Change in drought conditions and its impacts on vegetation growth over the Tibetan Plateau

The Tibetan Plateau, the highest plateau in the world, has experienced strong climate warming during the last few decades. The greater increase of temperature at higher elevations may have strong impacts on the vertical movement of vegetation activities on the plateau. Although satellite-based observations have explored this issue, these observations were normally provided by the coarse satellite data with a spatial resolution of more than hundreds of meters (e.g., GIMMS and MODIS), which could lead to serious mixed-pixel effects in the analyses. In this study, we employed the medium-spatial-resolution Landsat NDVI data (30 m) during 1990–2019 and investigated the relationship between temperature and the elevation-dependent vegetation changes in six mountainous regions on the Tibetan Plateau. Particularly, we focused on the elevational movement of the vegetation greenness isoline to clarify whether the vegetation greenness isoline moves upward during the past three decades because of climate warming. Results show that vegetation greening occurred in all six mountainous regions during the last three decades. Increasing temperatures caused the upward movement of greenness isoline at the middle and high elevations (>4000 m) but led to the downward movement at lower elevations for the six mountainous regions except for Nyainqentanglha. Furthermore, the temperature sensitivity of greenness isoline movement changes from the positive value to negative value by decreasing elevations, suggesting that vegetation growth on the plateau is strongly regulated by other factors such as water availability. As a result, the greenness isoline showed upward movement with the increase of temperature for about 59% pixels. Moreover, the greenness isoline movement increased with the slope angles over the six mountainous regions, suggesting the influence of terrain effects on the vegetation activities. Our analyses improve understandings of the diverse response of elevation-dependent vegetation activities on the Tibetan Plateau.

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Spatial heterogeneity of changes in vegetation growth and their driving forces based on satellite observations of the Yarlung Zangbo River Basin in the Tibetan Plateau

Journal of Hydrology ◽

10.1016/j.jhydrol.2019.04.043 ◽

2019 ◽

Vol 574 ◽

pp. 324-332 ◽

Cited By ~ 14

Author(s):

Wenchao Sun ◽

Yuanyuan Wang ◽

Yongshuo H. Fu ◽

Baolin Xue ◽

Guoqiang Wang ◽

...

Keyword(s):

Tibetan Plateau ◽

Spatial Heterogeneity ◽

River Basin ◽

Driving Forces ◽

Satellite Observations ◽

The Tibetan Plateau ◽

Vegetation Growth ◽

Yarlung Zangbo River

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Increased Chances of Drought in Southeastern Periphery of the Tibetan Plateau Induced by Anthropogenic Warming

Journal of Climate ◽

10.1175/jcli-d-16-0636.1 ◽

2017 ◽

Vol 30 (16) ◽

pp. 6543-6560 ◽

Cited By ~ 15

Author(s):

Shuangmei Ma ◽

Tianjun Zhou ◽

Oliver Angélil ◽

Hideo Shiogama

Keyword(s):

Climate Change ◽

Tibetan Plateau ◽

Climate Models ◽

Hadley Circulation ◽

Warm Pool ◽

Severe Drought ◽

The Tibetan Plateau ◽

Ensemble Simulations ◽

Pacific Warm Pool ◽

Drought Conditions

The southeastern periphery of the Tibetan Plateau (SEPTP) was hit by an extraordinarily severe drought in the autumn of 2009. Overall, the SEPTP has been gripped by a sustained drought for six consecutive years. To better understand the physical causes of these types of severe and frequent droughts and thus to improve their prediction and enhance the ability to adapt, many research efforts have been devoted to the disastrous droughts in the SEPTP. Nonetheless, whether the likelihood and strength of the severe droughts in the SEPTP, such as that in the autumn of 2009, have been affected by anthropogenic climate change remains unknown. This study first identifies the atmospheric circulation regime responsible for the SEPTP droughts and then explores how human-induced climate change has affected the severe droughts in the SEPTP. It is found that the drought conditions in the SEPTP have been driven by the Indian–Pacific warm pool (IPWP) sea surface temperature (SST) through strengthening of the local Hadley circulation and anomalously cyclonic motion over the South China Sea. Ensemble simulations of climate models demonstrate a robust increase in the dry and warm meteorological conditions seen during the 2009 SEPTP autumn drought due to anthropogenic global warming. Given that warming is expected to continue into the future, these results suggest that it is likely that drought conditions will become more common in the SEPTP.

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Soil Macropores Affect the Plant Biomass of Alpine Grassland on the Northeastern Tibetan Plateau

Frontiers in Ecology and Evolution ◽

10.3389/fevo.2021.678186 ◽

2021 ◽

Vol 9 ◽

Author(s):

Ying Zheng ◽

Ning Chen ◽

Can-kun Zhang ◽

Xiao-xue Dong ◽

Chang-ming Zhao

Keyword(s):

Tibetan Plateau ◽

Soil Properties ◽

Plant Biomass ◽

Principal Component ◽

Belowground Biomass ◽

Available Phosphorus ◽

The Tibetan Plateau ◽

Vegetation Growth ◽

Alpine Regions ◽

Growth Space

Macropores are an important part of soil structure. However, in alpine regions, the effects of soil macropores on soil properties and vegetation growth are not clear. We used the X-ray computed tomography (CT) method to obtain 3D images and visualize the distribution and morphology of soil macropores. By combining principal component analysis (PCA) and stepwise regression methods, we studied the relationships between soil macropores and both soil properties and vegetation growth in three types of grassland [alpine degraded steppe (ADS), alpine typical steppe (ATS), and alpine meadow steppe (AMS)] on the Tibetan Plateau. More tubular and continuous macropores occurred in the soil profiles of the AMS and ATS than in that of the ADS. In addition, the AMS soil had the highest macropore number (925 ± 189), while the ADS soil had the lowest macropore number (537 ± 137). PCA and correlation analysis suggested that macroporosity (MP) has significant positive correlations with the contents of soil organic matter, total nitrogen (TN), available phosphorus (AP) and total phosphorus (TP) (p < 0.05). The two parameters with the greatest influence on aboveground and belowground biomass were the shape factor (p < 0.05) and MP (p < 0.05), respectively. However, there was no significant correlation between plant diversity and soil macropores. We conclude that the irregularity of soil macropores restricts the growth space of roots and causes plants to sacrifice the accumulation of aboveground biomass for that of roots to find suitable sites for nutrient and water absorption.

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

Remote Sensing ◽

10.3390/rs13071305 ◽

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.

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The Effects of Asymmetric Diurnal Warming on Vegetation Growth of the Tibetan Plateau over the Past Three Decades

Sustainability ◽

10.3390/su10041103 ◽

2018 ◽

Vol 10 (4) ◽

pp. 1103 ◽

Cited By ~ 15

Author(s):

Haoming Xia ◽

Ainong Li ◽

Gary Feng ◽

Yang Li ◽

Yaochen Qin ◽

...

Keyword(s):

Tibetan Plateau ◽

The Tibetan Plateau ◽

Vegetation Growth ◽

Diurnal Warming ◽

The Past

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Variations in surface roughness of heterogeneous surfaces in the Nagqu area of the Tibetan Plateau

Hydrology and Earth System Sciences ◽

10.5194/hess-25-2915-2021 ◽

2021 ◽

Vol 25 (5) ◽

pp. 2915-2930

Author(s):

Maoshan Li ◽

Xiaoran Liu ◽

Lei Shu ◽

Shucheng Yin ◽

Lingzhi Wang ◽

...

Keyword(s):

Heat Flux ◽

Surface Roughness ◽

Tibetan Plateau ◽

Sensible Heat Flux ◽

Underlying Surface ◽

The Tibetan Plateau ◽

Vegetation Growth ◽

Northern Tibetan Plateau ◽

Roughness Lengths ◽

Aerodynamic Roughness

Abstract. Temporal and spatial variations of the surface aerodynamic roughness lengths (Z0 m) in the Nagqu area of the northern Tibetan Plateau were analysed in 2008, 2010 and 2012 using MODIS satellite data and in situ atmospheric turbulence observations. Surface aerodynamic roughness lengths were calculated from turbulent observations by a single-height ultrasonic anemometer and retrieved by the Massman model. The results showed that Z0 m has an apparent characteristic of seasonal variation. From February to August, Z0 m increased with snow ablation and vegetation growth, and the maximum value reached 4–5 cm at the BJ site. From September to February, Z0 m gradually decreased and reached its minimum values of about 1–2 cm. Snowfall in abnormal years was the main reason for the significantly lower Z0 m compared with that in normal conditions. The underlying surface can be divided into four categories according to the different values of Z0 m: snow and ice, sparse grassland, lush grassland and town. Among them, lush grassland and sparse grassland accounted for 62.49 % and 33.74 %, and they have an annual variation of Z0 m between 1–4 and 2–6 cm, respectively. The two methods were positively correlated, and the retrieved values were lower than the measured results due to the heterogeneity of the underlying surface. These results are substituted into the Noah-MP (multi-parameterisation) model to replace the original parameter design numerical simulation experiment. After replacing the model surface roughness, the sensible heat flux and latent heat flux were simulated with a better diurnal dynamics.

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