Influence of bare rocks on surrounding soil moisture in the karst rocky desertification regions under drought conditions

• Karst rocky desertification is a serious geo-ecological problem in Southwest China.
• We found that bare rocks influenced the surrounding soil moisture by shading.
• The effect degree of rocks to surrounding soil moisture correlated with its shape.
• Soil moisture on the north side of the rocks was significantly higher than others.
• The location at 15 cm north of the rocks was ideal site for plantation restoration.

A large number of bare rocks exposed in the field represent one of the most spectacular scenes of the Karst Rocky Desertification (KRD) process. The presence of bare rocks modifies the microenvironment. An understanding of soil moisture variability is necessary to characterize the linkages between a region's hydrology, ecology, and physiography. The objective of the study was to determine the influence of those exposed bare rocks on soil moisture in the surrounding area in a typical KRD region—the Forest Station of Sandoqing, in Fu'yuan County, Yun'nan Province, Southwest China. Dynamic soil moisture was quantified in Feb, 2010 during an extreme drought period. Results showed that during the drought period, soil moisture on the north side of the rocks was significantly higher than those on the east, west and south sides (p < 0.01). Soil surface moisture increased with the above-ground height of the rocks. The size of the bare rocks was significantly correlated with soil moisture on the west and north sides of the rocks (p < 0.01) and the east side of the rocks (p < 0.05). Sharper rocks were associated with declining soil moisture on the east, west and north sides of the rocks. Soil moisture began to increase and then declined on the north, east and west sides, but showed a continued increase on the south side with the distance from the rocks. The soil moisture around the rocks increased gradually with depths of soil layers. During the drought period bare rocks created some shade, resulting in higher soil moisture on the north side of the rocks compared to the other three directions. The location at 15 cm north of the rocks had the highest soil water content, thus becoming the most ideal site for establishing vegetation restoration in the KRD area under stressful environmental conditions. Results from this study can be used to assist in restoration of ecological system damaged by the KRD process.