Kolb, P.F. and R. Robberecht. 1996. Pinus ponderosa seedling establishment and the influence of competition with the bunchgrass, Agropyron spicatum. International Journal of Plant Sciences. 157:509-515.
Abstract Interspecific competition
between Agropyron spicatum (Pursh.) Scrib. & Smith
bunchgrasses and naturally established seedlings of Pinus
ponderosa was examined within a pine/bunchgrass community.
Canopy separation techniques were used to determine if bunchgrass
culms influenced the survival of pine seedlings. In addition,
two lengths of root exclusion tubes were used to determine the
effects of bunchgrass root overlap on pine seedlings. The bunchgrass
canopy did not significantly affect pine seedling survival. However,
root competition, presumably for water, significantly decreased
pine seedling survival. Exclusion of bunchgrass roots from 0.15-m
and 0.30-m deep root zone of pine seedlings resulted in 40% and
80% reductions in mortality, respectively. Root exclusion also
significantly delayed mortality 2-3 weeks. Pine seedlings developed
taproots that reached below the zone of maximum bunchgrass root
density within four weeks of germination. The pine/bunchgrass
community is dominated by two species that can utilize different
resource zones in the soil, thereby reducing interspecific competition
except during the establishment of pine germinants. In areas with
shallow soils, establishment of pine seedlings may occur successfully
only if soil moisture is available in deeper soil horizons during
the summer.
Key words: Pinus ponderosa - Agropyron
spicatum - Interspecific competition - Root competition -
Seedling survival - Roots
This project was funded by the McIntire-Stennis Cooperative Forestry Research
Program through the University of Idaho, College forestry, Wildlife and Range Sciences,
Moscow, Idaho. Contribution no. 795 of the Forest, Wildlife and Range Experiment Station,
University of Idaho..