Plant element stoichiometry and stoichiometric flexibility strongly regulate ecosystem responses to global change. Here, we tested three potential mechanistic drivers (climate, soil nutrients, and plant taxonomy) of both using paired foliar and soil nutrient data from terrestrial forested National Ecological Observatory Network sites across the USA. We found that broad patterns of foliar nitrogen (N) and foliar phosphorus (P) are explained by different mechanisms.
View Article and Find Full Text PDFPlant root associations with microbes such as mycorrhizal fungi or N-fixing bacteria enable ecosystems to tap pools of nitrogen (N) that might otherwise be inaccessible, including atmospheric N or N in large soil organic molecules. Such microbially assisted N-foraging strategies may be particularly important in late-successional retrogressive ecosystems where productivity is low and soil nutrients are scarce. Here, we use natural N-stable isotopic composition to constrain pathways of N supplies to different plant functional groups across a well-studied natural soil fertility gradient that includes a highly retrogressive stage.
View Article and Find Full Text PDFGlobal ecosystem models suggest that bedrock nitrogen (N) weathering contributes 10-20% of total N inputs to the natural terrestrial biosphere and >38% of ecosystem N supplies in temperate forests specifically. Yet, the role of rock N weathering in shaping ecological processes and biogeochemical fluxes is largely unknown. Here, we show that temperate forest ecosystems underlain by N-rich bedrock exhibit higher free-living N fixation rates than similar forests residing on N-poor parent materials, across sites experiencing a range of climate and tectonic regimes.
View Article and Find Full Text PDFNitrogen (N) fixation by free-living bacteria is a primary N input pathway in many ecosystems and sustains global plant productivity. Uncertainty exists over the importance of N, phosphorus (P) and molybdenum (Mo) availability in controlling free-living N fixation rates. Here, we investigate the geographic occurrence and variability of nutrient constraints to free-living N fixation in the terrestrial biosphere.
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