LTREB renewal: Climatic change and community organization across three trophic levels: long-term research at a sentinel site in semiarid north-central Chile

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Increases in semi-arid and arid lands may affect economic stability and societies globally. This long-term project examines the shifting forces that influence a semi-arid community and thus serves as an important sentinel for societal ramifications of increased aridity with climate change. Since 1989, unexpected changes in rainfall patterns and species invasions have replaced native species interactions as key drivers of a semi-arid thorn scrub community in northern Chile. Long-term ecological data from this site contribute directly to decisions on wise management of these changing environments. It also will provide information to help the general public understand the decision-making process by improving their knowledge of its wildlife and natural areas. The project will provide important comparisons with ongoing research in semi-arid sites in North America, where important drivers of long-term change differ. The project represents a long-term collaboration between US and Chilean researchers and managers, and will provide valuable opportunities for US students to participate in international research. This long-term field project utilizes 20 experimental grids in which small mammals and ephemeral plants are sampled monthly, cover by shrubs is measured every three months, soil samples are taken every 4 months to estimate seed density, and fox owl diets are assessed. Previous results document the effects of predators on small mammals and plants that were overwhelmed by El Niño‐associated rainfall. Based on predictions of more frequent and intense El Niño events as a consequence of ongoing global climate change, the project will emphasize the dual and interactive roles of climate change and invasive species (lagomorphs, numerous ephemeral plants) on community-level dynamics in this habitat. Data collected over the next five years will be analyzed to answer three important questions: 1) will a major El Niño event in the next 5 years reverse the trends that have been apparent since 2002, or has a critical transition occurred that will be stable for the foreseeable future? 2) what further changes may ensue from the apparent decline in perennial shrub cover and an increase in invasive vegetation since 2003? and 3) what will be the consequences of these changes for the north-central Chilean semiarid zone more generally? These goals are facilitated by extensive collaboration with multiple investigators in Chile, Spain, and the United States. This research integrates population, community, and geographical ecology in the context of global climate change and predicted vegetative responses, spans 3 trophic levels, and provides important insight into the relative importance of biotic vs. abiotic factors, and top-down versus bottom-up control in semi-arid systems.