scholarly journals Climate Variability Rather Than Livestock Grazing Dominates Changes in Alpine Grassland Productivity Across Tibet

2021 ◽  
Vol 9 ◽  
Author(s):  
Meng Li ◽  
Jianshuang Wu ◽  
Yunfei Feng ◽  
Ben Niu ◽  
Yongtao He ◽  
...  
Keyword(s):  
Climate Change ◽  
Central Government ◽  
Net Primary Production ◽  
Grazing Intensity ◽  
Relative Effect ◽  
Livestock Grazing ◽  
Alpine Grassland ◽  
The Tibetan Plateau ◽  
Alpine Grasslands ◽  
Grassland Productivity

Alpine grasslands on the Tibetan Plateau, being vulnerable to environmental and anthropogenic changes, have experienced dramatic climate change and intensive livestock grazing during the last half-century. Climate change, coupled with grazing activities, has profoundly altered alpine grassland function and structure and resulted in vast grassland degradation. To restore degraded grasslands, the Central Government of China has implemented the Ecological Security Barrier Protection and Construction Project since 2008 across the Tibetan Autonomous Region. However, the relative effect of climate change and grazing activities on the variation in alpine grassland productivity is still under debate. In this study, we quantified how aboveground net primary production (ANPP) varied before (2000–2008) and after (2009–2017) starting the project across different alpine grasslands and how much variance in ANPP could be attributed to climate change and grazing disturbance, in terms of temperature, precipitation, solar radiation, and grazing intensity. Our results revealed that Tibet’s climate got warmer and wetter, and grazing intensity decreased after starting the project. Mean ANPP increased at approximately 81% of the sites, on average from 27.0 g C m–2 during 2000–2008 to 28.4 g C m–2 during 2009–2017. The ANPP positively correlated with annual temperature and precipitation, but negatively with grazing intensity for both periods. Random forest modeling indicated that grazing intensity (14.5%) had a much lower influence in controlling the dynamics of grassland ANPP than precipitation (29.0%), suggesting that precipitation variability was the key factor for alpine grassland ANPP increase across Tibet.

scholarly journals Precipitation and aridity index regulating spatial patterns of vegetation production and species diversity based on alpine grassland transect, Tibetan Plateau

2016 ◽  
Author(s):  
Jian Sun
Keyword(s):  
Tibetan Plateau ◽  
Primary Production ◽  
Alpine Meadow ◽  
Net Primary Production ◽  
Aridity Index ◽  
Alpine Grassland ◽  
The Tibetan Plateau ◽  
Aboveground Net Primary Production ◽  
Alpine Steppe ◽  
Unimodal Pattern

Although the relationship between the aboveground net primary production (ANPP) and speciesdiversity (SR) have been widely reported, there is considerable disagreement about the fitting patterns of SR–ANPP, which has been variously described as ‘positive’, ‘negative’, ‘unimodal’, ‘U-shaped’ and so on. Not surprisingly, the effect-factors including precipitation, aridity index and geographic conditions (e.g.,altitude, longitude and latitude) on ANPP and SR continue to interest researchers, especially the effects at high altitude regions. We investigated ANPP and SR from 113 sampled sites (399 plots) across alpine meadow and steppe in the Tibetan Plateau, which included Tibet, Qinghai and Sichuan province. The effects of various environmental factors (precipitation, temperature, aridity index, altitude, longitude,latitude and vegetation type on SR and ANPP) were explored. The results indicate that a unimodal pattern was confirmed between ANPP and SR in alpine steppe (R 2 =0.45, P <0.0001), alpine meadow ( R 2 =0.4, P <0.0001), and all samples across alpine grassland ( R 2 =0.52, P <0.0001). For the aboveground net primary production, the appropriate precipitation and aridity is 600mm and 42, respectively. Under thesame moisture conditions, the maximum value of diversity is 0.75. Longitude ( R 2 =0.69, P <0.0001) and altitude ( R 2 =0.48, P <0.0001) have positive and negative effects on aboveground net primary production, and a similar relationship exists with diversity ( R 2 =0.44, P <0.0001 and R 2 =0.3, P <0.0001).The same patterns of diversity and production responding to precipitation and the aridity index were evident in alpine steppe and meadow, and a unimodal pattern was confirmed between ANPP and SR in both locations.

scholarly journals Projected changes of alpine grassland carbon dynamics in response to climate change and elevated CO2concentrations under Representative Concentration Pathways (RCP) scenarios

2019 ◽  
Author(s):  
Pengfei Han ◽  
Xiaohui Lin ◽  
Wen Zhang ◽  
Guocheng Wang
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Carbon Cycle ◽  
Carbon Budget ◽  
Carbon Fluxes ◽  
Carbon Dynamics ◽  
Alpine Grassland ◽  
The Tibetan Plateau ◽  
Rcp Scenarios ◽  
Representative Concentration Pathways

AbstractThe Tibetan Plateau is an important component of the global carbon cycle due to the large permafrost carbon pool and its vulnerability to climate warming. The Tibetan Plateau has experienced a noticeable warming over the past few decades and is projected to continue warming in the future. However, the direction and magnitude of carbon fluxes responses to climate change and elevated CO2concentration under Representative Concentration Pathways (RCP) scenarios in the Tibetan Plateau grassland are poorly known. Here, we used a calibrated and validated biogeochemistry model, CENTURY, to quantify the contributions of climate change and elevated CO2on the future carbon budget in the alpine grassland under three RCP scenarios. Though the Tibetan Plateau grassland was projected a net carbon sink of 16 ~ 25 Tg C yr-1in the 21st century, the capacity of carbon sequestration was predicted to decrease gradually because climate-driven increases in heterotrophic respiration (Rh) (with linear slopes 0.49 ~ 1.62 g C m-2yr-1) was greater than the net primary production (NPP) (0.35 ~ 1.52 g C m-2yr-1). However, the elevated CO2contributed more to plant growth (1.9% ~ 7.3%) than decomposition (1.7% ~ 6.1%), which could offset the warming-induced carbon loss. The interannual and decadal-scale dynamics of the carbon fluxes in the alpine grassland were primarily controlled by temperature, while the role of precipitation became increasingly important in modulating carbon cycle. The strengthened correlation between precipitation and carbon budget suggested that further research should consider the performance of precipitation in evaluating carbon dynamics in a warmer climate scenario.

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

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.

How land management and water availability control ecosystem-atmosphere carbon exchange in the Karoo, South Africa

2020 ◽  
Author(s):  
Oksana Rybchak ◽  
Kanisios Mukwashi ◽  
Justin Du Toit ◽  
Gregor Feig ◽  
Mari Bieri ◽  
...  
Keyword(s):  
Climate Change ◽  
South Africa ◽  
South African ◽  
Land Management ◽  
Water Availability ◽  
Grazing Intensity ◽  
Carbon Fluxes ◽  
Livestock Grazing ◽  
Carbon Uptake ◽  
The Past

&lt;p&gt;South African ecosystems are highly vulnerable to the effects of climate change, such as increasing&amp;#160;temperatures, modifications in rainfall patterns, increasing frequency of extreme weather events and fire, and increased concentration of atmospheric carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;). At the same time, ecosystems are impacted by livestock grazing, cultivation,&amp;#160;fuelwood collection, urbanization and other types of human land use. Climatic and land management factors, such as water availability and grazing intensity, play a dominant role in influencing primary production and carbon fluxes. However, the relative role of those parameters still remains less known in many South African ecosystems. Investigation of the carbon inter-annual variability at dwarf shrub Karoo sites will assist in understanding savanna dynamics and in constraining climate change scenarios as basis for climate adaptation strategies.&amp;#160;&lt;/p&gt;&lt;p&gt;This research is part of the EMSAfrica (Ecosystem Management Support for Climate Change in Southern Africa) project, which aims at producing data and information relevant to land users and land managers such as South African National Parks (SANParks). A particular focus is given on the importance of carbon cycling in degraded vs. intact systems. We investigate the impacts of climate parameters and diverse land management on ecosystem-atmosphere variability of carbon fluxes, latent and sensible energy. Long-term measurements were collected and analyzed from two eddy-covariance towers in the Karoo, Eastern Cape, South Africa. Study areas had almost identical climatic conditions but differ in the intensity of livestock grazing. The first site represents controlled grazing and comprises a diverse balance of dwarf shrubs and grasses, while the second site is degraded through overgrazing in the past (rested for approximately 8 years) and mainly consists of unpalatable grasses and short-lived species. These ecosystems are generally characterized by alternating wet (December to May) and dry seasons (June to November) with the amount and distribution of rain (average 373 mm per year) and soil moisture as the main drivers of carbon fluxes. We observed peak CO&lt;sub&gt;2&lt;/sub&gt; uptake occurring during the wet season (January to April) and a progressive decrease from wet to dry periods being highly controlled by the amount of precipitation. At the end of the observation period (November 2015 &amp;#8211; November 2019), we found that both study sites were considerable carbon sources, but during wet periods 'overgrazed in the past' site had stronger carbon sequestration compared to 'controlled grazing' site. The higher carbon uptake could be an indication that resting of the highly degraded site for a long period may improve carbon uptake in the Karoo ecosystems. Our study shows that CO&lt;sub&gt;2&lt;/sub&gt; dynamics in the Karoo are largely driven by water availability and the effects of grazing intensity on above-ground biomass.&lt;/p&gt;

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

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2680 ◽  
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.

scholarly journals Squalene Found in Alpine Grassland Soils under a Harsh Environment in the Tibetan Plateau, China

Biomolecules ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 154 ◽  
Author(s):  
Xuyang Lu ◽  
Shuqin Ma ◽  
Youchao Chen ◽  
Degyi Yangzom ◽  
Hongmao Jiang
Keyword(s):  
Tibetan Plateau ◽  
Relative Abundance ◽  
Alpine Grassland ◽  
Gas Chromatography Mass Spectrometry ◽  
The Tibetan Plateau ◽  
Alpine Grasslands ◽  
Grassland Soils ◽  
Pyrolysis Gas ◽  
Microbial Characteristics ◽  
Microbial Biosynthesis

Squalene is found in a large number of plants, animals, and microorganisms, as well as other sources, playing an important role as an intermediate in sterol biosynthesis. It is used widely in the food, cosmetics, and medicine industries because of its antioxidant, antistatic, and anti-carcinogenic properties. A higher natural squalene component of lipids is usually reported as being isolated to organisms living in harsh environments. In the Tibetan Plateau, which is characterized by high altitude, strong solar radiation, drought, low temperatures, and thin air, the squalene component was identified in five alpine grasslands soils using the pyrolysis gas chromatography–mass spectrometry (Py-GC/MS) technique. The relative abundance of squalene ranged from 0.93% to 10.66% in soils from the five alpine grasslands, with the highest value found in alpine desert and the lowest in alpine meadow. Furthermore, the relative abundance of squalene in alpine grassland soils was significantly negatively associated with soil chemical/microbial characteristics. These results indicate that the extreme environmental conditions of the Tibetan Plateau may stimulate the microbial biosynthesis of squalene, and the harsher the environment, the higher the relative abundance of soil squalene.

scholarly journals Increased precipitation accelerates soil organic matter turnover associated with microbial community composition in topsoil of alpine grassland on the eastern Tibetan Plateau

2017 ◽  
Vol 63 (10) ◽  
pp. 811-821 ◽  
Author(s):  
Conghai Han ◽  
Zongli Wang ◽  
Guicai Si ◽  
Tianzhu Lei ◽  
Yanli Yuan ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Tibetan Plateau ◽  
Microbial Communities ◽  
Turnover Rate ◽  
Soil Microbial Communities ◽  
Alpine Grassland ◽  
The Tibetan Plateau ◽  
Soil Organic Matter Turnover

Large quantities of carbon are stored in alpine grassland of the Tibetan Plateau, which is extremely sensitive to climate change. However, it remains unclear whether soil organic matter (SOM) in different layers responds to climate change analogously, and whether microbial communities play vital roles in SOM turnover of topsoil. In this study we measured and collected SOM turnover by the 14C method in alpine grassland to test climatic effects on SOM turnover in soil profiles. Edaphic properties and microbial communities in the northwestern Qinghai Lake were investigated to explore microbial influence on SOM turnover. SOM turnover in surface soil (0–10 cm) was more sensitive to precipitation than that in subsurface layers (10–40 cm). Precipitation also imposed stronger effects on the composition of microbial communities in the surface layer than that in deeper soil. At the 5–10 cm depth, the SOM turnover rate was positively associated with the bacteria/fungi biomass ratio and the relative abundance of Acidobacteria, both of which are related to precipitation. Partial correlation analysis suggested that increased precipitation could accelerate the SOM turnover rate in topsoil by structuring soil microbial communities. Conversely, carbon stored in deep soil would be barely affected by climate change. Our results provide valuable insights into the dynamics and storage of SOM in alpine grasslands under future climate scenarios.

scholarly journals Market Costs and Financing Options for Grassland Carbon Sequestration: Empirical and Modelling Evidence From Qinghai, China

2021 ◽  
Vol 9 ◽  
Author(s):  
Andreas Wilkes ◽  
Shiping Wang ◽  
Leslie Lipper ◽  
Xiaofeng Chang
Keyword(s):  
Climate Change ◽  
Carbon Sequestration ◽  
Grazing Intensity ◽  
Grassland Management ◽  
Cash Flows ◽  
Economic Benefits ◽  
The Tibetan Plateau ◽  
Degraded Land ◽  
Financing Costs ◽  
Carbon Project

Asia’s grasslands provide livelihoods for some of the region’s poorest people. Widespread grassland degradation reduces the resilience and returns to herding livelihoods. Reversing degradation and conserving grasslands could not only improve herders’ situation, but also make a huge contribution to mitigating climate change by sequestering carbon in soils. However, the means for reaching each of these objectives are not necessarily the same. To realize this potentially huge dual livelihood/climate change mitigation outcome from improved grassland management, it is necessary to have detailed understanding of the processes involved in securing better livelihoods and sequestering carbon. Based on household surveys on the Tibetan Plateau and modeling results, this study estimates economic and market costs of grassland carbon sequestration, and analyzes the implications of household and carbon project cash flows for the design of financing options. Five scenarios are modeled involving cultivation of grass on severely degraded grassland (all scenarios) and reduced grazing intensity on less degraded land, which requires destocking by 29, 38, 47, 56, and 65% in each scenario). Modeling results suggest that economic benefits for herders are positive at low levels of destocking, and negative at high levels of destocking, but initial investments and opportunity costs are significant barriers to adoption for households in all destocking scenarios. Existing rural finance products are not suitable for herders to finance the necessary investments. Market costs–the cost at which transactions between herders and carbon project developers are feasible–depend on the scale of project implementation but are high compared to recent carbon market prices. Large initial investments increase project developers’ financing costs and risk, so co-financing of initial investments by government would be necessary. Therefore, public policies to support grassland carbon sequestration should consider the potential roles of a range of financial instruments.

scholarly journals Soil Bacterial Communities and Diversity in Alpine Grasslands on the Tibetan Plateau Based on 16S rRNA Gene Sequencing

2021 ◽  
Vol 9 ◽  
Author(s):  
Hongmao Jiang ◽  
Youchao Chen ◽  
Yang Hu ◽  
Ziwei Wang ◽  
Xuyang Lu
Keyword(s):  
Tibetan Plateau ◽  
Bacterial Communities ◽  
Soil Bacteria ◽  
Alpine Grassland ◽  
Rrna Gene ◽  
The Tibetan Plateau ◽  
Alpine Grasslands ◽  
Soil Bacterial Communities ◽  
Soil Bacterial ◽  
Grassland Types

The Tibetan Plateau, widely known as the world’s “Third Pole,” has gained extensive attention due to its susceptibility to climate change. Alpine grasslands are the dominant ecosystem on the Tibetan Plateau, albeit little is known about the microbial community and diversity among different alpine grassland types. Here, soil bacterial composition and diversity in the upper soils of five alpine grassland ecosystems, alpine meadow (AM), alpine steppe (AS), alpine meadow steppe (AMS), alpine desert (AD), and alpine desert steppe (ADS), were investigated based on the 16S rRNA gene sequencing technology. Actinobacteria (46.12%) and Proteobacteria (29.67%) were the two dominant soil bacteria at the phylum level in alpine grasslands. There were significant differences in the relative abundance at the genus level among the five different grassland types, especially for the Rubrobacter, Solirubrobacter, Pseudonocardia, Gaiella, Haliangium, and Geodermatophilus. Six alpha diversity indices were calculated based on the operational taxonomic units (OTUs), including Good’s coverage index, phylogenetic diversity (PD) whole tree index, Chao1 index, observed species index, Shannon index, and Simpson index. The Good’s coverage index value was around 0.97 for all the grassland types in the study area, meaning the soil bacteria samplings sequenced sufficiently. No statistically significant difference was shown in other diversity indices’ value, indicating the similar richness and evenness of soil bacteria in these alpine grasslands. The beta diversity, represented by Bray–Curtis dissimilarity and the non-metric multidimensional scaling (NMDS), showed that OTUs were clustered within alpine grasslands, indicating a clear separation of soil bacterial communities. In addition, soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), pH, and soil water content (SWC) were closely related to the variations in soil bacterial compositions. These results indicated that soil bacterial taxonomic compositions were similar, while soil bacterial community structures were different among the five alpine grassland types. The environmental conditions, including SOM, TN, TP, pH, and SWC, might influence the soil bacterial communities on the Tibetan Plateau.

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