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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.

Understanding soil respiration ( R s ) response to thinning is an important component of our understanding of belowground carbon (C) dynamics and evaluating effects of forest management on C cycling. Therefore, we partitioned R s into heterotrophic respiration ( R h ) and autotrophic respiration ( R a ) using trenched plots in a 20 year-old Pinus tabulaeformis plantation, subjected to varying thinning intensities, in Shanxi Province, China. Soil respiration was measured using an infrared gas exchange analyzer in untrenched and trenched plots. Rates of soil respiration were measured twice a month from May to October in 2011 and 2012, while soil temperature and moisture were obtained using temperature and moisture probes and data loggers. R s was measured in untrenched plots and R h in trenched plots. Mean R s and R h values were significantly greater in stands subjected to heavy thinning (HT) ( R s = 2.79 μmol CO 2 m −2 s −1 , R h = 2.24 μmol CO 2 m −2 s −1 ) than in the control (CK) ( R s = 2.29 μmol CO 2 m −2 s −1 , R h = 1.81 μmol CO 2 m −2 s −1 ) and low thinned stand (LT) ( R s = 2.48 μmol CO 2 m −2 s −1 , R h = 1.80 μmol CO 2 m −2 s −1 ). The mean R a was greater in the thinned stands ( R a = 0.69, 0.58, 0.55 μmol CO 2 m −2 s −1 in LT, moderate thinned stand (MT) and HT) than CK ( R a = 0.48 μmol CO 2 m −2 s −1 ), possibly the result of increased productivity and root growth in thinned stands. The relative proportion of R h to R s averaged 71.6–79.7% over the four thinned stands. Temperature sensitivity ( Q 10 ) values of R h ranged from 2.16 to 2.75 in the various thinning intensities, with the highest Q 10 value in the control stand. Temperature sensitivity of R a was also affected by thinning ranging from 1.34 to 1.84. The model with the best fitted temperature and moisture factors explained 66.7–77.3% of the variation in R h and 30.2–46.4% in R a among the four thinned stands during two growing seasons.

Turfgrass growth and physiological activities are sensitive to temperatures and are affected by mowing height. Increasing temperatures associated with global climate change may limit photosynthetic capacity of established turfgrass stands. The objective of this study was to determine the effects of mowing height on carbon exchange of a turfgrass system and consequential effects on turfgrass growth in response to temperature variations across the growing season in kentucky bluegrass (Poa pratensis cv. Baron) stands. Mature (8 years old) turfgrass was mowed at 7.6 cm [high mowing height (HM)] or 3.8 cm [low mowing height (LM)] during 2012 and 2013. Both LM and HM plots displayed significant decline in turf quality (TQ), shoot biomass, and canopy photosynthetic rate (Pn) with increasing air temperature above 23–24 °C in both years and the decline was more pronounced for LM plots. Turf plots were carbon emitters when total respiration rate of shoots, roots, and soil (Rtotal) exceeded canopy Pn under high temperatures during July–September but maintained net carbon gain during cooler seasons (May and June) due to greater Pn to Rtotal ratio (Pn:Rtotal). Lowering mowing height accelerated carbon loss by reducing canopy Pn, particularly under high temperatures. Our results suggested that whether mature turfgrass stands fix or emit carbon is heavily dependent on interaction between seasonal temperatures and mowing height gauging whole-stand photosynthetic capacity. Furthermore, increasing mowing height during summer months may offset the deleterious effects of high temperature by maintaining positive carbon balance within the turfgrass system.

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

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.

Forest ecosystems play dominant roles in global carbon budget because of the large quantities stored in live biomass, detritus, and soil organic matter. Researchers in various countries have investigated regional and continental scale patterns of carbon (C) stocks in forest ecosystems; however, the relationship between stand age in different components (vegetation, forest floor detritus, and mineral soil) and C storage and sequestration remains poorly understood. In this paper, we assessed an age sequence of 18-, 20-, 25-, 38-, and 42-year-old Pinus tabulaeformis planted by analyzing the vertical distribution of different components biomass with similar site conditions on Mt. Taiyue, Shanxi, China. The results showed that biomass of P. tabulaeformis planted stands was ranged from 88.59 Mg ha−1 for the 25-year-old stand to 231.05 Mg ha−1 for the 42-year-old stand and the major biomass was in the stems. Biomass of the ground vegetation varied from 0.51 to 1.35 Mg C ha−1 between the five stands. The forest f...

Respiration was measured at daytime during the growing seasons (May–October) of 2011 and 2012 in a young Pinus tabulaeformis plantation with heavy, medium and light intensity thinning and unthinned control plots in Shanxi province in northern China. Soil temperature, moisture, fine root biomass, amounts of soil organic C and litterfall biomass were also measured. We found that immediately following thinning treatments, soil respiration increased by 8 %–21 % compared with the unthinned control plots during both growing seasons. Thinning significantly affected soil respiration and soil temperature with different thinning intensities, while there were no significant differences in soil moisture among the various treatments. During the growing seasons, the soil respiration rates were positively correlated with the soil moisture: the 19.4 %–54.0 % variation in soil respiration rates in the four thinning regimes are explained by the changes in soil moisture. Meanwhile, a positive correlation was found between soil temperature and soil respiration rates at all sites. The best fitting model with temperature and moisture explained 44.3 % of the variation in soil respiration in the high thinning treatment, 27.6 % in the light thinning treatment, 18.6 % in medium thinning and in the control sites during the measuring periods. Overall, soil respiration is better predicted by soil moisture, soil organic C, live fine root biomass and soil temperature when data are pooled for all thinning treatments over the two growing seasons. The best regression model explained 74.7 % of the total variation in soil respiration over the different thinning intensities for the two sampling periods.

Quercus liaotungensis natural secondary forest is an important vegetation formation and has a large distribution area in Lingkong Mountain Nature Reserve, Shanxi Province, China. The spatial patterns of trees at different life stages give important clues about the underlying processes driving regeneration and succession of the forest. In this paper, the trees of a population were mapped, characterized and the spatial distribution patterns and spatial associations of Q. liaotungensis among different life stages (juveniles – J, premature – P, mature – M, overmature – O) were analyzed using O-ring univariate O(r) and bivariate O(subscript 12)(r) statistics. We found that: (1) Q. liaotungensis was a discontinuously regenerating population. (2) The distribution patterns of Q. liaotungensis varied at different life stages. Q. liaotungensis (J) and Q. liaotungensis (M) showed significant aggregations at scale 0–19 m and 0–23 m, respectively. Q. liaotungensis (P) exhibited significant aggregations at the majority...

This study introduces the current situations of the research on the refuge chamber at home and abroad. Aiming at disasters prevented and environment for refuge chamber, it deals with the chamber's protection and positioning, notes for selection of chamber sites, reference sizes and requirements of strength and impermeability. Some designs for survival system in the refuge chamber are structured, including multistage oxygen supply, air cleaning system, temperature and humidity control system, dynamical system, monitoring and communication system, etc.

Although the effect of litter mixture on decomposition has been well documented, few studies have examined the relationships between richness and relative abundance of leaf species in litter mixture and changes in universal fungal communities during the decomposition process in temperate forests. In this study, we used the litterbag method and included three leaf litter species, i.e., aspen (Populus davidiana Dode), birch (Betula platyphylla Sukaczev) and oak (Quercus mongolica Fischer ex Ledebour), to investigate the mass loss rate and diversity of universal fungal communities in each litter treatment, which were sampled in situ after 180, 240, 300 and 360 days of decomposition (between 2012 and 2013) in broadleaved mixed forests in Chinese temperate forests. Eight mixture proportions were examined: pure aspen litter (10A), pure birch litter (10B), pure oak litter (10O), 50% aspen litter mixed with 50% birch litter (5A:5B), 50% aspen litter mixed with 50% oak (5A:5O), 50% birch litter mixed with 50% oak litter (5B:5O), 10% birch litter mixed with 80% aspen litter and 10% oak litter (1B:8A:1O), 30% birch litter mixed with 40% aspen litter and 30% oak litter (3B:4A:3O). Over 360 days of decomposition, approximately 46.6%, 43.6%, 28.0%, 54.4%, 40.2%, 39.5%, 54.5% and 49.46% of litter mass was lost from 10A, 10B, 10O, 5A:5B, 5A:5O, 5B:5O, 1B:8A:1O and 3B:4A:3O, respectively. In addition, the number of fungal denaturing gradient gel electrophoresis (DGGE) bands showed a positive correlation with mass loss rate, indicating a positive feedback between leaf litter decomposition and universal fungal communities in the leaf litter. The results revealed that the 5A:5B, 1B:8A:1O and 3B:4A:3O litter mixtures had a synergistic effect on the litter mixture, while the 5A:5O and 5B:5O litter mixtures had a nearly neutral effect on the litter mixture. Thus, leaf litter species composition and relative abundance seem to be more important than leaf litter richness in driving the direction and magnitude of litter mixture decomposition.

Patterns of biomass and carbon (C) storage distribution across Chinese pine (Pinus tabulaeformis) natural secondary forests are poorly documented. The objectives of this study were to examine the biomass and C pools of the major ecosystem components in a replicated age sequence of P. tabulaeformis secondary forest stands in Northern China. Within each stand, biomass of above- and belowground tree, understory (shrub and herb), and forest floor were determined from plot-level investigation and destructive sampling. Allometric equations using the diameter at breast height (DBH) were developed to quantify plant biomass. C stocks in the tree and understory biomass, forest floor, and mineral soil (0-100 cm) were estimated by analyzing the C concentration of each component. The results showed that the tree biomass of P. tabulaeformis stands was ranged from 123.8 Mg·ha-1 for the young stand to 344.8 Mg·ha-1 for the mature stand. The understory biomass ranged from 1.8 Mg·ha-1 in the middle-aged stand to 3.5 Mg·ha-1 in the young stand. Forest floor biomass increased steady with stand age, ranging from 14.9 to 23.0 Mg·ha-1. The highest mean C concentration across the chronosequence was found in tree branch while the lowest mean C concentration was found in forest floor. The observed C stock of the aboveground tree, shrub, forest floor, and mineral soil increased with increasing stand age, whereas the herb C stock showed a decreasing trend with a sigmoid pattern. The C stock of forest ecosystem in young, middle-aged, immature, and mature stands were 178.1, 236.3, 297.7, and 359.8 Mg C ha-1, respectively, greater than those under similar aged P. tabulaeformis forests in China. These results are likely to be integrated into further forest management plans and generalized in other contexts to evaluate C stocks at the regional scale.

Light-use efficiency (LUE) is used commonly with remotely sensed and meteorological data to monitor terrestrial ecosystem primary production (NPP). Studying the variation in space of LUE is helpful to obtain a deep understanding of the carbon cycles. Spatial pattern of LUE in subtropics evergreen coniferous based on NPP were studied at local level. The results showed that the average of LUE was 0.71 g·MJ−1. LUE tracked closely with NPP and NPP gradually decreased from southeast to northwest in subtropics evergreen coniferous. In a linear regression, longitude, latitude, and precipitation accounted for approximately 50.5 % of the variability in LUE. LUE showed single-peaked curve followed with the increase of precipitation. The highest LUE was reached when the precipitation is about 1200 ∼ 1400 mm. Spatial patterns of the LUE were discussed based on the observation data, which provides very crucial data for further correction, improvement and evaluation of LUE model.

コナラの前生稚樹の生育形は, 主軸伸長型, 側枝伸長型, 萌芽再生型の三つに大別され, さらに九つに細分された.閉鎖林冠下では主軸伸長型と側枝伸長型が, 林冠欠所下では萌芽再生型が多くみられた.前生稚樹の平均年齢は, 閉鎖林冠下では4.1年, 林冠欠所下では14.5年であったO前生稚樹の定着様式には主軸がそのまま伸長して定着するタイプと, 主軸が伸長せず萌芽更新によって定着するタイプの二つが認められた.後者は高齢稚樹で多くみられた.林内の稚樹は成長が悪く, 林縁稚樹に比べて葉面積比およびT/R率が大きかった.前生稚樹の成長は上木の伐採によって著しく促進された.皆伐地の稚樹は皆伐後3年目で乾重量が閉鎖林冠下の稚樹の38倍に増加した.皆伐地における前生稚樹の定着と成長促進には, 除草剤の散布, 施肥, 刈払いの三つの処理の併用が有効であった.ササの枯殺にはフレノック50kg/haの散布が適当であった.ササ密生地への施肥は, かえってササの繁茂を促進し, 稚樹の定着を阻害した.フレノック・施肥・刈払区では, 上木伐採から3年後に優勢稚樹がha当り5-9万本生存し, 樹高約1mに成長した.この結果からフレノックと施肥併用がコナラの更新に有効であることがわかった.