PRESENTATION
B.D. Keeland(1) L.E. Gorham(2), G. Weisbrich(1), C. Wells(1), and S. Mopper(4) bob_keeland@usgs.gov
(1)USGS, NWRC, 700 Cajundome Blvd., Lafayette, LA 70506‐3152
(2)USDA ‐ NRCS, 59 Waterfront Plaza, Suite 11, Newport, VT 05855‐4877
(3)3509 Lois Lane, Harrisburg, SD 57032
(4)Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70504
Abstract
In August 1992 Hurricane Andrew caused extensive tree uprooting and soil upheaval in the Atchafalaya Basin of southern Louisiana. To study the impact on the herbaceous and woody vegetation recovery associated with mound/depression microhabitat, we selected 120 tree tip‐up mounds from two disturbed sites. In 1994, 1996, and 1998 we surveyed plant diversity and species presence/absence on tip‐up mounds, associated depressions, and adjacent undisturbed soils.
Initially, mounds supported significantly greater herbaceous plant diversity than either undisturbed or depression soil microsites. One‐third (20 out of 60) of the herbaceous plant species observed on the three micro‐habitat types were found exclusively on tip‐up mounds. Over time, however, diversity decreased on mounds and increased in depressions and on undisturbed soils. A significant increase in vine species over time was observed in mound and depression microsites. Depression microsites, however, supported significantly fewer vine species than mounds and undisturbed soils throughout the study period. The number of tree seedlings increased through time at Site A, and at both sites, there were more seedlings in undisturbed than in the mound or depression habitats. The tipped tree species and viability status had significant impacts on mound degradation rates. Mounds associated with uprooted but viable trees had significantly slower degradation rates than mounds associated with uprooted trees that died.
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