How similar are coexisting species? Evidence from early spring herbaceous communities in logged and old growth Southern Appalachian cove forests

The diverse early spring herbaceous layer of rich cove hardwood forests in the Southern Appalachians is an ideal setting to investigate whether co-occurring species exhibit niche differentiation in resource use. Old growth forests are expected to differentiate more in resource use among herbaceous species due to higher ramet density found in old growth compared to forests logged 100 years ago. Functional traits were used as proxies for a plant’s ability to use light, water, and nutrient resources. Traits were measured for ten individuals for all species present in early April within 40- 0.25 m² plots comprising 10- 1 m² quadrats at each site (three old growth and three 100 year old forest sites) in the Nantahala National Forest, North Carolina. Two spatial scales (1 m² quadrats and 0.25 m² plots in which a total of 16,096 ramets were mapped) were used to test whether traits are more or less similar for co-occurring species than expected by random. Significantly less overlap in traits between co-occurring species than expected supports limiting similarity while more overlap than expected suggests character convergence. Preliminary results suggest that traits indicative of nutrient use (thickest root diameter and rhizome diameter) exhibit the greatest differentiation between co-occurring species while light traits (chlorophyll a:b ratio and total chlorophyll) demonstrate the greatest convergence. Despite the higher ramet density in old growth forests, there was not greater differentiation in traits compared to previously logged forests. Old growth forests did exhibit greater intraspecific aggregation which may minimize the need to differentiate resource use between species.