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Water Relations and the Effects of Shade on Uneven-Aged Management Item Info

Competition, in the form of shade, severely limits the growth and survival of understory trees in uneven-aged forests. Light is obviously reduced under shaded conditions, but other factors like water and nutrient supply may also be especially limiting to tree productivity and survival. This study was established to test the hypothesis that water limits tree productivity under shade through a decreased leaf specific hydraulic conductivity and maximum stomatal conductance. Fifty-two ponderosa pine and twenty Douglas-fir saplings were identified and studied under a range of light conditions from sun to shade. For ponderosa pine and Douglas-fir, maximum stomatal conductance was found to decline with increasing shade. Leaf specific conductivity, predrawn water potential, and productivity, measured as three-year height and basal area increment, also significantly declined with increasing shade for ponderosa pine. Predrawn water potential and leaf specific conductivity were also strongly related to stomatal conductance, as expected in terms of water supply and demand. Productivity was positively related to leaf specific conductivity and negatively related to shade for both species. Leaf specific conductivity is a measure of the hydraulic sufficiency of a tree to supply water to transpiring foliage, so it follows that trees with a low leaf specific conductivity are less able to maintain stomatal conductance and transpiration with a given pressure gradient. Thus, they have reduced carbon assimilation and lower productivity as a result. The quantification of productivity can be directly related to the level of shade for practical forest management.

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Title:
Water Relations and the Effects of Shade on Uneven-Aged Management
Creator:
Estoll, Greg
Date Created:
2001-05
Description:
Competition, in the form of shade, severely limits the growth and survival of understory trees in uneven-aged forests. Light is obviously reduced under shaded conditions, but other factors like water and nutrient supply may also be especially limiting to tree productivity and survival. This study was established to test the hypothesis that water limits tree productivity under shade through a decreased leaf specific hydraulic conductivity and maximum stomatal conductance. Fifty-two ponderosa pine and twenty Douglas-fir saplings were identified and studied under a range of light conditions from sun to shade. For ponderosa pine and Douglas-fir, maximum stomatal conductance was found to decline with increasing shade. Leaf specific conductivity, predrawn water potential, and productivity, measured as three-year height and basal area increment, also significantly declined with increasing shade for ponderosa pine. Predrawn water potential and leaf specific conductivity were also strongly related to stomatal conductance, as expected in terms of water supply and demand. Productivity was positively related to leaf specific conductivity and negatively related to shade for both species. Leaf specific conductivity is a measure of the hydraulic sufficiency of a tree to supply water to transpiring foliage, so it follows that trees with a low leaf specific conductivity are less able to maintain stomatal conductance and transpiration with a given pressure gradient. Thus, they have reduced carbon assimilation and lower productivity as a result. The quantification of productivity can be directly related to the level of shade for practical forest management.
Document Type:
Thesis
Library Call Number:
SD358.8.I2E88 2001
Subjects:
West Hatter Creek stomatal conductance shade competition watershed management specific conductivity carbon assimilation productivity ponderosa pine pinus ponderosa silviculture
UIEF Unit:
West Hatter Creek
Location:
UIEF; West Hatter Creek
Latitude:
46.83765
Longitude:
-116.824734
Department:
Department of Forest Resources
Type:
text
Format:
application/pdf

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Preferred Citation:
"Water Relations and the Effects of Shade on Uneven-Aged Management", UIEF Research Exchange, University of Idaho Library Digital Collections, https://www.lib.uidaho.edu/digital/uief/items/uief_0036.html
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