This research will examine the effects of several woody and herbaceous wetland and upland plant species on the growth of trees on reclaimed phosphate mined lands in Florida. Control of primrose willow (Ludwigia spp.) and cattail (Typha spp.) in wetlands is required by the Florida Department of Environmental Regulation, but trees have been observed to overtop these species in a few years and may shade them out with time. Bahiagrass (Paspalum notatum) and bermudagrass (Cynodon dactylon) are commonly planted on reclaimed lands but may inhibit tree establishment and growth. The competitive effects of and the need to control primrose willow, cattail, bermudagrass, and bahiagrass will be evaluated. The potential value of woody nurse crops (eg., willow, Salix caroliniana; and wax myrtle, Myrica cerifa) to shade out weeds while allowing shade tolerant forest trees to grow will be compared with conventional methods of tree establishment. Less competitive herbaceous cover crops will also be evaluated.
1995-1996 Progress Report - Abstract
Florida regulations require that "nuisance" species, including the native primrose willow (Ludwigia peruviana) and cattail (Typha spp.), be limited to less than ten percent of the cover on reclaimed wetlands. Controlling these two species is expensive and may be unnecessary. It is hypothesized that shade-tolerant trees can grow through, overtop, and shade out these sun-requiring "nuisance" species. This study, conducted on reclaimed phosphate mined lands in central Florida, compared tree growth in primose willow stands (P1 and P2 sites) and in cattail stands (C1 and C2 sites) versus with the nuisance species removed (cut or herbicided). Through three growing seasons at the P1 site, primrose willow had little or no effect on baldcypress (Taxodium distichum) height growth, but by the sixth growing season, baldcypress was 25 percent taller with primrose willow removed. Nevertheless, baldcypress growth was substantial in the presence of primrose willow. After three growing seasons 50 percent of the baldcypress trees had grown through and overtopped the primrose willow, and that figure had increased to 85 percent after the sixth growing season. Popash (Fraxinus caroliniana), baldcypress, and red maple (Acer rubrum) heights were only slightly affected by primrose willow competition at the P2 site after three years, although some trees were bent over by the primrose willow. Cattail had little or no effect on heights of baldcypress or popash after two years. The modest effect of primrose willow on baldcypress indicates control measures, which are expensive, are not necessary. If trees are planted at a sufficient density, they will eventually develop a canopy cover that will probably shade out the primrose willow.
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