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Climate variability rather than overstocking causes recent large scale cover changes of Tibetan pastures.

Lehnert LW, Wesche K, Trachte K, Reudenbach C, Bendix J - Sci Rep (2016)

Bottom Line: This supply function is claimed to be threatened by pasture degradation on the TP and the associated loss of water regulation functions.However, neither potential large scale degradation changes nor their drivers are known.Increasing livestock numbers as a result of land use changes exacerbated the negative trends but were not their exclusive driver.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Geography, Philipps-University of Marburg, Deutschhausstr. 10, 35037 Marburg, Germany.

ABSTRACT
The Tibetan Plateau (TP) is a globally important "water tower" that provides water for nearly 40% of the world's population. This supply function is claimed to be threatened by pasture degradation on the TP and the associated loss of water regulation functions. However, neither potential large scale degradation changes nor their drivers are known. Here, we analyse trends in a high-resolution dataset of grassland cover to determine the interactions among vegetation dynamics, climate change and human impacts on the TP. The results reveal that vegetation changes have regionally different triggers: While the vegetation cover has increased since the year 2000 in the north-eastern part of the TP due to an increase in precipitation, it has declined in the central and western parts of the TP due to rising air temperature and declining precipitation. Increasing livestock numbers as a result of land use changes exacerbated the negative trends but were not their exclusive driver. Thus, we conclude that climate variability instead of overgrazing has been the primary cause for large scale vegetation cover changes on the TP since the new millennium. Since areas of positive and negative changes are almost equal in extent, pasture degradation is not generally proceeding.

No MeSH data available.


Related in: MedlinePlus

Trends in vegetation cover and climate variables between 2000 and 2013.(a) Plant cover trends during the growing season. (b) Histograms of the relative frequencies of significant plant cover trends in Qinghai and the TAR (significance level of 0.05). Note that the distributions are bimodal because only significant changes are considered. Maps in (c) and (d) show trends in precipitation sums and the mean 2 m air temperature, respectively. The colours indicate the τ-values of the Mann-Kendall correlations, and the (+) labels mark areas where the correlations are significant at the 0.05 confidence level. For interpretation note that all of the correlations were calculated from the anomalies of the variables. The maps and the histograms have been created using R statistical software40.
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f3: Trends in vegetation cover and climate variables between 2000 and 2013.(a) Plant cover trends during the growing season. (b) Histograms of the relative frequencies of significant plant cover trends in Qinghai and the TAR (significance level of 0.05). Note that the distributions are bimodal because only significant changes are considered. Maps in (c) and (d) show trends in precipitation sums and the mean 2 m air temperature, respectively. The colours indicate the τ-values of the Mann-Kendall correlations, and the (+) labels mark areas where the correlations are significant at the 0.05 confidence level. For interpretation note that all of the correlations were calculated from the anomalies of the variables. The maps and the histograms have been created using R statistical software40.

Mentions: The vegetation cover increased significantly between 2000 and 2013 along a large belt that encompasses southern Qinghai, the headwater region of the Yangtze and the eastern part of Qinghai (Fig. 3a). The largest increase was observed south of Lake Koko Nor. In contrast, the vegetation cover in the western and southern parts of the TAR has decreased, with the strongest negative trends being observed in the upper reaches of the Indus River. The south-eastern part of the TP does not show clear trends. The comparison of the accumulated vegetation cover trends for grid squares from Qinghai and the TAR highlight the different patterns in each area, with more positive vegetation cover changes for Qinghai and more negative vegetation cover changes for the TAR (Fig. 3b). For the prefectures of the TAR, predominantly negative trends have been observed for Ngari, Shigatze, Lhasa, and Shannan (Histograms in Fig. 2). Qamdo, Nyingtri and Nagqu featured less pronounced patterns.


Climate variability rather than overstocking causes recent large scale cover changes of Tibetan pastures.

Lehnert LW, Wesche K, Trachte K, Reudenbach C, Bendix J - Sci Rep (2016)

Trends in vegetation cover and climate variables between 2000 and 2013.(a) Plant cover trends during the growing season. (b) Histograms of the relative frequencies of significant plant cover trends in Qinghai and the TAR (significance level of 0.05). Note that the distributions are bimodal because only significant changes are considered. Maps in (c) and (d) show trends in precipitation sums and the mean 2 m air temperature, respectively. The colours indicate the τ-values of the Mann-Kendall correlations, and the (+) labels mark areas where the correlations are significant at the 0.05 confidence level. For interpretation note that all of the correlations were calculated from the anomalies of the variables. The maps and the histograms have been created using R statistical software40.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4829870&req=5

f3: Trends in vegetation cover and climate variables between 2000 and 2013.(a) Plant cover trends during the growing season. (b) Histograms of the relative frequencies of significant plant cover trends in Qinghai and the TAR (significance level of 0.05). Note that the distributions are bimodal because only significant changes are considered. Maps in (c) and (d) show trends in precipitation sums and the mean 2 m air temperature, respectively. The colours indicate the τ-values of the Mann-Kendall correlations, and the (+) labels mark areas where the correlations are significant at the 0.05 confidence level. For interpretation note that all of the correlations were calculated from the anomalies of the variables. The maps and the histograms have been created using R statistical software40.
Mentions: The vegetation cover increased significantly between 2000 and 2013 along a large belt that encompasses southern Qinghai, the headwater region of the Yangtze and the eastern part of Qinghai (Fig. 3a). The largest increase was observed south of Lake Koko Nor. In contrast, the vegetation cover in the western and southern parts of the TAR has decreased, with the strongest negative trends being observed in the upper reaches of the Indus River. The south-eastern part of the TP does not show clear trends. The comparison of the accumulated vegetation cover trends for grid squares from Qinghai and the TAR highlight the different patterns in each area, with more positive vegetation cover changes for Qinghai and more negative vegetation cover changes for the TAR (Fig. 3b). For the prefectures of the TAR, predominantly negative trends have been observed for Ngari, Shigatze, Lhasa, and Shannan (Histograms in Fig. 2). Qamdo, Nyingtri and Nagqu featured less pronounced patterns.

Bottom Line: This supply function is claimed to be threatened by pasture degradation on the TP and the associated loss of water regulation functions.However, neither potential large scale degradation changes nor their drivers are known.Increasing livestock numbers as a result of land use changes exacerbated the negative trends but were not their exclusive driver.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Geography, Philipps-University of Marburg, Deutschhausstr. 10, 35037 Marburg, Germany.

ABSTRACT
The Tibetan Plateau (TP) is a globally important "water tower" that provides water for nearly 40% of the world's population. This supply function is claimed to be threatened by pasture degradation on the TP and the associated loss of water regulation functions. However, neither potential large scale degradation changes nor their drivers are known. Here, we analyse trends in a high-resolution dataset of grassland cover to determine the interactions among vegetation dynamics, climate change and human impacts on the TP. The results reveal that vegetation changes have regionally different triggers: While the vegetation cover has increased since the year 2000 in the north-eastern part of the TP due to an increase in precipitation, it has declined in the central and western parts of the TP due to rising air temperature and declining precipitation. Increasing livestock numbers as a result of land use changes exacerbated the negative trends but were not their exclusive driver. Thus, we conclude that climate variability instead of overgrazing has been the primary cause for large scale vegetation cover changes on the TP since the new millennium. Since areas of positive and negative changes are almost equal in extent, pasture degradation is not generally proceeding.

No MeSH data available.


Related in: MedlinePlus