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Nitrogen deposition impacts on microbial abundance and decomposition in three Mediterranean sites: a coordinated study using the NitroMed network

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posted on 2016-08-11, 09:39 authored by Mauro Lo CascioMauro Lo Cascio, Raul Ochoa Hueso, Lourdes Morillas, Esteban Manrique Reol, Silvana Munzi, Donatella Spano, Cristina Cruz, Teresa Dias, Antonio Gallardo Correa, Manuel Delgado-baquerizoManuel Delgado-baquerizo, Javier Roales, Simone Mereu

 Mediterranean and semi-arid ecosystems are underrepresented in global networks, including those focusing on the effects of nitrogen (N) deposition on ecosystem structure and processes. The establishment of networks of experimental sites is a crucial strategy to answer global ecological questions related to the prediction of ecosystem functioning under changing environments and the formulation of sustainable natural resource management policies. NitroMed is a recent network composed of three N manipulation experimental sites, namely Arrábida (Lisbon, Portugal), El Regajal (Madrid, Spain) and Capo Caccia (Alghero, Italy). All three sites present similar characteristics: i) they are all located in a Mediterranean biome and include similar vegetation types; ii) they host long-term experiments (>5 years); and iii) they are subject to added N loads similar to those predicted for the Mediterranean Basin during this century. The main goal of NitroMed is providing “field laboratories” to investigate the effects of N pollution and climate change on structure and functioning of Mediterranean ecosystems sharing protocols, experimental design and, whenever possible, equipment. Herein we present preliminary analyses using data from the current NitroMed network aiming to understand the cause-effect mechanisms that determine changes in decomposition and stabilization rates in response to different N loads. Our results suggest that N deposition increases soil N availability and reduces soil pH, which in turn has an effect on microbial community structure (lower fungi to bacteria ratio) and overall enzymatic activity, responsible for decomposition rates. Our findings also show how site-specific heterogeneity can greatly influence ecosystem processes, highlighting the importance to increase the number of experimental sites in the NitroMed network.

Funding

Euro-Mediterranean Center on Climate Change (CMCC)

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