Southwestern Borderlands Grassland Ecosystem Restoration
Investigators (most current known information)
Proposal Abstract
Vegetation features and rodent communities were compared between manipulated and nonmanipulated ranges in southeastern Arizona during summers 1996 and 1997. Two-way analysis of variance were used for all comparisons and identified relationships between rodent species richness or population size between mechanically treated and control areas (P greater than 0.10) or (P = 0.10). Two kangaroo rat (Dipodomys) species exhibited contrasting relationships with increasing grass cover. Rodent species richness and population size were greater on ungrazed compared to grazed areas (P less than 0.10). Prescribed fire did not have an obvious impact on rodent species richness or populations size, though kangaroo rats may have increased following the burn.
During winter 1996-1997 and summer 1997, we studied bird assemblages along a vegetation gradient in desert grasslands of southeast Arizona and southwest New Mexico. A gradient of increasing woody cover and decreasing grass cover best described the variance in vegetation characteristics among sites. At larger scales of observation, we found woody plant characteristics had a large effect on the presence and distribution of individual species and assemblages. At finer scales of analysis, we found a greater proportion of relationships between birds and particular plant species. Bird species richness was positively related to shrub species richness during winter. We observed greater between season shifts in bird species richness among sites with greater than 1.0% woody cover. Total bird abundance varied little between seasons except at sites with less than 1.0% woody cover. Woody plant levels below 10% and 20% are likely to increase populations of plains and semidesert grassland bird communities respectively.
Outcome
M.S. Theses
Downard, G.T. 1998. Status and management of sensitive grassland birds: Bird-habitat relationships along a vegetation gradient in southeastern Arizona and southwestern New Mexico. Southwestern Borderlands Grassland Ecosystem Restoration Project. M.S. Thesis. The University of Arizona. Tucson AZ.
Fitzgerald, C.S. 1997. Potential impacts of rangeland manipulations on desert rodent communities. Southwestern Borderlands Grassland Ecosystem Restoration Project. M.S. Thesis: The University of Arizona, Tucson AZ.