The characteristics of plant species and soil quality in the restoration process of the Loess Hilly Region

Using the methods of comparative analysis and substituting temporal serial with spatial serial, the changing characteristics of plant communities biomass and soil nutrient in the process of plant restoration were studied based on the survey data of abandoned lands in the Loess Hilly Region with the five different ecological restoration periods (0-5,6-10,11-15,16-20,and 21-25 years). The results showed that the main dominant species in the Loess Hilly Region with these five plant restoration periods were Leymus scalinus, Artemisia scoparia, Lespedeza davurica, Stipa bungeana and Bothriochloa ischaemun, respectively. Generally, Simpson index, Shannon-Wiener index, Pielou index and Margalef index increased firstly and then decreased which suggested that the ecological system in the Loess Hilly Region can gradually improved by both natural and artificial restoration modes. With the increase of restoration period, the aboveground biomass, soil organic matter, total nitrogen and available nitrogen content decreased firstly and then increased, however, the total phosphorus content changed in opposite way. The soil nutrient contents in different layer decreased with soil depth (0-20 cm, 20-40 cm, 40-60 cm) increased. Soil organic matter and total nitrogen reached the peak in area with the 21-25 years restoration period and total phosphorus content reached the peak in area with the 16-20 years restoration period which indicated that the content of soil nutrient in the Loess Hilly Region can be gradually improved with low speed.