Growth of Newly Planted Water Tupelo Seedlings After Flooding and Siltation

In central Mississippi, outplanted water tupelo seedlings survived and grew well after shallow flooding (up to 8 cm) from late February through June 1. Submersion of the seedlings, flooding until late in the growing season, reflooding, and moderate siltation reduced growth. Flooding caused changes in certain soil properties, but these changes did not seem to be the major cause of growth reductions. Forest Sci. 16: 250-256. Additional key words. Redox potential, Alligator clay, Nyssa (]fjuatica L. WATER TUPELO (Nyssa aquatica L.) is a valuable timber species in swamps which cover more than 4 million acres in the Midsouth. The swamps are usually flooded from January or February until late Mayor early June, and in wet years the water may not leave until midsummer. These wet conditions have discouraged attempts to regenerate water tupelo after logging, and extensive swamp areas in the Midsouth now need planting. Before a successful planting program can begin, information is needed on the effects of flooding and siltation during the growing season. This paper describes responses of newly planted seedlings to controlled flooding and siltation under field conditions. Previous studies have determined the general response of water tupelo to flooding. Applequist (1960) and Klawitter (1963) investigated flooding effects by reconstructing the history of existing stands. They found that growth rate was' positively correlated with the supply of available moisture during the growing season. They also concluded that extended flooding during the growing season was harmful. In greenhouse studies, Briscoel found that submersion of first-year seedlings 1 Briscoe, C. B. Diameter growth and effects of flooding on certain bottomland forest trees. Unpublished dissertation on file at Sch. Forest., Duke Univ., Durham, N. C. 1957. reduced growth more than flooding the soil only, and that the reduction increased with duration of submersion. Water at temperatures of 5° and 35° C was more damaging than that at 20° C. Hosner and Boyce (1962) in a greenhouse study with first-year seedlings found that water tupelo, green ash (Fraxinus pennsylvanica Marsh.), pumpkin ash (Fraxinus profunda (Bush) Bush), and pin oak (Quercus palustris M uenchh.) in saturated soil significantly outgrew seedlings of the same species in nonsaturated soil. Other species studied were either not affected or their growth was significantly reduced by soil saturation. Hosner et al. (1965) studied the effects of four soil moisture regimes (saturated to wilting point) upon nutrient uptake of four species. Tissue nutrient concentrations were generally low for seedlings subjected to saturated soils and high for those subjected to the wilting point regime. The authors concluded that moisture treatments apparently affected The author is Associate Silviculturist at the Southern Hardwoods Laboratory, which is maintained at Stoneville, Miss., by the Southern Forest Exp. Sta., USDA Forest Service, in cooperation with the Mississippi Agricultural Exp. Sta. and the Southern Hardwood Forest Research Group. The material is from a dissertation submitted to the Graduate Faculty of Louisiana State University in partial fulfillment of Ph.D. requirements. The author thanks Dr. N. E. Linnartz for advice before and during the research. Manuscript received Oct. 20, 1969. Reprinted from FOREST SCIENCE, Volume 16, NUll'ber 2, June, 1970 growth more tha n nutrient absorptio n. Hook2 a nd Hook a nd Stubbs (1967) studied the response of water tupelo a nd swa mp tupelo (N. sy/vatica var. biflora (Wa lt. ) Sa rg.) to six water regimes under controll ed conditions. They fou nd tha t seedlings grew about twice as fast in moving as in stagnant water. Under so me regimes, lenticels prolifera ted; and the a uth o rs suggested that these tructures may function in gas excha nge between the atmosphere a nd roots. Carbon d iox ide concentrations were higher a nd oxygen concentrations lower in stagna nt tha n in movin g water. High carbon dioxide (3 1 percent) a nd low oxygen (I percent) concentrations reduced growth. Silker ( 1948) measured res ponses of water tupelo to flooding under field conditions. H e planted seedlin gs a long margi ns of reservoirs, where floodin g depth co uld not be controlled. W ater tupelo was well ada pted to fl a ts in the zone intermittently covered by water; a bove thi s zone seedlin gs grew well only on seepage a reas. Prolonged ubmergence of the pla nts durin g the growin g eason caused d ieback, but the trees sprouted after the water leve l was lowered .