Soil surface disturbance alters cyanobacterial biocrusts and soil properties in dry grassland and shrubland ecosystems
Biological soil crusts (biocrusts) dominate soil surfaces in drylands, providing services that include soil stabilization and carbon uptake. In this study, we investigated the direct and biocrust-mediated effects of anthropogenic disturbances in two dryland ecosystems.
We applied low intensity soil surface disturbance (twice-yearly footfalls) in grassland and shrubland ecosystems in northern Chihuahuan Desert, USA.
After five years of disturbance, biocrust photosynthetic capacity (chlorophyll a) declined by 44%. Declines were largest in interspaces between grassland plants. Levels of scytonemin, a biocrust sunscreen pigment, were 38% greater in shrubland than grassland and 44% greater under grass canopy than in interspaces, but decreased only 5% with disturbance. Disturbance reduced soil surface stability 2 times more in the grassland than shrubland. Disturbance effects on other hydrologic and physical properties were indirectly mediated by the photosynthetic capacity of biocrusts. Disturbance indirectly increased infiltration depth and shallow (2–3 cm) soil moisture in the grassland but reduced surface moisture (<1 cm) in the shrubland.
Biocrusts were more sensitive to low intensity soil disturbance in a grassland than shrubland ecosystem. While biocrusts mediated the effects of soil disturbance on dryland soil hydrological and physical properties, the nature of their influence differed between ecosystem types.
KeywordsBiocrust Bouteloua Soil stability Ecohydrology Larrea tridentata Sevilleta LTER
We thank Jarek Kwiecinski, Elisa Gagliano, Katherine Anderson, Kendall Beals, Jennifer Bell, Katy Beaven, and UNM undergraduate students for lab and field work assistance. Thornton was funded by the Sevilleta REU program (NSF-DBI 1062564), and Chung by the Sevilleta LTER graduate fellowship and NSF Doctoral Dissertation Improvement Grant (NSF-1601210). Support for Dettweiler-Robinson was provided by NSF-1557135. This research was also partially supported by grants from the National Science Foundation to the University of New Mexico for Long-term Ecological Research (SEV-LTER, NSF-1748133, 1440478).
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