Effects of grazing on net primary productivity,evapotranspiration and water use efficiency in the grasslands of Xinjiang,China |
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| Authors: | HUANG Xiaotao LUO Geping YE Feipeng HAN Qifei |
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| Institution: | 1.State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;2.University of Chinese Academy of Sciences, Beijing 100049, China;3.College of Resource and Environment Sciences, Xinjiang University, Urumqi 830046, China;4.Nanjing University of Information Science & Technology, Nanjing 210044, China |
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| Abstract: | Grazing is a main human activity in the grasslands of Xinjiang, China. It is vital to identify the effects of grazing on the sustainable utilization of local grasslands. However, the effects of grazing on net primary productivity (NPP), evapotranspiration (ET)and water use efficiency (WUE) in this region remain unclear. Using the spatial Biome-BGC grazing model, we explored the effects of grazing on NPP, ET and WUE across the different regions and grassland types in Xinjiang during 1979-2012. NPP, ET and WUEunder the grazed scenario were generally lower than those under the ungrazed scenario, and the differences showed increasing trends over time.The decreases in NPP, ET and WUE varied significantly among the regions and grassland types. NPP decreasedas follows: among the regions, Northern Xinjiang(16.60 g C/(m2?a)), Tianshan Mountains (15.94g C/(m2?a)) and Southern Xinjiang (-3.54g C/(m2?a)); andamong the grassland types, typical grasslands (25.70g C/(m2?a)), swamp meadows (25.26g C/(m2?a)),mid-mountain meadows (23.39 g C/(m2?a)), alpine meadows (6.33g C/(m2?a)), desert grasslands (5.82g C/(m2?a)) and saline meadows(2.90g C/(m2?a)). ET decreasedas follows: among the regions, Tianshan Mountains (28.95 mm/a), Northern Xinjiang (8.11mm/a) and Southern Xinjiang (7.57 mm/a);and among thegrassland types, mid-mountain meadows (29.30 mm/a), swamp meadows (25.07mm/a), typical grasslands (24.56mm/a), alpine meadows (20.69mm/a), desert grasslands (11.06mm/a) and saline meadows (3.44mm/a). WUE decreasedas follows: among the regions,Northern Xinjiang (0.053g C/kg H2O), Tianshan Mountains (0.034 g C/kg H2O) and Southern Xinjiang (0.012 g C/kg H2O);and among the grassland types, typical grasslands (0.0609 g C/kg H2O), swamp meadows (0.0548 g C/kg H2O), mid-mountain meadows (0.0501 g C/kg H2O), desert grasslands (0.0172 g C/kg H2O), alpine meadows (0.0121 g C/kg H2O) and saline meadows (0.0067 g C/kg H2O). In general, the decreases in NPP and WUE weremore significant in the regions with relatively high levels of vegetation growth because of the high grazing intensity in these regions. The decreases in ET weresignificant in mountainous areas due to theterrain and high grazing intensity. |
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| Keywords: | grazing effect grassland type net primary productivity evapotranspiration water use efficiency Biome-BGC grazing model |
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