Impact of ecological restoration of rocky desertification on soil biodiversity in karst area: A review

Abstract

Karst region in southwestern China is an ecologically fragile area with slow pedogenesis, shallow soil layer, discontinuous soil cover structure and low water holding capacity. Excessive human disturbances and improper land uses led to land degradation, even serious rocky desertification. From the 9th to the 13th Five-Year Plan, the ecological restoration measures have been applied widely to suppress and reverse rocky desertification, and the related researches have been increased drastically in recent years. The " 14th Five-Year Plan" in China will advance scientifically the comprehensive management of rocky desertification, so as to improve the self-repair capacity and the stability of vulnerable karst ecosystem. This paper reviewed the impacts of ecological restoration measures on the diversity of soil microorganism, protozoa, nematode, micro-arthropod and earthworm in karst areas. The results showed that: (1) the diversities of bacterial and fungi were higher in the karst habitat than those in the non-karst habitats, which may be caused by higher pH and calcium content of the karst habits. (2) There were no significant differences in fauna group number between karst and non-karst habits, but the densities of soil fauna were significant lower in the karst habit than those in the non-karst habits. (3) The rocky desertification, as the extreme degradation process in karst area, reduced the microbial species and function diversity. Also the faunal density and group number showed a decline trend. (4) The ecological restoration measures changed the vegetation structure, increased the vegetation coverage and soil fertility, and then gradually increased soil microbial biomass, enzyme activities, and fungal/bacterial ratio, consequently favored soil carbon sequestration and ecosystem restoration. Furthermore, the ecological restoration measures increased the faunal density and group number. In conclusion, the soil biodiversity can be used to indicate the degradation process or ecological restoration process in karst area. In the future, we suggested that: (1) besides the traditional classification and identification of soil biota, some novel technologies such as metagenomics, metaproteomics, and isotope probing techniques should be involved in the researches of the degradation or ecological restoration process in karst area. (2) Strengthening the function study of soil biodiversity in the ecological restoration. And (3) by building long-term field ecological observatory stations, to study the real response of soil biodiversity to the ecological restoration process. These further studies would make important contribution to the clarification of the maintenance mechanism and ecosystem functions of soil biodiversity, and promoting ecological restoration of the degraded karst land.