Under climatic change, soil microbial community and variables relating to N-cycle are modulated by changes in the upper limit temperature

Abstract

The effect of temperature increase and more specifically its upper and low level correlates on soil microbial biomass, activity and N-cycle variables was studied in a Mediterranean shrubland. Experimental manipulation succeeded in establishing three treatments which, in comparison with the monthly ambient temperature, displayed an increase in mean monthly temperature by 2.1, 4.9 and 7.4°C respectively. Also the upper limit temperature values (T max), but not the low limit counterparts (Tmin), differed significantly among the three treatments. T max changes seemed to affect directly only the microbial biomass, while it exerted an indirect effect on the majority of the other soil variables. With increased T max the values of the estimated soil microbial variables (microbial biomass and activity) increased, while other soil chemical variables, such as the inorganic forms of N, were found reducing. Organic N was the only variable remaining independent from changing T max at any treatment. The results of this paper indicate that the level of T max increase could be crucial for the structure of the microbial community. A T max increase up to 7°C induced by climate change could favour the dominance of the soil bacterial populations, while larger increases could be in favour of the fungal populations. © 2011 Global NEST Printed in Greece. All rights reserved.