Mulching cannot further amplify the improved effects of infiltration hole on soil environment in level ditch in semiarid loess plateau, northwestern China

Abstract

Vegetation restoration is an important strategy for addressing global climate change challenges. Slope engineering measures are conducive to improve vegetation growth by improving soil environments. Infiltration hole is an effective supplement of existing measures to enhance the replenishment of deep soil water and nutrients in semi-arid area, but also increases shallow soil evaporation after rainfall. Can mulching further enhance the improved effects of infiltration hole on soil environments in slope measure via reducing ineffective evaporation under field conditions? In this study, the effects of different measures on soil environment and vegetation growth in level ditch were estimated, including control (LD) and infiltration hole (LD-IH), branch mulching (LD-BM), and their combination (LD-IH-BM). The results showed that the replenishment depth of rainfall was not variable under LD-BM after two rainy seasons, however, the one was increased by 40 cm and 30 cm under LD-IH and LD-IH-BM, respectively. The soil water storage (0–300 cm) under LD-IH and LD-IH-BM was obviously increased by 52.5/66.2 mm and 40.4/54.1 mm compared with LD/LD-BM, respectively. The increment of soil water storage (50–150 cm) was significantly higher under LD-IH and LD-IH-BM than LD and LD-BM. LD-BM just increased soil organic carbon and total nitrogen content of 0–10 cm soil layer and LD-IH and LD-IH-BM mainly increased that of 60–100 cm. The soil carbon/nitrogen storage (0–120 cm) was increased by 13.0/0.80 Mg hm−2, 29.8/2.81 Mg hm−2, and 20.3/2.54 Mg hm−2 under LD-BM, LD-IH, and LD-IH-BM, respectively. The contribution in the effects under LD-IH-BM was from infiltration hole rather than branch mulching, and even branch mulching had a negative effect. Overall, the combination of level ditch and infiltration hole is sufficient to promote the rehabilitation of slope in semi-arid areas by improving soil environment, but adding mulching would not continue to further amplify these effects. Despite these favorable changes, they were insufficient to promote the growth of C. korshinskii during the experimental period of less than two years. Based only on a short-term field trial, practitioners do not need to add mulching to the ecosystem of level ditch and infiltration hole in slope management. However, a longer-term trial is needed to evaluate the necessity for adding mulching because of its long-term effect on soil property improvement. Our findings provide the insight in selecting reasonably slope combined measures to successful vegetation restoration in semi-arid areas.