Vegetation restoration in the coarse-textured soil area is more conducive to the accumulation of Fe-associated C.
Abstract
Vegetation restoration has an important effect on soil carbon (C) pool dynamics. Highly stable iron (Fe)-associated C is an important component of the soil C pool and it plays a crucial role in the soil C cycle. However, a knowledge gap remains regarding the existence of Fe-associated C variation during vegetation restoration. Herein, 0-60 cm soil samples of cropland, grassland, shrubland and forestland from three soil types (loam, loess and sandy soils) were collected to explore the response of Fe-associated C to vegetation restoration. The results showed that soil Fe-associated C proportion in the study area ranged from 2.2% to 26.3%. Surface soil (0-20 cm) Fe-associated C content in loess and sandy soils increased following vegetation restoration, but decreased in loam soil. The accumulation efficiency of soil Fe-associated C during vegetation restoration was higher in coarser soils. Moreover, the Fe-associated C content and proportion of forestland with a higher soil organic matter (SOM) pool were the highest among the land use types. Vegetation restoration affects soil Fe-associated C in two different ways: (1) increasing the SOM and dissolved organic C and improving the efficiency of C and Fe binding to promote the accumulation of Fe-associated C; (2) decreasing the total soil Fe content, reducing the trivalent iron (Fe(III)) to bivalent iron (Fe(II)) and breaking the binding of C and Fe to decrease soil Fe-associated C content, and these two different ways were found in all three soil types. Additionally, higher SOM accumulation efficiency and less root destruction caused by vegetation restoration in coarse soils resulted in a higher Fe-associated C accumulation efficiency. Synthesis and applications. Vegetation and soil type strongly regulated the effects of vegetation restoration on soil Fe-associated C. Forestlands may be the optimum vegetation type to provide soil C sequestration benefits, effectively increasing soil C pool and maximising Fe-associated C content. This study has addressed the knowledge gap regarding the effects of vegetation restoration on soil Fe-associated C and provides scientific basis for a better understanding of the soil C cycle and developing scientific vegetation restoration measures.