The effects of neighbors on the growth and survival of shrub seedlings following fire

Abstract

Where plant species vie for limited resources, disturbances might preclude competition by releasing a flush of nutrients, or by reducing biomass and thereby diminishing the consumption of resources. However, if new seedlings colonize in clumps, they may still deplete resources within the local aggregations, which may then reduce their growth and survivorship. We investigated competition among seedlings in a burned area by examining the relationship between the performance of newly established shrub seedlings of Ceanothus impressus and (1) the proximity and (2) the identity of their near neighbors. We also investigated the relationship between neighbor proximity and the availability of water. Both survivorship and growth of C. impressus were positively associated with increasing distance to near neighbors, in a manner consistent with resource competition. The availability of water (as determined by pre-dawn xylem pressure potentials) tended to be greater when neighbors were farther away, providing evidence that water was a resource for which plants were competing. This conclusion is reinforced by the finding that the effects of neighbors were stronger in drought years, suggesting that yearly variation in the availability of an important resource (water) can affect the strength of competitive interactions. This suggests that after disturbances, when some resources are apparently abundant on a large scale, competition may be important in determining the small scale patterns of seedling growth and survival.

Expansion of Rosa rugosa and Hippophaë rhamnoides in coastal grey dunes: Effects at different spatial scales

“…Mosses showed no consistent negative effects of increasing shrub, probably because this life form comprises high proportions of comparatively shade-tolerant species. In addition, R. rugosa shrubland often grows so dense that only few gaps are available for the germination of any species, which is already shown for other shrublands (Tyler and D' Antonio, 1995). In contrast, an increase in H. rhamnoides cover had a positive effect on the number of further shrubs and other typical shrubland species.…”

Fire-mediated effects of shrubs, lichens and herbs on the demography of Hypericum cumulicola in patchy Florida scrub

“…Fire creates opportunities for recruitment and growth of herbaceous species like H. cumulicola in rosemary scrub patches because of its long-term eect on resource availability and aboveground biomass (see Zedler and Zammit 1989;Tyler and D'Antonio 1995). H. cumulicola is virtually absent in the dense and shrub-dominated scrubby¯atwoods and¯atwoods that are more common in the regional landscape.…”

Seedling competition between native cottonwood and exotic saltcedar: implications for restoration

“…Competition is considered an important factor in structuring plant communities (e.g., Tilman 1988;Grime 2001). However, ecologists find it difficult to make accurate predictions about the outcome of competitive interactions in many plant communities (e.g., Connell 1983;Connor and Simberloff 1979;Gilpin and Diamond 1984).…”