Objective: This work aims to explore the relationship between the geographical distribution of Picea koraiensis and climate change and to simulate potential suitable distribution areas of P. koraiensis under climate change during different periods, so as to provide a scientific basis for resource management and the protection of P. koraiensis. Method: Based on data from 59 existing distribution sites of P. koraiensis and 19 climate variables obtained from the WorldClim website, the maximum entropy model (MaxEnt) was used to simulate the suitable distribution areas of P. koraiensis during different time periods: the present, last interglacial (LIG), last glacial maximum (LGM), mid-holocene (MH), and two future climate scenarios (RCP4.5 and RCP8.5) that would cover periods (2050s and 2070s). This paper discussed the main environmental factors that could limit the geographical distribution of P. koraiensis, identified potential biological sanctuaries, and predicted how the distribution of P. koraiensis might change under future climate change scenarios. Result: The prediction result from the MaxEnt model was reliable, and the average AUC values of the training dataset and test dataset were both greater than 0.99, indicating high reliability. Precipitation of warmest quarter (Bio18), temperature seasonality (Bio4) and precipitation seasonality (Bio15) were the main variables that limited the distribution of P. koraiensis, with contribution rates of 40.6%, 28.9% and 24.6%, respectively. The current suitable distribution areas of P. koraiensis included the Great Khingan Mountains, Lesser Khingan Mountains and Changbai Mountains in China. The suitable areas of P. koraiensis during the LIG, LGM and MH periods expanded by 107.78%, 110.28% and 105.25%, respectively. From the LIG to the present, its distribution centre followed a migratory trend toward the southeast, then to the northeast, and then to the southwest. The suitable distribution area of P. koraiensis under the future climate scenario shows a decreasing trend. The suitable area under the RCP4.5-2050s, RCP4.5-2070s, RCP8.5-2050s and RCP8.5-2070s scenarios would decrease to 99.06%, 96.88%, 98.05% and 95.08% compared to the current period, respectively. The highly suitable area shows a fragmented distribution. The population distributed in the hinterland of Changbai Mountains and Lesser Khingan Mountains would be relatively stable. Conclusion: Precipitation has a greater influence on the distribution range of P. koraiensis than temperature. P. koraiensis population has expanded during the LIG and shrunken continuously from the MH into the modern era. Based on population genetic diversity, the prediction of suitable areas and sporopollen fossils, it is speculated that the hinterlands of Changbai Mountains and the Lesser Khingan Mountains are the interglacial refuges for P. koraiensis. During future climate scenarios, the suitable distribution area of P. koraiensis will be reduced, and the distribution centre will migrate to high altitudes and high latitudes. The priority should be given to protecting the marginal populations in the northern to central Great Khingan Mountains, the western part of Changbai Mountains and the northern part of Zhangguangcai Mountains.

Objective: This paper probes into the suitable area zoning and ecological threshold of natural Acer truncatum, and analyzes the rationality of the zoning results through field investigation of the sample points, providing theoretical basis for the reasonable location of artificial cultivation of natural Acer truncatum, the investigation and protection of natural germplasm resources, and the selection and breeding of excellent varieties. Method: Based on 138 selected representative sample points, combined with 15 ecological factors, the MaxEnt model was applied to analyze the main ecological factors and threshold range affecting the distribution of natural Acer truncatum by knife cutting method. Then, the model results were evaluated by using the GIS simulation of the suitable area division in China and the subject work characteristic curve. After the evaluation, the sample points were investigated on the spot, and the rationality analysis was carried out on the zoning results. Result: 1) The ROC curve training set and test set AUC values of the regionalization results of the suitable areas of natural Acer truncatum were 0.968 and 0.947. 2) The main ecological factors affecting the range of suitable areas of the natural Acer truncatum were average temperature in the driest season, precipitation in the wettest season, altitude, precipitation in the driest season and average annual temperature, with a cumulative contribution rate of 82.80%, and soil factors had little effect on the distribution of the natural Acer truncatum. It is suitable to grow in areas with average temperature of ?12.50–3.82 ℃ in the driest season, precipitation of 230–547 mm in the wettest season, altitude of 0–1 465 m, precipitation of 5–53 mm in the driest season and average annual temperature of 4.04–15.41 ℃. 3) The main habitat area of the natural Acer truncatum spans 34°—46°N, 108°—126°E, and concentrated in Inner Mongolia, Shaanxi, Hebei, Jilin, Shanxi, Liaoning, Shandong, Henan, Gansu and other provinces（autonomous regionsand municipalities）, with an area of about 1 642 247 km², accounting for 17.11% of the total land area of China. Among them, the high suitability areas are mainly located in Hebei, Liaoning and Shandong, with an area of 277 792 km², accounting for 16.92% of the total suitability areas in China. 4) The rationality of regionalization of suitable area was analyzed through field investigation of sample points. The overall regionalization accuracy of natural Acer truncatum was 0.82, and the Kappa coefficient was 0.61. Conclusion: The suitable areas of the natural Acer truncatum are widely distributed in north China and parts of northeast and northwest China. Bioclimatic factors and altitude factors are the main limiting ecological factors for the growth of the natural Acer truncatum in China. In this study, the simulated zoning results of the suitable area of the natural Acer truncatum can reflect the spatial distribution characteristics of the natural Acer truncatum, and provide a theoretical basis for making full use of the natural resources and maximizing the economic value of the natural Acer truncatum.

Objective: Amygdalus pedunculata is one of the important oil tree species in China, with extremely high economic value and ecological benefits. This study aims to predict the suitable areas of A. pedunculata in China and its response to climate change, which would provide scientific basis for the protection and artificial planting of A. pedunculata resources. Method: A total of 148 A. pedunculata distribution data and 34 environmental factors were filtered out by R language and ArcGis. The ENMeval software package was used to optimize the maximum entropy niche model (MaxEnt) parameters, and complete the filtering of environmental factors required for modeling which was based on Pearson correlation analysis and VIF variance expansion factor analysis. Jackknife was used to evaluate the dominant environmental factors in the suitable area of A. pedunculata. The optimized model was used to analyze the geographical distribution of the currently suitable distribution areas of A. pedunculata, to speculate the potential distribution in the Last Inter Glacial, the Last Glacial Maximum and the Mid Holocene, and analyze their potential distribution. According to the sixth climate model of IPCC, the changing trend of A. pedunculata in the future distribution area under different climatic scenarios could be predicted. Result: The results of model optimization showed that when the model feature combinations were linear, quadratic, fragmented, product and threshold features, and the regulation radio was 1.5, the training omission rate and low complexity of MaxEnt model were low, and the fitting was the best. The AUC value of the receiver-operating characteristic curve was 0.967, showing that the model prediction results were accurate and high reliability. According to the results of the Jackknife, the precipitation of the warmest season, the precipitation seasonality, the temperature seasonality, the annual mean temperature, and the topsoil base saturation were the dominant environmental factors affecting the distribution of A. pedunculata. The prediction results of the model showed that at present suitable areas of A. pedunculata in China were mainly distributed in the Inner Mongolia Plateau and Loess Plateau. The analysis of historical, current and future adaptation areas showed that A. pedunculata was sensitive to climate change. Under different climate change scenarios in the future, the suitable area of A. pedunculata would shrink and tend to migrate to middle and high latitude, and high altitude areas, especially under high greenhouse gas emission concentration, the migration distance would be longer. Conclusion: The optimized model can accurately predict the potential geographical distribution area of A. pedunculata. Temperature and precipitation are the most likely environmental factors causing the migration of A. pedunculata distribution areas. In the future, climate warming will cause the migration of the distribution area of A. pedunculata. Under the background of future climate warming, suitable areas of A. pedunculata tend to decrease. The reduction areas are mainly in low latitudes and low altitudes, while newly suitable areas appear in medium and high latitudes, and high altitudes (Hohhot, Ordos, Xilingol, Yan'an).

Objective: The aim of this study is to develop stand-level biomass and carbon stock models for major forest types in Guangdong Province, so as to facilitate the estimation of the biomass and carbon stock in the province, and realize the effective connection of the provincial with municipal- and county-level data. In addition, this study also analyzes the impact of tree species structure and climate on models and its impact mechanism, providing theoretical guidance for more detailed carbon sink monitoring and forest quality improvement. Method: Taking 12 major forest types in Guangdong Province as research object, and using the national forest inventory in 2007, 2012 and 2017 in Guangdong Province, the models of above-ground biomass, below-ground biomass, above-ground carbon stock and below-ground carbon stock compatible with the volume for each forest type were established by using the nonlinear error-in-variable simultaneous equation approach. The influence of tree species structure was introduced into each model in the form of dummy variables, and the climate-sensitive stand biomass and carbon stock models were established by the method of reparameterization. Finally, the model fitting results were evaluated, and the impact of climate variables on stand biomass and carbon stock was also analyzed. Result: The models of volume, above- and below-ground biomass, and the mean carbon content coefficient of above- and below-ground biomass were obtained. 1) The adjusted coefficients of determination ($ R_{\mathrm{a}}^2 $) of basic models based on basal area and mean height were between 0.947?0.997. The total relative errors (TRE) and the mean systematic errors (MSE) were within ±1.54% and ±2.48%, respectively, which were not more than ±3%. The mean prediction errors (MPE) were between 0.30%?3.61%, and only some of models of Quercus spp. forest and Acacia spp. forest were slightly more than 3%. The mean percent standard errors (MPSE) were between 3.30%?13.39%, which were not more than 15%. 2) The $ R_{\mathrm{a}}^2 $ of simplified models based on basal area were between 0.876?0.996. Except for the poor fitting effect of below-ground biomass model of Acacia spp. forest, the TRE and MSE of other models were within ±3.19% and ±2.74%, respectively, with MPE of 0.36%?4.70% and MPSE of 4.18%?15.61%. The $ R_{\mathrm{a}}^2 $ of supplementary models based on mean DBH and stand density were between 0.775?0.977, most of which were above 0.9. Except for the poor fitting effect of some models of Acacia spp. forest, the TRE and MSE of other models were within ±2.28% and ±1.83% respectively, with MPE of 1.12%?6.24% and MPSE of 5.91%?17.44%. 3) The $ R_{\mathrm{a}}^2 $ of stand-level models for distinguishing tree species structure were between 0.960?0.997. TRE and MSE were within ±1.61% and ±2.33% respectively, MPE were between 0.30%?3.41%, and MPSE were between 2.67%?12.92%. In addition, most models were significantly better than the basic models. 4) The climate-sensitive stand-level biomass and carbon stock models for 8 forest types were constructed, which $ R\mathrm{_a^2} $ were between 0.947?0.998. TRE and MSE were within ±1.86% and ±1.96% respectively, MPE were between 0.29%?2.65%, and MPSE were between 3.18%?13.29%. Most models were significantly improved compared with the basic models. In most cases, biomass is negatively correlated with temperature index, and negatively correlated with evapotranspiration or positively correlated with precipitation. Conclusion: The models constructed in this study have good fitting effect and high prediction accuracy. In practical application, appropriate models can be selected according to the availability of data and the estimation range. High temperature, excessive evapotranspiration, or insufficient precipitation are the main factors limiting the growth of forest biomass and carbon stock in Guangdong.

Objective: To investigate the carbon sequestration by forest vegetation and its offsetting effect in Beijing, and to predict the carbon offsetting potential in the future up to the carbon neutral year, with a view to providing a scientific basis for carbon sequestration by forest vegetation, energy saving and emission reduction, and carbon neutralization pathway in Beijing. Method: Forest inventory data, photosynthetic rate method and IPCC inventory guidelines were used to study the spatial and temporal dynamics of vegetation carbon fixation, energy CO₂ emissions and intensity from 2000 to 2020, to evaluate the offsetting effect of carbon sequestration by forest vegetation on CO₂ emissions, and to predict the carbon offsetting potential in the future up to the year of carbon neutrality by using the GM(1,1) gray prediction model. The potential of carbon offsetting was predicted by using the gray prediction model of GM(1, 1). The average carbon sequestration capacity of shrubs, deciduous broadleaf forests, evergreen coniferous forests and deciduous coniferous forests in the past 20 years was 4.24, 4.60, 1.68 and 1.95 t·hm^?2a^?1, respectively. Miyun District had the highest growth in vegetation carbon fixation and Xicheng District had the lowest, with cumulative increases of 2.27×10⁵ and 7.86×10² t·a^?1, respectively, from 2000 to 2020.The city’s total energy carbon emissions from 2000 to 2020 showed a trend of first increasing and then decreasing, with a cumulative increase of 1.98×10⁷ t·a^?1 increased by 21.64%; Chaoyang District has the highest CO₂ emissions, and Yanqing District has the lowest, respectively, 1.54×10⁷-2.46×10⁷ and 1.78×10⁶-2.20×10⁶ t·a^?1. Xicheng District has the most significant energy emission reduction, and Changping District has the fastest growth in energy CO₂, emissions; the intensity of Beijing’s carbon emissions per unit of GDP has increased from 2.79 t per ten thousand yuan in 2000 to 0.32 t per ten thousand yuan in 2020, with a clear downward trend; Miyun District has the highest CO₂, emission intensity, and Xicheng District has the lowest, at 0.79-9.76 t per ten thousand yuan and 0.11-2.08 t per ten thousand yuan, respectively.The carbon offsetting effect of Beijing’s forest vegetation from 2000 to 2020 ranges from 1.56% to 2.50%, with shrubs being the highest and deciduous coniferous forests being the lowest. The average value of the offsetting effect of carbon sequestration by Beijing’s forest vegetation on CO₂ energy emissions in different periods of time is 4.3% in each district, and it is the highest in Yanqing District and the lowest in Xicheng District, with 15.91% and 0.02%, respectively. By 2060, the carbon sequestration and carbon offsetting effect of forest vegetation in Beijing will increase to 8.01×10⁶ t·a^?1 and 15.44%, respectively, with an average annual increase of 13.29% and 1.30%, and the CO₂ energy emission will decrease to 4.99×10⁷ t·a^?1 with an average annual decrease of 2.76%. Conclusion: The carbon fixation of forest vegetation in Beijing increases rapidly from 2000 to 2020, and the carbon fixation of different vegetation types is highest for shrubs, followed by deciduous broad-leaved forests, evergreen coniferous forests, and lowest for deciduous coniferous forests; CO₂ energy emissions increase first and then decrease, and the carbon offsetting effect of forest vegetation is on an overall rising trend; in order to enhance the contribution of carbon neutrality of forest vegetation in Beijing. In order to increase the carbon neutral contribution of Beijing’s forest vegetation, it is necessary to optimize the composition of forest species, increase the proportion of broadleaf forests, and improve the quality of forests in the future.

Objective: To clarify the soil preferential flow characteristics in typical forests of pure forest and mixed forest in this special habitat in southwest karst area, so as to provide a theoretical basis for local forest vegetation restoration. Method: Two typical stand types (pure Platycladus orientalis forest and mixed Platycladus orientalis, Pinus massoniana, and Eucalyptus maideni forest) were selected and two simulated rainfall amounts were set. Through field staining tracing experiments, the soil was stained with bright blue dye solution to excavate the stained vertical and horizontal profiles of the soil. With the help of image processing technology, five characteristic parameters of preferential flow, such as dyeing area ratio, maximum infiltration depth, matrix flow depth, preferential flow ratio and length index, were extracted, and the distribution, quantity, and proportion of preferential path of the soil at different depths were also obtained. Result: Under the same simulated rainfall, the ratio of soil staining area and maximum infiltration depth of mixed forest were higher than that of pure forest. When the simulated rainfall increased from 25 mm to 60 mm, the ratio of dyed area of mixed forest changed from 12.36% to 16.44%, and the average maximum infiltration depth changed from 22.21 cm to 30.64 cm. The increase of dyeing area ratio and average maximum infiltration depth was similar. The dyeing area ratio of pure forest changed from 7.42% to 15.89%, and the average maximum infiltration depth changed from 12.50 cm to 17.59 cm. The increase of dyeing area ratio was significantly higher than the average maximum infiltration.The soil under the mixed forest is finger-shaped or branched with independent patches, while the pure forest is funnel-shaped, without independent patches.When the simulated rainfall was 25 mm, the matrix flow depth, preferential flow ratio and length index under the mixed forest were 1.65 cm, 76.70%, and 352.61% respectively, which were higher than those of pure P. orientalis forest by 1.31 cm, 74.33%, and 184.20%. When the simulated rainfall increased to 60 mm, the matrix flow depth, preferential flow ratio and length index under the mixed forest were 2.21 cm, 77.18%, and 497.02%, while those of the pure Platycladus orientalis forest were 4.29 cm, 53.83%, and 331.27%. The preferential paths of mixed forest and pure forest in karst area were mainly distributed above 15 cm soil layer, and most of them were less than 5 mm in radius. The preferential paths under mixed forest changed more with the depth of soil layer, and the proportion of priority paths with large impact radius (> 5 mm) (19.0%) was higher than that of pure forest (9.0%). Conclusion: There are certain preferential flows under pure Platycladus orientalis forest and mixed Platycladus orientalis, Pinus massoniana, and Eucalyptus maideni forest in karst area. Due to the influence of its special earth-rock structure, there are more preferential paths in forest soil. The development degree and spatial variability of preferential flow under mixed forest is higher than that of pure forest, which is directly related to the high proportion of preferential paths with large influence radius and strong variability of preferential paths.

Objective: Taking the fixed sample plot of Jiaohe mixed coniferous and broad-leaved forest in Jilin as the object, this study explores the impact and maintenance role of biological and abiotic factors on forest productivity, providing scientific basis and theoretical guidance for the sustainable management of the mixed coniferous and broad-leaved forest in Northeast China. Method: Multiple regression analysis was used to quantify the impact of explanatory variables (biological factors including unit area basal area, forest differentiation degree, biodiversity, and abiotic factor, namely topographical factor) on the response variable(biomass increment of survivors, biomass increment of recruits, biomass mortality). Determine the relative importance of the above three biomass changes on the net biomass change through variance decomposition. Result: For biomass increment of survivors, all explanatory variables together explained 12.07% of its total variance, with a significant positive effect of basal area per unit stand area and a significant negative effect of slope. For biomass increment of recruits, all explanatory variables together explained 22.62% of its total variance. The coefficient of DBH variation and phylogenetic diversity had significant positive effects on the biomass increment of recruits. Basal area per unit stand area, elevation, and slope showed significant negative relationships with the biomass increment of recruits. For biomass mortality, all explanatory variables together explained 3.51% of its total variance, with a significant positive effect of basal area per unit stand area. The fraction of the total variance of net change in biomass that could be explained by biomass increment of recruits, biomass increment of survivors and biomass mortality was 0.01%, 20.87% and 74.54%, respectively. The relative contribution of biomass mortality to the net biomass change was the largest, but its predictability was low. Conclusion: Basal area per unit stand area had different effects on different processes of biomass dynamics . Basal area per unit stand area promoted biomass mortality as well as the growth of survivors but suppressed the growth of recruits. The tree differentiation degree and phylogenetic diversity enhanced the growth of recruits. Among the topographic factors, the growth of survivors was negatively related with the slope, the growth of recruits was negatively related with the elevation and the slope .The net biomass change was mainly influenced by biomass mortality and biomass increment of survivors.

Objective: This study analyzed the effects of bamboo chicken farming (BCF) on the active organic carbon and carbon pool management index of the topsoil of Phyllostachys praecox forest under different densities. We hope that this study will clarify the extent of disturbance to soil quality and carbon stability of bamboo forest ecosystems by BCF under different densities, and provide a scientific basis for the development of sustainable and eco-friendly under-forest farming strategies. Method: We characterized the different farming densities by the different distances from the chicken house. And we investigated the differences in the distribution of soil active organic carbon pools and the carbon pool management index under the conditions of 5 m (2.25–2.70 chickens·m^?2), 15 m (1.05–1.26 chickens·m^?2), 25 m (0.60–0.72 chickens·m^?2), 35 m (0.34–0.41 chickens·m^?2), and >60 m (CK, pure forest, 0 chickens·m^?2) from the chicken house. Result: We found that BCF could effectively promote the accumulation of soil organic carbon (SOC) compared with pure forest, but there was no significant difference in SOC at different farming densities And the active organic carbon fractions such as easily oxidizable organic carbon (EOC), light fraction organic carbon (LFOC), and particulate organic carbon (POC) were found to increase by 43.72%–76.95%, 5.55%–47.85%, and 19.59%–43.54%, respectively, in the bamboo forest chicken rearing system. But dissolved organic carbon (DOC) decreased significantly by 6.35% to 19.09% in BCF compared to pure forest. We also found that EOC, LFOC, and POC were significantly and positively correlated with SOC, but DOC was not significantly correlated with SOC in the BCF system. Compared with pure forest, carbon pool activity, activity index, carbon pool index, and carbon pool management index were found to be significantly increased in the BCF system, while the oxidative stability coefficient was significantly decreased. Conclusion: BCF improved soil carbon pool management indices and soil quality, and significantly altered the distribution of active organic carbon pools in surface soil. And higher farming density may influence litter input and disrupt surface soil structure through frequent disturbances, reducing soil water stability and affecting soil organic carbon accumulation. Moderate resting or rotation at higher farming densities may be the only way to balance the economic and environmental benefits of the current process of farming chickens in bamboo forests.

Objective: Larch is the main tree species for afforestation in northeast and north China. Growth and yield tables of larch plantations were compiled to provide the basis for scientific management. Method: Based on the data of 552 permanent sample plots of larch plantations from the fifth to the eighth national forest inventory and meteorological data in 7 provinces of northeast and north China (Beijing, Hebei, Shanxi, Liaoning, Jilin, Heilongjiang and Inner Mongolia), growth and yield tables were produced for larch plantations with different site levels using 3-PG_mix model. Result: The model parameters of larch plantations were obtained by calibration and validation. The simulated and measured values of stand variables were consistent with each other (R² was between 0.71 and 0.96). The mean relative errors in terms of stand volume were 5.70%, 0.95%, 4.70%, and ?4.56% for Larix gmelinii, Larix olgensis, Larix principis-rupprechtii and Larix kaempferi, respectively. The RMSE (root mean square error) values were 14.88, 12.00, 16.74 and 13.11 m³·hm^?2, respectively. The growth and yield tables could describe the change of stand variables with age, including stand average DBH, average height, stem density, stock volume, stand biomass, periodical and mean annual increment etc. Results showed the differences in the growth of the four larch species, owing to the difference in suitable conditions, phenological period, growth period and other biological characteristics. The model results are statistically reliable and biologically rational. Conclusion: The simulation results of the 3-PG_mix process-based growth model can be used to produce the growth and yield table of larch plantations, and the study provided a novel way for forest growth and yield table.

Objective: In this paper, the physiological characteristics of latex flow in young rubber trees of different varieties under the various tapping systems were studied, in order to lay the theoretical foundation for elaborating the mechanism of latex flow and provide a guidance for planning rational tapping system to different varieties in natural rubber production. Method: The 6-year-old healthy virgin rubber trees of 4 varieties, PR107, RY8-79, Tjir1 and RY7-33-97, were selected, and the intensive tapping with S/2 d/2 (tapping line length of ? stem circumference and one tapping every two days) and subsequent stimulation with 1% ethrel were applied. The rubber particle size, and conventional physiological parameters of latex flow, such as the dry rubber content (DRC), latex volume, duration of latex flow, initial velocity and plugging index, were investigated, and further the effects of different tapping times were compared. Result: 1) The rubber particle size of different varieties was different obviously. In the virgin tree, the order of rubber particle size was RY8-79 >PR107 > RY7-33-97 > Tjir1. During the intensive tapping, the rubber particle size of different varieties increased firstly then decreased with the increase in tapping times, and the rubber particle size of RY8-79 and Tjir1 changed faster than that of PR107 and RY7-33-97. After the eighth intensive tapping, the rubber particle size decreased to below 0.80 μm usually, which was significantly lower than the largest size (P<0.05). During the ethrel stimulation, rubber particle size generally showed a downward trend and remained at a low level. 2) In the virgin tree, the order of DRC was RY7-33-97>RY8-79 >PR107 >Tjir1. Under the intensive tapping, DRC of RY8-79 and Ry7-33-97 dropped faster than that of PR107 and Tjir1. During the ethrel treatment, DRC of PR107 showed a slight downward trend, but that of RY8-79, Ry7-33-97 and Tjir1 dropped obviously, especially for RY7-33-97. 3) Under the intensive tapping condition, the change rule of duration of latex flow was highly consistent with latex volume, and for these two parameters, RY8-79 was obviously higher than that of PR107, RY7-33-97 and Tjir1. After the ethrel treatment, the duration of latex flow and latex volume of all varieties were significantly increased (P<0.05), especially for PR107 and Tjir1. 4) The initial velocity of latex flow of RY8-79 and RY7-33-97 was obviously higher than that of PR107 and Tjir1 under intensive tapping condition, and etherl significantly reduced the initial velocity of all varieties. 5) The plugging index of RY8-79 was the lowest, while that of RY7-33-97 was the highest amongst the four varieties. Ethrel stimulation obviously reduced the plugging index. 6) Under the intensive tapping condition, the thiol content of RY8-79 was the highest, followed by PR107 and RY7-33-97, Tjir1 was the lowest. In about 48 h after ethrel stimulation, the thiols content of the four varieties generally decreased. Conclusion: The effects of latex flow induced by intensive tapping and ethrel stimulation are different among various varieties. The parameters of rubber particle size and DRC related with yield usually are difficult to recover to the healthy level under intensive tapping and ethrel overstimulation. Compared with other parameters, rubber particle size and DRC are less affected by the surrounding environment and can be used as references to evaluate the overflow. When the rubber particle size drops below 0.80 μm, it always indicates that the tapping intensity should be reduced. The varieties with fluent latex flow and high yield under natural conditions are usually intolerable to the intensive tapping and ethrel overstimulation, thus the varieties of RY8-79 and RY7-33-97 as main cultivars should avoid the application of ethrel while PR107 is fit to stimulate. Using young rubber tree as materials, combined with intensive tapping and ethrel stimulation, can be used as one of the methods for quickly screening the resistance of different varieties to tapping and ethrel stimulation in early breeding, and also provide a basis for the formulation of different variety tapping systems for rubber production.

Objective: Walnut is a high-quality economic forest tree. Arbuscular mycorrhizal (AM) fungi can promote plant growth and phosphorus (P) uptake, however, the mechanisms by which AM fungi enhance nutrient utilization and plant growth in walnuts are not clear. This study aims to explore the effect of AM fungi on P uptake of walnuts under low P conditions and the associated mechanisms. Method: In this study, an effective AM fungal strain, Diversispora spurca, screened earlier, was used to inoculate Juglans regia cv. Liaohe 1 seedlings, and the effects of D. spurca on plant growth, root system architecture, root P, root and soil phosphatase activities, and the relative expression of root acid phosphatase secretion genes (JrPAP10 and JrPAP12) and phosphate transporter protein genes (JrPT3;1 and JrPT3;2) of J. regia cv. Liaohe 1 seedlings under appropriate P (100 μmol·L^?1) and low P (1 μmol·L^?1) level conditions were studied. Result: After three months of inoculation with D. spurca, the mycorrhizal colonization of walnut root system reached 45.6%–53.2%, and low P treatment significantly increased root mycorrhizal colonization, compared with appropriate P treatment. Inoculation of D. spurca significantly increased plant biomass and soil acid, neutral, and alkaline phosphatase activities under both low and appropriate P levels conditions. D. spurca also significantly improved root morphology as well as increased root P content and root acid phosphatase activity under low P condition. Root JrPAP10 expression was up-regulated by D. spurca under both low and appropriate P levels conditions, while JrPAP12 expression was induced by D. spurca only under low P level condition. In addition, D. spurca up-regulated the relative expression of JrPT3;1 in roots under both low P and appropriate P level conditions, while the expression of JrPT3;2 was inhibited by D. spurca. Conclusion: The AM fungus, D. spurca, can induce up-regulated expressions of JrPAP10, JrPAP12, and JrPT3;1 in roots of walnut seedlings under low P levels conditions, increase soil phosphatase, root acid phosphatase, and improve root morphology, and thereby enhancing P uptake and biomass accumulation of walnut seedlings.

Objective: In this study, plant growth-promoting microorganisms (PGPM) were used to inoculate into the rhizosphere of Liquidambar formosana to investigate effects of PGPM on soil physicochemical properties and the leaf color of L. formosana, as well as changes in the composition and diversity characteristics of the rhizosphere microbial community, in order to study the effect of PGPM on plants and soil microorganisms. Method: A field inoculation experiment was conducted on 7-year-old L. formosana seedlings with consistent growth in Jurong Forest Farm of Jurong City with phosphate solubilizing bacteria Serratia marcescens subsp. marcescens (NJ2D) and Funneliformis mosseae (BJ04), and the effects on soil physical and chemical properties, leaf color parameters in autumn and soil microbial community were analyzed. Result: 1) The total nitrogen, total phosphorus, soil organic matter, available phosphorus content, soil moisture content (%), and soil pH of the rhizosphere soil of L. formosana in the treatment group were significantly increased compared to the control group (P<0.05). 2) The content of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids in leaves of L. formosana inoculated once with BJ04 significantly increased (P<0.05), while NJ2D+BJ04 inoculation significantly increased the anthocyanin level in the leaves (P<0.05). 3) There were significant differences in the rhizosphere soil microbial community diversity between control group (CK), NJ2D, BJ04 and NJ2D+BJ04 treatments (P<0.05). The number of OTUs (operating taxonomic units) of rhizosphere bacteria in L. formosana trees inoculated with NJ2D, BJ04, and NJ2D+BJ04 was significantly increased compared to the control group (P<0.05), while the number of OTUs of arbuscular mycorrhizal fungi (AMF) was significantly reduced compared to the control group (P<0.05). 4) The high-throughput sequencing results of rhizosphere microorganisms showed that Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria and Gemmatimonadetes dominated the bacterial communities on the rhizosphere of L. formosana. Within the AMF community, Glomus, Rhizophagous and Dominika were dominant genera. However, after inoculation, the species abundances of Acidobacteria, Chloroflexi and Planctomycetes were significantly reduced within the rhizosphere of L. formosana (P<0.05), whereas Proteobacteria and Actinobacteria were significantly increased (P<0.05). Conclusion: Inoculation with phosphorus solubilizing bacteria, arbuscular mycorrhizal fungi, and composite microbial agents NJ2D+BJ04 can all influence the soil microenvironment and have an impact on the autumn colour of L. formosana leaves.

Objective: To clarify the mechanism of industrial agglomeration on enterprises’ GVC (global value chain) position and provide policy implications for wood enterprises to enhance their GVC position through industrial agglomeration. Method: Taking the export domestic value added rate (DVAR) as an index of the enterprises’ GVC position, a theoretical framework of the role of industrial agglomeration on DVAR was constructed. Based on the sample of 15 406 Chinese wood enterprises and customs trade data, the mediating effect model was applied to study the impact of industrial agglomeration on DVAR through the two paths of enterprise cost plus rate and the relative price of domestic intermediate goods. Result: 1) Overall, the clustering of the wood industry has significantly increased DVAR, with increase in clustering level of 1 unit resulting in an increase of 0.002 3 units in DVAR. 2) Specifically, for all sub-industries in the wood industry, the impact of industrial agglomeration on DVAR shows heterogeneity: increases in each unit of industrial agglomeration level has significantly increased the DVAR of wood-based panel industry by 0.014 1 units; the impact on the DVAR of wood processing industry and wood products industry is not significant; agglomeration reduces the DVAR of the wooden furniture industry by 0.006 8 units. 3) From the perspective of enterprise heterogeneity, compared with processing trade enterprises and foreign investment enterprises, industrial agglomeration significantly promotes the improvement of DVAR of general trade enterprises and local enterprises. There is no “inverted U” and “N” nonlinear relationship, that is, the production of enterprises is still in the range of increasing returns to scale, and further agglomeration of wood industry can still improve DVAR. 4) The results of the mediating effect model show that: the estimated coefficient of the cost plus rate and the relative price of domestic intermediate goods on DVAR is significantly positive, and for every 1 unit increase in the cost plus rate, DVAR is significantly increased by 0.066 0 units; For every 1 unit decrease in the relative price of domestic intermediate products, DVAR significantly increases by 0.151 5 units. Conclusion: Industrial agglomeration can improve the overall DVAR of the wood industry through two ways: the pool effect of labor, the sharing effect of intermediate inputs and the spillover effect of knowledge and technology to promote the increase of enterprise cost markup rate and the reduction of the relative price of domestic intermediate products, but there are industry heterogeneity and enterprise heterogeneity. Therefore, it is necessary to reasonably guide the formation of wood industry agglomeration and optimize the layout. Under the new pattern of dual circulation, taking advantage of technological innovation and talent to drive the wood industry agglomeration and exerting a positive spillover effect in order to promote wood enterprises to gradually reduce their dependence on the international market and achieve a development path based on economic internal circulation through local industrial agglomeration.

Objective: The willingness of farmers to protect wildlife is related to the effectiveness of wildlife protection, and is the endogenous driving force for the harmonious coexistence between human and nature. To explore the impact of wildlife accident and wildlife damage compensation on farmers’ willingness to protect wildlife, to provide theoretical support for preventing and controlling wildlife accident, optimizing wildlife damage compensation mechanism and improving farmers’ willingness to protect wildlife, and to provide decision-making reference for promoting the modernization of harmonious coexistence between human and nature. Method: A theoretical analysis framework was constructed around the wildlife accident, wildlife damage compensation and farmers’ wildlife protection intention. Based on the survey data of 837 farmers in active wildlife areas of Yunnan Province, the effects of wildlife accident and wildlife damage compensation on farmers’ wildlife protection intention were empirically tested using the multiple ordered Logit model. The regulating effect of wildlife damage compensation on the relationship between wildlife damage and farmers’ willingness to protect wildlife was further investigated. Result: 1) The wildlife accident had a negative effect on farmers’ wildlife protection intention. The more severe the wildlife accident, the lower the farmers’ wildlife protection intention; 2) With the increase of wildlife damage compensation level, the impact of wildlife damage compensation on farmers’ wildlife protection intention was first "promoted" and then "inhibited", and the impact mechanism was "inverted U-shaped", with an inflection point at 53.39% of the compensation level; 3) Wildlife damage compensation can regulate the negative impact of wildlife accidents on farmers’ wildlife protection intentions, and play a regulatory role of "weakening" and then "strengthening"; 4) The effects of wildlife accident and wildlife damage compensation on farmers’ wildlife protection intentions are heterogeneous in different regions, different cultural beliefs and different income levels. The regulatory effects of wildlife accident and wildlife damage compensation have a greater impact on farmers in areas with abundant wildlife resources, strong cultural beliefs in wildlife and higher income levels. Conclusion: Wildlife accidents reduce farmers’ willingness to protect wildlife, and wildlife damage compensation plays a nonlinear regulating role of first "weakening" and then "strengthening" in the negative impact of wildlife accidents on farmers’ willingness to protect wildlife. It is suggested that in the process of promoting harmonious coexistence between human and wildlife, we should strengthen the prevention and control of wildlife accidents, optimize the compensation mechanism of wildlife damage, and build a sustainable wildlife protection mechanism.