation mechanisms in forest woody residues, providing certain scientific references for forest biodiversity conservation, maintenance of biogeochemical cycle functions and forest carbon sequestration.

Wood archaeology research is an important basis to promote the natural and historical information mining, protection and restoration of wood relics. In recent years, with the rapid development of ancient DNA hybridization capture and sequencing technologies, it has become possible to obtain sequence information of highly degraded DNA fragments from woody remains. On the basis of wood anatomy, the innovative research on wood molecular archaeology with ancient DNA as the core has gradually become the focus and frontier of attention in wood archaeology. Therefore, this paper firstly reviews the research of the wood molecular archaeology, and then summarizes the research progress and problems of wood ancient DNA from three aspects: preservation and degradation, acquisition, data processing and sequence analysis. It also points out that the high degradation, low concentration, and chemical damage of ancient DNA make it difficult to extract and analyze. Then it summarizes the main applications of wood molecular archaeology in interpreting the ways of ancient people’s cognition and utilization of forest resources, restoring regional forest vegetation types and species diversity in historical periods, and reconstructing the microevolutionary responses of ancient trees to climate and habitat changes. Finally, we proposed three research topics which should be given priority in future: 1) establishment of the specimen collections of archeological woods and the corresponding DNA database. 2) Studying the laws of wood ancient DNA damage and its changes in different spatial and temporal dimensions. 3) Development of the stable and efficient technical system for extracting and analyzing wood ancient DNA. By further strengthening the interdisciplinary research of wood molecular archaeology, the application of new theories, methods and technologies in the field of wood science and archaeology is promoted, so as to provide scientific basis for the species identification, protection and utilization of wood cultural relics, and the reconstruction of the coupling relationship between forest vegetation, environmental climate and human activities in the historical period.

Hydrogels are 3D network structure material formed by physical or chemical cross-linking of hydrophilic polymers. It usually has the characteristics of hydrophilicity, viscoelasticity, biocompatibility, etc., and is widely used in bioengineering, flexible electronics and other fields. Traditional hydrogels generally use fossil-based polymers as raw materials, and there are potential threats to the human body and the environment during the use of hydrogels and the recycling of waste hydrogels. At the same time, the traditional hydrogel will be damaged due to the action of mechanical external force after a long time of use, and its structural integrity and performance will be affected. Hydrogels with self-healing ability can recover to almost the same mechanical properties as the initial state after breakage using supramolecular interactions or reversible covalent interactions, which is of great significance for prolonging the service life of hydrogels. Cellulose is a kind of natural organic polymer, with non-toxic, harmless, good biocompatibility and other advantages, mainly from natural materials such as trees in nature, in line with the concept of green environmental protection, has broad application prospects. The abundant oxygen-containing groups in cellulose chain can form hydrogen bond network with water, which is conducive to the preparation of hydrogels with self-healing ability. And by chemically modifying cellulose to obtain cellulose derivatives, such as carboxymethyl cellulose, hydroxyethyl cellulose, etc., its application in the field of hydrogels can be expanded. This paper comprehensively introduces a class of self-healing hydrogels using cellulose and cellulose derivatives as raw materials, analyzes the shortcomings of traditional self-healing hydrogels, and proposes related modification strategies. Cellulose is difficult to dissolve in water due to its own crystal structure and internal supramolecular interactions, so cellulose hydrogels are generally prepared by using a dispersion system or a dissolving system. By regulating the three-dimensional structure of the hydrogel, reversible covalent interactions (acylhydrazone bond, disulfide bond exchange, etc.) and non-covalent interactions (hydrogen bonding, hydrophobic interaction, host-guest interaction, etc.) are used to endow the hydrogel with self-healing ability. Due to the existence of such reversible cross-linking, the general mechanical properties of traditional cellulose self-healing hydrogels are poor. At the same time, the functional development of cellulose self-healing hydrogels is relatively simple at present, which limits its application in various fields. Therefore, by introducing the construction of intelligent network structure, biomimetic natural biological wound healing mechanism and functional modification methods, this paper proposed a new multi-functional intelligent cellulose self-healing hydrogel construction method. Finally, combined with the relevant research results of self-healing hydrogels, the problems that still need to be solved at the present stage of cellulose self-healing hydrogels are put forward, and the application prospect of cellulose self-healing hydrogels in the fields of bioengineering, electronic materials and intelligent materials is forecasted.