Abstract: Understanding the responses of soil carbon to forest structure adjustment is an important issue concerning vegetation restoration in semi-arid regions. In this study, total carbon, organic carbon, and inorganic carbon in soils of three different plantations (Populus tomentosa plantation, Populus tomentosaplantationtransformed with Pinus tabuliformis for 5 years, and Populus tomentosaplantation transformed with Pinus tabuliformisfor 10 years) were analyzed in a typical semi-arid loess watershed. The results showed that: (1) The temporal changes of soil total carbon and soil organic carbon concentration were similar. Concentrations of soil total carbon and soil organic carbon increased over time. Soil organic carbon storage in both mixed plantations was significantly higher than that in pure plantation. There was no difference in soil total carbon and inorganic carbon storage among the three plantations. (2) Soil carbon concentrations were significantly correlated with soil moisture, bulk density, and pH in different plantations. Increased soil moisture and decreased pH and bulk density had a synergistic effect with increasing soil carbon. Our results can provide scientific guidance to vegetation restoration and the enhancement of ecosystem services in the semiarid Loess Plateau.

Key words: swarming, behavioral ecology, Euphausia superba, swimming, physiological ecology