Growth of six planted tree species under various cultural treatments on former agricultural bottomlands

Falling soybean prices in the mid-1970s resulted in extensive abandonment of agricultural wetlands in the Mississippi Valley. Research has been conducted on the reforestation of these sites, but few studies have documented the long-term results of reforestation practices. This study was initiated to determine tree species and cultural treatments best suited to west Tennessee's former agricultural bottomlands. The effects of seed source, fertilization, disking and mowing on sweetgum (Liquidambar styraciflua L.), American sycamore (Platanus occidentalis L.) and green ash (Fraxinus pennsylvanica Marsh.) were examined 18 years after planting. Seventeen-year-old cherrybark oak (Quercus pagoda Raf), yellow-poplar (Liriodendron tulipifera L.) and loblolly pine (Pinus taeda L.) under fertilization, disking and mowing also were examined. Variations in soil series and bulk density and the effects of water table depth on tree growth were analyzed. Overall survival was significantly higher for sweetgum (93%) and green ash (95%) than for sycamore (88%). Height growth of sweetgum was significantly greater than sycamore, which was significantly greater than that of green ash. Seed source (Virginia Coastal Plain vs. Louisiana Gulf Coast) had no effect on the growth of sycamore or sweetgum. Height and dbh of sweetgum, sycamore and green ash were significantly increased by fertilization only on plots that were not disked or mowed. Disking and mowing significantly increased the growth of unfertilized trees more than that of fertilized trees. Survival was 92%, 64% and 63% for yellow-poplar, cherrybark oak and loblolly pine, respectively. Growth of loblolly pine was significantly greater than that of cherrybark oak. The growth and survival of yellow-poplar, cherrybark oak and loblolly pine were not affected by cultural treatments. Natural regeneration on the same site resulted in dense stands (3,445 trees/acre and 4,340 trees/acre) dominated by sweetgum. The combination of fertilization and mowing significantly increased soil bulk density. Soils were much more variable than prior soil surveys indicated. Although a shallower water table increased survival of sweetgum and sycamore, growth was increased for these two species on better-drained soils.