Soil uptake of carbonyl sulfide in subtropical forests with different successional stages in south China

摘要

The uptake rates of carbonyl sulfide (COS) by soils in subtropical forests with different successional stages were measured using static chambers in Dinghushan Biosphere Reserve (DBR) in south China from July 2004 to March 2005. The three typical tropical forests studied included monsoon evergreen broad-leaf forest (BF), pine and broad-leaf mixed forest (MF) and pine forest (PF), representing forests with different succession stages in the region. COS exchange rates were also compared between the plots with litter-fall remaining (plots L) and those with litter-fall removed (plots S) in each forest. Results showed that these forest soils all acted as sinks for COS with exchange rates of -1.22 to -11.82 pmol m-2 s-1. The MF in the midsuccessional stage had significantly higher uptake rates, and the mean exchange rates in the BF, MF, and PF were -3.90, -4.77, and -3.65 pmol m-2 s-1, respectively. COS uptake rates at plots L were higher than those at plots S. Mean COS fluxes were significantly higher in March (-6.06 pmol m-2 s-1) than those in July (-3.60 pmol m-2 s-1), August (-3.82 pmol m-2 s-1), September (-3.45 pmol m-2 s-1), and October (-3.54 pmol m-2 s-1). Significant correlation was observed between the COS uptake rates and soil respiration rates or microbial biomass, indicating that microbial activity was an important factor controlling the soil uptake of COS. Significant correlations between COS fluxes and initial COS mixing ratios were only observed in the BF and MF. COS fluxes showed no correlation with soil temperature or water content alone in any of the three forests, but do correlate well with soil temperature and water content together in polynomial forms with an order of 2.