The Influence of Overstory Structure on Understory Light Availability in a Longleaf Pine (Pinus palustris Mill.) Forest

dc.contributor.authorBattaglia, Michael Anthonyen
dc.contributor.committeechairMou, Paul P.en
dc.contributor.committeememberMitchell, Robert J.en
dc.contributor.committeememberJones, Robert H.en
dc.contributor.departmentForestryen
dc.date.accessioned2014-03-14T20:46:45Zen
dc.date.adate2000-10-23en
dc.date.available2014-03-14T20:46:45Zen
dc.date.issued2000-09-15en
dc.date.rdate2001-10-23en
dc.date.sdate2000-10-17en
dc.description.abstractUnderstory light environments are inherently heterogeneous and therefore difficult to characterize. Numerous methods to measure understory light have been assessed in closed-canopied forests; however, the reliability of these methods has not been addressed for open-canopied forests. Therefore, the first objective of this study, presented in Chapter 3, was to test the accuracy and precision of various light measurement techniques at different time scales and sky conditions. The methods assessed performed differently depending on the sky condition and time of year when the sample was taken. To estimate annual photosynthetic photon flux density transmittance (annual %PPFD), the use of a 10-minute average of PPFD measured on an overcast day (%PPFDovercast) was effective, but accuracy decreased with decreasing solar altitude (ie season change). Hemispherical photographs used to estimate weighted canopy openness and gap fraction were effective methods, but gap light index (GLI) also derived from hemispherical photographs performed better. Accuracy of daily %PPFD estimates using %PPFDovercast, weighted canopy openness, and gap fraction were strongly affected by solar altitude and sky condition. Gap light index was very effective in estimating daily %PPFD for all sky conditions and time periods. The second objective of this study, presented in Chapter 4, was to characterize the relationship between canopy structure and spatial distribution of light by using three replicates of one uncut treatment and three harvest treatments: single tree, small gap (0.1 ha), and large gap (0.2 ha). Each harvest retained similar residual basal area but with different spatial patterns of the residuals, ranging from uniformly dispersed (single tree) to different degrees of aggregation (small and large gap). Average stand level light availability increased 12-22% when the same residual basal area of trees was distributed in clusters versus a uniform distribution. The variation of light availability increased as stands became more aggregated and larger amounts of the variation was explained by the spatial pattern of the canopy structure. Spatial autocorrelation range was twice as large in the small gap harvest then the other harvest treatments. It is suggested that seedling growth response to these differences in spatial patterns of light may differ between the different harvests.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-10172000-15110052en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-10172000-15110052/en
dc.identifier.urihttp://hdl.handle.net/10919/35411en
dc.publisherVirginia Techen
dc.relation.haspartchap1&2.pdfen
dc.relation.haspartchap4.pdfen
dc.relation.haspartchap3.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectlongleaf pineen
dc.subjectlight measurementsen
dc.subjectheterogeneity of lighten
dc.subjectcanopy structureen
dc.subjecthemispherical photographyen
dc.titleThe Influence of Overstory Structure on Understory Light Availability in a Longleaf Pine (Pinus palustris Mill.) Foresten
dc.typeThesisen
thesis.degree.disciplineForestryen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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