Warm- and cold- season grazing affect plant diversity and soil carbon and nitrogen sequestration differently in Tibetan alpine swamp meadows

Abstract

Seasonal grazing is a traditional grassland management practice in alpine swamp meadows on the Tibetan Plateau, but little information is available on the interactions between plant diversity and soil carbon and nitrogen sequestration in warm- and cold- season grazed alpine swamp meadows. A multisite survey was conducted to investigate the plant characteristics and soil properties of Tibetan alpine swamp meadows under warm-season grazing (WG) and cold-season grazing (CG). Our study showed that plant biomass, litter mass, soil water content (SW), soil available nitrogen, soil microbial biomass carbon and nitrogen were significantly lower in the WG meadows than in the CG meadows (P < 0.05). However, plant diversity, species richness and the evenness index tended to increase in the WG meadows. Soil C and N storage were significantly lower in the WG meadows than in the CG meadows (P < 0.01). Grazing-induced changes in SW, plant diversity, plant biomass and litter mass were the major factors resulting in the decrease in soil C and N storage. Our results indicate that warm-season grazing is beneficial for species diversity conservation, whereas cold-season grazing is suitable for soil C and N sequestration in alpine swamp meadows. Grazing-induced changes in litter mass greatly contributed to variations in plant diversity and soil C and N storage. In view of the accelerated vegetation and soil degradation in alpine grasslands, periodic warm- and cold-season grazing strategies should be considered to maintain alpine swamp meadow sustainability.