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 andscape heterogeneity and plant species richness. Our results demonstrate complementary effects of two co-occurring keystone species on their associated biotic communities.
We compared the vegetation on plots occupied by: 1) both species (Pdog+Krat plot); 2) only kangaroo rats (Krat plot); and 3) both species, but here prairie dogs inhabited one half of the plot and kangaroo rats inhabited the other half (Transition plot).
Vegetation was sampled using a 180 m x 180 m (7x7) grid that extended cross each plot.
Plant canopy cover, height of live foliage, feces, and animal soil disturbance were measured at 30 m intervals on each grid using 1 m x 1 m quadrats. The method was similar to that developed by Huenneke et al. (2001), except that we measured total canopy cover per plant species within each quadrat rather than multiple volumetric measures needed for assessing net primary production. We counted fecal pellets of desert cottontails (Sylvilagus auduboni), black-tailed jackrabbits (Lepus californicus), kangaroo rats, and prairie dogs as a relative measure of their activity and distribution of their nutrient input on the landscape. Soil surface disturbance by kangaroo rats, prairie dogs, and pronghorn antelope (Antilocapra americana) also was measured to evaluate the spatial distribution of their activity on the landscape. Soil disturbance was measured as the percentage of ground cover disturbed by animal tracks, digs, or mounds within each quadrat. Sampling occurred during late spring (April) and early fall (September), from fall 1999 - spring 2002. Historic extermination of prairie dogs at the SNWR was extensive, leaving most of the grasslands inhabited only by kangaroo rats, and making it impossible to locate replicate sites occupied by both species, exclusively by prairie dogs, or by neither species.
The metadata were entered and updated on 01/09/2009 by Yang Xia from metadata supplied by Ana Davidson and Kristin Vanderbilt
Additional Metadata: 1/22/2008 (YX) 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.
Additional 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