Foliar δ¹⁵N patterns along successional gradients at plant community and species levels

Relationships to ¹⁵N abundances have been found in aridity, rainfall, soil age and latitudinal gradients across large spatial and temporal scales and patterns at intermediate spatial and temporal scale remain unclear. An investigation on ¹⁵N abundances at intermediate spatial and temporal scale was conducted in a series of successional fields (Blandy Experimental Farm) in northern Virginia. Foliar and soil samples were collected from these fields in mid-summer 2004 and 2005. The results showed that foliar δ¹⁵N signatures decreased as successional age increased at both the plant community and species levels. There were also significant decreases in soil δ¹⁵N as succession proceeded. These results provide a clear example that δ¹⁵N signatures in certain ecosystems, like an early successional field, could change significantly at time scales within human lifespans and such dynamics should be considered when modeling δ¹⁵N spatial patterns.