Aims The shrublands of northern China have poor soil and nitrogen (N) deposition has greatly increased the local soil available N for decades. Shrub growth is one of important components of C sequestration in shrublands and litterfall acts as a vital link between plants and soil. Both are key factors in nutrient and energy cycling of terrestrial ecosystems, which greatly affected by nitrogen (N) addition (adding N fertilizer to the surface soil directly). However, the effects and significance of N addition on C sequestration and litterfall in shrublands remain unclear. Thus, a study was designed to investigate how N deposition and related treatments affected shrublands growth related to C sequestration and litterfall production of Vitex negundo var. heterophylla and Spiraea salicifolia in Mt. Dongling region of China.
Methods A N enrichment experiment has been conducted for V. negundo var. heterophylla and S. salicifolia shrublands in Mt. Dongling, Beijing, including four N addition treatment levels (control (N₀, 0 kg N·hm^-2·a^-1), low N (N₁, 20 kg N·hm^-2·a^-1), medium N (N₂, 50 kg N·hm^-2·a^-1) and high N (N₃, 100 kg N·hm^-2·a^-1)). Basal diameter and plant height of shrub were measured from 2012-2013 within all treatments, and allometric models for different species of shrub’s live branch, leaf and root biomass were developed based on independent variables of basal diameter and plant height, which will be used to calculate biomass increment of shrub layer. Litterfall (litterfall sometimes is named litter, referring to the collective name for all organic matter produced by the aboveground part of plants and returned to the surface, and mainly includes leaves, bark, dead twigs, flowers and fruits.) also was investigated from 2012-2013 within all treatments.
Important findings The results showed 1) mean basal diameter of shrubs in the V. negundo var. heterophylla and S. salicifolia shrublands were increased by 1.69%, 2.78%, 2.51%, 1.80% and 1.38%, 1.37%, 1.59%, 2.05% every year; 2) The height growth rate (the shrub height relative growth rate is defined with the percentage increase of plant height) of shrubs in the V. negundo var. heterophylla and S. salicifolia shrublands were 8.36%, 8.48%, 9.49%, 9.83% and 2.12%, 2.86%, 2.36%, 2.52% every year, respectively. Thee results indicated that N deposition stimulated growth of shrub layer both in V. negundo var. heterophylla and S. salicifolia shrublands, but did not reach statistical significance among all nitrogen treatments. The above-ground biomass increment of shrub layer in the V. negundo var. heterophylla and S. salicifolia shrublands were 0.19, 0.23, 0.14, 0.15 and 0.027, 0.025, 0.032, 0.041 t C·hm^-2·a^-1 respectively, which demonstrated that short-term N addition had no significant effects on the accumulation of C storage of the two shrublands. The litter production of the V. negundo var. heterophylla and S. salicifolia communities in 2013 were 135.7 and 129.6 g·m^-2 under natural conditions, respectively. Nitrogen addition promoted annual production of total litterfall and different components of litterfall to a certain extent, but did not reach statistical significance among all nitrogen treatments. Above results indicated that short-term fertilization, together with extremely low soil moisture content and other related factors, lead to inefficient use of soil available nitrogen and slow response of shrublands to N addition treatments.

Aims The objective of the study was to evaluate the dynamics of recalcitrant components during foliar litter decomposition at different forest gap size in Pinus massoniana plantation in the low hilly land, Sichuan basin. Methods The experiment was set up by thinning P. massoniana plantation to establish seven different gap sizes (G1: 100 m², G2: 225 m², G3: 400 m², G4: 625 m², G5: 900 m², G6: 1225 m², G7: 1600 m²). The contents of four recalcitrant components (condensed tannins, total phenol, lignin, cellulose) in foliar litter of two native species (Cinnamomum camphora and Toona ciliata) placed in litterbags at different locations in the forest gaps were evaluated. The litterbags placed under closed canopy were used as the control. Litterbags with air-dried leaves of C. camphora and T. ciliata were placed at center, edge of the gap and under the closed canopy in November 2013, and collected in December 2013, February 2014, May 2014 and August of 2014 for lab analysis. Important findings The results showed that: 1) Forest gap size had significant effect on the content of condensed tannins, total phenol and lignin for T. ciliata in gap center. However, the forest gap size had no significant effect on the content of recalcitrant components in the litters of C. camphora and cellulose content of T. ciliata. With the increase of gap size, except for cellulose content, the other three recalcitrant components content in small and medium sized gaps (G1-G5) were significant lower than in large gaps (G6, G7). 2) The condensed tannis content of T. ciliata at the gap center were significant lower than at the gap edge. The lignin contents at gap center of G3 was significant reduced in the C. camphora litter. The condensed tannins, total phenol, and lignin contents of T. ciliata litter in small and medium gaps significantly decreased. 3) The contents of the four recalcitrant components in both species’ foliar litter changed with time. The contents of condensed tannins and cellulose decreased and the content of lignin increased significantly with time, however, the total phenol content increased initially, and then decreased. Therefore, small and medium sized gaps (100-900 m²) could be the optimal gap sizes to promote the degradation of litter recalcitrant components for two native species in P. massoniana plantations.

Aims Grazing intensity and grazing exclusion affect ecosystem carbon cycling by changing the plant community and soil micro-environment in grassland ecosystems. The aims of this study were: 1) to determine the effects of grazing intensity and grazing exclusion on litter decomposition in the temperate grasslands of Nei Mongol; 2) to compare the difference between above-ground and below-ground litter decomposition; 3) to identify the effects of precipitation on litter production and decomposition. Methods We measured litter production, quality, decomposition rates and soil nutrient contents during the growing season in 2011 and 2012 in four plots, i.e. light grazing, heavy grazing, light grazing exclusion and heavy grazing exclusion. Quadrate surveys and litter bags were used to measure litter production and decomposition rates. All data were analyzed with ANOVA and Pearson’s correlation procedures in SPSS. Important findings Litter production and decomposition rates differed greatly among four plots. During the two years of our study, above-ground litter production and decomposition in heavy-grazing plots were faster than those in light-grazing plots. In the dry year, below-ground litter production and decomposition in light-grazing plots were faster than those in heavy-grazing plots, which is opposite to the findings in the wet year. Short-term grazing exclusion could promote litter production, and the exclusion of light-grazing could increase litter decomposition and nutrient cycling. In contrast, heavy-grazing exclusion decreased litter decomposition. Thus, grazing exclusion is beneficial to the restoration of the light-grazing grasslands, and more human management measures are needed during the restoration of heavy-grazing grasslands. Precipitation increased litter production and decomposition, and below-ground litter was more vulnerable to the inter-annual change of precipitation than above-ground litter. Compared to the light-grazing grasslands, heavy-grazing grasslands had higher sensitivity to precipitation. The above-ground litter decomposition was strongly positively correlated with the litter N content (R² = 0.489, p < 0.01) and strongly negatively correlated with the soil total N content (R² = 0.450, p < 0.01), but it was not significantly correlated with C:N and lignin:N. Below-ground litter decomposition was negatively correlated with the litter C (R² = 0.263, p < 0.01), C:N (R² = 0.349, p < 0.01) and cellulose content (R² = 0.460, p < 0.01). Our results will provide a theoretical basis for ecosystem restoration and the research of carbon cycling.

AimsLitter decomposition is an important ecological process in nutrient cycling and productivity of ecosystems. Our objective is to quantify the differences of litter decomposition and nutrient release (N and P) under the forest and in an alpine lake among the dominant tree species in the Jiuzhaigou National Nature Reserve.
Methods Fresh leaf litters of Abies ernestii, Pinus tabulaeformis, Betula albo-sinensis, and Salix cupularis were collected and placed in bags under the forest and in an alpine lake for a year.
Important findings The mass remaining ratio (MR) of the leaf litters was well predicted with Olson’s decay model (r > 0.93, p < 0.01). The time for 99% decomposition was the shortest for S. cupularis (6.80 a), followed by B. albo-sinensis (10.34 a), A. ernestii (18.88 a), and P. tabulaeformis (27.21 a). These values were 1.48-, 1.55-, 1.80-, and 1.65-folds of the corresponding values in the lake, respectively. Both MR and nitrogen remaining ratio (NR) had significantly negative correlations with the leaf initial N concentration, but significantly positive correlations with the initial C:N. The nutrient release was significantly different among the four species and between the two sites (i.e., forest and alpine lake). The N release of S. cupularis was consistent between forest and the lake (i.e. directly released in the beginning of decomposition), while other species had an obvious N enrichment process before it released. The release of P among was similar among the four species and between the two sites, with a release—enrichment—release pattern. Overall, the leaf litter decomposition appeared as an intricate process that was affected by the litter chemistry and and the environment. The fast litter decomposition in the lake may have a profound influence on the water quanlity in the Jiuzhaigou National Nature Reserve.

Aims Litter is an important component of terrestrial ecosystems, which plays significant roles in carbon and nutrient cycles. Quantifying regional-scale pattern of litter standing crop would improve our understanding in the mechanism of the terrestrial ecosystem carbon cycle, also with help in predicting the responses of carbon cycle of terrestrial ecosystems to future climate change. Our objective was to examine variation in litter standing crop of shrublands along the environmental gradients in southern China.
Methods During 2011-2014, we investigated the litter standing crop at 453 shrublands sites by the stratified random sampling, reflecting climatic and soil attributes across southern China.
Important findings We found that the mean value of litter standing crop in these shrubland ecosystems across southern China was 0.32 kg·m^-2. It was 68% of forest litter standing crop (0.47 kg·m^-2) and was five times higher than that in grasslands (0.06 kg·m^-2) in China. Litter standing crop increased with latitude. Our results showed that litter standing crop was negatively correlated with mean annual temperature, soil total P and soil pH, but not significantly correlated with other environmental variables, including mean annual precipitation, soil carbon, nitrogen and soil organic matter. The conversion coefficient of carbon in litter standing crop was 0.41, which is significantly lower than that of vegetation in shrublands (0.50), resulting in an overestimate in carbon storage of litter standing crop in shrubland up to 22% by applying wrong conversion coefficient. We concluded that litter standing crop of shrublands is an important component in terrestrial ecosystems. Mean annual temperature was the most important environmental variable, accounting for the variation in litter standing crop of shrublands in southern China. To our best of knowledge, this is the first study to quantify variation in litter standing crop of shrublands at the regional scale. Therefore, our study will have important implications for assessing the carbon budget of terrestrial ecosystems in China.

Aims Studying storage of carbon (C), nitrogen (N) and phosphorus (P) in ecosystems is of significance in understanding carbon and nutrient cycling. Previous researches in ecosystem C, N and P storage have biased towards forests and grasslands. Shrubland ecosystems encompass a wide gradient in precipitation and soil conditions, providing a unique opportunity to explore the patterns of ecosystem C, N and P storage in relation to climate and soil properties.
Methods We estimated densities and storage of organic C, N and P of shrubland ecosystems in Northern China based on data from 433 shrubland sites.
Important findings The main results are summarized as follows: the average organic C, N and P densities in temperate shrubland ecosystems across Northern China were 69.8 Mg·hm^-2, 7.3 Mg·hm^-2 and 4.2 Mg·hm^-2, respectively. The average plant C, N and P densities were 5.1 Mg·hm^-2, 11.5 × 10^-2 Mg·hm^-2 and 8.6 × 10^-3 Mg·hm^-2, respectively, and were significantly correlated with precipitation and soil nutrient concentrations. The average litter C, N and P densities were 1.4 Mg·hm^-2, 3.8 ×10^-2 Mg·hm^-2, 2.5 ×10^-3 Mg·hm^-2 and were significantly correlated with temperature and precipitation. The average soil organic C, N and P densities in the top 1 m were 64.0 Mg·hm^-2, 7.1 Mg·hm^-2 and 4.2 Mg·hm^-2, respectively and the former two were significantly correlated with temperature and precipitation. The total organic C, N and P storage of shrublands in Northern China were 1.7 Pg, 164.9 Tg and 124.8 Tg, respectively. The plant C, N and P storage were 128.4 Tg, 3.1 Tg and 0.2 Tg, respectively. The litter C, N and P storage were 8.4 Tg, 0.45 Tg, 0.027 Tg, respectively. Soil is the largest C, N and P pool in the studied area. The soil organic C, N and P storage in the top 1 meter were 1.6 Pg, 161.3 Tg and 124.6 Tg, respectively.

Aims
The concentration of CO₂ and other greenhouse gases in the atmosphere has considerably increased over last century and is set to rise further. Forest ecosystems play a key role in reducing CO₂ concentration in the atmosphere and mitigating global climate change. Our objective is to understand carbon storage and its distribution in forest ecosystems in Zhejiang Province, China.
Methods
By using the 8th forest resource inventory data and 2011-2012 field investigation data, we estimated carbon storage, density and its distribution in forest ecosystems of Zhejiang Province.
Important findings
The carbon storage of forest ecosystems in Zhejiang Province was 602.73 Tg, of which 122.88 Tg in tree layer, 16.73 Tg in shrub-herb layer, 11.36 Tg in litter layer and 451.76 Tg in soil layer accounting for 20.39%, 2.78%, 1.88% and 74.95% of the total carbon storage, respectively. The carbon storage of mixed broadleaved forests was 138.03 Tg which ranked the largest (22.90%) among all forest types. The young and middle aged forests which accounted for 70.66% of the total carbon storage were the main body of carbon storage in Zhejiang Province. The carbon density of forest ecosystems in Zhejiang Province was 120.80 t·hm^-2 and that in tree layer, shrub-herb layer, litter layer and soil layer were 24.65 t·hm^-2, 3.36 t·hm^-2, 2.28 t·hm^-2 and 90.51 t·hm^-2, respectively. The significant relationship between soil organic carbon storage and forest ecosystem carbon storage indicated that soil carbon played an important role in shaping forest ecosystem carbon density. Carbon density of tree layer increased with age in natural forests, but decreased in the order over-mature > near-mature > mature > middle-aged > young forest in plantations. The proportions of young and middle aged forests were larger than any other age classes. Thereby, the carbon storage of forest ecosystems in Zhejiang Province could be increased through a proper forest management.

Aims Forest litter decomposition is an important factor affecting nutrient cycling and ecosystem stability. In a complex system with forest and understory medicinal plants, leachate from the medicinal plants enriched in plant secondary metabolites (PSM) may inhibit litter decomposition and soil enzyme activity of forest trees. Thus, inspection on whether or not this phenomenon exits is one important basis for selecting understory medicinal plants.Methods In this paper, typical forest species Betula albo-sinensis and Eucommia ulmoides and six species of common medicinal plants (Corydalis bungeana, Mentha haplocalyx, Houttuynia cordata, Nepeta cataria, Gynostemma pentaphyllum and Prunella vulgaris) in Qinling Mountains area were taken as objects, and the litter decomposition experiment was carried out. The leachate (water-extraction solution) from the stems and leaves of the medicinal materials were sprayed onto the litter in order to study the effects of leachate from understory plants on forests litter decomposition, nutrient release (carbon, nitrogen and phosphorus) and soil enzyme activity.Important findings For litter of B. albo-sinensis, the decomposition half-life and the turnover period were extended by 76% and 4.3 times, respectively, under H. cordata leachate treatment and the inhibitory effects on the release of carbon and nitrogen were also significant. While under G. pentaphyllum leachate treatment, the half-life of litter decomposition and turnover period were extended by 35% and 2.7 times, respectively, and the inhibitory effects on the release of carbon, nitrogen and phosphorus were all significant. The leachate from these two species of medicinal plants displayed significant inhibitory effects on seven kinds of soil enzymes (invertase, carboxymethyl cellulase, β-glucosidase, dehydrogenase, polyphenol oxidase, protease and phosphatase) activity. For litter of E. ulmoides, the decomposition half-life and the turnover period were extended by 1.7 times and 4.2 times respectively, under H. cordata leachate treatment; while they were extended by 1 times and 9 times respectively, under G. pentaphyllum leachate treatment. The leachate from these two species of medicinal plants displayed significant inhibitory effects on the release of carbon, nitrogen and phosphorus from litter decomposition and the activities of all seven kinds of soil enzymes. Therefore, results suggested that H. cordata and G. pentaphyllum should not be planted under B. albo-sinensis and E. ulmoides forests, or the interplanting density must be low to reduce the inhibitory effects of litter decomposition.

Aims
Forest carbon storage in Nei Mongol plays a significant role in national terrestrial carbon budget due to its large area in China. Our objectives were to estimate the carbon storage in the forest ecosystems in Nei Mongol and to quantify its spatial pattern.
Methods
Field survey and sampling were conducted at 137 sites that distributed evenly across the forest types in the study region. At each site, the ecosystem carbon density was estimated thorough sampling and measuring different pools of soil (0-100 cm) and vegetation, including biomass of tree, grass, shrub, and litter. Regional carbon storage was calculated with the estimated carbon density for each forest type.
Important findings
Carbon storage of vegetation layer in forests in Nei Mongol was 787.8 Tg C, with the biomass of tree, litter, herbaceous and shrub accounting for 93.5%, 3.0%, 2.7% and 0.8%, respectively. Carbon density of vegetation layer was 40.4 t·hm^-2, with 35.6 t·hm^-2 in trees, 2.9 t·hm^-2 in litter, 1.2 t·hm^-2 in herbaceous and 0.6 t·hm^-2 in shrubs. In comparison, carbon storage of soil layer in forests in Nei Mongol was 2449.6 Tg C, with 79.8% distributed in the first 30 cm. Carbon density of soil layer was 144.4 t·hm^-2. Carbon storage of forest ecosystem in Nei Mongol was 3237.4 Tg C, with vegetation and soil accounting for 24.3% and 75.7%, respectively. Carbon density of forest ecosystems in Nei Mongol was 184.5 t·hm^-2. Carbon density of soil layer was positively correlated with that of vegetation layer. Spatially, both carbon storage and carbon density were higher in the eastern area, where the climate is more humid. Forest reserves and artificial afforestations can significantly improve the capacity of regional carbon sink.

Atmospheric nitrogen deposition has increased in the last several decades due to anthropogenic activities and global changes. Increasing nitrogen deposition has become an important factor regulating carbon cycle in grassland ecosystems. Litter decomposition, a key process of carbon and nutrient cycling in terrestrial ecosystems, is the main source of soil carbon pool and the basis of soil fertility maintenance. Elevated nitrogen deposition could affect litter decomposition by raising soil nitrogen availability, increasing the quantity and quality of litter inputs, and altering soil microorganism and soil conditions. Litter decomposition are complex biological, physical and chemical processes, which were affected by abiotic, biological factors and their interactions. The effects of nitrogen deposition on litter decomposition and the underlying mechanisms were discussed in this paper, including the aspactes of soil nitrogen availability, litter production, litter quality, microclimate, soil microorganism and enzyme activities. The main research contents, directions, methods and existing problems of litter decomposition in grasslands were discussed. We also discussed the prospect of future directions to study the interaction and feedback between nitrogen deposition and grassland ecosystem carbon cycling process.

：Aims Stoichiometric ratios of carbon (C), nitrogen (N) and phosphorus (P) are important characteristics of the ecological processes and functions. Studies on population ecological stoichiometry can refine the content of flora chemometrics, determine the limited nutrient, and provide data for process-based modeling over large scale. Phyllostachys edulis is an important forest type, whose area accounts for 74% of total bamboo forest area in Southern China. However, little is known about the ecological stoichiometric in P. edulis. This study aimed to reveal C:N, C:P and N:P stoichiometry characteristics of the “plant-soil-litter” continuum and to provide a better understanding nutrient cycling and stability mechanisms in P. edulis forest in China. Methods The data were collected from the published literature containing C、N、P content in leaf or surface soil (0-20 cm) or littefall in P. edulis forests. Important findings 1) The leaf C, N, P content were estimated at 478.30 mg·g^-1, 22.20 mg·g^-1, 1.90 mg·g^-1 in P. edulis, and the corresponding C: N, C: P and N: P were 26.80, 299.60 and 14.40, respectively. Soil C, N, and P content in 0-20 cm were 21.53 mg·g^-1, 1.66 mg·g^-1, 0.41 mg·g^-1, with ratios of 14.20 for C:N, 66.74 for C:P and 4.28 for N:P. The C, N and P contents were 438.49 mg·g^-1, 13.39 mg·g^-1, 0.86 mg·g^-1 for litterfall, with the litter C:N, C:P and N:P being 25.53, 665.67, 22.55, respectively. 2) In the plant-soil-litter system in P. edulis forest, leaf had higher C:N, litter had higher C:P and N:P, while soil were the lowest. The N, P resorption rate was 39.68% and 54.74%, indicating that P. edulis forest growth and development was constrained by P or by both of N and P in China. 3) N content and N:P in leaf showed a tendency to increase with latitude, while the C:N of leaf declined with latitude. N:P of leaf increased with longitude, but the P content and the C:N of leaf showed a opposite trend. C: N of soil increased with longitude, whereas the N content of soil declined longitude. The N content of litter declined with longitude. 4) The leaf N content was negatively correlated with mean annual temperature and mean annual precipitation, but being more sensitive to temperature than precipitation. The positive correlations between N content and latitude support “Temperature-Plant Physiological” hypothesis, reflecting an adaptive strategy to environmental conditions.

Aims Seasonal litterfall production plays an important role in the carbon and nutrient cycling in forest ecosystems. This study examines the effects of micro-environmental factors on seasonal litterfall dynamics in the forests of Putuoshan Island, Zhejiang Province of eastern China.
Methods The study covers five forest types, including Liquidambar formosana forest, Cinnamomum japonicum and Machilus thunbergii forest, Pinus massoniana forest, Cyclobalanopsis glauca forest, and Distylium gracile forest, in Putuoshan Island. We collected micro-meteorological data, and measured monthly litterfall in stands of the five forest types over one year. Redundancy analysis (RDA) was performed to determine the effects of micro-climatic factors on litterfall production．
Important findings The average annual litterfall production ranged from 3.45 to 5.36 t·hm^-2·a^-1 across five types of forests, albeit no effect of forest types on the litterfall production. The partitioning of litterfall components differed among the five forest types. The seasonal litterfall production exhibited two contrasting patterns, i.e. double climax curve and triple peaks, and varied significantly among the five forest types. Moreover, the peak in the litterfall production mostly occurred in the windy months of the year, such as in April, July and December, which was consistent with the dynamics of wind speed. RDA results showed that components of litterfall production in different months were controlled by different micro-climatic factors. The total, leaves, fruits, and miscellaneous litterfall productions were directly and positively affected by air temperature. Twig litterfall production was positively affected by the overstory wind velocity. Flower litterfall production was negatively affected by air humidity. In summary, forest types had no effects on litterfall production. However, variations in litterfall productions were explained by air temperature, air humidity, and overstory wind velocity in the forests studied.

Aims Existence of forest gaps affects soil moisture, temperature, and decomposer community structure in forest ecosystem; however, it remains largely unknown how the size of gaps affect litter decomposition. The objective of this study was to determine the rate of mass loss of twigs associated with the closed canopy and forest gaps of different sizes in a subalpine forest of western Sichuan, China.

Methods Three forest gaps (FG1: 255-290 m ², FG2: 153-176 m ²; FG3: 38-46 m ²) and three plots under a closed canopy in an alpine fir (Abies faxoniana) forest of western Sichuan, China were selected to conduct a litter decomposition experiment. The air-dried samples of A. faxoniana twigs were placed in nylon litterbags (size 20 cm × 20 cm, pore size 1.0 mm), and those litterbags were placed on the forest floor of experimental plots. The experiment was carried out for a period of four years from November 2012 to October 2016. Mass loss rates associated with different forest gaps and closed canopy were estimated every six months.

Important findings Our results showed that there were significant differences in the depth of snow cover, the temperature and the frequency of freezing and thawing cycles on the forest floor associated with the three gaps and a closed canopy. The snow depth and the temperature were highest in the FG1 and lowest under the closed canopy. After four years, the remaining mass percentages of twig were 59.9%, 59.5%, 62.1% and 55.3% for the FG1, FG2, FG3 and the closed canopy, respectively. Correspondingly, the decomposition constant (k) was 0.127, 0.131, 0.120 and 0.135, and the time for 95% decomposition was 23.6, 22.7, 25.0 and 22.2 a for the FG1, FG2, FG3 and the closed canopy, respectively. Compared with the closed canopy, the mass loss rates in the forest gaps increased in the growing season for the first year and the second year, but reduced in the winter for the first year and fourth year. The effects of gap sizes on the mass loss rates varied with the decomposing periods. The mass loss rates increased with the increase of the gap size in the winter during the first year and the third year decomposing, and reduced with the increase of gap size in the growing season in the third year. Also, the percentage of mass loss was the highest in the first year and increased with the gap size. The percentage of mass loss in the winter was higher than that in the growing season. In conclusion, the formation of forest gaps profoundly affects the litter decomposition in the subalpine forest of western Sichuan.

Aims Changes in snowpack induced by climate change may alter water and heat regimes at the ground surface, thus influencing activities of decomposers and litter decomposition in snow-covered regions. However, effects of snow-depth changes on litter decomposition are unclear. Our objective was to characterize the decomposition dynamics of two contrasting tree species—Korean pine (Pinus koraiensis) and Mongolian oak (Quercus mongolica) in a snow-depth manipulation experiment.

Methods The snow-depth manipulation experiment that included three treatments (i.e., snow-addition, snow-removal, and control) was conducted in a temperate Korean pine plantation in the Maoershan Forest Ecosystem Research Station, Northeast China. Air-dried foliar litter of the pine or oak (10 g litter per bag) was sealed in a nylon litterbag (15 cm × 20 cm). A total of 648 litterbags (3 plots × 3 treatments × 2 tree species × 3 replicates × 12 sampling dates) were placed evenly on the forest floor in October 2014. Three replicate litterbags per species were buried in each treatment plot and sampled 12 times (i.e., freezing onset stage, deep freezing stage, thawing stage, early, middle and late snow-free seasons) during the two-year period (2014-2016) to determine the temporal variation of the decomposition rate. Associated factors (i.e., mean temperature at litter layer, freeze-thaw cycle, available nitrogen and phosphorus at the organic layer) were measured simultaneously.

Important findings Tree species, snow-depth treatment, decomposition stage, and the measured associated factors all influenced the decomposition rates of the foliar litter. The litter mass loss was 52.1%-54.5% for the pine, and 53.9%-59.1% for the oak during the two-year period. The decomposition coefficients for the litter of the two species were the highest in the snow-addition plot, and the lowest in the snow-removal plot. Moreover, the snow-depth manipulation dramatically changed the relative contribution of the mass loss (R ratio) during the snow-covered or snow-free seasons to the yearly total loss. Compared with the control, the snow-addition treatment increased the R ratio during the snow-covered season by 9.1% for the pine and 10.4% for the oak, while the snow-removal treatment increased the R ratio during the snow-free season by 10.4% and 12.7%, respectively. In conclusion, changes in snowpack induced by climate change may significantly affect the foliar decomposition in temperate forests, and also alter the relative contribution of the litter decomposition in the snow-covered and snow-free seasons to the yearly decomposition.

Aims The aims of this study were to explore how vegetation restoration affects leaf, litter and soil C, N, P stoichiometry dynamics and nutrients cycling, and to characterize the homeostasis and nutrient use strategy of plants at different vegetation restoration stages in the mid-subtropical area of China.
Methods Four vegetation types representing the successional sequence in the secondary forests were selected using the “space for time substitution” approach in central hilly area of Hunan Province, China, which consists of Loropetalum chinense + Vaccinium bracteatum + Rhododendron simsii scrub-grass-land (LVR), Loropetalum chinense + Cunninghamia lanceolata + Quercus fabri shrubbery (LCQ), Pinus massoniana + Lithocarpus glaber + Loropetalum chinense coniferous-broad leaved mixed forest (PLL), and Lithocarpus glaber + Cleyera japonica + Cyclobalanopsis glauca evergreen broad-leaved forest (LCC). Permanent plots were established in each community. The organic carbon (C), total nitrogen (N) and total phosphorus (P) contents in leaf, undecomposed litter layer and 0-30 cm soil layer were quantified at each stage. The response and nutrient use strategy of plant to environmental changes were estimated by allometric growth, nutrient use efficiency and nutrient reabsorption efficiency.
Important findings 1) Along vegetation restoration, the leaf C:N, C:P ratios decreased significantly and the highest values were in LVR. Leaf C, N, P contents, soil C, N contents and soil C:N, C:P, N:P ratios increased significantly, in which leaf C, N contents and soil C, N contents, N:P in LCC were higher than those in LVR, LCQ and PLL, and leaf P content and soil C:N, C:P in PLL were higher than those in LVR, LCQ and LCC. Leaf N:P (>20) indicated that all restoration stages were P limited. C, N, P contents and their stoichiometry of litter fluctuated greatly. 2) The relationships between litter and leaf or soil nutrients and their stoichiometry were weak, and the significant correlations were found in the relationships between leaf and soil nutrients and their stoichiometry. Leaf C, N and P were positively correlated with soil C, N, C:N (except leaf C, N contents), C:P and N:P, while leaf C:N was negatively correlated with soil C, N, C:P and N:P, leaf C:P was negatively correlated with soil C content, C:N and C:P, and leaf N:P were negatively correlated with soil C:N. 3) During vegetation restoration, leaf N and P had significantly allometric growth relationship (p < 0.01) with the allometric index being 1.45. The use efficiency of N and P nutrients in leaf showed decreasing trends and reabsorption efficiency showed increasing trends, and the lowest N use efficiency was observed in LCC and the lowest P use efficiency was in PLL, but the highest N, P reabsorption efficiency were both in PLL. 4) The leaf N content had weak homeostasis, and leaf P content had strong homeostasis to maintain P balance in plant under P limited in soil. Vegetation restoration had significant effects on leaf, litter and soil C, N, P contents and their stoichiometry. The C, N, P contents and their stoichiometry had significant correlations between leaf and soil. Plants could adapt to the shortage of soil nutrient supply mainly by reducing nutrient use efficiency and improving nutrient reabsorption capacity. The N and P cycles of the leaf-litter-soil system gradually reached the “stoichiometric equilibrium” during vegetation restoration.

Aims Ecological stoichiometry focuses on the balance of chemical elements in ecological processes, in which the stoichiometric ratios of carbon (C), nitrogen (N) and phosphorus (P) are important features of ecological functions. The objectives of this study were to determine the stoichiometric characteristics in different organs and components of mixed evergreen and deciduous broadleaved forests, and to examine the discrepancy in stoichiometric ratios among different components of the ecosystem and plant organs. Methods We measured the concentrations of C, N and P in different plant organs, litter and soil in a mixed evergreen and deciduous broadleaved forest in Shennongjia of Hubei Province, China, and computed the stoichiometric ratios using the biomass-weighted mean method. Important findings The C concentration, C:N and C:P of different components were ranked in the order of plant community > litter > soil, and concentrations of N and P and N:P in the order of litter > plant community > soil. There were little differences in C concentration among various organs, with the coefficient of variation (CV) much lower and less variable than that for N and P concentrations. Both N and P concentrations were highest in leaves with the lowest CV value; N:P was highest in the bark, but with the lowest CV value in branches. Additionally, there were considerable differences in N and P concentrations in leaves between evergreen and deciduous species. Compared with other forest types, this forest had lower C:P and N:P ratios in plant community, higher C:P and N:P ratios in litter, and the C, N and P stoichiometric ratios in soils were consistent with, and the C:N ratio in ecosystem was lower than, that in subtropical evergreen broadleaved forests. Our findings demonstrated the patterns of differences among components in stoichiometry using the integral biomass-weighted mean method differ from that using the arithmetic mean method in selective organs. Furthermore, the distribution and homeostasis of C, N and P concentrations and their stoichiometric ratios could be closely related to the physiology of different organs.

In order to understand the research progress of litter decomposition and its underlying mechanisms, this paper presented a bibliometric analysis of litter decomposition in China from 1986 to 2018 based on the four common literature databases, including CNKI, ISI Web of Science, ScienceDirect and Springer Link. Litter decomposition researches are mainly from forest ecosystems (65%), and focus on above-ground litter. This suggests that the studies on below-ground litter decomposition should be strengthened in the future. About 68% studies focused on the litters from dominant species, which couldn’t represent the natural decomposition characteristics due to the mixed effects among litters from multiple species. Besides carbon, nitrogen and phosphorus, we should pay more attention to other key chemical components related with decomposition (e.g. K, Fe, Mn, lignin, tannin, etc.) and the heavy metal elements related with environmental pollution. Meanwhile, ecological stoichiometry is an effective method to interlink the biogeochemical cycle in the plant-litter-soil system. Nitrogen deposition and climate change are hot topics in the field of litter decomposition, especially the interactions of multiple factors (e.g. nitrogen, phosphorus, etc.), temperature sensitivity of litter decomposition and underlying mechanisms in permafrost under climate warming context.

Aims Litter decomposition plays a vital role in nutrient recycling of forest ecosystems. The decomposition rate of leaves can vary among tree species with different substrate quality and environmental conditions, such as the supply of exogenous nitrogen (N). However, the effects of exogenous N on leaf litter decomposition of different tree species in subtropical forests with high nitrogen deposition background remain poorly understood. Thus this study was designed to address the effect of N addition on litter decomposition of different tree species in a subtropical forest ecosystem.
Methods Leaf litters of four common tree species with contrasting substrate quality were collected and decomposed in fertilized (50 kg N·hm ^-2·a ^-1) and control (0 kg N·hm ^-2·a ^-1) plots for up to two years by using the nylon bag method, in Sanming Castanopsis kawakamii nature reserve of Fujian Province.
Important findings The litter decomposition rate in control plots ranked as follows: Michelia odora (0.557 a ^-1), Castanopsis carlesii (0.440 a ^-1), Acacia confusa (0.357 a ^-1), Cunninghamia lanceolata (0.354 a ^-1), while the decomposition rate in N addition plots ranked as follows: Michelia odora (0.447 a ^-1), Castanopsis carlesii (0.354 a ^-1), Cunninghamia lanceolata (0.291 a ^-1), Acacia confusa (0.230 a ^-1). Overall, N addition significantly increased the litter mass remaining of Michelia odora, Acacia confusa and Castanopsis carlesii, but not Cunninghamia lanceolata. N addition not only slowed down the release of N, but also retarded the degradation of lignin and cellulose in the decomposition process. Moreover, N addition increased the activities of β-glucosidase (βG) and acid phosphatase, had species-specific effects on the activity of cellulose hydrolase, and decreased the activity of β-N-acetylglucosaminidase and phenoloxidase (PHO). The litter mass loss rate was positively correlated with the activities of carbon acquiring enzyme (βG) in litter layer and the extractives, negatively correlated with carbon concentration, cellulose and lignin, but did not correlate significantly with the initial N concentration. Further analysis found an interactive effect of litter type and N addition on the degradation of cellulose and lignin, but not on dry mass loss. Overall, our results demonstrated that litter chemical components may be better parameters to predict the decomposition rate of leaf litters than the initial nutrient concentrations, and N addition could decrease leaf litter decomposition by inhibiting oxidase (e.g. PHO). We call for further experiments to involve more species and longer time for revealing the response of leaf litter decomposition and its extracellular enzyme activity to N addition.

Aims Litter is the major input source of soil organic carbon and nutrients in natural ecosystems and considered as a key link between above- and belowground carbon cycles. Changes in litter input amount have been proven to exert significant impacts on plant productivity, community structure, and therefore ecosystem function. In Nei Mongol semiarid grasslands, different grassland management practices such as grazing, clipping, and fencing have caused dramatic changes in litter production and input. In addition, as a nitrogen-limited ecosystem, Nei Mongol semiarid grasslands also experienced increasing nitrogen deposition. However, how do changes in litter input and nitrogen addition impact the community productivity and composition of plant functional groups are still unclear in the semiarid grasslands. In this study, our objectives are: 1) to investigate the effects of altered litter input and nitrogen addition on community productivity; 2) to study the changes in aboveground biomass of different plant functional groups and their contribution to community productivity under different litter input and N addition treatments.
Methods We established a manipulative experiment with altered litter input and nitrogen addition treatments in a semiarid typical grassland in West Ujimqin Banner, Nei Mongol. A randomized block split-plot design was applied with five blocks. Three litter input treatments, including litter removal (C0), control (C1) and litter addition (C2), were assigned randomly in each block. Each plot (6 m × 7 m) of litter input treatment was separated into two subplots. One of the subplots was assigned as the N addition treatment (N1) and another subplot was considered as the control treatment without N addition (N0). In N addition treatment, 15 g N·m^-2·a^-1 N fertilizer (as NH₄NO₃) was applied every year since 2013. Aboveground net primary productivity (ANPP) in community and plant functional group levels of each treatment were determined during the peak season from 2013 to 2018.
Important findings Based on 6-year measurements, we found the following results. 1) Litter input increase and nitrogen addition increased community ANPP. Compared with the control, litter removal treatment significantly decreased ANPP by 8.4% and 7.6% in plots without and with N addition, respectively. Litter addition increased ANPP by 10.7% and 6.3% in plots without and with N addition, respectively. 2) Different responses of plant functional groups to altered litter input and N addition led to a change in plant functional group composition. The biomass of perennial bunch grass (PB) and perennial rhizome grass (PR) increased significantly with the increment of litter and nitrogen, which enhanced their dominant status in the community. 3) Improved soil water condition by litter input and nutrient supply by N addition are the major pathways that enhanced ANPP and changed the functional group composition. These results show that proper management, such as grazing exclusion and reducing grazing intensity, can promote productivity by increasing inputs of litter in semiarid grasslands, which leads to the maintenance of ecosystem stability. Suitable nutrients management, like nitrogen addition, is also helpful for productivity improvement and the recovery of degraded grasslands.

Aims Accurate estimation of the variation of nutrient cycling along environmental gradients within an ecosystem is important for assessing their ecological functions. The aim of this study is to explore the effects of different habitats on the metal element content and nutrient return dynamics of Casuarina equisetifolia.
Methods Taking the litter of C. equisetifolia in Chihu State-owned Protective Forest Farm of Huian, Fujian Province as the research object. Five distances named T₁, T₂, T₃, T₄ and T₅ respectively, were selected in order of near to far from the coastline, and the litter was collected to determine the metal element content.
Important findings We found that: 1) Different coastal distances had significant effects on the content and return of each element of C. equisetifolia litter. The element content and return from the forest edge zone to interior forest were linear. In order of near to far from the coastline, sodium (Na) content gradually decreases. Iron (Fe), copper (Cu), zinc (Zn) and manganese (Mn) increased since T₄, and their changing trend and amount of the return and content along the gradient were similar. 2) There were significant differences on the content of litter elements among different months. Litter Na, Fe, Cu, and Zn had similarities, and had lowest value in June and November. Litter Mn fluctuated after falling from February to April. The return amount was generally similar between litter Na and Cu, with peaks in May, August, and next January; Litter Mn, Fe, and Zn showed similar return amount, with peaks in May, August, and next January. 3) Na content in soils at different distances from the coastline decreased gradually, while other elements fluctuated and did not show significant difference along the gradient. 4) Litter Na and Fe were significantly positively correlated, and litter Na and Zn, Fe and Cu, and Fe and Zn were extremely significantly positively correlated, respectively. There was a positive correlation for the same element between soil and litter and the correlation was significant for Na and Cu. The difference in litter element was greatly affected by the difference in resorption rate during litter falling at different timing along the distance gradient. The temporal difference among different months was due to the requirements from plant life activity. The difference in the return of the element was related to the amount of litterfall and the content of elements in the litter.

Aims Due to the extremely low precipitation, low vegetation coverage, strong solar radiation, and poor soil stability, litter turnover in extremely arid areas differs from that in non-arid areas. This study aimed to determine the patterns of leaf litter decomposition of contrasting initial qualities in an extremely arid region.
Methods We used the litter bag method to investigate changes of the mass and water-soluble salt content in the leaf litter of three dominant species, Karelinia caspia, Alhagi sparsifoliaand Populus euphratica,in the desert- oasis transitional zone of the southern edge of the Taklimakan Desert, in responses to three levels of sand burial treatments, including placement of letter samples at the surface, and 2 cm and 15 cm soil depths, respectively, that represented different incubation environments under natural conditions.
Important findings The relationships of litter decomposition rate with the initial litter quality indicators, including carbon (C) content, nitrogen (N) content, C:N and lignin content, differed between the extremely arid sites and the non-arid sites. The litter placed on the surface had higher lignin content and faster mass loss than those subjected to other treatments. The losses of litter mass and changes in water-soluble salt content significantly varied with the level of burial treatments. Litter samples placed on the surface and at 2 cm depth had a significantly greater rate of losses in mass and water-soluble salt content than those at 15 cm depth. The surface litter had a greater amount of dissolved water-soluble salt in the early stage of decomposition. This study shows that the driving mechanism of litter decomposition in the extremely arid areas is unique. Under conditions of extremely low precipitation and the low activity of soil microorganisms, the buried depth is not the main factor driving the litter decomposition, whilst other abiotic processes such as solar radiation controlled the rate of decomposition.

Aims It is very important to investigate the relationships between litter decomposition characteristics and plant functional traits in understanding the maintenance mechanism of ecosystem functions.

Methods In order to study the main driving factors that affect the leaf litters and root decomposition of different species, this study took the leaf litters and roots of six main plant species Stipa grandis, Cleistogenes squarrosa, Anemarrhena asphodeloides, Leymus chinensis, Convolvulus ammannii and Carex korshinskyi in S. grandis steppe. The litter bag method was used to study the decomposition rate constant of both leaf litters and root through 501 days of field incubation. Plant functional traits including leaf dry matter content, root specific surface area, root tissue density, contents of C, N and different cellulose components of the leaf and root litters were determined and the relationships between decomposition characteristics and functional traits of leaf litters and root across six plant species were examined.

Important findingsThe results showed that there were significant interspecific differences in leaf and root traits of six plant species. The ratios of maximum to minimum values for most traits were between 1 and 2, while the difference in some traits, such as C:N and specific surface area of roots between species was nearly 4 times. For the six plant species, the overall trend of the mass residue and decomposition rate constant of the leaf litter and root during 501 days of decomposition all showed the rapid decomposition in the early stage, relatively slow decomposition in the middle stage and the slowest decomposition in the later stage. During the decomposition process of leaf litters and roots, Cleistogenes squarrosa showed the slowest one, while the leaf litter decomposition of Anemarrhena asphodeloides was the fastest, and the root decomposition of Convolvulus ammannii was the fastest. Through the correlation analysis and stepwise regression analysis, it was found that the decomposition process of leaf litters and roots was affected by different traits in different decomposition periods. The structural carbohydrate content was the main factor affecting the early and late decomposition of litters and the early decomposition of roots, while the non-structural carbohydrate content was the main factor affecting the middle and late decomposition of roots. In addition, the decomposition rate of leaf litters in the middle stage of decomposition was mainly affected by leaf dry matter content, while the decomposition rates of roots in the middle and late stages of decomposition were also significantly affected by C:N and N content, respectively. Our results present the important guide for the prediction of carbon and nutrient cycling process in the S. grandis steppe.

Aims Litterfall is an important component of ecosystem net primary productivity, and a key link between above- and below-ground carbon processes. However, it remains unclear how biodiversity, stand factors and functional traits work together in affecting litterfall production and its temporal stability during forest succession.

Methods We measured litterfall production for three years in plots from four successional stages of broad-leaf and Korean pine (Pinus koraiensis) mixed forests, at the northern limit of Korean pine forest in the Shengshan Reserve of Heilongjiang. Functional traits (leaf carbon and nitrogen contents, specific leaf area) were measured to quantify functional diversity and community weighted mean (CWM) of traits. Tree diameter and height, total basal area (TBA) and gap fraction were measured to quantify stand structure. We used hierarchy partitioning analysis and variance partitioning to evaluate the relative effects of stand factors, community level traits, and (species, functional and phylogenetic) diversity on annual litterfall production, and its temporal stability (= 1/coefficient of variation for annual litterfall production).

Important findings Litterfall production was significantly lower in the early successional stage, but did no vary from the middle to late successional stages. The litterfall stability increased continuously with forest succession. The variable importance of multivariate models also suggest that, the litterfall production was mainly affected by stand factors (e.g. height, TBA, gap fraction) and functional traits (leaf carbon content), with species richness also playing a role. For stability of litterfall production, however, functional diversity was the strongest predictor, followed by stand factors (such as maximum tree diameter). The independent effect of biodiversity on litterfall production was only 0.41%, but was as much higher (33.12%) for temporal stability of litterfall, suggesting that biodiversity have an important influence on litterfall stability that is independent of stand factors and traits. There was also a strong joint effect (up to 53.8%) among the stand factors, biodiversity and functional traits, indicating that these factors collectively affect litterfall production and its stability. Our results suggest that forest succession not only increases forest productivity but also improves ecosystem stability. Therefore, protecting primary forests and promoting forest restoration are effective ways to improve ecosystem functions.

Aims Forest litter are the main sources of soil humic substances, and different litter types can have differential effects on the formation and composition of soil humic substances. The aim of this study was to determine how variations in litter input would affect the dynamics of soil humic substances in subalpine forests of western Sichuan.
Methods A field in-situ litter manipulation experiment incorporating litter removal was established on sites of coniferous, broad-leaved, and mixed coniferous and broad-leaved forest stands. Measurements were made on the contents of soil extractable humic substances, humic acid, and fulvic acid; ratios of humic acid to fulvic acid and humic acid to humic substances were also computed.
Important findings The contents of extractable humic substances, humic acid and fulvic acid of soils varied significantly among forest types. The extractable humic substances content followed a descending order of coniferous forest > mixed coniferous and broad-leaved forest > broad-leaved forest, and the humic acid content of mixed coniferous and broad-leaved forest > coniferous forest > broad-leaved forest, and the fulvic acid content of coniferous forest > broad-leaved forest > mixed coniferous and broad-leaved forest. Fulvic acid was the predominant fraction of soil humic substances in all the three forest types. Time of measurements also significantly affected the contents of extractable humic substances, humic acid and fulvic acid, with an increasing trend for up to 1.5-year followed by decreases thereafter. With few exceptions, litter removal generally reduced the contents of extractable humic substances, humic acid and fulvic acid. The ratios of humic acid/fulvic acid and humic acid/extractable humic substances indicate low degree of humification for all the three forest types, which followed a descending order of mixed coniferous and broad-leaved forest > broad-leaved forest > coniferous forest. Litter removal improved the humic substances quality in the broad-leaved and mixed coniferous and broad-leaved forests to some extent. Correlation analysis showed significantly positive correlations of soil extractable humic substances with soil organic carbon, total nitrogen and soil water content, and a significantly negative correlation with temperature. In summary, short-term litter removal reduced the soil humic substances content, with differential effects by different litter types. We draw conclusion that the dynamics of soil humic substances are comprehensively regulated by litter type and environmental factors. Therefore, the impact of litter changes on soil humic substances needs further long-term research.

Aims The study of the pattern of biomass variations and their drivers along environmental gradients commonly contributes to the understanding of plant’s adaptability to environmental changes, further explains the spatial differences in vegetation and ecosystem processes. We investigated the biomass latitudinal patterns of plant communities and its components and revealed the quantitative relationships of biomass with climatic, soil and community structure as well as species diversity.

Methods In order to analyze the variation patterns of biomass along the latitude gradient and the drivers, we set up a total of 101 plots (4 m × 6 m) across nine region along latitude in the arid valley of southwest China (23.23°-32.26° N), to investigate biomass and species composition of plant communities and its components.

Important findings In the arid valley, the average biomass of community was (17.05 ± 1.09) t·hm^-2, of which the average biomass of shrub, herb and litter were (11.51 ± 1.03), (2.11 ± 0.21) and (3.41 ± 0.34) t·hm^-2, respectively, with each of them accounting for 60.2%, 15.6%, and 24.1% of the community biomass. With the increase of latitude, community biomass increased significantly. Shrub biomass and their proportion also increased significantly, herb biomass and their proportion remained consistent, whereas litter biomass decreased significantly. The changes of shrub dominance and abundance were the main internal factor for vegetation biomass variation along the latitude gradient. Additionally, compared with soil factors, climatic factors had a more significant impact on the biomass changes of communities and its components.

Aims The aim of this study was to explore the effects of native tree species on soil microbial biomass carbon (MBC) and nitrogen (MBN) content in subtropical Sichuan.

Methods In the present study, Cinnamomum japonicum, C. longepaniculatum, C. austrosiense, Alnus cremastogyne, C. camphora, Toona ciliata and T. sinensis in a common garden were selected as the research objects; whereas the abandoned land as the control. The effects of tree species on soil MBC content and MBN at different depths (0-10, 10-20, and 20-30 cm) were analyzed using the method of common garden.

Important findings (1) Tree species significantly affected the content of soil MBC and MBN, as well as their ratio. Compared with the abandoned land, tree species exhibited positive or neutral effects and the effects of tree species were particularly obvious in C. japonicum.For example, the contents of MBC and MBN in 0-10 cm soil layer were 108.2% and 139.6% higher than those in the abandoned land, respectively. (2) The content of soil MBC and MBN in the both tree and abandoned land generally decreased with an increase with soil depth; however, the characteristics of MBC:MBN varied with tree species. (3) The content of soil MBC and MBN varied with tree species and soil layer. The variations caused by tree species were stronger than that caused by soil layer. Compared with other species, C. japonicum was more conducive to the growth and reproduction of soil microorganisms.

Aims As key components in plant litters, the total phenols and condensed tannins greatly regulate decomposition process of forest litter, which can be directly or indirectly affected by forest gaps. The aim of this study was to determine how the forest gaps would affect the losses of total phenols and condensed tannins of foliar litter during decomposition in subalpine forest.
Methods We conducted a three-year in situ litter decomposition experiment on different forest gaps (i.e. gap center, canopy gap, expanded gap, closed canopy) in a subalpine forest of western Sichuan, and six foliar litters including Juniperus saltuaria, Abies fargesii var. faxoniana, Larix mastersiana, Betula albosinensis, Salix paraplesia and Rhododendron lapponicum were selected. The measurements were conducted to examine the losses of litter total phenols and condensed tannins during winter and growing season.
Important findings Litter total phenols and condensed tannins showed higher loss rates in the first decomposition year, with the levels of 10.76 mg·d^-1 and 8.5 mg·d^-1, respectively. The effects of forest gaps on the degradation of phenolic components gradually were getting weak with the litter decomposition proceeding, and exhibited obvious seasonal differences. The total phenols content of six litters all decreased rapidly in the growing seasons, while litters with higher initial condensed tannins with faster loss rate were found in the first winter, suggesting that both litter quality and seasons would significantly alter litter phenolic components losses during long-term decomposition under forest gaps. These results are helpful for deeper understanding of the litter decomposition process and nutrients cycling in forest ecosystems, which provide scientific data to improve the development of management policies in subalpine forests.

Aims As the first colonizer of leaf litters, the phyllospheric microbes may directly participate in the decomposition of litters.
Methods To test this hypothesis, the diversity of phyllospheric microbes and their effects in needle litter decomposition of Pinus massoniana were investigated by employing high-throughput amplicon sequencing techniques and indoor decomposition experiments.
Important findings (1) There are abundant and diverse microbial communities in the phyllospheric microbes of P. massoniana, and the microbial communities changed rapidly along with needle senescence. A large number of shared operational taxonomic units were detected among samples of mature needles, litter needles, and decomposing needles. (2) The decomposition process of P. massoniana needles can be divided into two stages: the rapid decomposition period (the first 8 months) and the slow decomposition period (after 8 months). Phyllospheric microbes of the senesced needles (fallen but not in contact with the soil) could decompose needle litters, and the decomposition rates exhibited the trend of phyllospheric microbes + soil microbes treatment > phyllospheric microbes treatment > soil microorganism treatment. There are synergistic effects between phyllospheric microbes and soil microbes during the decomposition of P. massoniana needles. (3) The decomposition rate of needle litters was significantly positively correlated with those of lignin and cellulose, while not correlated with the activity of lignin or cellulose decomposing enzymes. For ligninolytic enzymes, the activity of polyphenol oxidase had a significantly negative correlation with peroxidase activity. Meanwhile, activity of ligninolytic enzyme β-glucosidase had a significantly positive correlation with cellobiohydrolase activity. In conclusion, the present results indicate that the phyllospheric microbes can directly participate in the decomposition of needle litters, and its effect on the decomposition rate of needle litters of P. massoniana is superior to that of the soil microbes. These results have advanced the litter decomposition theory and provided theoretical foundation for further investigation into the core microbiome participating in litter decomposition.