SGS-LTER Impact of Labile and Recalcitrant Carbon Treatments on Plant Communities (Basal Cover) in a Semiarid Ecosystem on the Central Plains Experimental Range, Nunn, Colorado, USA 1997-2012, ARS Study Number 3

This data package was produced by researchers
working on the Shortgrass Steppe Long Term
Ecological Research (SGS-LTER) Project,
administered at Colorado State University.
Long-term datasets and background information
(proposals, reports, photographs, etc.) on the
SGS-LTER project are contained in a comprehensive
project collection within the Digital Collections
of Colorado
(http://digitool.library.colostate.edu/R/?func=collections&collection_id=3429).
The data table and associated metadata document,
which is generated in Ecological Metadata
Language, may be available through other
repositories serving the ecological research
community and represent components of the larger
SGS-LTER project collection. In a 10-year study, we assessed the influence
of five carbon (C) treatments on the labile C and
nitrogen (N) pools of historically N enriched
plots on the Shortgrass Steppe Long Term
Ecological Research site located in northeastern
Colorado. For eight years, we applied sawdust,
sugar, industrial lignin, sawdust + sugar, and
lignin + sugar to plots that had received N and
water additions in the early 1970s. Previous work
showed that past water and N additions altered
plant species composition and enhanced rates of
nutrient cycling; these effects were still
apparent 25 years later. We hypothesized that
labile C amendments would stimulate microbial
activity and suppress rates of N mineralization,
whereas complex forms of carbon (sawdust and
lignin) could enhance humification and lead to
longer-term reductions in N availability. Results
indicated that of the five carbon treatments,
sugar, sawdust, and sawdust + sugar suppressed N
availability, with sawdust + sugar being the most
effective treatment to reduce N availability. The
year after treatments stopped, N availability
remained less in the sawdust + sugar treatment
plots than in the high-N control plots. Three
years after treatments ended, reductions in N
availability were smaller (40-60%). Our results
suggest that highly labile forms of carbon
generate strong short- term N sinks, but these
effects dissipate within one year of application,
and that more recalcitrant forms reduce N longer.
Sawdust + sugar was the most effective treatment
to decrease exotic species canopy cover and
increase native species density over the long
term. Labile carbon had neither short- nor
long-term effects on exotic species. Even though
the organic amendments did not contribute to
recovery of the dominant native species Bouteloua
gracilis, they were effective in increasing
another native species, Carex eleocharis. These
results indicate that organic amendments may be a
useful tool for restoring some native species in
the shortgrass steppe.