| Forested wetlands are recognized as long-term terrestrial carbon (C) sinks, so they are very important in global C accounting. Harvest disturbance plays an important role in forested wetland ecosystems, since harvest can turn wetlands into a C source if soil respiration is stimulated more than photosynthesis. Daxing’anling is one of the main areas of Chinese forested wetlands, however, effects of harvesting on ecosystem C storage for boreal forested wetlands are still poorly understood. The aim of this study was to evaluate the short-term effects of selective harvest on ecosystem C storage and C sequestration for Larix gmelinii-Carex schmidtii forested wetlands in Daxing’anling, northeast China, by measuring and comparing changes in its total ecosystem C storage (biomass, litter, and soil C pools) and annual C sequestration under four harvest treatments (0.0%-uncut,25%-low,35%-moderate and50%-high of total volume) after5years, so as to provide references for managing wetland resources. We found that:(1) Total vegetation biomass and total vegetation C storage varied from135.03±7.72to204.71±1.71t/hm2and61.16±0.67to99.61±1.47t C/hm2at the various harvest sites and decreased significantly by8.7%-34.0%and15.5%±38.6%, respectively, as harvest intensity increased when comparing the three harvest intensities (P<0.05). The decrease in total vegetation biomass mainly resulted from significant reductions of tree biomass, which comprise the dominant component (91.5%±96.0%) of this forested wetland type, although harvest could increase the understory biomass and reduce the litter biomass, both of which had only limited impacts on total vegetation biomass. Thus, all selective harvest intensities significantly reduced the vegetation C storage;(2) Low intensity harvest (208.82±26.28t/hm2) increased the soil C storage by16.2%, however, both moderate-(90.14±59.02t/hm2) and high-intensity (122.25±42.56t/hm2) harvest caused significant reductions (30.1%±48.5%,P<0.05) relative to174.93±37.19t/hm2in the uncut stand, respectively. Therefore, low intensity harvest should be adopted to manage Larix gmelinii-Carex schmidtii forested wetlands from the C sequestration point of view;(3) Low intensity harvest (293.03±29.34t C/hm2) led to a mild increase by6.7%in the total ecosystem C storage while moderate-(160.32±55.05t C/hm2) and high-intensity (183.41±46.27t C/hm2) harvest resulted in significant reductions (33.2%-41.6%, P<0.05) compared with the uncut stand (274.54±39.70t C/hm2);(4) Significantly greater total NPP (69.1%-83.2%) and annual C sequestration (52.0%-78.7%) were in the low-(11.87±0.92t ha-1yr-1and6.29±0.92t C·ha-1yr-1) and moderate-(10.96±0.95t ha-1yr-1and5.35±0.85t C·ha-1yr-1) intensity harvest stands compared to the high intensity harvest and uncut stands (8.28±0.48t ha-1yr-1,5.08±0.57t C-ha-1yr-1and6.48±0.28t ha-1yr-1,3.52±0.21t C·ha-1yr-1). Therefore, it appears that both low-and moderate-intensity harvest may be capable of enhancing the efficiency of NPP and C sequestration capacity of this type of forested wetland.Finally, it appears that low intensity harvest may not only be capable of sustaining the ecosystem C sink for this forested wetland type, but restore its C sequestration capacity more efficiently. |
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