Anthropogenic disturbances reduce soil organic carbon (SOC) and soil inorganic carbon (SIC) in surface soils and change soil C (carbon) cycling. SIC is the dominant form of soil C in deserts, with its formation heavily dependent on root and microbial respiration. SOC inputs may be reduced from alterations in plant and soil microbial activity. Currently, deserts are subject to extreme land-use changes including utility-scale solar projects, which often involve vegetation removal. Recovery from natural disturbances takes decades to centuries, due to low recruitment and soil C accumulation rates. Habitat restoration may increase the rate of soil C recovery. Thus, understanding changes in soil C processes related to disturbances and habitat restoration is critical to maximize soil C conservation.
An experiment was designed to test the effects of habitat restoration on soil C dynamics in creosote bush shrub in the Colorado Desert. Larrea tridentata shrubs were transplanted into a disturbed area where the vegetation had been removed ~20 years prior. CO2 flux measurements and soil samples were collected at multiple time points before and after transplanting to quantify differences in soil C and CO2 flux between restored, disturbed, and intact soils.
CO2 flux of dry soils was low with no differences between treatments. After rain, intact soils had the highest CO2 flux from increased microbial and root activity. Restored soils had intermediate CO2 flux while disturbed soils had the lowest flux after rain. Release of CO2 from disturbed soils suggests that microbes may be stimulated by rain and SIC releases more CO2 after a rain event. Furthermore, restoration may encourage reestablishment of previously lost soil microbial activity as CO2 flux was higher in restored plots than disturbed plots.
Following a similar pattern as CO2 flux, total C, SOC, SIC, and microbial C were highest in intact soils and lowest in disturbed soils. This further suggests that vegetation removal alters various soil C pools and may reduce the ability of desert soils to sequester C. Restored soils had slightly higher amounts of soil C than disturbed soils, which will increase over time as L. tridentata shrubs develop resource islands. Disturbances, such as vegetation removal to accommodate renewable energy developments, negatively impacts soil C dynamics, leading to unintended increased soil C losses. Habitat restoration may be a feasible strategy to mitigate soil C losses and facilitate soil C recovery post-disturbance.