scholarly journals Holocene vegetation and biomass changes on the Tibetan Plateau – a model-pollen data comparison

2011 ◽  
Vol 7 (3) ◽  
pp. 881-901 ◽  
Author(s):  
A. Dallmeyer ◽  
M. Claussen ◽  
U. Herzschuh ◽  
N. Fischer
Keyword(s):  
Tibetan Plateau ◽  
Land Cover ◽  
Land Cover Change ◽  
Vegetation Change ◽  
Climatic Factors ◽  
Warm Season ◽  
Total Biomass ◽  
The Tibetan Plateau ◽  
Vegetation Shift ◽  
Natural Land

Abstract. Results of a transient numerical experiment performed in a coupled atmosphere-ocean-vegetation model with orbital forcing alone are compared to pollen-based vegetation reconstructions covering the last 6000 yr from four representative sites on the Tibetan Plateau. Causes of the vegetation change and consequences of the biomass storage are analysed. In general, simulated and reconstructed vegetation trends at each site are in good agreement. Both methods reveal a general retreat of the biomass-rich vegetation that is particularly manifested in a strong decrease of forests. However, model and reconstructions often differ with regard to the climatic factors causing the vegetation change at each site. The reconstructions primarily identify decreasing summer monsoon precipitation and changes in the temperature of the warm season as the responsible mechanisms for the vegetation shift. In the model, the land cover change mainly originates from differences in warm/cold seasonal temperatures and only to a lesser extent from precipitation changes. According to the model results, the averaged forest fraction on the Plateau shrinks by almost one-third from mid-Holocene (41.4 %) to present-day (28.3 %). Shrubs, whose fraction is quadrupled at present-day (12.3 %), replace most of this forest. Grass fraction increases from 38.1 % during the mid-Holocene to 42.3 % at present-day. This land cover change results in a decrease of living biomass by 0.62 kgC m−2. Total biomass on the Tibetan Plateau decreases by 1.9 kgC m−2, i.e. approx. 6.64 PgC are released due to the natural land cover change.

scholarly journals Holocene vegetation and biomass changes on the Tibetan Plateau – a model-pollen data comparison

2011 ◽  
Vol 7 (2) ◽  
pp. 1073-1111
Author(s):  
A. Dallmeyer ◽  
M. Claussen ◽  
U. Herzschuh ◽  
N. Fischer
Keyword(s):  
Tibetan Plateau ◽  
Land Cover ◽  
Land Cover Change ◽  
Vegetation Change ◽  
Climatic Factors ◽  
Surface Air Temperature ◽  
Total Biomass ◽  
The Tibetan Plateau ◽  
Near Surface ◽  
Vegetation Shift

Abstract. Results of a transient numerical experiment, performed in a coupled atmosphere-ocean-vegetation model with orbital forcing alone, are compared to pollen-based vegetation reconstructions from four representative sites on the Tibetan Plateau, covering the last 6000 years. Causes of the vegetation change and consequences for the biomass storage are analysed. In general, simulated and reconstructed vegetation trends at each site are in good agreement. Both methods reveal a general retreat of the biomass-rich vegetation that is particularly manifested in a strong decrease of forests. However, model and reconstructions differ with regard to the climatic factors causing this vegetation change. The reconstructions primarily identify decreasing summer monsoon precipitation as the responsible mechanism for the vegetation shift. In the model, the land cover change originates from differences in near-surface air temperature arising out of orbitally-induced insolation changes. According to the model results, the averaged forest fraction on the Plateau is shrinking by almost one-third from mid-Holocene (41.4%) to present-day (28.3%). Shrubs, whose fraction is quadrupled at present-day (12.3%), replace most of this forest. Gras fraction increases from 38.9% during the mid-Holocene to 42.3% at present-day. This land cover change results in a decrease of living biomass by 0.62 kgC m−2. Total biomass on the Tibetan Plateau decreases by 1.9 kgC m−2, i.e. approx. 6.64 PgC are released due to the natural land cover change.

scholarly journals Vegetation Change and Its Relationship with Climate Factors and Elevation on the Tibetan Plateau

2019 ◽  
Vol 16 (23) ◽  
pp. 4709 ◽  
Author(s):  
Yixin Zhang ◽  
Guoce Xu ◽  
Peng Li ◽  
Zhanbin Li ◽  
Yun Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Vegetation Change ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Climatic Factors ◽  
Sunshine Duration ◽  
The Tibetan Plateau ◽  
The North ◽  
Geographical Unit ◽  
Key Factor

As the “roof of the world”, the Tibetan Plateau (TP) is a unique geographical unit on Earth. In recent years, vegetation has gradually become a key factor reflecting the ecosystem since it is sensitive to ecological changes especially in arid and semi-arid areas. Based on the normalized difference vegetation index (NDVI) dataset of TP from 2000 to 2015, this study analyzed the characteristics of vegetation variation and the correlation between vegetation change and climatic factors at different time scales, based on a Mann–Kendall trend analyses, the Hurst exponent, and the Pettitt change-point test. The results showed that the vegetation fractional coverage (VFC) generally increased in the past 16 years, with 60.3% of the TP experiencing an increase, of which significant (p < 0.05) increases accounted for 28.79% and were mainly distributed in the north of the TP. Temperature had the largest response with the VFC on the seasonal scale. During the growing season, the correlation between precipitation and sunshine duration with VFC was high (p < 0.05). The change-points of the VFC were mainly distributed in the north of the TP during 2007–2009. Slope and elevation had an impact on the VFC; the areas with large vegetation change are mainly distributed in slopes <20° and elevation of 3000–5000 m. For elevation above 3000–4000 m, the response of the VFC to precipitation and temperature was the strongest. This study provided important information for ecological environment protection and ecosystem degradation on the Tibetan 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 Characteristics of Deep Convective Systems and Initiation during Warm Seasons over China and Its Vicinity

2021 ◽  
Vol 13 (21) ◽  
pp. 4289
Author(s):  
Yang Li ◽  
Yubao Liu ◽  
Yun Chen ◽  
Baojun Chen ◽  
Xin Zhang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
South China ◽  
Warm Season ◽  
Statistical Characteristics ◽  
The Tibetan Plateau ◽  
Spatiotemporal Resolution ◽  
Convective Systems ◽  
Seasonal And Diurnal Variations ◽  
Deep Convective Systems ◽  
Guizhou Plateau

The spatiotemporal statistical characteristics of warm-season deep convective systems, particularly deep convective systems initiation (DCSI), over China and its vicinity are investigated using Himawari-8 geostationary satellite measurements collected during April-September from 2016 to 2020. Based on a satellite brightness temperature multiple-threshold convection identification and tracking method, a total of 47593 deep convective systems with lifetimes of at least 3 h were identified in the region. There are three outstanding local maxima in the region, located in the southwestern, central and eastern Tibetan Plateau and Yunnan-Guizhou Plateau, followed by a region of high convective activities in South China. Most convective systems are developed over the Tibetan Plateau, predominantly eastward-moving, while those developed in Yunnan-Guizhou Plateau and South China mostly move westward and southwestward. The DSCI occurrences become extremely active after the onset of the summer monsoon and tend to reach a maximum in July and August, with a diurnal peak at 11–13 LST in response to the enhanced solar heating and monsoon flows. Several DCSI hotspots are identified in the regions of inland mountains, tropical islands and coastal mountains during daytime, but in basins, plains and coastal areas during nighttime. DCSI over land and oceans exhibits significantly different sub-seasonal and diurnal variations. Oceanic DCSI has an ambiguous diurnal variation, although its sub-seasonal variation is similar to that over land. It is demonstrated that the high spatiotemporal resolution satellite dataset provides rich information for understanding the convective systems over China and vicinity, particularly the complex terrain and oceans where radar observations are sparse or none, which will help to improve the convective systems and initiation nowcasting.

Dynamics of evapotranspiration and variations in different land-cover regions over the Tibetan Plateau during 1961-2014

2021 ◽  
Author(s):  
Shan Lin ◽  
Genxu Wang ◽  
Zhaoyong Hu ◽  
Kewei Huang ◽  
Xiangyang Sun ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Land Cover ◽  
Northwestern Part ◽  
The Tibetan Plateau ◽  
Southeastern Part ◽  
Available Energy ◽  
Forest Region ◽  
Energy Factors ◽  
Term Change ◽  
Increasing Trend

AbstractIn this study, the spatiotemporal changes and driving factors of evapotranspiration (ET) over the Tibetan Plateau (TP) are assessed from 1961-2014, based on a revised generalized nonlinear complementary (nonlinear-CR) model. The average annual ET on the TP was 328 mm/year. The highest ET value (711 mm/year) was found in the forest region in the southeastern part of the TP, and the lowest value (151 mm/year) was found in the desert region in the northwestern part of the TP. In terms of the contribution of different sub-regions to the total amount of ET for the whole plateau, the meadow and steppe regions contributed the most to the total amount of ET of TP, accounting for 30% and 18.5%, respectively. The interannual ET presented a significant increasing trend with a value of 0.26 mm/year from 1961 to 2014, and a significant positive ET trend was found over 35% of the region, mainly in the southeastern part of the plateau. The increasing trend of ET in swamp areas was the largest, while that in the desert areas was the smallest. In terms of the seasonality, the ET over the plateau and different land-cover regions increased the most in summer, followed by spring, while the change in ET in winter was not obvious. The energy factors dominated the long-term change in the annual ET over the plateau. In addition, the available energy is the controlling factor for ET changes in humid areas such as forests and shrublands. Energy and water factors together dominate the ET changes in arid areas.

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