Decomposition and nitrogen mineralization in five common urban habitat types across seven college campuses in Southern California (January-May 2019)

Urban landscaping conversions can alter decomposition processes and soil respiration, making it difficult to forecast regional CO2 emissions. Here we explore rates of initial mass loss and net nitrogen (N) mineralization in natural and four common urban landcovers (water -wise, water-wise with mulch, shrub, and lawn) from sites across seven Colleges in southern California. To better understand decomposition processes in surface soils across various urban habitats, we measured rates of leaf litter decomposition and nitrogen (N) mineralization between 28 January and 17 May 2019, for two dominant native trees of the southern California region: coastal live oak (Quercus agrifolia Neé, “oak”) and western sycamore (Platanus racemosa L., “sycamore”) in natural and urbanized land-covers at seven college campuses in southern California. At each college, we placed litter bags in five landcover types that typify southern California urban landscapes: (1) lawns, dominated by non-native grasses and high water inputs; (2) hedge/shrub environments, defined by at least 75% cover of non-native shrubs with water inputs; (3) water-wise gardens (no mulch), which consist of native or non-native plants with reduced water inputs but no mulch; (4) water-wise (with mulch) gardens, with native or non-native plants, reduced water inputs and a mulch (most often mixed wood chips) covered soil; and (5) natural areas, receiving no water subsidies often dominated by native shrubs or non-native annuals.