Forest carbon sinks are not "a drop in the bucket", but a tool of national importance, the forest carbon sink and its contribution to carbon neutrality have become a global consensus. The formation, promotion, monitoring, measurement, verification, and trading of forest carbon sinks have become an important field of scientific research and social development. Firstly, the characteristics of the human-carbon relationship during the course of human civilization were explored. Secondly, some basic problems in the whole chain of forest carbon sinks are discussed, including the impact of forest definition on carbon sink measurement, carbon source-sink conversion in forests, the boundary of carbon sink measurement, the monitoring, reporting, and accounting of carbon sink, as well as the basic requirements of carbon sink project development and carbon sink trade. etc. The challenges, potential, and paths of forest carbon sink enhancement in China also were analyzed in this review, and it is believed that we should further strengthen the construction of scientific and technological innovation systems for forest carbon sequestration to better understand the carbon sequestration mechanism in the process of ecological restoration, forest management, and forest utilization. It is necessary to further optimize the design and application of social institutions and rules, technologies, and cultural systems related to the carbon cycle of forest ecosystems, to support the implementation of the national "carbon peaking and carbon neutrality" strategy and the development of ecological civilization.

Consolidating and enhancing the carbon sink capacity and potential of terrestrial ecosystems is an important approach to mitigate the rise of carbon dioxide concentration and climate warming, and it is also one of the main ways to achieve China’s goal of “carbon neutrality”. To comprehensively understand the carbon sink of China’s terrestrial ecosystems and scientifically make the implementation pathways and action plans for the “carbon neutrality” goal, this review summarized the research progress on carbon sinks in the forest, shrub, grassland, desert, wetland, and farmland ecosystems, and the challenges and pathways to enhancing carbon sink in China’s terrestrial ecosystems. In the past 40 years, China’s terrestrial ecosystems have become an important carbon sink with obviously spatiotemporal difference in carbon sink intensity. The intensity increased from 0.17 Pg·a^?1 (1 Pg = 1×10¹⁵ g) during 1980—2000 to 0.20 Pg·a^?1 during 2001—2010, and is expected to reach 0.46-0.49 Pg·a^?1 during 2050—2060. The overall carbon sink intensity in eastern and southern China is higher than that in western and northern China. The carbon source/sink characteristics of various subsystems of China’s terrestrial ecosystems are also different: forests are the major carbon sink, while shrubland, wetland, and farmland have carbon sink trends, however, whether the grassland and desert have the carbon source or sink characteristics remains unclear. Overall, China’s terrestrial ecosystem has a huge potential for carbon sink in the future but there are great uncertainties. It mainly faces three types of challenges: the ecological space is limited, the carbon sequestration capacity urgently needs to be improved, and the policy mechanisms and supporting measures need to be further improved. In the future, we should carry out an in-depth study on carbon sinks of China’s terrestrial ecosystems from the following four aspects: 1）optimizing layouts of ecological spaces and scientifically implementing ecological restoration; 2）further understanding the formation mechanisms of carbon sink and improving the carbon sequestration capacity; 3）strengthening the capacity construction in investigation, monitoring, accounting and standards specification of ecosystem carbon sinks, and 4）exploring the mechanisms and pathways for realizing the value of ecological carbon sink products.

Objective: Developing growth models of carbon storage in tree layers for five major plantation types in China, i.e., Chinese fir, popular, eucalyptus, larch, and masson pine, determining the stand age with maximum average carbon growth, and analyzing difference of and climate effect on carbon sequestration capacity would provide scientific basis for increasing carbon sequestration capacity of plantations and decision-making of sustainable forest management. Method: Based on the carbon storage data of 8 520 sample plots from the 9^th national forest inventory of China, the growth models of carbon storage in tree layers for five major plantations were developed through using weighted nonlinear regression method and variable parameter model, the impacts of two climate factors, i.e., mean annual temperature (MAT) and precipitation (MAP), to model parameters were analyzed, and the difference of carbon sequestration capacity in tree layers among five plantations was compared. Result: The mean prediction errors of growth models of carbon storage in tree layers for five types of plantations developed in this study are less than 5%, and total relative errors are all less than 3% for both calibration and cross-validation. The mean carbon growth of larch, masson pine, Chinese fir, popular, and eucalyptus plantations reach to the highest 1.50, 1.85, 2.10, 2.96, 6.97 t?hm^?2, respectively at 24, 16, 12, 6, and 2 years old of stand age. Comparison to larch plantation, the highest mean carbon growth in tree layers of masson pine, Chinese fir, poplar and eucalyptus plantations are 1.23, 1.40, 1.97 and 4.65 times, respectively. The models were used to analyze the influence of climate factors on carbon storage in tree layers. The results showed that 1 ℃ decrease in MAT could result in 7.6%, 4.5%, 4.0% and 3.0% decrease of annual mean carbon growth for popular, masson pine, eucalyptus, and larch plantations, respectively; and 100 mm decrease in MAP could result in 5.8% decrease of annual mean carbon growth for larch plantation, but increase in some extent for poplar and eucalyptus plantations. Conclusion: The carbon sequestration capacity in tree layers of major five types of plantations was successively eucalyptus, popular, Chinese fir, masson pine and larch, which was affected by MAT and MAP to varying degrees. The most significant effect is to poplar plantation, followed by larch, Masson pine and eucalyptus plantations, but there is no significant effect to Chinese fir plantation. To maximize the carbon sequestration potential of plantations in China, we need to determine reasonable management cycle referring to the growing process of carbon storage, and do efforts for developing eucalyptus and poplar plantations based on balancing regional development.

Objective: Long-term forest CO₂ fluxes measured by eddy covariance(EC) were rarely validated with ground monitoring of carbon processes, which limited the understanding for the estimate accuracy of temperate forest carbon sink. This study mainly determined the long-term CO₂ fluxes and ground carbon processes and their uncertainties in a temperate secondary forest in northeast China. Method: Based on the CO₂ flux measurements of the typical temperate secondary forest at the Maoershan site over 11 years (2008—2018) via the EC method, we calculated the CO₂ fluxes and its uncertainty with site-specific approaches of data analysis; Based on 12 years’ inventory measurements during 2008—2019, we systematically estimated the net primary productivity(NPP) and net ecosystem production(NEP) and their uncertainties, and compared the CO₂ fluxes estimates between the two methods. Result: 1) Based on the EC method, the mean net ecosystem exchange(NEE), gross primary production(GPP), and ecosystem respiration(R_e) of the stand over the 11 years were ?1.57 ± 0.64, 13.56 ± 1.48, and 12.00 ± 1.38 t?hm^?2 a^?1, respectively; of which the corresponding uncertainties were 0.47, 0.90 and 1.37 t?hm^?2 a^?1, and the relative uncertainties were 29.9%, 6.6% and 11.4%. 2) Based on the inventory method, the total NPP of ecosystem was 7.54 ± 1.31 t?hm^?2 a^?1. The NPP of total litterfall and total woody tissues were 2.32 ± 0.14 t?hm^?2 a^?1 and 2.36 ± 0.14 t?hm^?2 a^?1, respectively, accounted for 30.8% and 31.3% of the total NPP, respectively. The understory NPP was 0.39 ± 0.04 t? hm^?2 a^?1, only accounted for 5.2% of the total; of which the NPP of shrubs and herbs were 0.08 ± 0.02 t?hm^?2 a^?1 and 0.31 ± 0.03 t?hm^?2 a^?1, respectively. The fine root NPP was 2.47 ± 1.29 t? hm^?2 a^?1, which was the largest fraction (32.7%) of total NPP. 3) For the canopy NPP, the uncertainty was mainly from litterfall production. Measurement of diameter at breast height, temporal and spatial variation of growth and carbon concentration accounted for 5.9%, and 32.3%, 65.2% and 2.5% of the uncertainty of wood tissue NPP for one-year measurement, respectively. The relative uncertainty of shrub, herb, and fine root NPP were 25.0%, 12.7% and 52.3%, respectively. 4) Combined with the soil heterotrophic respiration (5.23 ± 0.20 t?hm^?2 a^?1) and coarse woody debris respiration (0.37 ± 0.21 t?hm^?2 a^?1), the NEP was estimated to be 1.94 ± 1.34 t?hm^?2 a^?1, overlapped with the interval of absolute value of NEE estimate (1.57 ± 0.47 t?hm^?2 a^?1). Conclusion: The 11-year mean NEE measured by the EC method is closed to the NEP measured by the inventory method in the typical temperate secondary forest at the Maoershan site. Careful system design and site-adapted data analysis of the EC method, measuring all components of NPP as completely as possible via appropriate approaches, and extending the period length of measurements, will help to improve the accuracy of carbon flux measurement in forest ecosystems. These findings improve the understanding of the CO₂ fluxes in typical temperate deciduous forests in Chin and the uncertainty of forest NPP and NEP at the local scale, and provide data and methodological support for accurate assessment of ecosystem carbon cycling.

Objective: The aim of this study was to investigate the carbon credits measurement method of mangrove protection carbon sink project activities in China, to promote measurable, reportable, and verifiable carbon credits of mangrove protection carbon sink projects into the carbon market for trading. Method: This paper proposed a carbon credits measurement method for mangrove conservation carbon sink projects that takes carbon benefits, biodiversity benefits, and community benefits into consideration. Futian Mangrove Reserve in Shenzhen was taken as an example, the PLUS model Markov chain method was used to determine the baseline scenario of the mangrove protection carbon sink project and the changes in carbon stocks and greenhouse gas emissions of each carbon pool. The default factor was used to calculate the carbon benefits of the mangrove conservation carbon sink project in the Futian Mangrove Reserve from 1988 to 2060 (the target year for achieving carbon neutrality in China). The biodiversity and community benefits of Futian Mangrove Reserve were evaluated using participatory village assessment, field visit and literature survey. Result: From 1988 to 2060, the carbon benefits of the mangrove protection carbon sink project in Futian Mangrove Reserve was 350 231.91 t, and the annual carbon benefits was 4 864.33 t?a^?1. According to the assessment results of biodiversity and community benefits, the mangrove conservation carbon sink project in Futian Mangrove Reserve was classified as a Class A project, and it was not necessary to adjust the carbon benefits. Therefore, the carbon credits of the mangrove protection carbon sink project in Futian Mangrove Reserve were the same as the carbon benefits. Conclusion: The carbon credits of Futian Mangrove Reserve effectively reflect the multiple benefits of conservation activities, that is, in addition to the ability of sequestration, emission reduction and sink increase, the project activities also synergistically respond to and solve other global problems. The development of carbon credits accounting methods for mangrove conservation activities is conducive to the effective allocation of resources through the carbon market mechanism, broadening financing channels for mangrove conservation activities, and further strengthening the protection of mangrove ecosystems.

Objective: It is important to study the resource changes, productivity and carbon sink capacity of Eucalyptus plantation forests in China during 1973—2018, with a view to revealing the soil fertility depletion of Eucalyptus plantation forests, objectively evaluating the contribution of Eucalyptus plantation forests to increasing timber supply and enhancing forest carbon sink capacity in China, and providing a scientific basis for formulating sustainable management policies. Method: In this study, we collected the sample plot data from 9 national forest inventories(NFIs) during 1973—2018, China forest-land database map in 2003 and 2016, as well as climate and elevation data, and analyzed the dynamic changes in the spatial distribution of Eucalyptus plantation forests and continuously tracked the changes of Eucalyptus in fixed sample plots, and quantitatively evaluated Eucalyptus in China based on the accumulation data of eucalyptus fixed sample plots for 5 periods of 25 years(from 1994 to 2018). The productivity, carbon accumulation capacity, and abandonment rate of Eucalyptus in China were quantitatively evaluated based on the accumulation of Eucalyptus in fixed sample plots for five periods of 25 years. Result: The results showed that regions with annual mean air temperature of 19-21 ℃, annual precipitation of 1 400-1 600 mm, and elevation of 0-300 m above sea level suit the growth of Eucalyptus plantations best. The average annual productivity of Eucalyptus trees nationwide generally ranges from 4.14 to 8.57 m³·hm^?2a^?1, which is higher in four provinces of Hainan, Guangdong, Guangxi, and Fujian, with 2-3-year-old Eucalyptus forests approaching 40 m³·hm^?2a^?1; according to the 9th inventory (2014—2018) data, the average annual carbon sequestration per hectare of Eucalyptus was 5.29 t·hm^?2a^?1, which was 2.95 and 2.18 times higher than that of fast-growing tree species, horsetail pine and fir plantations in the same region. Despite the low harvesting age of Eucalyptus and the fact that 46% of the harvesting volume is used for paper production, 54% of the harvesting volume is still in the form of panels for long-term carbon sequestration, and the carbon sink function is still strong. Eucalyptus is an important timber species, and while the area of Eucalyptus accounts for 6.85% of the country's plantation forest, the annual timber harvest accounts for more than 17.96% of the country's plantation forest harvest; among them, Guangdong and Guangxi account for 30.32% and 34.91% of their plantation forest area, while the harvest accounts for 66.29% and 49.97% respectively. However, Eucalyptus grow vigorously and consume large amounts of land power. The abandonment rate of the original Eucalyptus plantation area is about 25% or more every 5 years, and the cumulative abandonment rates at 10 and 20 years are close to 50% and 75%, respectively, with the risk of serious decline in land power and difficulty in reforestation after long-term continuous planting. Conclusion: Through measures such as controlling the continuous management cycle of Eucalyptus plantations, carrying out reasonable crop rotation and improving scientific management, the abandoned land can still be replanted. The area of Eucalyptus plantations replanted within 20 years accounts for less than 20% of their abandoned areas, and less than 30% within 50 years, indicating that there is still potential to increase the replanting rate. Therefore, sustainable management of Eucalyptus plantation forests in China should be strengthened to maintain soil fertility and make greater contributions to securing China's timber supply, protecting natural forest resources, enhancing forest carbon sequestration capacity and mitigating climate change.

Objective: In order to scientifically evaluate the results of desertification prevention and control in Egypt, in-depth study of the temporal and spatial characteristics of vegetation growth in Egypt in the past 20 years, and at the same time provide a scientific basis for the systematic evaluation of Egypt’s desertification prevention and control and sustainable development. Method: Based on MODIS-EVI data from 2001 to 2020, the harmonic analysis of time series is used to reconstruct the data, trend analysis, coefficient of variation and Hurst index were used for the analysis of temporal and spatial characteristics of vegetation growth in Egypt in the past 20 years and its future trends. Result: 1） The growth curve of vegetation in Egypt during the year is characterized by double peaks. In the past 20 years, vegetation growth in Egypt has tended to improve, with the average growth rate of EVI being 0.000 31?a^?1. 2） The areas with stable vegetation growth in Egypt accounted for 93.21% of the total area, mainly distributed in most areas of western, central, and southern Egypt; the areas with improved vegetation growth accounted for 4.79% of the total area, mainly distributed in the northwest coast of Egypt, east and west of the Nile Delta Department; the areas with decreasing vegetation growth accounted for 2.00% of the total area, mainly distributed in the central part of the Nile Delta. 3） The coefficient of variation of vegetation growth in Egypt has been relatively low in the past 20 years, while the fluctuations in vegetation growth in the Nile Delta and the Nile River coast areas are relatively obvious. 4） The reverse changes of future vegetation growth in Egypt are stronger than the changes in opposite direction. The area of vegetation improvement in the future will account for 3.74% of the total area, and the area of vegetation degraded in the future will account for 3.05% of the total area. Conclusion: In the past 20 years, Egypt has made remarkable achievements in the prevention and control of desertification. The growth of vegetation tends to improve in general, and it will show a certain degree of sustainability in the future.

Objective: To explore the effective network construction method of three-dimensional convolutional neural network (3D-CNN) in tree species classification supported by hyperspectral data. Method: Taking the southern Sierra Nevada, California, USA as the study area, the canopy height model (CHM) obtained from LiDAR data was divided into single trees and used as a supplement to establish samples. A 3D-CNN network structure with simpler structure, higher classification accuracy and no need to preprocess hyperspectral data was improved for forest species identification. Result: Compared with the conventional supervised classification methods(support vector machine, random forest), the traditional two-dimensional convolutional neural network model and the latest MSR 3D-CNN model, the overall classification accuracy of the 3D-CNN model proposed in this study is 99.79%, and the mean intersection over union(MIoU) is 99.53%. Compared with SVM and RF method, the overall classification accuracy is improved by about 5%, and the new 3D-CNN model has the characteristics of more accurate extraction of tree species' boundaries and less pepper and salt phenomenon; Compared with 2D-CNN, the overall classification accuracy is improved by about 10%, and MIoU is improved by about 7%; Compared with MSR 3D-CNN, the overall accuracy is not much different, but in the process of training and testing, this model takes much less time than MSR 3D-CNN model. Conclusion: The 3D-CNN model proposed in this study can efficiently process the original hyperspectral images, classify and map tree species, and add forest vertical structure information to make classification labels, which can obtain higher accurate classification results.

Objective: The optimal dehydration and low temperature storage conditions are still the difficulties in the research of recalcitrant seeds. In this study, the seed vigor under different dehydration methods and low temperature storage conditions was investigated, in order to provide theoretical basis and technical support for the collection and preservation of recalcitrant seeds in subtropical areas. Method: In this study, Castanopsis sclerophylla seeds were used as the experimental materials, and the germination ability of seeds before and after dehydration and cold storage was compared. The seeds were subjected to the different storage temperature (room temperature 20 ℃ and low temperature 4 ℃), and the treatment time (7, 14, 30, 60, 90 d), as well as different dehydration rate (fast and slow) and dehydration time (1, 2, 4, 8, 12, 24, 48, 96 h). The germination rate and germination index of the seeds under the interaction between low temperature and dehydration were analyze , to explore the effect of the interaction between dehydration methods and cold storage on seed germination. Result: 1) The results showed that low temperature storage, dehydration time and their interaction had significant effects on seed germination rate and germination index. 2) When stored at room temperature, the germination rate and germination index of seeds subjected to rapid dehydration were significantly increased compared with the non-dehydrated seeds. 3) Compared with unrefrigerated seeds, the cold storage treatment inhibited the germination of rapidly dehydrated seeds, but had no significant effect on the germination rate of undehydrated and slowly dehydrated seeds for 1-48 h, however the seeds almost lost vigor after slow dehydration for 96 h. The germination rate of unrefrigerated seeds was the highest (68.80%) after rapid dehydration, but it decreased significantly after refrigeration. The germination rate and germination index of seeds were significantly decreased after 30 days of cold storage. 4) Under the same cold storage (except for 30 d), the germination rate and germination index of seeds treated with short-term rapid dehydration were significantly higher or had no significant difference compared with those without dehydration, while the seeds vigor greatly reduced or lost when prolonged dehydration time. The germination rate and germination index of seeds with slow dehydration were generally significantly lower than those of undehydrated seeds. Conclusion: During storage at room temperature, rapid dehydration significantly promotes seed germination. There is an interaction between low temperature storage and dehydration treatment. Short-term rapid dehydration and cold storage treatment are conducive to the seed germination, while cold storage and slow dehydration treatment inhibit seed germination. C. sclerophylla seeds can be stored under both rapid dehydration at room temperature and short-term rapid dehydration at 4 ℃.

Objective: Hydraulic vulnerability segmentation is one of important drought resistance mechanisms of plants. The study on the differences of vulnerability segmentation among hybrid poplar individuals with different growth rates and the relationship between vulnerability segmentation and growth can not only provide experimental evidence for testing vulnerability segmentation hypothesis, but also provide theoretical basis and practical guidance for evaluating drought tolerance and growth strategy of the poplar under the background of frequent drought. Method: Three clones (K, Z, M) of 4-year-old offsprings of hybrid poplar [I-101 (Populus alba) × 84K (P. alba × P. glandulosa)] with different growth rates were selected as the research materials, and 3–6 plants were selected from each clone. Aboveground biomass (AGB) and the midday leaf water potential (Ψ_middy) were measured, and the vulnerability curves of roots, branches and leaves were constructed (P₅₀). The hydraulic safety margin (HSM) of leaves and branches were calculated, and the anatomical traits of xylem vessels were measured, including the vessel diameter (D_V), hydraulic weighted vessel diameter (D_H), vessel density (V_D), vessel lumen ratio (F_L) and (t/b)². Result: 1) The clone K had the highest AGB, followed by clone Z, and both of them were significantly higher than clone M. 2) The P₅₀ of branches of M was significantly lower than that of K and Z, while the P₅₀ of leaves and root segments had no significant difference among the three clones. Among different organs, the P₅₀ of branches was lower than that of leaves and roots. 3) In terms of vessel anatomical traits, the D_H, D_V and b of branches of M were significantly lower than those of K and Z, and the (t/b)² was significantly higher than that of K and Z. The D_V of leaves of M was similar to Z, but significantly lower than that of K. The V_D of root segment of M was significantly higher than that of K and Z, and other indexes showed no significant difference. Among different organs, theD_V gradually decreased along the hydraulic path from root to leaf, and the maximum mean diameter of vessels in the root segments was 5.12 times that of the leaves, while the V_D gradually increased from root to branch, and the V_D in the root segments was only 1/4 that of the branches. 4) Embolism vulnerability segmentation existed in all three clones, and the segmentation degree of M was the largest, slightly higher than K, and twice as high as Z. The HSM of leaves of clone Z was wider, while that of K and M was narrower or even negative. The HSM of branches of the three clones was similar. Conclusion: All the three clones with different growth rates exhibit vulnerability segmentation, and clone M with the slowest growth rate has the largest degree of segmentation. The difference in vulnerability of different organs can be reflected by D_V, (t/b)² and other vessel anatomical traits. The difference in hydraulic structure of xylem conduit of branches may be the main reason for the different degree of vulnerability segmentation of the three clones. Compared with K and Z, M with the slowest growth rate has the higher embolism resistance and the higher degree of vulnerability segmentation. The two phenomena may work together to protect stems from hydraulic failure, but this may be achieved at the expense of growth rates, suggesting that the increased vulnerability segmentation may be detrimental to plant growth.

Objective: This study aims to investigate the effect of different heat wave frequencies and contrasting water additions on the photosynthetic characteristics and growth ofSchima superba seedlings, so as to provide theoretical basis for revealing its adaptation mechanism to extreme high temperature events. Method: In this study, S. superba seedlings, a common broad-leaved tree species, were chosen as the experimental materials. An artificial heat wave simulation device was used to simulate the occurrence of natural heat waves. The seedlings were subjected to water control and replenishment treatments with different heat wave frequencies (no heat wave, single heat wave, two heat waves). The differences in the photosynthetic characteristics and growth rate of S. superba seedlings were analyzed for their resistance and resilience ability to different frequency of heat wave stress. Result: 1) With water addition, the single heat wave treatment had insignificant effects on the photosynthetic characteristics. S. superba was able to regulate leaf temperature by significantly increasing its transpiration rate (Tr), thus reducing water use efficiency (WUE) significantly, but there was no significant change in net photosynthetic rate (P_n). 2) Under controlled water supply condition, a single heat wave significantly decreased S. superba P_n by 49%, while there were no significant changes in Tr and WUE. However, the treatments significantly slowed down the recovery process of photosynthetic characteristics of S. superba. 3) Under the influence of two heat waves, regardless of water control and replenishment conditions, S. superba P_n significantly decreased (about 46% and 32%) during heat wave stage, respectively. Although it was able to still recover after the heat wave, the recovery process was hindered. The effects of multiple heat waves were additive, manifested as a weakening of the resistance and recovery ability of S. superba to heat waves. Conclusion: Our results indicate that the photosynthetic characteristics and growth rates of S. superba demonstrate divergent resistance and resilience to heat waves with the different water supply. The seedlings can maintain high temperature resistance through physiological regulation mechanism, but this mechanism would be disturbed when water supply is not adequate. Moreover, the interaction of high temperature and drought significantly affect the photosynthetic characteristics and growth rate of S. superba, and the effects of compound stress are stronger than single factor effects. These results suggest that the occurrence of combined seasonal high temperature and drought stress in subtropical regions, or the occurrence of high-frequency successive heat waves may significantly change the structure and function ofS. superba natural forests and plantations, as well as its stability and sustainability.

Objective: This study aims to solve the problems of easy confusion and difficult identification of chestnut varieties in production, through using the geometric morphometry（GMMs）to digitally analyze the leaf morphology of different chestnut varieties, so as to establish a method of leaf morphology identification of chestnut varieties. Method: The leaves of 80 varieties from different chestnut producing areas in China were used as materials, a total of 6 400 leaves were collected repeatedly in two years. Images were obtained by scanning, geometric morphometric method and Image J software was used to select 24 identification points combined with chestnut leaf characteristics, and the leaf morphology coordinate data were obtained in a consistent order. Morpho J software was used to classify leaf morphology data by production regions and varieties, and a generalized Procrustes analysis was performed to separate the leaf size and the morphology factor, and further form symmetric and asymmetric components. Principal component analysis and partial least squares allometric analysis were performed on the data, and the difference in leaf morphology among different varieties was visualized with grid change diagram. The 24 identification points were classified according to the discrimination contribution rate. The varieties were identified with canonical variables (CVs), discriminant analysis and significance test. Result: 1) The difference in leaf morphology of different varieties was mainly affected by the symmetric components, and the difference was not obvious in the asymmetric components. The cumulative contribution rate of the first two principal components (PCs) in the symmetric components reached 80.6%, which could be used as a CV for the difference analysis of chestnut varieties. The grid change diagram of the symmetric components showed that there were significant differences between varieties. 2) Principal component and allometric analysis showed that the top 14 identification marks with the highest contribution rate were the same, and could be used as the first-level identification marks. 3) The cumulative contribution rate of the first two CVs in the symmetric components reached 81.4%. The scatter plots showed that except for the similarity between 'Huaijiu' and 'Yanfeng', 'Yanshanhongli' and 'Yanchang', 'Yanlong' and 'Yanming', 'Liuyuebao' and 'Yelizang' higher, the other varieties could be accurately distinguished. 4) Discriminant analysis (DA) of chestnut production regions showed that, except Hubei and Anhui (97.5% vs. 96.9%), the correct discrimination rates of other regions reached 100.0%. The DA among varieties showed that 99.3% of the varieties had a discrimination rate of 100.0%, a few of varieties were lower discrimination rate but all above 95.0%, and the discrimination results were significantly different (P<0.05). 5) Cluster analysis reflected the similarity of leaf morphology among production regions and varieties, and the classification results were mostly consistent with the geographical distribution of provenance. Conclusion: The GMMs based on 24 identification marks can accurately identify different chestnut varieties. The screened 14 primary identification marks, 3 secondary identification marks, and 7 supplementary identification marks can accurately reflect the main differences in leaf morphology of chestnut varieties, and the correct discrimination rate reaches 95.3%~100.0%. The established chestnut variety leaf morphology identification database and the chestnut variety identification method based on the digital analysis of leaf morphology will provide technical support for the accurate identification of chestnut varieties.

Objective: This study aims to investigate the performance of plant growth traits of Populus deltoides clones under different photoperiod treatments, and screen the traits that can effectively evaluate photoperiod sensitivity of P. deltoides, so as to clarify the effect of photoperiods on physiological status of P. deltoides clones with different sensitivity. Method: In this study, 26 clones of P. deltoides were used as the research materials, and subjected to two photoperiod treatments (light 16 h/dark period 8 h, light 8 h/dark period 16 h) in artificial climate chambers. A total of 12 growth traits of P. deltoides were continuously observed at multiple time points under different photoperiod treatments, and the subordinate function method and principal component analysis were used to obtain the comprehensive evaluation index D value of photoperiod sensitivity of growth traits of P. deltoides. Regression analysis and path analysis were used to screen the direct effect indexes suitable for the evaluation of photoperiod sensitivity of P. deltoides, and the P. deltoides clones with different photoperiod sensitivity were selected for synchronously monitoring the growth and measuring the physiological indexes. Result: 1) The results of variance analysis showed that there were significant differences in 12 growth traits of P. deltoides under different photoperiod treatments (P<0.05). The leaf length, leaf width, leaf area and specific leaf area ofP. deltoides under short photoperiod were significantly greater than those under long photoperiod, while the net growth value of plant height, net ground diameter, dry weight of leaf, fresh weight of stem segment, fresh weight of root system, dry weight of stem segment, root dry weight and the observed values of node number were significantly lower than those under long photoperiod. 2) The analysis results of D value of comprehensive evaluation indexes for photoperiod sensitivity of P. deltoides showed that four indexes, including fresh weight of stem segment, number of nodes, net growth value of ground diameter and net growth value of plant height, had a greater direct effect on the comprehensive evaluation value of photoperiod sensitivity (0.113–0.338), which could be used as the character index for evaluating photoperiod sensitivity of P. deltoides. Among them, net growth value of plant height was more suitable for practical production. 3) The comprehensive comparison of photoperiod sensitivity of 12 characters showed that different clones in the same provenance had different photoperiod sensitivity. Among the 26 clones of P. deltoides, LS8, TN3 and WA1 had the highest photoperiod sensitivity, and QB7, LS5 and TN6 had the lowest photoperiod sensitivity. Three clones with high growth and high photoperiod sensitivity, LS9, LS4 and TN4, and three clones with low growth and low sensitivity, QB7, QB2 and QB4, were selected based on the growth performance of plants. 4) The Rubisco activity, triose phosphate isomerase activity and fructose-1,6-bisphosphate aldolase (FBA) activity of clones with high growth and high sensitivity under long photoperiod treatment increased with the increase of treatment time. The total chlorophyll content decreased first and then increased. The glutamine synthetase (GS) activity decreased gradually with the increase of treatment time. Under short photoperiod treatment, the Rubisco activity increased first and then decreased, and the total chlorophyll content decreased gradually. Rubisco activity and total chlorophyll content of clones with low growth and low sensitivity decreased gradually with the increase of treatment time. Under the treatment of short photoperiod, their FBA activity first decreased and then increased, and Rubisco activity generally decreased with the increase of treatment time. The changes of enzyme activities and total chlorophyll content of different P. deltoides clones were different under different photoperiod treatments. Conclusion: The growth characters of P. deltoides are significantly affected by photoperiod, among which the net growth value of plant height, net growth value of ground diameter, fresh weight of stem segments are more sensitive to photoperiod, which can be used as the character indicators for evaluating photoperiod sensitivity of P. deltoides. Combined with the net growth value of plant height, the clones can be divided into high growth sensitivity and low growth sensitivity types. The physiological responses of P. deltoides with different photoperiod sensitivities to photoperiod changes are significantly different. The FBA activity and GS activity of clones with high sensitivity are more sensitive to long photoperiod. The Rubisco activity of P. deltoides with different photoperiod sensitivities shows a reverse change trend under long photoperiod, which may lead to the growth differences of P. deltoides with different photoperiod sensitivities. The results can provide useful reference for the study of photoperiod response mechanism of poplar and forest trees, and the screened P. deltoides with different photoperiod sensitivity can provide germplasm for cultivating new poplar varieties with wide adaptability.

Objective: The species of Ericaceae are important flower resources. A stem sawfly pest feeding on twigs of Rhododendron fortuneiwas found in 2021 from Ningbo, China. This study aims to clarify its species and taxonomic status, and the explore the possible bearings on the diversification mechanism of stem sawflies. Method: The classical comparative morphology was used to clarify the species name and the systematic position of the pest. The whole genome was sequenced by the second generation sequencing technique. Mitogenome was assembled and the features were analyzed, genetic distances among the relatives were calculated, and the phylogenetic trees were inferred. Result: The new species of Cephidae, damagingR. Fortunei, has been identified: Janus dujuan Wei, sp. nov.. This new species is close to J. xanthus Naito & Smith, 1998 from eastern Tibet but differs from the latter by body color and structure. The length of the mitochondrial genome of the new species is 17 725 bp and contains 37 genes. Based on the data of mitochondrial genes, phylogenetic tree of five Janus species was reconstructed. The result showed that J. dujuan formed a sister group with a species of J. bimaculatus group, and there was a significant difference between J. dujuan and the other species of Janus with known mitochondrial genome data. The K2P distance of cox1 among J. dujuan and other Janus species was between 14.7% and 21.4%. We cautiously speculate that the diversification of Janus in Southern Asia is probably related to the diversification of Ericaceae in southern China. In the contrary, the diversification of Cephus in Mediterranean region is probably related to the diversification of the Poaceae, esp. the diversification of Triticum. Conclusion: The pest boring on stems of R. fortunei is a new species: Janus dujuan Wei, sp. nov.. It is similar to J. xanthus Naito & Smith, 1998 from Tibet but differs from the latter in body color and structure. The Janus showed a relatively large genetic distance for barcoding region within the genus, suggesting more taxonomic study on Janus is required. It is speculated that its diversification in Southern Asia is probably related to the diversification of Ericaceae in southern China.

The trees, as the skeleton of the terrestrial forest ecosystem, suffer from the stresses of forest pests for a long time, which endangers the normal growth of trees, even causes the death of trees, and poses a serious threat to the sustainable development of forestry. It is necessary to recognize and obtain the features of forest pests for realizing the rapid and accurate targets detection and monitoring of forest pests and pest damaged areas. This paper focuses on the analyses of the main features of direct targets of the biological stresses, such as plant diseases, plant insects, rats and rabbits, harmful plants etc. and indirect targets, and summarizes and reviews the research status of techniques and equipments for recognizing and identifying targets for forest pests control through different ways at home and abroad. It is recommended to establish interdisciplinary forces to constantly explore and study the target recognition technology and equipment for forest pest control and integrated control intelligent systems based on the early warning with the target recognition of the plant stresses and the cooperative defense control with the sensor network. This paper looks forward to the future development of passive/active sensing technologies focusing on target identification of forest pests control, and proposes to conduct research on the passive sensing technologies of control targets, including the machine vision, the odor-sensitive, the force-sensitive, the thermal-sensitive and the acoustic-sensitive according to the physical and chemical characteristics of forest plants under biological stresses. The active sensing technologies, such as LiDAR scanning, the photoacoustic effect active attraction and the electronic insects and odoriferous active attraction, would be applied to sense some specific pest targets which the passive sensing technologies are difficult to sense. It is also proposed that the design and development of new sensors such as the biology, the magnetic-sensitive, the humidity-sensitive and the thermal-sensitive sensors, and the multi-sensor fusion technologies for ultrasound, LiDAR, radiation and satellite images, so as to improve the accuracy of forest pest targets recognition. Finally, the paper proposes corresponding research recommendations for target perception and recognition technology around specific targets such as plant roots, wild mammals, terrestrial termites, and harmful plants.