Fertilization influences the nematode community through changing the plant community in the Tibetan Plateau

Fertilization greatly impacts grassland ecosystems as it alters plant communities, soil fauna, and microbiota although few studies have looked at these interactions on the Tibetan plateau. Soil nematodes are ideal bioindicators for the status of below-ground ecosystems. To explore how nematode communities are impacted by the use of fertilization, we studied the top layer of soil in land that had been fertilized annually with diammonium phosphate for over 10 years. We tested effects of long term fertilization treatment at 300, 600 kg ha(-1) yr(-1) (F300, F600) compared to unfertilized control (F0) on soil nematode community at the 0-15 cm depth. Soil samples for analysis of nematode community were collected on September 2012 and on September 2013. We show that fertilization was associated with increased plant and microbial biomass, and decreased plant biodiversity. Fertilization increased microbial biomass C and N; grass biomass and total plant biomass, but decreased plant species richness, plant community biodiversity and the biomass of sedges, legumes and forbs. Fertilization increased nematode communities increased over the entire course of the study. We show that the amount of fertilizer used and the duration of its use significantly impacted the dynamics and composition of nematode communities. The changes in nematode community were associated with both changes in soil factors and shifts in the plant community that were caused by fertilization. According to the structural equation model (SEM), fertilization had strong effects on soil microorganisms and plant community composition, whereas plant community was the main determinant of nematode community changes. Our findings highlight the importance of soil fertilization in regulating both plant and soil fauna communities, and provide a better understanding of the responses of plants and soils to fertilization and the linkages between structure and functioning of above-ground and below-ground in the Tibetan Plateau. Published by Elsevier Masson SAS.