Quantification of seedling microclimate in an East Texas loblolly pine (Pinus taeda L.) shelterwood and clearcut /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Regeneration of loblolly pine (Pinus taeda L.) often fails on harsh sites in East Texas, probably because of high temperature and moisture stress. Preliminary studies have shown that loblolly shelterwoods have the potential to substantially influence temperature, radiation, humidity and windspeed of the seedling level microclimate relative to those in a clearcut. Although each of these individual factors has an influence on seedling environment, there are also interactive effects among the variables which complicate the determination of a partial overstory's impact on seedling environment. Empirical functions have been developed that relate the relevant environmental variables to each other. One such relationship is the combination equation for potential evaporation. The near-surface environment of an East Texas clearcut and shelterwood site were instrumented to test the hypothesis that a partial overstory can influence a seedling's microclimate. This hypothesis was fully supported over a period of 209 days of measurement. The influence of the shelterwood on measured variables was primarily due to the partial overstory canopy dispersing incident radiation before it reached the near-surface environment, where it could significantly affect the microclimate. Net radiation and photosynthetically-active Radiation (PAR) levels measured on the shelterwood site were 67.0 and 65.4% of that measured in the clearcut. Air temperatures and actual vapor pressure (AVP) were not strongly influenced by the partial overstory due to advection and convection in the well mixed surface layer. Soil surface temperatures in the clearcut reached levels high enough to potentially damage seedlings, whereas temperatures in the shelterwood did not. Daily average wind speeds were consistently greater in the clearcut. Estimates of daily total potential evaporation for the clearcut were consistently greater than those for the shelterwood, over 158 days. PET estimates were highly dependent on net radiation values. Soil moisture levels showed no overall general trend between the clearcut and shelterwood sites. It was shown that although PET had some significant affect on seedling physiology, it was not possible to use PET estimates to infer seedling physiological response to its microclimate, on these sites, during the relatively wet year of 1990/1991. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Forestry." |
| Physical Description: | xi, 85 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |