Complexity in rodent community respones to grassland-shrubland trasititions

TitleComplexity in rodent community respones to grassland-shrubland trasititions
Publication TypeConference Paper
Year of Publication2007
AuthorsCampanella A., Bestelmeyer B, Roemer G., Peters DC
Conference Name87th Annual Meeting American Society of Mammalogist
Date PublishedJune 6-8, 2007
Conference LocationAlbuquerque, NM
ARIS Log Number221827
Keywordsabiotic, biotic, desertification, diversity, rodents
AbstractIt is believed that the abundance and diversity of Chihuahuan Desert rodents increases with shrub encroachment accompanying desertification although grassland specialist species decline with loss of perennial grasses. It has been reported, however, that a suite of biotic-abiotic interactions may influence rodent population responses to spatial variation in habitat in complex ways, mediating the general habitat/abundance relationship. The consistency of rodent responses to shrub encroachment across a landscape and over time has not been examined in the past and is the objective of this study. Between 2002 and 2006 we monitored rodent populations on five grassland-shrubland ecotone sites in the Jornada Basin (NM, USA). The ecotones are within the same vegetation types and soils (Bouteloua eriopoda and Prosopis glandulosa on coarse loamy Argids), but they are dynamic (with shrubs expanding into grasslands over the last century) and varied in total shrub and grass abundance depending on mesoclimate and disturbance history. We also monitored 23 additional grids distributed across an area of 200 square kilometers and ranging from healthy grasslands to dense mesquite dunes. Precipitation at all sites was recorded. We tested the hypothesis that rodent richness, biomass, and density/abundance were highest in shrub-dominated portions of replicate grassland-shrubland ecotones and across grassland-shrubland transitions. We found that overall rodent richness, biomass and abundance were highly variable across the landscape and responses to shrub cover and precipitation were not always linear across years. Perennial grass cover and bare ground cover did not show significant effects on rodent populations. We conclude that absolute differences in shrub cover across the landscape are more important than relative differences in vegetation structure (i.e. shrub cover) within an ecotone for aggregate measures of rodent communities.