Assessing the factors influencing forest regrowth in South America

By Zillah Calle

Abstract
Understanding forest regrowth dynamics on a continental scale is crucial for climate modeling, sustainable forest management, and climate change adaptation. This thesis investigates the environmental factors influencing regrowth across South America, filling a gap in existing research primarily focused on national and biome levels. Using global remote sensing data, this thesis examines above-ground biomass (AGB) and forest cover across eight biomes in South America.
The study area encompasses regions where forests are regrowing following disturbances between 2000 and 2017. The factors, maximal temperature (Tmax), precipitation, downwelling short-wave vegetation (SW↓), slope, aspects, soil pH, sand content, time since disturbance, fire frequency, and longitude were examined. The study employed a linear mixed model for South America and biome-specific linear models to identify factors impacting regrowth at various spatial scales. At the continental level, slope and precipitation emerged as primary positive influencers on AGB, while Tmax and precipitation were key positive factors for tree cover. Fire frequency and SW↓ were key negative influencers for both AGB and tree cover. Factors like Tmax, SW↓, and time since disturbance exhibited varied impacts across biomes, unlike precipitation, fire frequency, and slope, which showed consistent effects. Unexpected findings included the positive impact of slope on both above ground biomass and tree cover, and the unexpected negative effect of time since disturbance on tree cover. These results underscore the necessity of considering the diverse biomes and scales when evaluating forest regrowth dynamics. Additionally, the study emphasizes the evolving patterns of forest regrowth in the face of climate change, providing valuable insights for guiding sustainable forest restoration efforts.