Biology ETDs

Publication Date

Summer 7-28-2017

Abstract

Knowledge of how multiple global change drivers interact to affect community structure is critical for predicting future community states, especially when community structure drives ecosystem function. Disturbances such as fire and nutrient additions often shift communities away from their mean composition, but less is known about how disturbances affect spatial variation among local patches of the community over time (spatiotemporal dispersion). Dispersion may increase (local communities diverge in composition), stay the same, or decrease (communities converge) in response to disturbance. We compared patterns of spatiotemporal dispersion and temporal trajectories in community composition across three sites in a northern Chihuahuan Desert grassland with different disturbance histories: unburned, burned, or burned plus fertilized. To fertilize, nitrogen, phosphorus, and potassium were added in a fully factorial design following the protocol of Nutrient Network. Community change in all sites tracked inter-annual variation in yearly climate, but there was no directional, temporal trajectory in community composition following a natural fire in 2009. In contrast to patterns in mesic grasslands, fertilization had no effect on plant productivity or species richness. However, burned-fertilized sites had the highest community dispersion, while dispersion was lowest at the unburned-unfertilized site. Nitrogen additions alone and nitrogen plus phosphorus both increased community dispersion, thereby magnifying spatiotemporal heterogeneity in community composition across the landscape, relative to unfertilized conditions. Our results highlight the importance of examining spatiotemporal variation in community responses to multiple global change drivers, in addition to understanding shifts in mean community composition.

Language

English

Document Type

Thesis

Degree Name

Biology

Level of Degree

Masters

Department Name

UNM Biology Department

First Committee Member (Chair)

Scott Collins

Second Committee Member

Jennifer Rudgers

Third Committee Member

William Pockman

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