Rapid changes in nutrient availability in a Mediterranean forest due to simultaneous effects of simulated climate change and exotic pathogens

Póster (TS.14-P-7) presentado en el 1st Meeting of the Iberian Ecological Society & XIV AEET Meeting: Ecology an integrative science in the Anthropocene, celebrado del 4-7 de febrero de 2019 en la Universidad de Barcelona (UB), Barcelona, EspañaClimate change and exotic pathogens are two key global change factors driving the decline of Quercus species in forests worldwide. However, very little is known about the interactive effects of these two factors on biogeochemical cycles. Here, we assessed for the first time the consequences of the simultaneous impact of climate change and soil-borne pathogens on nutrient cycling. We conducted a field experiment in a Mediterranean forest affected by Quercus suber decline, evaluating how drought (ambient vs. ~30% reduction in rainfall), warming (ambient vs. ~2.5 °C increase) and the abundance of the oomycete pathogen Phytophthora cinnamomi affected nutrient availability in soils (microbial biomass nitrogen, NH4+, NO3-, and urease, phosphatase and ß-glucosidase activities). One year after the beginning of the experiment, the drought trea ment decreased by 19% the soil phosphatase activity in spring and caused substantial reductions in microbial biomass nitrogen and NH4+ (60% and 33%, respectively) in summer. Warming also caused very rapid changes in nutrient availability, increasing NH4+ concentration in summer by 38%. Moreover, P. cinnamomi abundance was positively correlated with urease and ß-glucosidase activities. We did not find any short term interaction between the climate treatments and P. cinnamomi abundance. Our findings suggest that drought can have a very rapid negative impact on nutrient cycling in Mediterranean forests that could be partially buffered by the effects of warming and P. cinnamomi infection. Climate change and soil-borne pathogens can have counteracting effects on nutrient cycling, supporting the need for more studies that analyze their simultaneous effect on ecosystem functioning.N