Ammonium and nitrate content availability of soils in relation to microbial activity across forest stand age in chronosequence.

Abstract

Both ammonium (NH4) and nitrate (N03) have been proven to be crucial building components of accumulating plant biomass in forests (Knute et. al, 1984 & Pastor et. al, 1984). We wanted to examine the volumetric relationships between the microorganisms that process these compounds and the amount of the compounds themselves throughout a secondary successional forest of different stand ages. We sampled 45 plots in the A soil horizon throughout the University of Michigan Biological Station burn plot chronosequence from 3 different forest age stands, comparing differences of NH4 , N03 , total microbial mass and amino N content between sites. We found significant differences between NH4 and N03 content as well as a significant relationship between amino N and NH4 across stand age. In addition to N03 and NH4 interactions and cycling properties with biomass accumulation and nutrient leaching, these differences in data could be related to the unique attributes of forests in different successional periods such as amounts of leaf litter , species composition, or soil pH (Knute et. al, 1984, Mcclung, G; Stenger 1995; Bauhus & Cole, 1998).