Responses of soil moisture in different land cover types to rainfall events in a re-vegetation catchment area of the Loess Plateau, China

Abstract

a b s t r a c t a r t i c l e i n f oImplementation of the Grain-for-Green project has resulted in significantly increased vegetative cover on the Loess Plateau of China during the past few decades. The plant communities influence soil moisture recharge and usage processes, particularly the input process, which is directly related to transformation of the limited precipitation into available soil water in the semi-arid Loess Plateau. A study to measure soil moisture dynamics of typical land cover types associated with precipitation events was conducted in a re-vegetated catchment area. Smart probes were inserted at 6 different depths below the ground surface under grass (Andropogon), subshrub (Artemisia scoparia), shrub (Spiraea pubescens), tree (Robinia pseudoacacia), and crop (Zea mays) vegetation to record volumetric soil moisture at 10-minute intervals for a period of 60 days during the growing season in 2011. The advance of the wetting front and total accumulated infiltrated water were measured. The rainfall events were sporadic with widely different intensities, and the soil moisture was replenished mainly by 3-4 heavy precipitation events during July and August. The mean soil moisture content profiles of the 5 vegetation types can be ordered as crop > grass > subshrub> tree> shrub and this relationship displayed time stability. The different land cover types clearly influenced the water infiltration and water input amounts in the re-vegetated area. The subshrub site showed the highest total infiltration amount (164 mm) with precipitation (227 mm) during the study period. The grass site had an infiltration amount of 156 mm. The tree site had a total precipitation of 154 mm and an infiltration amount of 97 mm. The infiltration amount was 136 mm for the shrub site and was the lowest (83 mm) for the crop site. Natural grasses displayed a rapid infiltration rate and the wetting front was able to reach a greater depth.

Linking the soil moisture distribution pattern to dynamic processes along slope transects in the Loess Plateau, China

“…In this revegetated area, the different land cover types were the main control on moisture distributions. This combination of land cover types and revegetation has also been extensively studied (Yang and Tian 2004;Shangguan and Zheng 2006;Chen et al 2008;Ran et al 2008, Hu et al 2009Wang et al 2010aWang et al , b, 2012Wang et al , 2013. This has resulted in the acquisition of data regarding the mean soil moisture dynamic characteristics and the differences between slopes and downslope regions.…”

“…1), which is a typical loess gully and hilly area with elevations ranging from 1050 to 1298 m Wang et al 2012Wang et al , 2013. This catchment has a total area of 2.02 km 2 , with a gully density of 2.74 km km −2 , and with slope gradients ranging from 10 to 30°.…”

“…We selected five sites with typical land cover types: a tree site (R. pseudoacacia), shrub site (S. pubescens), subshrub site (A. scoparia), grass site (Andropogon), and crop site (Zea mays) to observe the soil moisture dynamics every 10 min, using a H21 soil moisture and temperature logger system, with six S-SMC-M005 soil moisture smart sensors (Decagon Devices Inc., Pullman, WA, USA) at depths of 10, 20, 40, 60, 80, and 100 cm below the land surface (Wang et al 2012(Wang et al , 2013 to link the soil moisture distribution pattern with dynamic processes. The data for the tree site was missing from August 9 due to the data logger being damaged, while data for the shrub site were missing from August 8 to 15.…”

“…In turn, different land cover types affect the mutually interacting hydrologic processes, especially infiltration and evapotranspiration Wang et al 2012;Wang et al 2013), resulting in various characteristics of soil moisture dynamics (Qiu et al 2001a. Chen et al (2007) evaluated the relationship between land cover types and soil moisture dynamics in the Loess Plateau area for five vegetation types and found that soil water loss occurred during the growing season, and the moisture was not fully replenished from rainfall during the rainy season.…”

“…Chen et al (2007) evaluated the relationship between land cover types and soil moisture dynamics in the Loess Plateau area for five vegetation types and found that soil water loss occurred during the growing season, and the moisture was not fully replenished from rainfall during the rainy season. The soil moisture content for land covered by different vegetation types in the semiarid area of the Loess Plateau has been well studied and documented during the past few decades (Qiu et al 2001a;Fu et al 2003;Chen et al 2007;Wang et al 2012Wang et al , 2013. The studies have indicated that bare soils usually have higher soil moisture content than vegetated soils, and that annual crops and grasses have higher soil moisture content than forests .…”