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Abiotic and Biotic Factors Shaping Seed-Rain and Seedling Establishment Regenerating Tropical Forests in Human-Modified Landscapes

Nohemi Huanca Nunez, University of Nebraska - Lincoln


Over 50% of the remaining forested area comprises secondary forests regrowing following human disturbance. Still, the dynamics, drivers, and outcomes of successional processes in tropical forests remain poorly known. Here, I focus on how processes affecting early life stages shape regeneration of wet tropical forests. First, I developed the concept of seed-rain–successional feedbacks (SRSF) in forest fragments, defined as a deterministic process in which existing reproductive trees have a greater influence on the fragment’s seed-rain than do external seed sources. I tested the strength of SRSF relative to other deterministic and stochastic mechanisms. I found that SRSF increased in strength with successional age concluding that the deterministic assembly generated by SRSF likely contributes to the increasing divergence in community structure that we observed in these regenerating secondary forests. Second, I examined how mammalian seed and seedling predators and herbivores affect the establishment of seedlings during succession. I found that the effects of mammals on seedling survival and abundance depended on successional age and species' successional niche, which translated into significant shifts in seedling community structure of secondary and mature forests. I concluded that plant-animal interactions are important not only for diversity maintenance, but also for shaping successional trajectories. Finally, I compared changes in community structure of seedlings and trees during succession and evaluated the effects of water stress and the role of successional niche as drivers of these changes. I found that seedlings and trees' structural changes depended upon the successional niche. The vulnerability to water stress was determined by three successional driven factors operating across levels of biological organization: the size class of the individual, the successional niche of the species, and the successional age of the forests. As droughts worsen with climate change, water stress may have an outsized role in the regeneration dynamics of tropical forests. Overall, this dissertation illustrates the pivotal role that processes affecting early life stages have on the trajectory of the nowadays more prevalent regenerating human-modified landscapes.

Subject Area

Ecology|Forestry|Plant sciences

Recommended Citation

Huanca Nunez, Nohemi, "Abiotic and Biotic Factors Shaping Seed-Rain and Seedling Establishment Regenerating Tropical Forests in Human-Modified Landscapes" (2022). ETD collection for University of Nebraska-Lincoln. AAI29167367.