The impacts of nutrient addition and livestock exclosure on the soil nematode community in a degraded grassland

Nutrient addition and livestock exclosure are two strategies for restoring degraded grassland. Although their impacts on plant community properties are well understood, the effects of fertilization and livestock exclosure on belowground fauna community in degraded grassland remain largely unknown. We examined the main and interactive effects of nutrient addition and livestock exclosure on soil nematode community in a severely degraded grassland of northern China, by recording soil nematode community composition in 0- to 10-cm soil layer in the summer of 2017. Neither nutrient addition nor livestock exclosure had significant effects on the biodiversity of nematode community in this degraded grassland. Livestock exclosure significantly increased the abundances of total nematodes and the maturity index of the nematode community, mainly due to its positive effect on omnivorous + carnivorous nematodes. Nutrient addition weakened the positive effects of livestock exclosure on soil nematode community by reducing soil pH and enhancing soil ammonium concentration. Our results highlight that the positive effects of livestock exclosure on soil nematode community would be reassessed under the scenarios of nutrient enrichment. Given that most grasslands are used for livestock production, the interactive effects of grazing and nutrient enrichment on soil nematode community deserve more attention in further research.