This dataset contains photosynthetic light response and carbon fixation data from biological soil crusts collected at four locations in the Chihuahuan Desert. This study aims to 1) assess the carbon fixation capacity of biocrust types under varying incubation times; 2) assess biocrust nitrogen fixation capacity; 3) understand microbial community composition as well as biomass differences within these biocrust types; and 4) identify how geographic location and soil properties can explain differences seen in carbon fixation and microbial diversity. In order to characterize the physiology of biocrust types at a range of Chihuahuan Desert sites, intact, replicate samples of five soil crust types were collected from each of 4 sites in southern New Mexico, USA: the Jornada Experimental Range (near T-West), the A-Mountain BLM site, the Volcanic BLM site, and White Sands Missile Range. Data and sample collection occurred between May and July of 2020, and the soil crust types of interest were light cyanobacterial, dark cyanobacterial, Peltula lichen, Clavascidium lichen, and moss crusts (n=5 samples for each site & type). After collection, crust subsamples were sequenced, targeting the 16S rRNA gene region for bacteria (see EDI dataset knb-lter-jrn.210549001 and linked data at NCBI), and then subjected to an incubation and photosynthetic response measurements. The intact crusts were incubated under low light, and C fixation was then observed under 12-point light regime in a LI-6400XT photosynthesis analyzer leaf chamber after incubation periods of 30min, 2hr, 6hr, 12hr, and 24hr (5 reps for each condition). The resulting light response curves were used to calculate photosynthetic information in R for the purpose of comparing biocrust type, site, and time response differences and upscale carbon flux values to landscape scale. This data set includes the light response curve values and photosynthetic data calculated from these curves. This data set also includes raw LICOR output files compiled into four Excel workbooks that data was extracted from. This study is complete.