LTREB: A Mechanistic Understanding of Ecosystem Resilience and Recovery In Seasonally Dry Tropical Forest Experiencing Disturbance

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Tropical forests provide habitat for countless organisms and help to protect the Earth’s climate by storing large amounts of carbon in trees and soils. Many of these forests are secondary forests that have regrown after being cleared for cropping or grazing. Secondary forest regeneration in the tropics is not fully understood. This makes it difficult to predict how the characteristics of tropical forests change over time and how quickly they regain important functions like biodiversity conservation and carbon storage. Long-term studies that track the birth, growth, and death of trees and measure other changes as forest ecosystems regrow are necessary to understand how forests change as they develop. This project extends long-term field measurements of forest regeneration in plots of seasonally dry forest in Costa Rica that have different ages and soil types, and then uses these insights to improve biologically realistic simulation models of forest growth. These results have a wide range of applications, from improving restoration projects for carbon storage to simulating the future state of tropical forests under a range of climate scenarios. The core data from this project will be used in an online learning module about tropical ecology for undergraduate students.Long-term data are critical for understanding ecosystem change over time. Eighteen forest plots were established across successional and soil gradients in Guanacaste, Costa Rica, and have been measured continuously since 2008. The plots encompass spatial gradients in soil characteristics and large inter-annual variability in climatic conditions, including the strongest drought on record. Forest plots experienced variable mortality in response to the extreme drought of 2015 and are in various stages of recovery. This project extends measurements of the key response variables of biomass, litterfall, tree and woody vine composition and demography, soil biogeochemistry, and frass fall (as an indirect proxy for Lepidoptera larvae abundance) to test five hypotheses addressing biotic and abiotic controls on successional processes as well as the resistance and resilience of dry forest to extreme climate events. This project will generate new fundamental knowledge on how tropical dry forests change through time and space in response to disturbance from land use and drought as well as the roles of two key groups, nitrogen-fixing legume trees and woody vines in mediating these processes. All data, model output, and model code will be freely available to the scientific community in online repositories.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.