Alpine Meadow Research Articles

Barley farmland harbors a highly homogeneous soil bacterial community compared to wild ecosystems in the Qinghai-Xizang Plateau.

Understanding patterns and processes of microbial biogeography in soils is important for monitoring ecological responses to human activities, particularly in ecologically vulnerable areas such as the Qinghai-Xizang Plateau. Highland barley is the staple food of local people and has mainly been cultivated along the Yarlung Zangbo River valley in Xizang. Here we investigated soil bacterial communities from 33 sampling sites of highland barley farmland in this region and compared them to those from wild ecosystems including alpine tundra, meadow, forest, and swamp. Additionally, the effects of environmental factors on bacterial communities, as well as the relative importance of stochastic and deterministic processes in shaping the beta diversity of soil bacterial communities in alpine ecosystems were assessed. In contrast to soils of wild ecosystems, these farmland samples harbored a highly homogeneous bacterial community without significant correlations with geographic, elevation, and edaphic distances. Discriminant bacterial taxa identified for farmland samples belong to Acidobacteria, with Acidobacteria Gp4 as the dominant clade. Although Acidobacteria were the most abundant members in all ecosystems, characterized bacterial taxa of meadow and forest were members of other phyla such as Proteobacteria and Verrucomicrobia. pH and organic matter were major edaphic attributes shaping these observed patterns across ecosystems. Null model analyses revealed that the deterministic assembly was dominant in bacterial communities in highland barley farmland and tundra soils, whereas stochastic assembly also contributed a large fraction to the assembly of bacterial communities in forest, meadow and swamp soils. These findings provide an insight into the consequences of human activities and agricultural intensification on taxonomic homogenization of soil bacterial communities in the Qinghai-Xizang Plateau.

Net primary productivity response to precipitation varied with different ecosystems in the Tibetan Plateau over the past two millennia

The long-term pattern of terrestrial net primary productivity (NPP) response to climate change is important for estimating aboveground biomass and assessing its ecosystem function. NPP accumulation generally increased during warming intervals. However, the relationship between terrestrial NPP and precipitation change has not been comprehensively elucidated owing to the lack of long-term quantitative NPP records. Here, we present an NPP sequence quantitatively reconstructed from annual layers of fossil pollen assemblages spanning the past two millennia. We also explore the relationship between NPP and precipitation during the periods dominated by different ecosystem types. The results revealed that the NPP variation is positively correlated with the alpine meadow, dominated by Cyperaceae species, and negatively correlated with the alpine steppe, dominated by Artemisia and Poaceae species. Additionally, the NPP sequence recorded a remarkable ∼200-year periodic oscillation, which was also recorded in the precipitation sequence. The periodic NPP showed an in-phase relationship with precipitation when the regional ecosystem was marked by the symbiosis of alpine steppe and alpine meadow, and showed an anti-phase relationship with precipitation when the regional ecosystem was dominated by alpine steppe. This study elucidates the relationships between terrestrial NPP and precipitation during the past two millennia and provides foundations for predicting future terrestrial productivity.

Spatial distribution and drivers of arbuscular mycorrhizal fungi on the Tibetan Plateau.

Arbuscular mycorrhizal fungi (AMF) are pivotal in plant resource acquisition, mediating plant interactions, and influencing soil carbon dynamics. However, their biogeographical distribution in Tibetan alpine grasslands remains understudied. In this research, we examined the distribution pattern of AMF communities and their key determinants along a 2000-km transect across the Tibetan plateau, encompassing 7 alpine meadows and 8 alpine steppes. Our findings indicate that AMF community diversity and composition exhibit similarities between alpine meadows and alpine steppes, primarily influenced by latitude and evapotranspiration. At the genus level, Glomus predominated in both alpine meadow (36.49%±2.67%) and alpine steppe (41.87%±2.36%) soils, followed by Paraglomus (27.14%±3.69%, 32.34%±3.28%). Furthermore, a significant decay relationship of AMF community was observed over geographical distance. Null model analyses revealed that random processes predominantly (>50%) drove the assembly of AMF communities. In summary, our study elucidates the spatial distribution pattern of AMF in Tibetan plateau grasslands and underscores the significant influence of geographical and climatic factors on AMF community dynamics.

Spatial distribution, sources and human health risk assessment of dissolved heavy metals and metalloids in Yalong River, China

The adverse effects of metal(loid) accumulation on ecological health and human health have attracted widespread attention from the society, and the reduction of species diversity in the whole Yalong River basin due to dam construction. In this study, we investigated the distribution characteristics of metal(loid)s in the whole Yalong River basin from the point of view of metal(loid)s, identified the pollution sources, assessed the risk level, and further evaluated the risk to human health. A total of 9 heavy metals (Cr, Mn, Fe, Ni, Ag, Cd, Pb, Cu and Zn) and 1 metalloid (As) were investigated and surface water samples were collected from 17 sites along the Yalong River, which were categorized into industrial and agricultural production zones (YL1–5), alpine canyon zones (YL6–12), and alpine meadow zones (YL13–17) based on altitude and habitat. The results indicated that the density of metal(loid) in the alpine meadow area was considerably highest compared to other areas. The Zn content ranged from 64.42 to 84.55 μg/L, the Mn concentration ranged from 7.47 to 20.03 μg/L, and the Pb value ranged from 0.63 to 3.44 μg/L. In other places, the concentrations for Zn ranged from 17.88 to 37.78 μg/L, for Mn they ranged from 2.84 to 12.86 μg/L, and for Pb they ranged from 0.16 to 0.50 μg/L. The main sources of the metal(loid)s were determined by correlation analysis (CA) and principal component analysis (PCA) to be from natural factors such as crustal movement, atmospheric deposition, and water-rock washout. The water quality of Yalong River was evaluated by HEI, NI and WQI indices, and the results showed that the overall water quality of Yalong River was "excellent", in which the water quality of the alpine meadow area was better than that of the industrial and agricultural production area and the alpine canyon area. HQdermal, HQingestion and HI values are calculated to expose the harm caused by metal(loid) elements. The results indicate that all of the aforementioned values are below 1, suggesting that the potential harm caused by these elements is minimal. The value of HQdermal tends to be higher than HQingestion. Consequently, skin contact is likely the primary mechanism of exposure. This study provides a reference basis for metal(loid) detection and ecological changes caused by the dam construction process, and provides an important basis for the use and protection of surface water in the Yalong River.

Research on Sustainable Land Use in Alpine Meadow Region Based on Coupled Coordination Degree Model—From Production–Living–Ecology Perspective

Changes in land use types in alpine meadow areas have significant impacts on the ecological environment in alpine areas. Exploring land use change is crucial for land use management and optimization in alpine regions. Thus, it is necessary to analyze land use evolution and its drivers in alpine meadow regions from a production–living–ecology space (PLES) perspective by using remote sensing data. We first constructed the PLES evaluation system for Gannan. Then, we analyzed the spatial and temporal evolution characteristics and coupling degree of PLES in the study area. Finally, the driving factors affecting PLES were explored with geodetector. The conclusions of the study reveal that the distribution of productive and ecological spaces is large and concentrated, while the distribution of living spaces is more decentralized. The PLES was mainly concentrated in the area above 2500 m but below 4000 m and with a slope of 40° or less. During the study period, the area of production space showed a decreasing trend, while the areas of living and ecological space both showed increasing trends, primarily occurring at the expense of production space. DEM and GDP were the main factors affecting the distribution of PLES. The coupling level and the degree of coupling coordination were relatively stable in general, showing a pattern of “high in the east and low in the west”. The study provides technical support and a theoretical basis for the future planning of land space and ecological environment optimization in the alpine meadow regions.

Species richness and dominant functional groups enhance aboveground biomass, with no effect on belowground biomass in Qinghai-Tibet Plateau's grasslands

Understanding the role of plant diversity in maintaining grassland ecosystem functioning is of great importance in ecological research. Despite decades of research, ecologists have struggled to understand the biodiversity-ecosystem functioning relationships and how the dominance of plant functional groups impacts ecosystem function. In attempting to understand (i) the temporal patterns of above- and below-ground biomass (AGB and BGB) and species richness, (ii) whether species richness is consistently associated with AGB and BGB, and (iii) the relative contributions of plant functional groups (forb, grass, legume, and sedge) in stabilizing ecosystem function, we used biomass productivity data of meadow steppe and alpine meadow in the Qinghai-Tibet Plateau (QTP) for the period 2015–2019. Our results show that AGB for both grasslands increased, but BGB stayed steady over 5 years. The rising tendency of AGB was caused by the upward trend of AGB in forbs and grasses, which are the dominant functional groups in QTP, stressing the importance of dominant functional groups to ecosystem functioning. The biodiversity-ecosystem functioning relationships were significantly positive for AGB, stable for BGB, and negative for the BGB:AGB ratio, which highlights the crucial role of higher species richness in ecosystem functioning. Significant differences in mean species richness among sites (9–19 species in meadow steppe and 8–22 species in alpine meadow) highlight the varying levels of species diversity across sites in the QTP. While 42% of the sites showed stable species richness, the reported increasing trends in species richness at 58% of the sites indicate the potential for ecological changes or processes in these areas. AGB in both grasslands increased, while BGB remained stable with increasing precipitation. The top soil layer (0–10 cm) dominated the observed BGB in both grasslands, as abundant nutrients in the top layer provide favorable conditions for root proliferation. In meadow steppe, AGB formed an isometric relationship with BGB, indicating that AGB increased with BGB. This study concludes that species richness influenced ecosystem functioning, and forbs and grasses dominated biomass productivity, of which the topsoil layer contributed three-quarters of BGB. Our study (i) provides empirical evidence of stable to increasing species richness in both grasslands over 5 years, and (ii) highlights the role of greater species richness in enhancing ecosystem functioning. These findings serve as a scientific reference for policymaking regarding ecosystem stability.

Soil nutrient heterogeneity affects community stability through changing asynchrony in an alpine meadow on the Qinghai-Tibetan Plateau

Soil nutrients are ubiquitously heterogeneously distributed and such heterogeneity can greatly influence plant and population growth, interspecific competition and community structure and productivity. Despite these impacts, it is still unknown how soil nutrient heterogeneity affects community stability. We conducted a three-year experiment in an alpine meadow on the Qinghai-Tibetan Plateau, involving one homogeneous and six heterogeneous treatments of N, P, and K addition. The heterogeneous treatments varied in patch size, patch contrast, and number of patch types. Community stability in the homogeneous treatment tended to be the highest, likely due to high asynchrony among functional groups. However, such effects varied with patch size, patch contrast and number of patch types. Also, the effects of patch contrast and number of patch types on community stability and asynchrony among functional groups depended on patch size. The grass proportion was significantly affected by soil nutrient heterogeneity, and greater number of patch types increased the grass proportion at the small patch size, but not at the large one. Additionally, species richness, Shannon-Weiner index and Simpson index were greater in high patch contrast compared to the homogeneous treatment, but community evenness was not. These results suggest that soil nutrient heterogeneity can influence community stability by modifying functional group asynchrony and community evenness, rather than biomass proportions or other plant diversity indices. Our findings highlight the importance of incorporating soil nutrient heterogeneity in modeling the responses of alpine ecosystems to continuous nitrogen deposition and climate warming.

Plateau pika bioturbation leads to lower soil organic nitrogen fractions of bare patches in alpine meadows

The small semi–fossorial herbivore bioturbation has been verified to affect available soil nitrogen in grasslands, but the effects of small semi–fossorial herbivore bioturbation on soil organic nitrogen (SON) fractions that are main compositions of soil total nitrogen and sources of soil available nitrogen remain poorly known. The plateau pika (Ochotona curzoniae) bioturbation creates numerous bare patches, which intersperse within vegetated surfaces in grasslands. In this study, plateau pika was considered as an example animal to examine the differences of SON fractions between bare patches and vegetated surfaces under the small semi–fossorial herbivore bioturbation across six sites. This study demonstrated that acid–hydrolysable nitrogen (AHN) was 27.58% lower in bare patches than in vegetated surfaces. Amino acid nitrogen (AAN), ammonium nitrogen (AN), amino sugar nitrogen (ASN) and unknown nitrogen (UN) in bare patches were 35.23%, 17.07%, 17.70% and 19.87% lower than those in vegetated surfaces, respectively. The contribution of AAN to AHN was 5.3% lower in bare patches than in vegetated surfaces, but the contributions of AN, ASN and UN to AHN were 2.42%, 1.11%, and 1.77% higher, respectively. The response of AAN to plateau pika bioturbation was more sensitive than AN, ASN and UN. These findings verify the plateau pika bioturbation leads to a lower potential capacity of soil nitrogen supply in bare patches than in vegetated surfaces, and present a possible pattern of SON fractions in relation to small semi–fossorial herbivore bioturbation in grasslands.

Divergent impacts of fertilization regimes on below-ground prokaryotic and eukaryotic communities in the Tibetan Plateau

Chemical nutrient amendment by human activities can lead to environmental impacts contributing to global biodiversity loss. However, the comprehensive understanding of how below- and above-ground biodiversity shifts under fertilization regimes in natural ecosystems remains elusive. Here, we conducted a seven-year field experiment (2011–2017) and examined the effects of different fertilization on plant biodiversity and soil belowground (prokaryotic and eukaryotic) communities in the alpine meadow of the Tibetan Plateau, based on data collected in 2017. Our results indicate that nitrogen addition promoted total plant biomass but reduced the plant species richness. Conversely, phosphorus enrichment did not promote plant biomass and exhibited an unimodal pattern with plant richness. In the belowground realm, distinct responses of soil prokaryotic and eukaryotic communities were observed under fertilizer application. Specifically, soil prokaryotic diversity decreased with nitrogen enrichment, correlating with shifts in soil pH. Similarly, soil eukaryotic diversity decreased with increased phosphorous inputs, aligning with the equilibrium between soil available and total phosphorus. We also established connections between these soil organism communities with above-ground plant richness and biomass. Overall, our study contributes to a better understanding of the sustainable impacts of human-induced nutrient enrichment on the natural environment. Future research should delve deeper into the long-term effects of fertilization on soil health and ecosystem functioning, aiming to achieve a balance between agricultural productivity and environmental conservation.

Changes in above- versus belowground biomass distribution in permafrost regions in response to climate warming

Permafrost regions contain approximately half of the carbon stored in land ecosystems and have warmed at least twice as much as any other biome. This warming has influenced vegetation activity, leading to changes in plant composition, physiology, and biomass storage in aboveground and belowground components, ultimately impacting ecosystem carbon balance. Yet, little is known about the causes and magnitude of long-term changes in the above- to belowground biomass ratio of plants (η). Here, we analyzed η values using 3,013 plots and 26,337 species-specific measurements across eight sites on the Tibetan Plateau from 1995 to 2021. Our analysis revealed distinct temporal trends in η for three vegetation types: a 17% increase in alpine wetlands, and a decrease of 26% and 48% in alpine meadows and alpine steppes, respectively. These trends were primarily driven by temperature-induced growth preferences rather than shifts in plant species composition. Our findings indicate that in wetter ecosystems, climate warming promotes aboveground plant growth, while in drier ecosystems, such as alpine meadows and alpine steppes, plants allocate more biomass belowground. Furthermore, we observed a threefold strengthening of the warming effect on η over the past 27 y. Soil moisture was found to modulate the sensitivity of η to soil temperature in alpine meadows and alpine steppes, but not in alpine wetlands. Our results contribute to a better understanding of the processes driving the response of biomass distribution to climate warming, which is crucial for predicting the future carbon trajectory of permafrost ecosystems and climate feedback.

Source identification and assessment of heavy metal contamination in different plant species in the alpine ecosystems of Mt. Madra

Heavy metals are among important environmental pollutants due to their environmental persistence, toxicity and ability to accumulate in living organisms. The aim of the present study was to investigate the levels of aluminium (Al), boron (B), cobalt (Co), chromium (Cr), copper (Cu), and molybdenum (Mo) in plants sampled from Mt. Madra, analysed their distribution characteristics and investigated their origins using Positive Matrix Factorization (PMF) modelling. The multi-point sampling technique was used to collect samples of 26 plants from Madra Mountain at altitudes ranging from 177 m to 1347 m. Inductively-coupled plasma optical emission spectroscopy (ICP-OES) was used for the determination of metals. The metal concentrations (all in terms of mg/kg) determined by ICP-OES are the following sequences (mean ± standard deviation): Al (827.97 ± 198.95) > B (38.49 ± 2.50) > Co (0.74 ± 0.15) > Cr (1.90 ± 0.39) > Cu (7.68 ± 0.73) > Mo (0.51 ± 0.06). Based on the results obtained from the plant samples with the highest concentrations, the following metals were identified: Al (Ajuga orientalis, 4643.57 mg/kg), B (Quercus petraea, 69.25 mg/kg), Co (Ajuga orientalis, 4.23 mg/kg), Cr (Teucrium lamiifolium, 8.64 mg/kg), Cu (Ajuga orientalis, 19.75 mg/kg) and Mo (Ajuga orientalis, 1.07 mg/kg). In conclusion, the results of the source identification analysis conducted by PMF indicated that metal concentrations in the alpine zone have a primarily anthropogenic origin.

Edaphic regulation of soil organic carbon fractions in the mattic layer across the Qinghai-Tibetan Plateau

The mattic layer is a main ecological function bearer of alpine meadow soils in the Qinghai-Tibet Plateau. It has high soil organic carbon (SOC) content with a variety of SOC fractions, which are thought to have different sensitivities to climate change. The effects of soil properties and climate on the SOC fractions in the mattic layer are not well understood. To address this, we analyzed the effects of environmental factors on two SOC fractions: particulate organic carbon (POC) and mineral-associated organic carbon (MAOC). A random forest model (RFM), partial correlation analysis, and structural equation model (SEM) were used to quantify the relative effects of soil and climatic factors on SOC fractions. We found that SOC and its fractions are primarily regulated by soil properties rather than climate. Partial correlation analysis and SEM revealed that climate indirectly affects SOC by influencing soil properties. Silt+Clay and exchangeable calcium (Caex) were found to be the strongest contributing factors of MAOC and POC, respectively. A distinct shift occurs in the mechanism underlying SOC stabilization with varying soil pH. In acidic and neutral environments, amorphous Al/Fe-(hydr) oxides contribute to the stability of MAOC, whereas free Al/Fe-(hydr) oxides promote SOC mineralization. Conversely, Caex positively influences the stabilization of both POC and MAOC throughout the pH range. These results can be extrapolated to predict SOC dynamics in future soil conditions affected by environmental change, especially for use in Earth system models.

Impacts of geography, climate, soil properties and vegetation characteristics on soil C:N:P stoichiometry across the Qinghai-Tibetan Plateau

Soil C:N:P (soil organic carbon: total nitrogen: total phosphorus) stoichiometry can give important information about biogeochemical cycling in terrestrial ecosystems. The spatial patterns and driving mechanisms of soil C:N:P stoichiometry are still poorly understood on the Qinghai-Tibetan Plateau. In this study, we therefore combine data on the geographic position, climate, soil properties and vegetation characteristics of 319 sites across the plateau to investigate their relationship with the horizontal and vertical patterns of soil C, N and P concentrations and the C:N:P ratios. We observed higherSOC (30.5–46.8 mg g-1), TN (2.4–3.4 mg g-1), C:N (14.7–18.0) and N:P (6.9–8.0) in alpine meadows, forests and shrublands, and higher TP (1.6 mg g-1) in croplands. Overall, SOC, TN, TP, C:N and N:P showed decreasing trends with an amplitude of 67%, 64%, 19%, 12% and 54% respectively along the soil profile. Soil cation exchange capacity (CEC) and bulk density were the stronger environmental drivers of SOC and TN. Soil TP showed latitudinal and longitudinal increasing trends in all soil layers. Soil properties explained most of the variations in SOC (67%–90%), TN (67%–87%), C:N (61%–89%) and N:P (64%-85%), with increasing impacts along the soil profile. Geographical position and climate influenced TP both directly and indirectly through soil properties, with geographical position being the predominant driver (46%–65%) along the whole soil profile. The variation in soil C:N was mostly driven by SOC and TN, and the direct and indirect effects of the environmental factors were relatively weak. Geographical position, climate factors, soil properties and vegetation indirectly impacted soil N:P through their effects on soil TN and TP in all the soil layers. Altogether, our findings shed important light on the relative contribution of geography, climate, vegetation and soil properties on soil C:N and N:P, thus providing a better understanding of C, N, and P cycling across the Qinghai-Tibetan Plateau.

Variations in the phenological patterns of a caddisfly inhabiting the same mountain massifs: Life‐history differences in different altitudinal zones

AbstractOrganisms inhabiting mountainous regions can experience large vertical environmental changes, and show different ecological characteristics between altitudes, thus facilitating allopatric fragmentation even in geographically close populations. This study compared the life‐history patterns of a species of limnephilid caddisfly, Asynarchus sachalinensis, in several genetically differentiated populations between alpine and sub‐alpine zones in a temperate mountainous region. We showed that in the sub‐alpine populations, larval development started earlier with increasing water temperature in spring, and adult emergence was also earlier. The occurrence of adults was extremely low in mid‐summer, probably due to summer diapause, followed by a larger number of ovary‐developed females in autumn. On the other hand, in the alpine zone, increasing water temperature was delayed compared to the sub‐alpine zone, and larval development occurred from early to mid‐summer. Adult emergence and ovary‐developed individuals were concentrated in mid‐summer. Hence, summer diapause was not observed. These results indicated life‐history differences between genetically differentiated populations at different altitudes. As the timing of adult occurrence and ovarian developmental patterns differ between populations at different altitudes, it is possible that reproductive isolation is facilitated or maintained between populations.

Characterization of alpine meadow surface crack and its correlation with root-soil properties

Characterization of alpine meadow surface crack and its correlation with root-soil properties

Preference for ground cover when selecting burrow entrances in plateau pikas.

Burrow-dwelling animals such as the plateau pika (Ochotona curzoniae) often seek sturdy entrances for their burrows, which can reduce the need for frequent maintenance. The toughness of the ground surface is often reinforced by the interweaving of plant roots and often varies with the root characteristics. To better understand ground cover preferences when selecting burrow entrances by plateau pikas, we investigated the ratios of different ground covers at the rear of the entrances, as well as their coverage and underlying soil compaction in an undegraded alpine meadow on the Qinghai-Xizang Plateau. The results indicated a clear preference hierarchy of sedges > forbs > grass > bare soil. This distribution was aligned with the soil compaction hierarchy of the topsoil layer beneath each cover type. The sedge coverage was significantly negatively correlated with burrow density, suggesting that plateau pikas opt for sturdy entrances with a natural inclination toward energy conservation. However, there is consensus that the population density of plateau pikas often reaches its maximum on almost nonvegetated "black soil beaches." We hypothesized that the survival benefits brought about by vegetation degradation would be higher than the maintenance costs of burrow entrances.

Effects of Sheep Grazing and Nitrogen Addition on Dicotyledonous Seedling Abundance and Diversity in Alpine Meadows

Seedling is a crucial stage in the growth and development of plants, and the expansion and persistence of plant populations can be achieved through seed regeneration. Sheep grazing, fertilization, light, soil moisture, vegetation diversity and biomass, and litter all have potential impacts on species regeneration. We measured vegetation diversity, annual net primary productivity (ANPP), litter, ground photosynthetically active radiation (PAR), and soil moisture of alpine meadows under sheep grazing and nitrogen addition treatments, and studied their effects on the dicotyledonous seedling abundance and diversity using linear regression models (LMs) and structural equation models (SEMs). We found that sheep grazing reduced ANPP, increased vegetation diversity and PAR, and decreased soil moisture. Fertilization increased ANPP and litter, decreased vegetation diversity and PAR, but had no effect on soil moisture. Sheep grazing and fertilization both reduced the abundance of dicotyledonous seedlings, and simultaneously fertilization can reduce the diversity of dicotyledonous seedlings, while sheep grazing had no effect on the diversity of dicotyledonous seedlings. LMs showed that vegetation diversity, ANPP, and litter, rather than light and soil moisture, affected dicotyledonous seedling abundance and diversity. SEMs revealed that sheep grazing and fertilization indirectly influenced seedling regeneration through vegetation diversity rather than ANPP and litter. Our research will increase our understanding of the dicotyledonous plant regeneration process in alpine grasslands and facilitate the development of strategies for management and protection of alpine grassland.

Variation of root traits and its influences on soil organic carbon stability in response to altered precipitation in an alpine meadow

Soil organic carbon (SOC) dynamics are strongly controlled by plant roots. Yet, how variation of root traits under precipitation change influences SOC stability remains unclear. As part of a 5-year field experiment manipulating precipitation including 90 % (0.1P), 50 % (0.5P), 30 % (0.7P) decrease, and 50 % increase (1.5P), this study was designed to assess the effects of changing precipitation on root traits and production dynamics by minirhizotron and examine how such influences regulate SOC stability in an alpine meadow on the Qinghai-Tibetan Plateau. We found that root length density (RLD), specific root length (SRL), root branching intensity (RBI), and root residue carbon input (RC input) exhibited no significant response, whereas root turnover (RT), root carbon (C), nitrogen (N) concentrations and C/N ratio were altered by precipitation change with nonlinear trends. Absorptive root RT positively correlated to manipulated precipitation within the interannual precipitation range in topsoil, but it showed no significant change under extreme drought treatment. Alpine meadows can maintain the SOC content and density under varied precipitation. However, it showed significant variation in aggregate stability and organic carbon (OC) distribution in aggregates in topsoil, which were mainly due to the strong direct effects of soil moisture and partly related to RLD and RC input of transport roots. Although subsurface soil aggregate stability and OC associated with aggregates were not modified, our results indicated a risk of SOC stability variation in subsurface soil if absorptive root RT and SRL changed. These findings provide vital information to predict responses of SOC dynamics of alpine meadow to future climate change.

Mother-reliant or self-reliant: the germination strategy of seeds in a species-rich alpine meadow is associated with the existence of pericarps.

Some plants germinate their seeds enclosed by a pericarp, whereas others lack the outer packaging. As a maternal tissue, the pericarp might impart seeds with different germination strategies. Plants in a community with different flowering times might separately disperse and germinate their seeds; therefore, flowering time can be considered as one manifestation of maternal effects on the offspring. The mass of the seed is another important factor influencing germination and represents the intrinsic resource of the seed that supports germination. Using seeds from a species-rich alpine meadow located in the Hengduan Mountains of China, a global biodiversity hotspot, we aimed to illustrate whether and how the type of seed (with or without a pericarp) modulates the interaction of flowering time and seed mass with germination. Seeds were germinated in generally favourable conditions, and the speed of germination [estimated by mean germination time (MGT)] was calculated. We quantified the maternal conditions by separation of flowering time for 67 species in the meadow, of which 31 produced seeds with pericarps and 36 yielded seeds without pericarps. We also weighed 100 seeds of each species to assess their mass. The MGT varied between the two types of seeds. For seeds with pericarps, MGT was associated with flowering time but not with seed mass. Plants with earlier flowering times in the meadow exhibited more rapid seed germination. For seeds without a pericarp, the MGT depended on seed mass, with smaller seeds germinating more rapidly than larger seeds. The distinct responses of germination to flowering time and seed mass observed in seeds with and without a pericarp suggest that germination strategies might be mother-reliant for seeds protected by pericarps but self-reliant for those without such protection. This new finding improves our understanding of seed germination by integrating ecologically mediated maternal conditions and inherent genetic properties.

Effect of Plateau pika on Soil Microbial Assembly Process and Co-Occurrence Patterns in the Alpine Meadow Ecosystem.

Burrowing animals are a critical driver of terrestrial ecosystem functioning, but we know little about their effects on soil microbiomes. Here, we evaluated the effect of burrowing animals on microbial assembly processes and co-occurrence patterns using soil microbiota from a group of habitats disturbed by Plateau pikas (Ochtona curzoniae). Pika disturbance had different impacts on bacterial and fungal communities. Fungal diversity generally increased with patch area, whereas bacterial diversity decreased. These strikingly different species-area relationships were closely associated with their community assembly mechanisms. The loss of bacterial diversity on larger patches was largely driven by deterministic processes, mainly due to the decline of nutrient supply (e.g., organic C, inorganic N). In contrast, fungal distribution was driven primarily by stochastic processes that dispersal limitation contributed to their higher fungal diversity on lager patches. A bacterial co-occurrence network exhibited a positive relationship of nodes and linkage numbers with patch area, and the fungal network presented a positive modularity-area relationship, suggesting that bacteria tended to form a closer association community under pika disturbance, while fungi tended to construct a higher modularity network. Our results suggest that pikas affects the microbial assembly process and co-occurrence patterns in alpine environments, thereby enhancing the current understanding of microbial biogeography under natural disturbances.