HR: 1340h
AN: B43A-0243    [Abstracts]
TI: Spatio-temporal Variability of Soil Respiration Across an Age-chronosequence of Four Temperate Afforested White Pine ( Pinus Strobus L.) Stands in Ontario, Canada
AU: * Khomik, M
EM: khomikm@mcmaster.ca
AF: School of Geography and Earth Sciences, 1280 Main St West, Hamilton, ON L8S 4K1 Canada
AU: Arain, A M
EM: arainm@mcmaster.ca
AF: School of Geography and Earth Sciences, 1280 Main St West, Hamilton, ON L8S 4K1 Canada
AB: Temporal and spatial variability of soil respiration (Rs) across four (60, 30, 15 and 1 year old), temperate, afforested, white pine ( Pinus Strobus L.) stands was examined in order to investigate age-related differences. Data from two years of measurements (June 2003 to May 2005) was analyzed. Measurements were conducted along transects at each stand, on a biweekly to monthly basis throughout the year, using a portable IRGA system. It was hypothesized that Rs would increase with stand age across the chronosequence and spatial variability would be more profound at the older stands. However, in both years, observed Rs at the 15-year-old stand was comparable to that of the 60-year-old stand and higher than that of the 30-year-old stand. Furthermore, during spring and into early summer, the 1-year-old stand showed higher Rs values compared to the rest of the stands. During the first year, observed Rs ranged from 0.2 to 4.9, 0.2 to 3.8, 0.4 to 5.2, 0 to 2.8 μmol CO₂ m^-2 s^-1 for the 60-, 30-, 15- and 1-year old stands, respectively, while during the second year it ranged from 0.3 to 3.7, 0.3 to 3.1, 0.3 to 3.8, 0.2 to 3.2 μmol CO₂ m^-2 s^-1. Maximum Rs values occurred towards the end of the summer and minimum during winter. Seasonal variability of soil temperature at 15 cm depth was able to explain 62-97% and 84-95% of the seasonal variability of Rs across the stands, during the two respective years. Q₁₀-values for 2003-2004 study year ranged from 2.3 to 4.1 and for the 2004-2005 study year from 2.9 to 3.8. Differences of mean Rs between the sites were attributable to differences in stand physiology. Spatial variability of Rs also did not follow the hypothesized age-pattern. The degree of spatial variability at each stand was seasonal (3 to 63% covariance range observed in 2003-2004 and 0 to 30% in 2004-2005), following the seasonal trend of average Rs for the stand. There was no strong relationship between spatial variability of soil nutrients (ex. N, P, Mg, Ca, K, etc) and spatial variability of Rs at each site. The results of this study suggest that age alone is not a good predictor of temporal or spatial variability of Rs in forest ecosystems. Other stand characteristics, such as stem density, LAI, ground cover and soil organic matter should also be considered.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0438 Diel, seasonal, and annual cycles (4227)
SC: Biogeosciences [B]
MN: Fall Meeting 2005