Forest ecology

Forest ecosystems are critically important to biodiversity and the global carbon budget. Within forest ecosystems, dead wood has several ecological roles, including in carbon and nutrient dynamics and biodiversity conservation. However, surface fuels in forests also influence wildfire behavior and associated risks and hazards. Therefore, appropriate management of dead wood contributes directly to appropriate functioning of the forest ecosystem by conserving forest biodiversity, mitigating extreme wildfire events and pyrogenic emissions, and enhancing carbon sequestration. Using data extracted from peer-reviewed journal articles, geospatial, and field inventory data, and integrating meta-analytic, hierarchical regression, and vegetation simulation modeling approaches, this dissertation project examined the influence of dead wood on biodiversity, carbon, and wildfires in forest ecosystems.
The meta-analysis results suggest that dead wood quantity is an indicator of forest biodiversity, while dead wood types and decay stages had varied relationships with biodiversity. Generalized linear and additive mixed effects modeling of geospatial and human observed data demonstrated the predominant influences of weather conditions and moderate effects of live and dead fuels on exceptionally large wildfires’ behavior in the western United States. Consistently dominant effects of temperature on wildfire behavior highlight and emphasize the pressing need to address climate change's impact on western US forests. Lastly, vegetation and wildfire simulation modeling of forest stand inventory data and post-modeling carbon computations suggested that physical harvesting of dead wood, an approach analogous to traditional practice of firewood collection, when combined with modern mechanical fuel reduction treatments in Sierra Nevada, CA, mixed conifer forests has great potential to mitigate wildfire hazards, reduce fire emissions, and enhance carbon sequestration.

The Brazilian pepper tree (BP, Schinus terebinthifolius), introduced to the United States
in the 1800s, has since become a category one invasive plant in Florida, aggressively
spreading to 3000 km2 of prime habitat. There is a serious dearth of knowledge on
whether the rhizobiome plays any roles in the displacement of native flora and the range
expansion of BP. This thesis discusses the well-established plant invasion mechanisms of
the BP and highlights key emerging mechanisms and gaps in (a) the current
understanding of the molecular, below-ground processes of BP invasion and (b) studies
on the potential role of microbial interactions in the success of BP invasion already
established for other select invasive species, and the intervention of soil metagenomic
studies to elucidate plant invasive mechanisms. These poorly studied mechanisms could further explain the aggressive spread and resilience of BP and contribute significantly to
the development of effective and sustainable control measures, enabling appropriate
strategies for restoring native plants.