Prairie dogs (Cynomys spp.) and banner-tailed kangaroo rats (Dipodomys spectabilis) are considered keystone species of grassland ecosystems, and co-occur in the arid grasslands of the southwestern United States and in Mexico. Their keystone status is attributed primarily to the effects of their burrowing and foraging behavior, but they differ ecologically in several important respects. We studied the comparative functional roles of these species where they co-occur at the Sevilleta National Wildlife Refuge, New Mexico, focusing on their impacts on grassland vegetation. We found that vegetation cover, structure, and species richness varied across a gradient extending out from the mound centers, and these patterns differed between prairie dog and kangaroo rat mounds. Certain species and functional groups of plants associated differentially with mounds and landscape patches occupied by prairie dogs and banner-tailed kangaroo rats. Where both species co-occurred locally there was greater soil disturbance, more organic material from their feces, and higher activity of other animals. The overall effect of these rodents was to create a mosaic of different patches across the landscape such that their combined activities increased landscape heterogeneity and plant species richness. Our results demonstrate complementary effects of two co-occurring keystone species on their associated biotic communities.
Mound-Scale Plots: To measure plant species composition and vegetation structure associated with mound disturbance patches, we established replicated small-scale plots with paired mound and non-mound control plots. The mound and control plots were spatially intermixed on each landscape-scale plot. Specifically, transects were centered around 20 prairie dog mounds (fall 1999-spring 2002) and 20 kangaroo rat mounds (fall 2001 and spring 2002 only) on the Pdog+Krat plot, and around 20 kangaroo rat mounds on the Krat plot (fall 2001 and spring 2002).
Five-meter transects were located along the four cardinal directions centered on each mound. Plant canopy cover, height of live foliage, feces, and animal soil surface disturbance were measured on 30 cm x 30 cm quadrats, located at 1 m, 2 m, 3 m, 4 m, and 5 m along each transect line during, although only at 1 m, 3 m, and 5 m during fall 2001 - spring 2002. Transects also were established around a point located 10 m away from the sample mound to represent a non-mound area without mound-associated disturbance. Like the landscape-scale plots, sampling occurred during late spring and early fall.
Additional Metadata: 1/23/2008 (Yang Xia). 1.updated and modified metadata to correct format. 2. Checked data for missing data points and errors. 3. any empty cells were filled in with either -999 for missing data or an NA for not applicable
Updated the metadata 01/09/2009 (Yang Xia)these metadata were entered on 10/30/2008 by Kristin Vanderbilt from metadata supplied by Ana Davidson
Additional Information on the personnel associated with the Data Collection / Data Processing
The Sevilleta Field Crew from 2000-2002 also helped collect data
Additonal Study Area Information
Study Area Name: Pino Gate
Study Area Location: The study site was located near the base of the Los Pinos mountains and directly adjacent to the nothern fencline of the SNWR at Pino GateElevation: 1600 m
Vegetation: Burrograss (Scleropogon brevifolius), sand dropseed (Sporobolus cryptandrus), and black grama (Bouteloua eriopoda) were the dominant vegetation.
Soils: Deep clayey loam soilsGeology: On an upper bajada slope, in a broad swale
Climate: Long-term mean annual precipitation is 243 mm, about 60% of which occurs during the summer. Long-term mean monthly temperatures for January and July are 1.5°C and 25.1°C, respectively.
Site history: Historically, prairie dogs were common throughout the area, but were exterminated by the early 1970’s (John Ford, United States Department of Agriculture Wildlife Services, personal communication). Gunnison’s prairie dogs began to re-colonize the study site from adjacent private land in 1998. During our study, the colony occurred within a 5 ha area, near the base of the Los Piños Mountains in an area with deep clayey loam soils. The site has been long inhabited by kangaroo rats, and represents typical northern Chihuahuan Desert grasslandNorth Coordinate:34.406954South Coordinate:34.406954East Coordinate:106.606269West Coordinate:106.606269