Flood Caused Changes to the Upper Guadalupe River Riparian Forests of Central Texas

摘要

Pre-flood phytosociological measurements were made in eight apparently mature riparian forestcommunities along the upper Guadalupe River in central Texas. After a high magnitude 100+ year floodin 1978, six communities were revisited and post-flood phytosociological measurements were made toexamine flood effects on the riparian forest communities. Some riparian forests were completelydestroyed with woody plant trunks snapped or plants uprooted and washed downstream. We viewedthese as early successional communities, and did not study them. The flood caused changes in theriparian forest communities we studied previously including reductions in community basal area anddensity, as well as species basal area, density, and percent cover. Overall, community speciescomposition was unchanged based on Shannon-Weaver diversity values (H’). Species with the greatestreduction in community basal area or density were Taxodium distichum (Bald cypress), Caryaillinoinensis (Pecan), Ulmus americana (American elm), Celtis laevigata (Hackberry) and Acer negundo(Box-elder). Greatest community damage seemed to be related to tree size and bank position.Apparently, the larger the tree or species, the greater the damage sustained in the flood. Larger trees orspecies at the edge of the river sustained the greatest community change while the smallest ones atgreater distance from the river edge had the least change. However, aerial photographic evidence ofmajor river bends, areas that we did not study, suggested that water was so deep and the flood force sogreat that it cut across the bend removing most trees and vegetation in its path. Published on-linewww.phytologia.org Phytologia 99(4): 226-237 (Dec 18, 2017). ISSN 030319430.