Effects of rain events on carbon fluxes from biological soil crusts

摘要

In dry ecosystems, biological soil crusts (BSCs) have been suggested as one of the factors responsible for the large rate of annual C02 net uptake (Xie et al. 2009). However, most studies carried out on carbon (C) fluxes in arid and semi-arid ecosystems, such as soil respiration, have neglected the carbon fluxes from BSCs. Although BSCs are a vital component of the dry-land soil C cycle, few studies have parameterized the conditions required for photosynthesis in BSCs or determined BSCs respiration (Elbert et al. 2009, Castillo-Monroy et al. 2011). Precipitation in dry land is dominated by small events (Lauenroth and Bradford 2009). Even the smallest events will influence the carbon fluxes of BSCs, while intermediate pulses might wet the subsurfacebiotic community, and typically only larger events arc used by plants for carbon gain or growth of roots or shoots (Belnap et al. 2005). As BSCs dry quickly and are hence very responsive to moisture pulses, the pulsed nature of precipitation can lead tohighly variable carbon fluxes from BSCs (Bowling etal. 2011). Therefore, it is very important to study the effect of rain events upon carbon fluxes through BSCs in the dry ecosystem.