Biocrust carbon exchange varies with crust type and time on Chihuahuan Desert gypsum soils

Authors: HOELLRICH, MIKAELA - New Mexico State University; James, Darren; BUSTOS, DAVID - Us National Park Service; DARROUZET-NARDI, ANTHONY - University Of Texas - El Paso; SANTIAGO, LOUIS - University Of California, Riverside; PIETRASIAK, NICOLE - New Mexico State University

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2023
Publication Date: 5/10/2023
Citation: Hoellrich, M.R., James, D.K., Bustos, D., Darrouzet-Nardi, A., Santiago, L.S., Pietrasiak, N. 2023. Biocrust carbon exchange varies with crust type and time on Chihuahuan Desert gypsum soils. Frontiers in Microbiology. 14. Article 1128631. https://doi.org/10.3389/fmicb.2023.1128631.
DOI: https://doi.org/10.3389/fmicb.2023.1128631

Interpretive Summary: This study measured carbon gas exchange over time from different types of biocrust on gypsum soils at White Sands national Park. It found that different biocrust types do not fix carbon at the same rate, and these rates can vary year to year. Understanding the dynamics of biocrust carbon fixation will enable better calibration of carbon cycling models and impacts of global climate change to dryland carbon cycling.

Technical Abstract: In dryland systems, biological soil crusts (biocrusts) can occupy large areas of plant interspaces, where they fix carbon following rain events. Although distinct biocrust types contain different dominant photoautotrophs, to date only a few studies have documented carbon exchange over time from various biocrust types. This is true especially for gypsum soils. Our objective was to assess the carbon gas exchange of biocrust types established at the world’s largest gypsum dune field at White Sands National Park. We sampled five different biocrust types on a sand sheet location in three different years and seasons (summer 2020, fall 2021, and winter 2022) for carbon exchange measurements in controlled lab conditions. Biocrusts were rehydrated to field capacity and light incubated for 30min, 2hr, 6hr, 12hr, 24hr, and 36hr. Samples were subjected to a twelve-point light regime with a LI-6400XT photosynthesis system to assess carbon exchange. Biocrust carbon exchange values differed by biocrust type, incubation time since wetting, and time of field sampling. Lichens and mosses had higher gross and net carbon fixation rates than dark and light cyanobacterial crusts. High respiration rates were found after 0.5 hr and 2 hr incubation times as communities recovered from desiccation, leveling off after 6 hr incubation. Net carbon fixation of all types increased with longer incubation time primarily as a result of decreasing respiration which suggests rapid recovery of biocrust photosynthesis across types. However, net carbon fixation rates varied from year to year likely as a product of time since the last rain event and environmental conditions preceding collection, with moss crusts being most sensitive to environmental stress. Ultimately, given the complexity of biocrust carbon exchange, it is especially important to consider a multitude of factors when comparing rates across studies. Understanding the dynamics of biocrust carbon fixation will enable better calibration of carbon cycling models and impacts of global climate change to dryland carbon cycling.