CO2 FLUXES OF CRYPTOGAMIC CRUSTS .1. RESPONSE TO RESATURATION

The relationship between carbon dioxide exchange of Microcoleus- and Scytonema-dominated cryptogamic crusts and resaturation time was measured in the laboratory with a modified discrete sampling technique and infrared gas analysis. Maximum net photosynthetic rate of Microcoleus was 187 nmol CO2 m-2 s-1 and of Scytonema was 111 nmol CO2 m-2 s-1 for rehydration to 100% soil saturation. Both crust types demonstrated a slow rise in resaturation respiration and took 2 days to become fully active after the first rehydration to 100% soil saturation after long-term dryness, and only one day to become active after the second rehydration cycle.