3.1 The Interaction Between Nitrogen and Carbon Cycles at UMBS. Cumulative NH4-N and NO3-N deposition and canopy retention at UMBS in 2004 (Nave et al., in preparation).

The linkage between the nitrogen (N) and carbon (C) cycles at UMBS is the focus of Lucas Nave's doctoral research. The amount of N available to plants generally has a direct effect on biomass production and physiological processes involved in C storage such as photosynthesis and respiration.

Atmospherically deposited N is an important source of available N. The quantity of N retained by the canopy is of interest because it is possible that this N is directly taken up and assimilated by leaves. Recent results show that NH4-N and NO3-N constituted 44% and 29% of total bulk-deposited N, respectively. Between April and November, the canopy retained 55.5% of the NH4-N in bulk deposition, but only 1.4% of deposited NO3-N.