Soil Surface Dynamics

Soil Surface Dynamics

Soil Surface Dynamics
  Carl White taking measurements of soil bridges.  Photo taken January 12, 2009.

Most research on microbial soil crusts has been concentrated in the cold desert grasslands of the Colorado Plateau and the Basin and Range region of the western United States.  Relatively little is known about the microbial communities of soils of the warm, semi-arid grassland region of the southwestern United States.

Within the grassland systems of the Sevilleta National Wildlife Refuge (SNWR), located in central New Mexico, wind, rain, and fire are the major agents moving particles at the soil surface.  After being deployed in the field for a year, litterbags utilized in decomposition studies were found to be resting on pedestals of nearly 2 cm of soil.  Thus, a study was initiated within the SNWR to better understand the effects of such forces, particularly fire, on the soil surface.

A major area of investigation was the effect of fire within a landscape dominated by C4 grasses.  Four years following a prescribed burn, data was collected on a range of variables related to soil characteristics and microbial and plant communities. One hypothesis was that the community of soil microbiota adapted to cold-moist conditions would differ from that adapted to the hot-moist conditions of the summer monsoons.

At each study site a soil bridge was placed across two pieces of rebar and thirty points selected for measurement at 5-cm intervals.  At a millimeter-scale, the height of each point on the soil bridge was measured, as was soil surface microtopography.  Soil samples were analyzed for inorganic and mineralizable nitrogen and ammonium.  Material was collected from the soil surface to determine chlorophyll content and the composition of the plant community was described.  Measurements were done twice a year, at the end of spring and near the end of the summer monsoon season.