scholarly journals Variation of Net Primary Production and Its Correlation with Climate Change and Anthropogenic Activities over the Tibetan Plateau

2018 ◽  
Vol 10 (9) ◽  
pp. 1352 ◽  
Author(s):  
Zhaohui Luo ◽  
Wenchen Wu ◽  
Xijun Yu ◽  
Qingmei Song ◽  
Jian Yang ◽  
...  
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Climatic Factors ◽  
Anthropogenic Activities ◽  
Mean Value ◽  
Mean Annual Temperature ◽  
The Tibetan Plateau ◽  
Casa Model ◽  
Negative Effect ◽  
Cumulative Precipitation

Grasslands in the Tibetan Plateau are claimed to be sensitive and vulnerable to climate change and anthropogenic activities. Quantifying the impacts of climate change and anthropogenic activities on grassland growth is an essential step for developing sustainable grassland ecosystem management strategies under the background of climate change and increasing anthropogenic activities occurring in the plateau. Net primary productivity (NPP) is one of the key components in the carbon cycle of terrestrial ecosystems, and can serve an important role in the assessment of vegetation growth. In this study, a modified Carnegie–Ames–Stanford Approach (CASA) model, which considers remote sensing information for the estimation of the water stress coefficient and time-lag effects of climatic factors on NPP simulation, was applied to simulate NPP in the Tibetan Plateau from 2001 to 2015. Then, the spatiotemporal variations of NPP and its correlation with climatic factors and anthropogenic activities were analyzed. The results showed that the mean values of NPP were 0.18 kg∙C∙m−2∙a−1 and 0.16 kg∙C∙m−2∙a−1 for the original CASA model and modified CASA model, respectively. The modified CASA model performed well in estimating NPP compared with field-observed data, with root mean square error (RMSE) and mean absolute error (MAE) of 0.13 kg∙C∙m−2∙a−1 and 0.10 kg∙C∙m−2∙a−1, respectively. Relative RMSE and MAE decreased by 45.8% and 44.4%, respectively, compared to the original CASA model. The variation of NPP showed gradients decreasing from southeast to northwest spatially, and displayed an overall decreasing trend for the study area temporally, with a mean value of −0.02 × 10−2 kg∙C∙m−2∙a−1 due to climate change and increasing anthropogenic activities (i.e., land use and land cover change). Generally, 54% and 89% of the total pixels displayed a negative relationship between NPP and mean annual temperature, as well as annual cumulative precipitation, respectively, with average values of –0.0003 (kg∙C∙m−2 a−1)/°C and −0.254 (g∙C∙m−2∙a−1)/mm for mean annual temperature and annual cumulative precipitation, respectively. Additionally, about 68% of the total pixels displayed a positive relationship between annual cumulative solar radiation and NPP, with a mean value of 0.038 (g∙C∙m−2·a−1)/(MJ m−2). Anthropogenic activities had a negative effect on NPP variation, and it was larger than that of climate change, implying that human intervention plays a critical role in mitigating the degenerating ecosystem. In terms of human intervention, ecological destruction has a significantly negative effect on the NPP trend, and the absolute value was larger than that of ecological restoration, which has a significantly positive effect on NPP the trend. Our results indicate that ecological destruction should be paid more attention, and ecological restoration should be conducted to mitigate the overall decreasing trend of NPP in the plateau.

scholarly journals Contrasting Evolution Patterns of Endorheic and Exorheic Lakes on the Central Tibetan Plateau and Climate Cause Analysis during 1988–2017

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1962
Author(s):  
Zhilong Zhao ◽  
Yue Zhang ◽  
Zengzeng Hu ◽  
Xuanhua Nie
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Climatic Factors ◽  
Global Climate ◽  
Rapid Expansion ◽  
Annual Precipitation ◽  
The Tibetan Plateau ◽  
Lake Area ◽  
Climate Change Research ◽  
Mean Temperature

The alpine lakes on the Tibetan Plateau (TP) are indicators of climate change. The assessment of lake dynamics on the TP is an important component of global climate change research. With a focus on lakes in the 33° N zone of the central TP, this study investigates the temporal evolution patterns of the lake areas of different types of lakes, i.e., non-glacier-fed endorheic lakes and non-glacier-fed exorheic lakes, during 1988–2017, and examines their relationship with changes in climatic factors. From 1988 to 2017, two endorheic lakes (Lake Yagenco and Lake Zhamcomaqiong) in the study area expanded significantly, i.e., by more than 50%. Over the same period, two exorheic lakes within the study area also exhibited spatio-temporal variability: Lake Gaeencuonama increased by 5.48%, and the change in Lake Zhamuco was not significant. The 2000s was a period of rapid expansion of both the closed lakes (endorheic lakes) and open lakes (exorheic lakes) in the study area. However, the endorheic lakes maintained the increase in lake area after the period of rapid expansion, while the exorheic lakes decreased after significant expansion. During 1988–2017, the annual mean temperature significantly increased at a rate of 0.04 °C/a, while the annual precipitation slightly increased at a rate of 2.23 mm/a. Furthermore, the annual precipitation significantly increased at a rate of 14.28 mm/a during 1995–2008. The results of this study demonstrate that the change in precipitation was responsible for the observed changes in the lake areas of the two exorheic lakes within the study area, while the changes in the lake areas of the two endorheic lakes were more sensitive to the annual mean temperature between 1988 and 2017. Given the importance of lakes to the TP, these are not trivial issues, and we now need accelerated research based on long-term and continuous remote sensing data.

scholarly journals Chemical Weathering of the Southern Tibetan Plateau: Study the Geochemical Weathering Indices in the Top Soils

2020 ◽  
Author(s):  
Xiaoyan Yang ◽  
Juzhi Hou ◽  
Feixue San
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Chemical Weathering ◽  
Regional Climate ◽  
Lacustrine Sediment ◽  
Mean Annual Temperature ◽  
The Tibetan Plateau ◽  
Climate Condition ◽  
Weathering Indices ◽  
Southern Tibetan Plateau

Abstract Continental chemical weathering has been suggested to affect the concentration of atmospheric carbon dioxide that influences global climate change at different time scales. Various indices for chemical weathering have been adopted to investigate past change in chemical weathering intensity and climate change on oceanic and lacustrine sediment archives. The reliability of the chemical weathering indices has been questioned as most sediments likely originate from multiple types of bedrock that may experience various degrees of chemical weathering and can thus be reliably robust indicators of climate and paleoclimate. Here we present Sr-type (e.g. Rb/Sr Sr/Ba) and Na-type (e.g. CIA CIW PIA CPA) chemical weathering indices for top soils across the southern Tibetan Plateau to discuss the chemical weathering characteristic in the Tibetan Plateau and to examine their response to regional climate variation. The results of chemical indices and the A-CN-K ternary plot show that the southern Tibetan Plateau is under the carbonate control of the primary chemical weathering stage with the cold-dry climate. Correlation analyses show shat Sr-type indices co-vary with mean annual temperature and annual precipitation while Na-type indices show little consistence with regional climate. The climate condition is the dominant control of Sr-type indices of top soils in the study area and the bedrock may be the dominant control for the Na-type indices. We also compared the corresponding indices at a Holocene lacustrine sediment profile in the Qaidam Basin in the northeast Tibetan Plateau with regional climatic records which strongly supports our observation in the top soils. The results of the study suggest that for the relative cold and dry climate in Tibetan Plateau the Sr-type indices are more sensitive to climate condition than Na-type indices. This suggests that the Sr-type indices are likely more suitable than Na-type indices to reflect the change of climate on the Tibetan Plateau. Caution should be taken for using the Na-type indices for reconstructing the past change in climate for the study area.

scholarly journals Changing Pattern of Water Level Trends in Eurasian Endorheic Lakes as a Response to the Recent Climate Variability

2021 ◽  
Vol 13 (18) ◽  
pp. 3705
Author(s):  
Xin Zhang ◽  
Abilgazi Kurbaniyazov ◽  
Georgiy Kirillin
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Central Asia ◽  
Climatic Factors ◽  
Hydrological Regime ◽  
Water Levels ◽  
The Tibetan Plateau ◽  
Lake Levels ◽  
Mongolian Plateau ◽  
Recent Climate

Lake level is a sensitive integral indicator of climate change on regional scales, especially in enclosed endorheic basins. Eurasia contains the largest endorheic zone with several large terminal lakes, whose water levels recently underwent remarkable variations. To address the patterns of these variations and their links to the climate change, we investigated the variability of levels in 15 lakes of three neighboring endorheic regions—Central Asia, Tibetan Plateau, and Mongolian Plateau. Satellite altimetry revealed a heterogeneous pattern among the regions during 1992–2018: lake levels increased significantly in Central Asia and the Tibetan Plateau but decreased on the Mongolian Plateau. The shifts to the increasing trend were detected since 1997 in Central Asia, since 1998 in the southern part of the Tibetan Plateau, and since 2005 in its northern part. The shift in air temperatures around 1997 and the precipitation shifts around 1998 and 2004 contributed to the trend’s turning points, with precipitation being the major contributor to the heterogeneous pattern of lake levels. Our findings reveal the linkage of the heterogeneous pattern of lake levels to climatic factors in the endorheic basins, providing a further understanding of the hydrological regime in the Eurasian endorheic zone and its sensitivity to climate change.

scholarly journals Precipitation Drives the NDVI Distribution on the Tibetan Plateau While High Warming Rates May Intensify Its Ecological Droughts

2021 ◽  
Vol 13 (7) ◽  
pp. 1305
Author(s):  
Kewei Jiao ◽  
Jiangbo Gao ◽  
Zhihua Liu
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Vegetation Cover ◽  
Climatic Factors ◽  
Dominant Role ◽  
Climatic Variability ◽  
The Tibetan Plateau ◽  
Vegetation Growth ◽  
Semiarid Regions ◽  
Arid And Semiarid

Climate change has significantly affected the ecosystem of the Tibetan Plateau. There, temperature rises and altered precipitation patterns have led to notable changes in its vegetation growth processes and vegetation cover features. Yet current research still pays relatively little attention to the regional climatic determinants and response patterns of such vegetation dynamics. In this study, spatial patterns in the response of the normalized difference vegetation index (NDVI) to climate change and its dynamic characteristics during the growing season were examined for the Tibetan Plateau, by using a pixel-scale-based geographically weighted regression (GWR) based on the Global Inventory Modeling and Mapping Studies (GIMMS) NDVI data, as well as data for temperature and moisture indices collected at meteorological stations, for the period 1982–2015. The results show the following. Spatial nonstationary relationships, primarily positive, were found between the NDVI and climatic factors in the Tibetan Plateau. However, warming adversely affected vegetation growth and cover in some arid and semiarid regions of the northeast and west Tibetan Plateau. Additionally, precipitation played a dominant role in the NDVI of the Tibetan Plateau in the largest area (accounting for 39.7% of total area). This suggests that increased moisture conditions considerably facilitated vegetation growth and cover in these regions during the study period. Temperature mainly played a dominant role in the NDVI in some parts of the plateau sub-cold zone and some southeastern regions of the Tibetan Plateau. In particular, the minimum temperature was the dominant driver of NDVI over a larger area than any of the other temperature indices. Furthermore, spatial regressions between NDVI dynamics and climatic variability revealed that a faster warming rate in the arid and semiarid regions impeded vegetation growth through mechanisms such as drought intensification. Moisture variability was found to act as a key factor regulating the extent of vegetation cover on the south Tibetan Plateau.

scholarly journals Dynamic Changes of NDVI in the Growing Season of the Tibetan Plateau During the Past 17 Years and Its Response to Climate Change

2019 ◽  
Vol 16 (18) ◽  
pp. 3452 ◽  
Author(s):  
Xianglin Huang ◽  
Tingbin Zhang ◽  
Guihua Yi ◽  
Dong He ◽  
Xiaobing Zhou ◽  
...  
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Tibetan Plateau ◽  
Time Series Analysis ◽  
Environmental Changes ◽  
Climatic Factors ◽  
Growing Season ◽  
Lag Time ◽  
The Tibetan Plateau ◽  
Series Analysis

The fragile alpine vegetation in the Tibetan Plateau (TP) is very sensitive to environmental changes, making TP one of the hotspots for studying the response of vegetation to climate change. Existing studies lack detailed description of the response of vegetation to different climatic factors using the method of multiple nested time series analysis and the method of grey correlation analysis. In this paper, based on the Normalized Difference Vegetation Index (NDVI) of TP in the growing season calculated from the MOD09A1 data product of Moderate-resolution Imaging Spectroradiometer (MODIS), the method of multiple nested time series analysis is adopted to study the variation trends of NDVI in recent 17 years, and the lag time of NDVI to climate change is analyzed using the method of Grey Relational Analysis (GRA). Finally, the characteristics of temporal and spatial differences of NDVI to different climate factors are summarized. The results indicate that: (1) the spatial distribution of NDVI values in the growing season shows a trend of decreasing from east to west, and from north to south, with a change rate of −0.13/10° E and −0.30/10° N, respectively. (2) From 2001 to 2017, the NDVI in the TP shows a slight trend of increase, with a growth rate of 0.01/10a. (3) The lag time of NDVI to air temperature is not obvious, while the NDVI response lags behind cumulative precipitation by zero to one month, relative humidity by two months, and sunshine duration by three months. (4) The effects of different climatic factors on NDVI are significantly different with the increase of the study period.

Spring phenology outweighed climate change in determining autumn phenology on the Tibetan Plateau

2021 ◽  
Vol 41 (6) ◽  
pp. 3725-3742
Author(s):  
Jie Peng ◽  
Chaoyang Wu ◽  
Xiaoyue Wang ◽  
Linlin Lu
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
The Tibetan Plateau ◽  
Spring Phenology

scholarly journals Strong controls of daily minimum temperature on the autumn photosynthetic phenology of subtropical vegetation in China

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Peixin Ren ◽  
Zelin Liu ◽  
Xiaolu Zhou ◽  
Changhui Peng ◽  
Jingfeng Xiao ◽  
...  
Keyword(s):  
Climate Change ◽  
Minimum Temperature ◽  
Vegetation Index ◽  
Climatic Factors ◽  
Time Lag ◽  
Evergreen Forest ◽  
Maximum Temperature ◽  
Daily Minimum Temperature ◽  
Study Region ◽  
Cumulative Precipitation

Abstract Background Vegetation phenology research has largely focused on temperate deciduous forests, thus limiting our understanding of the response of evergreen vegetation to climate change in tropical and subtropical regions. Results Using satellite solar-induced chlorophyll fluorescence (SIF) and MODIS enhanced vegetation index (EVI) data, we applied two methods to evaluate temporal and spatial patterns of the end of the growing season (EGS) in subtropical vegetation in China, and analyze the dependence of EGS on preseason maximum and minimum temperatures as well as cumulative precipitation. Our results indicated that the averaged EGS derived from the SIF and EVI based on the two methods (dynamic threshold method and derivative method) was later than that derived from gross primary productivity (GPP) based on the eddy covariance technique, and the time-lag for EGSsif and EGSevi was approximately 2 weeks and 4 weeks, respectively. We found that EGS was positively correlated with preseason minimum temperature and cumulative precipitation (accounting for more than 73% and 62% of the study areas, respectively), but negatively correlated with preseason maximum temperature (accounting for more than 59% of the study areas). In addition, EGS was more sensitive to the changes in the preseason minimum temperature than to other climatic factors, and an increase in the preseason minimum temperature significantly delayed the EGS in evergreen forests, shrub and grassland. Conclusions Our results indicated that the SIF outperformed traditional vegetation indices in capturing the autumn photosynthetic phenology of evergreen forest in the subtropical region of China. We found that minimum temperature plays a significant role in determining autumn photosynthetic phenology in the study region. These findings contribute to improving our understanding of the response of the EGS to climate change in subtropical vegetation of China, and provide a new perspective for accurately evaluating the role played by evergreen vegetation in the regional carbon budget.

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