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Sulfur is an essential functional element in leaves, and it plays important roles in regulating plant growth, development and abiotic stress resistance in natural communities. However, there has been limited information on the spatial variation in leaf sulfur content (LSC) and adaptive characters on a large community scale. Sulfur in leaves of 2207 plant species from 80 widespread ecosystems (31 forests, 38 grasslands and 11 deserts) in China was measured. One-way analysis of variance with Duncan’s multiple-range tests were used to evaluate the differences in LSC among different plant growth forms and ecosystems. We fitted the relationships of LSC to spatial and climate factors using regression. Structural equation modeling analysis and phylogenetic analysis helped us further explore the main factors of LSC variation. LSC ranged from 0.15 to 48.64 g kg–1, with an average of 2.13 ± 0.04 g kg–1 at the community scale in China. We observed significant spatial variation in LSC among different ecosystems and taxa. Overall, LSC was higher in arid areas and herbs. Furthermore, higher LSC was observed under environments of drought, low temperatures and intense ultraviolet radiation. Temperature, precipitation, radiation, soil sulfur content and aridity jointly regulated LSC, explaining 79% of the spatial variation. However, LSC was not significantly related to phylogeny. Our results demonstrate that LSC plays an important role in plant adaptations to extreme environments and further extend our understanding of the biological function of sulfur from the organ to the community level. These findings highlight the importance of sulfur metabolism for our understanding of the impact of global climate change on plants.

Soil moisture is one important factor affecting ecosystem function, controlling the diffusion and transport of soil nutrients, maintaining soil microbial activities, and altering soil microbial diversity. To explore the response of soil microbial to soil moisture in the grassland ecosystem along the south shore of Hulun Lake in Inner Mongolia, China, we established a study area covering a natural soil moisture gradient which was subdivided into high (HW), medium (MW) and low water content (LW). Aboveground and belowground properties were measured by field investigation and laboratory analyses, respectively. Soil prokaryotic community composition was determined by high-throughput sequencing techniques. Soil moisture content as a dominant controlling factor, and soil organic nutrients as a secondary controlling factor, significantly affected the diversity of prokaryotic communities. The relative abundance and diversity of prokaryotic microbial were highest under MW, indicating a high heterogeneity of prokaryotes. However, the number of differential ASVs decreased, indicating that the structure and composition of the community stabilized under MW. Therefore, the prokaryotic community was more suitable to survive under MW. Although the relative abundance and diversity of microorganisms were lower under HW and LW than MW, phenotypic predictions showed that the prokaryotic community was more tolerant. We believe that either too high or too low soil water content will reduce the relative abundance and diversity of prokaryotic communities, and the communities will gradually become resistant to stress. Soil microbial community characteristics of the south shore of Hulun Lake in Inner Mongolia, China, respond significantly to soil moisture.

Grassland reconstruction is a major approach to alleviate the ‘black beach’ in Sanjiangyuan of the Qinghai-Tibetan Plateau. It is vital to understand how to manage the planting grassland after reconstruction. And which artificial grassland management pattern is more likely to restore the degraded grassland of ‘black beach?’ To provide the scientific basis for the restoration of ‘black beach’, we investigated the changes in vegetation characteristics, soil physicochemical properties and soil microbial community structure of planting grassland under different management patterns, and explored the effect of the management patterns on community succession of planting grassland. In this study, vegetation characteristics and soil physicochemical properties were measured by field investigation and laboratory analyses, respectively. Soil microbial community composition was determined by high-throughput sequencing techniques. The results showed that there were significant differences in vegetation characteristics, soil physicochemical properties and soil microbial community structure of the planting grassland under different management patterns. Actinobacteria and Basidiomycota were mainly controlled by vegetation plant species diversity, aboveground biomass (AGB) and soil organic carbon (SOC). Shannon-Wiener index, AGB and SOC peaked and the relative abundance of amplicon sequence variants annotated by Actinobacteria and Basidiomycota were significantly enriched under the management pattern of the planting once treatment. Additionally, the soil had the highest bacterial diversity and the lowest fungal diversity under the planting once treatment, becoming a ‘bacterial’ soil. These vegetation characteristics and soil environment were more conducive to overall positive community succession, indicating that the planting once treatment is the most reasonable management pattern for restoring the ‘black beach’.

Aims Grassland degradation represents a major challenge in the maintenance of grassland productivity. This process has dramatic impacts on energy flows and soil nutrient dynamics, thus directly or indirectly influencing soil microbes. Here, we aim to (i) examine changes in soil microbial composition, diversity and functionality in response to different levels of grassland degradation (i.e. non-degraded, moderately and severely degraded) in a temperate grassland in Inner Mongolia, and (ii) elucidate biotic and abiotic factors that are responsible for these changes. Methods The composition structure of soil microbial community was determined by high-throughput sequencing. The functionality of bacterial communities was examined using the tool of FAPROTAX, and functional guilds of fungal communities were quantified using the FUNGuild pipeline. Important Findings Grassland degradation significantly decreased soil bacterial diversity but it did not affect fungal diversity. Belowground biomass, soil organic carbon and total nitrogen were positively related to changes in diversity of bacterial community. Grassland degradation significantly increased the relative abundance of Chloroflexi (from 2.48% to 8.40%) and decreased Firmicutes (from 3.62% to 1.08%) of bacterial community. Degradation also significantly increased the relative abundance of Glomeromycota (from 0.17% to 1.53%) and decreased Basidiomycota (from 19.30% to 4.83%) of fungal community. The relative abundance of pathogenic fungi (Didymella and Fusarium) was decreased significantly by degradation. In addition, degradation had a significant impact on putative functionality of soil bacteria related to soil carbon and nitrogen cycling. Our results suggest that soil bacterial community is more sensitive than fungal community in response to degradation in the temperate grassland.

Functional traits are frequently used to evaluate plant adaptation across environments. Yet, traits tend to have multiple functions and interactions, which cannot be accounted for in traditional correlation analyses. Plant trait networks (PTNs) clarify complex relationships among traits, enable the calculation of metrics for the topology of trait coordination and the importance of given traits in PTNs, and how they shift across communities. Recent studies of PTNs provide new insights into some important topics, including trait dimensionality, trait spectra (including the leaf economic spectrum), stoichiometric principles, and the variation of phenotypic integration along gradients of resource availability. PTNs provide improved resolution of the multiple dimensions of plant adaptation across scales and responses to shifting resources, disturbance regimes, and global change.

The response of soil microorganisms to altered nitrogen (N) and rainfall patterns plays an important role in understanding ecosystem carbon and nitrogen cycling processes under global change. Previous studies have separately focused on the effects of N addition and rainfall on soil microbial diversity and community composition. However, the combined and interactive impact of N addition and rainfall on soil microbial diversity and function mediated by plant and soil processes have been poorly investigated for grassland ecosystems. Here, we conducted a field experiment with simulated N addition (N addition: 10 g N m

Assessing the health of the ecosystem based on the landscape pattern of national parks can facilitate policy makers in formulating more targeted conservation policies to better manage national park ecosystems. To analyze the landscape patterns and characteristics of the national park, the ecosystem health evaluation index system of the national park was constructed using the vigor-organization-resilience (VOR) model to evaluate the health status. In this study, the Shennongjia National Park in China was selected as a case study area to be assessed using the index system. The results revealed that the patches of construction land and farmland are the largest in number and the most complex in shape, reflecting the obvious fragmentation of construction land and farmland patches. All patch types in this national park were evenly distributed. The results of the analysis showed that the comprehensive index of national park heath, according to the VOR model, is 0.74, indicating that the ecosystems in this study area were in a good state of health. Ecosystems in strictly protected areas of this park had the highest ecosystem health index levels, while the traditional utilization areas had the lowest. Ecosystem health levels were characterized by significant spatial agglomeration characteristics, with high-high aggregation distribution areas, mainly clustered in strictly protected areas, and low-low aggregation distribution, mainly clustered in traditional utilization areas and marginal areas. This study provided a set of ecosystem health assessment systems and their practical use in China’s newly established national parks.

Carbon (C) and nitrogen (N) are the primary elements involved in the growth and development of plants. The C:N ratio is an indicator of nitrogen use efficiency (NUE) and an input parameter for some ecological and ecosystem models. However, knowledge remains limited about the convergent or divergent variation in the C:N ratios among different plant organs (e.g., leaf, branch, trunk, and root) and how evolution and environment affect the coefficient shifts. Using systematic measurements of the leaf-branch-trunk-root of 2,139 species from tropical to cold-temperate forests, we comprehensively evaluated variation in C:N ratio in different organs in different taxa and forest types. The ratios showed convergence in the direction of change but divergence in the rate of change. Plants evolved toward lower C:N ratios in the leaf and branch, with N playing a more important role than C. The C:N ratio of plant organs (except for the leaf) was constrained by phylogeny, but not strongly. Both the change of C:N during evolution and its spatial variation (lower C:N ratio at midlatitudes) help develop the adaptive growth hypothesis. That is, plants with a higher C:N ratio promote NUE under strong N-limited conditions to ensure survival priority, whereas plants with a lower C:N ratio under less N-limited environments benefit growth priority. In nature, larger proportion of species with a high C:N ratio enabled communities to inhabit more N-limited conditions. Our results provide new insights on the evolution and drivers of C:N ratio among different plant organs, as well as provide a quantitative basis to optimize land surface process models.

The R2R3-MYB transcription factor FOUR LIPS (FLP) controls the stomatal terminal division through transcriptional repression of the cell cycle genes CYCLIN-DEPENDENT KINASE (CDK) B1s (CDKB1s), CDKA; 1, and CYCLIN A2s (CYCA2s). We mutagenized the weak mutant allele flp-1 seeds with ethylmethane sulfonate and screened out a flp-1 suppressor 1 (fsp1) that suppressed the flp-1 stomatal cluster phenotype. FSP1 encodes RPA2a subunit of Replication Protein A (RPA) complexes that play important roles in DNA replication, recombination, and repair. Here, we show that FSP1/RPA2a functions together with CDKB1s and CYCA2s in restricting stomatal precursor proliferation, ensuring the stomatal terminal division and maintaining a normal guard-cell size and DNA content. Furthermore, we provide direct evidence for the existence of an evolutionarily conserved, but plant-specific, CDK-mediated RPA regulatory pathway. Serine-11 and Serine-21 at the N terminus of RPA2a are CDK phosphorylation target residues. The expression of the phosphorylation-mimic variant RPA2a(S11,21/D) partially complemented the defective cell division and DNA damage hypersensitivity in cdkb1;1 1;2 mutants. Thus, our study provides a mechanistic understanding of the CDK-mediated phosphorylation of RPA in the precise control of cell cycle and DNA repair in plants.

Root turnover is a key process of terrestrial ecosystem carbon cycle, which is of great significance to the study of soil carbon pool changes and global climate change. However, because there are many measurement and calculation methods of root turnover, the results obtained by different methods are quite different, and the current research on root turnover of forest ecosystem on the global regional scale is not sufficient, so the change law of root turnover of global forest ecosystem is still unclear. By collecting literature data and unifying the calculation method of turnover rate, this study integrates the spatial pattern of fine root turnover of five forest types in the world, and obtains the factors affecting fine root turnover of forest ecosystem in combination with soil physical and chemical properties and climate data. The results showed that there were significant differences in fine root turnover rate among different forest types, and it gradually decreased with the increase of latitude; the turnover rate of fine roots in forest ecosystem is positively correlated with annual average temperature and annual average precipitation; fine root turnover rate of forest ecosystem is positively correlated with soil organic carbon content, but negatively correlated with soil pH value. This study provides a scientific basis for revealing the law and mechanism of fine root turnover in forest ecosystem.

Sulfur (S) is a functional element that plays an important role in abiotic stress resistance and environmental adaptation in plants. However, knowledge of the biogeographic patterns of S among major plant organs remains limited. We conducted a methodologically consistent field survey of 2745 plant species across 78 typical communities throughout China. From this, we constructed a new matched database of S content in leaves, twigs, trunks, and roots to explore S allocation strategies in plants to better understand the regulatory mechanisms on a large scale. The average S content in leaves, twigs, trunks, and roots of plants in China was 2.32 ± 0.04, 1.13 ± 0.02, 0.15 ± 0.01, and 1.23 ± 0.02 g kg

As a significant environmental issue, global warming will have a significant impact on soil microorganisms, especially soil bacteria. However, the effects of warming on the network structure of bacterial communities and the function of ecosystems remain unclear. Therefore, we examined the effects of three-year simulated field warming on the complexity of soil bacterial communities and predicted functions in a temperate steppe of Inner Mongolia. Warming significantly increased the α-diversity of bacteria in 2018 but did not affect it in 2019 and 2020. Warming increased network complexity and stability and keystone taxa, and these bacterial taxa also associated more closely with each other, indicating that the protection of interactions between bacterial taxa is very important for the conservation of biodiversity. Warming significantly increased aerobic chemoheterotrophy, ureolysis, and chemoheterotrophy, suggesting that warming increased the ability of bacteria to decompose organic matter and the emission of greenhouse gases, such as CO2 and CH4. Collectively, warming will alter soil bacterial community structure and its potential functions, further affecting key functions in grassland belowground ecosystems.

A better understanding of how rates and stoichiometric signatures of root exudates respond to altered N deposition and rainfall patterns is critical for predicting future impacts of environmental changes on ecosystem function and services. Here, we conducted a field experiment examining the effects of rainfall reduction (−50% compared to the control with normal rainfall), rainfall addition (+50%), N addition (~10 g N m−2 yr−1), and their interactions on root C and N exudation rates and C : N ratios of root exudates from dominant species in a temperate steppe. We hypothesized that increasing soil water and N availability will increase C: N ratios of root exudates because plants will grow more and retain more N in their biomass, thus have lower root N exudation rates. We found greater changes in root N exudation rates (ranging from −18% ~ +11%) than C exudation rates (ranging from −6 ~ +11%) in response to rainfall and N treatments. In addition, N addition and its interactions with rainfall treatments decreased root N exudation rates by 4–18% and therefore increased C : N ratios of root exudates by 8–27% compared to control; however, a contrasting pattern was found under rainfall reduction. Furthermore, changes in root C exudation rates in response to rainfall and N treatments were not related to changes in plant biomass. In contrast, root N exudation rates decreased with increasing plant biomass, resulting in an overall increase in C : N ratios of root exudates with increasing plant biomass. Overall, our results reveal the C : N stoichiometric plasticity of root exudates in response to resource modifications. These findings have important implications for understanding rhizosphere plant-soil-microbe interactions and ecosystem functioning under environmental changes.

The energy stored in biomass, a key component of global sustainable energy, is essential for achieving the United Nations Sustainable Development Goals, especially for climate change mitigation and energy security. However, it remains unknown how much energy is stored in the vegetation biomass of China's terrestrial ecosystems. Furthermore, the shortage of biomass has limited the development of China's bioeconomy and bioenergy industry, requiring us to seek more multi-source and sustainable biomass supplies. In view of this, through comprehensive investigations and systematic data integration (including biomass data, calorific value data, land cover data, climate data, etc.), we explored the gross biomass energy (BE) reserves and their spatiotemporal pattern based on a total of 14 vegetation types that account for 76.24% of China's land area. The theoretical potential of gross BE in China was estimated as 535.91 EJ in 2010, which was equivalent to 18.29 Gt standard coal. BE showed a trend of continuous increase from 1980 to 2060 and is expected to peak in 2030. Importantly, BE (per land area or per capita) was significantly negatively correlated with provincial development levels in China. Our findings indicate that China has abundant BE reserves, which have potential as feedstocks for the production of different forms of energy in the context of sustainable development. Furthermore, more advanced low-cost technologies, such as coal and biomass co-gasification, are expected to promote the transformation and upgradation of energy systems in China in the future.

The contribution of root exudates to soil carbon (C) inputs is poorly quantified, especially for grasslands under the context of degradation that includes simultaneous shifts in species composition due to long-term overgrazing. The objectives of this study were to examine (1) how grassland degradation affects root exudation rate and (2) to what extent root exudates contribute to soil C inputs compared to litter materials and root turnover during degradation. A field experiment was conducted in a temperate grassland, with different levels of degradation (undegraded control, moderately degraded, and severely degraded), dominated by different species in Inner Mongolia. Aboveground biomass, root biomass, and root exudate rate were measured monthly during a growing season. Root exudation rates differed among dominant plant species across the degradation gradients and grassland degradation significantly increased root exudation rates at the plot level. However, the amount of root exudates released to soils in degraded sites was lower than in undegraded site due to reduced living root biomass. Compared to the undegraded control, the relative contribution of root exudates to soil C inputs was enhanced by grassland degradation as a result of decreased contributions from root turnover. These findings prove grassland degradation can alter the relative contribution of root exudates compared to other soil C inputs and highlight the necessity of further studies to examine how this shift may affect soil organic C formation and long-term storage.

Global climate change has generally modified net primary production (NPP) which leads to increasing litter inputs in some ecosystems. Therefore, assessing the impacts of increasing litter inputs on soil nutrients, plant growth and ecological carbon (C) : nitrogen (N) : phosphorus (P) stoichiometry is critical for an understanding of C, N and P cycling and their feedback processes to climate change. In this study, we added plant above-ground litter, harvested near the experimental plots, to the 10–20 cm subsoil layer of a steppe community at rates equivalent to annual litter input of 0, 15, 30, 60 and 120%, respectively, covering the entire range of the expected NPP increases in this region due to climate change (10–60%). We measured the resulting C, N and P content of different pools (above- and below-ground plant biomass, litter, microbial biomass). Small litter additions, which are more plausible compared to the expected increase predicted by Earth system models, had no effect on the variables examined. Nevertheless, high litter addition (120% of the annual litter inputs) significantly increased soil inorganic N and available P, above-ground biomass, below-ground biomass and litter. Our results suggest that while very high litter addition can strongly affect C : N : P stoichiometry, the grassland studied here is resilient to more plausible inputs in terms of stoichiometric functioning.

The factors controlling litter decomposition and soil microbial community are important regulators of biogeochemical processes. Here we aim to explore controls on litter decomposition dynamics and soil microbial community composition in temperate forest by comparing three Korean pine forests along an altitudinal gradient. : Single- and mixed-species litter decomposition rates were determined by the litterbag method and soil microbial community composition was characterized by PLFAs. : Litter decomposition rates decreased with altitude regardless of litter type, and were controlled by temperature. Generally, fine root litter decomposed more rapidly than leaf litter, and mixed-species litter decomposed faster than single-species. Soil microbial biomass C and N decreased with altitude and varied differently among forest types in response to soil temperature and nutrient status. Fungal: bacterial PLFA ratios were significantly larger in forests receiving relatively poor litter quality inputs. Soil temperature, soil water content, total soil N and P were all directly related to the changes in total PLFAs among three forests. : In these Korean pines dominated temperate forests, environmental changes associated with altitude gradient drive decomposition dynamics and soil microbial community composition. This implies that climate change might be an important factor affecting these systems in the future.

Artemisia ordosica Krasch. is a semishrub native to the Ordos Plateau of Inner Mongolia, northern China, and forms a unique and dominant vegetation type in the sandland of the region. To determine the variation of productivity in A. ordosica rangeland, we investigated net primary production (NPP), fine root turnover, soil microbial C (Cmic), and soil organic carbon density (SOCd) on sand dunes differing in mobility (i.e., fixed, semifixed, and shifting sand dunes) in Mu Us sandland. We found that, on an area basis, the NPP, SOCd ,C mic, and fine root turnover rates all increased with increasing vegetation cover. However, the ratios of root NPP to total NPP (RMRN) increased with declining vegetation cover. Total NPP varied markedly among habitats and ranged from 18.3 g ? m 22 ? yr 21 for communities on the shifting sand dunes to 293.8 g ? m 22 ? yr 21 for communities on the fixed sand dunes; whereas the rates of fine root turnover varied from 0.16 ? yr 21 to 0.54 ? yr 21 . Our study demonstrated that habitat change in sandland has significant impacts on ecosystem productivity by affecting many related aspects of NPP. From the perspective of biomass production, protection of the semifixed dunes from degradation should be taken as a higher priority than trying to convert shifting sand dunes to semifixed sand dunes; whereas conversion of semifixed sand dunes to fixed sand dunes would appear to be a much easier task than restoring shifting sand dunes.

Fine root dynamics and turnover rate were studied by sequential soil coring method in a 60-year-old Asia white birch ( Betula platyphylla ) forest of Donglingshan Mountain, China. Biomass and necromass of both the finest ( −1 , respectively.

A natural grassland in northeastern China dominated by Leymus chinensis (Trin.) was subject to drought treatments to determine the seasonal dynamics in resource partitioning to shoot and storage organs in response to drought. The growing season was divided into six stages according to the phenology of L. chinensis. Plant samples of L. chinensis were collected at each stage to determine biomass, gross calorific value, relative water content, and key mineral contents of plant parts, including rhizomes, roots, leaves, and stems. Resource partitioning to shoot and storage organs as measured by biomass, gross calorific value, and N, K+, and Na+ contents varied significantly among phenologic stages. Drought treatment (natural precipitation, 50–60 % of field capacity) significantly reduced biomass, gross calorific value, relative water content of shoot, and N and K+ contents in both shoot and storage organs, but it enhanced rhizome : shoot ratio and Na+ content. A negative correlation in biomass, gross calorific value, and K+ and Na+ contents between shoot and storage organs was found throughout the growing season, which may have been accentuated by drought when soil moisture was limited. Our results indicate that resource partitioning to storage plays an important role in regulating plant growth of L. chinensis, especially under drought conditions.

We developed and compared allometric equations describing leaf, branch, and fruit biomass at the branch level, and leaf, branch, fruit and coarse root biomass at the whole plant level for Artemisia ordosica plants growing on fixed, semi-fixed and shifting dunes of the Mu Us desert. At the branch level, branch diameter significantly correlated with leaf, branch and fruit biomass. The allometric relationships predicting leaf, branch and fruit biomass significantly differed among the different dune types. At the whole plant level, crown area significantly correlated with leaf, branch, fruit and coarse root biomass. The allometric relationships predicting leaf and fruit biomass significantly differed among the different dune types. Stand total biomass was 339.9, 178.8 and 25.0 g m−2 in fixed, semi-fixed and shifting dunes, respectively. Stand biomass of leaves, branches, fruits, coarse roots, and fine roots (1–2 mm and

Morphology, biomass accumulation and allocation, gas exchange, and chlorophyll fluorescence were compared for one-year-old seedlings of Salix psammophila and Artemisia ordosica, two dominant desert species, in response to two water supplies (equivalent to 315.0 mm for present precipitation in growing season and to 157.5 mm for future decreasing precipitation) during 105 d. For both species, photochemical efficiency of photosystem 2 (Fv/Fm), net photosynthetic rate, transpiration rate, stomatal conductance, biomass accumulation in different organs, tree height, number of leaves, and leaf area were reduced in response to the decrease in water supply. For both species, instantaneous water use efficiency was not affected by the water deficit. However, diurnal patterns of gas exchange and biomass allocation were affected in different ways for the two species, with notably a decrease in specific leaf area and an increase in root : shoot ratio for S. psammophila only. Overall, S. psammophila was more responsive to the decreasing precipitation than A. ordosica.

We studied the responses of leaf water potential (Ψw), morphology, biomass accumulation and allocation, and canopy productivity index (CPI) to the combined effects of elevated CO2 and drought stress in Caragana intermedia seedlings. Seedlings were grown at two CO2 concentrations (350 and 700 μmol mol−1) interacted with three water regimes (60–70%, 45–55%, and 30–40% of field capacity of soil). Elevated CO2 significantly increased Ψw, decreased specific leaf area (SLA) and leaf area ratio (LAR) of drought-stressed seedlings, and increased tree height, basal diameter, shoot biomass, root biomass as well as total biomass under the all the three water regimes. Growth responses to elevated CO2 were greater in well-watered seedlings than in drought-stressed seedlings. CPI was significantly increased by elevated CO2, and the increase in CPI became stronger as the level of drought stress increased. There were significant interactions between elevated CO2 and drought stress on leaf water potential, basal diameter, leaf area, and biomass accumulation. Our results suggest that elevated CO2 may enhance drought avoidance and improved water relations, thus weakening the effect of drought stress on growth of C. intermedia seedings.

We compared the effect of elevated temperature on morphological development, biomass accumulation and allocation, and gas exchange of three dominant plants (Caragana intermedia Kuanget H.C. Fu, Hedysarum mongolicum Turcz., and Artemisia ordosica Krasch.) growing in Chinese Maowusu sandland. Plants were grown in two temperature chambers (25/20, 28/23 °C, day/night) during 60 d. Tree height, number of leaves, and leaf area were increased in C. intermedia and H. mongolicum seedlings, while in A. ordosica temperature only affected tree height. Elevated temperature increased biomass and reduced the root : shoot ratio in C. intermedia and H. mongolicum seedlings, but not in A. ordosica seedlings. The net photosynthetic rate (PN) and transpiration rate (E) were increased at days 40 and 60 in C. intermedia and H. mongolicum seedlings, while in A. ordosica seedlings no significant effects on E were observed, and PN was increased only at day 60. Water use efficiency (WUE) was reduced at days 40 and 60 in H. mongolicum seedlings, and at day 60 in C. intermedia seedlings. No temperature effect on WUE was observed in A. ordosica seedlings. These different responses indicate that climate change could alter plant communities in Maowusu sandland.

Research Funding: 'Strategic Priority Research Program - Climate Change: Carbon Budget and Related Issues' of the Chinese Academy of Sciences. Grant Number: XDA05050407. The National Natural Science Foundation of China. Grant Number: 31370462. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, the Chinese Academy of Sciences. The Flemish National Science Foundation. The European Community's Seventh Framework Programme (FP7/2007-2013). Grant Number: 226701 (CARBO-Extreme). The European Research Council Synergy. Grant Number: 610028. The Cost Action Terrabites. Grant Number: ES-0805. Fresh plant litter inputs accelerate soil organic matter (SOM) decomposition through a ubiquitous mechanism called priming. Insufficient priming has been suggested as a stabilization mechanism of SOM at depth, as well as the long-term persistence of some highly degradable organic compounds in soils. Priming therefore plays a crucial, albeit unquantified and commonly neglected, role in the global carbon cycle. Because priming intensity is likely to be altered by global changeinduced changes in net primary productivity, it casts substantial uncertainty to future projections of the climate-carbon cycle feedback. Using results from a large field litter manipulation experiment in Mongolian steppe, we here show that priming intensifies with increasing litter inputs, but at a decreasing efficiency: the stimulation per unit litter added declines with increasing litter inputs. This non-linear behavior originates from two antagonistic responses to fresh litter inputs: a stimulation of microbial activity versus a shift in microbial community composition (more fungi) associated to substrate shift from SOM to litter. Despite all complexity, however, the priming effect on SOM decomposition scaled linearly with the response of microbial biomass across the entire range of plant litter addition (60-480 g C m⁻²), suggesting that priming could be modeled effectively as a function of the response of microbial biomass to litter inputs. Incorporating the priming mechanism in Earth System models will improve their estimates of the SOM-climate feedback and appears to be best addressed by explicitly representing microbial biomass in the models.

Fine root and aboveground litterfall, two large fluxes of nutrients and carbon in the forest ecosystems, are key processes to be considered in efforts of measuring, modeling and predicting soil carbon sequestration. We used sequential coring and litter trap to measure seasonal dynamics of fine root and litterfall in three Korean pine dominated forests along an altitudinal gradient in the Changbai Mountain during the 2012 growing season. Fine root biomass decreased significantly while necromass increased remarkably with altitude. Patterns and amounts of fine root production and mortality varied among forest types. Litterfall decreased significantly with altitude, whereas forest floor mass increased. Carbon inputs through fine root mortality and litterfall decreased significantly with altitude while carbon storage of fine root mass did not differ among forest types and carbon storage of forest floor mass was significantly larger in higher altitudinal forests due to lower turnover rates. This study provided an insight into the variations of fine root and litterfall dynamics among three Korean pine forests which were associated with different vegetation traits and environmental conditions, and also the quantification of carbon fluxes through fine root mortality and litterfall for estimating carbon budget of temperate forest.

Background Many theoretical researches predicted that the larch species would decrease drastically in China under future climatic changes. However, responses of the structural and compositional changes of Gmelin larch (Larix gmelinii var. gmelinii) forests to climatic changes have rarely been reported. Methodology/Principal Findings Field survey was conducted to examine the structures and compositions of natural Gmelin larch forests along a climatic gradient. Stepwise linear regression analyses incorporating linear and quadratic components of climatic and non-climatic factors were performed on the structural and compositional attributes of those natural Gmelin larch forests. Isothermality, Max Temperature of Warmest Month (TempWarmestMonth), Precipitation of Wettest Month (PrecipWettestMonth), Precipitation Seasonality (PrecipSeasonality) and Precipitation of Driest Quarter (PrecipDriestQuarter) were observed to be effective climatic factors in controlling structure and composition of Gmelin larch forests. Isothermality significantly affected total basal area of larch, while TempWarmestMonth, PrecipWettestMonth and PrecipSeasonality significantly affected total basal area of Mongolian pine, and PrecipDriestQuarter significantly affected mean DBH of larch, stand density of larch and total basal area of spruce and fir. Conclusions/Significance The summer and winter temperatures and precipitations are all predicted to increase in future in Northeast China. Our results showed the increase of total basal area of spruce and fir, the suppression of regeneration and the decrease of stand density of larch under increased winter precipitation, and the decrease of total basal area of larch under increased summer temperature in the region of current Gmelin larch forest. Therefore, we suggest that larch would decrease and spruce and fir would increase in the region of future Gmelin larch forest.

Background: Global climatic change is generally expected to stimulate net primary production, and consequently increase soil carbon (C) input. The enhanced C input together with potentially increased precipitation may affect soil microbial processes and plant growth. Methodology/Principal Findings: To examine the effects of C and water additions on soil microbial properties and plant growth, we conducted an experiment lasting two years in a temperate steppe of northeastern China. We found that soil C and water additions significantly affected microbial properties and stimulated plant growth. Carbon addition significantly increased soil microbial biomass and activity but had a limited effect on microbial community structure. Water addition significantly increased soil microbial activity in the first year but the response to water decreased in the second year. The water-induced changes of microbial activity could be ascribed to decreased soil nitrogen (N) availability and to the shift in soil microbial community structure. However, no water effect on soil microbial activity was visible under C addition during the two years, likely because C addition alleviated nutrient limitation of soil microbes. In addition, C and water additions interacted to affect plant functional group composition. Water addition significantly increased the ratio of grass to forb biomass in C addition plots but showed only minor effects under ambient C levels. Our results suggest that soil microbial activity and plant growth are limited by nutrient (C and N) and water availability, and highlight the importance of nutrient availability in modulating the responses of soil microbes and plants to potentially increased precipitation in the temperate steppe. Conclusions/Significance: Increased soil C input and precipitation would show significant effects on soil microbial properties and plant growth in the temperate steppe. These findings will improve our understanding of the responses of soil microbes and plants to the indirect and direct climate change effects.

Summary • Global climate change is generally expected to increase net primary production, resulting in increased soil carbon (C) inputs. To gain an understanding of how such increased soil C inputs would affect C cycling in the vast grasslands of northern China, we conducted a field experiment in which the responses of plant and microbial biomass and respiration were studied. • Our experiment included the below-ground addition of particulate organic matter (POM) at rates equivalent to 0, 60, 120 and 240 g C m−2, under either natural precipitation or under enhanced precipitation during the summer period (as predicted for that region in recent simulations using general circulation models). • We observed that addition of POM had a large effect on soil microbial biomass and activity and that a major part of the added C was rapidly lost from the system. This suggests that microbial activity in the vast temperate grassland ecosystems of northern China is energy-limited. Moreover, POM addition (and the associated nutrient release) affected plant growth much more than the additional water input. • Although we performed no direct fertilization experiments, the response of plant productivity to POM addition (and associated release of nutrients) leads us to believe that plant productivity in the semiarid grassland ecosystems of northern China is primarily limited by nutrients and not by water.