Spatial and Temporal Variation in Competitive Effects on Soil Moisture and Pine Response

Abstract

The effects of different plant life-forms, including a bunch grass species, Andropogon virginicus L. (broomsedge), and a sprouting deciduous tree species, Liquidambar styraciflua L. (sweetgum), on soil moisture and competitive responses of a transplanted coniferous tree seedling, Pinus taeda L. (loblolly pine), were investigated. Addition of the bunch grass and/or hardwood sprouts either had no effect or increased soil moisture in the surface soil (0-14 cm) depending on the time, while addition of sweetgum and/or broomsedge (greatest density alone) decreased soil moisture in deeper portions of the solum during the summer months. Soil moisture available to pine seedlings at various points in time was assessed by measuring predawn xylem pressure potential. Temporal variation in predawn xylem pressure potential was accounted for through a water stress integral approach. More than half of the variation in pine size after one growing season could be accounted for by the water stress integral.

Interactions between neighbour environments and drought resistance

“…Shainsky et al, 1992;Gordon & Rice, 1993;Mitchell et al, 1993). Although competition has been found to increase root allocation (e.g.…”

Switch between competition and facilitation within a seasonal scale at colony level in bryophytes

“…Facilitation and competition may operate simultaneously, and the overall eVect of one species on another may vary in space and time (Travis et al 2006). Several studies have inferred, and in part clariWed, the importance of abiotic variables such as moisture in contributing to the outcome of the interaction between competition and facilitation (Mitchell et al 1993;James et al 2003). Climatic Xuctuations, for example, even though poorly investigated in the framework of plant interactions, are considered a major force able to inXuence both the balance between positive and negative interaction and therefore also the spatial distribution of plants (Brooker et al 2008).…”

Sweetgum: a new look

“…The presence of sweetgum can lead to greater competition for limited resources such as water, reducing survival and growth of the desired pine trees. Sweetgum can reduce soil moisture at depths of 60-90 cm in the soil which can directly adversely affect potential growth of the planted P. taeda stand (Mitchell et al 1993). Especially during times of limited water which is common from June to September in much of the pine-sweetgum range, the effect of increased competition by sweetgum can lead to exacerbated water stress and changes in stomatal conductance, the exchange of carbon dioxide molecules through the leaf stomata, which affects photosynthesis (Perry et al 1994).…”