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Plant functional traits have been shown to vary with environmental conditions. However, we lack empirical data on how plant functional traits of different plant life forms respond to environmental factors. We studied the influence of environmental conditions on the distribution of plant functional traits in a Quercus wutaishanica forest with the aim of exploring the patterns of functional traits across different life forms and determining the driving factors of functional trait variation at fine spatial scales. We collected data on environmental factors (soil nutrients and soil moisture, canopy variables, topography) of 70 20 m × 20 m plots. Leaves were harvested from 26 species (4 tree species, 7 shrub species and 15 herbaceous species), and community-weighted mean (CWM) trait values for leaf area (LA), leaf mass per unit area (LMA), leaf carbon content (LCC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and leaf potassium content (LKC) were calculated. We also measured the height (H) of plants. The importance of biotic and abiotic factors in controlling plant functional traits was quantitatively assessed using redundancy analysis (RCA). Regression was used to determine relationships between CWM trait values and environment variables. We found that plant functional traits varied with life forms of plants. LA, LMA and LCC of trees were greater than those of the understory, whereas LNC, LPC and LKC of herbaceous were greater than those of trees. Responses of plant functional traits to environmental factors varied with different life forms. The combined effect of canopy, topography and soil factors had a greater impact on plant functional traits in understory layer than tree layer. General linear models showed that openness is the main factor affecting various functional traits of undergrowth plants, and the relationship between the element content in leaves of herbaceous plants and environmental factors is greater than that of shrub plants. The strong correlation of plant functional traits and environmental factors at fine spatial scales indicates that Q. wutaishanica forests have high spatial variability. Considering the variation of traits in different life form of plants and their interactions with biotic factors, it provides further insights into ecological mechanisms of shaping plant communities and driving plant community dynamics.

The stoichiometric ratios of elements in microorganisms play an important role in biogeochemical cycling and evaluating the nutritional limits of microbial growth, but the effects of thinning treatment on the stoichiometric ratio of carbon, nitrogen, and phosphorus in microorganisms remain unclear. We conducted research in a Larix principis-rupprechtti Mayr. plantation to determine the main factors driving microbial carbon (C): nitrogen (N): phosphorus (P) stoichiometry following thinning and the underlying mechanisms of these effects. The plantation study varied in thinning intensity from 0% tree removal (control), 15% tree reduction (high density plantation, HDP), 35% tree reduction (medium density plantation, MDP), and 50% tree reduction (low density plantation, LDP). Our results indicated that medium density plantation significantly increased litter layer biomass, soil temperature, and other soil properties (e.g., soil moisture and nutrient contents). Understory vegetation diversity (i.e., shrub layer and herb layer) was highest in the medium density plantation. Meanwhile, thinning had a great influence on the biomass of microbial communities. For example, the concentration of phospholipid fatty acids (PLFA) for bacteria and fungi in the medium density plantation (MDP) was significantly higher than in other thinning treatments. Combining Pearson correlation analysis, regression modeling, and stepwise regression demonstrated that the alteration of the microbial biomass carbon: nitrogen was primarily related to gram-positive bacteria, gram-negative bacteria, soil temperature, and soil available phosphorus. Variation in bacteria, actinomycetes, gram-positive bacteria, gram–negative bacteria, and soil total phosphorus was primarily associated with shifts in microbial biomass carbon: phosphorus. Moreover, changes in microbial biomass nitrogen: phosphorus were regulated by actinomycetes, gram-negative bacteria, and soil temperature. In conclusion, our research indicates that the stoichiometric ratios of elements in microorganisms could be influenced by thinning management, and emphasizes the importance of soil factors and microbial communities in driving soil microbial stoichiometry.

Forest thinning management practices such as thinning play a major role in the process of soil organic carbon (SOC) sequestration, however, the mechanism for SOC variations is still unclear. The objectives of this study were to estimate SOC stock and its active chemical components following a short term density adjustment of stand woods. Three treatments, low intensity thinning (removal of 15% of the trees, three 25 ∗ 25 m repeated plots), moderate thinning (30% removal), and heavy intensive thinning (50% removal) were compared to control plots with no thinning three years before sampling of soil carbon composition. A number of carbon components (i.e. SOC; soil total nitrogen, TN; permanganate oxidizable C, POXC; dissolved organic carbon, DOC; microbial biomass carbon, MBC) were measured in five soil layers within the Larix principis-rupprechtii plantation throughout the growing seasons of 2015 and 2016. Results indicated both SOC content and its active component, POXC content, were maximized under the moderate density adjustment (p

Leaf area index (LAI) is a key factor that determines a forest ecosystem’s net primary production and energy exchange between the atmosphere and land surfaces. LAI can be measured in many ways, but there has been little research to compare LAI estimated by different methods. In this study, we compared the LAI results from two different approaches, i.e., the dimidiate pixel model (DPM) and an empirical statistic model (ESM) using ZY-3 high-accuracy satellite images validated by field data. We explored the relationship of LAI of Larix principis-rupprechtii Mayr plantations with topographic conditions. The results show that DPM improves the simulation of LAI (r = 0.86, RMSE = 0.57) compared with ESM (r = 0.62, RMSE = 0.79). We further concluded that elevation and slope significantly affect the distribution of LAI. The maximum peak of LAI appeared at an aspect of east and southeast at an elevation of 1700–2000 m. Our results suggest that ZY-3 can satisfy the needs of quantitative monitoring of leaf area indices in small-scale catchment areas. DPM provides a simple and accurate method to obtain forest vegetation parameters in the case of non-ground measurement points.

Soil organic carbon (SOC) and total nitrogen (TN) are critical indicators of soil quality and play a pivotal role in key biogeochemical process (i.e. soil carbon and nutrient cycling). Many studies have assessed soil organic matter and nutrients individually in different ecosystems. However, appropriate sampling density for accurate estimation of the spatial distribution of SOC in subalpine forests and quantification of the relative importance of influencing factors remains uncertain. In this study, a combination of conventional analytical and geostatistical methods was used to analyze the spatial variability and patterns of SOC and TN along a soil profile. A total of 444 soil samples, taken from three layers down to 60 cm, were collected from the Jieshigou catchment area (5.64 km 2 ) of Mount Taiyue in northern China. Results show that a large spatial variability of SOC and TN appears in upper 40 cm along an elevation and vegetation gradient, while strong spatial autocorrelation is present below 40 cm (40-60 cm). Range and degree of spatial autocorrelation for SOC were slightly larger than those of TN; All the same, both showed clustered spatial distribution. A distribution map of Kriging revealed that both SOC and TN concentrations in the Jieshigou catchment area decreased from west to east along the direction of the valley, which coincides with the overlay of topographic features. More than 40% of the variance in SOC and TN contents could be explained by topographical indices and normalized difference vegetation index (NDVI). SOC and TN significantly increased (from 23.6 to 56.8 g kg − 1 ) with age of larch plantations in the surface layer. Our results suggest that a stratified random sampling was proved a sufficiently reliable way for estimating the spatial distribution of SOC and TN.

Plantation management practices may influence carbon dioxide (CO2) uptake dynamics; however, the responses of carbon losses, such as soil respiration, to management (e.g. thinning) have not been sufficiently studied. We evaluated the effects of forest thinning (no thinning (NT), low thinning (LT), medium thinning (MT), and high thinning (HT) and organic matter manipulation (intact soil (untreated control, UC), exclusion of aboveground litter (EL), and exclusion of both aboveground litter and roots (ELR)) on soil respiration in a Larix principis-rupprechtii plantation. During the period from 2015–2018, soil respiration was continuously monitored from May to October (growing season). Meanwhile, soil temperature and soil moisture at a depth of 5 cm were also measured. In addition, three soil samples were collected to measure biochemical properties of soil. We found that mean soil respiration (Rs) was significantly greater in MT than that in NT (by 21.5 %). RS in HT was significantly greater than NT in 2015 (by 25.0 %) and then finally lower than NT (14.8 %) in 2018. However, RS in LT compared with NT showed no response to thinning during our observation period. The organic matter manipulation also affected soil respiration. Mean reduction of soil respiration in EL (REL) and in ELR (RELR) compared to Rs ranged from 25.9%–39.2% and 40.8%–53.6% across all thinning regimes, respectively. The temperature sensitivity (Q10) values of RS, REL, RELR ranged from 2.23 to 2.72, 2.21–2.60, and 2.31–2.90, respectively. The model with the best fitting temperature and moisture factors explained 63.8 % - 75.4 % changes in RS, 65.9 % - 74.7 % changes in REL and 70.4 % - 74.1 % changes in RELR. Stepwise regression analyses showed that soil temperature, ratio of soil carbon and nitrogen in the topsoil explained the pattern of RS across the thinning scenarios. REL showed a high sensitivity to changing in some soil chemical properties and hydrolases activities, whereas RELR showed a high sensitivity to changing in microbial activity combined with temperature and pH of soil. Overall, our data show that the response of organic matter inputs to thinning has an important impact on soil CO2 fluxes of plantation, and emphasize the difference of the response between aboveground and underground organic matter inputs to soil CO2 fluxes.

In hilly area of North China, massive deforestation of natural forests and extensive use of agricultural lands have resulted in severe soil degradation. Soil organic carbon (SOC) and total nitrogen (STN) are crucial to soil quality. However, knowledge on the efficiency of changes in SOC under various land uses in these areas is very limited. To address this problem, a study was conducted in Songjiagou Catchment of Mount. Taiyue to evaluate the impact of land use change on SOC sequestration and STN accumulation. The results showed that compared with cropland, the SOC stock of shrub land was 10.8% higher and that of forestland 39.8% higher. Comparative values were 55.9% and 64.7% higher for nitrogen accumulation over the entire soil profile. Among that, the topsoil layer in cropland contained 40.7% of the SOC stock and this layer of the secondary shrub 43.6%. It appears that inappropriate tillage practices and anthropogenic disturbances imply a considerable loss of carbon sequestration. Ground litter biomass and live biomass were considered as the main influence factors of STN and SOC variance in surface soil. As well, soil properties, such as bulk density and pH value, were found to have significant and negative effect on SOC and STN concentrations. Therefore, we conclude that the change of land use from cropland to secondary shrub and restoration of forest plantation can improve SOC and STN concentrations and stocks.

Changes in the concentration of soil nitrogen (N) or its components may directly affect ecosystem functioning in forestry. Thinning of forest stands, a widely used forestry management practice, may transform soil nutrients directly by altering the soil environment, or indirectly by changing above- or belowground plant biomass. The study objectives were to determine how tree stem density affects the soil N pool and what mechanisms drive any potential changes. In this study, N and its active components were measured in the soil of a Larix principis-rupprechtii plantation across two full growing seasons, in 12 (25 × 25 m) plots: (low thinning, removal of 15% of the trees, three plot repetitions), moderate thinning (MT) (35% removal) and heavy thinning (HT) (50% removal) and no thinning control. Environmental indices, like the light condition, soil respiration, soil temperatures, and prescription, were measured in the plots also. Results indicated that soil total nitrogen (STN) was affected by tree stem density adjustments in the short-term; STN generally increased with decreasing tree stem density, reaching its highest concentration in the MT treatment before decreasing in HT. This pattern was echoed by the DON/STN ratio dissolved organic nitrogen (DON) under MT. A lower DON/STN was measured across the seasons. Microbial biomass nitrogen (MBN) and the SOC/STN (soil organic carbon (SOC)) ratio and density treatments influenced MBN concentration and inhibited SOC/STN. MT tended to accumulate more STN, produce lower DON/STN and had a generally higher microbial activity, which may be partly ascribed to the higher MBN value, MBN/STN ratio and lower DON/STN. The water conditions (soil moisture), light and soil temperatures could partly be responsible for the N pool dynamic in the different density treatments.

Plant growth and ecosystem production are limited by nitrogen (N), however, the mechanisms of N limitation in terrestrial carbon (C) sequestration in soil remains unclear. To examine these mechanisms N was deposited at rates of 0, 50, 100, and 150 kg N ha−1 yr−1 for two years in a subalpine Larix principis-rupprechtii plantation. Soil C and N components were measured three times encompassing the entire growing season (spring, summer, and autumn) in the second year of the experiment. Results showed that N-deposition affected soil organic carbon (SOC) in the upper soil layer (0–10 cm) especially in the summer season. Dissolved organic carbon (DOC) played the key role in C loss under the high-N treatment (p

Forest soils sequester a large amount of carbon (C) and have a significant effect on the global C balance. Forests are commonly managed to maintain certain age structures but the effects of this management on soil C pools (kg C m−2) is still uncertain. We compared 40-year-old (1GF) and 24-year-old (2GF) plantations of Larix principis-rupprechtii in North China. Specifically, we measured environmental factors (e.g., soil temperature, moisture, and pH), the active C and nitrogen (N) pools (e.g., soil organic C, soil total N, dissolved organic C and N, microbial biomass C and N), and soil processes (e.g., C mineralization and microbial activity in different seasons) in five soil layers (0–50 cm, 10 cm for each soil layer) across the growing seasons in three 25 m × 25 m plots in each age class (1GF and 2GF). Findings indicated that the soil organic C pool in the older 1GF forest (12.43 kg C m−2) was significantly higher than 2GF forests (9.56 kg C m−2), and that soil temperature in 1GF forests was 9.8 °C, on average, 2.9% warmer than temperature in 2GF forests. The C lost as carbon dioxide (CO2) as a result of mineralization in the 2GF plots may partly explain the lower soil organic C pool in these younger forests; microorganisms likely drive this process.

Background Soil microbial communities and their associated enzyme activities play key roles in carbon cycling in terrestrial ecosystems. Soil microbial communities are sensitive to resource availability, but the mechanisms of microbial regulation have not been thoroughly investigated. Here, we tested the mechanistic relationships between microbial responses and multiple interacting resources. Methods We examined soil carbon properties, soil microbial community structure and carbon-related functions under nitrogen addition and plant inputs removal (litter removal (NL), root trench and litter removal (NRL)) in a pure Larix principis-rupprechtii plantation in northern China. Results We found that nitrogen addition affected the soil microbial community structure, and that microbial biomass increased significantly once 100 kg ha−1 a−1 of nitrogen was added. The interactions between nitrogen addition and plant inputs removal significantly affected soil bacteria and their enzymatic activities (oxidases). The NL treatment enhanced soil microbial biomass under nitrogen addition. We also found that the biomass of gram-negative bacteria and saprotrophic fungi directly affected the soil microbial functions related to carbon turnover. The biomass of gram-negative bacteria and peroxidase activity were key factors controlling soil carbon dynamics. The interactions between nitrogen addition and plant inputs removal strengthened the correlation between the hydrolases and soil carbon. Conclusions This study showed that nitrogen addition and plant inputs removal could alter soil enzyme activities and further affect soil carbon turnover via microbial regulation. The increase in soil microbial biomass and the microbial regulation of soil carbon both need to be considered when developing effective sustainable forest management practices for northern China. Moreover, further studies are also needed to exactly understand how the complex interaction between the plant and below-ground processes affects the soil microbial community structure.

Microbial communities and their associated enzyme activities play key roles in carbon cycling in ecosystems. Forest thinning is likely to change the soil properties and feedbacks on the structure and function of microbial communities, consequently affecting microbial regulation on the soil carbon process. However, few studies have focused on the mechanism of how thinning affects the quantity and stability of soil carbon. To reveal the influence of thinning on soil carbon and to explore the regulated key factors, this study was conducted in a pure Larix principis-rupprechtii Mayr plantation with different thinning intensity (light, medium, and high) in Shanxi province, China. Soil properties (soil pH, soil water content, soil organic carbon, and soil microbial biomass carbon) were measured. Meanwhile, soil microbial communities were examined with the method of phospholipid fatty acid (PLFA), and soil enzyme activities were measured as indicators of soil microbial functions. The results showed that medium and high thinning has positive effects on soil organic carbon, microbial biomass carbon, soil microbial abundance, and soil enzyme activities. Actinomycetes and gram-negative bacteria were the major factors to affect soil microbial community function relating to carbon decomposition. Soil pH contributed to actinomycetes and gram-negative bacteria through direct influences on arbuscular mycorrhizal fungi. Moreover, there were strong correlations between soil pH and microbial community to control soil carbon turnover. The increasing of soil microbial abundance and the microbial regulation on soil carbon in forest thinning need to be considered for sustainable forest management practices in northern China.

Thinning is a common management practice in forest ecosystems. However, understanding whether thinning treatment will change the availability of phosphorus (P) in soils, and the effect of thinning on the seasonal dynamics of soil P fractions, are still limited. The objective of the present study was to assess seasonal variations in soil P fractions under different forest thinning management strategies in a Larch (Larix spp.) plantation in northern China. To accomplish this, we examined soil P fractions, soil physical&ndash, chemical properties, and litter biomass under control (CK), light (LT), moderate (MT) and high thinning (HT) treatments. Data were collected during the growing season of 2017. We found that most P fractions varied seasonally at different soil depths, with the highest values occurring in the summer and autumn. When compared to CK, MT enhanced the inorganic P (Pi) concentration extracted by resin strip (R-Pi). Labile organic P (Labile Po), moderately labile P and total P (TP) also increased in both MT and HT treatments irrespective of season. In contrast, less-labile Pi and Po fractions were lower in LT than in CK, especially when examining deeper soil layers. Our results suggest that LT leads to a strong ability to utilize Po and less-labile Pi. Moreover, the effect of thinning did not tend to increase with thinning intensity, P availability was maximized at the MT. Ultimately, we show that MT can improve soil P bioavailability and is recommended in Larix principis-rupprechtii Mayr. plantations of North China. Our results emphasize that the effect of thinning management on soil microenvironment is an important basis for evaluating soil nutrients such as soil P bioavailability.