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Spatial and temporal dynamics of disturbance interactions along an ecological gradient

Posted date: April 21, 2015
Publication Year: 
2013
Publication Series: 
Dissertations
Source: Tucson, AZ: University of Arizona. Dissertation. 204 p.

Abstract

Interactions among site conditions, disturbance events, and climate determine the patterns of forest species recruitment and mortality across landscapes. Forests of the American Southwest have undergone significant changes over a century of altered disturbance regimes, human land uses, and changing environmental conditions. Along steep vertical gradients such as those of southwestern Madrean Sky Island systems, where mountains rising out of the Sonoran Desert host biomes representing a latitudinal transect from Mexico to Canada, forests are especially vulnerable to changing dynamics of disturbances. In these vertically stacked systems, a change in one forest type can propagate changes into and across adjoining forest types. In the Pinaleño Mountains of southeast Arizona, a series of recent insect outbreaks and high-severity fires significantly reduced the extent of a remnant spruce-fir forest and raised concerns about the vulnerability of the surrounding forest to additional high-severity disturbances. A century of Euro-American influence and changes in longer-term climate patterns may have influenced the size and severity of recent disturbances by altering the species composition and structure of forests surrounding the spruce-fir system and increasing temperature and drought stress on overstocked forests. This study reconstructs the interactions between, fire, spruce beetle outbreaks, climate, and anthropogenic factors and their influence on the species composition, spatial extent, and structure of the four upper elevation forest types of the Pinaleño Mountains.

Citation

O'Connor, Christopher D. 2013. Spatial and temporal dynamics of disturbance interactions along an ecological gradient. Tucson, AZ: University of Arizona. Dissertation. 204 p.