A successional study of Willows (Salix spp.) on sandbar islands in the Mississippi River using GIS

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references: p. 36-38.Issued also on microfiche from Lange Micrographics.Willows (Salix nigra Marsh. and Salix interior Row.) are short-lived, early successional species which require moist, sandy soil to germinate and can withstand long periods of innundation. Sandbar islands in the Mississippi River possess these characteristics, making establishment and growth of willows likely. Examination of aerial photographs from 1962 to 1992 of Choctaw and Lower Cracraft Islands, in approximately four year intervals, revealed initial establishment of willows on the island, followed by succession of later species. Grids and grid overlays, which are used in GIS spatial analysis, were generated from landuse classified vector files. Cross-tabulated data generated from the grid overlays were statistically analyzed and indicated that the vegetation on the islands was changing. Analysis of the percent of landcover per year, the cross-tabulated data, and grids verified that the vegetation is generally changing from willow to later successional species. River levels plotted over a forty year period were compared to the vegetation on the aerial photographs. Analysis indicated an annual trend of high river levels in the Spring and low levels in the Fall which would allow seeds to be transported in the Spring and germinate when the water began to drop in the Summer. The effect of particularly high and low river levels was inconclusive due to the small number of islands studied