Biocrust carbon isotope signature was depleted under a C3 forb compared to interspace
Plants and biological soil crusts (biocrusts) are the key producers in drylands, but biocrusts seldom show net CO2 uptake. I hypothesized that biocrusts could augment CO2 fixation by incorporating plant-derived carbon.
I collected biocrusts located at the base of Gutierrezia sarothrae (C3 forb), Bouteloua gracilis (C4 grass), and from bare interspaces between plants, and from a mesocosm experiment with live B. gracilis or dead B. gracilis roots. To trace carbon sources, I determined 13C values of the biocrust community, isolated cyanobacteria and lichen, and plant leaves because the photosynthetic pathway distinguishes the tissue 13C values.
Biocrust communities and washed cyanobacteria and cyanolichen in G. sarothrae microsites were depleted by ~2‰ relative to other locations. Biocrust δ13C did not differ between the interspace and live or dead B. gracilis.
Potential mechanisms for the trend in biocrust δ13C adjacent to C3 plants include differences in microsite conditions, biocrust communities, use of respired CO2 in the soil matrix for photosynthesis, or mixotrophic use of plant photosynthates. Further investigation of this observation may improve understanding of the degree to which the activities of dryland primary producers are coupled.
KeywordsBiological soil crust C3 plant C4 plant Delta 13C Carbon dynamics
Jenn Rudgers, Bob Sinsabaugh, Lee Taylor, Matt Bowker, and four anonymous reviewers provided valuable manuscript feedback. This project originated as a project funded by Zack Sharp’s Stable Isotope Biogeochemistry course and I received feedback from Dr. Sharp and the other students in the course. Viorel Atudorei and Laura Burkemper provided assistance with sample preparation and processing. The Sevilleta Long Term Ecological Research site (NSF DEB #1440478) and Sevilleta Field Station provided logistic support for sampling. I thank my dad, Creighton Robinson, for letting me sample on his property. Manuscript was prepared with support from NSF DEB DDIG#1557135 and NSF DEB #1557135.
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