Article Mid-Scale Drivers of Variability in Dry Mixed-Conifer Forests of the Mogollon Rim, Arizona Matthew Jaquette 1, Andrew J. Sánchez Meador 1,* , David W. Huffman 2 and Matthew A. Bowker 3 1 School of Forestry and Ecological Restoration Institute, Northern Arizona University, Flagstaff, AZ 86011, USA;
[email protected] 2 Ecological Restoration Institute, Northern Arizona University, Flagstaff, AZ 86011, USA;
[email protected] 3 School of Forestry, Northern Arizona University, Flagstaff, AZ 86011, USA;
[email protected] * Correspondence:
[email protected]; Tel.: +1-928-523-3448 Abstract: The structure and composition of southwestern dry mixed-conifer forests have changed sig- nificantly, decreasing forest resiliency to uncharacteristic disturbances which also threaten ecosystem services. Restoration of these forests can be informed by historical conditions; however, managers and researchers still lack a full understanding of how environmental factors influence forest conditions. We investigated historical and contemporary variability in dry mixed-conifer forests in northern Arizona and identified important environmental drivers. We utilized forest sample plots and den- drochronological reconstruction modelling to describe forest conditions in 1879 and 2014, respectively. We used correlogram analysis to compare spatial autocorrelation of average diameter, basal area and tree density, and structural equation modeling to partition the causal pathways between forest structure, forest composition, and a suite of environmental factors reflecting climate, topography, and soil. Historical (1879) reconstructed forests had significantly fewer trees, lower basal area, and Citation: Jaquette, M.; Sánchez Meador, A.J.; Huffman, D.W.; Bowker, higher average diameter than contemporarily (2014). Composition has shifted from ponderosa M.A. Mid-Scale Drivers of Variability pine dominance towards a more mixed-species composition.