The impact of land use and land cover changes on soil moisture and hydraulic conductivity along the karst hillslopes of southwest China

Abstract

The understanding of the temporal and spatial dynamics of soil moisture and hydraulic property is crucial to the study of several hydrological and ecological processes. Karst environments are extremely fragile because of thin soil and small soil water holding capacity. A marked intensification of agricultural land use and deforestation due to increase of population and thus expansion of agricultural areas has made the karst environment even more delicate. In this study, the soil moisture contents (SMC) and hydraulic conductivities (K) along four karst hillslopes were measured in situ by time domain reflectometry and the Guelph Permeameter, respectively, at test plots, each of which has a different vegetative cover, landform, land surface slope, soil property and content of rock fragment. The statistical results from the measurements show that land cover changes strongly affect the distribution of soil moisture and hydraulic properties. Compared with SMC in the bare soil areas, SMC values are 30.5, 20.1 and 10.2% greater in the forest, shrub and grass areas, respectively. Vegetation roots significantly increase permeability of low-layer silt soils. Measured K values were 0.8, 0.6 and 0.01 cm/min for the forest, agriculture and bare soil areas, respectively. When the forest was destroyed by fire or cut to become an agricultural area or bare soils, SMC would be reduced by 13.1 and 32.1%, respectively. If deforestation leads to strong rock desertification, SMC was reduced by 70%. Bedrock fractures significantly reduce the SMC in the overlying layer, but increase K values. SMC values of 30-45% would be reduced to 17-30% for the soil layer embedding rocks with and without fractures, respectively. K values could be increased from 1.0 to 8.5 cm/min. SMC are sensitive to terrain. A slope angle increase of 1°would reduce SMC about 0.82%. These changes resulting from land cover and land use alterations offer useful information to further investigate the response of ecosystem evolution to hydrodynamic processes.

Relationship between carbon dioxide in Balcarka Cave and adjacent soils in the Moravian Karst region of the Czech Republic

“…The highest CO 2 concentrations in anthropogenic soils were expected because of soil cultivating, fertilizing, and enhanced organic matter content. A concern exists about the negative impact of land use on the karst system/processes, especially via (i) changes in soil texture, moisture, and hydraulic conductivity (Canora et al, 2008;Chen et al, 2009), (ii) soil erosion (Febles et al, 2009), (iii) water pollution (Jiang et al, 2008), and (iv) a complex of influences (Baker & Genty, 1998;Balák et al, 1999). With respect to carbon dioxide, however, we do not recognize a fundamental problem.…”

Choosing an optimal land-use pattern for restoring eco-environments in a semiarid region of the Chinese Loess Plateau

“…For example, past studies have generally shown an order of forest < shrub < grassland < cultivated soils for soil water in upper few meters of soil (Chen et al, 2009;Yang et al, 2012). Most studies of land-use patterns, however, did not systematically consider the regimes of deep SWC, the extent of DSL or the aboveground net primary productivity (ANPP) of the dominant species.…”

Vertical distribution of soil saturated hydraulic conductivity and its influencing factors in a small karst catchment in Southwest China

“…For example, Li et al (2008) found significant differences of hydraulic conductivity among different topographic units of the dolines, and the influence of RC was not obvious. Chen et al (2009) focused on the influence of land-use types and found a significant difference of hydraulic conductivity among forest, agriculture, and bare soil areas. Chen et al (2012a) found the soil near-saturated hydraulic conductivity to be high and to exceed the rates of most natural rainfall events, confirming that overland flow is rare on karst hillslopes.…”