Date of Award

1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Robert E. Noble

Abstract

An understory vegetative succession study was conducted on the LSU Lee Memorial Forest near Bogalusa, Louisiana. Research blocks were established within fifteen-year-old overstocked loblolly pine (Pinus taeda) stands, in specific areas classified as with or without a history of prescribed burning for the current timber rotation. Silvicultural treatments involved precommercially thinning randomly selected blocks to various stand densities, along with the establishment of unthinned control areas. Growth rates of residual trees were determined from tree diameter measurements, on all timbered plots. Burn-history areas received a further treatment, involving the mechanical destruction of all timber on specified areas, followed by site-preparation fires. These clearcut areas, representing initial secondary succession, were planted with one-year-old loblolly pine seedlings. Control plots, application of various herbicide treatments, and the continued use of prescribed fire, were subtreatments made within timbered plots in burn-history areas. Replanted areas received banding and spot-gun herbicide applications along with untreated areas to serve as controls. The amount of available light, measured as photosynthetic active radiation (PAR), was determined annually, along with the composition and density of understory vegetation. Successional changes in vegetation led to increases in the density of most plant taxa. Increases were most pronounced within clearcut and replanted areas, with the greatest disturbances. Herbicide treatments on clearcut plots lowered the density of most taxa in the Spring following herbicide application. Most plant taxa impacted by herbicide applications rebounded to greater densities the year following treatments. Herbicide usage within timbered areas impacted understory vegetation to a lesser extent than within clearcut areas. Light levels within all timbered plots failed to teach the critical levels necessary for understory vegetation to be fully impacted by herbicides. A history of prescribed fire suppression or use had a greater bearing on the composition and density of understory vegetation than the use of fire as an implemented treatment. Absence of abundant understory vegetation, along with greater numbers of larger woody stems, were characteristic of no-burn-history areas. The passage of time was the single most important factor in determining the composition and density of understory vegetation on all areas.

ISBN

9780591288797

Pages

169

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