Resistance and resilience stability of a grass mosaic and long-term mesquite demography within a mixed-grass prairie, Edwards Plateau, Texas /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1990.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | On the Edwards Plateau, Texas, Hilaria mutica produces distinct patches within a matrix of short-grasses (Buchloe dactyloides and Hilaria belangeri). Superimposed on this grass mosaic is an open canopy of Prosopis glandulosa var. glandulosa. Factors that function to form the mosaic, and short- and long-term stability of the mosaic including disturbance (competition removal with or without soil disturbance) and weather fluctuations were investigated. Prosopis recruitment, mortality, growth, and height structure, within the grass mosaic, were evaluated. Grass distribution within 45 permanent transects (0.3 m x 6 m), established prior to the 1951-1956 drought, were mapped, by species, in 1951, 1953, 1957, and 1987. Total plant canopy cover was similar in 1951 and 1987, however, significant changes in species composition and cover occurred during and following the drought. H. mutica is resistant to drought and moderate grazing, but probably displays low resilience to other disturbances. Conversely, short-grasses have low resistance to drought and high resistance to grazing and exhibit high resilience. Spatial distribution of the mosaic pattern is mostly static; 79% of the transects displayed $<$25% variation in cover and location of mosaic species from 1951 to 1987. Short-grass dominated transects were more stable (91%) than ones dominated by H. mutica (62%) from 1951 to 1987. Total soil profile depth and Bk horizon depth were both greater under H. mutica than short-grass. Soil texture, color, and CaCO3 content under H. mutica and short-grass were not different. Disturbance treatments indicate that mosaic formation and stability may be regulated by competitive interactions and differences in reproductive biology between H. mutica and short-grasses. Prosopis density increased significantly on 87 permanent plots from 1951 to 1987, but varied between sites differing in grass composition and soil resources. Differential recruitment and mortality of plants <0.3 m in height, which was higher on short-grass understories than H. mutica, accounted for these differences. A high degree of community stability results from competitive interactions, and species differences in reproductive biology, and grazing and drought avoidance/tolerance mechanisms. Soil variability also influences vegetation pattern and dynamics. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Range science." |
| Physical Description: | xiv, 139 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |