Soil organic matter and silt contents determine soil particle surface electrochemical properties across a long-term natural restoration grassland

Abstract

Vegetation restoration is an effective way to rebuild degraded ecosystems and restore soil function. Soil surface electrochemical properties, including specific surface area, cation exchange capacity, surface charge density, surface electric field strength, and surface potential, are often used as indicators to evaluate agricultural soil quality and fertility. However, little attention has been payed to the effect of natural revegetation on soil surface electrochemical properties. In this work, we selected a grassland restoration chronosequence (slope cropland, 0 years; natural grasslands restored for 3, 8, 22 and 24 years, i.e. NR3, NR8, NR22 and NR24, respectively) to investigate the changes of soil surface electrochemical properties along with vegetative restoration. Our results showed that surface charge density and surface potential for restored grassland ranged from 0.16 to 0.20 C m−2 and from −94 to −109 mV, with an average of 0.18 C m−2 and −101 mV, respectively. The value of surface electric field strength could reach to the order of magnitude of −107 V m−1 and showed a decreasing trend with increasing period of natural vegetation recovery. Cation exchange capacity and specific surface area significantly increased with the extension of natural restoration period except for NR3 (P < 0.05). It was found that soil organic matter (SOM) and silt content were the main factors to determine cation exchange capacity and specific surface area. Both cation exchange capacity and specific surface area were closely related to silt content but weakly related to clay content, possibly due to the high silt content in our studied soils. Moreover, cation exchange capacity and specific surface area showed a significant linear relationship with SOM, which may be ascribed to the diversity in cation substitution sites and high specific surface area of SOM. Our results indicated that the long-term natural restoration of grassland contributed to the improvement of cation exchange capacity and specific surface area.