Wu Ma

Date of Graduation

2016

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Forest Resource Management

Committee Chair

Mo Zhou

Committee Co-Chair

Alan Collins

Committee Member

Jonathan Cumming

Committee Member

Jingjing Liang

Committee Member

Jingxin Wang

Abstract

Despite the economic and ecological significance of oak-hickory forests in the Central Hardwood Region (CHR), major challenges are faced by both private and public landowners and policymakers due to the lack of reliable growth and yield models as well as the absence of useful tools for multi-criteria management. Moreover, the effects of climate change and fire disturbance on these forests and their management are largely unknown.;The second chapter of the dissertation is directed towards the study of the community and population structure of CHR forests under climate change and associated changes of fire regimes. The Central Hardwood Region of the United States constitutes one of the most diverse ecoregions in North America and the most extensive temperate deciduous forest in the world. Despite the economic and ecological significance of the CHR, the long term effects of changes in climate and fire regime on forest structures remain largely unknown. In this study, we developed an integrated climate sensitive matrix framework to synchronously couple (1) forest dynamics, (2) mean fire interval, (3) population density, and (4) future climate scenarios to study the community and population structure of CHR forests under climate change and associated changes of fire regimes. Using Monte Carlo simulations and coupled forest dynamics-disturbance models, we projected that the CHR would undergo a major shift in population structure from the present to year 2100. The fundamental changes would consist of a transition of dominant species from oak and hickory to maple species, reduced species diversity, and substantial declines in stand basal area and stand volume compared to year 2010. These projected changes may have profound ecological and economic implications. Ecologically, changes in tree species diversity favoring maples would alter ecosystem processing of nutrients and subsequent nutrient flows to drainage waters within the region. Habitat change would alter the broad spectrum of organisms relying on the forest, leading to a redistribution of wildlife species, further heightening the risks for endangered species. On the brink of these fundamental shifts, our study calls for ecologically and economically informed conservation and mitigation strategies to better prepare society for the associated changes in ecosystem services and economic benefits derivable from the CHR forests.;The third chapter further addresses assessments of management impacts on central hardwood forests under climate and fire uncertainty. Central hardwood forests, in the absence of management, are predicted to undergo a species shift and decline in stocks due to climate change and increased fire frequencies. Here I quantified how various management intensities would influence these forests in terms of the net present value (NPV) of harvests, tree species and size diversity, and carbon stocks in four pools: above-ground biomass, fine roots, dead organic matters, and soil. An uncertainty analysis with fuzzy sets shows that when considering uncertain climate and fire, the NPV, size diversity, and total carbon stock would be distinctively different in climate scenarios RCP2.6 and RCP8.5 with high certainty. However, for species diversity, similar climatic effects on species diversity may exist across most management regimes.;The fourth chapter focused on modeling multi-stage scenario-based optimization under uncertainty in climate-induced fire disturbance. I developed multi-stage scenario-based optimization models for managing central hardwood forests under uncertainty in climate change and associated fire regimes. Based on a climate-sensitive matrix growth model and a mean fire interval model, four future climate scenarios and attendant fire intervals combined with two fire severity regimes were transformed into 36 and 20 tree growth scenarios for harvesting cycles of 10 and 20 years, respectively. Three alternatives of optimization formulations were proposed: 1) optimize for the maximum objective value under each individual scenario independently; 2) based on results from (1), find the compromise management plan that's feasible for all scenarios while minimizing the weighted sum of deviations between the realized and maximum objective values; and 3) derive the optimal management plan over the entire scenario tree. Four objectives were considered: the net present value (NPV) of harvests, total carbon stock, tree species diversity, and tree size diversity. Finally I determined the trade-off between economic and ecological benefits by quantifying the opportunity cost of increasing ecological benefits in terms of NPV. (Abstract shortened by ProQuest.).

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