SGS-LTER Disturbance intensity and above- and belowground herbivory effects on long-term recovery of shortgrass steppe on the Central Plains Experimental Range, Nunn, Colorado, USA 1977-1990

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. Additional information and referenced materials
can be found: http://hdl.handle.net/10217/83444 The importance of disturbance intensity and
herbivory by cattle and white grubs, or the larvae
of June beetles to recovery of shortgrass steppe
ecosystems in Colorado, USA were evaluated over a
14 year time period. Disturbance intensity was
defined by survival of the dominant grass species
(Bouteloua gracilis) after an outbreak of root
feeding activity by white grubs. 16 patches of
vegetation consisting of four pairs of adjacent
ungrazed-grazed by cattle locations with 2
replicates that were recently affected by white
grubs were selected in 1977. Disturbance intensity
was determined in 1977 by the area in each patch
that contained live tillers of B. gracilis.
Permanent plots were lcoated both within and
outside of each patch. Plant basal cover and
density by species were estimated at time of peak
aboveground biomass in 6 different years on each
plot. Successional dynamics on patches was similar
to areas affected by other types of disturbances,
however, rate of recovery was faster for patches
affected by grubs. Grazing by cattle was
infrequently important to plant recovery, a result
similar to effects of grazing on other aspects of
shortgrass steppe. Disturbance intensity was
important to recovery of B. gracilis since tiller
survival in 1977 was linearly related to cover in
each year of sampling. For ungrazed patches,
initial conditions were important to recovery of
B. gracilis for as many as 14 years. For grazed
patches, initial conditions decreased and grazing
increased in importance through time. Changes in
resource quality and more uniform distribution of
roots due to grazing likely resulted in more
complete mortality of plants by grubs under grazed
compared to ungrazed conditions. Persistance of
shortgrass steppe ecosystems in spite of
disturbances with different intensities are
determined at least in part by characteristics of
disturbances interacting with the ability ofplants
to respond, and in part by the evolutionary
history of the system. Although white grubs affect
shortgrass communities infrequently, they have
large and important effects on plant community
structure through time, and represent an important
class of disturbance defined by intensity.