Date of Award

Fall 2023

Project Type

Thesis

Program or Major

Natural Resources

Degree Name

Master of Science

First Advisor

Mark J. Ducey

Second Advisor

Thomas D. Lee

Third Advisor

Gregory Nowacki

Abstract

Old-growth kauri (Agathis australis) dominated forests are highly diverse and species-rich, making their survival critical to maintaining global biodiversity. The ability to accurately quantify stand density in such complex forests is difficult, but important to their effective management and protection. However, studying mature versions of these forests today is unlikely due to extensive historic logging efforts and the recent onset of the prolific kauri dieback. Fortunately, an opportunity presented itself in the uncovering and reconfiguring of historic data collected across 25 old-growth kauri dominated stands by Ahmed and Ogden (1991a,b). I successfully determined the maximum stand density of these complex forests using the additive formulation of stand density index. The stands showed considerable variation in maximum stand density. Surprisingly, this variation is best explained by the interaction between structural complexity and species evenness (stems per ha), not functional traits or other species diversity measurements. This suggests that the horizontal and vertical distribution of stands may be important attributes to consider in accurately predicting stand density in similarly complex forests.

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