How will global warming affect decomposition and element cycling of native and invasive leaf litter in streams?

Ayala Crespo, Carla Nicole (2023) How will global warming affect decomposition and element cycling of native and invasive leaf litter in streams? Masters thesis, Northern Arizona University.

Text Ayala_Crespo_2023_how_will_global_warming_affect_decomposition_element.pdf - Published Version Restricted to Repository staff only Download (2MB) | Request a copy

Abstract

Global warming and introduced species have the potential to alter the functioning and structure of headwater streams. Testing how temperature affects detrital food webs is challenging because it is difficult to manipulate temperature in a field setting. Here, we evaluate how microbes and shredders decompose two morphologically distinct, riparian tree species, Populus fremontii (native) and Tamarix sp. (nonnative). We built an artificial stream facility to manipulate temperature while maintaining natural diurnal and seasonal patterns of most stream variables (light, nutrients, dissolved oxygen). We employed a factorial design that included 3 temperature treatments (ambient, + 3.7°C, and + 6.6°C), 2 leaf types and 2 decomposition mediators (microbes and shredders + microbes). Decomposition rate and microbial biomass were influenced by leaf type and temperature, with P. fremontii decomposing more rapidly and supporting almost twice the microbial biomass found in Tamarix sp. Temperature increased decomposition rate by 9.1 to 16.5% in the +3.7°C treatments relative to ambient temperatures. Additional increases in temperature did not accelerate decomposition rate for either species. Litter packs containing shredders decomposed more rapidly than litter packs with only microbes. However, shredder contribution to leaf litter decomposition was relatively low in both leaf types, ranging from 1.97% to 10.45%. A laboratory experiment measured leaching rates with 2 temperatures and 2 time periods (24h and 48h). P. fremontii leached significantly more DOC than Tamarix sp. and Tamarix sp. leached significantly more TN than P. fremontii. In both litter types, approximately 43% to 48% of initial mass was lost after 48 hours of leaching. Temperature did not affect mass loss due to leaching. These results show that increases in water temperature may lead to rapid depletion of labile leaf litter resources and that the disproportionately high leaching of TN found in Tamarix sp. leaf litter may prevent microbes and shredders from accessing compounds containing nitrogen.

Item Type:	Thesis (Masters)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	Carbon cycling; Global warming; Invasive species; Leaf litter decomposition; Streams
Subjects:	Q Science > QK Botany
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > Biological Sciences
Date Deposited:	01 Aug 2023 21:44
Last Modified:	01 Aug 2023 21:44
URI:	https://openknowledge.nau.edu/id/eprint/6081

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