scholarly journals Evaluating the Influence of Climate Change on Sophora moorcroftiana (Benth.) Baker Habitat Distribution on the Tibetan Plateau Using Maximum Entropy Model

Forests ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1230
Author(s):  
Fumei Xin ◽  
Jiming Liu ◽  
Chen Chang ◽  
Yuting Wang ◽  
Liming Jia

The ecosystems across the Tibetan Plateau are changing rapidly in response to climate change, which poses unprecedented challenges for the control and mitigation of desertification on the Tibetan Plateau. Sophora moorcroftiana (Benth.) Baker is a drought-resistant plant species that has great potential to be used for desertification and soil degradation control on the Tibetan Plateau. In this study, using a maximum entropy (MaxEnt) niche model, we characterized the habitat distribution of S. moorcroftiana on the Tibetan Plateau under both current and future climate scenarios. To construct a robust model, 242 population occurrence records, gathered from our field surveys, historical data records, and a literature review, were used to calibrate the MaxEnt model. Our results showed that, under current environmental conditions, the habitat of S. moorcroftiana was concentrated in regions along the Yarlung Tsangpo, Lancang, and Jinsha rivers on the Tibetan Plateau. Elevation, isothermality, and minimal air temperature of the coldest month played a dominant role in determining the habitat distribution of S. moorcroftiana. Under future climate scenarios, the increased air temperature was likely to benefit the expansion of S. moorcroftiana over the short term, but, in the long run, continued warming may restrict the growth of S. moorcroftiana and lead to a contraction in its habitat. Importantly, the Yarlung Tsangpo River valley was found to be the core habitat of S. moorcroftiana, and this habitat moved westwards along the Yarlung Tsangpo River under future climate scenarios, but did not detach from it. This finding suggests that, with the current pace of climate change, an increase in efforts to protect and cultivate S. moorcroftiana is necessary and critical to control desertification on the Tibetan Plateau.

2021 ◽  
Author(s):  
Dongfeng Li ◽  
Xixi Lu ◽  
Ting Zhang

<p>Sediment flux in cold environments is a crucial proxy to link glacial, periglacial, and fluvial systems and highly relevant to hydropower operation, water quality, and the riverine carbon cycle. However, the long-term impacts of climate change and multiple human activities on sediment flux changes in cold environments remain insufficiently investigated due to the lack of monitoring and the complexity of the sediment cascade. Here we examine the multi-decadal changes in the in-situ observed fluvial sediment fluxes from two types of basins, namely, pristine basins and disturbed basins, in the Tibetan Plateau and its margins. The results show that the fluvial sediment fluxes in the pristine Tuotuohe headwater have substantially increased over the past three decades (i.e., a net increase of 135% from 1985–1997 to 1998–2017) due to the warming and wetting climate. We also quantify the relative impacts of air temperature and precipitation on the increases in the sediment fluxes with a novel attribution approach and finds that climate warming and intensified glacier-snow-permafrost melting is the primary cause of the increased sediment fluxes in the pristine cold environment (Tuotuohe headwater), with precipitation increase and its associated pluvial processes being the secondary driver. By contrast, the sediment fluxes in the downstream disturbed Jinsha River (southeastern margin of the Tibetan Plateau) exhibit a net increase of 42% from 1966-1984 to 1985-2010 mainly due to human activities such as deforestation and mineral extraction (contribution of 82%) and secondly because of climate change (contribution of 18%). Then the sediment fluxes dropped by 76% during the period of 2011-2015 because of the operations of six cascade reservoirs since 2010. In an expected warming and wetting climate for the region, we predict that the sediment fluxes in the pristine headwaters of the Tibetan Plateau will continue to increase throughout the 21st century, but the rising sediment fluxes from the Tibetan Plateau would be mostly trapped in its marginal reservoirs.</p><p>Overall, this work has provided the sedimentary evidence of modern climate change through robust observational sediment flux data over multiple decades. It demonstrates that sediment fluxes in pristine cold environments are more sensitive to air temperature and thermal-driven geomorphic processes than to precipitation and pluvial-driven processes. It also provides a guide to assess the relative impacts of human activities and climate change on fluvial sediment flux changes and has significant implications for water resources stakeholders to better design and manage the hydropower dams in a changing climate. Such findings may also have implications for other cold environments such as the Arctic, Antarctic, and other high mountainous basins.</p><p>Furthermore, this research is under the project of "Water and Sediment Fluxes Response to Climate Change in the Headwater Rivers of Asian Highlands" (supported by the IPCC and the Cuomo Foundation) and the project of "Sediment Load Responses to Climate Change in High Mountain Asia" (supported by the Ministry of Education of Singapore). Part of the results are also published in Li et al., 2018 Geomorphology, Li et al., 2020 Geophysical Research Letters, and Li et al., 2021 Water Resources Research.</p>


2020 ◽  
Vol 20 (2) ◽  
pp. 881-899 ◽  
Author(s):  
Aolin Jia ◽  
Shunlin Liang ◽  
Dongdong Wang ◽  
Bo Jiang ◽  
Xiaotong Zhang

Abstract. The Tibetan Plateau (TP) plays a vital role in regional and global climate change. The TP has been undergoing significant surface warming starting from 1850, with an air temperature increase of 1.39 K and surface solar dimming resulting from decreased incident solar radiation. The causes and impacts of solar dimming on surface warming are unclear. In this study, long-term (from 1850 to 2015) surface downward radiation datasets over the TP are developed by integrating 18 Coupled Model Intercomparison Project phase 5 (CMIP5) models and satellite products. The validation results from two ground measurement networks show that the generated downward surface radiation datasets have a higher accuracy than the mean of multiple CMIP5 datasets and the fused datasets of reanalysis and satellite products. After analyzing the generated radiation data with four air temperature datasets, we found that downward shortwave radiation (DSR) remained stable before 1950 and then declined rapidly at a rate of −0.53 W m−2 per decade, and that the fastest decrease in DSR occurs in the southeastern TP. Evidence from site measurements, satellite observations, reanalysis, and model simulations suggested that the TP solar dimming was primarily driven by increased anthropogenic aerosols. The TP solar dimming is stronger in summer, at the same time that the increasing magnitude of the surface air temperature is the smallest. The cooling effect of solar dimming offsets surface warming on the TP by 0.80±0.28 K (48.6±17.3 %) in summer since 1850. It helps us understand the role of anthropogenic aerosols in climate warming and highlights the need for additional studies to be conducted to quantify the influence of air pollution on regional climate change over the TP.


2019 ◽  
Author(s):  
Aolin Jia ◽  
Shunlin Liang ◽  
Dongdong Wang ◽  
Bo Jiang ◽  
Xiaotong Zhang

Abstract. The Tibetan Plateau (TP) plays a vital role in regional and global climate change. The TP has been undergoing significant surface warming since 1850, with an air temperature increase of 1.39 K and surface solar dimming resulting from decreased incident solar radiation. The causes and impacts of solar dimming on surface warming are unclear. In this study, long-term (from 1850–2015) surface downward radiation datasets over the TP are developed by integrating 18 Coupled Model Intercomparison Project Phase 5 (CMIP5) models and satellite products. The validation results from two ground measurement networks show that the generated downward surface radiation datasets have higher accuracy than the mean of multiple CMIP5 and the fused datasets of reanalysis and satellite products. After analyzing the generated radiation data with four air temperature datasets, we found that downward shortwave radiation (DSR) remained stable before 1950 and then declined rapidly at a rate of −0.53 W m−2 per decade and that the fastest decrease in DSR is in the southeastern TP. Evidence from site measurements, satellite observations, reanalysis, and model simulations suggested that TP solar dimming was primarily driven by increased anthropogenic aerosols. The TP solar dimming is stronger in summer, at the same time that the increasing magnitude of the surface air temperature is the smallest. The cooling effect of solar dimming offsets surface warming on the TP by 0.80 ± 0.28 K (48.6 ± 17.3 %) in summer. It helps us understand the role of anthropogenic aerosols in climate warming, and highlights the need for additional studies to be conducted to quantify the influence of air pollution on regional climate change over the TP.


2020 ◽  
Author(s):  
Yao Jiang ◽  
Zongxue Xu

<p>Understanding the dynamics of basin-scale water budgets over the Tibetan Plateau (TP) is significant for hydrology and water resource management in the southern and eastern Asia. However, a detailed water balance analysis is limited by the lack of adequate hydro-climatic observations in this region. In this study, we investigate the spatiotemporal variation of water budget components (e.g. precipitation P, evapotranspiration ET and runoff Q etc.) in the Yarlung Tsangpo River basin (YTB) of southeast TP during the period of 1975-2015 through using multi-source datasets (e.g. insitu observation, remote sensing data products, reanalysis outputs and model simulations etc.). The change trend of water budget components and vegetation parameters was analyzed in the YTB on interannual scale. The results indicated that the detailed water budgets are different from upstream to downstream YTB due to different temperature, vegetation cover and evapotranspiration, which are mainly affected by different climate conditions. In the whole basin, precipitation that are mainly during June to October was the major contributor to the runoff. The P and Q were found to show a slight but insignificant decrease in most regions of YTB since the late 1990s, which showed positive relationships with the weakening Indian summer monsoon. While the ET showed an insignificant increase across most of the YTB, especially in the middle basin. The runoff coefficient (Q/P) exhibited an indistinctively decreasing trend which may be, to some extent, due to the overlap effects of ET increase and snow and glacier changes. The obtained results offer insights into understanding the evolution mechanism of hydrological processes in such a data-sparse region under changing environment.</p>


Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 181
Author(s):  
Yuchen Wang ◽  
Tong Zhao ◽  
Zhifang Xu ◽  
Huiguo Sun ◽  
Jiangyi Zhang

Germanium/Silicon (Ge/Si) ratio is a common proxy for primary mineral dissolution and secondary clay formation yet could be affected by hydrothermal and anthropogenic activities. To decipher the main controls of riverine Ge/Si ratios and evaluate the validity of the Ge/Si ratio as a weathering proxy in the Tibetan Plateau, a detailed study was presented on Ge/Si ratios in the Yarlung Tsangpo River, southern Tibetan Plateau. River water and hydrothermal water were collected across different climatic and tectonic zones, with altitudes ranging from 800 m to 5000 m. The correlations between TDS (total dissolved solids) and the Ge/Si ratio and Si and Ge concentrations of river water, combined with the spatial and temporal variations of the Ge/Si ratio, indicate that the contribution of hydrothermal water significantly affects the Ge/Si ratio of the Yarlung Tsangpo River water, especially in the upper and middle reaches. Based on the mass balance calculation, a significant amount of Ge (11–88%) has been lost during its transportation from hydrothermal water to the river system; these could result from the incorporation of Ge on/into clays, iron hydroxide, and sulfate mineral. In comparison, due to the hydrothermal input, the average Ge/Si ratio in the Yarlung Tsangpo River is a magnitude order higher than the majority of rivers over the world. Therefore, evaluation of the contribution of hydrothermal sources should be considered when using the Ge/Si ratio to trace silicate weathering in rivers around the Tibetan Plateau.


2019 ◽  
Vol 25 ◽  
pp. 63-70
Author(s):  
Torsten Haberzettl ◽  
Gerhard Daut ◽  
Nora Schulze ◽  
Volkhard Spiess ◽  
Junbo Wang ◽  
...  

Abstract. The Tibetan Plateau is of peculiar societal relevance as it provides freshwater from the so-called “Water Tower of Asia” to a large portion of the Asian population. However, future climate change will affect the hydrological cycle in this area. To define parameters for future climate change scenarios it is necessary to improve the knowledge about thresholds, timing, pace and intensity of past climatic changes and associated environmental impacts. Sedimentary archives reaching far back in time and spanning several glacial–interglacial cycles such as Nam Co provide the unique possibility to extract such information. In order to explore the scientific opportunities that an ICDP drilling effort at Nam Co would provide, 40 scientists from 13 countries representing various scientific disciplines met in Beijing from 22 to 24 May 2018. Besides paleoclimatic investigations, opportunities for paleomagnetic, deep biosphere, tectonic and paleobiological studies were discussed. After having explored the technical and logistical challenges and the scientific opportunities all participants agreed on the great value and need to drill this extraordinary archive, which has a sediment thickness of more than 1 km, likely covering more than 1 Ma.


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