Sensitivity of boreal forest carbon dynamics to long-term (1989-2005) throughfall exclusion in Interior Alaska)

Abstract

"The objective of this study was to assess the effect of throughfall exclusion (1989-2005) on forest vegetation and soil in upland and floodplain landscape positions. In uplands, imposed drought reduced soil moisture at 5, 10, and 20 cm depths and increased soil C storage by slowing decomposer activity at the surface. In the drought plots, aboveground tree growth was reduced and root biomass in mineral soil was increased. In floodplains, imposed drought did not reduce soil moisture as strongly as it did in uplands, though near-surface soil C storage was still increased as a result of reduced decomposer activity. Floodplain vegetation response to imposed drought differed from that of uplands; imposed drought did not reduce aboveground tree growth but instead reduced root biomass in mineral soil. At both landscape positions, imposed drought accelerated the loss of understory vegetation. Overall, the results of the throughfall exclusion indicated that chronic soil drying is likely to increase forest C storage only in floodplains. In uplands, where soil moisture is more limited, forest C storage is not as likely to change because an increase in soil C may be offset by reduced tree growth"--Leaf iii