The differential effects of sand burial on CO2, CH4, and N2O fluxes from desert biocrust-covered soils in the Tengger Desert, China.

Biocrusts are a crucial component of desert ecosystems, playing a significant role in greenhouse gas fluxes when they cover soils. However, little is known about whether, and how sand burial, one of the most common disturbances affecting the biodiversity and ecological function of biocrusts, influences fluxes of CO 2 , CH 4 , and N 2 O from the desert biocrust-covered soils. Based on measurements of the fluxes of three greenhouses gases from soils covered with two kinds of biocrusts separately dominated by mixed (i.e., approximately 50% algal coverage and 50% lichen coverage of Endocarpon pusillum Hedw., here cyanobacteria are classed as algae) and moss (i.e., 100% coverage of Didymodon vinealis (Brid.) Zand.) crusts respectively, followed by zero (control), 1 mm (shallow burial), and 10 mm (deep burial) burial depths of sand, we studied the effects of short (20 days) and relatively long periods (one year) of sand burial on the fluxes of three greenhouse gases as well as their relationships with soil temperature and moisture at Shapotou on the southeastern edge of the Tengger Desert. The results of this study showed that sand burial had a significantly positive effect on emission fluxes of CO 2 and a negative effect on uptake of CH 4 by soils covered with the two types of biocrusts ( P < 0.05), but had a differential effect on N 2 O fluxes depending on burial depth. Shallow burial dramatically increased N 2 O emissions from the biocrust-covered soils ( P < 0.05), but the opposite was observed under deep burial. As burial time increased, the increase of CO 2 emissions decreased, but changes in fluxes of CH 4 and N 2 O varied with biocrust types and burial depths, respectively. In addition, results showed that CO 2 fluxes from the two biocrusts were closely related to soil temperature and moisture; thereby increased with the raised soil temperature at 5 cm depth and soil moisture caused by sand burial. In contrast, CH 4 and N 2 O emissions were not clearly related to temperature or moisture. Overall, the increase in global warming potential caused by sand burial indicates that this kind of deposition may aggravate the greenhouse effect of desert areas covered with biocrusts. [ABSTRACT FROM AUTHOR]