Abstract:

We selected arable areas with different years of abandonment (1 a, 2 a, 4 a, 8 a, 13 a, 20 a, 30 a, 40 a, and CK) as research objects and used the space-time substitution method to analyze the vegetation community and soil physical-chemical characteristics during the restoration period at the Qingtu Lake. Our results showed that 15 plant families, with 29 genera and 43 species appeared in our plots during the 40-year restoration process, with most species belonging to a few plant families and few species belonging to one dominant plant family. We divided the vegetation restoration process into four stages. The first rapid-recovery stage (grain for 1a to 2 a) is composed of annual and perennial root herbs; the second stage (grain for 2 a to 8 a) is composed of annual herbaceous and perennial herbaceous plants; in the third stage (grain for 8 a to 20 a), perennial herbaceous and perennial shrub are the most common species; and perennial shrubs dominate the fourth final succession stage (grain for 20 a to 40 a). In areas where farming activities were more intensive, the soil-water content was more volatile, with increasing and decreasing periods. In the final succession stage, the topsoil layer had more moisture in compasrison to the lower-soil layer. Independent of the restoration stage, the proportion of fine sand grains was the largest, followed by the proportion of powder grains, whereas the proportion of coarse sand grains and clay grains were the smallest, and these particle proportions did not change depending on time and intensity of farming activities. We observed that according to the intensity of the farming activities, both total nitrogen and organic matter showed a downward trend. Still, the soil’s available potassium first increased and then decreased, whereas the available phosphorus showed the opposite trend. The surface aggregation phenomenon was evident. Finally, the succession of the vegetation community was closely related to soil physical-chemical properties. The Margalef richness index positively correlated with total soil nitrogen and organic matter, whereas the Shannon diversity index positively correlated with soil bulk density and fine sand particles and negatively correlated with soil clay and silt particles. The 4th year of the return of farming activity was crucial in the recovery process at Qingtu Lake.

Key words: Qingtu Lake, abandoned land, vegetation community characteristics, soil physical and chemical properties