The Melting Himalayas: Cascading Effects of Climate Change on Water, Biodiversity, and Livelihoods

Under ongoing climate change, changes in net primary productivity (NPP), a key indicator of vegetation growth and ecosystem functioning, are crucial for understanding regional carbon sequestration, forage supply, and ecosystem stability in alpine grasslands on the Tibetan Plateau (TP). However, it is unclear how the NPP of alpine grasslands (including alpine meadow and steppe) on the TP responds to regional climate change. Based on this, we explored the spatial and temporal variations of alpine grassland NPP and its response to changes in temperature, precipitation, solar radiation, vapor pressure deficit, and wind speed over the past forty-one years by using remotely sensed data, the improved Carnegie-Ames-Stanford Approach (CASA) model, higher-order partial correlation analysis, and the Constraint Lines approach. The results showed that: (1) from 1982 to 2022, the NPP of alpine grasslands on the TP showed a slow growth trend, and its spatial distribution pattern showed a prominent characteristic of "low in the northwest and high in the southeast". The NPP of the alpine meadow is higher, while that of the alpine steppe is relatively lower. (2) The correlation between the NPP of alpine grasslands on the TP and temperature and precipitation is closer than that with solar radiation, vapor pressure deficit, and wind speed. Temperature and precipitation explained 28% and 30% of the variation in NPP of grasslands, and the dominant climatic factors for alpine steppe and alpine meadow were temperature and precipitation, respectively. (3) NPP responses to climatic factors exhibited clear threshold effects, and the optimal climatic conditions differed between alpine meadow and alpine steppe. In particular, alpine meadow reached peak NPP under wetter and warmer conditions than alpine steppe. Alpine steppe NPP began to decline when precipitation exceeded 407.24mm, temperature exceeded -0.19°C, and solar radiation exceeded 5254.79MJ·m-2, whereas alpine meadow NPP began to decrease when precipitation exceeded 697.44mm, temperature exceeded 2.99°C, and solar radiation exceeded 4853.29MJ·m-2.

Alpine meadow and alpine steppe are the two most widely distributed nonzonal vegetation types in the Qinghai-Tibet Plateau. In the context of global climate change, the differences in spatial-temporal variation trends and their responses to climate change are discussed. It is of great significance to reveal the response of the Qinghai-Tibet Plateau to global climate change and the construction of ecological security barriers. This study takes alpine meadow, alpine steppe and the overall vegetation of the Qinghai-Tibet Plateau as the research objects. The normalized difference vegetation index (NDVI) data and meteorological data were used as the data sources between 2000 and 2018. By using the mean value method, threshold method, trend analysis method and correlation analysis method, the spatial and temporal variation trends in the alpine meadow, alpine steppe and the overall vegetation of the Qinghai-Tibet Plateau were compared and analyzed, and their differences in the responses to climate change were discussed. The results showed the following: (1) The growing season length of alpine meadow was 145~289 d, while that of alpine steppe and the overall vegetation of the Qinghai-Tibet Plateau was 161~273 d, and their growing season lengths were significantly shorter than that of alpine meadow. (2) The annual variation trends of the growing season NDVI for the alpine meadow, alpine steppe and the overall vegetation of the Qinghai-Tibet Plateau increased obviously, but their fluctuation range and change rate were significantly different. (3) The overall vegetation improvement in the Qinghai-Tibet Plateau was primarily dominated by alpine steppe and alpine meadow, while the degradation was primarily dominated by alpine meadow. (4) The responses between the growing season NDVI and climatic factors in the alpine meadow, alpine steppe and the overall vegetation of the Qinghai-Tibet Plateau had great spatial heterogeneity in the Qinghai-Tibet Plateau. These findings provide evidence towards understanding the characteristics of the different vegetation types in the Qinghai-Tibet Plateau and their spatial differences in response to climate change.

Different response of alpine meadow and alpine steppe to climatic and anthropogenic disturbance on the Qinghai-Tibetan Plateau

Divergences of soil carbon turnover and regulation in alpine steppes and meadows on the Tibetan Plateau

The biogeographic characteristics of soil microbial biomass stoichiometry homeostasis and also its mechanisms are commonly thought to be key factors for the survival strategies and resource utilization of soil microbes under extreme habitat. In this work, we conducted a 5,000-km transect filed survey in alpine grassland across Qinghai–Tibet Plateau in 2015 to measure soil microbial biomass carbon (MBC) and nitrogen (MBN) across alpine steppe and meadow. Based on the differences of climate and soil conditions between alpine steppe and meadow, the variation coefficient was calculated to investigate the homeostatic degree of MBC to MBN. Furthermore, the “trade-off” model was utilized to deeply distinguish the homeostasis degree of MBC/MBN between alpine steppe and meadow, and the regression analysis was used to explore the variability of trade-off in response to environmental factors in the alpine grassland. The results showed that the coefficient of variation (CV) of MBC/MBN in alpine meadow (CV = 0.4) was lower than alpine steppe (CV = 0.7). According to the trade-off model, microbial turnover activity of soil N relative to soil C increased rapidly and then decreased slightly with soil organic carbon (SOC), soil total nitrogen (STN), and soil water content across alpine meadow. Nevertheless, in alpine steppe, SOC/STN had a positive effect on microbial turnover of soil N. These results suggested that water, heat, and soil nutrients availability were the key factors affecting the C:N stoichiometry homeostasis of soil microbial biomass in Qinghai–Tibet Plateau (QTP)’s alpine grassland. Since the difference of survival strategy of the trade-off demands between soil C and N resulting in different patterns and mechanism, the stoichiometry homeostasis of soil microbial biomass was more stable in alpine meadow than in alpine steppe.

高寒草甸和高寒草原作为青藏高原两种重要植被类型，研究其植被变化与气候变化相关性，有助于为青藏高原两种高寒草地生态系统应对全球气候变化管理提供参考。以位于同纬度的三江源高寒草甸和阿里高寒草原为研究对象，基于植被净初级生产力（Net Primary Productivity，NPP）变化表征植被变化，利用NPP数据和气象数据，分别分析两地2000-2017年植被NPP、降水和气温时空变化差异；利用Sen+Mann-Kendall趋势检验，研究两种高寒草地气候与植被净初级生产力变化趋势；以县域统计年鉴牛羊肉产量表征放牧强度，研究放牧活动对高寒草地植被变化的影响；通过Pearson相关和偏相关分析方法，分别研究降水和气温对两种高寒草地植被NPP变化影响差异。研究结果表明：（1）2000-2017年三江源高寒草甸和阿里高寒草原区年平均气温以0.085℃/a和0.084℃/a的趋势上升，降水以平均每年3.87 mm和2.23 mm的趋势增加，高寒草甸区变暖变湿速率较高寒草原区快。（2）三江源高寒草甸和阿里高寒草原植被NPP均呈现由东南向西北逐渐降低空间格局；2000-2017年高寒草甸区57.7%植被NPP呈现上升趋势，而高寒草原区50.96%植被NPP呈现上升趋势，高寒草甸植被NPP增长趋势较高寒草原明显。（3）三江源高寒草甸和阿里高寒草原两种草地植被变化受放牧影响不大，受气候变化影响较大。（4）三江源高寒草甸大部分植被NPP增长与气温呈显著正相关而与降水呈显著负相关，高寒草甸植被NPP主要受温度调控，而阿里高寒草原植被NPP受降水和温度的双重调控。;Alpine meadow and alpine steppe are two important vegetation types on the Qinghai-Tibet Plateau. Studying the correlation between vegetation change and climate change in alpine meadow and alpine steppe is helpful to provide reference for the management of the two alpine grassland ecosystems on the Qinghai-Tibet Plateau in response to global climate change. In this study, the alpine meadow of the Three-River Headwaters Region and the alpine steppe of Ali located in the same latitude were taken as the research objects. Vegetation changes were characterized based on the changes of Net Primary Productivity (NPP) of vegetation. Based on NPP data and meteorological data, the spatial and temporal variations of NPP, precipitation and air temperature between 2000 and 2017 were analyzed. Sen+ Mann-Kendall trend test was used to study the change trend of climate and vegetation net primary productivity in two alpine grasslands. The effects of grazing activities on the vegetation change of alpine grassland were studied by using the yield of beef and mutton in county statistical yearbooks. Through Pearson correlation and partial correlation analysis, the variation trend of precipitation and air temperature on vegetation NPP and the difference of precipitation and air temperature on NPP of two alpine grasslands were studied respectively. The results show that:(1) from 2000 to 2017, the annual average temperature in Three-River Headwaters Region alpine meadow and Ali alpine steppe increased at 0.085℃/a and 0.084℃/a, and the annual average precipitation increased at 3.87 mm and 2.23 mm, respectively. The warming and wetness rate in the alpine meadow was faster than that in the alpine steppe. (2) The NPP of the alpine meadow in the Three-River Headwaters Region and the alpine steppe in Ali showed a decreasing spatial pattern from southeast to northwest. From 2000 to 2017, the NPP of 57.7% of alpine meadow vegetation presented an upward trend, while that of 50.96% of alpine steppe vegetation showed an upward trend. The NPP of alpine meadow vegetation increased more obviously than that of alpine steppe. (3) The alpine meadow in the Three-River Headwaters Region and the alpine steppe in Ali region were less affected by grazing and more affected by climate change. (4) The NPP growth of most alpine meadow vegetation in the Three-River Headwaters Region was significantly positively correlated with air temperature and negatively correlated with precipitation. The NPP of alpine meadow vegetation was mainly regulated by temperature, while the NPP of alpine steppe vegetation in the Ali region was controlled by both precipitation and temperature.

Disentangling the assembly mechanisms of bacterial communities in a transition zone between the alpine steppe and alpine meadow ecosystems on the Tibetan Plateau

The alpine grasslands account for approximately 54.5% of the total carbon in China’s grasslands, and carbohydrate-active enzymes (CAZymes) play key roles in the turnover of carbon. However, the variation and factors influencing gene-encoding enzymes for plant- and microbial-derived carbon decomposition in alpine steppes and alpine meadows remain unclear. Here, the trends in microbial carbohydrate-active enzymes (CAZymes) and their responses to the decomposition of biomass of different origins were studied using metagenomics in the alpine steppes and alpine meadows on the Tibetan Plateau. Our results revealed the abundance of GTs and CBMs was higher in the alpine steppes than in the alpine meadows, whereas AAs were higher in the alpine steppes than in the alpine meadows. Soil properties (i.e., soil water content, soil ammonium nitrogen, and nitrate nitrogen) highly related to CAZyme genes (GTs, CBMs, and AAs) showed an abundant pattern between the alpine steppes and alpine meadows. Moreover, our results indicated that the relative abundance of genes encoding CAZymes involved in the decomposition of plant- (indicated by cellulose, hemicellulose, and lignin) and fungal-derived carbon (indicated by chitin and glucans) was higher by 8.7% and 10.1%, respectively, in the alpine steppes than in the alpine meadows, whereas bacterial-derived carbon (indicated by peptidoglycan) was lower by 7.9% in the alpine steppes than in the alpine meadows. Soil water content (SWC), nitrate nitrogen (NO3−), and pH influenced on the abundance of CAZyme genes involved in the decomposition of plant-, fungal-, bacterial-derived carbon. In addition, the dominant microbial phyla (Actinobacteria, Protebacteria, and Acidobacteria) mineralized carbon sources from plant- and microbial-derived carbon through their corresponding CAZyme families. In conclusion, our study compared plant- and microbial-derived carbon decomposition potentials and influencing factors to illustrate the contribution of dead biomass to carbon accumulation in alpine grasslands.

The responses of soil microbes to climatic and anthropological factors in the Tibetan grasslands

Alpine meadow and alpine steppe plant-soil network in Qinghai-Tibet Plateau, China

PDF HTML阅读 XML下载 导出引用 引用提醒 青海省高寒草地土壤无机碳储量空间分异特征 DOI: 10.5846/stxb201301250156 作者: 作者单位: 中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（41030105）；中国科学院战略性先导科技专项（XDA05050404）（固碳现状、速率、机制和潜力）项目 The variation feature of soil inorganic carbon storage in alpine grassland in Qinghai province Author: Affiliation: Northwest Institute of Plateau biology, Chinese Academy of Sciences,,,,,,,,Northwest Institute of Plateau biology, Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以青海省主要高寒草地类型即温性草原、高寒草原、草甸草原以及高寒草甸为研究对象，进行其土壤无机碳（SIC）储量分异特征研究。结果表明，在取样剖面内四类草地SIC储量依次为温性草原 >高寒草原 >草甸草原 >高寒草甸，其值分别为16.51、16.48 、3.37 kgC/m2和0.12 kgC/m2，温性草原与高寒草原土壤是高寒草地无机碳的主要储蓄库。温性草原与高寒草原50-100cm SIC储量分别占0-100cm总储量的60.2%和 51.8%，而草甸草原与高寒草甸30-50cmSIC储量分别占0-50cm总储量的50.1%和55.8%，说明土体下部是高寒草地无机碳储蓄的主要场所。四类草地SIC含量随土层深度的变化过程各异，其碳酸钙富集层与野外剖面调查所得碳酸钙盐酸泡沫检验结果相吻合。SIC储量与土壤容重和土壤pH均呈显著正相关关系，与地下生物量呈显著负相关关系。 Abstract:The warm steppe, alpine steppe, alpine meadow steppe and alpine meadow are the main grassland types which widely distribute in Qinghai-Tibetan plateau. It's widely distribution and diverse development environments make it play an important role in the ecosystem: supporting regional economic development, guaranteeing water conservation of the plateau, maintaining biodiversity, fixation of carbon, etc. A quantitative survey of the variation feature of soil inorganic carbon(SIC)stored in warm steppe, alpine steppe, alpine meadow steppe and alpine meadow were carried out in Qinghai province. Results showed that the total storage of SIC in the four types grassland appeared to be warm steppe> alpine steppe> meadow steppe> alpine meadow, and the values were 16.51kgC/m2,16.48 kgC/m2,3.37 kgC/m2 and 0.12 kgC/m2, respectively. One-Way ANOVA analysis indicated that warm steppe、alpine steppe had a significant difference with alpine meadow steppe and alpine meadow(P < 0.05)while no significant difference between warm steppe and alpine steppe as well as alpine meadow steppe and alpine meadow(P > 0.05). The warm steppe and alpine steppe grassland are the main reserve pool of SIC in alpine grassland. The SIC stored in 50-100cm accounted separately for 60.2% and 51.8% of the total storage in 0-100cm profile of the warm steppe and alpine steppe, while in alpine meadow steppe and alpine meadow, it occupied 50.1% and 55.8% respectively of the 30-50cm in 0-50cm. Deep soil layer is the main place of SIC storing in alpine grassland. Soil depth has an important effect on SIC storage in alpine grassland. In 0-50cm depth of the soil, SIC storing in the four types grassland were 6.57 kgC/m2,7.95 kgC/m2,3.37 kgC/m2 and 0.12 kgC/m2, respectively. The change of SIC content with soil depth were different in the four types grassland. It increased with soil depth in warm steppe and alpine meadow steppe, but increased at first then decreased in alpine meadow steppe and alpine meadow. The calcium carbonate enrichment layer in the soil tallied with the foam examination by hydrochloric acid in the soil profile investigation. The calcium carbonate accumulate in the deep soil of steppe, but enrich rather shallow in meadow. SIC storage in the four types of grassland had a significantly positive correlation with soil bulk density and pH value but a significantly negative correlation with underground biomass. The SIC storage increased from south to north in the grassland of Qinghai province and the total SIC storage of the four types grassland reached 1.34 Pg in the profile. The SIC storage in the alpine meadow is very small and it mainly distributed in the south of Qinghai province. Warm steppe which has the largest SIC storage mainly distributed nearby the Qinghai Lake. Climate change and human activity may affect the capacity and distribution of the carbon storage which would bring the ecological risk to the inorganic carbon fixation. 参考文献 相似文献 引证文献

Currently, grazing exclosure is one of the most important grassland management measures for restoring all types of degraded alpine grassland in the Qinghai–Tibetan Plateau (QTP). The most widely distributed grassland ecosystems across the northeastern QTP are the alpine meadow (AM), alpine meadow steppe (AMS), and alpine steppe (AS). However, whether the impacts of fencing on vegetation characteristics and soil properties vary among different grassland types remains poorly understood despite that numerous individual studies have been conducted. This study investigated the vegetation characteristics and soil properties in fenced and grazed AM, AMS, and AS in the northeastern QTP. Grazing exclosure significantly increased the vegetation coverage and Shannon–Wiener diversity index in all the three grasslands. Plant species richness was significantly increased in AM, but there were no significant changes in AMS and AS. Aboveground biomass was significantly increased in AMS and AS but not significant in AM. Increase in the percentage of high-quality forage grasses was only observed in AMS. Fencing significantly decreased the soil bulk density (BD) and significantly increased soil organic carbon (SOC) and total nitrogen at a depth of 0–50 cm in AMS and AS but had no effect in AM. Our results indicate that the use of fencing for restoring degraded AM might not achieve the same expected results as in AS and AMS on the QTP.

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 &lt;0.0001), alpine meadow ( R 2 =0.4, P &lt;0.0001), and all samples across alpine grassland ( R 2 =0.52, P &lt;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 &lt;0.0001) and altitude ( R 2 =0.48, P &lt;0.0001) have positive and negative effects on aboveground net primary production, and a similar relationship exists with diversity ( R 2 =0.44, P &lt;0.0001 and R 2 =0.3, P &lt;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.

The changes in vegetation composition and plant diversity of three different alpine ecosystems: alpine meadow, alpine steppe and alpine desert, impacted by different levels of degradation (healthy, lightly degraded and moderately degraded) were examined across a large-scale transect on the Qinghai-Tibet Plateau. The importance values of the dominant species and levels of diversity were measured by various vegetation indices. The plant composition of the alpine meadow and alpine steppe ecosystems was more stable and appeared more resistant to disturbance than that of the alpine desert ecosystem.

Quantifying the impact of climate change and vegetation phenology on ecosystem productivity in the alpine grasslands of the Tibetan Plateau (TP) is essential for assessing carbon balance dynamics at regional and global scales. However, the relative contributions of climate change and phenological change to vegetation productivity across various grassland types remain indistinguishable. This study examined the effects of climate change and phenological change on net primary productivity (NPP) in the alpine meadow and alpine steppe ecosystems of the TP from 2001 to 2020. The results revealed that (1) NPP exhibited a positive correlation with vegetation phenology, particularly with an extended growing season length and an earlier start of the growing season. Among the phenological variables studied, changes in the start of the growing season had the strongest influence on NPP variations in both alpine meadows and alpine steppes. (2) NPP displayed a positive correlation with annual precipitation and annual temperature, with changes in annual precipitation playing a dominant role in shaping NPP variations in alpine steppes. (3) NPP showed a negative correlation with annual radiation, and the impact of radiation changes on NPP variations was comparable to that of precipitation or temperature in both alpine meadows and alpine steppes. (4) Climate change exerted a stronger impact on NPP than phenological change in alpine steppes, while NPP was jointly affected by climate change and phenological change in alpine meadows. Our findings indicated that the relative effects of climate change and phenological change on vegetation productivity vary across different grassland types on the TP.