Shrub Meadow Research Articles

Assessing the Soil Infiltration Rate of Alpine Meadows Using the Electrolyte Tracer Method

ABSTRACTGrassland on the Qinghai‐Tibet Plateau is highly susceptible to climate change and human activities, and vegetation degradation can affect biodiversity and soil erosion. Soil infiltration is a crucial water flow process that determines the amount of runoff and water storage capacity, and it is of great importance in maintaining biodiversity. This research investigated the effects of vegetation degradation and soil rates on soil infiltration rate and processes using the electrolyte tracer method. This technique accurately calculated soil infiltration rate by tracking continuous changes in the solute concentration change process throughout the experimental period and did not require calibration. Findings indicate that vegetation type, root mass, soil water content and soil porosity significantly affect soil infiltration rate. In particular, root mass was found to have a negative effect on soil infiltration rate. Soil moisture content initially dominated soil infiltration, but subsequently, soil porosity became increasingly influential in affecting infiltration in degraded meadow. Soil infiltration capacity varied more with vegetation type than with surface runoff. Shrub meadows had the highest infiltration rate followed by normal alpine meadows and degraded meadows, indicating the importance of vegetation on soil infiltration. The research also shows that mixed shrub and meadow can improve the ecological environment by introducing a more complex root system and increasing the infiltration rate. The electrolyte tracer method was used as an alternative to other methods that can be used in different environments than the one studied in this research.

Influences of climate change on carbon and water fluxes of the ecosystem in the Qinling Mountains of China

Climate change is one of the foremost challenges confronting the contemporary world. Carbon and water cycles and their interconnections of ecosystems are playing a pivotal role in assessing the impacts of climate change on ecosystems. The Qinling Mountains of China represent a focal area for research on global climate change and regional adaptation strategies. Based on historical and CMIP6 (Coupled Model Intercomparison Project Phase 6) future climatic data, the Biome-BGC model, which was sufficiently optimized with the Biome-BGC-PEST package, was used to simulate the historical and future trends of GPP (Gross primary productivity), ET (Evapotranspiration), and WUE (Ecosystem water use efficiency) in the Qinling Mountains, so as to elucidate the dynamics and spatiotemporal variations of carbon and water fluxes amidst climate change. The results showed that the GPP, ET, and WUE of the Qinling Mountains heterogeneously distributed in space, due to the dramatic disparities in carbon and water fluxes among different vegetation types in the Qinling Mountains. Among the various vegetation types, evergreen needle-leaved forest had the highest annual mean value of WUE. In the historical period of 1979-2018, deciduous broad-leaved forest had the highest annual mean value of GPP and ET, while evergreen needle-leaved forest would dominate in the future (2021-2100). For the annual GPP and ET flux variations, different vegetation cover types followed varying peak patterns in the Qinling Mountains. Deciduous broad-leaved forest, evergreen needle-leaved forest, and shrub meadow showed ’single-peak’ pattern annually, whereas the crop area displayed ’double-peak’ pattern due to the different growing seasons of crops. There also were temporal variations for the carbon and water fluxes within the same vegetation type. Future projections suggested a continuous increase in GPP and ET fluxes, underscoring the consistent role of the Qinling Mountains in water resource conservation and carbon sink amid evolving climatic conditions.

Surface soil phytolith assemblages across an altitudinal transect in the Qilian Mountains of Northwestern China, and their implications for palaeoecologic analysis in arid alpine regions

Reconstructing changes in altitudinal vegetation belts is crucial for comprehending vegetation response to past environmental changes in arid alpine regions, however, proxy data are limited. In this study, we report 51 surface soil phytolith samples from various vegetation types across an altitudinal transect in the arid alpine region of the Qilian Mountains, to elucidate the relationships between vegetation types and phytolith assemblages. Our results show that phytolith morphotypes in surface soil samples could be categorized into 16 classes, with Gobbet, Crenate, Rondel, Elongate entire, and Acutebulbosus being the predominant classes. The characteristics of surface soil phytolith assemblages vary across an altitudinal transect, reflecting differences in local vegetation. Discriminant analysis identifies Cubic, Elongate entire, Crenate, Gobbet, and Rondel as discriminant variables that correlated with five vegetation types (desert vegetation, mountain steppe vegetation, mountain coniferous forest vegetation, subalpine shrub meadow vegetation, and alpine meadow vegetation). We establish five discriminant functions based on the relationships between vegetation types and phytolith assemblages, demonstrating a high accuracy of our method for distinguishing between different vegetation types. These discriminant functions are applicable for distinguishing between diverse vegetation types in the mountains of arid inland regions of Asia. They are also effective in identifying coniferous forest vegetation in mid-latitude mountains. Therefore, these discriminant functions hold significant potential for reconstructing changes in altitudinal vegetation belts in mountainous regions and determining the vegetative types recorded by terminal lakes in arid regions. Our study introduces a new perspective on palaeoecologic analysis in arid alpine regions, advancing our understanding of ecosystem dynamics in response to environmental fluctuations.

Divergent shift of normal alpine meadow exacerbated soil loss of hillslope alpine meadows based on field experiments

Global climate change and overgrazing are driving shifts in the plant composition of grassland communities, which may profoundly affect the function of grassland ecosystems in regulating runoff and soil erosion. Here, we examined the shift effects of normal hillslope alpine meadow to shrub and severely degraded meadow states on runoff and sediment generation under natural rainfall conditions, and determined the contributions of plant and soil properties changes to soil erodibility, runoff and sediment generation by in situ rainfall experiment and monitoring on the hillslope of Qinghai-Tibetan Plateau. The results showed that normal meadow shift into severely degraded meadow state, mean weight diameter, soil saturated hydraulic conductivity, soil cohesion and soil erodibility K-factor at the topsoil decreased by 70.3%, 73.1%, 80.3% and −13.1%, respectively, and when normal meadows shift into shrub meadow state, they reduced by 49.1%, −1.3%, 49.4%, and −8.3%, respectively. Runoff and soil loss significantly changed by - 40.0% and 177.8% when normal meadow shifted into a severely degraded meadow state, while runoff and soil loss significantly changed by + 65.0% and +77.8% when normal meadow shifted into a shrub meadow state. Our findings highlight that the two divergent shifts both increased soil loss compared to the normal hillslope alpine meadows. Overall, our results indicate that the divergent shifts of normal alpine meadows exacerbated soil erodibility and soil loss of hillslope alpine meadows. These results obtained here offer a novel perspective on the regulation of runoff and soil erosion in the alpine meadow ecosystem.

A dataset of biomass of the alpine shrub meadow (2003–2020) and the alpine Kobresia humilis (2002–2020) observed at the CO2 flux monitoring station in Haibei, China

The Qinghai-Tibet Plateau (QTP) is a hotspot and sensitive region affected by global climate change. The alpine shrub and alpine Kobresia humilis meadow are the primary types of alpine meadow found in this area, which play an important role in the sustainable development of the QTP and even the global alpine meadow ecosystem. Biomass, as a direct index reflecting the production function of grassland ecosystem, can be used to effectively study the relationship between grassland ecosystem function and other influencing factors. The precise measurement and assessment of the biomass of the alpine shrub and alpine Kobresia humilis meadow are crucial elements for gaining a scientific understanding of the ecological functions of the alpine meadow on the QTP. The National Field Scientific Observation and Research Station of Alpine Grassland Ecosystem located in Haibei Prefecture, Qinghai Province (Haibei Station) has been conducting scientific monitoring of the biomass of alpine Potentilla fruticosa shrub and alpine Kobresia humilis meadow respectively since 2002 and 2003. Haibei Station has continuously accumulated the original data of these two ecosystems for 17 and 18 years respectively. In order to precisely evaluate the carbon sink potential of the alpine shrub and alpine Kobresia humilis meadow ecosystems in the QTP and even the global, and accurately predict the long-term response of the ecosystem to climate change, we published the biomass data of the alpine shrub (2003-2020) and alpine Kobresia humilis meadow (2002-2020) in the Haibei Flux Monitoring Station. This dataset includes aboveground biomass and underground biomass of the alpine shrub and alpine Kobresia humilis meadow. It can provide ground observation data support for scientific cognition, remote sensing inversion and model verification of the spatial and temporal dynamics of ecosystem biomass in alpine meadows, and contribute to the healthy and sustainable development of alpine meadows.

Divergent shift of normal alpine meadow towards shrub and degraded meadows reduces soil water retention and storage capacity

Soil saturated hydraulic conductivity (Ks) is a critical ecohydrological parameter for assessing the capacity of soil layers in grassland ecosystems to respond to precipitation efficiency, recharge groundwater and supply freshwater to rivers, which is significantly impacted by shifts in vegetation composition. Nevertheless, few studies focused on the effects of the shifts in vegetation composition on Ks of alpine grassland ecosystems. This study examined the effects of normal alpine meadow transition into shrub and severely degraded meadow stages on Ks and further qualified the driving processes. The results showed that the divergent shift of normal alpine meadows altered the soil and meadow properties. Soil water retention and storage capacity of the topsoil was reduced due to the divergent shift of the normal meadow transition into shrub meadow or severely degraded meadow. Ks and field moisture capacity (FMC) reduced by 73.1% and 64.9% in the 0–10 cm soil layer during the transition from normal to degraded meadow, while their variation in the 0–10 cm soil layer were not significant but water consumption increased during the shift from normal to shrub meadow. At the state of normal alpine meadow shift toward severely degraded meadow, the dominant factors affecting Ks were meadow cover (MC), root mass density (RMD), clay content and total porosity, with total effect coefficients of 0.48, 0.42, 0.39 and 0.69, respectively. Meanwhile, when normal alpine meadow shift toward shrub meadow, dominant factors affecting Ks were MC, non-capillary porosity, clay and sand contents, with total effect coefficients of 0.47, −0.86, −0.54 and −0.50, respectively. This study helps understanding the impacts of the shifts in vegetation composition on the ecohydrological processes in alpine meadow ecosystems in response to climate change and overgrazing.

Modern pollen distribution in moss samples along an elevational gradient in southeast Tibet

Modern pollen distribution and its relationship to vegetation and climate in the lower Yarlung Zangbo River are investigated to provide a reference for paleoenvironmental reconstructions and to improve the understanding of pollen dispersal patterns in mountainous regions. Twenty-eight modern samples collected in moss polsters from 800 and 5400 m a.s.l. are used for palynological analysis. Our results indicate that palynological assemblages and indicator species from moss polsters can reflect the vertical distribution of vegetation belts. Abies, Picea and Pinus pollen from the upper forests and shrub meadow elements (Ericaceae, Cyperaceae and Polygonum) show strong abilities to be transported upward, whereas pollen (e.g. Macaranga, Alnus and Rutaceae) and spore (e.g. Athyrium, Cyatheaceae, Dicranopteris, Pteris) taxa from the lower evergreen forests show weak abilities to be transported upward. An unusual finding is that Tsuga pollen from the lower coniferous forest tends to be transported downslope, probably due to the intense spring rainfall and associated surface runoff in the study area. Due to its potential impact on the geographic range shifts of plants, pollen dispersal may be an additional factor to be considered in studies of vegetation change in the southeastern Tibetan Plateau, such as the projection of Abies or Picea treeline under climate warming. Furthermore, the redundancy analysis shows that precipitation and wind speed are the main factors influencing pollen distribution in the study area.

The drought-induced succession decreased ecosystem multifunctionality of alpine swamp meadow

Rapid climate change and intensified anthropogenic disturbances have dropped groundwater level and altered hydrology conditions, provoked the drought-induced succession in alpine swamp meadows. However, we currently lack general cognition on how the drought-induced succession influence the ecosystem structure and functions in alpine swamp meadows. Here, we examined the changes of the main above- and below-ground ecological functions following the drought-induced succession, including swamp meadow to alpine meadow, shrub meadow, and steppe meadow. We found that both above- and below-ground ecosystem multifunctionality (EMF) indexes of the swamp meadows both decreased with the drought-induced succession. Specifically, ecosystem functions of alpine swamp meadow such as plant productivity, soil water content, soil fertility, and carbon and nitrogen all declined consistently following the drought-induced succession. Further, our analysis showed that the dynamics of the above- and below-ground EMF were positively related to plant productivity, soil hydrological properties, and nutrient availability. The decreases in soil water and nutrient contents by the drought-induced succession were the major factors that resulted in the decreased EMF. Taken together, our results demonstratedthat the drought-induced succession decreased EMF of alpine swamp meadow, and our finding revealed that soil water and nutrient contents changes were critical indicators of the EMF change during the drought-induced succession. Thus, soil hydrology and nutrient functions conservation are key to maintaining the EMF of alpine swamp meadows under ongoing climate changes.

Ecosystem services relationship characteristics of the degraded alpine shrub meadow on the Qinghai-Tibetan Plateau.

Alpine shrub meadows hold significant importance as grassland ecosystems on the Qinghai-Tibetan Plateau (QTP). They provide a range of vital ecosystem services (ESs) and are commonly utilized as summer pastures by herders, resulting in short grazing periods and high grazing intensities. Unfortunately, these practices have led to varying degrees of degradation, thereby affecting the sustainable provision of ESs. However, the current knowledge regarding changes in ESs and their characteristics under the influence of degradation, particularly the differences between alpine shrub and alpine meadow ecosystems, is insufficient. To address this gap, this study aimed to investigate and analyse changes in four ESs within alpine shrub meadows across different levels of degradation, as well as explore their relationships. The research was conducted in a summer pasture located in the northeastern QTP. The findings revealed a substantial reduction of 85.9% in forage supply due to degradation in alpine shrub meadows. Moreover, regulating services experienced a decline followed by an increase in instances of heavy degradation. Trade-offs were observed between provisioning and regulating services, while synergistic relationships were identified among different regulating services. Degradation exacerbated imbalances between provisioning and regulating services, whereas light degradation allowed for a better equilibrium between the two. Comparatively, alpine meadows exhibited higher levels of forage supply and carbon storage services, whereas alpine shrub ecosystems displayed greater nutrient supply and water retention services. It was observed that changes in ESs and relationship patterns within alpine shrub meadows were significantly influenced by the presence of alpine meadows. Consequently, safeguarding the structural integrity of alpine meadows and addressing conflicts over ESs is essential to ensure coordination and sustainability of ESs within alpine shrub meadows. The outcomes of this study provide valuable insights for ecosystem management and ecological restoration initiatives in alpine shrub meadows on the QTP.

Ecosystem Service Relationships, Drivers, and Regulation Strategies in a Degraded Alpine Shrub Meadow on the Northeastern Qinghai-Tibetan Plateau

One of the challenges of managing grasslands sustainably is the conflict between the different ecosystem services they provide. This is especially evident in the Qinghai-Tibetan Plateau (QTP) region, where fragile alpine ecosystems make balancing the needs of grassland conservation and development difficult. However, our current understanding of the relationships and drivers of ecosystem services in degraded alpine shrub meadows on the QTP is insufficient. To address this, we studied forage provisioning and water retention services in a degraded alpine shrub meadow in the northeastern QTP. We analyzed the changes and relationships between these services at different levels of degradation and identified those factors that influenced ecosystem service relationships. The results showed that the forage supply service and the water retention service of the alpine shrub meadow increased and decreased by 23.6% and 27.07%, respectively, due to degradation. The trade-offs between these two services varied depending on the degree of degradation, with light and moderate degradation showing a preference for water retention service, and heavy and extreme degradation showing a preference for forage supply. Water retention was constrained by forage supply and both services showed an exponential function form of decay. The physical and chemical properties of the soil in the alpine shrub meadow remained relatively stable during the degradation process, with only soil organic carbon (SOC), total potassium (TK), and total nitrogen (TN) decreasing significantly. SOC may have indirectly influenced the relationship between the two services by affecting water retention. This study provides insights into alpine shrub meadow management and conservation on the QTP.

Kobresia pygmaea meadows as disclimax communities in the same geographic and climatic environments in Qinghai–Tibet Plateau, China

Abstract Kobresia meadows are the main pastures for animal husbandry on the Qinghai–Tibet Plateau, and may represent alternative steady states associated with different grazing intensities. The ability of other plant communities to succeed these meadows remains unclear. In this study, the historical data of plant communities were analyzed in terms of the soil profile, and the present characteristics were identified by investigating their plant communities. Four types of steady states were identified, corresponding to grazing intensities of >11, 8–11, 5.5–8 and <5.5 sheep/ha. Drought alpine swamp meadows and shrub meadows could succeed to K. pygmaea meadows and K. humilis meadows under overgrazing, and their total biomass and edible biomass (estimated by Gramineae and Cyperaceae) decreased with increasing grazing intensity. The regime shift of the states occurred at a grazing intensity of 8–11 sheep/ha. This value thus represented the threshold of significant change in the production and ecological service function in the Kobresia meadow succession process. In general, increasing grazing intensities can adversely affect the service ability of meadows for livestock production and ecosystem stabilization. Our results revealed the potential degraded succession process of the alpine Kobresia meadow and the succession direction in the restoration process of degraded meadows. Additionally, this study provided a theoretical basis for evaluating the fitness between the livestock bearing capacity and carrying capacity in steady states and academic reference for policy setting pertaining to the utilization of Kobresia meadows in a sustainable development framework.

Effects of long-term warming on soil prokaryotic communities in shrub and alpine meadows on the eastern edge of the Qinghai-Tibetan Plateau

The variations in response of the soil prokaryote community structure to long-term climate warming among different vegetation types in alpine areas are not fully understood. After an 18-year warming experiment, changes in the diversity and structure of soil prokaryote communities in alpine and shrub meadows of the Tibetan Plateau were analyzed based on 16S rDNA MiSeq sequencing. Proteobacteria (26.70 %), Actinobacteria (20.90 %), and Acidobacteria (13.09 %) were the dominant soil bacterial communities; however, Crenarchaeota (5.69 %) was the dominant archaea at the phylum level. Warming did not significantly affect the top 11 prokaryotic communities in the shrub meadow soil. In meadow soils, however, we found an increase in the relative abundances of Crenarchaeota, Acidobacteria, Chloroflexi, and Planctomycetes and a decrease in the relative abundances of Actinobacteria and Proteobacteria. In terms of alpha-diversity, warming significantly increased the Chao1 and the observed species indices in both the meadow and shrub meadow soils. The soil prokaryote community in the meadow soil was more sensitive to simulated warming than that in the shrub meadow soil. The soil pH and water content were the primary factors that influenced variation in the overall structure and diversity of the soil prokaryotic community. Therefore, the response of soil prokaryote composition and structure (at the phylum level) to long-term warming largely depended on vegetation type, but the response of alpha-diversity was similar among different vegetation types. We conclude that the vegetation type plays a regulatory role in the sensitivity of alpine soil microbial communities to warming.

Proximity to oilseed rape fields affects plant pollination and pollinator-mediated selection on a co-flowering plant on the Tibetan Plateau.

The ecological effects of mass-flowering crops on pollinator abundance and species richness of neighbouring habitats are well established, yet the potential evolutionary consequences remain unclear. We studied effects of proximity to a mass-flowering crop on the pollination of local co-flowering plants and on patterns of natural selection on a pollination-generalised plant on the Tibetan Plateau. We recorded pollinator visitation rates and community composition at different distances (near vs. far) to oilseed rape (Brassica napus) fields in two habitat types and quantified pollinator-mediated selection on attractive traits of Trollius ranunculoides. The proximity to oilseed rape increased pollinator visitation in neighbouring alpine meadows and changed pollinator composition in neighbouring shrub meadows. Trollius ranunculoides in the alpine meadow near oilseed rape received three times more pollinator visits (mainly bees) and consequently had a 16.5% increase in seed set but also received slightly more heterospecific pollen per stigma. In contrast, pollinator visitation to T. ranunculoides in the shrub meadow near oilseed rape was three times lower (mainly flies), leading to a 10.7% lower seed despite no effect on pollen deposition. The proximity to the oilseed rape field intensified pollinator-mediated selection on flower size and weakened selection on flower height of T. ranunculoides in the alpine meadow but did not affect phenotypic selection on either trait in the shrub meadow. Our study highlights context-dependent variation in plant-pollinator interactions close to mass-flowering oilseed rape, suggesting potential effects on the evolution of flower traits of native plants through altered pollinator-mediated selection. However, context dependence may make these effects difficult to predict.

Seasonal resource selection and movement ecology of free‐ranging horses in the western United States

AbstractUnderstanding factors driving resource selection and habitat use of different species is an important component of management and conservation. Feral horses (Equus caballus) are free ranging across various vegetation types in the western United States, yet few studies have quantified their resource selection and seasonal use. We conducted a study to determine effects of vegetation community, distance to water, and topographic variables on seasonal resource selection in 2 feral horse populations in Great Basin sagebrush (Artemisia spp.) ecosystems of west‐central Utah, USA: Conger Herd Management Area (HMA) and Frisco HMA. We deployed global positioning system (GPS) radio‐collars on 38 female horses and GPS‐transmitters braided and glued into the tail hair of 14 males, collecting locations every 2 hours for 1–4 years between 2016 and 2020. We calculated home range size and core use area of social groups (harems) and bachelor males using auto‐correlated kernel density estimators for each biologically defined season (breeding, fall, and winter) per study year. We examined seasonal home range size and overlap of harem groups and bachelor males and compared movement speed of bachelors and harems among seasons. We determined seasonal resource selection in a use‐availability framework using resource selection functions. We hypothesized that horses would select for areas of high herbaceous vegetation, that water would be a key variable in resource selection models like other equids, and home range size in winter would be largest because horses can eat snow for hydration and could therefore roam farther from surface water. Mean annual home range size was 103.12 ± 37.38 km2 (SD) for Conger harems and 117.47 ± 32.75 km2 for Frisco harems. At Conger there was no difference in home range size between harem groups and bachelor males, but home range size was smaller in winter than other seasons, whereas winter home range size at Frisco was larger than other seasons. Bachelor males moved at higher speeds than harems during all seasons, and harem groups from both populations had lower movement speeds in winter. Harem groups had distinct winter ranges with little overlap on breeding season ranges. In both populations, all horses selected for herbaceous vegetation types and avoided forest relative to shrubland throughout the year. Harems at Frisco were consistently located closer to water sources, whereas selection for water sources by Conger harems varied seasonally, with winter having the lowest selection. Harem groups at Conger had an average of 10.6% of their home ranges outside the HMA boundary and Frisco harems had up to 66.8% outside, likely because of the horseshoe shape of Frisco HMA in which shrub meadows (foraging areas) comprise the horseshoe center, which is outside the HMA. Our results highlight the importance of water sources, which were a key predictor of horse movement patterns in our study. We emphasize the utility of telemetry devices to understand resource selection of feral horses at a fine scale, enabling management to be more targeted and facilitate planning.

Control of Mosses on Water Flux in an Alpine Shrub Site on the Qilian Mountains, Northwest China.

Mosses are an important component of the alpine shrub, but little is known about their contribution to ecosystem water and energy exchange, especially potential opportunities for alpine shrub expansion under a warming climate. We studied the role of mosses in alpine shrub evapotranspiration by conducting herb and moss removal experiments with different Potentilla fruticosa L. shrub coverage in the Qilian Mountains, Northwest China. The understory evapotranspiration was measured using lysimeters in different shrub coverage (dense shrub cover, medium shrub cover, and thin shrub cover) during the growing season of 2012. The understory evapotranspiration is about 1.61 mm per day in the control treatment (intact moss and herbs) during the growing season, and the evapotranspiration rates differed significantly between canopy covers. We found a 22% increase in evapotranspiration losses after removing the moss layer compared to the control treatment lysimeter with an intact moss layer in the shrub site. This suggests that most of the understory evaporation originated from the organic layer underlying the moss layer. Given this study's large moss evaporation rates, understory contributions cannot be ignored when interpreting eddy covariance data for the whole alpine ecosystem. Our results show that mosses may exert strong controls on understory water fluxes in alpine shrub meadow ecosystems and suggest that changes in moss cover may have significant consequences for season frozen soil thaw.

Effect of grazing exclusion on emission of greenhouse gases and soil organic carbon turnover in alpine shrub meadow

Grazing exclusion (GE) is a management option used widely to restore degraded grassland and improve grassland ecosystems. However, the impacts of GE on soil properties and greenhouse gas emissions of alpine shrub meadow are still unclear, especially long-term GE of more than ten years. To fill part of this gap, we examined the effects of long-term GE of alpine shrub meadow on soil nutrients, soil properties, greenhouse gas emissions (CO2 and CH4) and soil organic carbon (SOC) turnover. When compared to grazed grassland (GG), long-term GE resulted in: 1) greater SOC, nitrogen (N), and phosphorous (P) content, especially in the 20–30 cm soil layer; 2) greater soil C:N, C:P and N:P ratios in the 20–30 cm depth; 3) greater soil CO2, but lesser CH4 emission during the growing season; and 4) much faster SOC turnover time (0–30 cm). GE of more than ten years can increase grassland C reserves and improve the C sequestration capacity of the ecosystem. Results from this study can have important implications in developing future grassland management policies on soil nutrient balances, restoration of degraded grassland and controlling shrub expansion.

Altitudinal Variation Influences Soil Fungal Community Composition and Diversity in Alpine-Gorge Region on the Eastern Qinghai-Tibetan Plateau.

Soil fungi play an integral and essential role in maintaining soil ecosystem functions. The understanding of altitude variations and their drivers of soil fungal community composition and diversity remains relatively unclear. Mountains provide an open, natural platform for studying how the soil fungal community responds to climatic variability at a short altitude distance. Using the Illumina MiSeq high-throughput sequencing technique, we examined soil fungal community composition and diversity among seven vegetation types (dry valley shrub, valley-mountain ecotone broadleaved mixed forest, subalpine broadleaved mixed forest, subalpine coniferous-broadleaved mixed forest, subalpine coniferous forest, alpine shrub meadow, alpine meadow) along a 2582 m altitude gradient in the alpine–gorge region on the eastern Qinghai–Tibetan Plateau. Ascomycota (47.72%), Basidiomycota (36.58%), and Mortierellomycota (12.14%) were the top three soil fungal dominant phyla in all samples. Soil fungal community composition differed significantly among the seven vegetation types along altitude gradients. The α-diversity of soil total fungi and symbiotic fungi had a distinct hollow pattern, while saprophytic fungi and pathogenic fungi showed no obvious pattern along altitude gradients. The β-diversity of soil total fungi, symbiotic fungi, saprophytic fungi, and pathogenic fungi was derived mainly from species turnover processes and exhibited a significant altitude distance-decay pattern. Soil properties explained 31.27−34.91% of variation in soil fungal (total and trophic modes) community composition along altitude gradients, and the effects of soil nutrients on fungal community composition varied by trophic modes. Soil pH was the main factor affecting α-diversity of soil fungi along altitude gradients. The β-diversity and turnover components of soil total fungi and saprophytic fungi were affected by soil properties and geographic distance, while those of symbiotic fungi and pathogenic fungi were affected only by soil properties. This study deepens our knowledge regarding altitude variations and their drivers of soil fungal community composition and diversity, and confirms that the effects of soil properties on soil fungal community composition and diversity vary by trophic modes along altitude gradients in the alpine–gorge region.

Shrub Expansion is Mainly Affected by Climate-Dominated Functional Traits in Alpine Meadow

Shrub expansion has been reported mostly in dry and semi-arid ecosystems worldwide. Shrub expansion is also a serious ecological issue in alpine and cold regions. Multiple drivers, including anthropogenic and environmental factors, contribute to this phenomenon. However, the relative effects of climate and soil factors on shrub expansion are incompletely quantified or understood in the alpine meadow, and quantifying how these factors result in variations in functional traits associated with shrub expansion is crucial considering that functional traits are tightly related to ecosystem processes. In this study, we investigated the vegetation of an alpine shrub meadow composed of Potentilla fruticosa L. In the Zoige Plateau, along an elevation gradient. We assessed the direct and indirect effects of climate and soil factors on functional traits, shrub expansion strength (measured as the total biomass), and relative abundance (via functional traits). We found that climate factors, namely, the mean temperature of the warmest quarter (bio10), mostly affected specific leaf areas and specific lobe volume, which were the most important traits related to shrub expansion. Soil factors, except soil water content (SWC), had weak effects on functional traits closely related to shrub expansion. Our partial least square path modeling model explained 99% of the variation in shrub biomass. Results suggest that climate change not only affected functional traits but also influenced shrub expansion in the Zoige Plateau. Thus, management measures to control expansion should consider these drivers for more accurate forecasting and cost effectiveness. Understanding the mechanism of alpine shrub expansion contributes to the delaying of the expansion process and ensures steady pastoral production.

Response of Soil Water Storage to Meteorological Factors in Alpine Shrub Meadow on Northeastern Qinghai–Tibetan Plateau

The Qinghai–Tibet Plateau (QTP) has an important function in ensuring the water ecological security of China, even Asia, and the soil water storage of alpine grassland is an important part of the ecosystem water. Grassland degradation directly affects the soil water storage capacity. However, the impact of degradation on specific soil storage capacity, especially alpine shrubs, is rarely studied. Here, we chose two plots of alpine non-degraded shrub and degraded shrub, using the automatic soil moisture monitoring system to study the change process of soil moisture storage, and then adopted the boosted regression tree (BRT) model to quantitatively evaluate the relative influence of environmental variables on soil water storage. Our results show: (1) The soil water storage in the growing season (May–September) is higher than that in the non-growing season (January–April and October–December), and the soil water storage reaches its highest in mid-July. (2) During the growing season, the 100 cm soil temperature was the most important factor affecting the seasonal variation in soil water storage, accounting for 51% of the total variation. During the non-growing season, the 40 cm soil temperature was the most important factor affecting the variation in soil water storage, accounting for 80% of the total variation. (3) The soil water storage of non-degraded Potentilla fruticosa shrub meadow increased by 6–25%, compared with degraded grassland shrub meadow during growing-season. (4) Various meteorological factors have a weak impact on soil water storage.

Impacts of alpine shrub-meadow degradation on its ecosystem services and spatial patterns in Qinghai-Tibetan Plateau

• UAV is used to detect the spatial pattern of alpine shrub-meadow degradation. • Ecosystem services changes in degraded alpine shrub meadow are non-linear. • Spatial pattern characteristics may fail to interpret ecosystem service changes. Alpine shrub-meadow is an important ecosystem type on the Qinghai-Tibetan Plateau, providing a variety of ecosystem services while supporting the livelihoods of pastoralists. However, there is a clear lack of understanding of the changes in spatial patterns and ecosystem services of alpine shrub-meadow degradation. This study combined aerial photography and ground surveys to investigate and analyse the impact of degradation on the spatial patterns of alpine shrub-meadow and their ecosystem services, and the relationships between the spatial patterns and ecosystem services. The results showed that degradation led to fragmentation and patchiness in alpine shrub-meadow, as evidenced by a decrease in the proportion of shrub and meadow area and average patch size, as well as the complexity of patch boundaries and shapes. Light and moderate degradation reduced all ecosystem services in alpine shrub-meadow, with carbon storage, nutrient supply and water retention services decreased by an average of 27.4%, 17.3% and 13.8% respectively, while forage supply services decreased by 65.2% at heavy degradation, and the reduction in alpine meadow ecosystem services was even greater. Regulating services increased again at heavy degradation due to the accumulation and slow decomposition of plant underground roots, and rodent activity. The spatial patterns of the meadow layer were more closely related to its ecosystem services than the shrub layer, and fragmentation and patchiness were positively related to ecosystem services. Our findings suggest that the impact of degradation on alpine shrub-meadow ecosystem services may be non-linear and that the relationships between spatial patterns and ecosystem services need to be interpreted with caution and should be analysed comprehensively with a wider range of influencing factors. Our results have implications for grassland restoration and ecosystem service management on the Qinghai-Tibetan Plateau.