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

Mikaela R Hoellrich; Darren K James; David Bustos; Anthony Darrouzet-Nardi; Louis S Santiago; Nicole Pietrasiak

doi:10.3389/fmicb.2023.1128631

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

Front Microbiol. 2023 May 10:14:1128631. doi: 10.3389/fmicb.2023.1128631. eCollection 2023.

Authors

Mikaela R Hoellrich¹, Darren K James², David Bustos³, Anthony Darrouzet-Nardi⁴, Louis S Santiago⁵, Nicole Pietrasiak^{1

6}

Affiliations

¹ Plant and Environmental Sciences, New Mexico State University, Las Cruces, NM, United States.
² USDA-ARS Jornada Experimental Range, New Mexico State University, Las Cruces, NM, United States.
³ US DOI White Sands National Park, Alamogordo, NM, United States.
⁴ Biological Sciences, The University of Texas at El Paso, El Paso, TX, United States.
⁵ Botany and Plant Sciences, University of California, Riverside, Riverside, CA, United States.
⁶ School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV, United States.

Abstract

Introduction: In dryland systems, biological soil crusts (biocrusts) can occupy large areas of plant interspaces, where they fix carbon following rain. Although distinct biocrust types contain different dominant photoautotrophs, few studies to date have documented carbon exchange over time from various biocrust types. This is especially true for gypsum soils. Our objective was to assess the carbon exchange of biocrust types established at the world's largest gypsum dune field at White Sands National Park.

Methods: We sampled five different biocrust types from 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 full saturation and light incubated for 30 min, 2, 6, 12, 24, and 36 h. Samples were then subject to a 12-point light regime with a LI-6400XT photosynthesis system to determine carbon exchange.

Results: Biocrust carbon exchange values differed by biocrust type, by incubation time since wetting, and by date 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 h and 2 h incubation times as communities recovered from desiccation, leveling off after 6 h 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 at our study sites.

Discussion: Given the complexity of patterns discovered in our study, it is especially important to consider a multitude of factors when comparing biocrust carbon exchange rates across studies. Understanding the dynamics of biocrust carbon fixation in distinct crust types will enable greater precision of carbon cycling models and improved forecasting of impacts of global climate change on dryland carbon cycling and ecosystem functioning.

Keywords: Clavascidium; Peltula; White Sands National Park; carbon fixation; cyanobacteria; desiccation recovery; dryland.