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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - CCPaMe (Direct and indirect effects of Climate Change on biotic communities and exotic Pathogens in mixed Mediterranean forests)

Teaser

Summary

Mixed oak forest and rangeland ecosystems are the most representative ecosystems of the Mediterranean Basin. However, their persistence has been seriously threatened by Global Change. It is a complex phenomenon that involves several factors, highlighting climate change and biological invasions. Although each of these factors has been individually studied in detail in the last years, it is still poorly known how they could interact to affect biotic communities and the ecosystems processes that they control. CCPaMe aimed to elucidate the effects of climate change on biotic communities and their interactions with the invasive pathogen Phytophthora cinnamomi which is killing thousands of Quercus in Mediterranean forest systems. Three lines of research were pursued: 1) a study of the direct effects of climate change on P. cinnamomi population in field conditions; 2) an investigation of the interaction between tree species coexistence and climate change on different aspects of P. cinnamomi life cycle and 3) an investigation of the indirect effect of climate change on the soil biotic community and its interaction with P. cinnamomi infectivity. CCPaMe has accomplished these goals by a multidisciplinary approach by combining ecology, pathology and forestry. By means of several experiments in growth chambers and in field conditions using different infrastructures of climate change simulation, CCPaMe has generated several key results which supported the following conclusion: 1) Olea europaea var. sylvestris is susceptible to P. cinnamomi, also encouraging the production of resistant spores; 2) O. europaea var. sylvestris and Quercus canariensis induced autogamy of P. cinnamomi: 3) coexistent tree species of mixed Mediterranean forests negatively influence the epidemiology of the root disease: 4) in field, the highest P. cinnamomi population densities were recorded during spring regardless to the annual precipitation range and the climate change effect: 4) the most risk season for P. cinnamomi introduction is at the end of summer, when soil conditions were more favorable to the production of infective zoospores. So, as a main conclusion, our results do not support strong interactive effects of climate change and P. cinnamomi, however these two factors could act simultaneously limiting seedling performance, and seriously threaten the long-term conservation of Mediterranean forest ecosystems.

Work performed

CCPaMeâ€™s researcher and collaborators have enthusiastically worked during the 24 months of the Action to successfully achieve the objectives proposed as it described below:
We have conducted a field experiment of climate change simulation in an infested mixed Mediterranean forest located in Los Alcornocales Natural Park (CÃ¡diz, southern Spain), as well as, several in planta experiments under controlled conditions to determine the interactive effects of climate change and woody plant community on the exotic pathogen Phytophthora cinnamomi. In particular, CCPaMe have been focused on the variation of this pathogen population density in wild forests mediated by seasons and tree species coexistence. As main results of these experiments, spring was detected as the most favorable season for P. cinnamomi inoculum viability. Additionally, CCPaMe described to Olea euopaea var. sylvestris as a new host of P. cinnamomi which susceptibility might be age-related. On the most important research findings is that P. cinnamomi may act as facultative homotallic under the influence of Quercus canariensis and Olea euopaea var. sylvestris, two of the principal trees integrant of plant community of mixed Mediterranean forests. Moreover, tree species coexistence and climate change did not decrease the severity of root rot caused by P. cinnamomi.
On the other hand, by another field experiment of climate change simulation in three un-infested rangeland ecosystems located in areas of high risk of P. cinnamomi introduction, we determine the variation of P. cinnamomi infectivity mediated by soil properties and microbiota composition during the two years of Action. CCPaMe results showed that at the end of summer soil properties are more favorable for P. cinnamomi infectivity. Consequently, the preventive action to avoid P. cinnamomi outbreak should be focused on this season. Additionally, the effect of climate change on P. cinnamomi infectivity, although it only differs to the control conditions during summer, is high linked to annual precipitation range.
Some of the main results of CCPaMe have already been presented in four international (2) and national (2) meetings. CCPaMe has also been focused on outreaching activities, actively participating at the European Researchersâ€™ Night, â€˜Caffe with Scienceâ€™ centering on science dissemination to high schoolsâ€™ students, general public speeches to celebrate the Environmental Day (June 5th) and by a website. Additionally, CCPaMe has served to the researcher to supervise three Master students and two undergraduate students.

Final results

The main objectives of CCPaMe has been successfully accomplished contributing to the state-of-the-art of the epidemiology of the root rot caused by Phytophthora cinnamomi. We have described for the first time Olea europaea var. sylvestris as an unknown host of P. cinnamomi, which susceptibility might be plant-age mediated. Moreover, CCPaMe constitutes the first record of P. cinnamomi autogamy induced by roots of Quercus canariensis and O. europaea var. sylvestris. These results might revolutionize the life cycle of P. cinnamomi prior described at the Iberian Peninsula and consequently, the established strategies of root rot management.
On the other hand, it is the first time that an infrastructure of climate change simulation set-up in a forest is successfully used to evaluate the consequences of climate change on invasive pathogens dynamic. CCPaMe has generated valuable knowledge on plant performance and long-term persistence of mixed forests under the simultaneously influence of climate change and P. cinnamomi. These findings contrast with prior hypotheses of synergistic interactions between both driving factors.
One of our major contributions to the state of the art has been the establishment of the annual variation of sporangia production of P. cinnamomi in ecosystems favorable to root disease development. We concluded that control action to prevent pathogenâ€™s outbreak, should be focused on reducing soil appropriateness to sporangia and zoospore production mainly during summer. On the other hand, the interaction of climate change with P. cinnamomi infectivity is directly linked to the annual precipitation range. The mechanisms by which these patterns occur are not clear and needs further exploration, including the completion of soil microbiota analyses which are currently carrying out.
These results allow the possibility to expand this kind of studies conducted in CCPaMe to others Phytophthora species which are involved in Mediterranean ecosystems decline.