CARBON FIXATION OF CYANOBACTERIAL–ALGAL CRUSTS AFTER DESERT FIXATION AND ITS IMPLICATION TO SOIL ORGANIC CARBON ACCUMULATION IN DESERT

Enhanced carbon fixation in soil crusts may facilitate the restoration of damaged ecosystems, but this requires greater knowledge of carbon fixation patterns and mechanisms. We measured the net photosynthetic rate (P-n) and estimated annual carbon fixation (ACF) in cyanobacterial-algal crusts after desert fixation in the Tengger Desert, northwestern China. The accumulated carbon fixation since the establishment of a restoration site was also calculated. In addition, stepwise regression analysis was used to study the relation between P-n and ACF and the physicochemical properties of crusts. Results showed that P-n was significantly higher at a more established 51-year-old restoration site (1 57 mu molm(-2)s(-1)) than at a younger 15-year-old site (0 92 mu molm(-2)s(-1)). The ACF also increased significantly with restoration time, but in two temporal phases, a slower ACF phase between 15 and 26years of restoration (0 28 -0 7 gCm(-2)y(-1)) and a high ACF phase after 43-51years of restoration (3 3 gCm(-2)y(-1)). Stepwise regression analysis revealed that P-n was significantly correlated with chlorophyll a and crust cover, whereas ACF was only correlated with crust cover. Accumulated carbon fixation increased from 2 9 gCm(-2) after 15years to 35 4 gCm(-2) at 51years following establishment of the restoration site. The accumulated carbon fixation was positively correlated with soil organic carbon content. This study demonstrated that carbon fixation by cyanobacterial-algal crusts increased progressively after desert fixation. Artificial measures, like the establishment of these restoration zones, can facilitate the colonization and development of biological soil crusts and are an effective biological tool for desert soil restoration. Copyright (c) 2011 John Wiley & Sons, Ltd.