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Effects of Environmental Stress and Bunchgrass Competition on Pinus Ponderosa Seedlings Item Info

Interspecific competition between the bunchgrass Agropyron spicatum (Pursh.) Scrib. & Smith, and seedlings of Pinus ponderosa (Dougl.) Lawson was examined within a pine/bunchgrass community. Canopy separation techniques and root exclusion tubes were used to determine the effects of bunchgrass competition on pine seedlings. Shoot interference from bunchgrass did not significantly affect pine seedling survival. In contrast, bunchgrass root exclusion increased survival of P. ponderosa seedlings. Physiological responses of P. ponderosa seedlings to water and high-temperature stress were also measured in the field and in a controlled greenhouse environment. Mortality significantly increased during periods with soil water potentials less than -1.5 MPa and soil surface temperatures greater than 60۫ C. Pinus ponderosa seedlings grown in the greenhouse developed physiological and morphological characteristics that indicated adaptation to dry environments. Drought-stressed seedlings exhibited higher root:total plant biomass ratios, and had significantly lower cell wall elasticity than watered seedlings, although osmotic potentials decreased to -2.5 MPa in all seedlings. Root:total plant biomass ratios greater than 0.78, along with rapid root growth to soil depths of 1m and greater, may have increased the ability of P. ponderosa seedlings to extract soil water. Calculated heat exchange rates showed that high transpiration rates maintained seedlings stem temperatures below 63۫C, which was determined to be the lethal temperature threshold in the field. Root exclusion experiments and modeled heat exchange both indicated that soil water availability strongly influenced P. ponderosa seedling survival on dry sites with high soil surface temperatures.

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Title:
Effects of Environmental Stress and Bunchgrass Competition on Pinus Ponderosa Seedlings
Creator:
Kolb, Peter F.
Date Created:
1995-01
Description:
Interspecific competition between the bunchgrass Agropyron spicatum (Pursh.) Scrib. & Smith, and seedlings of Pinus ponderosa (Dougl.) Lawson was examined within a pine/bunchgrass community. Canopy separation techniques and root exclusion tubes were used to determine the effects of bunchgrass competition on pine seedlings. Shoot interference from bunchgrass did not significantly affect pine seedling survival. In contrast, bunchgrass root exclusion increased survival of P. ponderosa seedlings. Physiological responses of P. ponderosa seedlings to water and high-temperature stress were also measured in the field and in a controlled greenhouse environment. Mortality significantly increased during periods with soil water potentials less than -1.5 MPa and soil surface temperatures greater than 60۫ C. Pinus ponderosa seedlings grown in the greenhouse developed physiological and morphological characteristics that indicated adaptation to dry environments. Drought-stressed seedlings exhibited higher root:total plant biomass ratios, and had significantly lower cell wall elasticity than watered seedlings, although osmotic potentials decreased to -2.5 MPa in all seedlings. Root:total plant biomass ratios greater than 0.78, along with rapid root growth to soil depths of 1m and greater, may have increased the ability of P. ponderosa seedlings to extract soil water. Calculated heat exchange rates showed that high transpiration rates maintained seedlings stem temperatures below 63۫C, which was determined to be the lethal temperature threshold in the field. Root exclusion experiments and modeled heat exchange both indicated that soil water availability strongly influenced P. ponderosa seedling survival on dry sites with high soil surface temperatures.
Document Type:
Dissertation
Library Call Number:
SD397.P6115K65 1995
Subjects:
East Hatter Creek ponderosa pine pinus ponderosa bunchgrass bunchgrass competition environmental stress silviculture
UIEF Unit:
East Hatter Creek
Location:
UIEF; East Hatter Creek
Latitude:
46.840526
Longitude:
-116.780027
Department:
Department of Forest Resources
Type:
text
Format:
application/pdf

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Preferred Citation:
"Effects of Environmental Stress and Bunchgrass Competition on Pinus Ponderosa Seedlings", UIEF Research Exchange, University of Idaho Library Digital Collections, https://www.lib.uidaho.edu/digital/uief/items/uief_0099.html
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