Date of Award

1981

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Soil erosion, soil chemistry, and understory vegetation were studied after four regeneration cutting methods--clearcut, seed-tree, shelterwood, and selection--were applied to mature loblolly pine (Pinus taeda L.) stands at two locations in southeastern Louisiana. Treatment plots were 8 ha in size, and each treatment was replicated twice at each location. Soil erosion on slopes was measured from permanent stakes located at the top, middle, and bottom on each of six slopes within each plot. Soil erosion off the slopes was determined from a small trap built across one individual drainage on each plot. Vegetation was sampled four times before and after cutting. Analysis of variance of erosion data on the slopes revealed that significant differences among treatments occurred during only three of the 16 data periods at only one of the two locations. However, these differences were very small and were not consistent among treatments nor among data periods. Although some soil movement occurred on slopes, a good cover of litter and vegetation prevented soil loss from the plots. Measurable amounts of sediment were collected only from two clearcut plots. Sediment collected from one clearcut plot was caused by erosion from a logging road and loading deck; on the other plot, erosion after logging and site preparation produced some sediment. Only exchangeable K('+) and Ca('++) were influenced by harvest treatments. At both locations, the K('+) content was increased at the 15-30 cm depth, while calcium was significantly reduced at the 0-15 and 15-30 cm depths. The heavier the cutting, the greater the effect on the composition and amount of vegetation present after timber harvest. The variety of species and amount of cover were greatest on the clearcut, followed by the seed-tree, shelterwood, and selection plots. After harvest cutting, several new plant species became established but other species disappeared from the study plots. With proper planning and application, any of the four regeneration systems studied can be used in southeastern Louisiana with minimal effects on soil erosion or soil chemistry. Vegetation composition and cover will be altered according to the amount of overstory removed.

Pages

249

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