PARENT SESSION
Oral Session #48: Vegetation Change and Response.
Presiding: D. Zobel
Tuesday, August 6. 1:00 PM to 4:45 PM. Mesquite Room, Radisson.

Abiotic drivers of conifer forest expansion in the Greater Yellowstone Ecosystem.

Powell, Scott^*,1, Hansen, Andrew¹, ¹ Montana State University, Bozeman, MT

ABSTRACT- Forest dynamics in the Greater Yellowstone Ecosystem (GYE) are governed by a complex set of drivers that are distributed across the landscape at multiple spatial and temporal scales. One aspect of forest dynamics that is widespread across the GYE is an increase in the spatial extent and density of conifer forest. The objective of this study was to use partial Mantel's tests to determine the correlative relationships between abiotic variables and conifer forest dynamics. The spatial patterns of correlated variables were analyzed in conjunction with the rates and distribution of conifer forest change to interpret the driving mechanisms of forest dynamics. The predictor variables included in the study were temperature, precipitation, aspect, soil type, distance to nearest conifer stand, topographic convergence index (TCI), and solar radiation. Conifer forest change was quantified by interpreting 90m² plots from aerial photographs over a 60 year time period. The results of this analysis indicated that conifer forest dynamics were most significantly correlated with aspect, solar radiation, and distance to nearest conifer stand. Temperature and soil type were also strongly correlated with conifer dynamics, yet TCI and precipitation were not. Path diagrams were used to depict the significant correlations and interpret mechanistic drivers of conifer forest dynamics in the GYE. The significance of understanding these drivers is that it will ultimately enable a quantification of carbon source/sink dynamics and changes in patterns of biodiversity across the GYE.

KEY WORDS: conifer expansion, Mantel's test, Greater Yellowstone Ecosystem