Response of deep soil moisture to land use and afforestation in the semi-arid Loess Plateau, China

Abstract

s u m m a r ySoil moisture is an effective water source for plant growth in the semi-arid Loess Plateau of China. Characterizing the response of deep soil moisture to land use and afforestation is important for the sustainability of vegetation restoration in this region. In this paper, the dynamics of soil moisture were quantified to evaluate the effect of land use on soil moisture at a depth of 2 m. Specifically, the gravimetric soil moisture content was measured in the soil layer between 0 and 8 m for five land use types in the Longtan catchment of the western Loess Plateau. The land use types included traditional farmland, native grassland, and lands converted from traditional farmland (pasture grassland, shrubland and forestland). Results indicate that the deep soil moisture content decreased more than 35% after land use conversion, and a soil moisture deficit appeared in all types of land with introduced vegetation. The introduced vegetation decreased the soil moisture content to levels lower than the reference value representing no human impact in the entire 0-8 m soil profile. No significant differences appeared between different land use types and introduced vegetation covers, especially in deeper soil layers, regardless of which plant species were introduced. High planting density was found to be the main reason for the severe deficit of soil moisture. Landscape management activities such as tillage activities, micro-topography reconstruction, and fallowed farmland affected soil moisture in both shallow and deep soil layers. Tillage and micro-topography reconstruction can be used as effective countermeasures to reduce the soil moisture deficit due to their ability to increase soil moisture content. For sustainable vegetation restoration in a vulnerable semi-arid region, the plant density should be optimized with local soil moisture conditions and appropriate landscape management practices.

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

“…6 indicated that soil-water regimes depended highly on the plant species of the land-use patterns. The AW in the farmland was the highest, followed by grassland, and the AW in S was the lowest; this trend was consistent with the results of Yang et al (2012) whose SWC data was based on a 0-800 cm soil profile (which may reflect plant-root development to some extent). AW in the mixed land-use patterns was in the order S-O > S-G > S-Alf.…”

“…Considerable interest has since been generated around the world in the assessment of vertical distribution and influencing factors Yang et al, 2012), depletion and replenishment (Li and Huang, 2008;Liu et al, 2010), dynamics and simulations (Jipp et al, 1998;Markewitz et al, 2010;Zhao et al, 2008) of SWC in soils to a depth of roughly 1000 cm. The depth of depletion of SWC, inferred to be a function of root uptake, has recently been reported to be 1800 cm in an Amazonian forest (Davidson et al, 2011) and to be 1550, 2240 and 2150 cm (based on the comparison of soil-water conditions between shrublands/forests and permanent farmland) in alfalfa grassland, Caragana korshinskii shrubland and pine forest, respectively, on the Loess Plateau of China (Wang et al, 2009).…”

“…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.…”

Effects of vegetation restoration on the spatial distribution of soil moisture at the hillslope scale in semi-arid regions

“…However, unlike native plants, introduced vegetation usually has a higher water demand and annual rainfall levels cannot supply sufficient water for growth (Chen et al, 2008a;Wang et al, 2010). Introduced plants in this region are thus forced to develop deep and robust root systems to utilize soil moisture in deep soil layers (Chen et al, 2008a;Yang et al, 2012a). The limited water stored below the surface layers has become a particularly important component of ecosystems in this region.…”

Time-varying parameter models for catchments with land use change: the importance of model structure

“…The literature on land use change and its impacts on catchment hydrology is extensive, with studies examining the effects of (1) conversion to agricultural land use (Thanapakpawin et al, 2007;Warburton et al, 2012); (2) deforestation (Costa et al, 2003;Coe et al, 2011); (3) afforestation (e.g., Yang et al, 2012;Brown et al, 2013) and (4) urbanization (Bhaduri et al, 2001;Rose and Peters, 2001). Fewer studies have examined how traditional modeling approaches must be modified to handle nonstationary conditions, or how modeling methods can be used to assess impacts of land use change.…”