HR: 0800h
AN: B11D-0772    [Abstracts]
TI: Soil respiration from a boreal forest fire scar chronosequence
AU: * Smith, D
EM: drs20@le.ac.uk
AF: Department of Geography Univesity of Leicester, University Road, Leicester, LE17RH, United Kingdom
AU: Kaduk, J
EM: jk61@le.ac.uk
AF: Department of Geography Univesity of Leicester, University Road, Leicester, LE17RH, United Kingdom
AU: Balzter, H
EM: hb91@le.ac.uk
AF: Department of Geography Univesity of Leicester, University Road, Leicester, LE17RH, United Kingdom
AU: Wooster, M
EM: martin.wooster@kcl.ac.uk
AF: Department of Geography King's College London, Strand, London, WC2R 2LS, United Kingdom
AU: Mottram, G
EM: gareth.mottram@kcl.ac.uk
AF: Department of Geography King's College London, Strand, London, WC2R 2LS, United Kingdom
AB: Climate change predictions suggest that warming is to be most pronounced at high latitudes, with a possibility of boreal forest warming of 4-6°C in the next 50-100 years. This has lead to the suggestion that changes in boreal forest soil carbon (C) storage could significantly alter the global soil C balance. Fire is the most significant factor controlling succession in the boreal forest biome and it is possible that climate change will lead to an increase in fire regime e.g. size, frequency, intensity, or any combination of these. Our research is investigating C flux dynamics in a Canadian boreal forest jack pine (Pinus banksiana Lamb.) dominated fire scar chronosequence. Fieldwork is carried out at Sharpsand Creek experimental burn site, near Thessalon, Ontario, Canada, where there are numerous fire scars of different ages. In June 2006 soil respiration (Rs), soil temperature (Ts) and soil moisture (Ms) were measured on three replicate scars selected from plot last burnt in 1948 and 1991. Rs values were later adjusted for Ts using a Q10 value of 2. There was no significant difference in mean adjusted Rs between the two scar age categories. It is likely that sample sizes were not large enough here to detect significant differences. In May 2007, large areas of the field site burnt as a result of wildfire; this provided an opportunity to take a large number of Rs measurements from recently burnt fire scars, as well as from those areas unaffected by the burn. Rs, Ts and Ms measurements were taken from 1948, 1975 and 1991 scar age categories (three replicate scars each) that were burnt in 2007, as well as a 1948 and 1991 fire scar that was unaffected by the wildfire. Soil samples were taken from three locations per fire scar surveyed and analysed in the laboratory for total C content. There was a significant difference in mean Rs adjusted for Ts and Ms (Rsadj) between the three pre-2007 fire scar age categories 1948, 1975 and 1991, that were all burnt in 2007. Mean Rsadj differed significantly between the 1948 and 1991 scars that were not burnt in 2007. A significant difference was apparent in mean Rsadj between the 1948 scar not burnt in 2007 and the three 1948 scars that were burnt in 2007. There was a significant difference in mean Rsadj between the 1991 scar not burnt in 2007 and the three 1991 scars burnt in 2007. Finally mean (Rsadj) differed significantly between the 1948 scar not burned in 2007, 1991 scar not burnt in 2007 and the 9 scars burnt in 2007. Our results indicate that Rs rates vary between fire scars of different ages and it seems that this is also apparent days after burning of scars that differ in their burn history. It appears that Rs from fire scars previously burnt in 1948 and subjected to fire in 2007, decreased as a direct result of the fire. In contrast, Rs from fire scars previously burnt in 1991 and subjected to fire in 2007, increased as a result of the fire. These results suggest that Rs is dominated by autotrophic components in mature forest (59 years post fire), but heterotrophic components in younger forest (16 years post fire). The possibility that Rs is increased directly after burning of younger fire scars is an important finding considering the view that climate change in boreal systems may increase the frequency of forest fires, and hence the proportion of younger forest. More research is needed in other boreal systems and in monitoring Rs for longer time periods after fire on scars with different burn histories.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0466 Modeling
SC: Biogeosciences [B]
MN: 2007 Fall Meeting