Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Hydrol. Earth Syst. Sci., 21, 2249-2261, 2017
https://doi.org/10.5194/hess-21-2249-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
02 May 2017
Variation of soil hydraulic properties with alpine grassland degradation in the eastern Tibetan Plateau
Tao Pan1,3, Shuai Hou1,2, Shaohong Wu1, Yujie Liu1, Yanhua Liu1, Xintong Zou1,2, Anna Herzberger3, and Jianguo Liu3 1Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
2University of the Chinese Academy of Sciences, Beijing, 100049, China
3Center for Systems Integration and Sustainability, Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824, USA
Abstract.

Ecosystems in alpine mountainous regions are vulnerable and easily disturbed by global environmental change. Alpine swamp meadow, a unique grassland type in the eastern Tibetan Plateau that provides important ecosystem services to the upstream and downstream regions of international rivers of Asia and other parts of the world, is undergoing severe degradation, which can dramatically alter soil hydraulic properties and water cycling processes. However, the effects of alpine swamp meadow degradation on soil hydraulic properties and the corresponding influencing mechanisms are still poorly understood. In this study, soil moisture content (SMC), field capacity (FC) and saturated hydraulic conductivity (Ks) together with several basic soil properties under lightly degraded (LD), moderately degraded (MD) and severely degraded (SD) alpine swamp meadow were investigated; the variations in SMC, FC and Ks with alpine swamp meadow degradation and their dominant influencing factors were analysed. The results showed that SMC and FC decreased consistently from LD to SD, while Ks decreased from LD to MD and then increased from MD to SD, following the order of LD  >  SD  >  MD. Significant differences in soil hydraulic properties between degradation degrees were found in the upper soil layers (0–20 cm), indicating that the influences of degradation were most pronounced in the topsoils. FC was positively correlated with capillary porosity, water-stable aggregates, soil organic carbon, and silt and clay content; Ks was positively correlated with non-capillary porosity (NCP). Relative to other soil properties, soil porosity is the dominant factor influencing FC and Ks. Capillary porosity explained 91.1 % of total variance in FC, and NCP explained 97.3 % of total variance in Ks. The combined effect of disappearing root activities and increasing sand content was responsible for the inconsistent patterns of NCP and Ks. Our findings suggest that alpine swamp meadow degradation would inevitably lead to reduced water holding capacity and rainfall infiltration. This study provides a more comprehensive understanding of the soil hydrological effects of vegetation degradation. Further hydrological modelling studies in the Tibetan Plateau and similar regions are recommended to understand the effects of degraded alpine swamp meadows on soil hydraulic properties.

Citation: Pan, T., Hou, S., Wu, S., Liu, Y., Liu, Y., Zou, X., Herzberger, A., and Liu, J.: Variation of soil hydraulic properties with alpine grassland degradation in the eastern Tibetan Plateau, Hydrol. Earth Syst. Sci., 21, 2249-2261, https://doi.org/10.5194/hess-21-2249-2017, 2017.

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This study shows that soil hydraulic properties, especially those of the top soil, varied greatly with alpine swamp meadow degradation. Soil porosity is the dominant influencing factor of soil hydraulic properties. The results suggest that alpine swamp meadow degradation would inevitably lead to negative hydrological effects. Hydrological modelling in the Tibetan Plateau and similar regions are recommended to understand the effects of degradation on soil hydraulic properties.
This study shows that soil hydraulic properties, especially those of the top soil, varied...
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