Sugar and organic acid availability modulate soil diazotroph community assembly and species co-occurrence patterns on the Tibetan Plateau

The alpine grasslands on the Tibetan Plateau are sensitive and vulnerable to climate change. However, it is still unknown how precipitation use efficiency (PUE), the ratio of ANPP to precipitation, is related to community assembly of plant species, functional groups or traits for the Tibetan alpine grasslands along actual environmental gradients. We conducted a multi-site field survey at grazing-excluded pastures across meadow, steppe and desert-steppe to measure aboveground biomass in August, 2010. We used species richness, the Shannon diversity index, and cover-weighted functional group composition (FGC) of 1-xerophytes, 2-mesophytes, and 3-hygrophytes to describe community assembly at the species level; and chose community-level leaf area index (LAIc ), specific leaf area (SLAc ), and species-mixed foliar δ13C to quantify community assembly at the functional trait level. Our results showed that PUE decreased with increasing accumulated active temperatures (AccT) when daily temperature average is higher than 5°C, but increased with increasing climatic moisture index, which was demined as the ratio of growing season precipitation (GSP) to AccT. We also found that PUE increased with increasing species richness, the Shannon diversity index, FGC and LAIc ,decreased with increasing foliar δ13C, and had no relation with SLAc at the regional scale. Neither soil total nitrogen nor organic carbon has no influence on PUE at the regional scale. The community assembly of the Shannon index, LAIc and SLAc together accounted for 46.3 % of variance in PUE, whilst climatic moisture index accounted for 47.9 % of variance in PUE at the regional scale. This implies that community structural properties and plant functional traits can mediate the sensitivity of alpine grassland productivity in response to climate change. Thus, a long-term observation on community structural and functional changes is recommended for better understanding the response of alpine ecosystems to regional climate change on the Tibetan Plateau.

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Community assembly and functional leaf traits mediate precipitation use efficiency of alpine grasslands along environmental gradients on the Tibetan Plateau

PeerJ ◽

10.7717/peerj.2680 ◽

2016 ◽

Vol 4 ◽

pp. e2680 ◽

Cited By ~ 4

Author(s):

Shaowei Li ◽

Jianshuang Wu

Keyword(s):

Climate Change ◽

Tibetan Plateau ◽

Community Assembly ◽

Environmental Gradients ◽

Diversity Index ◽

Regional Scale ◽

The Tibetan Plateau ◽

Alpine Grasslands ◽

Use Efficiency ◽

Precipitation Use Efficiency

The alpine grasslands on the Tibetan Plateau are sensitive and vulnerable to climate change. However, it is still unknown how precipitation use efficiency (PUE), the ratio of aboveground net primary productivity (ANPP) to precipitation, is related to community assembly of plant species, functional groups or traits for the Tibetan alpine grasslands along actual environmental gradients. We conducted a multi-site field survey at grazing-excluded pastures across meadow, steppe and desert-steppe to measure aboveground biomass (AGB) in August, 2010. We used species richness (SR), the Shannon diversity index, and cover-weighted functional group composition (FGC) of 1-xerophytes, 2-mesophytes, and 3-hygrophytes to describe community assembly at the species level; and chose community-level leaf area index (LAIc), specific leaf area (SLAc), and species-mixed foliar δ13C to quantify community assembly at the functional trait level. Our results showed that PUE decreased with increasing accumulated active temperatures (AccT) when daily temperature average is higher than 5 °C, but increased with increasing climatic moisture index (CMI), which was demined as the ratio of growing season precipitation (GSP) to AccT. We also found that PUE increased with increasing SR, the Shannon diversity index, FGC and LAIc, decreased with increasing foliar δ13C, and had no relation with SLAcat the regional scale. Neither soil total nitrogen (STN) nor organic carbon has no influence on PUE at the regional scale. The community assembly of the Shannon index, LAIcand SLActogether accounted for 46.3% of variance in PUE, whilst CMI accounted for 47.9% of variance in PUE at the regional scale. This implies that community structural properties and plant functional traits can mediate the sensitivity of alpine grassland productivity in response to climate change. Thus, a long-term observation on community structural and functional changes is recommended for better understanding the response of alpine ecosystems to regional climate change on the Tibetan Plateau.

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Distinct assembly mechanisms underlie similar biogeographical patterns of rare and abundant bacteria in Tibetan Plateau grassland soils

10.21203/rs.2.19893/v1 ◽

2020 ◽

Author(s):

Mukan Ji ◽

Weidong Kong ◽

James Stegen ◽

Linyan Yue ◽

Fei Wang ◽

...

Keyword(s):

Tibetan Plateau ◽

Community Assembly ◽

Climatic Factors ◽

Variation Partitioning ◽

Terrestrial Ecosystems ◽

The Tibetan Plateau ◽

Grassland Soils ◽

Ecological Processes ◽

Local Factors ◽

Grassland Types

Abstract Background: Bacteria in low abundance represent the majority of Earth’s biodiversity and perform vital ecological functions, but little is known about their biogeography nor the ecological processes that drive their community assembly in terrestrial ecosystems. Here, we investigated the community compositions and phylogenies of rare (relative abundance < 0.1%) and abundant (> 1%) soil bacteria along a transect containing three alpine grassland types (meadow, steppe, and desert) on the Tibetan Plateau. Results: Our results revealed similar biogeographical patterns of rare and abundant bacteria, with their community compositions and phylogenies shifting gradually along the transect. The similar patterns, however, were driven by contrasting community assembly processes, with rare subcommunity being more heavily influenced by stochasticity (72%) than abundant (57%). The composition of abundant subcommunity (80%) was better explained by local (including soil and vegetation factors), geospatial and climatic factors than that of rare subcommunity (41%), while the phylogeny of the rare one (36%) was better explained than that of the abundant one (29%). Variation partitioning analysis indicated that pure local factors consistently explained a higher proportion of the community composition than geospatial factors in both rare (12.3% and 8.7%, respectively) and abundant bacteria (18.3% and 14.1%, respectively). In contrast, the phylogeny of rare subcommunity was explained by local and geospatial factors equally (11.5% and 11.9%, respectively), while that of abundant subcommunity was more explained by geospatial (22.1%) than local factors (11.3%). Furthermore, our results revealed a tighter connection between the community phylogeny and composition in rare than in abundant bacteria. Conclusions: Our results revealed consistent biogeographical patterns of rare and abundant bacteria in grassland soils, but their assembly processes were distinct. We further demonstrated that rare subcommunity was less predictable than the abundant subcommunity by environmental and geospatial factors. Rare and abundant bacteria responded differentially to factors, which was attributed to the distinct life strategies. Our study provides novel insights into the assembly processes and biographical patterns of rare and abundant bacteria in terrestrial ecosystems.

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Ecological processes underlying community assembly of aquatic bacteria and macroinvertebrates under contrasting climates on the Tibetan Plateau

The Science of The Total Environment ◽

10.1016/j.scitotenv.2019.134974 ◽

2020 ◽

Vol 702 ◽

pp. 134974 ◽

Cited By ~ 2

Author(s):

Annika Vilmi ◽

Wenqian Zhao ◽

Félix Picazo ◽

Mingjia Li ◽

Jani Heino ◽

...

Keyword(s):

Tibetan Plateau ◽

Community Assembly ◽

The Tibetan Plateau ◽

Ecological Processes ◽

Aquatic Bacteria

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Community assembly and functional leaf traits mediate precipitation use efficiency of alpine grasslands along environmental gradients on the Tibetan Plateau

10.7287/peerj.preprints.2472 ◽

2016 ◽

Author(s):

Shaowei Li ◽

Jianshuang Wu

Keyword(s):

Climate Change ◽

Tibetan Plateau ◽

Community Assembly ◽

Environmental Gradients ◽

Diversity Index ◽

Regional Scale ◽

The Tibetan Plateau ◽

Alpine Grasslands ◽

Moisture Index ◽

Use Efficiency

The alpine grasslands on the Tibetan Plateau are sensitive and vulnerable to climate change. However, it is still unknown how precipitation use efficiency (PUE), the ratio of ANPP to precipitation, is related to community assembly of plant species, functional groups or traits for the Tibetan alpine grasslands along actual environmental gradients. We conducted a multi-site field survey at grazing-excluded pastures across meadow, steppe and desert-steppe to measure aboveground biomass in August, 2010. We used species richness, the Shannon diversity index, and cover-weighted functional group composition (FGC) of 1-xerophytes, 2-mesophytes, and 3-hygrophytes to describe community assembly at the species level; and chose community-level leaf area index (LAIc ), specific leaf area (SLAc ), and species-mixed foliar δ13C to quantify community assembly at the functional trait level. Our results showed that PUE decreased with increasing accumulated active temperatures (AccT) when daily temperature average is higher than 5°C, but increased with increasing climatic moisture index, which was demined as the ratio of growing season precipitation (GSP) to AccT. We also found that PUE increased with increasing species richness, the Shannon diversity index, FGC and LAIc ,decreased with increasing foliar δ13C, and had no relation with SLAc at the regional scale. Neither soil total nitrogen nor organic carbon has no influence on PUE at the regional scale. The community assembly of the Shannon index, LAIc and SLAc together accounted for 46.3 % of variance in PUE, whilst climatic moisture index accounted for 47.9 % of variance in PUE at the regional scale. This implies that community structural properties and plant functional traits can mediate the sensitivity of alpine grassland productivity in response to climate change. Thus, a long-term observation on community structural and functional changes is recommended for better understanding the response of alpine ecosystems to regional climate change on the Tibetan Plateau.

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Increasing soil pH enhances the network interactions among bacterial and archaeal microbiota in alpine grasslands of the Tibetan Plateau

10.21203/rs.2.18880/v1 ◽

2019 ◽

Author(s):

Beibei Chen ◽

Shuaiwei Luo ◽

Beibei Ma ◽

Wei Qi ◽

Changdong Cao ◽

...

Keyword(s):

Tibetan Plateau ◽

Soil Ph ◽

Microbial Interactions ◽

The Tibetan Plateau ◽

Alpine Grasslands ◽

Soil Microbiota ◽

Neutral Ph ◽

Topological Features ◽

Node Level ◽

Occurrence Patterns

Abstract Background: Soil functioning and processes are driven by complex microbial interactions. It is therefore critical to understand the co-occurrence patterns of soil microbiota, especially in fragile alpine ecosystems. Here we explored the geographic patterns of the topological features and the major drivers shaping the topological structure of the co-occurrence network for bacterial and archaeal microbiota in alpine grasslands of the Tibetan Plateau based on high-throughput sequencing. Results: Soil pH was the most important environmental variable for predicting the topological features of the microbial network at both network and node levels. Associations among soil microbiota were enhanced with increasing pH (5.17–8.92), and the network was the most stable at neutral pH (7). Node-level topological features suggested that taxa of the high-pH cluster had more important roles in maintaining complex network connections than taxa of the low-pH cluster. Network-level features revealed closer relationships among soil microbiota in the steppe ecosystem than in the meadow ecosystem. Archaeal operational taxonomic units (OTUs) with higher values for node-level topological features appeared to be more important than bacterial OTUs in maintaining complex connections. The co-occurrence patterns of bacterial OTUs with lower node-level feature values followed a power-law distribution, whereas those of archaeal OTUs did not. Conclusions: Soil pH plays a decisive role in determining the complex interactions among soil microbiota in alpine grassland ecosystems of the Tibetan Plateau, with a more stable co-occurrence network at neutral pH. Bacterial and archaeal taxa, which occupy distinct network niches, have closer relationships in alpine steppe than in alpine meadow ecosystems.

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