Effects of Black-Tailed Prairie Dog on Shortgrass Vegetation of Western Kansas

Previous studies indicate the black-tailed prairie dog (Cynomys ludovicianus) alters its environment through grazing, clipping, and burrowing, which affect plant community composition, cover, species richness, and biomass. Previous research has been contradictory, reporting varying degrees of effect with change in geographic location and plant community. Limited research has been conducted on the effects of the black-tailed prairie dog on shortgrass vegetation in western Kansas. Objectives of this study were to characterize the spatial and temporal effects of black-tailed prairie dog on shortgrass prairie in western Kansas. To examine spatial effects, I observed floristic composition, plant basal cover, forb species counts, and aboveground biomass among four treatments: prairie dog plus cattle (PC), prairie dog only (P), cattle only (C), and exclusion of both species (EX). Six replicates of each treatment were observed four times during the 2007 growing season. To examine temporal effects, I observed plant community composition, basal cover, and forb species counts among three colony zones of different ages on eight colonies during the 2008 growing season. I collected data along line transects by using modified step-point, frequency quadrats, and a forage disk. Prairie dogs induced a shift from grazing-tolerant, shortgrass species such as blue grama [Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths] and buffalograss [Buchloe dactyloides (Nutt.) Engelm.] and perennial forbs such as slimflower scurfpea [Psoralidium tenuiflorum (Pursh) Rydb.] and scarlet gaura [Gaura coccinea Nutt. ex Pursh] to grazing-avoided grasses such as purple threeawn [Aristida purpurea Nutt.] and ruderal, annual forbs such as kochia [Kochia scoparia (L.) Schrad.] and Russian thistle [Salsola kali L.]. These compositional shifts became more evident with increasing time of prairie dog habitation. Basal cover was not significantly different among herbivory treatments: PC (31.6 %), P (37.2 %), C (41.7 %), and EX (42.4 %), but temporally, basal cover became reduced with increasing colony age and was significantly (p 0.05) lower in colony zones inhabited for 6 years (19.8 %) than in colony zones inhabited for 4 years (28.6 %) and 2 years (29.5 %). The number of forb species was not significantly different between on-colony (22.6) and off-colony (22.7) sites, or among colony zones inhabited for 6 years (14.6), 4 years (15.2), and 2 years (13.0). Plant biomass was about 1.5 times greater on uncolonized areas than on prairie dog colonies. Prairie dogs and cattle reduced biomass by 977 kg ha-1, and prairie dogs reduced biomass more than cattle, 659 and 246 kg ha-1 respectively. Prairie dogs significantly altered shortgrass vegetation. Prairie dogs and associated environmental effects provide habitat critical for preservation of species such as the black-footed ferret (Mustela nigripes), but vegetational changes induced by prairie dogs might have a negative effect on livestock grazing. On rangeland managed for livestock production, areal extent of prairie dog colonies should be a management consideration.