Analyzing Site Suitability for Baldcypress (Taxodium distichum) Regeneration Along a Hydrologic Gradient in South Louisiana Swamps
Master of Science (MS)
Renewable Natural Resources
The future of Louisiana’s coastal cypress-tupelo forests is threatened by prolonged or permanent flooding during the growing season. Permanent inundation prevents baldcypress seedlings from becoming established. The upper limit of submergence with respect to adequate planted baldcypress seedling performance has not been effectively tested under actual field conditions. Similarly, an effective method for determining a site’s regeneration potential based on present vegetation attributes has not been developed. To test first-year performance of planted baldcypress seedlings under varying levels of submergence, I planted 900 of both 1-0 and 2-0 age-class bare-root seedlings across 12 different sites covering a range of hydrologic conditions and monitored their performance over the 2014 growing season. Water levels were continuously monitored for each individual seedling, and survival and height growth were documented. Due to their taller starting heights, 2-0 seedlings were submerged, on average, less often (1.4 days) than 1-0 seedlings (34.8 days). Survival was high across sites for both age classes (79% for 1-0 and 89% for 2-0). Survival of 1-0 seedlings decreased to only 9% following more than 90 cumulative days of submergence. Height growth across sites was greater for 1-0 seedlings (0.29 m) than 2-0 seedlings (0.13 m). Height growth of 1-0 seedlings decreased significantly following more than 30 cumulative days of submergence. To relate present vegetation attributes to baldcypress regeneration potential, I sampled the vegetation on all 12 sites in addition to using vegetation and hydrology data from five sites monitored by the Coastwide Reference Monitoring System (CRMS). Sites were separated into three categories based on how their hydrologic regime related to baldcypress regeneration potential. Sites with potential for natural regeneration were indicated by a species-diverse overstory and a high midstory stem density. Sites with only artificial regeneration potential were indicated by an overstory layer consisting almost exclusively of cypress-tupelo and a dense midstory layer with a high percentage of stems rooted on elevated structures. Sites with neither natural nor artificial regeneration potential were indicated by an overstory layer consisting almost exclusively of cypress-tupelo and a sparse midstory layer with a high percentage of stems rooted on elevated structures.
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Rutherford, Marcus, "Analyzing Site Suitability for Baldcypress (Taxodium distichum) Regeneration Along a Hydrologic Gradient in South Louisiana Swamps" (2015). LSU Master's Theses. 3709.