Woodland patch mosaic structure and microclimate response to contemporary and historical disturbances.




Murray, Darrel B.

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In this study, changes in area and structure of Ashes’s juniper (Juniperus ashei)-dominated woody vegetation patches, growth response of an oak species codominant, and changes in interior patch microclimate in response to disturbance were investigated. A historical aerial photo analysis, a tree ring study, and microclimate monitoring were performed on woody vegetation patches within Balcones Canyonlands National Wildlife Refuge in central Texas. Aerial photograph analysis indicated that although overall woody vegetation area did not change considerably, configuration of patches was highly variable through time related to small and large-scale disturbance inferred from areas of woody vegetation loss. The tree ring analysis, performed on a within-patch co-dominant oak species, Texas red oak (Quercus buckleyi), indicated that climate, fire, and loss of neighboring woody vegetation were highly variable within the study area and influenced growth of oaks. Microclimate analysis indicated that protections provided by intact woody patch edges, including decreased wind and lower daytime temperatures and vapor pressure deficits, were only minimally reduced following disturbances that reduced edge vegetation. The overall results of these studies indicate woodlands in central Texas are influenced by disturbances at both patch and landscape scales. Disturbance drives variability within these systems, yet aids stability in the overall coexistence of woody patches within herbaceous areas.



Woodlands., Patch mosaic., Drought., Fire., Texas --- Balcones Canyonlands National Wildlife Refuge