Humans alter and manage landscapes to varying degrees to suit our needs and preferences. Decomposition of organic matter is essential replenish soil nutrients for the functioning of healthy ecosystems in both natural and human-modified landscapes. While a variety of microorganisms, fungi, and insects affect decomposition processes, rates vary depending on the substrate and soil characteristics, such as temperature and moisture availability. Decomposition processes in agricultural and natural settings have been extensively studied but remain relatively unexplored in urban settings, especially in relation to stormwater natural treatment systems. We studied decomposition and litter stabilization rates across four land-use types (e.g., biofilters/bioswales, ornamental landscapes, lawns, and unmanaged coastal sage scrub areas) on three southern University of California campuses. Three to four replicates of a standardized substrate were buried for approximately 85 days at each of 28 sites (i.e., seven sets of each land-use type). This study was run during both the dry and wet season. We used a Kruskal-Wallis test to understand differences in rates across land-use types followed by a pairwise comparison using the Wilcoxon rank sum test. Results suggests no significant differences in decomposition rates among managed land-use types irrespective of a varied irrigation schedules and season. Decomposition and litter stabilization rates did differ between managed and unmanaged land-use types. This study shows that within Mediterranean climates, management towards desired greener urban land use types changes the microclimate leading to increased decomposition rates and decreased litter stabilization. This change indicates a shift in the historic regional carbon cycle, which in turn has flow-on effects across the ecosystem from food-web composition and plant regeneration to perturbation of other natural cycles and greenhouse gas emissions.

Classic urban land management hastens decomposition in Southern California

2019 Fall National Meeting

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