Biology ETDs

Publication Date

Summer 6-30-2020

Abstract

Uncertainties surround the extent to which diversity can mitigate the effects of climate change and anthropogenic activity on ecosystem functions. In desert grasslands, changes to water availability and soil nitrogen, two primary resources that limit ecosystem processes, can have lasting impacts on nutrient cycling. We used grass litter from Bouteloua eriopoda, Bouteloua gracilis, Pleuraphis jamesii, and Sporobolus spp. to assess the effects of soil resources on single- and multi-species decomposition in a Chihuahuan Desert grassland in central New Mexico, USA. Litterbags were deployed in a factorial experiment that manipulated rain pulse size (5- vs. 20-mm) and frequency (weekly vs. monthly), and soil nitrogen content during the monsoon season. Decay did not significantly differ among pulse-sized thresholds. We found significant differences among species so that the more palatable grasses, B. gracilis and P. jamesii, decayed faster (k = 0.48 y-1 and 0.33 y-1, respectively) than B. eriopoda (k = 0.24 y-1). Although not significant, the decay of litter mixtures was enhanced in the 5-mm·week-1 (k = 0.53 y-1) and 20-mm·month-1 (k = 0.499 y-1) treatment relative to the water control (k = 0.31 y-1) when nitrogen was not limiting. Nitrogen immobilization persisted only in B. eriopoda and litter mixtures after one year. Future changes in rainfall regimes will have limited impacts on nutrient cycling in desert grasslands at current rates of atmospheric nitrogen deposition. However, high rates of nitrogen deposition will likely intensify the effect of pulse-sized thresholds on nutrient cycling. We conclude that species composition is critical for ecosystem functioning.

Project Sponsors

Sevilleta Long Term Ecological Research

Language

English

Keywords

Sevilleta, Deep Well, mixed grassland, pulse-sized thresholds, litter mixtures, species traits

Document Type

Thesis

Degree Name

Biology

Level of Degree

Masters

Department Name

UNM Biology Department

First Committee Member (Chair)

Scott L. Collins

Second Committee Member

Marcy Litvak

Third Committee Member

Heather Throop

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