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Thesis Abstract – Riley (2018)

Title:

Comparing Soil Respiration in California Sage Scrub and Non-Native Grassland Habitats

Author and college:

Amanda Riley, Scripps College

Date:

December 2018

Degree:

Bachelor of Arts in Environmental Science

Advisors:

Colin Robins, Keck Science Department of Claremont McKenna, Pitzer, and Scripps Colleges
Wallace Meyer, Biology Department, Pomona College

Abstract:

Soil respiration (R_s) is a major component of the global carbon cycle and therefore important to accurately quantify and parametrize in nutrient cycling models. Controls on R_s in semi-arid environments differ from controls in wetter environments, yet semi-arid R_s dynamics are relatively under-studied. This study establishes baseline R_s rates in a California Sage Scrub (CSS), a non-native grassland (NNG), and an intermediate vegetation community during the summer dry season in southern California. Average R_s rates differed between habitats and were all below 1.0 μmol CO₂m^-2 s^-1. R_s rates were highest in CSS, followed by the intermediate habitat and then the NNG. To identify drivers of R_s, soil temperature, soil moisture, soil organic matter (SOM), total soil C, and total soil N were also measured, though none of these variables had a significant relationship with R_s. However, R_s did respond to manipulations of soil moisture in irrigation experiments, suggesting moisture is the limiting factor on R_s during the dry season. Though ultraviolet (UV) radiation plays a prominent role in the decomposition processes in CSS communities, manipulations of soils UV exposure did not detectably impact R_s. To complete baseline assessments, data collection during and immediately following the CSS wet winter season is needed.

For more information:

Contact Colin Robins – crobins@kecksci.claremont.edu