Impact of N and P deposition on soil microfauna of high mountain systems of the Spanish National Parks network

Abstract

The main Global Change factors with larger impacts on high mountain ecosystems include climate change, land use change and nitrogen (N) deposition. In Spain, phosphorus (P) deposition coming from Saharian dust has also an impact in these ecosystems. Atmospheric deposition of these compounds can have large effects on nutrient cycling and soil biota. Nematodes are a key group of such biota, since they occupy multiple positions in the soil food web, play key roles in the ecosystem and are good indicators of soil condition. For three years, we have simulated N and P deposition in four alpine and sub-alpine systems along an aridity gradient and analyzed their effects on soil nematode communities and microorganisms. Fungi and bacteria communities reduced their presence with aridity buy only fungi responded to N deposition. Nematode communities also reduced their abundances with aridity, while N deposition increased nematode biomass due to the increase in bacterivore nematodes, and P deposition increased the contribution of microbivores simplifying the soil food webs. Fungivore nematodes were less sensitive than bacterivores to stoichiometric unbalances, and, in general, communities in arid sites were characterized by a prevalence of the bacterivore decomposition channel and a lower relevance of belowground herbivory. Global Change factors such as the increases in aridity and atmospheric N deposition, together with the potential increase in the deposition of Saharian P, could have long-term effects on the composition and structure of the Spanish high mountain soil food webs and on the ecosystem functions they provide.