Abstract
Soil CO2
efflux was measured in clear-cut and intact plots in order to quantify
the impact of harvest on soil respiration in an intensively managed
Eucalyptus plantation, and to evaluate the increase in heterotrophic
component of soil respiration because of the decomposition of harvest
residues. Soil CO2 effluxes showed a pronounced seasonal
trend, which was well related to the pattern of precipitation and soil
water content and were always significantly lower in the clear-cut plots
than in the intact plots. On an annual basis, soil respiration
represented 1.57 and 0.91 kgC m−2 yr−1 in intact and clear-cut plots, respectively. During the first year following harvest, residues have lost 0.79 kgC m−2 yr−1.
Our estimate of heterotrophic respiration was calculated assuming that
it was similar to soil respiration in the clear-cut area except that the
decomposition of residues did not occur, and it was further corrected
for differences in soil water content between intact and clear-cut plots
and for the cessation of leaf and fine root turnover in clear cut.
Heterotrophic respiration in clear-cut plots was estimated at 1.18 kgC m−2 yr−1 whereas it was only 0.65 kgC m−2 yr−1 in intact plots (41% of soil respiration). Assumptions and uncertainties with these calculations are discussed.
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