Effects of tree size and forest structure on forest dynamics
Abstract
Climate change is exacerbating drought disturbances, reducing forest productivity, and causing increased forest mortality. Manipulating tree size and overall forest structure are two important components that are being considered by forest managers to help combat losses in forests. When it comes to tree size, however, there are inconsistent findings on which sizes are most vulnerable to drought; and when it comes to forest structure, there are inconsistent findings on whether stand structural diversity (SSD) is beneficial for promoting productivity. We conducted two meta-analyses to help better understand these factors, one for tree size and one for forest structure. Based on our results, we found that both tree size effects and forest structure effects are highly complex and rely on multiple biotic and abiotic factors. Notably, for tree size effects on drought induced mortality, we discovered that larger trees are initially more resistant to drought but become more vulnerable during longer droughts. They also tend to show higher mortality during drought from increasing insect disturbances. For forest structure, we found that increased SSD increases productivity in stands with larger average tree size, higher basal area, higher average temperatures, and higher levels of drought. My results indicate that forest managers will need to consider the specific factors that affect tree size and forest structure if they want to effectively manipulate forest structure and tree size to manage forests in the future.
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- OSU Theses [15752]