Exploring Soil Particle Size Fraction and Spatial Redistribution of 137Cs in Sloping Landscapes with Different Lynchet Heights of Terracing Hedgerows in the Remote Mountain Region of Southwestern China

Abstract

Soil erosion is a global environmental problem related to anthropogenic activities which are influenced by natural factors. The sloping cultivated lands, with serious soil erosion, constitute a significant proportion of the landscape in the remote mountain regions of southwestern China. The traditional soil conservation strategy, involving a certain height of lynchets on the edge of the terracing hedgerows of the sloping lands, plays an effective part in soil and water conservation. A typical sloping landscape with a lynchet of terracing hedgerows was chosen in this study. The objective of this study was to explore soil particle size fraction and spatial redistribution of 137Cs in sloping landscapes with different lynchet heights of terracing hedgerows. The results showed that fine-grained sediments were deposited in front of the lynchet of terracing hedgerows, especially particle sizes grouped at <0.002 mm clay and 0.002–0.02 mm silt. The 137Cs concentration profiles of the lynchet from the upper to the lower sloping landscape showed first increasing and then decreasing trends when the soil depth increased. 137Cs inventory generally increased along with the whole sloping landscapes. Moreover, the results suggested that the mean 137Cs inventory and erosion rate could be represented by the average value of the middle slope position. The highest value of annual erosion modulus reached 4917.06 t km−2 a−1 on the upper site of the sloping lands. Moreover, the annual erosion modulus was synchronously reduced from the upper to the lower sloping landscape and the erosion rate had a similar trend. Meanwhile, the K values of soil erodibility changed from 0.0338 t hm2 h (hm−2 MJ−1 mm−1) to 0.0375 t hm2 h (hm−2 MJ−1 mm−1) along the slope length. There was a logarithmic relationship between the K value and the 137Cs inventory. Therefore, it is useful to study spatial patterns of soil erosion in different slope positions with different heights of lynchet of terracing hedgerows of the whole sloping landscape. Moreover, it is important to implement a soil conservation strategy in the remote mountain regions of China.