Tree growth and mortality during 20 years of managing a Green-Tree Reservoir in Arkansas, USA

Green-Tree Reservoirs (GTR) are bottomland hardwood forests that are flooded during late fall and winter to provide waterfowl habitat. Early reports suggested that increased moisture improved tree growth and mast production; however, recent reports showed reduced vigor and growth. This study examines the effects of 20 years of GTR management practices in the Felsenthal National Wildlife Refuge, Crossett, Arkansas. Tree species composition, size characteristics, and vigor classes were measured in 1990, 1995, 2001, and 2006. The overall annual tree mortality rate was 2.6%, with high elevations at 1.7% and low elevations at 3.1%. Annual mortality rates exceeded 3% for willow oak (Quercus phellos) and water hickory (Carya aquatica), while rates for Nuttall oak (Q. texana), overcup oak (Q. lyrata), and sweetgum (Liquidambar styraciflua.) were lower at 2.8, 2.4, and 1.5%, respectively. Tree health (vigor) has degraded substantially for over 60% of trees initially rated in good or fair condition. Statistical probit models were generated to predict short-term (5 years) and long-term (15 years) vigor degradation. Low numbers of saplings and little advanced regeneration indicated lack of tree replacement, suggesting that inundation strategies of the GTR management may have long-term impacts on forest structure and composition in the southeastern United States.