Aims As an important part of the ecosystems of Central Asia and the whole world, forest growth dynamics of the boreal forest in Altai Mountains can affect global thermal radiation, carbon balance and so on. Therefore, it is crucial to explore the main factors affecting tree radial growth of the boreal forest in Altai Mountains.
Methods We selected Pinus sibirica in Kanas National Nature Reserve of Xinjiang as the target tree species, and established tree-ring chronology of P. sibirica. To explore the influence of competition and climate on radial growth of P. sibirica in the Altai Mountains, Xinjiang, we analyzed the relationships among the cumulated basal area increment (BAI), competition index and climate factors at different time intervals by applying various methods like linear mixed effect model and correlation analysis.
Important findings The results of the linear mixed effect model showed that: (1) the BAI over the past 30 years can be best predicted by the sun of competitors’ diameter at breast height (SDBH). (2) Significant positive correlations were found between the standard chronology, and mean air temperature, mean maximum air temperature and mean minimum air temperature in March. (3) The highest value of the cumulated BAI was observed when air temperature was from 0 to 5 °C, and the competition index was below 100. The lowest value of the cumulative growth occurs when air temperature reaches -10 °C and the competition index exceeds 300. Tree radial growth of subject trees was influenced by both the diameter at breast height of the competing trees and the early growing season air temperature. Competition plays a more important role in affecting radial growth of P. sibirica than climate factors in this area. Therefore, our results would provide a scientific basis for forest management of P. sibirica in Kanas National Nature Reserve of Xinjiang.

Aims The subject of this study was to investigate warming effects on leaf stomatal traits, anatomical structure and photosynthetic traits of four common tree species in subtropical evergreen broad-leaved forest of southern China, and to compare their physiological adaptability to warming. Our study aims to provide a theoretical basis for better predicting the tree growth of native forests in a warming climate.
Methods One-year-old seedlings of Syzygium rehderianum, Ormosia pinnata, Castanopsis hystrix and Schima superba were selected and exposed to two levels of temperature (ambient temperature and infrared heater warming). Leaf stomatal traits, anatomical structure and photosynthetic characteristics were measured to represent the abilities of stomatal regulation, leaf tissue regulation and nutrient maintenance, respectively.
Important findings For Syzygium rehderianum, warming decreased its leaf sponge tissue thickness, photosynthetic nitrogen-use efficiency (PNUE) and photosynthetic phosphorous-use efficiency (PPUE). Seedling of O. pinnata exposed to warming showed increased stomatal conductance, photosynthetic rate, PNUE and PPUE, but decreased stomatal density, leaf thickness and palisade tissue thickness. For C. hystrix, warming decreased the stomata size, but did not affect its photosynthetic rate. Seedling of Schima superba exposed to warming showed lower stomata density, leaf palisade tissue thickness, photosynthetic rate, PNUE and PPUE, but higher stomata size. These results suggested that O. pinnata, Syzygium rehderianum and Schima superba could reduce their leaf thickness to acclimate to warming conditions. The abilities of stomatal regulation, nutrient maintenance, photosynthetic rate and PNUE varied among these tree species. Warming would be beneficial for the growth of O. pinnata due to increased photosynthetic rate, PNUE and PPUE, while not for Syzygium rehderianum and Schima superba, the two dominant tree species of native forests. This study indicated that, with projected climate change, O. pinnata may replace Syzygium rehderianum and Schima superba as a new dominant tree species in the subtropical evergreen broad-leaved forest for its stronger adaptability to warming.

Aims Due to fast-growing and high drought stress tolerance, Leucaena leucocephala has been widely used for afforestation in degraded tropical forests worldwide, but it is also a global invasive exotic species. Studies have shown that fast-growing can help L. leucocephala successfully invade subtropical forests. In this study, we aimed to investigate whether fast-growing and high drought stress tolerance can help L. leucocephala invade tropical rain forests.
Methods The pioneer community of tropical rain forest which had been invaded by L. leucocephala in the Baopoling Mountain, Sanya, China was the research object. Through the t-test, we compared the differences in key functional traits that were related to growth rate (photosynthesis rate, stomatal conductance and transpiration rate) and drought stress tolerance (leaf turgor loss point) in both wet and dry seasons between L. leucocephala and eight dominant native species of pioneer community of tropical rain forest. And the principal component analysis (PCA) was used to investigate whether these functional traits can best discriminate between Leucaena leucocephala and the eight dominant native species.
Important findings Leucaena leucocephala could be invariably growing fast (photosynthesis rate, stomatal conductance and transpiration rate much higher than native species) from wet to dry seasons and had higher drought stress tolerance (leaf turgor loss point much lower than native species) in the dry season. The results of PCA showed that these functional traits could significantly discriminate between L. leucocephala and the eight dominant native species. Therefore, invariable fast-growing from wet to dry season and high drought stress tolerance in the dry season make L. leucocephala successfully invade pioneer communities of tropical rain forests. In the future, these functional traits can be used to select many native species to perform biological control of L. leucocephala in other tropical forests.

Aims Pinus yunnanensis var. tenuifolia is an ecologically and economically important timber tree located at the junction of Yunnan, Guizhou and Guangxi, China. The natural distribution area represents a typical habitat of hot-dry valley. This paper aimed to describe the association between variation patterns of cone and seed traits (CST) and the geo-meteorological factors, explore its ecological adaptability, and provide a reference for the genetic resources conservation, evaluation and utilization.
Methods We sampled eight wild populations of P. yunnanensis var. tenuifolia distributed along the Nanpan-Hongshui River basin. The CST among and within populations were analyzed via discriptive statistics and nested ANOVA. Correlations between CST and geo-meteorological were evaluated based on Pearson and canonical correlation coefficients. Principal component analysis and Mantel test were applied to reveal the geographic variation pattern.
Important findings Abundant variations of eleven CST among and within populations were indicated by the extremely significant difference of nested ANOVA results (p < 0.001). The variation within population was the main source (the average coefficient of phenotypic differentiation V_ST = 18.65%), and generally, the V_ST of cone traits (24.22%-39.88%) were larger than those of seed and wing traits (4.14%-13.80%), indicating more environment selection pressure on the cone traits. Majority of CST was positively correlated (though part of variable-pairs statistically insignificant) with latitude and longitude, annual average temperature, and negatively correlated with relative humidity and annual rainfall. This result suggests that the CST of P. yunnanensis var. tenuifolia is subjected to strong environmental selection, especially to temperature and relative humidity, prompting the species to adapt the hot-dry environment. Eight natural populations of P. yunnanensis var. tenuifolia were divided into three groups via principal component and cluster analysis. The two Luodian populations (WJ and DT) in the east were grouped into one group, and their cones and seeds were large. A population (BW) of Xingyi in the southwest belonged to a separate group, and its cones and seeds were small. The other populations were grouped together, and their CST fell between the first two groups. On the whole, the CST in P. yunnanensis var. tenuifolia increased from west to east. Mantel test exhibited a significant spatial structure among populations, and the variation pattern of populations was consistent with that of the cline.

Aims Euryodendron excelsum, an extremely endangered species of Theaceae, is endemic to China. However, there are few studies on the cause of population structure change of E. excelsum, and its conservation strategy is not perfect. We studied the age structure and dynamics of the E. excelsum population, compared them with the research results in 2007, and analyzed the changes of the E. excelsum population in the last ten years, so as to provide scientific reference for the effective protection and management of the E. excelsum population.
Methods Based on field investigation data, the values of parameters such as standard life table, survival curve, killing power and life expectancy curve were established, and the structure status of the E. excelsum population was analyzed as well. The community composition was analyzed using DET’s multiple analysis method.
Important findings (1) The analysis of population dynamic indices showed that dynamic indices (V_pi and V′_pi) of the wild E. excelsum population were all less than 0. The survival curve of the whole population generally fit a Deevey-III type curve, suggesting a declining population. The number of young individuals was abundant, but impaired development, and hence cannot support the population growth in time. (2) The analysis of survival curve, killing power and life expectancy showed that the sapling, small tree II and middle tree II obstructed the natural population renewal. (3) The Sanjia and Bajia group seedlings of E. excelsum decreased by 39.3% and 71.9%, respectively. The seedling conversion rate of Sanjia group was nearly 1/2 times lower than the Bajia group of E. excelsum. Human interference was the main driver of population decline of E. excelsum. In addition, the conservation strategy that has been implemented is not suitable for the current situation.

Aims The adjustment of leaf traits and biomass allocation is an important way for plants to adapt to environmental changes. Revealing the responses of biomass allocation and leaf traits of Dodonaea viscosa seedlings to nitrogen and phosphorus concentrations, is crucial to understand the adaptation strategies of D. viscosa under the changes of nitrogen and phosphorus.
Methods Seedlings of D. viscosa were planted under nitrogen concentrations (3, 5, 15, 30 mmol·L^-1) and phosphorus concentrations (0.25, 0.5, 1, 2 mmol·L^-1) by sand culture. Plant height, base diameter, biomass allocation, leaf traits and their correlations were quantified.
Important findings The results showed that high nitrogen concentration (30 mmol·L^-1) increased the height, diameter, leaf nitrogen concentration, and biomass accumulation of D. viscosa, and there were no significant differences of the traits under other concentrations (3, 5, 15 mmol·L ^-1). Compared with the high nitrogen level, other treatments significantly reduced the biomass accumulation and leaf nitrogen concentration, and significantly increased the root:shoot biomass ratio and nitrogen utilization efficiency. With the increase of phosphorus concentration, the biomass of D. viscosa increased significantly. Low phosphorus concentrations (0.25, 0.5 mmol·L^-1) significantly constrained the growth of D. viscosa, and the root:shoot biomass ratio and phosphorus utilization efficiency did not change significantly. Low phosphorus conditions increased the specific leaf area and the leaf:stem biomass ratio, and decreased leaf dry matter content significantly. Under the nitrogen treatment, leaf nitrogen concentration was negatively correlated with the root:shoot biomass ratio, while under phosphorus treatment, leaf nitrogen concentration was positively correlated with specific leaf area. Height, diameter and total biomass of D. viscosa were negatively correlated with the root:shoot biomass ratio, and positively correlated with leaf nitrogen concentration under the condition of nitrogen treatment, indicating that the adjustment of root:shoot biomass ratio and leaf nitrogen concentration played an important role in adapting to nitrogen limitation. However, under the condition of phosphorus treatment, height, diameter and total biomass were negatively correlated with specific leaf area, and positively correlated with leaf dry matter content, indicating that the adjustment of leaf structural traits was of great significance in adapting to changes of phosphorus. Our findings suggest that the biomass allocation, leaf traits and their relationships responded differently to changes in nitrogen and phosphorus, and the effects of nitrogen or phosphorus on plant traits should be discriminated in the future.

Aims The objective was to investigate the responses of soil extracellular enzyme activities to carbon input alteration and warming in a subtropical evergreen broad-leaved forest of Ailao Mountain, Yunnan, southwest China.
Methods This study was based on two soil depths (0-5 and 5-10 cm) for four treatments under a long-term soil warming experiment in a subtropical evergreen broad-leaved forest of Ailao Mountain, Yunnan, southwest China. Potential activities of β-glucosidase (BG), polyphenol oxidase (POX), peroxidase (PER), β-1,4-N-acetylglucosaminidase (NAG) and acid phosphatase (AP) and their stoichiometric ratios were measured. Soil physical and chemical properties were also analyzed.
Important findings The results showed that in the control treatment, activities of all enzymes except POX decreased significantly with soil depth. Compared with the control treatment, long-term litter removal significantly reduced AP and BG activities at 0-5 cm soil depth, but had no significant effect on NAG, PER and POX activities at both 0-5 and 5-10 cm soil depths. Long-term root removal significantly reduced BG activity at 0-5 cm soil depth, while increased PER activity at both soil depths. Long-term root removal and warming treatment significantly reduced AP and BG activities at 0-5 cm soil depth, but had no significant effect on activities of other enzymes at both soil depths. The results of redundancy analysis showed that soil water content and NH₄⁺-N content were likely important factors driving the changes soil enzyme activities among treatments. This research provides critical information on the activities of soil enzymes related to carbon, nitrogen and phosphorus cycling in response to global change in this subtropical forest ecosystem.

Aims This study aims to explore the effects of dissolved organic matter (DOM) from different plant sources on subtropical forest soil enzyme activities in order to provide a scientific basis for soil carbon cycling under rainfall leaching conditions in different forest ecosystems of subtropical areas.
Methods Three kinds of DOM, extracted from the fresh leaves of Cunninghamia lanceolata, Schima superb, and Phoebe zherman, were added to the soils of C. lanceolata plantation. Soil treated with deionized water of the same amount as the DOM solution served as the control. Incubation of treated and control soils was conducted for 25 days in the laboratory. The physical and chemical properties, microbial biomass, and enzyme activities of the soils were determined after incubation.
Important findings The results showed that, compared with the control treatment (CT), soil total organic carbon (SOC) content, soil total nitrogen (TN) content, and carbon-nitrogen ratio had no significant changes after adding DOM. However, the TN of treatment with added C. lanceolata leaf DOM (CL) was significantly lower than that of treatments with added S. superb leaf DOM (SL) and P. zherman leaf DOM (PL), and the carbon-nitrogen ratio in CL was significantly higher than that in SL and PL. The three treatments with added DOM increased soil dissolved organic carbon (DOC) content and dissolved organic nitrogen (DON) content overall. There was no significant change in soil microbial biomass carbon (MBC) content after all three DOM inputs, while the microbial biomass nitrogen (MBN) content in CL and SL treatments was reduced by 50.9% and 51.1%, respectively, compared to CT. However, MBN content in PL treatment was increased by 54.0% than CT. DOM input significantly increased the activities of β-glucosidase, cellobiohydrolase, and peroxidase in comparison with CT, but significantly decreased the activity of polyphenol oxidase. In addition, both β-glucosidase and cellobiohydrolase activities showed the following characteristics: CL > SL > PL. The results of correlation analysis showed that the contents of SOC, TN and MBN and the activities of β-glucosidase and cellobiohydrolase of the treatments with DOM were significantly correlated with the DOC content and humification index (HIX) of added DOM. In addition, soil MBN content and polyphenol oxidase activity were positively correlated with the pH value of added DOM. The results of redundancy analysis (RDA) showed that the key factors causing the change in soil enzyme activities after DOM input were DON and DOC content. In general, differences in the properties of DOM obtained from different plant sources affect the activities of soil carbon-acquisition hydrolase. DOM input increases the availability of soil carbon and nitrogen, and elicits different responses from the four carbon-acquisition enzymes. This study provides a theoretical basis for exploring the process of carbon cycling in the rain-rich subtropical forest ecosystem.

Aims The objective was to explore the characteristics of soil nitrogen mineralization in the rhizosphere soils of trees, shrubs, and herbs in plantations and their variations among different species, forest types, and seasons.
Methods The rhizosphere soils of trees, shrubs (Loropetalum chinense, Adinandra millettii, and Eurya muricate), and herbs (Woodwardia japonica and Dryopteris atrata) were sampled in the early growth season (April) and the vigorous growth season (July) in Cunninghamia lanceolata, Pinus massoniana, and Pinus elliottii plantations at Qianyanzhou Ecological Research Station, Taihe, Jiangxi. Net mineralization rate (N_min), net ammonification rate (N_amm), net nitrification rate (N_nit), soil chemical properties, and microbial properties were measured.
Important findings The results found that, 1) Species, forest types, and sampling seasons significantly affected N_min, N_amm, and N_nit. Understory plants showed a higher seasonal sensitivity of rhizosphere soil N_nit than trees did in P. massoniana plantations and P. elliottii plantations. It means that rhizosphere soil N_min and N_amm of trees were significantly higher than those of most of the understory plants in April, but rhizosphere soil N_min and N_amm of the understory plants significantly increased and showed no difference with those of trees in July. This finding was consistent with the variance analysis of comprehensive scores by principal component analysis. Generally, rhizosphere soil N_min and N_nit in C. lanceolata plantation were higher than those in P. massoniana and P. elliottii plantations. Rhizosphere soil nitrogen mineralization in July was higher than those in April. 2) Soil ammonium nitrogen, nitrate nitrogen, soil total nitrogen concentration, and soil microbial nitrogen concentration were the main factors affecting net nitrogen mineralization of rhizosphere soil. Soil chemical properties contributed to 29.2% of the variation of rhizosphere soil nitrogen mineralization, which was significantly higher than soil microbial properties. Consideration of the seasonal variations of soil nitrogen mineralization in the rhizosphere of understory plants and their influencing factors will provide an important foundation for accurately evaluating nutrient cycling in the plantation ecosystem.

The ecological “green-core” area of Changzhutan urban cluster is located in the center of red soil hilly region of Southern China, and the northern vegetation sub-zone of mid-subtropical evergreen broad-leaved forests. In this area, the vegetation is dominated by secondary forests, and the vegetation types are diverse. It is representative of the current vegetation in red soil hilly region of South China, and hance can provide a good platform for the research of regional vegetation succession dynamics and vegetation restoration. We set up 50 plots with a unified and standardized method, and then the species composition, quantitative characteristics, and habitat information of the main vegetation types in the area were investigated. The importance values of species in the tree layer, shrub layer and herb layer were calculated, and the vegetation type of each community were identified and named according to the compilation and research standard of Vegegraphy of China. The community species composition and characteristics were described, and the original data of 50 plots divided into 10 vegetation formations, 22 alliances and 33 associations were provided, including 43 forest plots, 5 shrub plots, 1 grassland plot and 1 swamp plot.