• Response of Birds, Small Mammals, and Vegetation to Burning Sacaton Grasslands in Southeastern Arizona

      Bock, C. E.; Bock, J. H. (Society for Range Management, 1978-07-01)
      We studied the impact of fire on an ungrazed sacaton grassland community at The Research Ranch in southeastern Arizona. Two summer burns were followed through two post-fire growing seasons. A winter burn was studied through one post-fire growing season. Burning reduced the height and extent of sacaton grass (Sporobolus wrightii) itself, and stimulated growth of other grasses and forbs. Summer fires created more bare ground and encouraged a greater number and variety of annuals than the winter fire. The fires had the effect of reducing total small-mammal populations and greatly increasing bird populations. These results were more dramatic on the areas which burned in early summer than on the winter-burned plot. Raptors and most game birds, particularly mourning doves, were most abundant on one-year-old burns. Seed-eating birds (Fringillidae) preferred burned over unburned areas. Cotton rat (Sigmodon hispidus) populations were greatly reduced by the fires, while populations of seed-eating pocket mice (Perognathus) and kangaroo rats (Dipodomys) increased, especially on the summer burns. Sacaton grasslands recover rapidly even from summer burning, at least in the absence of livestock. Results of this study suggest that fire is beneficial to the indigenous plants and wildlife of sacaton communities, as long as a mosaic of different aged stands is maintained.
    • Runoff Water Quality from Varying Land Uses in Southeastern Arizona

      Schreiber, H. A.; Renard, K. G. (Society for Range Management, 1978-07-01)
      Surface runoff waters from three kinds of activity on rangeland were examined for suspended solids and some indicator chemical constituents. We compared ungrazed brush-covered rangeland with recently subdivided rangeland, originally and still partly brush-covered, but whose surface was disturbed by man's urbanizing influence. Water quality indicators showed the urbanized watersheds had poorer water quality. Comparisons between the two brush-covered watersheds and a third-grass-covered and grazed-were made only on the runoff water's dissolved constituents. Despite the grazing activity, the waters were of better quality. A contrast in the geology between the grass and brush areas suggested that mineral sources affected qualitative changes in the dissolved solids. Calcareous soils produced waters higher in Ca and total dissolved solids and lower in other cations. Phosphate in runoff averaged higher from the grass-covered, noncalcareous area than from the brush-covered calcareous watershed. We hypothesize now that the phosphate originated from soil sources, rather than from grazing activity. Nitrate levels were comparable in runoff from all the nonurban areas, but increased in runoff from the semiurban area. Thus, the nonagricultural complex of activities associated with a housing development was more detrimental to water quality than those from undisturbed or grazed rangelands.