Environmental Influences on Gas Exchange in Fertilized and Non-Fertilized Stands of Loblolly Pine

Spatial and temporal variation in foliar gas exchange on both a diurnal and seasonal scale was examined in 15-year-old fertilized and non-fertilized loblolly pine in the upper and lower thirds of crowns in stands located in the North Carolina sandhills. Photosynthesis rates between control and fertilized stands for both seasonal and diurnal measurement periods were different during only three months. Photosynthesis rates were consistently greater in the upper third of the crown compared to the lower third. Seasonal trends in both conductance and transpiration closely resembled trends found in seasonal photosynthesis. Foliar nitrogen concentrations were greater in fertilized stands for all months sampled. However, nitrogen content generally did not correlate with photosynthesis rates. Mean monthly water use efficiencies were significantly higher in fertilized stands during two months and were usually greater in upper crown foliage. Common empirical gas exchange models reveal that light and vapor pressure deficit (VPD) explain a majority of the variation observed in photosynthesis and transpiration, respectively. Conductance was not modeled since environmental variation did not adequately explain conductance patterns. Predicted light response curves reveal that upper crown foliage has higher maximum photosynthesis rates, respiration rates, light compensation points, and lower initial quantum yield compared to lower crown foliage. Models predict that foliage from fertilized stands is more sensitive to VPD and light during the growing season. Transpiration models predict highly variable responses to VPD depending on the treatment combination and season. Model R-square and predicted gas exchange values suggest that seasonal acclimation occurred.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Forestry

Department dc:contributor.department

Forestry

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2000

Author dc:creator

• Gough, Christopher Michael

Chair dc:contributor.committeechair

• Seiler, John R.

Committee members dc:contributor.committeemember

• Chevone, Boris I.
• Mou, Paul P.

• seasonal and diurnal variation
• Loblolly Pine
• environment
• crown position
• fertilization
• gas exchange

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-08022000-11480057

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/34301