Coupled Biogeochemical Cycles in Human Ecosystems: Stoichiometry, Hydrology, Connectiveness, and Culture

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Brezonik0322065This proposal seeks to expand our understanding of biogeochemical cycles in human ecosystems. Our main question is: how do humans in cities and on farms alter biogeochemical cycles? We will address this question using a fourfold concept of coupling: (i) between hydrology and element cycling, (ii) among elements (stoichiometry), (iii) across spatial scales (from households to regions), and (iv) between human behavior and element cycling. Element cycles are controlled by spatial connections at three key scales. Elements move between households (which are key components of urban landscapes) and their surroundings, within and between watersheds (i.e., hierarchically from small upstream (low-order) watersheds downstream to larger, higher-order ones), and between major ecosystem types (e.g., from farm to city). Some of this movement is deliberately controlled (e.g., food import to cities), but a large portion is not (e.g., movement of NOx from autos and landscapes to the atmosphere. Moreover, there are "hotspots" within landscapes where disproportionate nutrient inputs, transformations, and losses occur. The complexity of human-dominated ecosystems is one reason why our understanding of their biogeochemical cycles has lagged behind that of natural systems. Nevertheless, for two reasons, now is the time to confront this complexity and develop this understanding. First, we must, as a matter of survival. Second, we can; our ability to acquire, store, and use data has reached the point that we can expect to unravel this complexity to a useful degree and develop new management paradigms.