Post-fire Redistribution of Soil Carbon and Nitrogen at a Grassland– Shrubland Ecotone

TitlePost-fire Redistribution of Soil Carbon and Nitrogen at a Grassland– Shrubland Ecotone
Publication TypeJournal Article
Year of Publication2018
AuthorsWang G, Li J, Ravi S, Dukes D, Gonzales HB, Sankey JB
Accession NumberSEV.796

The rapid conversion of grasslands into shrublands
has been observed in many arid and semiarid regions
worldwide. Studies have shown that fire can
negatively affect shrub communities and promote
resource homogenization, thereby providing some
reversibility to the resource heterogeneity induced
by shrub encroachment, especially in the early
stages of encroachment. Here, we used prescribed
fire in a grassland–shrubland transition zone in the
northern Chihuahuan Desert to test the hypothesis
that fire facilitates the remobilization of nutrientenriched
soil from shrub microsites to grass and
bare microsites and thereby reduces the spatial
heterogeneity of soil resources. Results show that
the shrub microsites had the lowest water content
compared to grass and bare microsites after fire,
even when rain events occurred. Significant differences
of total soil carbon (TC) and total soil
nitrogen (TN) among the three microsites were not
detected 1 year after the fire. The spatial autocorrelation
distance increased from 1 to 2 m, approximately
the mean diameter of an individual shrub
canopy, to over 5 m 1 year after the fire for TC and
TN. Patches of high soil C and N decomposed 1 year
after the prescribed fire. Overall, fire stimulates the
redistribution of soil C and N from shrub microsites
to nutrient-depleted grass and bare microsites,
leading to a decrease in spatial heterogeneity of
these elements. The redistribution of soil C and N
from shrub to grass and bare microsites, coupled
with the reduced soil water content under the
shrub canopies but not in grass and bare microsites,
suggests that fire might influence the competition
between shrubs and grasses, leading to a higher
grass, compared to shrub, coverage in this ecotone.