LTER Cross-site: Regional Variation in Direct and Indirect Influences of Animals on a Chihuahuan Desert Grasslands

New Mexico State University, Las Cruces NM

Investigators

Abstract

Peters, Debra P New Mexico State University DEB 0087289 "Regional variation in direct and indirect influences of animals o a Chihuahuan Desert grasslands" In Chihuahuan desert grasslands, the loss of grass to shrubs and the reclamation of grasslands from shrublands are important problems in community dynamics that emerge from several direct and indirect processes. The PIs will investigate direct and indirect biotic influences on the persistence and recovery of Chihuahuan desert grass. They propose an assessment of the effects of different animal taxa on the dominant grass species, black grama Bouteloua eriopoda. The will: 1) determine the relative importance of different animal activities for several plant processes and 2) test the hypothesis that variation in local and regional patterns of grass establishment are related to variation in animal activities and abundances. They will perform a series of exclusion experiments on seeds, seedlings, and adult plants inhabiting grass- and shrub-dominated habitats within two Chihuahuan desert LTER sites (the Sevilleta and Jornada and Big Bend National Park). By comparing the effects of animal taxa where grasses are successful versus where they are not, tests of specific hypotheses by which animals influence vegetation will be performed. Specifically, they will examine four hypothesized mechanisms: a) seed loss due to predation by ants and rodents, b) seed protection and increased germination in cache pits dug by rodents, c) mortality and diminished seed production due to herbivory by small mammals and grasshoppers on seedlings and adult plants, and d) the positive effects of nutrient enrichment and/or increased availability of water due to the nesting of scavenging ants under adult plants. These experiments will help us understand animal abundance and grass recruitment at broad scales. The work will clarify the role of animals in generating and maintaining patterns and dynamics in desert grasslands. It will also contribute to a multi-scale perspective on the importance of direct and indirect plant-animal interactions... a research area of ecological significance to many systems.