PARENT SESSION
Oral Session #55: Fire Ecology. Presiding: M. Moritz.
Wednesday, August 8, 2001. 1:00 PM to 5:00 PM. Hall of Ideas H.
Nitrogen mineralization and phenol accumulation along a fire chronosequence in northern Sweden .
DeLuca, Thomas1,2, Nilsson, Marie-Charlotte 2, Zackrisson, Olle2, 1 2
ABSTRACT- Boreal Scots pine (Pinus sylvestris) forests of northern Sweden are often considered to be N limited. This N limitation has likely been exacerbated by the elimination of wildfire as a natural disturbance factor. Phenolic inhibition of N mineralization and nitrification is often invoked when discussing N limitation of these forests, however such allusions greatly remain hypothetical. Nitrogen mineralization, nitrification and presence of free phenolic compounds were assessed along a fire chronosequence in northern Sweden. Ionic resins were used to assess net N mineralization and nitrification and non-ionic carbonaceous resins were used to non-destructively assess free phenolic compounds in forest stands aged 2 to 350 years since last fire. Plots were analyzed at each site to assess understory vegetation and depth of forest floor (Oi/Oe/Oa horizons). Significant correlation between site age and N transformations were observed. Nitrification followed a logarithmic decrease with time (R2 = 0.80, P< 0.005) that may suggest inhibition of nitrification as a result of the rapid increase in ericaceous vegetation and loss in sorption potential of charcoal with time. Net N mineralization followed a gradual linear decrease with time (R2 = 0.61, P< 0.05). Supporting field studies at one site further support the notion that nitrification may actually be inhibited or absent in late successional forests, whereas net N mineralization appears to be simply limited by rapid immobilization and a lack of labile N.
KEY WORDS: ericoids, boreal, allelopathy, charcoal