Alpine marginal ecosystems above the natural tree line are considered to be the most vulnerable habitats for maintaining local biodiversity. The soil microbial community is crucial for ecosystem stability and function. However, our comprehension of the overall soil microbial community in alpine marginal ecosystems remains limited, particularly regarding environmental stress. We selected the Baima Mountain National Nature Reserve (BMNNR) in the northwest Yunnan provinces as our study area and collected soil samples from three different depth layers, in alpine marginal ecosystems. The phospholipid fatty acid (PLFA) analysis method was utilized to evaluate alterations in soil microbial communities. The results showed that: (1) the PLFA content gradually decreased with increasing soil depth; (2) on the whole, the variations in PLFA across alpine marginal ecosystems were obviously, the highest in alpine meadow (AM) and the lowest in alpine screes (AS); (3) the site effect exerted a greater direct influence than microhabitat effect and elevation (0–5 cm, 32 %, 16 % and 9 %, respectively; 20–40 cm, 46 %, 29 % and 0 %, respectively), with the direct impact of elevation decreasing as soil depth increased (0–5 cm, 5–20 cm and20-40 cm, 9 %, 1 % and 0 %, respectively); and (4) the ratio of cyclopropyl to precursors (Cy:Pre) in all communities was > 0.1, indicating that the soil microbial community was under environmental stress. This study demonstrates the potential of PLFA analysis to profile soil microbial communities and their stress status under field conditions and also provides a better understanding of the correlation between soil microbial communities and the function and health of alpine marginal ecosystems.

Payment for ecosystem services (PES) is an innovative economic intervention to mitigate the decline of ecosystem services and biodiversity; it plays a key role in harmonizing protection and development. Based on numerous PES practices worldwide, PES has emerged as a research hotspot in the field of sustainability. This paper presents a comprehensive scientometric analysis of PES academic publications between 1987 and 2022. The study aims to characterize the intellectual landscape of PES by identifying and visualizing the evolution of the collaboration network, the co-citation network, and emerging research trends. The findings reveal a rapid increase in publications of this field, indicating its growing importance as an interdisciplinary research subject. In particular, PES has gained significant attention from numerous researchers since 2007. Environmental sciences and ecology (50.77%) have been the core subjects, followed by business economics (11.04%) and biodiversity conservation (9.58%). Engineering (3.52%) and water resources (3.40%) have emerged as new fields in recent years. Notably, productive authors and institutions in this domain are primarily located in the United States, China, and the United Kingdom. However, fewer stable collaborations were found between China and European countries. Regarding the keywords, the most popular keywords of this topic were “ecosystem service” (1423), “conservation” (1324), and “biodiversity” (1029). By synthesizing the literature, this paper identifies pressing topics related to the effectiveness of PES, including the evaluation of effectiveness, efficiency assessment, and equity. Through an in-depth analysis, this paper elucidates global trends and directions in PES research. It is important to create a fair and efficient market that boosts the motivation and initiative of society to engage in PES initiatives, to increase investment in comprehensive PES projects, which helps improve the efficiency of fund utilization, especially concerning climate change mitigation. It is proposed to integrate natural sciences and social sciences to comprehensively assess the effectiveness of climate-friendly PES, which contributes to the sustainable development of PES research and application.

Numerous studies and some meta-analysis have proved that grazing exclusion affects the carbon storage of grassland ecosystems, but effects of grazing exclusion duration on carbon sequestration are still unclear, especially in the belowground carbon pool of global grasslands. Here, we used a comprehensive meta-analysis to examine the responses of 17 variables associated with carbon pool, carbon flux and environmental factors to grazing exclusion based on 215 peer-reviewed studies in grasslands on the earth. Results presented that: (1) grazing exclusion significantly increased carbon pools and carbon fluxes in grassland ecosystems, especially the belowground carbon pool; (2) Furthermore, grazing exclusion duration and climate affected ecosystem carbon sequestration to some degree. The ecosystem carbon exchange (NEE) changed from an increasing trend to a decreasing trend under grazing exclusion across increasing temperature and precipitation gradients, but the NEE continued to increase with grazing exclusion duration; (3) the temporal threshold for enhancing the belowground carbon pool was not reached, which may be caused by span over which data were collected (up to 40 years). The findings highlight that we should pay more attention to the effects of grazing exclusion duration and climate factors on grasslands in future study. Obviously, our study helps to better optimize policy decisions of grassland management but also for decision makers to cope with global climate change and achieve Sustainable Development Goals (SDGs).

Livelihoods around nature reserve (NRs), which are highly dependent on the harvest of endangered macrofungi (Cordyceps sinensis, Tricholoma matsutake), challenge biodiversity conservation on the Qinghai-Tibetan Plateau (QTP). Previous studies have attempted to capture the impact of rural livelihood assets through the conceptual framework of a sustainable livelihood and a multinomial logit model to find a possible solution. Although communities around NRs face more severe green traps, they are also regions with limited scientific evidence on this topic. We selected 7 NRs on the southeastern edge of the QTP as the study area, where NRs are densely distributed. Data were collected through a household survey and unstructured interviews with administrators, and we quantitatively analyzed the relationship between livelihood assets and livelihood strategies. K-mean cluster analysis related to income sources was used to identify three distinctive livelihood strategies: livestock, nonfarm, and gathering/livestock strategies. The results indicate that human, natural, and financial assets had significant influences on livelihood strategies and that the choice of livelihood strategy varied by livelihood assets. The multinomial logit model showed that enhancing financial and human assets facilitated the adoption of nonfarm strategies, while nature assets enhanced the propensity toward adopting the gathering/livestock strategy. Hence, this research recommends that policy interventions aimed at both endangered macrofungal conservation and livelihood development should give priority to improving the human assets of households living around NRs to achieve sustainable livelihood development.

A large number of individual studies and meta-analyses have shown that microplastics (MPs) affect soil ecosystems. However, the effects of different concentrations and types of MPs on soil ecosystem are still unclear. Here, a comprehensive meta-analysis was performed to examine the responses of 19 variables, associated with soil properties, microbes, enzymes, and fauna, to MPs, based on 114 peer-reviewed studies. The results showed that the addition of MPs significantly reduced the soil organic carbon (SOC), total nitrogen (TN), NH4+-N, pH, and diversity of bacteria, and increased the dissolved organic carbon (DOC), diversity of fungi and enzyme activities, especially enzymes related to the biogeochemical cycle. We further discussed that soil MPs exerted negative effects on soil fauna, including survival, growth, and reproduction, and that the concentration of MPs, rather than the type, was the biggest driving factor causing the toxicity of MPs affecting soil animals. More importantly, the concentrations of MPs were the main factor affecting the DOC, TN, NO3--N, total phosphorus (TP), available phosphorus (AP), and diversity of fungi, whereas the types of MPs were the main factors reflected in the SOC, NH4+-N, pH, diversity of bacteria, and enzyme activities. This study aimed to evaluate the response of soil ecosystems to the different concentrations and types of MPs, and the largest driving factor for the toxicity of MPs.

Long-term vegetation dynamics with satellite observations can provide valuable insights into natural variation in ecosystems and quantify disturbances associated with external pressures. Monitoring vegetation dynamics within protected areas (PAs) is essential, given their crucial role in protecting biodiversity and maintaining ecosystem integrity. In this study, using the normalized difference vegetation index (NDVI) and Breaks For Additive Seasonal and Trend (BFAST) model, we detected vegetation dynamics especially abrupt changes inside nature reserves (NRs, the primary type of PAs) on the Qinghai-Tibetan Plateau from 2000 to 2020. We then applied the matching approach and postmatching regression to evaluate the effect of NRs on natural vegetation with average NDVI, NDVI slope, and the number of abrupt changes. Our results showed that 78.97% of the vegetation within NRs exhibited greening trends. In addition, 29.15% of the area inside of the NRs experienced 1 or more abrupt changes, with the major change type interrupted greening (15.96%), followed by greening to browning (6.27%) and browning to greening (4.00%). The NRs significantly reduced the frequency of disturbances, and older NRs also showed a higher value of average NDVI compared to those in matched unprotected areas. Postregression models indicated that vegetation in newer NRs tended to be more vulnerable to disturbances and stricter NR management could benefit vegetation enhancement. Our analysis offers a new approach to vegetation dynamic monitoring that considers short-term disturbances. The findings of this work can help better understand effectiveness of PAs on ecosystem protection and offer practical guidance to future PAs management.

Soil microbes assemble in highly complex and diverse microbial communities, and microbial diversity patterns and their drivers have been studied extensively. However, diversity correlations and co-occurrence patterns between bacterial, fungal, and archaeal domains and between microbial functional groups in arid regions remain poorly understood. Here we assessed the relationships between the diversity and abundance of bacteria, fungi, and archaea and explored how environmental factors influence these relationships. We sampled soil along a 1500-km-long aridity gradient in temperate grasslands of Inner Mongolia (China) and sequenced the 16S rRNA gene of bacteria and archaea and the ITS2 gene of fungi. The diversity correlations and co-occurrence patterns between bacterial, fungal, and archaeal domains and between different microbial functional groups were evaluated using α-diversity and co-occurrence networks based on microbial abundance. Our results indicate insignificant correlations among the diversity patterns of bacterial, fungal, and archaeal domains using α-diversity but mostly positive correlations among diversity patterns of microbial functional groups based on α-diversity and co-occurrence networks along the aridity gradient. These results suggest that studying microbial diversity patterns from the perspective of functional groups and co-occurrence networks can provide additional insights on patterns that cannot be accessed using only overall microbial α-diversity. Increase in aridity weakens the diversity correlations between bacteria and fungi and between bacterial and archaeal functional groups, but strengthens the positive diversity correlations between bacterial functional groups and between fungal functional groups and the negative diversity correlations between bacterial and fungal functional groups. These variations of the diversity correlations are associated with the different responses of microbes to environmental factors, especially aridity. Our findings demonstrate the complex responses of microbial community structure to environmental conditions (especially aridity) and suggest that understanding diversity correlations and co-occurrence patterns between soil microbial groups is essential for predicting changes in microbial communities under future climate change in arid regions.

The Hengduan Mountain is one of the biodiversity hotpots in the world and the threatened and rare flora and fauna on the mountain have been protected in nature reserves (NRs) over the past 20 years. However, limited efforts have been made in studying the benefits local people have received from the conservation, particularly from alpine nature reserves. In this study, we address this research gap by focusing on local people's perceptions of ecosystem services (ESs). We assessed local people’s perception of a broad range of ESs benefits in NRs and consequently gained insights into how they valued 20 years of conservation. Binary analysis and multiple logistic regression model were applied to identify factors that affect the local people’s perception of ES benefits. Our results indicated that most people (73%) living nearby NRs recognized ES benefits from conservation, particularly cultural services like better view (68%) and more tourists (66%). Older people, educated, and other people who utilized NRs were likely to perceive the benefits of ESs from conservation. The opinions of respondents varied with village location, the level of NRs, and the knowledge of NRs. Our results reveal that formal education, age and knowledge-related NRs played important roles in shaping local people’s perceptions of cultural ESs benefits. It suggested that adaptive management should be implemented in NRs of the Hengduan Mountain and community-based protection and harvesting measures should be implemented to enhance community-participated co-management, coupled with environmental education programs covering all people in the family. The assessment of the benefit perception of local people provides a reference for seeking higher acceptance of conservation management.

Aim This study aims to propose a conservation network that contains suitable habitat and connectivity corridors for mitigation due to habitat transformation and fragmentation of Yunnan snub-nosed monkeys (Rhinopithecus bieti). Further, we also aim to understand the effects of land-use changes on the conservation network of R. bieti from 1990 to 2020. Location Three Parallel Rivers Region (TPRR) on the Qinghai-Tibetan Plateau (QTP) of China. Methods We used a GIS-based niche model to predict habitat suitability and extracted highly suitable habitats with an area above 30 km(2) as potential core habitats (PCH patches). We designed a normalized importance value index (NIVI) to select PCH patches with the top 5 NIVI values designated as priority protection habitats (PPHs), and we selected a circuit model to build connectivity corridors among PPHs and five protected areas (PAs) from 1990 to 2020. Results Unsuitable areas and lowly suitable habitats increased 69.3 and 46.8 km(2), respectively, from 1990 to 2020. In particular, the area of PPHs dramatically decreased from 212.1 km(2) in 1990 to 101.6 km(2) in 2020. Average length of connectivity corridors among PCH patches and PPHs decreased from 75.9 km in 1990 to 56.8 km in 2020. Main conclusion Habitat loss and fragmentation are common phenomena as evidenced by decreasing in highly and moderately suitable habitats of R. bieti and increasing in lowly suitable habitats and unsuitable areas. Five PAs are central to build a conservation network and to protect populations and wild groups of R. bieti. Land use changes the conservation network of R. bieti in the past 30 years. Based on re-planning boundaries of PAs to incorporate all protection network of R. bieti, it has practical significance to re-adjust the system of PAs that conservation network of R. bieti should be as fundamental management unit for PA development.

Southwest China, which is rich in biodiversity and a wide range of ecosystem services (ESs), is a strong support for local human wellbeing. This area is also one of the key components of the ecological security shelter (ESS) for national ecological security and biodiversity conservation. Due to the combination of man-made and natural factors, Southwest China has suffered serious ecological degradation that directly threatens ecological security which refers to the health status of ecosystems and ESs functions. Mapping ESs-based ecological security patterns (ESPs) is essential for designing conservation strategies that suitably combine regional environment conservation with sustainable utilization. We used the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs Tool) model to identify ecological conservation priority areas which integrated ecological sensitivity (soil erosion sensitivity, rock desertification sensitivity, landslide sensitivity, debris flow sensitivity, and freezing-thawing erosion sensitivity), ecological risk (drought risk, natural disaster risk, and socio-economic risk), and ecological conservation importance (soil conservation, water conservation, and biodiversity conservation importance). In this research, we summarized a new designing framework of ESs-based ESPs. We divided the study area into two zones and four belts including: (A) the alpine steppe and wetland zone, (B) Hengduan Mountain zone, (C) northern shelter belt (Daba-Micang Mountain), (D) central shelter belt (Wumeng-Wuling Mountain), (E) southern shelter belt (southern border of China), and (F) southwestern shelter belt (eastern Himalayas Mountain). Identifying distributions of the ESs-based ESPs has practical significance to improve local human wellbeing and to maintain sustainable development of natural-social ecosystems in Southwest China. Furthermore, ESs-based ESPs are necessary for local administrations to create rationalizing plans on balancing conservation and utilization of natural resources, so that policy-makers can put into place targeted prevention and control measures to limit the development of excessive consumption of natural resources and ecological damages, which is worth promoting.

Ignoring the responses of local households to ecological protection policies can not only seriously limit sustainable development of the alpine grassland ecosystem, but also not improve livelihood on the Qinghai-Tibetan Plateau (QTP). It is of vital importance to clearly understand coupling feedback and trigger between household decision-making of local herdsmen with the implementation of ecological protection policies. We selected Sanjiangyuan National Park (SNP) as the study area which was in the hinterland of the QTP and the first national park in China. We used the global rangeland (G-Range) model to simulate alpine grassland changes and DEcisions under Conditions of Uncertainty by Modeled Agents (DECUMA) model to identify household decision-making of local herdsmen. Results showed that: (1) distribution of livestock density was basically consistent with the distribution of habitat suitability of local households in the SNP; (2) more than half of the uneducated households (52 and 70%) opposed the eco-compensation and eco-migration policies; (3) most of the households (53.7%) never traded livestock for maintaining their livelihood; and (4) When local households owed 65,000 yuan (≈10,000 dollars) in debts, as the critical value (trigger), they traded livestock to support their livelihood. We suggest that feedback and trigger of household decision-making should be fully considered by managers of national park and policymakers of local governments in planning ecological protection policies to maintain sustainable development of alpine grassland, which is of practical significance to long-term conservation and sustainable utilization of natural resources in the SNP.

It is also necessary to enhance ecological security shelter in the Three Parallel Rivers Region (TPRR) with the Nu-Salween, Lancang-Mekong and Jinsha Rivers which is the key area of biodiversity hotspot on the Qinghai-Tibet Plateau. Mapping spatio-temporal patterns of forest disturbance and recovery is prerequisites for planning effective policies by policy-makers to maintain local sustainable development. Multi-source remote sensing data is useful for long-term spatial analysis of forest disturbance and recovery. We used LandTrendr algorithm on the Google Earth Engine platform (GEE), sample migration and random forest classification methods to classify forest types and to detect forest changes (disturbance and recovery) from 1990 to 2020 in the TPRR. Results showed that: (1) total area of forest disturbance was 2107.0 km2, accounting for 8.0% of the forest area in 1990. Since 2000, except in 2006 and 2010, the area of forest recovery was always higher than the area of forest disturbance; (2) proportion of forest disturbance in Honglaxueshan national nature reserve (HLXS NNR), Baimaxueshan national nature reserve (BMXS NNR), Laojunshan scenic spots (LJS SS), Yunlongtianchi national nature reserve (YLTC NNR), Yunling provincial nature reserve (YL PNR) and outside of protected areas (OPA) was 3.0%, 6.1%, 5.5%, 10%, 15.6% and 8.3%, respectively. Percentage of forest recovery was 6.2% in the whole study area, and 6.7% outside of protected areas. Proportion of forest recovery was 1.7%, 2.3%, 3.3%, 12.4% and 10.0% in HLXS NNR, BMXS NNR, LJS SS, YL PNR and YLTC NNR, respectively; (3) duration of forest disturbance was mainly concentrated in 1–3 years with a total area of 1632.9 km2, accounted for 77.5% of total area of forest disturbance. Duration of forest recovery was less volatile which was mainly concentrated in 2–13 years, with an area of 957.2 km2, accounted for 58.8% of total area of forest recovery; (4) recovery area of pine forest was the largest, with an area of 850.2 km2, accounted for 52.2% of the total forest recovery area in the study area. Based on mapping forest distribution and recovery, this research can support the decision-making of local governments on ecological conservation and is of benefit to ecological security improvement in the TPRR.

The microbial groups of nitrogen fixers, ammonia oxidizers, and denitrifiers play vital roles in driving the nitrogen cycle in grassland ecosystems. However, the understanding of the abundance and distribution of these functional microorganisms as well as their driving factors were limited mainly to topsoil. In this study, the abundances of nitrogen functional genes (NFGs) involved in nitrogen fixation (nifH), ammonia oxidation (amoA), and denitrification (nirK, nirS, and nosZ) were investigated in both topsoil (0-10 cm, soil layer with concentrated root) and subsoil (30-40 cm, soil layer with spare root) of three grassland habitats in northern China. The abundance of NFGs decreased with soil depth except for the archaeal amoA gene and the distribution of nifH, archaeal amoA, nirK, and nirS gene was significantly impacted by grassland habitats. Moreover, the distribution of NFGs was more responsive to the vertical difference than horizontal spatial heterogeneity. Redundancy analysis revealed that the distribution pattern of overall NFGs was regulated by grassland habitats, and these regulations were more obvious in the subsoil than in the topsoil. Variance partitioning analysis further indicated that soil resource supply (e.g., organic matter) may control the vertical distribution of NFGs. Taken together, the findings in this study could fundamentally improve our understanding of the distribution of N cycling-associated microorganisms across a vertical scale, which would be useful for predicting the soil N availability and guiding the soil N management in grassland ecosystems.

Alpine grassland is the main ecosystem on the Qinghai-Tibet Plateau (QTP). Degradation and restoration of alpine grassland are related to ecosystem function and production, livelihood, and wellbeing of local people. Although a large number of studies research degraded alpine grassland, there are debates about degradation patterns of alpine grassland in different areas and widely applicable ecological restoration schemes due to the huge area of the QTP. In this study, we used the meta-analysis method to synthesize 80 individual published studies which were conducted to examine aboveground and underground characteristics in non-degradation (ND), light degradation (LD), moderate degradation (MD), heavy degradation (HD), and extreme degradation (ED) of alpine grassland on the QTP. Results showed that aboveground biomass (AGB), belowground biomass (BGB), Shannon-Wiener index (H '), soil moisture (SM), soil organic carbon (SOC), soil total nitrogen (TN), and available nitrogen (AN) gradually decreased along the degradation gradient, whereas soil bulk density (BD) and soil pH gradually increased. In spite of a tendency to soil desertification, losses of other soil nutrients and reduction of enzymes, there was no linear relationship between the variations with degradation gradient. Moreover, the decreasing extent of TN was smaller in areas with higher precipitation and temperature, and the decreasing extent of AGB, SOC, and TN was larger in areas with a higher extent of corresponding variables in the stage of ND during alpine grassland degradation. These findings suggest that in areas with higher precipitation and temperature, reseeding and sward cleavage can be used for restoration on degraded alpine grassland. Fencing and fertilization can be used for alpine grassland restoration in areas with lower precipitation and temperature. Microbial enzymes should not be used to restore degraded alpine grassland on a large scale on the QTP without detailed investigation and analysis. Future studies should pay more attention to the effects of climate factors on degradation processes and specific ecological restoration strategies in different regions of the QTP.

Aim Although protected areas (PAs) are assumed to reduce natural threats within boundaries, their spillover effects remain equivocal. It is necessary to determine whether PAs truly achieve conservation targets and whether they promote or inhibit natural habitat degradation in adjacent areas by blockage or leakage spillover. This study aims to choose 54 nature reserves (NRs) focusing on forest protection as a case study to assess PA conservation effectiveness and spillover prevalence. Location PAs on the Qinghai-Tibet Plateau (QTP). Methods We used matching methods to compare deforestation rates inside PAs and their 20 km buffer zones with matched control areas based on the Global Forest Change dataset from 2001 to 2019. We contrasted the effects of NRs with different management levels, ages and areas. We designed five concentric buffer zones to assess spillover change with distance and estimated potential drivers of the spillover effect to explain its directions and magnitudes. Results 75.9% of the NRs were effective in preventing deforestation within their boundaries. NRs with different properties showed similar performance on forest conservation. Spillover effects were heterogeneous around NRs. One hundred and twenty-two buffer zones had positive spillover ranging from 0.1% to 5.3%. One hundred and nineteen buffer zones had leakages from -8.84% to -0.1%. Blockages slightly outnumbered leakages at different distances, while leakages happened more frequently when we treated buffer zones as a whole spillover area. The linear model indicated NR age and population density of buffer zones were the most relevant predictors to spillover value. Main conclusions Most PAs performed well in forest conservation. Leakages could undermine or offset PA conservation efforts and were related to multiple natural or socio-economic factors. We recommend considering the plurality of PAs as well as spillover effect and incorporating a social-ecological framework in further PA establishment and management.

Soil nitrogen (N) availability, which is primarily controlled by climate and soil properties, may play a key role in regulating biomass production in natural grasslands. However, how climate, soil properties, and gross N dynamics interact in their regulation of biomass production in natural grassland ecosystems in climate-sensitive biomes remains largely unclear. We quantified gross N transformation rates using the 15N dilution technique and the abundance of bacteria, fungi, ammonia-oxidizing archaea, and bacteria in the topsoil (0-10 cm) and subsoil (30-40 cm) in four natural grassland ecosystems along an altitudinal gradient from the Inner Mongolian (IM) to the Qinghai-Tibet (QT) plateaus. The results showed that gross N mineralization rates were generally greater in the topsoil (1.28-4.79 mg N kg-1 soil d-1) than in the subsoil (0.19-0.93 mg N kg-1 soil d-1) in all four grasslands. Gross nitrification rates were also consistently greater in the topsoil (2.42-6.48 mg N kg- 1 soil d-1) than in the subsoil (<1.43 mg N kg- 1 soil d-1) in all four grasslands. Gross nitrification rates were positively correlated with gross N mineralization rates, suggesting that soil nitrification was probably substrate limited. We present evidence of different interactive effects of climate, soil properties, and gross N dynamics on biomass production between the topsoil and the subsoil. In the topsoil, mean annual precipitation influenced gross N mineralization by altering total microbial activity and, in turn, influencing aboveground biomass. However, mean annual temperature influenced underground biomass through altering gross N mineralization in the subsoil. Climate influences biomass production by directly and indirectly regulating soil gross N mineralization in natural grasslands from the IM to the QT plateaus. The findings of the present study could facilitate better prediction of soil N availability for plants in natural grasslands under projected global climate change scenarios.

Ammonia (NH 3 ) volatilization from paddy soils is one of the main contributors to agricultural NH 3 emissions, however, little attention has been paid to the role of the ubiquitous periphyton in paddy soils on NH 3 volatilization. Considering that the composition of periphyton is dominated by autotrophs that directly affect the redox and pH conditions, it is hypothesized that the presence of periphyton may be an important factor affecting NH 3 emissions. In this study, NH 3 volatilization was determined under six periphyton biomass treatments and under treatments with six different N application rates to evaluate the contribution of periphyton to NH 3 volatilization in the laboratory representing the paddy soils system. Results showed that periphyton had trade‐off effects on NH 3 volatilization through pH and the NH 4 + concentration. Periphyton had net inhibition effects on NH 3 volatilization when the periphyton biomass was higher than 110 g·m −2 . In contrast, periphyton had net promotion effects on NH 3 volatilization when the periphyton biomass was less than 110 g·m −2 . The contribution of periphyton to NH 3 volatilization increased exponentially with increasing N application rates (i.e., with the increasing nitrogen concentration of the overlying water). In the low‐nitrogen treatments (≤20 kg N·ha −1 ), periphyton had no significant effect on NH 3 volatilization. In contrast, periphyton contributed as much as 47.4% of NH 3 volatilization at high nitrogen concentrations (100 kg N·ha −1 ). This study provides valuable insight into the role of periphyton on NH 3 volatilization, offers quantified relationship between periphyton and NH 3 volatilization, and improves the accuracy of NH 3 volatilization estimation in regional paddy soils.

Microbial stoichiometry and its potential driving factors play crucial roles in understanding the balance of chemical elements in ecological interactions and nutrient limitations along the aridity gradient. However, little is known about the variation in these features along the aridity gradient due to the lack of comprehensive field investigations. Additionally, previous studies focused on the topsoil (0–10 or 0–20 cm); however, the minimum sampling depth for topsoil could impact the results of the vertical distribution of microbial stoichiometry. In the present study, we measured the variation in microbial stoichiometry, examined the major influential factors (climatic, edaphic, and biotic factors) along an aridity gradient, and determined whether the sampling depth affected microbial C : N : P stoichiometry. From the topsoil to the subsoil, the microbial C : N, C : P, and N : P ratios varied from 6.59 to 6.83, from 60.2 to 60.5, and from 9.29 to 8.91, respectively. Only the microbial C : N ratio significantly increased with soil depth. The microbial C : N ratio significantly increased with increasing aridity in both topsoil and subsoil, while the microbial N : P ratio decreased along the aridity gradient only for the topsoil. This result implied that drought-stimulated microbes tend to be more N conservative, especially those in topsoil. Among all the factors, the soil organic carbon (SOC) content and the fungi-to-bacteria ratio exerted the largest influence on the microbial C : N, C : P, and N : P ratios at both soil depths, implying that the substrate supply and microbial structure together controlled the microbial stoichiometry. The results also revealed that the aridity index (AI) and plant aboveground biomass (AGB) exerted negative impacts on the microbial C : N ratio at both soil depths, and the effects of AI decreased in the subsoil. The results of this study suggested that the flexibility of the microbial N : P ratio should be considered when establishing the sampling depth for microbial stoichiometry study.

Abstract. Microbial stoichiometry and its driving factors play crucial roles in understanding the balance of chemical elements in ecological interactions and nutrient limitations along aridity gradients. However, little is known about the variation in these features along aridity gradients due to the lack of comprehensive field investigations. Additionally, previous studies focused on the surface soil (0–10 or 0–20 cm); however, the minimum sampling depth for surface soil could impact the results of the vertical distribution of microbial stoichiometry. In the present study, we measured the variation in microbial stoichiometry, examined the major influential factors (climatic, edaphic and biotic factors) along an aridity gradient and determined whether the sampling depth affected microbial C : N : P stoichiometry. We found that the microbial C : N (topsoil: 6.59; subsoil: 6.83), C : P (topsoil: 60.2; subsoil: 60.5) and N : P ratios (topsoil: 9.29; subsoil: 8.91) varied with soil depth and that the microbial C : N ratio significantly increased with soil depth. The microbial C : N ratio significantly increased with increasing aridity for both topsoil and subsoil, while the microbial N : P ratio decreased along the aridity gradient only for the topsoil), which implied that drought-stimulated microbes tend to be more N conservative, especially for the topsoil. Among all the factors, the soil organic carbon (SOC) content and fungi to bacteria ratio exerted the largest influence on the microbial C : N, C : P and N : P ratios at both soil depths, implying that the substrate supply and microbial structure together controlled the microbial stoichiometry. The results also revealed that the aridity index (AI) and plant aboveground biomass (AGB) influenced the C : N ratio in microbial biomass at both soil depths, and the effects of those factors decreased in the subsoil. The results of this study suggested that the flexibility of the microbial N : P ratio should be considered when establishing the minimum sampling depth in a vertical study. The present study also represented the first attempt to examine the patterns of soil microbial stoichiometry for different soil depth along an aridity gradient.