The effects of defoliation on plant community, root biomass and nutrient allocation and soil chemical properties on semi-arid steppes in northern China

Semi-arid steppes in northern China have severely deteriorated over the past 50 years, mostly due toimproper grazing management. A defoliation experiment was conducted on a Leymus chinensis-dominatedsemi-arid steppe to provide guidelines of grazing management and favor long-term restoration ofdegraded grasslands. There were five defoliation treatments: non-defoliation (no cutting during growingseason) as control; light defoliation (cut 15 cm above ground level); medium defoliation (10 cm); harddefoliation (5 cm) and severe defoliation (2 cm). Results showed that hard and severe defoliationsignificantly reduced the concentrations of soluble carbohydrates in rhizomes and fibrous roots anddecreased the belowground biomass and the ratio of below/aboveground biomass. Defoliation increasedplant species diversity, but decreased biomass of L. chinensis significantly. The biomass of L. chinensisunder light defoliation was lower than that in control, indicating L. chinensis was highly sensitive todefoliation. Defoliation intensity in general had no significant effect on soil chemical properties duringthe experimental period, suggesting that soil chemical properties might have a greater tolerance toshort-term heavy defoliation compared to plant community. However, prolonged intensive defoliationwould result in severe ecological consequences. Further studies are required to investigate the responseof soil chemical properties to long-term defoliation