Biotic and Abiotic Drivers of Decomposition Rates in Urban Soils: A Proof of Concept for a Global Experimental Network.

Urban soils provide many of the same ecosystem services as “natural” or agricultural soils e.g. decomposition and nutrient cycling, water purification and regulation, medium for plant growth, and habitat for an enormous diversity of organisms. Soil biota and substrate quality, along with abiotic factors, such as climate and parent material, greatly influences decomposition rates. In the highly fragmented urban landscape, land history, cover and management will strongly influence and in some cases may override these drivers. This leads to a high degree of similarity in biogeochemical processes among cities, a phenomenon known as Urban Convergence Hypothesis.

We have developed a series of relatively simple experimental protocols to assess soil characteristics, soil biota and decomposition rates across urban landscapes at a global scale.  We will present preliminary results from a proof of concept study conducted in five cities: Baltimore, MD (USA), Budapest (Hungary), Helsinki (Finland), Lahti (Finland), and Potchefstroom (South Africa). In each city four habitat types (reference site reflecting natural vegetation cover outside the city, remnant patches of the reference cover within the city, low maintenance lawn, and highly disturbed soil) were chosen in five replicates. To keep substrate constant we used teabags (Lipton pyramid red tea) as “litter bags” to measure decomposition. Soils were sampled to measure bacterial and fungal abundance and basic soil characteristics. Our ultimate goal is to establish a global experimental network that compares soil community composition and soil processes across different climatic zones, urban development patterns, socio-economic factors, soil types, and urban environmental factors.