Soil erosion has resulted in serious land degradation in Yuanmou dry-hot valley, Yunnan province, China. Vegetation restoration had been widely developed in this hot and arid area. In this work we investigate the quality of rhizosphere soils under four restoration species in the towns of Zuolin (gully bed) and Yuanma (slope area). The vegetation included two trees [Leucaena leucocephala (Lam.) de Wit. and Eucalyptus camaldulensis L.] for the slope area, one shrubland [Dodonaea viscosa (Linn.) Jacq. Enum.] and one native, natural grassland [Heteropogon contortus (L.) Beauv.] for gully bed. Soil physical (bulk density and soil moisture content), chemical [pH, soil organic matter, nitrogen (N), phosphorus (P) and potassium (K) contents], and microbial (microbial biomass and microbe quantity) properties and soil enzyme (catalase, protease and urease) activities were determined. Compared to the soils collected from other vegetation types, the soil under Leucaena leucocephala had the highest content of soil organic matter, total N, available N, total P, available P, available K, microbial biomass carbon (C), and the highest microbe quantity and enzyme activities. Five parameters (organic matter, pH, microbial biomass N, total K and protease activity), which had the greatest weight in the principal components analysis, were selected to calculate the soil quality index (SQI). The final SQI values implied that restoring Leucaena leucocephala greatly improved the soil quality, while restoration with Eucalyptus camaldulensis decreased the soil quality of the slope area. Plant recovery with Dodonaea viscosa and Heteropogon contortus on the gully bed affected the population of soil microbial communities but didn't improve the SQI values. It can therefore be seen that types of plants used for recovery in gully-developed regions in dry-hot valleys must be chosen cautiously: Leucaena leucocephala is a good choice for soil revegetation of the slope area, but the revegetation patterns on the gully bed still need further study.

Healthy soils are vital for food production as 95% of global food production directly or indirectly depends on soils. To ensure the food security of the burgeoning world population, it is necessary to evaluate soil health (SH) with a potential soil health index (SHI). Although there are several reputable methods for SH assessment at present, the connotations of and evaluation methods for SH are still unclear and such indexes are targeted at specific stakeholders or problems. In this study, we reviewed the fundamental steps in current attempts to develop SHIs, SH assessment methods and proposed a unified SHI based on the priorities of stakeholders. The proposed approach was designed as “three sets of dual index systems”, including the soil function (i), nutrition (j), and output (k) index systems, as well as the current (C) and expected (E) values of the respective index systems. The indicators included in index-i, index-j, and index-k reflect the soil regulatory functions, nutrient status, and quality and quantity of the output, respectively. The E values are used as a reference for the C values, and the health status is obtained, by using the ratio (R) of C to E for the respective index systems and their degree of deviation from “1” (R-1). For any evaluated soil, the farther the number of attributes and their ratios deviate from “1”, the unhealthier it is. This approach can provide a unified and comprehensive SH assessment method by diagnosing the most significant, healthy as well as unhealthy indicators. This method can be applied easily, not only by scholars but also by farmers and land managers.