Direct effects of competition on individual juniper plants: a field study.
On each of two sites in western Texas, 240 Juniperus pinchotii plants were harvested. The competitive influence of herbs and shrubs associated with each juniper plant was quantified in an attempt to explain variability in survival and regrowth of individual coppiced plants. Survival and regrowth were greater on the deep-soiled Rolling Plains site than on the shallow-soiled High Plains site. Pre-harvest age or size largely controlled survival and subsequent regrowth of coppiced J. pinchotii plants. Competition from neighbouring shrubs, though significant, explained little of the observed variation in survival or growth. Competition was most common during periods of active juniper growth. Competitive influence decreased with increasing distance, but not in a linear manner. Competition from herbaceous plants was not detected.