Impacts of Mechanical Tree Felling on Development of Water tipelo Regeneration in the Mobile Delta, Alabama

Two water tupelo (Nyssa aquatica L.) stands in the Mobile Delta of Alabama were selected to test the hypothesis that mechanizedfelling does not reduce establishment and growth of natural water tupelo regeneration relative to traditional tree felling with chainsaws. To test the hypothesis, we established six, 2 ac treatment plots in each of two blocks on each of two sites, and randomly assigned plots to either mechanical tree felling with a tracked, swing feller or chainsaw felling. Each site was clearcut in Fall, 1992, and merchantable boles were removed by helicopter. Establishment and growth of regeneration was assessedprior to harvest and annually for 3 yr after harvest infive, 0.01 ac measurement plots located in each treatment plot. Stand harvesting promoted establishment of water tupelo seedlings such that 3 yr after treatment we recorded over 27O/ac on each site regardless offelling method. Seedling height increased at a steady rate and averaged about 39 in. tall after three growing seasons. Woody competition also responded to the harvest, outnumbering water tupelo seedlings 3 yr after treatment by as much as seven to one on Site 2. Water tupelo stump sprouts developing from chainsaw felling grew well and averaged about 13.5 ft tall after three growing seasons. However, mechanicalfelling reduced water tupelo stump sprouting by 50% leading to a lower density of sprout clumps in mechanicallyfelledplots (P = 0.0253). Our results indicated that mechanicalfelling techniques used in this study may adversely impact regeneration of water tupelo swamps where coppice is a desirable form of reproduction. South. J. Appl. For. 24(2):65-69. w ater tupelo (Nyssa aquatica L.), a tree of sloughs and deep swamp sites in wetland forests, ranges across the southem United States from southeastern Virginia to southeastern Texas and northward through the Mississippi Alluvial Valley to southern Illinois (Johnson 1990). A conservative estimate of 2.9 million ac of forested wetlands are occupied by water tupelo and its most common associate, baldcypress (Taxodium distichum [L.] Rich.) (Conner andBuford 1998). Because the swampy sites occupied by water tupelo are characterist ically inundated, this species is well adapted for growth in anaerobic soils and is able to utilize annual inflows of nutrient rich water received by swamp basins. Consequently, the swamp sites on which water tupelo thrives can be among the most NOTE: Emile S. Gardiner is the corresponding author, and he can be reached at (601) 686-3184; Fax: (601) 686-3195; E-mail : egardinel [email protected]. This research was initiated while E.S. Gardiner, D.R. Russell, Jr., and J.D. Hodges were located at the Department of Forestry at Mississippi State University. The authors thank the employees of Mississippi State University and Kimberly-Clark Corporation, especially Greg Williams, who spent many hours collecting data in the swamps. manuscript received April 14, 1999, accepted August 10, 1999. productive of southern forests (Conner and Day 1976, Hodges 1993, support ing stands with basal areas in excess of 400 ft2/ ac and mean annual volume increments greater than 150 ft3/ ac/yr (Kellison and Young 1997). This exceptional productivity perpetuates the value of water tupelo as a source of fiber and lumber, but the annual inundations that maintain the productivity of swamp forests create logistical and environmental concerns for harvesting operations. Early lumbermen met the challenges of harvesting bottomland swamps through development of railroad logging and the pullboat, a barge-mounted skidder capable of winching felled logs nearly a mile through the swamp (Mancil 1980). Though effective in extracting felled logs from the swamp, pullboat “runs” remain as an indelible reminder of early harvest ing in swamps across the southern United States. Modem loggers realize that maintenance of wetland functioning hinges on limiting hydrologic alterations, limiting soil disturbance, and ensuring adequate stocking of the future stand during the regeneration harvest (Aust and Lea 1992, Lockaby et al. 1997). Yet there can be improved efficiency Reprinted from the Southern Journal of Applied Forestry, Vol. 24, No. 2, May 2000. Not for further reproduction. 65: and increased job-site safety through mechanization of harvest ing processes (Stokes and Shi l l ing 1997) . Thus there is a critical need to develop harvesting equipment and methods suitable for use on wetland soils. One method currently employed in swamps of the Mobile Delta involves the use of a tracked, swing feller that maneuvers above the soil surface on portable wooden mats. The portable mats reduce soil impacts by displacing the weight of the feller over a large surface area. Once trees are felled, ground crews attach choker cables to merchantable boles, which are extracted from the swamp with a helicopter (Willingham 1989). Although the operation described by Willingham (1989) can be efficient for harvesting wetland sites, the impact of the feller on establishment and growth of water tupelo regeneration is not known. Mechanized harvesting operations can potentially affect regeneration of wetland si tes, especially by altering hydroperiods and destroying vegetative reproduction (Lloyd et al . 1992, Lockaby et al . 1997). In this study, we tested the hypothesis that tree felling with a tracked, swing feller which maneuvers on portable mats does not reduce establishment and growth of natural water tupelo regeneration relat ive to the more labor intensive practice of tree fel l ing with chainsaws.