@conference {51423, title = {Effects of summer drought on the water relations, physiology and growth of large and small plants of Prosopis glandulosa and Larrea tridentata}, booktitle = {Wildland Shrub Symposium}, year = {1995}, month = {May 23-25, 1995}, pages = {19}, abstract = {Large and small plants of creosotebush (Lorreatridentata) and mesquite (Prosopisglandulosa) were subjected to summer drought by erecting rain-exclusion shelters with transparent plastic roofs over the experimental plants. The root systems of control and experimental plants of both species were isolated from the surrounding soil mass to a depth of approximately 1.5 m, with a backfilled, plastic-lined trench approximately 0.6 m from the plant crown dripline. The rainout shelters were very effective in drying the soil as measured with a neutron atennuation probe at 0.3 and 0.9 m. Both large and small plants responded to drought with lowered xylem water potential and lowered photosynthetic gas exchange, but the gas-exchange physiology of large plants appeared to be somewhat uncoupled from the short-term drought we induced. Stem growth was much greater in control plants, and in experimental plants growth appeared to be greater in small plants than in large plants. Our results are largely consistent with shrub resource islands theory which suggests that large, established plants with greater accumulated resources are better able to withstand episodes of short-term drought than are small, establishing shrubs.}, keywords = {Larrea tridentata, physiology, prosopis glandulosa, summer drought, water relations}, author = {A.G. de Soyza and Walter G. Whitford and A. C. Franco and R. A. Virginia and J. F. Reynolds} }