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We assessed the diversity, composition, and distribution of bird species in patches of semi-humid evergreen broad-leaved forest by selecting eight natural forest communities in the central Yunnan Plateau, which is a representative distribution area of semi-humid broad-leaved evergreen forest. Field observations were conducted from April to August 2023 by the sample line and sample point method, and eight survey routes of 3-4 km in length were established. The results showed that 1) A total of 1286 birds were recorded, belonging to 102 species in 7 orders and 30 families. The three most abundant families were Muscicapidae (14 species), Leiothrichidae (9 species), and Phylloscopidae (7 species); 2) Species of Oriental origin, Palaearctic origin, and widespread species accounted for 81.4%, 4.9%, and 13.7% of observations, respectively; 3) The average number of bird species surveyed in forest patches was 32.0±3.5; the Shannon index of birds was lower in secondary, semi-humid evergreen broad-leaved forests (1.536±0.110) than in primary forest communities (2.037±0.100); 4) Species composition exhibited considerable variation between patches, with the presence of dominant and common species, and the difference in rare species; 5) Considering the ecological groups of birds based on diet, invertebrate-eating and omnivorous birds, herbivorous birds, and carnivorous birds accounted for 84.3%, 11.8%, and 3.9%, respectively. The coexistence of birds with similar diets was maintained by diluting interspecific competition, mainly through partitioning of the vertical feeding space. For the conservation of bird species diversity and rare species, all patches of native semi-humid evergreenbroad-leaved forest are of conservation value.

The rhizosphere effect of plants affects soil organic carbon (SOC) mineralization. It is still unclear for the mechanism by which the rhizosphere effect of dominant plants in secondary broadleaved forest habitats invaded by moso bamboo affects SOC mineralization. Taking broadleaved tree species ( Quercus glauca and Cunninghamia lanceolata ) and moso bamboo, dominating respectively in uninvaded secondary broadleaved forest and bamboo forest formed after the invasion as test materials, we investigated rhizosphere effect of plants on the SOC mineralization in laboratory incubation experiments. The results showed that carbon mineralization rates of Phyllostachys edulis (PE), Quercus glauca (QG) and Cunninghamia lanceolata (CL) rhizosphere soils were 20%, 26%, and 21% higher than bulk soils, respectively. Carbon mineralization of bulk soils of QG and CL was 22% and 26% higher, while that of rhizosphere soils was 14% and 11% higher than PE, respectively. The contents of water-soluble organic carbon and organic carbon in rhizosphere soils of the three species were significantly higher than those of bulk soil, and the abundance of rhizosphere soil bacteria was higher than that of non-rhizosphere. The contents of microbial biomass carbon, water-soluble organic carbon, and total nitrogen were important factors influencing carbon mineralization in rhizosphere, while water-soluble organic carbon and microbial metabolic quotient were important factors influencing carbon mineralization in non-rhizosphere. On the whole, the rhizosphere effect increased total SOC mineralization, driving by changes in microbial biomass carbon, water-soluble organic carbon, and total nitrogen content. The results could provide a theoretical basis for plant-soil interaction on soil carbon cycling in bamboo invasion habitats.

Understanding the spatial heterogeneity of soil available medium- and micro-elements in karst area can provide a valuable theoretical guideline for soil nutrient management of karst ecosystem. We collected soil samples at a soil depth of 0-10 cm using grid sampling (20 m×20 m) in a 25 hm 2 (500 m×500 m) dynamic monitoring plot. We further analyzed the spatial variability of soil medium- and micro-elements and their drivers, with classic statistics analysis and geo-statistics analysis. The results showed that the average contents of exchangeable Ca and Mg and available Fe, Mn, Cu, Zn, and B were 7870, 1490, 30.24, 149.12, 1.77, 13.54, and 0.65 mg·kg -1 , respectively. The coefficient of variation of the nutrients ranged from 34.5% to 68.8%, showing a medium degree of their spatial variation. The coefficient of determination of the best-fit semi-variogram models of each nutrient was higher than 0.90, except for available Zn (0.78), indicating a strong predictive power for the spatial variation of the nutrients. The nugget coefficients for all the nutrients were less than 50%, showing a moderate spatial correlation, and the structural factors played a pivotal role. The spatially autocorrelated variation was within the range of 60.3-485.1 m, among which available Zn showed the lowest range and the deepest fragmentation degree. The spatial distribution of exchangeable Ca, Mg, and available B were consistent, with contents in the depression being significantly lower than that in other habitats. The contents of available Fe, Mn, and Cu declined with the increases of altitude and were significantly lower on the hilltop than in other habitats. The spatial variation of soil medium- and micro-elements was closely related to topographic factors in karst forest. Elevation, slope, soil thickness, and rock exposure rate were the primary drivers of spatial variation of soil elements and need to be considered in soil nutrient management of karst forestlands.

Tree mortality is an important ecological process in forests. It is crucial to understand how tree mortality affects spatial patterns and interspecific associations for revealing the mechanisms of tree mortality and community dynamics. We employed the correlation method of spatial point pattern analysis to analyse the variations in spatial patterns and interspecific relations before and after mortality using data obtained from two surveys of a 25 hm 2 plot in the Mulun National Natural Reserve, China. The results showed that most species had an aggregated distribution both pre- and post-mortality. The proportion of species with aggregated distribution reduced slightly post-mortality compared with that for pre-mortality. Increases in the number of species with random distribution at small scale indicated that tree death was not random. At the species level, there were significant positive associations between dead and live trees of the 13 common species at different levels of 0-30 m range, suggesting weak intraspecific and interspecific competition among dominant species. Pre- and post-mortality interspecific associations were mostly positive, which remained stable during the period of two surveys for most species, indicating that the community had reached a rather stable stage. Following tree mortality, the number of species with positive associations increased at 1-30 m scales, whereas the number of species with negative and no associations decreased at most scales. These results indicated that the pressure of interspecific competition was relieved to some extent after individual death.

In situ measurement of albedo is important for estimating ecosystem energy budget and its remote sensing application. However, the measurement method of albedo on sloping land is limited and the difference in temporal variation in albedo between visible and near-infrared bands remains unclear. Taking a deciduous broad-leaved forest at the Maoershan Forest Ecological Station in Northeast China as an example, we explored the temporal variation and influencing factors of albedo for three bands: incident and reflected solar radiation (SR, 300-2800 nm), photosynthetically active radiation (PAR, 400-700 nm), and near infrared radiation (NIR, 700-2800 nm). The temporal difference in albedo measurements between the two installation methods of radiometers was analyzed. The results showed that, in sunny days, the diurnal variation in SR and NIR albedo had an asymmetric U-shaped curve around the local noon, while PAR increased from sunrise to sunset. In cloudy days, the albedo decreased sharply and then tended to be stable. The measurement with parallel sensors to the slope increased the daily mean value of albedo, but reduced the daily asymmetry of SR and NIR. For the whole growing season, the maximum albedos of SR, NIR and PAR in horizontal measurement were 0.16, 0.27 and 0.11, respectively, and the minimums were 0.07, 0.11 and 0.03, respectively. Albedo in the SR and NIR wavebands increased first and then decreased (the peak value was in July), while PAR showed a contrasting pattern. SR albedo was mainly controlled by NIR rather than PAR. The contribution of the influencing factors was ranked in the order of normalized difference vegetation index (61.7%-78.5%, representing leaf area index) > solar altitude angle (15.4%-36.9%) > clearness index (0.4%-36.9%).

The special eco-physiological characteristics of moso bamboo ( Phyllostachys edulis ) facilitate their fast invasion in nature ecosystems. The widespread expansion of moso bamboo causes degradation of adjacent forest ecosystem and change of landscape, as well as soil properties and microbial community composition. However, how moso bamboo expansion affects soil microbial composition is far from fully understood. Herein, we selected four moso bamboo expansion transects with three forest types at the Anji Lingfeng temple forest farm, Zhejiang Province, including evergreen broadleaved forest (BLF), mixed P. edulis and broadleaved forest (MEF) and P. edulis forest (PEF). We examined the effects of moso bamboo expansion on soil properties and soil microbial phospholipid fatty acids (PLFAs). Our results showed that soil pH was higher in moso bamboo forest than in MEF and BLF by 0.37 and 0.32 unit. In contrast, soil organic carbon, ammonium, and nitrate contents significantly decreased. Biomass of soil microbial groups displayed a decreasing trend except arbuscular mycorrhizal fungi, and the microbial richness index (SR) and diversity index ( H ) decreased significantly. In summary, moso bamboo expansion affected soil nutrient and carbon inputs, which was an important factor affecting soil microbial community structure. Results of redundancy analysis showed that changes of soil organic carbon and ammonium content were the main factors driving soil microbial community.

Shrub is an important part of forest ecosystem. Exploring the species composition, structure and spatial distribution of shrub layer can lay an important foundation for further clarifying the mechanisms underlying species coexistence, biodiversity maintenance and community succession. In this study, species composition, spatial distribution, and species diversity of shrub layer were analyzed in 25 hm 2 of Huangguan forest plot. A total of 20716 individual shrubs (with 10463 branches) were recorded in the plot, belonging to 54 species, 45 genera, 28 families. The status of dominant species in the shrub layer was not obvious, with all the importance values being less than 10. The diameter structure of shrub layer vegetation was inverted 'J' type. Shrubs showed aggregated distribution in the plot, with obvious altitude differences in spatial distribution. The diameter structure and spatial distribution of the nine shrub species with the largest abundance in the plot were consistent with the overall situation of shrub layer. With increasing altitude, the Shannon diversity index ( H ) and Simpson dominance index ( D ) did not change significantly, while the Pielou evenness index ( E ) decreased. Those indices decreased with the increases of the abundance of dominant species in tree layer, and E increased with the increase of the number of dominant species in sub-tree layer. The indices of H , D , E were significantly negatively correlated with soil total phosphorus (TP). The H index was significantly positively correlated with soil pH, and the E index was significantly positively correlated with soil total potassium. The shrub layer was rich in species, stable in community structure and well regenerated. The species diversity of shrub layer was mainly affected by the number of dominant species in the tree layer, soil pH, and TP.

To promote the application of lidar technology in estimating standing stocks of the typical conifer stands in Northeast China, i.e. , spruce-fir forest, larch forest, Korean pine forest, Pinus sylvestris var. mongolica forest, we combined the point cloud data obtained by airborne lidar with the data of 800 ground plots and established models of standing stocks for the four conifer stands by stepwise regression and partial least square. Partial least squares method was better than stepwise regression method ( R 2 =0.05-0.15, RRMSE=2.6%-4.2%). Among the three types of feature variables involved in modeling, height variable (selected for 26 times) is more important than others (selected for 12 times and 11 times, respectively). With respect to the accuracy of models established based on the means of the partial least square, they worked best for Korean pine forest ( R 2 =0.79, RMSE=60.92, RRMSE=22.9%) and larch forest ( R 2 =0.76, RMSE=28.39, RRMSE=25.8%), followed by spruce-fir forest ( R 2 =0.81, RMSE=46.96, RRMSE=27.7%) and P. sylvestris var. mongolica forest ( R 2 =0.50, RMSE=55.49, RRMSE=30.4%). This study provi-ded an effective way to estimate standing stocks of four typical conifer stands in Northeast China.

We examined nutrient release and ecological stoichiometric characteristics of litters under N deposition in an evergreen broadleaved forest in Mopan Mountain in central Yunnan. Nylon net bag method was used for in situ decomposition of leaf litter and twig litter. There were four treatments, including control (CK, 0 g N·m -2 ·a -1 ), low nitrogen (LN, 5 g N·m -2 ·a -1 ), medium nitrogen (MN, 15 g N·m -2 ·a -1 ), and high nitrogen (HN, 30 g N·m -2 ·a -1 ). The results showed that after one year of N addition, the contents of C and N in leaf litter, twig litter and soil increased gradually with the increases of N addition rates, with increases of 0.3%-8.2% and 4.9%-69.0%, respectively. C/N gradually decreased with increasing N addition rates, with a decrease of 0.8%-37.8%. There was no significant difference in P content, C/P and N/P of twig litter under different treatments. Treatment duration and N application rate significantly affected the N and P contents and stoichiometric ratios of leaf litter, twig litter and soil. During the 1-year decomposition process, the residual rates of C, N and P in litters were successively in the modes of release, leaching-enriched-released and leaching-enriched. Exogenous N addition significantly inhibited the release process of C, N and P in litter. The contents of C and P in soil were significantly positively correlated with the contents of N and P in litter, while the contents of N in soil were significantly positively correlated with the contents of C and N in litter. There was a significant correlation of stoichiometric characteristics between litter and soils of evergreen broadleaved forest under N deposition. Our results were helpful to understand the response mechanism of litter decomposition process of forest ecosystem to N deposition.

The Qinling Mountain is a natural boundary between warm temperate zone and subtropical zone. While the China Forest Biodiversity Monitoring Network (CForBio) have basically covered most of the climate regions in China, few plots were located in the climate transition zone. Following the field protocol of CForBio and the Center for Tropical Forest Science (CTFS), a 25 hm 2 (500 m×500 m) forest plot was established in Huangguan Nature Reserve in Shaanxi Province, China, in 2019. In this study, we analyzed species composition, flora characteristics, diameter class structure, and spatial distribution patterns of dominant tree species based on the data of all woody species with a diameter at breast height (DBH) ≥1 cm. The results showed that there were 75137 woody individuals with DBH ≥1 cm in the plot (95679 when including branching individuals), belonging to 121 species, 83 genera and 44 families. The flora type at the genera level was mainly temperate, accounting for 71.1% of the total genera, and mixed with some tropical components. The dominant species in the community were obvious, with the number of individuals in the top 5 species exceeding 40% of the total number of individuals, the number of individuals in the top 50 species accounting for 95% of the total number of individuals, and the number of individuals in the remaining 61 species being less than 5% of the total. The diameter distribution of all woody indivi-duals in the plot was inverted 'J' type. Spatial distribution patterns varied across the four most abundant species with importance value >5. The degree of aggregation within species decreased with the increases of scales, while the spatial distribution of different species was affected by environmental heterogeneity. Warm-temperate deciduous broadleaved forest in Qinling Mountains had abundant species, stable community structure and good regeneration, reflecting the typical characteristics of the transition from warm temperate zone to subtropical zone. Environmental heterogeneity might be an important factor affecting the spatial distribution of tree species in the plot.

Forests play an important role in terrestrial carbon cycles. The mechanism underlying carbon balance in temperate deciduous broad-leaved forests is not clear. In this study, net ecosystem exchange (NEE) and environmental factors, including air temperature ( T a ), soil temperature ( T s ), photosynthetically active radiation (PAR), vapor pressure deficit (VPD), soil water content (SWC) and precipitation ( P ) were continually measured using eddy covariance techniques in 2019 in a deciduous broad-leaved forest in Songshan, Beijing. We analyzed the characteristics of NEE and its response to environmental factors. The results showed that, at diurnal scale, the monthly averaged NEE exhibited a "U" shape curve ( i.e ., being a carbon sink over daytime while being a carbon source during nighttime) over the growing season. During the non-growing season, NEE was positive ( i.e ., carbon source) at diurnal scale. At the seasonal scale, NEE exhibited a unimodal curve. The annual cumulative NEE was -111 g C·m -2 ·a -1 . Annual ecosystem respiration was 555 g C·m -2 ·a -1 , while gross ecosystem productivity was 666 g C·m -2 ·a -1 . Carbon sequestration peaked in June, while emission peaked in November. PAR was the dominant factor affecting daytime NEE (NEE d ). VPD was the main factor that indirectly affected daytime NEE d , with an optimal VPD value that maximizes daytime NEE around 1-1.5 kPa. Soil temperature was the main factor affecting nighttime NEE (NEE n ). SWC was a limiting factor for NEE n . Too high or too low SWC would inhibit NEE n , with an optimal SWC value of 0.28 m 3 ·m -3 .

We investigated soil total organic carbon (TOC), recalcitrant organic carbon (ROC), and labile organic carbon (LOC) of evergreen broadleaved forests at different altitudes (400, 600, 800, 1000 and 1200 m) in Guanshan National Nature Reserve, Jiangxi Province, with the aim to understand their altitudinal distribution. The results showed that soil TOC, ROC and LOC contents were the highest in the surface layer and decreased with soil depth. With the increases of altitude, contents of soil TOC, ROC, readily oxidizable organic carbon (ROOC), microbial biomass carbon (MBC), and particulate organic carbon (POC, 0-20 cm depth) increased with a peak at 1000 m and then decreased, whereas soil water-soluble organic carbon (WSOC) contents and POC contents in 20-40 cm layer did not change. In 0-10 cm soil layer, the proportions of ROC to TOC at 800 and 1200 m were significantly higher than those at 400 and 1000 m, while the proportions of LOC to TOC were the highest at 400 m. The proportions of ROC and LOC to TOC in 10-40 cm layer showed a low-high-low tendency along the altitude, with peaks at 1000 and 600 m, respectively. Soil organic carbon fractions were positively correlated with soil moisture, microbial biomass nitrogen, and soluble organic nitrogen. A positive correlation was observed between LOC and ammonium concentration. Our results suggested that altitude significantly affected the distribution of soil organic fractions, with soil ROC, ROOC and MBC being more sensitive to altitudinal changes. Soil ROC and LOC at high altitude were prone to decomposition and transformation under conditions with sufficient water and nitrogen, which reduced soil carbon stability. It was essential to study the dyna-mics of soil organic carbon in high altitude forests under global warming scenarios.

Fine roots play an important role in energy flow and substance cycling in forests. How-ever, the estimates of biomass, production and turnover of fine roots remain large uncertainties, and the mechanism underlying local-scale spatial variation in fine roots is still unclear. In a temperate secondary forest in the Maoer Mountain in Northeast China, we investigated the vertical distribution of fine root biomass and necromass at the 0-100 cm profile and the dynamics, production and turnover rate of fine root in 0-20 cm soil layer. The sequential coring (including the Decision Matrix and the Maximum-Minimum formula) and the ingrowth core (3 cm diameter and 5 cm diameter) were compared in estimating production and turnover rate of fine roots. Forest stand variables that might affect fine roots were also explored. The results showed that 76.8% of fine root biomass and 62.9% of necromass concentrated in the 0-20 cm soil layer, and that both decreased exponentially with increa-sing soil depth. The seasonal variation in both fine root biomass and necromass was not significant in 0-20 cm soil layer, which might be related to the negligible snowfall in winter and the extremely high precipitation in summer. There was no significant difference in the results of the estimated fine root production between two diameter ingrowth cores. After log-transformed, fine root production and turnover rate estimated by the Decision Matrix, the Maximum-Minimum formula and ingrowth cores were significantly different among methods. With the increases of soil nutrient concentrations, fine root biomass/fine root necromass ratio significantly increased, fine root necromass significantly decreased, whereas fine root biomass, productivity, and turnover rate were not related to soil nutrient. There was a significant positive correlation between fine root production and aboveground woody biomass increment in the previous-year but not current-year.

We measured the morphology traits (specific root length, specific root surface area, root tissue density, average root diameter) and architecture traits (root fork, root fork ratio, increase rate of root length, root tip density, root fork density) of fine roots in two mycorrhiza tree species, Castanopsis faberi (ectomycorrhizal) and Schima superba (arbuscular mycorrhizal), in an evergreen broadleaved forest in the middle subtropical zone. Root bags method was used in an in situ nitrogen deposition experiment. The aim of this study was to reveal the differences in the plastic responses of fine root morphology and architecture traits to nitrogen deposition between the different mycorrhizal trees. The plastic responses of specific root length, specific root surface area and root fork to nitrogen addition decreased from the first-order root to the fourth-order root, while root tissue density showed an opposite pattern. Such a result indicated a trade-off between nutrient acquisition and resource maintenance of different fine root orders. Different mycorrhizal tree species adopted diffe-rent adaptation strategies to the variations of soil nitrogen availability. C. faberi adopted an opportuni-stic strategy, which relied on fine root to improve nutrient absorption efficiency, enhanced the capacity of space expansion and in-situ nutrient absorption to focus on rapid nutrient absorption strategy. S. superba did not change fine root morphological traits through the trade-off between nutrient absorption efficiency and root construction cost, but relied more on the complementarity between mycorrhizal fungi and fine root architecture traits for nutrient acquisition. The differences in the cost of maintaining and constructing fine root C between different mycorrhizal trees led to fine root adopting the most suitable nutrient capture strategy.

The species-habitat association analysis facilitates a better understanding of species coexis-tence and community assembly. Here, all trees in a 25-hm 2 broadleaved deciduous forest plot in the Qinling Mountains of North-central China were classified into three life stages ( i.e ., seedling, sapling, and adult). The Torus-translation test was used to examine the species-habitat association. The results showed that the association of species with habitats varied across different species. Most species were significantly associated with high slopes, 95.7% of which showed negative association. 89.5% and 90.9% of tree species were negatively associated with low slopes and ridges, respectively. Most species had positive association with high valley, with only one negative association (0.03%). There were 80, 44 and 23 significant associations with habitats at seedling, sapling and adult stages, respectively, indicating that a greater dependence of seedlings on habitat. 38 species at seedling stage and 25 species at the sapling stage were associated with at least one habitat type, while only 17 species at the adult stage were significantly associated. The effects of habitat on species varied across life stages, showing a weaker species-habitat association at the later stage. Due to the specific environmental demands, most species showed different habitat preferences across life stages.

An experiment with four treatments of control (CK), N addition (100 kg N·hm -2 ·a -1 ), P addition (50 kg P·hm -2 ·a -1 ) and N + P (100 kg N·hm -2 ·a -1 + 50 kg P·hm -2 ·a -1 ) were conducted to examine the responses of plant height, ground diameter, crown width, specific leaf area, and mortality of seedlings to N and P addition. Under P addition, growth rates of plant height and ground diameter of seedlings decreased significantly by 45.1% and 30.3%, respectively. Fertilization affected the mortality of main constructive tree species. N addition significantly increased seedling mortality of Castanopsis carlesii to 25.1%. Fertilization treatment significantly increased mortality of Castanopsis fargesii to 25.1%-31.3%, while N addition and P addition signi-ficantly reduced mortality of Schima superba and Machilus nanmu . Fertilization significantly decreased the importance value of S. superba and C. fargesii in the seedling community. N addition and P addition significantly increased the importance value of M. nanmu seedling. The combined N and P addition significantly decreased Shannon index and Simpson index of the seedling community. Seedling growth was mainly affected by soil ammonium, available phosphorus, total nitrogen, canopy openness, and specific leaf area. Seedling mortality was mainly affected by soil ammonium, available phosphorus and canopy openness. Synthetically, N and P addition affected seedling growth mainly by regulating soil nitrogen and phosphorus availability and changing leaf functional trait. It accelerated the death of ectomycorrhizal tree species ( C. carlesii and C. fargesii ), changed the importance value of constructive species in seedling community, reduced species diversity, and ultimately changed community structure of adult trees in subtropical secondary broad-leaved forest.

Photosynthetically active radiation (PAR) is a key environmental factor affecting the change of net ecosystem exchange (NEE) during the daytime. However, the coordinate system of PAR measured by horizontal radiometers over sloping terrain does not match that of NEE after tilt-corrected of the ultrasonic anemometer. Using the temperate deciduous broad-leaved forest at the Maoershan site with an average slope of 9° and a azimuth of 296° as a case, we investigated the diurnal variations in NEE and its driving factors in the growing season (May to September) of 2016. We assessed the differences in estimating light response parameters and the explanations of NEE by other environmental factors between the PAR measured by horizontal and slope-parallel radiometers. The results showed that the diurnal change of NEE in each month of the growing season presented a morning-afternoon asymmetrically unimodal curve: the value was negative (net carbon absorption) about 2.5 h after sunrise, reached the peak around 12:00, then approached zero again at two hours before sunset. The daily net uptake maximized in July and minimized in May. During the whole growing season, the time-lag and difference in the PAR measured by the horizontal versus slope-parallel radiometers led to that the PAR values measured by the horizontal radiometer increased photosynthetic quantum yield (α) and daytime respiration rate (R d ) by 13.3% and 11.5%, respectively, and decreased the maximum photosynthetic efficiency (A max ) by 7.7%. The light response curves of NEE were asymmetrical in the morning and afternoon, with R d and A max in the afternoon being greater than that in the morning. Weather conditions affected light response parameters: on cloudy days, A max was higher than that in sunny days, the α and R d were lower versus those in sunny days for most conditions. However, the monthly A max and R d were generally higher for horizontally measured PAR than for slope-parallelly measured PAR, especially for A max in the cloudy afternoon. The radiometer-orientation affected the explanation of daytime NEE by air temperature (T a ) and vapor pressure deficit (VPD). The correlation of NEE residual based on the slope-parallel radiometer with T a and VPD (r ranged: 0.013 to 0.197, 0.098 to 0.224) was tighter than that based on the horizontal radiometer (r ranged: 0.082 to 0.219, 0.162 to 0.282) when the negative correlations with T a for September was excluded. Our results indicated that the measurements of PAR on the inclined terrains could cause errors in the environmental interpretations of NEE. Such findings had implications for the radiometric measurement of mountain vegetation and the reasonable interpretation of carbon exchange in terrestrial ecosystems.

To explore the distribution of fungal community in soil of brown coniferous forest in Daxing'anling and its relationship with soil characteristics, soil fungal community structure and diversity in three forest types, light brown coniferous forest, grass brown coniferous forest, and typical brown coniferous forest, were analyzed by high-throughput sequencing technology. The relationship between soil fungal community and soil characteristics was analyzed by R and SPSS 17.0 software. The results showed that soil physical and chemical characteristics differed significantly across the three brown coniferous forests. A total of 111 species belonged to six phyla, 23 class, 46 orders, 74 families and 88 genera were recorded in this study. Ascomycetes and basidiomycetes were dominant phyla. There were significant differences in relative abundance of phyla among three forest types. There was no significant difference in the Ace and Chao1 diversity indices among three brown coniferous forests, whereas there were significant differences in the Shannon and Simpson indices. Results from canonical correlation analysis and correlation analysis showed that both α and β diversity were significantly correlated with soil moisture, soil pH, soil organic matter, soil total nitrogen, and soil total potassium. The results indicated that soil characteristics were important factors affecting soil fungal diversity of brown coniferous forest in Xing'an larch forest in Daxing'anling.

The secondary deciduous broad-leaved forests in northeastern China were generally regenerated from the disturbed broad-leaved Korean pine forests, which are widely distributed in Changbai Mountains area. To understand their composition, structure and stability, a 5.76 hm 2 (240 m × 240 m) forest plot was established in the Mopan Mountains, Jilin Province in 2005, following the standards of the Center for Tropical Forest Science (CTFS). In this study, we analyzed the species composition, size class structure, survival curves of the main tree species and community stability of all woody plants with DBH ≥1 cm. The results showed that a total of 13368 individuals with DBH ≥1 cm were found, belonging to 39 species, 31 genera and 19 families. There were 12 species with importance value ≥1. The species composition was complex, with obvious characteristics of mixed broad-leaved forest. The abundance varied significantly among different species. The rare species and occasional species accounted for 23.1% and 43.6% of the total number of the species, respectively. The size distribution of all individuals showed a reverse "J" shape, which indicated that the community was in a stable and normal growth status. Fraxinus rhynchophylla, Quercus mongolica, Acer mono, and Maackia amurensis out of the six major species fitted reverse "J" form, Juglans manshurica showed an approximately normal distribution, and Ulmus japonica showed a "L" shape distribution. The survival curves of the six major tree species showed that the populations of F. rhynchophylla, Q. mongolica, A. mono, and M. amurensis were stable, J. mandshurica was declining, and U. japonica was growing. Results from the stability analysis of M-Godron indicated that the community was relatively stable at present.

To examine the effects of nitrogen and sulfur deposition on litter decomposition rate, a one-year field experiment was conducted with the litter bag method from April 2013 to April 2014 in an evergreen broad-leaved forest in the Rainy Area of Western China. There were nine treatments with three nitrogen levels and three sulfur levels, including control (CK), low nitrogen deposition (LN, 50 kg N·hm -2 ·a -1 ), high nitrogen deposition (HN, 150 kg N·hm -2 ·a -1 ), low sulfur deposition (LS, 200 kg S·hm -2 ·a -1 ), high sulfur deposition (HS, 400 kg S·hm -2 ·a -1 ), low nitrogen and low sulfur deposition (LNLS), high nitrogen and low sulfur deposition (HSLS), low nitrogen and high sulfur deposition (LNHS), and high nitrogen and high sulfur deposition (HNHS). The results showed that the leaf litter residual rate ranged from 57.0% to 70.7% after one year decomposition. The time of half mass loss ranged from 1.47 to 2.08 years, while the time of 95% mass loss ranged from 6.33 to 9.01 years. Nitrogen deposition had no significant effect on litter decomposition rate. The decomposition rate was significantly increased in LS treatment but significan-tly reduced in HS treatment. The rate was significantly affected by LNHS and HNHS, but unaffected by LNLS and HNLS. In addition, simulated nitrogen and sulfur deposition interacted to affect litter decomposition rate, with antagonistic effects between nitrogen deposition and low-sulfur composite deposition and synergistic effects between nitrogen deposition and high-sulfur composite deposition. In conclusion, sulfur deposition and the combined nitrogen and sulfur deposition affected leaf litter decomposition rate in the evergreen broad-leaved forest, with consequences on the litter decomposition process.

To investigate the effects of stem configuration on leaf biomass allocation in different organs of the current-year shoots at different canopy heights, relationships of biomass in different organs (i.e., leaves, stems, and twigs) and stem configuration (i.e., stem diameter, length, width/length, stem volume and stem density) were analyzed using the data of 69 woody species from the Yangjifeng Natural Reserve, Jiangxi Provence. Standardized major axis (SMA) was used to explore the regression between biomass and stem configuration. The results showed that there was no significant difference in leaf biomass, stem biomass, twig biomass, stem diameter, stem length, stem width/length and stem volume of current year shoots from upper and lower canopy heights and life forms (i.e., evergreen and deciduous woody plants). Stem density differed significantly in the current year shoots at different heights for both evergreen and deciduous woody species. There were isometric relationships among leaf, stem and total biomass of shoots in different canopy heights and in different life forms. Leaf biomass scaled allometrically with stem diameter and volume, with the scaling exponents being not different significantly among different canopy heights. With respect to the stem configuration of the twigs, stem length, stem width/length and stem density contributed less than 24% to the leaf biomass variation in the current-year shoots. On the contrary, stem diameter and volume had greater effects on leaf biomass of the current-year shoots than stem length, stem width/length and stem density. Canopy heights did not significantly affect the allometric scaling relationships between the stem configuration and leaf biomass of the current-year shoots.

The increasing nitrogen deposition due to human activities has impacted forest ecosystems to a large extent. The organic carbon and nitrogen released from decomposing litters play an important role in the formation, stability and transformation of soil organic carbon and nitrogen. We collected soil samples from a subtropical evergreen broadleaved forest experiment with nitrogen deposition [control (0), LN (75 kg·hm -2 ·a -1 ), HN (150 kg·hm -2 ·a -1 )] and litter control (litter retained and litter removal) for eight years. After extracted by solution of K 2 SO 4 , Na 2 B 4 O 7 , Na 4 P 2 O 7 , NaOH, H 2 SO 4 , Na 2 S 2 O 4 and HF step by step, carbon and nitrogen in each extraction was analyzed. The results showed that overall most of soil carbon and nitrogen existed in the Humin fraction, accounting for 33.5% of the total carbon and 33.3% of the total nitrogen. The soluble total carbon and nitrogen extracted by Na 2 B 4 O 7 solution was the highest, followed by NaOH and Na 4 P 2 O 7 solution. The soluble total carbon, soluble total nitrogen and soluble organic nitrogen of soil extracted by three reagents accounted for 46.2%, 47.9%, and 76.5% of the total extractions, respectively. In addition, nitrogen addition significantly increased carbon and nitrogen content in Na 2 S 2 O 4 and Humin fractions. Litter removal reduced carbon content in Na 2 B 4 O 7 , H 2 SO 4 , Na 2 S 2 O 4 and Humin fractions, and nitrogen content in NaOH, HF and Humin fractions. The nitrogen content in the K 2 SO 4 extraction was significantly increased by both litter remained and nitrogen addition. Our results demonstrated that litter and nitrogen added could mutually affect carbon and nitrogen concentration of soil fractions with different chemical stability, with consequences on the process of soil carbon and nitrogen.

Subtropical evergreen broad-leaved forests were selected along an urban (Guangzhou) - suburban (Dinghushan) - rural (Huaiji) gradient in the Pearl River Delta, from which soil samples in different layers were collected. The changes in total organic carbon (TOC), recalcitrant organic carbon (ROC), and active organic carbon (AOC) including readily oxidizable organic carbon (ROOC), microbial biomass carbon (MBC), and water-soluble organic carbon (WSOC) of samples were examined along this urbanization gradient to reveal the influence of urbanization on forest soil organic carbon. Results showed that no significant differences in both TOC and ROC contents were observed in 0-5 cm soil layer along the gradient. In 5-60 cm soil layer, the TOC content was significantly higher in the rural forest than that in the suburban and urban forests, the ROC content was the highest in the suburban forest and no significant difference was observed between the urban and rural forests. The ROOC content was significantly lower in the suburban forest than in the rural (0-60 cm soil layer) and urban (0-10 cm soil layer) forests. The MBC content was significantly lower in the urban forest than that in the suburban and rural forests. The suburban forest had significantly lower WSOC than the urban forest (0-10 cm soil layer). In 0-20 cm layer, the percentage of AOC to TOC of the urban and rural forests was significantly higher than those of the suburban forest, while the percentage of ROC to TOC was the lowest in the rural forest. The significant difference in the percentage of ROC to TOC was only observed in 5-10 cm depth layer between the suburban and urban forests. The results indicated that urbanization increased the active components of soil organic carbon and reduced the stable ones, which could be detrimental to organic carbon accumulation in soils. The rural forest soils were more sensitive to the urbanization.

A detritus-removal experiment was conducted in a temperate deciduous broad-leaved forest in 2007 at the Maoershan Ecological Station in Northeast China, including two treatments: Litterfall removal (NL), root removal (NR). Soil water content, bulk density and the concentrations of soil C, N and P were measured in 2016. The results showed that the C concentration at the surface soil layer (0-10 cm) was reduced by 15.6% and 10.7% for the NL and NR treatments, respectively, while the weighted-mean soil C concentration in 0-30 cm depth was reduced by 7.9% and 4.6%, respectively. The N concentration of the surface layer in the NL treatment decreased by 10.2%, whereas the surface-soil P concentration in the NR treatment increased by 6.6%, resulting in reduced C:P and N:P for both treatments. The standardized major axis regressions showed that the regression slopes between the C, N and P at each layer of 0-30 cm soil depth differed significantly among the treatments. The intercepts of the regressions between soil C concentration and bulk density or soil water content had significant differences among the treatments. The results suggested that detritus-removal caused a coordinated variation in soil C, N and P stoichiometry and physical properties. Therefore, we recommend taking the effect on soil ecological stoichiometry into account in future detritus-removal experiments.

Based on cluster analysis of species vertical stratification, the variations in concentration, allocation and seasonal dynamics of non-structural carbohydrates were investigated in a monsoon broad-leaved evergreen forest in Pu'er, Yunnan Province. The results showed that the concentrations of soluble sugar (3.9%) and nonstructural carbohydrates (NSC, 13.3%) were the highest in the sub-canopy. In contrast, the sugar/starch (0.76) of understory was the lowest. There was no significant difference in starch content among three forest layers. For all forest stories, the soluble sugar was mainly allocated to leaves and the roots had more starch and NSC. The soluble sugar contents in leaves and trunks of sub-canopy species were higher than canopy and understory species. There were no significant differences in soluble sugar content of twigs and roots among three different forest layers. The starch content of leaves increased with decreasing height of forest layers. In contrast, the lowest starch content (10.7%) of roots was in understory. There was no significant difference in starch content of twigs and trunks among three different forest layers. The NSC content of leaves was lower in canopy (10.7%) than that in sub-canopy (12.3%) and understory (12.0%). The lowest NSC content of roots was in understory (14.2%). The lowest sugar/starch of leaves, twigs, and trunks presented in understory, while the lowest sugar/starch of roots presented in canopy (0.79). There were dramatic seasonal variations in concentrations and components of NSC. The concentration of soluble sugar and the sugar/starch were higher in the rainy season than that in the dry season. However, the concentration of starch and NSC were higher in the dry season than in the rainy season. The variations in concentration of NSC and its components among forest layers indicated that species with different heights varied in their utilization strategies of carbon, which partly explained species coexistence.

The effects of Phyllostachys edulis and Oligostachyum oedogonatum expansion on species diversity of broad-leaved forests were investigated in Wuyishan National Nature Reserve, Jiangxi Province, China. Ph. edulis and/or O. oedogonatum expansion changed community structure and species composition. The co expansion of the two bamboos in high intensity (Ph. edulis was 30-50 ind·100 m -2 , O. oedogonatum was 300-500 ind·100 m -2 ) changed the density ratio of arbor and shrub from 2:8 to 1:9, and density ratio of bamboo and tree from 0:10 to 9:1. The main effects of Ph. edulis and O. oedogonatum on the species diversity were significant. Ph. edulis mainly influe-nced arbor layer, while O. oedogonatum influenced shrub layer more, and the interaction effect of two bamboos was not remarkable. There existed addition effects between Ph. edulis and O. oedogonatum on species diversity. The co-occurrence of two bamboos in high intensity decreased the Shannon index of community by 91.3%. Ph. edulis and O. oedogonatum did not compete obviously unless in high density. It was addition effect rather than interaction effect that changed the community structure and reduced species diversity when broad leaved forest suffered invasion by Ph. edulis and O. oedogonatum.

To understand the effects of increasing nitrogen deposition on soil microbial biomass carbon (MBC) and nitrogen(MBN), an in situ experiment was conducted in a natural evergreen broad-leaved forest in Ya'an City, Sichuan Province. Four levels of nitrogen deposition were set: i.e., control (CK, 0 g N·m -2 ·a -1 ), low nitrogen (L, 5 g N·m -2 ·a -1 ), medium nitrogen (M, 15 g N·m -2 ·a -1 ), and high nitrogen (H, 30 g N·m -2 ·a -1 ). The results indicated that nitrogen deposition significantly decreased MBC and MBN in the 0-10 cm soil layer, and as N de-position increased, the inhibition effect was enhanced. L and M treatments had no significant effect on MBC and MBN in the 10-20 cm soil layer, while H treatment significantly reduced. The influence of N deposition on MBC and MBN was weakened with the increase of soil depth. MBC and MBN had obvious seasonal dynamic, which were highest in autumn and lowest in summer both in the 0-10 and 10-20 cm soil layers. The fluctuation ranges of soil microbial biomass C/N were respectively 10.58-11.19 and 9.62-12.20 in the 0-10 cm and 10-20 cm soil layers, which indicated that the fungi hold advantage in the soil microbial community in this natural evergreen broad-leaved forest.

Extreme high temperature is one of important extreme weathers that impact forest ecosystem carbon cycle. In this study, applying CO 2 flux and routine meteorological data measured during 2003-2012, we examined the impacts of extreme high temperature and extreme high temperature event on net carbon uptake of subtropical coniferous plantation in Qianyanzhou. Combining with wavelet analysis, we analyzed environmental controls on net carbon uptake at different temporal scales, when the extreme high temperature and extreme high temperature event happened. The results showed that mean daily cumulative NEE decreased by 51% in the days with daily maximum air temperature range between 35 ℃ and 40 ℃, compared with that in the days with the range between 30 ℃ and 34 ℃. The effects of the extreme high temperature and extreme high temperature event on monthly NEE and annual NEE related to the strength and duration of extreme high tempe-rature event. In 2003, when strong extreme high temperature event happened, the sum of monthly cumulative NEE in July and August was only -11.64 g C·m -2 ·(2 month) -1 . The value decreased by 90%, compared with multi-year average value. At the same time, the relative variation of annual NEE reached -6.7%. In July and August, when the extreme high temperature and extreme high temperature event occurred, air temperature (T a ) and vapor press deficit (VPD) were the dominant controller for the daily variation of NEE. The coherency between NEE T a and NEE VPD was 0.97 and 0.95, respectively. At 8-, 16-, and 32-day periods, T a , VPD, soil water content at 5 cm depth (SWC), and precipitation (P) controlled NEE. The coherency between NEE SWC and NEE P was higher than 0.8 at monthly scale. The results indicated that atmospheric water deficit impacted NEE at short temporal scale, when the extreme high temperature and extreme high temperature event occurred, both of atmospheric water deficit and soil drought stress impacted NEE at long temporal scales in this ecosystem.

In order to reveal the dynamics of canopy vertical structure and its effects on understory regeneration, we built 24 permanent plots (20 m×20 m) on the upslope, midslopeand downslope, respectively, in a typical evergreen broadleaved forest in Damingshan, Guangxi, China. We measured the crown area of each tree with diameter at breast height (DBH)≥1.0 cm, and surveyed the understory regeneration in growing season from 2009 to 2011. The results showed that the total canopy cover significantly increased from 54.0% in 2009 to 67.4% in 2011 after the frozen disaster in 2008. A significant difference existed in the cover and increment of different canopy layers. The canopy cover in the upper layers was markedly higher than that in the middle and lower layers. The increment of canopy coverage in the middle and lower layers was significantly higher than that in the upper layer. There were 55 regenerated woody plant species, and the dominant families and species of regenerated plants were in accord with those in the evergreen broadleaved forest. Biodiversity index of regenerated plants in the same slope position was significantly different among different years, and no significant difference was observed among different slope positions in the same year. The correlation between the coverage at different canopy layers and the species richness and abundance of regenerated plants was not significant. Total canopy cover and canopy coverage at the middle and lower layers were significantly negatively correlated with the Shannon index, Simpson index, and Pielou evenness index of the understory regenerated plants. It indicated that canopy coverage had a significant influence on the regeneration of understory, and the middle and lower layers had a stronger influence on the biodiversity of regenerated plants.

Converting natural forests to plantations significantly affects the characteristics of soil organic carbon (C) pools, due to the changes of vegetation cover and management practices. In this paper, to investigate the effects of conversion from evergreen broad-leaved forest (EBF) to Chinese chestnut plantation (CP) on soil organic C pool, the soils from surface (0-20 cm) and subsurface (20-40 cm) layers were sampled from the above two forests (the CP was converted from the EBF and had been intensively managed for 10 years) in Lin'an City, Zhejiang Province. The soil orga-nic C storage, labile organic C pools, and other basic soil properties were determined. The chemical composition of soil organic C was determined by nuclear magnetic resonance (NMR) technique. Results showed that the soil organic C storage, water soluble organic C (WSOC), hot water soluble organic C (HWSOC), microbial biomass C (MBC) and readily oxidizable C (ROC) concentrations in the surface layer decreased by 19.7%, 34.4%, 25.8%, 30.4% and 25.2%, respectively, after the conversion from EBF to CP. Such values for the subsurface layers decreased by 13.5%, 38.4%, 19.8%, 34.1% and 22.2%, respectively. The O-alkyl C content, aromatic C content and aromaticity of soil organic C in the surface layer decreased signi-ficantly by the land-use conversion, while alkyl C content, carbonyl C content and alkyl C to O-alkyl C (A/O-A) ratio increased signi-ficantly. The O-alkyl C content of soil organic C in the subsurface layer decreased significantly by the land-use conversion, alkyl C content and A/O-A ratio increased significantly, and aromatic C content, carbonyl C content and aromaticity of soil organic C were not changed. In conclusion, conve-rting EBF to CP and subsequent intensive management significantly decreased the soil organic C sto-rage and labile C pool contents and altered the chemical composition of soil organic C.

In order to detect the effects of simulated nitrogen deposition on litter decomposition and degradation of lignin and cellulose, a one-year field experiment of simulated nitrogen deposition has been conducted using litter bag method from November 2013 to November 2014 in an evergreen broad-leaved forest, Rainy Area of West China. Four levels of nitrogen deposition were set, i.e., control (0 g N·m -2 ·a -1 ), low (5 g N·m -2 ·a -1 ), medium (15 g N·m -2 ·a -1 ) and high (30 g N·m -2 ·a -1 ) nitrogen deposition. The results indicated that foliar litter decomposed faster in summer, obviously faster than in the other seasons. N deposition significantly inhibited the decomposition of foliar litter in this evergreen broad-leaved forest. As N deposition increased, the inhibition effect was enhanced. The time of 95% mass loss (T 95% ) of foliar litter due to simulated N deposition was increased by 0.53-1.88 years compared with T 95% of control (4.81 years). N deposition significantly inhibited the degradation of lignin and cellulose. The mass remaining after one year of decomposition of lignin and cellulose in the medium and high nitrogen deposition treatments were significantly higher than that in the control. There was a significant positive linear relationship among mass remaining rate and lignin and cellulose remaining rates. The inhibiting effects of inorga-nic N on degradation of lignin and cellulose explained the inhibitory effect of N on foliar litter decomposition.

Keeping other parameters as empirical constants, different numerical combinations of the main photosynthetic parameters V c max and J max were conducted to estimate daily GPP by using the iteration method in this paper. To optimize V c max and J max in BEPSHourly model at hourly time steps, simulated daily GPP using different numerical combinations of the parameters were compared with the flux tower data obtained from the temperate deciduous broad-leaved forest of the Maoershan Forest Farm in Northeast China. Comparing the simulated daily GPP with the observed flux data in 2011, the results showed that optimal V c max and J max for the deciduous broad-leaved forest in Northeast China were 41.1 μmol·m -2 ·s -1 and 82.8 μmol·m -2 ·s -1 respectively with the minimal RMSE and the maximum R 2 of 1.10 g C·m -2 ·d -1 and 0.95. After V c max and J max optimization, BEPSHourly model simulated the seasonal variation of GPP better.

In order to investigate spatial variations in soil phosphorus (P) concentration and the influencing factors, one permanent plot of 1 hm 2 was established and stand structure was surveyed in Choerospondias axillaries deciduous broadleaved forest in Dashanchong Forest Park in Changsha County, Hunan Province, China. Soil samples were collected with equidistant grid point sampling method and soil P concentration and its spatial variation were analyzed by using geo-statistics and geographical information system (GIS) techniques. The results showed that the variations of total P and available P concentrations in humus layer and in the soil profile at depth of 0-10, 10-20 and 20-30 cm were moderate and the available P showed higher variability in a specific soil layer compared with total P. Concentrations of total P and available P in soil decreased, while the variations increased with the increase in soil depth. The total P and available P showed high spatial autocorrelation, primarily resulted from the structural factors. The spatial heterogeneity of available P was stronger than that of total P, and the spatial autocorrelation ranges of total P and available P varied from 92.80 to 168.90 m and from 79.43 to 106.20 m in different soil layers, respectively. At the same soil depth, fractal dimensions of total P were higher than that of available P, with more complex spatial pattern, while available P showed stronger spatial correlation with stronger spatial structure. In humus layer and soil depths of 0-10, 10-20 and 20-30 cm, the spatial variation pattern of total P and available P concentrations showed an apparent belt-shaped and spot massive gradient change. The high value appeared at low elevation and valley position, and the low value appeared in the high elevation and ridge area. The total P and available P concentrations showed significantly negative correlation with elevation and litter, but the relationship with convexity, species, numbers and soil pH was not significant. The total P and available P exhibited significant positive correlations with soil organic carbon (SOC), total nitrogen concentration, indicating the leaching characteristics of soil P. Its spatial variability was affected by many interactive factors.

We analyzed multidimensional biodiversity (including species diversity, functional diversity, and phylogenetic diversity) of needle-broadleaf mixed forests of Abies fargesii var. faxoniana-Betula spp. and needleleaf forests of A . fargesii var. faxoniana in the subalpine regions of eastern edge of Qinghai-Tibet Plateau. We measured leaf functional traits including leaf area, leaf thickness, leaf dry matter content, and specific leaf area. The results showed that leaf thickness (0.28 mm) and leaf dry matter content (319.86 mg·g -1 ) in the needle-broadleaf mixed forests were significantly lower than in the needleleaf forest (0.39 mm and 371.33 mg·g -1 , respectively), while specific leaf area (192.74 cm 2 ·g -1 ) was significantly higher (100.91 cm 2 ·g -1 ). Leaf area showed no significant difference between the two forest communities (27.88 and 26.63 cm 2 , respectively). The phylogenetic signals of all leaf functional traits were significant, except for leaf thickness. The phylogenetic structure of the needle-broadleaf mixed forests and needleleaf forest communities tended toward divergence. Shannon diversity index, Simpson diversity index, species richness, functional richness, functional dispersion, Rao's quadratic entropy, and phylogenetic diversity in the needle-broadleaf mixed forests were all significantly higher than in the needleleaf forest, and these indices were significantly positively correlated. Competitive exclusion played a major role in the assembly of subalpine forest communities, and species diversity, functional diversity, and phylogenetic diversity exhibited synchrony.

Quercus myrsinifolia is one of the dominant species in the evergreen broad-leaf forest on the southern slope of Shennongjia. The study of spatial distribution pattern and spatial correlation of Q. myrsinifolia population will help to understand population development and potential ecological processes, as well as the structure and biodiversity maintenance mechanism of evergreen broad-leaf forests at the northern edge of the subtropics. Based on forest dynamic monitoring data from one 1 hm 2 permanent plot on the southern slope of Shennongjia, we employed pair correlation functions g ( r ) and marked correlation functions to analyze the diameter structure of the Q. myrsinifolia population, spatial distribution patterns at different diameter classes, and intraspecific and interspecific spatial associations. The results showed that diameter structure of Q. myrsinifolia population exhibited an inverted 'J'-shaped distribution, suggesting a healthy regeneration status and belonging to a growing population type. The spatial distribution showed a decreasing trend in aggregation with increasing diameter. Positive correlations among individuals strengthened with closer diameter classes, while weakening with larger diameter differences. Interspecific spatial associations showed an increasing correlation of Q. myrsinifolia with understory dominant species with increasing spatial scales, but no correlation was observed with canopy-dominant species. Our results suggested that the spatial pattern of Q. myrsinifolia populations on the southern slope of Shennongjia was mainly influenced by habitat filtering, seed dispersal limitation, and intraspecific and interspecific competition. Furthermore, the adaptive strategies of Q. myrsinifolia varied when they coexisted with different species.

Chlorophyll is an important indicator of vegetation health status, accurate estimation of which is important for evaluating forest carbon sink. In this study, we estimated the chlorophyll content of coniferous forests, broad-leaved forests and mixed forest stands at stand and individual tree level by unmanned air vehicle (UAV) hyperspectral data combined with light detection and ranging (LiDAR) point clouds, which improved the non-destructive estimation accuracy of forest chlorophyll. We further comprehensively analyzed the spatial distribution of chlorophyll content at different scales. A total of 36 spectral characteristic variables related to chlorophyll content were screened by correlation analysis based on the fusion of UAV hyperspectral data and LiDAR point clouds combining with the empirical data from ground plots. We constructed multiple models for chlorophyll estimation by using statistical model, including multiple stepwise regression, BP neural network, BP neural network optimized by firefly algorithm, random forest and hybrid data-driven PROSPECT mechanism model. The optimal model was selected to estimate the chlorophyll content. The horizontal and vertical distribution of chlorophyll content at the stand level and individual tree level were analyzed. The results showed that the random forest model was superior to the models constructed by multiple stepwise regression, BP neural network and BP neural network optimized by firefly algorithm for chlorophyll estimation with R 2 and RMSE of 0.59-0.64 and 3.79-5.83 μg·cm -2 , respectively. The accuracy of the mechanism model was the highest, with R 2 and RMSE of 0.97 and 3.40 μg·cm -2 . The chlorophyll contents differed across stand types, with that in broad-leaved forest (25.25-31.60 μg·cm -2 ) being higher than mixed forest (13.52-23.93 μg·cm -2 ) and coniferous forest (6.40-13.71 μg·cm -2 ). There were significant differences in chlorophyll contents the in vertical direction among different stands. For individual tree of different species, the chlorophyll content inside the canopy was lower than that outside the canopy in the horizontal direction. In the vertical direction, there was no difference in chlorophyll content among different layers of Pinus sylvestris var. mongolica canopy. However, significant differences were observed among the upper, middle, and lower layers of Juglans mandshurica canopy. Using the fusion of hyperspectral image and LiDAR point cloud data, the mechanism model driven by hybrid data could effectively improve the accuracy and stability of chlorophyll content estimation at different scales.

Microbial biomass and community structure play a significant role in soil carbon cycling. There is a large amount of organic carbon in the subsoil, but most studies on soil microbial community have focused on the surface soil. The changes and influencing mechanisms of microbial community in subsoil are unclear. We analyzed soil microbial biomass and community structure at different soil depths (0-20, 20-40, 40-60, 60-80, and 80-100 cm) in three typical forests in southwest China, Xishuangbanna tropical rain forest, Ailao Mountain subtropical broad-leaved forest, and Lijiang temperate coniferous forest, by using phospholipid fatty acid technology, to explore their variation characteristics and influencing factors in different forests and soil depths. The results showed that contents of soil organic carbon and total nitrogen decreased gradually, microbial biomass declined significantly. The ratio of Gram-positive bacteria to Gram-negative bacteria (G + :G - ) reduced gradually, while the ratio of fungi to bacteria (F:B) increased with the increasing soil depth. Microbial community turned from G - -dominated which adapted to eutrophic environment into G + -dominated which adapted to oligotrophic environment. The three forest types differed little in soil microbial biomass, but different significantly in microbial community structure. Ailao Mountain subtropical broad-leaved forest and Lijiang temperate coniferous forest had much higher F:B at 0-20 cm than Xishuangbanna tropical rain forest, while significantly higher G + :G - at 0-100 cm in Xishuangbanna tropical rain forest was observed. Results of the redundancy analysis showed that the contents of soil organic carbon and total nitrogen were the main factors determining microbial biomass, with combined explanation of 78.3%. Results of the stepwise regression analysis showed that C:N was the most important driving factor on F:B and G + :G - . The change in microbial community structure and the decrease in biomass along soil profile might strongly affect the dynamics of soil organic carbon in southwest China forests.

Accurately clarifying the applicable spatial scale of 4-Scale model is conducive to improving the accuracy of its application in canopy reflectance simulation of different vegetation types, and to further improving the inversion accuracy of leaf area index, canopy density, and other parameters. Two forest plots (one for broad-leaved forest and one for mixed forest) with each area of 100 m×100 m in Maoershan Experimental Forest Farm, Shangzhi, Heilongjiang, were divided into the spatial scales of 10, 20, 30, 40 and 50 m, respectively. The 4-Scale model was used to simulate forest canopy reflectance. Local mean method, the nearest neighbor method, bilinear interpolation method, and cubic convolution method were used to convert Sentinel-2 images with spatial resolution of 10 m to other scales, with the results being evaluated. The simulated canopy reflectance and remote sensing pixel reflectance were compared and analyzed. The spatial scale of mixed forest and broad-leaved forest suitable for high-precision inversion parameters of 4-Scale model was determined. The results showed that the 4-Scale model underestimated the pixel forest canopy reflectance as a whole. The canopy reflectance of mixed forest and broad-leaved forest had the worst simulation effect at the 20 m scale. Both the root mean square error (RMSE) and the mean absolute error from (MAE) of red and near-infrared band were large. When the scale was >20 m, the simulation effect became better. The applicability of the model was the best when the mixed forest was 40 m and the broad-leaved forest was 30 m. The mean and standard deviation of the reflectance difference between the simulated value and the remote sensing pixel were the minimum in the red and near near-infrared bands, with the minimum RMSE and MAE. The simulation results of mixed forest and broad-leaved forest at 10 m scale were not stable, the rule of mean and standard deviation was inconsistent, and the difference between RMSE and MAE was large under the same band.

Soil dissolved organic carbon (DOC) is the most active part in forest soil carbon pool, the responses of which to climate warming has profound effects on forest carbon cycling. Based on a manipulative soil warming experiment in subtropical evergreen broad-leaved forests, we collected soil solutions in situ and used ultraviolet-visible, infrared and three-dimensional fluorescence spectroscopy analyses to explore the effects of soil warming (+4 ℃, 1 year) on soil DOC quantity and quality along the soil profile. The results showed that soil DOC flux remained constant along the soil profile. Soil DOC mainly included two humic-like fractions and one microbial metabolite. Warming significantly decreased soil DOC flux and the abundance of aromatic and hydrophobic components, and increased the amount of low molecular weight carbohydrates. Furthermore, soil warming increased the relative proportion of humic-like fractions in the surface soil layer (0-10 cm) and microbial metabolite in the deep soil layer (30-40 cm), indicating that warming might accelerate microbial turnover in the deep layer. Overall, soil warming not only decreased soil DOC content, but also simplified the composition of soil DOC in subtropical evergreen broad-leaved forests.

Taking five typical forests ( Betula platyphylla forest, Quercus mongolica forest, B. platyphylla + Pinus koraiensis + Acer mono mixed forest, P. koraiensis forest, and Larix olgensis forest) in Xiaoxing'an Mountains as test objects, we investigated the effects of forest types (broadleaved forest, mixed forest, and coniferous forest) and soil layers (0-10 cm, 10-20 cm, 20-30 cm) on the turnover of exogenous alanine. The results showed that the turnover of soil exogenous alanine varied across different forest types, with significant difference in time and profile. The turnover rate was the highest in the broadleaved forest, followed by the mixed forest, and the lowest in the coniferous forest, with the half-life being 2.6-4.2, 3.6-5.5, and 4.3-7.0 h, respectively. With increasing soil depth, the potential turnover rate of exogenous alanine decreased, the half-life became longer, and soil adsorption of alanine weakened. With the addition of exogenous alanine, the content of ammonium and nitrate significantly increased, with the former being increased by 83.8%-95.3%, 80.9%-94.6% and 73.7%-93.2%, and the latter being increased by 82.9%-94.7%, 82.3%-93.8% and 78.1%-92.5% in the broadleaved forest, mixed forest, and coniferous forest, respectively. The net ammoniation and nitrification rates increased sharply at first and then decreased slowly, which were both positive. Soil layer and forest type as well as their interaction significantly affected the turnover, half-life, ammoniation, and nitrification of exogenous alanine.

Current studies on water conservation capacity of litter in the mountainous area of Southwest China (MASC) mainly focus on local scale. Such results are difficult to evaluate the storage and water-holding capacity of litter in the whole MASC. In this study, the results of site-scale research in the MASC from 2004 to 2021 were collated (a total of 16 research sites and 70 data), as well as the storage and water-holding characteristics of litters of three typical forests in the MASC were compared and analyzed. The results showed that the water-holding processes of litter in coniferous forest, broadleaved forest and mixed forest were similar, which could be divided into three stages: rapid water absorption, gradual slowing, and stable. The absorption rate and duration of different forests were different in each stage. The broadleaved forest had the fastest water absorption rate, while coniferous forest had the slowest with the longest duration to reach stability. There was no significant difference in litter storage among diffe-rent forest types. The total litter storage of coniferous forest, broadleaved forest and mixed forest ranged from 8.26 to 8.82 t·hm -2 . The significant spatial variations of litter storage in semi-decomposed layer resulted in that of total litter storage. The total maximum water-holding capacity of litters of the three forests ranged from 17.85 t·hm -2 to 19.87 t·hm -2 , and the maximum water-holding rate of litter ranged from 200.6% to 228.0%. There was a positive correlation between the maximum water-holding capacity and litter storage in different forests. The total effective retention capacity of three forest litters ranged from 11.66 to 12.29 t·hm -2 , while the total effective retention rate of three forests ranged from 128.1% to 145.2%. There were no significant differences in litter storage and water holding capacity among three forest types with two decomposition degrees in MASC.

As an important geographical boundary, the subalpine coniferous forests in the Qinling Mountains have critical effects on water conservation, biodiversity conservation and climate regulation at the regional and even larger scale. In recent decades, temperature significantly increased in the Qinling Mountains, with significant spatial heterogeneity. An understanding of the responses of the Qinling coniferous trees to climate change is important for the protection and management of mountain forests under climate change. In this study, we synthesized the relationships between the radial growth of coniferous trees and climate at different altitudes in the western, central, and eas-tern Qinling Mountains. The effects of climate change on coniferous trees were investigated from the aspects of radial growth, NDVI, phenology, and species distribution range. Furthermore, know-ledge gaps in the responses of tree growth to climate change and possible future directions in this field were discussed.

"Planting conifer and reserving broadleaved tree" is an effective way to restore broad-leaved pine forest of temperate zone in Northeast China. Liberation cutting can promote the growth of Korean pine ( Pinus koraiensis ) under forest crown and accelerate the succession. However, how liberation cutting intensity affects the growth of Korean pine in secondary forest is still unclear. Taking the "Planting conifer and reserving broadleaved tree" Korean pine forest in Changbai Mountain as the object, we constructed a growth model of diameter at breast height (DBH) and tree height of Korean pine with double dummy variables (liberation cutting intensity and tree classification) to predict the growth of Korean pine plantation under different liberation cutting intensities, i.e . control (no liberation cutting), light-intensity liberation cutting (retaining upper canopy closure 0.6), medium-intensity liberation cutting (0.4), heavy-intensity liberation cutting (0.2) and clear cutting (cutting all upper broadleaf trees) stands. We analyzed the effects of liberation cutting intensities on DBH, tree height, and the ratio of tree height to DBH. The results showed that among six theoretical growth equations, the Gompertz model on the DBH ( R 2 =0.46) and tree height ( R 2 =0.81) was optimal basic model. The R 2 of the DBH model was increased to 0.65 and 0.89, respectively, after the single dummy variable and the double dummy variable were introduced into the basic model, while the R 2 of the tree height model was increased to 0.84 and 0.94. Therefore, the double dummy variable model was the most suitable for predicting the growth of Korean pine. The growth of DBH of pressed tree increased with the increases of liberation cutting intensity (increase by 145.8%-933.3%) during the whole simulation period (0-80 a). Average and dominant trees showed the same pattern at 42 and 60 a. In the early and middle stages of liberation cutting (20 and 42 a), clear cutting and heavy-intensity liberation cutting had similar effects on the height growth of dominant trees (64.8%-68.5%), average trees (100.0%-144.2%), and pressed trees (138.5%-183.9%). The effects of medium-intensity liberation cutting and light-intensity liberation cutting on the height growth were similar (24.3%-35.1%, 56.0%-92.3%, 84.6%-103.2%). While in the middle and late period (42 and 80 a), height growth of three grade trees increased with the increases of liberation cutting intensity. Under each liberation cutting intensity, the ratio of height to DBH of the dominant, average, and pressed trees increased successively, ranging from 0.50-0.95, 0.64-1.23, and 0.73-4.33, respectively. Only the pressed tree decreased with the increases of liberation cutting intensity at 0-80 a. Therefore, about 40 years after the implementation of liberation cutting, the promoting effect of different liberation cutting intensities on DBH growth was significantly weakened, the promoting effect on tree height growth was significantly enhanced, and the ratio of tree height to diameter began to increase. In order to alleviate forest competition, second liberation cutting should be carried out for light-intensity liberation cutting and medium-intensity liberation cutting stands to further release the growth potential of Korean pine, and thinning management should be carried out in clear cutting and heavy-intensity liberation cutting stands.

We analyzed the effects of meteorological factors and soil properties on vertical variation of SOC, based on soil organic carbon (SOC) density in different soil layers (0-10, 10-20, 20-30, 30-50, and 50-100 cm) from 131 mature natural forests in different climate zones in China. The results showed that SOC density decreased with increasing soil depth (0-30 cm) in temperate coniferous, temperate deciduous broadleaved, subtropical deciduous broadleaved and subtropical evergreen broadleaved forests. There were significant regional variations of SOC density in 0-100 cm soil layer. SOC density of 0-100 cm soil layer in temperate coniferous forests was higher than temperate deciduous broadleaved forests, and was higher in subtropical evergreen broadleaved forests than subtropical deciduous broadleaved forests. SOC density was significantly positively correlated with soil clay content, mean annual precipitation, and aboveground net primary production, and significantly negatively correlated with soil pH and mean annual temperature. Mean annual precipitation and mean annual temperature influenced input and output of SOC, while soil pH and clay content affected SOC accumulation. Therefore, protecting mature natural coniferous and evergreen broadleaved forests would benefit forest carbon sequestration in China.

The adaptation strategy of seedlings plays a decisive role in population regeneration. Machilus nanmu is a tree species belonging to Lauraceae, which is national class Ⅱ protected species and one of the dominant species in the evergreen broadleaved forest in Jinyun Mountain, Chongqing. Therefore, it is of great significance to understand the adaptation strategies of M. nanmu seedlings to maintain population regeneration and protect the biodiversity of evergreen broadleaved forest. We studied the temporal dynamics of early adaptation strategy of M. nanmu in Jinyun Mountain in Chongqing and its response to heterogeneous habitats from the perspective of morphology and biomass allocation. The seedlings of M. nanmu were classified into different age stages (stage 1: 1-3 a; stage 2: 4-6 a; stage 3: 7-9 a) under different canopy environments (gap/understory). Stem configurations (except branch angle) and leaf inclination angle of M. nanmu seedlings in the gap were significantly greater than understory at stages 2 and 3. Root configurations (except root diameter) and leaf area were significantly greater than that in the understory at stages 1 and 2. Specific leaf area in the gap was significantly smaller than understory at all three stages. Across all the conditions, biomass distribution was dominated by leaves. From the stage 2, stem biomass distribution of M. nanmu seedlings in the gap was increased, while root biomass distribution was decreased. There was no significant variation in root biomass of M. nanmu seedlings in the understory. The coordination among different organs of M. nanmu seedlings would help their adaptation to different habitats. Root and leaf of M. nanmu seedlings in the gap were significantly correlated, with the correlation changing from positive to negative as the age increased. While in the understory, there was significant positive correlation between root and stem, but no correlation between root and leaf. The slope of SMA equation of branch weight and branch length had significant difference under different canopy environments only at stage 3, while the slope of SMA equation of leaf and root biomass and configuration had no significant difference. Most of the SMA equation intercepts between biomass and configuration differed significantly at stage 2.

In this study, seven sampling sites (glaciers retreated for 0, 10, 30, 40, 50, 80 and 127 years) were chosen along a primary succession sequence in the Hailuogou glacial retreat area in the eastern margin of the Tibetan Plateau, China. The accumulation and cycling characteristics of N and P under different succession stages were analyzed by measuring biomass and N and P contents in surface soil and each vegetation layer. The N and P contents in leaves, branches and roots of tree layers decreased along the succession sequence, whereas the N and P contents in stems were higher in the late succession stage. The changes of N and P contents in litter and soil O layer were consis-tent with those in the leaves and branches of tree layers. Ecosystem N and P storage increased along the succession sequence. Ecosystem N accumulation was mainly dependent on the vegetation layer in the early succession stage. After the community reached the climax, soil became the main N pool of the ecosystem. Vegetation P storage was higher than that in the surface soil after 80 years of glacial retreat. The nutrient accumulation rate in each layer of the ecosystem was rapid in the middle succession stage, with an order of surface soil > tree layer > understory vegetation layer. The nutrient cycling coefficients of N and P in broadleaved forest in the middle stage were higher than those in coniferous forest in the late stage, whereas the N and P utilization efficiency was lower than that in coniferous forest. Therefore, the mechanism of low nutrient cycling and high utilization efficiency of coniferous trees was conducive to the their competition with other species, thus finally forming the climax community.

Based on a long-term simulated acid rain experiment, soil N 2 O emission fluxes were measured using static chambers and the gas chromatography method in a coniferous and broadleaved mixed forest and a monsoon evergreen broadleaved forest in southern China. During the five-year observation periods (2014-2018), soil N 2 O emission fluxes in the two forests showed obvious seasonal variation. The soil N 2 O emission fluxes in wet season were significantly higher than that in dry season, with a large annual variation. Due to the decreases of precipitation, soil N 2 O emission fluxes of the two forests in 2017 and 2018 were generally low. Soil N 2 O emission flux was positively correlated with soil temperature and soil moisture. In the monsoon evergreen broadleaved forest, soil N 2 O emission flux in the control plot was 12.6 μg N 2 O·m -2 ·h -1 . Soil N 2 O emission fluxes under the pH 3.5 and pH 3.0 treatments increased by 42.9% and 61.1%, respectively. Soil N 2 O emission was significantly increased under simulated acid rain in the monsoon evergreen broadleaved forest. Acid rain promoted soil N 2 O emission in the coniferous and broadleaved mixed forest, but without significant difference among the treatments. Under the scenario of increasing acid rain, soil N 2 O emission fluxes in typical subtropical southern China forests would increase, and the magnitude of such increase was different among forest types.

We monitored seed rain in three forest types for two years (2018-2019) in the central part of Greater Xing'an Mountains, and analyzed the seasonal seed rain dynamics, deciduous dynamics, seed rain thousand-grain weight, inter-annual variation of seed rain, and spatial pattern of seed rain of the main tree species in different forest types. The results showed that seed rain of Larix gmelinii and Betula platyphylla in each forest type showed unimodal distribution. The leaf litter amount of coniferous and broad-leaved species ( L. gmelinii , Pinus sylvestris var. mongolica , Picea koraiensis , B. platyphylla and Populus davidiana ) also showed obvious seasonal dynamics, with a peak in the middle and early September. In coniferous and broadleaved mixed forests and coniferous forests, the 1000-grain weight of L. gmelinii at the peak period was significantly greater than that at the initial and final stages. The 1000-grain weight of B. platyphylla in the three forest types did not show obvious seasonal variation. Seed rain of L. gmelinii and B. platyphylla showed obvious inter-annual change. The year 2018 was a large seed set year, whereas 2019 was a year with small seed set. The spatial pattern of all seed rain was mainly dominated by aggregated distribution in both years, which was consistent with that of seedlings and saplings.

The numerical classification and ordination of plant communities can reveal the relationship between plant distribution and environment, with implications on vegetation restoration and forest management. Community types were classified using a clustering method based on 45 forest dynamic plots with each area of 0.04 hm 2 in Wuchaoshan, Hangzhou, Zhejiang Province, China. The ordination of plant community and the relationship between communities and edaphic variables (soil nutrient availability and topography) were explored using redundancy analysis. Results showed there were three community types in the study area, including Schima superba community type, Quercus fabri-Symplocos anomala community type, and Cyclobalanopsis glauca community type. Stem density and basal area of trees were not significantly different among those community types. Species richness in the C. glauca community was higher than that in S. superba community, but not significantly different from the Q. fabri-S. anomala community. Results from the redundancy analysis showed that community distribution was significantly related to edaphic factors. Topographic and soil factors accounted for 46.4% of the total variation in community distribution while total soil phosphorus, available phosphorus, available potassium, elevation, slope, aspect, and canopy openness had significant effects on community composition. Total soil phosphorus, available potassium, and altitude were the main factors influencing community distribution in Wuchaoshan. 53.6% of the total variation in community distribution were not explained, perhaps due to anthropogenic disturbance.

The ENSO events affect climate and fire danger of China. It would be helpful for improving fire danger forecast to understand the impacts of ENSO events on fire weather for various ecological zones in the country. We calculated the fire weather index (FWI) using the daily climatic dataset (V3.0) of international exchange weather stations in China during 1951-2016. The burned areas in forests for each ecological zone in 2001-2016 were derived from MODIS fire products. Temperature, precipitation, FWI and burned areas in fire season were estimated for each ecological zone by ENSO events (weak, medium, strong, and super strong El Niño events and weak, medium, and strong La Niña events). The results showed that there were 19 El Niño events and 14 La Niña events during 1950-2016. The average daily maximum temperature of the spring fire season increased significantly in the northwestern region with the influence of strong or super strong El Niño event, while the temperature reduced significantly in the medium El Niño event for mid-temperate semi-arid grassland. Precipitation in fire season generally increased in El Niño events in southern and southwestern forest regions. It would be reduced in most areas affected by the low and medium intensity La Niña event, but be increased during the strong La Nina event. The fire weather indices of southern forest regions decreased due to the weak El Niño event. The FWI of the northern forest regions increased with the strong or super strong El Niño event, and reduced in the southern and southwestern forest areas. There was a significant spatial difference on the FWI for some ecological zones with the impacts of the El Niño/La Niña events. The burned areas showed a consistent change trend with seasonal severity rating (SSR) during 2001-2016 when the SSR changed significantly for the regions of deciduous broad-leaved forest in humid/semihumid areas of warm temperate zone, broad-leaved forest in the middle north subtropical humid areas, and broad-leaved forest in tropical and subtropical humid areas. The burned areas in the rest regions were not affected by the ENSO events.