Spatial-Temporal Patterns and Controls of Evapotranspiration across the Tibetan Plateau (2000–2012)

Abstract

Evapotranspiration (ET) is a key factor to further our understanding of climate change processes, especially on the Tibetan Plateau, which is sensitive to global change. Herein, the spatial patterns of ET are examined, and the effects of environmental factors on ET at different scales are explored from the years 2000 to 2012. The results indicated that a steady trend in ET was detected over the past decade. Meanwhile, the spatial distribution shows an increase of ET from the northwest to the southeast, and the rate of change in ET is lower in the middle part of the Tibetan Plateau. Besides, the positive effect of radiation on ET existed mainly in the southwest. Based on the environment gradient transects, the ET had positive correlations with temperature ( > 0.85, < 0.0001), precipitation (R > 0.89, p < 0.0001), and NDVI (R > 0.75, p < 0.0001), but a negative correlation between ET and radiation (R = 0.76, p < 0.0001) was observed. We also found that the relationships between environmental factors and ET differed in the different grassland ecosystems, which indicated that vegetation type is one factor that can affect ET. Generally, the results indicate that ET can serve as a valuable ecological indicator.

Spatial and Temporal Patterns of the Extreme Precipitation across the Tibetan Plateau (1986–2015)

“…In contrast, the order of decline for the other precipitation indices moved in the opposite direction: Forest, alpine meadow, alpine steppe, and desert steppe ( Figures 6 and 7). Previous research verified significant positive correlations between precipitation and evapotranspiration (ET) [35,65,66], and normalized difference vegetation index (NDVI) [67]. Forests are distributed mainly in the western Sichuan Province, southeast Tibetan, and the northern Yunnan Province with deep ravine regions [35].…”

“…Previous research verified significant positive correlations between precipitation and evapotranspiration (ET) [35,65,66], and normalized difference vegetation index (NDVI) [67]. Forests are distributed mainly in the western Sichuan Province, southeast Tibetan, and the northern Yunnan Province with deep ravine regions [35]. These areas have lush vegetation, more precipitation, and more ET than other ecosystems across the Tibetan Plateau [68], and as for ET, it has a growth gradient from the southeast to northwest, and it is similar to precipitation ( Figure 5).…”

“…A decrease in EASM and SASM led to a decline in precipitation from 1975 to 2014 [14]. In addition, one possible cause of the decreasing precipitation and precipitation days is the decreasing trends of evapotranspiration (ET) in southeastern region of the Tibetan Plateau [35]. The alpine steppe and desert steppe are mainly located in areas controlled by the westerly belt.…”

“…Furthermore, most of the study area is dominated by alpine steppes and alpine meadows, the alpine steppe is mainly distributed in northern Tibet and the eastern and western ends of Qinghai Province, which covers 0.71 million km 2 ; the alpine meadow is widely distributed widely in Tibet, Sichuan Province and Qinghai Province, with an area of 0.65 million km 2 [28]. Furthermore, the forest area mainly occurs in the south and southeast end of the Tibetan Plateau and large areas of bare land, such as desert steppes are found in the northwest (Figure 1) [35].…”

Selected Environmental Assessment Model and Spatial Analysis Method to Explain Correlations in Environmental and Socio-Economic Data with Possible Application for Explaining the State of the Ecosystem

“…The southern end of the Hu Line is an ecologically fragile area that is also a hot spot for economic development and population growth. Located in Sichuan and Yunnan provinces, the southeastern part of the Tibetan Plateau is fragile and vulnerable to climate change [35]. Sichuan Basin is in the northeastern part of the study area, where the terrain is relatively flat and the soil is fertile.…”