The trends of and relationships among the plant community, soil nutrients, and four soil enzymes were investigated after being abandoned for 10, 15, 20, 30, and 45 years to reveal the soil properties during the restoration in the Loess Hilly Region. The results indicate the following ranking of dominant plant community species:Artemisia scoparia→Lespedeza dahurica+Artemisia sacrorum→Artemisia giraldii+irons Artemisia annua→Bothriochloa flaccidum+Artemisia selengensis. The ranking reflects an increase along the chronosequence of abandoned land. Moreover, the ratio of the total species of Compositae, Poaceae, and Leguminosae decreases from 66.67% to 50% and then increases up to 75%. The SOC, TN, TP, AN, AP, and four enzyme activity types (ALP, CAT, UE, and SC) increase but respond differently to restoration, while the stoichiometric ratio fluctuates. In contrast to the number of plant families, genus, species, and plant diversity, Compositae, Poaceae, and Leguminosae have major effects on the soil nutrient and enzyme activity, which explains the total variation of 72.8%, 69.1%, and 66.0%, respectively. The effects of these three families on the soil enzymes are greater than that on soil nutrients. Poaceae and Leguminosae have a positive effect on the nutrient and enzyme activity, while the family Compositae has a negative effect. Overall, the changes of dominant species of grassland communities during restoration significantly affect the soil enzyme and thereby are responsible for the soil nutrient dynamics.
Keywords: Loess Hilly Region; abandoned land; enzyme activity; stoichiometry; vegetation community.