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Shifts in an ecosystem’s state can alter biogeochemical cycling and the extent of nutrient conservation within a terrestrial landscape on multiple time scales. Transient biogeochemical changes may follow disturbance and succession, although persistent long-term differences may exist under different climates and vegetation types. We evaluate the potential for such biogeochemical changes in the context of long-term ecological history by measuring the nitrogen isotope composition of organic matter in a lake sediment core. We targeted Little Windy Hill Pond (LWH) in the Medicine Bow Mountains, Wyoming because reconstructions of the lake level, fire, and vegetation histories from the lacustrine sediments indicated a century-scale transformation from an arid, shrub-dominated landscape to a sub-alpine, tree-dominated ecosystem with extensive woody cover and large, live biomass pools. We demonstrate …