Patterns of and controls over nitrogen inputs by green alder (Alnus viridis spp. fruticosa) to a secondary successional chronosequence in interior Alaska I - N2 Fixation and Soil Temperature

We measured rates of nitrogen fixation by Alnus viridis spp. fruticosa and concurrent subcanopy soil temperature at BNZ LTER. To do so we utilized replicate (n=3/stage) stands of a seral sequence of successional stages maintained by the Bonanza Creek Long-Term Ecological Research program (BNZ LTER). At each of the 9 replicate stands we selected a total of 70 individual shrubs. During each of 7 sampling periods, 3 across the growing season of 1997 and 4 during 1998, we randomly selected 10 of 70 A. viridis spp. fruticosa at each replicate stand. We used acetylene reduction assays (ARA) to estimate rates of N2 fixation at each of the selected shrubs and concurrently measured soil temperature at each shrub. The attached database may be utilized to (1) elucidate seasonal trends in rates of N2 fixation by A. viridis spp. fruticosa across a boreal forest chronosequence and (2) investigate soil temperature controls over rates of N2 fixation. It may also be used to statistically analyze differences between years, successional stages and replicates within successional stage in both rates of ARA and temperature.

We developed this database to describe seasonal trends of rates of nitrogen fixation by A. viridis spp. fruticosa across a boreal forest chronosequence and to elucidate soil temperature controls over rates.