Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: December 10, 2006
Publication Date: February 9, 2007
Citation: James, J.J., Davies, K.W., Aanderud, Z.T., Sheley, R.L. 2007. The potential for resource-based niches to contributed to invasion resistance in a semi-arid plant community [abstract]. Society for Range Management. Paper No. 213. Technical Abstract: Understanding the properties that make plant communities less invasible is a central goal of land managers. Emerging theories of invasibility predict that invasion resistance will be directly tied to the ability of the resident vegetation to maintain low levels of a limiting resource. Partitioning of a limiting resource in space, time or form may be one potential mechanism allowing native plant communities to increase total resource capture and thereby confer some degree of invasion resistance. In this field study, we quantified the degree to which soil N is partitioned between native species and functional groups in a model Great Basin bunchgrass community and evaluated how these patterns of resource acquisition relate to patterns of resource capture of cheatgrass and medusahead. The five native species used in this study included three bunchgrasses and two perennial forbs. Patterns of N capture were quantified by injecting 15N -labeled nitrogen three times during the year (early, mid, or late spring) at two depths (2¬7 or 17-22 cm) and in two forms (NO3-or NH4+) around individual plants. The timing of plant N capture was closely linked to phenology. Native bunchgrasses, which initiated growth earlier in the growing season tended to have highest rates of N capture early in the growing season. Native forbs, in contrast, had higher growth rates and N capture later in the growing season compared to bunchgrasses. Differences in depth and form of N capture tended to be more similar between species within a functional group than between species in different functional groups. These preliminary results indicate that significant partitioning of N among native species in depth, time and form may be one mechanism in which functionally diverse plant communities reduce the availability of N to invasive annual grasses.