@article {JRN54583, title = {Effects of exurban development on trophic interactions in a desert landscape}, year = {2016}, abstract = {

Context. Mechanisms of ecosystem change in urbanizing landscapes are poorly understood, especially in exurban areas featuring residential or commercial development set in a matrix of modified and natural vegetation. We asked how development altered trophic interactions and ecosystem processes in the matrix.
Objectives. We examined the effect of varying degrees of exurban development (housing density) on a trophic system that included an apex mammalian predator (coyote, Canis latrans), mammalian herbivores (lagomorphs and rodents), and herbaceous plants. We tested the hypothesis that plant recruitment would be negatively affected by exurban development due either to increases in herbivores associated with increased resource availability (a bottom{\textendash}up effect) or to a reduction in predators that avoid humans (a top{\textendash} down effect).
Methods. In Las Cruces, New Mexico, USA, four replicate sites were located in each of three urbanization levels: high density exurban, low density exurban, and wildland dominated by Chihuahuan Desert vegetation. Seedling trays measured herbivory rates, live trapping estimated abundance of pocket mice and kangaroo rats, and remotely-triggered wildlife cameras estimated the activity of lagomorphs and coyotes.
Results. Increased herbivory on seedlings and decreased herbaceous plant recruitment were observed in high density exurban areas. Overall rodent abundance, seed consumption rates, and activity of the lagomorph Lepus californicus did not vary with urbanization level. Activity by another lagomorph, Sylvilagus audubonii, and coyotes was highest in dense exurban areas, consistent with a bottom{\textendash}up effect.
Conclusions. Exurban development can have important indirect effects on trophic interactions occurring in adjacent, untransformed ecosystems. Similar to earlier studies, such effects in the Chihuahuan Desert may be mediated by bottom{\textendash}up processes associated with anthropogenic inputs.

}, keywords = {Chihuahuan Desert, coyote, lagomorph, plant recruitment, rodent, urbanization}, doi = {10.1007/s10980-016-0403-9}, url = {/files/bibliography/16-025.pdf}, author = {Kristen Davanon and Lindsey Howard and Karen Mabry and Robert L. Schooley and Brandon T Bestelmeyer} } @conference {JRN54443, title = {The effects of urbanization on trophic interactions in a desert landscape}, booktitle = {100th Annual Meeting of the Ecological Society of America}, year = {2015}, month = {08/2015}, address = {Baltimore, MD}, abstract = {

Background/Question/Methods: Trophic systems can be affected through top-down (predators) and bottom-up (resources) impacts. Human activity can alter trophic systems by causing predators to avoid areas (top-down) or by providing increased resources through irrigation and decorative plants that attract herbivores and their predators (bottom-up). Both processes may constrain the recruitment of herbaceous plants. We examined the effect of increasing urbanization within Las Cruces, NM, on a trophic system that included mammalian predators, mammalian prey, and herbaceous plants within natural shrubland vegetation. We tested the hypotheses that urbanization could cause a top-down effect in which predator abundance is reduced in more dense exurban areas, or urbanization could cause a bottom-up effect by providing food and water resources to support increased prey and predators. To test these hypotheses, we compared natural herbaceous plant recruitment, herbivory and granivory rates, rodent abundance, and lagomorph and carnivore activity across an urbanization gradient in Las Cruces, NM. The gradient included four replicates each of three development levels: high density exurban (0.40 ha lots), low density exurban (1.20 ha lots), and wildland (undeveloped). We used seedling and foraging trays to measure herbivory and granivory rates, live-trapping to estimate rodent abundance, and wildlife cameras to measure lagomorph and carnivore activity.\  Results/Conclusions: Supporting both top-down and bottom-up hypotheses, we found increased rates of herbivory on seedlings and decreased herbaceous plant recruitment in the most dense exurban areas. Patterns of overall rodent (kangaroo rat and pocket mouse) abundance, seed consumption rates, and jackrabbit activity did not vary with urbanization. However, we found increased cottontail activity in dense exurban areas. We also found increased predator (coyote) activity in dense exurban areas compared to wildlands, supporting the hypothesis that the effect of urbanization on plant recruitment is mediated by a bottom-up effect. Our results indicate that urbanization can have important indirect effects on natural vegetation.\  COS 112-3.

}, author = {Kristen Davanon and Lindsey Howard and Brandon T Bestelmeyer and Karen Mabry and Robert L. Schooley} }