Effects of soil-incorporated plant litter morphological characteristics on the soil detachment process in grassland on the Loess Plateau of China

Abstract

The Loess Plateau of China is one of the most eroded areas in the world. In the past 20 years, effective vegetation restoration measures have significantly changed the near-surface characteristics of soil. In natural conditions, plant litter is widespread in the topsoil. The effects of litter incorporated into soil on the process of soil detachment, which is closely related to plant litter morphology, are still not well known. This study aimed to detect the variation of litter morphological characteristics and quantify their effects on soil detachment capacity and rill erodibility when litter is incorporated into the soil. Four plant litters (Bothriochloa ischaemum (L.) Keng., Artemisia sacrorum Ledeb., Setaria viridis (L.) Beauv., and Artemisia capillaris Thunb.) with five length levels (<0.5, 0.5–2, 2–4, 4–6, and 6–8 cm) were incorporated into soil (idle for 50 days) at the same litter biomass rate (0.7 kg m−2). Then the soil was sampled and cores were subjected to overland flow under six flow shear stress levels (5.66, 8.31, 12.21, 15.55, 19.15 and, 22.11 Pa) using a hydraulic flume (4.0 m × 0.35 m). The results showed that the litter morphological characteristics of litter length density (LLD), litter surface area density (LSAD) and litter volume ratio (LVR) differed in plant species at the same litter biomass rate. Correspondingly, soil detachment capacity (ranging from 0.414 to 2.179 kg m−2 s−1) and rill erodibility (ranging from 0.037 to 0.177 s m−1) varied significantly and mean values from the Bothriochloa ischaemum (L.) Keng. treatments were the minimums, which were 28% to 37% and 23% to 35% less than that of the other treatments, respectively. The soil detachment capacity and rill erodibility were significantly correlated with the litter morphological characteristics of LLD, LSAD and LVR (p < 0.01). The contact area between litter and soil was the most critical factor affecting soil detachment. Incorporated plant litter residue litter effect on rill erodibility could be well estimated by LSAD.