Potential of alfalfa as pioneer plant for ecosystem recovery in semiarid Horqin Sandy Land, Northern China.
The ecosystem of the Horqin Sandy Land in Inner Mongolia, China, is threatened by desertification during recent decades. As a result of land degradation, an exotic weed Cenchrus pauciflorus Benth has spread throughout the Horqin region since the early 1980s, causing severe damage to the agriculture, grasslands and livestock. The establishment of technology that can control weeds and restore vegetation is an urgent issue in this region. In this study, a native perennial legume with strong drought tolerance was tested as a pioneer plant. We have planted Aohan, a local variety of alfalfa (Medicago sativa L. cv. Aohan) in 2015 and found that this plant has profound effects on soil amelioration, weed suppression and vegetation restoration. Soil properties such as the moisture, organic matter, clay contents and cation exchange capacity were significantly increased, and the sand content decreased after alfalfa establishment. The coverage of above-ground biomass seemed to trap and sequestrate fine particle such as clay, and the root could stabilize coarse particles like sand, which consequently improved soil properties. The aboveground biomass was 1.6-20 times to the typical biomass of grasslands in Inner Mongolia, indicating alfalfa plantation on sandy land can supply sufficient forage production. The variety of plant species increased to 23 after 4 years, and 22 of them are local species. The large quantities of alfalfa shoot accumulated seeds, resulting in increased species diversity at the experimental site. The significant increase in plant species over a short period also indicated that alfalfa can be an effective pioneer plant for vegetation restoration in the Horqin Sandy Land. Moreover, no Cenchrus pauciflorus Benth was observed in the study site except the edge area, suggesting that Aohan successively suppressed the invasion of this weed. The results suggested that the establishment of this native shrub is an effective measure for both Cenchrus pauciflorus Benth control and vegetation recovery in the Horqin Sandy Land.