Biocrust disturbance experiment soil responses 2016

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. Results. 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. Conclusions. 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.