COS 4-4 - Mechanisms mediating drought resistance in aseasonal tropical forests

Monday, August 7, 2017: 2:30 PM
B118-119, Oregon Convention Center
Michael J. O'Brien, Estación Experimental de Zonas Áridas, Consejo Superior de Investigaciones Científicas, Almería, Spain

Precipitation patterns are changing across the globe causing more severe and frequent drought for many forest ecosystems. Forest response to altered precipitation is the result of many factors including species tolerance to reduced water availability and interactions among plants that alleviate or exacerbate drought. Here I present the results from multiple rainfall manipulation studies whereby I altered drought frequency and severity for seedling communities in a tropical forest that, in recent history (i.e. the last 10 – 20000 years), has primarily experienced infrequent supra-annual droughts associated with El Niño Southern Oscillation events (ENSO).


This research has highlighted important mechanisms operating at the individual and community levels that mediate seedling responses to drought. At the individual level, seedlings exposed to recurrent periods of drought altered their growth rates throughout the year relative to seedlings in everwet conditions, which sustained overall annual growth rates. At the community level, seedlings growing in more diverse communities maintained growth rates under drought similar to everwet conditions while competition among conspecifics inhibited growth under the same conditions. These results suggest these communities can potentially adapt to predicted climate change scenarios and both plant–plant interactions and physiological plasticity of species contribute to population and community responses to drought.