Biocrusts control the nitrogen dynamics and microbial functional diversity of semi-arid soils in response to nutrient additions

12 páginas.- 4 figuras.- 2 tablas.- referencias.- Electronic supplementary material The online version of this article (doi:10.1007/s11104-013-1779-9) contains supplementary material, which is available to authorized users .- Texto completo en https://maestrelab.com/wp-content/uploads/2015/10/Plant_Soil2013c.pdf

Aims Human activities are causing imbalances in the nutrient cycles in natural ecosystems. However, we have limited knowledge of how these changes will affect the soil microbial functional diversity and the nitrogen (N) cycle in drylands, the biggest biome on Earth. Communities dominated by lichens, mosses and cyanobacteria (biocrusts) influence multiple processes from the N cycle such as N fixation and mineralization rates. We evaluated how biocrusts modulate the effects of different N, carbon (C) and phosphorus (P) additions on theN availability, the dominance of different available N forms and the microbial functional diversity in dryland soils. Methods Soil samples from bare ground (BG) and biocrust-dominated areas were gathered from the center of Spain and incubated during seven or 21 days under different combinations of N, C and P additions (N, C, P, N + C, N + P, P + C, and C + N + P). Results The relative dominance of dissolved organic N (DON) and the microbial functional diversity were higher in biocrust than in BG microsites when C or P were added. Changes in the C to N ratio, more than N availability, seem to modulate N transformation processes in the soils studied. In general, biocrusts increased the resilience to N impacts (N, C + N, N + P, C + N + P) of the total available N, ammonium, nitrate and DON when C was present. Conclusions Our results suggest that biocrusts may buffer the effects of changes in nutrient ratios on microbial functional diversity and DON dominance in dryland soils. Thus, these organisms may have an important role in increasing the resilience of the N cycle to imbalances in C, N and P derived from human activities.

This research is supported by the European Research Council (ERC) under the European Community’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement n° 242658 (BIOCOM) and by the Ministry of Science and Innovation of the Spanish Government, Grant n° CGL2010-21381. M.D.B was supported by a PhD grand from Universidad Pablo de Olavide.

Peer reviewed