PARENT SESSION
Contributed Oral Session 58: Forest Ecology: Riparian Areas
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 514 A, Level 5, Palais des congrès de Montréal

Forest composition and nutrient limitation in alluvial and blackwater floodplain forests of the southeastern United States.

Frederick, Heather¹, Walbridge, Mark¹, ¹ West Virginia University, Morgantown, WV, USA

ABSTRACT- We examined variations in forest composition and nutrient (N, P) limitation in eight alluvial and blackwater floodplain forests in the southeastern United States. Study sites were located on two parent materials--younger Pliocene/Miocene sediments approximately 2-24 million years old and older Cretaceous sediments approximately 66-144 million years old (n=2 per floodplain type/ parent material combination). Our objectives were to relate species composition and nutrient limitation to floodplain type and parent material age. We quantified forest composition in three randomly located 0.1ha sample plots at each study site, and estimated nutrient limitation of plant productivity by comparing net growth in fertilized (N, P, N+P) and non-fertilized (control) root ingrowth cores over two six month periods during 2003 and 2004. During 2003, mean root ingrowth varied from 0.0925 to 1.6324g/m² (dry mass), and was significantly greater in N and N+P fertilized cores that in control and P fertilized cores. Preliminary analysis of 2004 data suggest the same growth pattern. Data indicate significant variation in forest composition among these forested floodplains, and suggest that N is the nutrient that most limits plant growth in these ecosystems regardless of floodplain type or parent material age. However, alluvial forested floodplains appear to show a stronger response in terms of rootgrowth than blackwater forested floodplains.

Key words: Forested Floodplain, Nutrient Limitation, Root Growth, Forest Composition