The influence of kangaroo rat mounds on species diversity and abundance in two grassland types at a semi-arid ecotone.
KROEL-DULAY, G.* 1, T.HOCHSTRASSER 2 and D.P.C.PETERS 3
HAS, Vacratot, H-2163 Hungary 1
Colorado State University, Fort Collins, CO 80523 USA 2
USDA-ARS, Jornada Experimental Range, Las Cruces, NM 88003 USA 3
Our objective was to evaluate the effects of kangaroo rat mounds on species diversity and composition at a semiarid-arid grassland ecotone. We expected that source populations of plants occurring on kangaroo rat mounds have important influences on species composition of vegetation at the landscape scale, and that these influences differ by grassland type. Our study was conducted at the Sevilleta LTER in New Mexico, where a grassland type dominated by Bouteloua gracilis , a shortgrass steppe species, and a grassland dominated by B. eriopoda , a desert grassland species, meet to form patches across the landscape. Four 0.4 ha plots were sampled for species diversity and composition within a 7m by 7m grid in each grassland type. Kangaroo rat mounds were also mapped and sampled for vegetation measures in 4 areas of 1.6 ha in each type. The landscape scale abundance of many subordinate species was increased significantly by populations occurring on kangaroo rat mounds in both grassland types. However, the area affected by the burrowing activity of kangaroo rats was twice as large in the B. eriopoda dominated grassland type. Furthermore, dominant plants on mounds in the B. eriopoda type were also abundant in off-mound areas whereas dominant plants on mounds in the B. gracilis type were not as abundant off-mound. These results indicate that the presence of mounds in the B. gracilis dominated type is creating islands of plant communities that are distinct from the rest of the grassland. Therefore, the occurrence of certain plant species in this grassland type may be intimately associated with the disturbance regime at this ecotone. This study demonstrates that effects of small animals may increase the coexistence of species at this ecotone.
Keywords: Kangaroo rats, plant diversity, source-sink
This abstract is being presented at: 10:30 AM in session:
Poster Session #12: Disturbance Ecology.