Natural and Anthropogenic Drivers of Calcium Depletion in a Northern Forest during the Last Millennium. Leys, B. A., Likens, G. E., Johnson, C. E., Craine, J. M., Lacroix, B., & McLauchlan, K. K. 113(25):6934–6938.
Natural and Anthropogenic Drivers of Calcium Depletion in a Northern Forest during the Last Millennium [link]Paper  doi  abstract   bibtex   
[Significance] This research breaks new ground by showing that, contrary to generally accepted theories of ecosystem development, calcium depletion has been occurring for millennia as a natural consequence of long-term ecosystem development. This natural process predisposed forest ecosystems in the region to detrimental responses to acid rain in the 20th century. We also show that nitrogen availability was increasing concurrently with the depletion of calcium. This is the first study, to our knowledge, to reconstruct continuous changes in nutrient availability for a northern forest ecosystem on the millennial time scale. The results alter our assessments of the speed and trajectory of nutrient limitation in forests and suggest that reformulation of global models of forest productivity may be necessary. [Abstract] The pace and degree of nutrient limitation are among the most critical uncertainties in predicting terrestrial ecosystem responses to global change. In the northeastern United States, forest growth has recently declined along with decreased soil calcium (Ca) availability, suggesting that acid rain has depleted soil Ca to the point where it may be a limiting nutrient. However, it is unknown whether the past 60 y of changes in Ca availability are strictly anthropogenic or partly a natural consequence of long-term ecosystem development. Here, we report a high-resolution millennial-scale record of Ca and 16 other elements from the sediments of Mirror Lake, a 15-ha lake in the White Mountains of New Hampshire surrounded by northern hardwood forest. We found that sedimentary Ca concentrations had been declining steadily for 900 y before regional Euro-American settlement. This Ca decline was not a result of serial episodic disturbances but instead the gradual weathering of soils and soil Ca availability. As Ca availability was declining, nitrogen availability concurrently was increasing. These data indicate that nutrient availability on base-poor, parent materials is sensitive to acidifying processes on millennial timescales. Forest harvesting and acid rain in the postsettlement period mobilized significant amounts of Ca from watershed soils, but these effects were exacerbated by the long-term pattern. Shifting nutrient limitation can potentially occur within 10,000 y of ecosystem development, which alters our assessments of the speed and trajectory of nutrient limitation in forests, and could require reformulation of global models of forest productivity.
@article{leysNaturalAnthropogenicDrivers2016,
  title = {Natural and Anthropogenic Drivers of Calcium Depletion in a Northern Forest during the Last Millennium},
  author = {Leys, Bérangère A. and Likens, Gene E. and Johnson, Chris E. and Craine, Joseph M. and Lacroix, Brice and McLauchlan, Kendra K.},
  date = {2016-06},
  journaltitle = {Proceedings of the National Academy of Sciences},
  volume = {113},
  pages = {6934--6938},
  issn = {1091-6490},
  doi = {10.1073/pnas.1604909113},
  url = {http://mfkp.org/INRMM/article/14073752},
  abstract = {[Significance]

This research breaks new ground by showing that, contrary to generally accepted theories of ecosystem development, calcium depletion has been occurring for millennia as a natural consequence of long-term ecosystem development. This natural process predisposed forest ecosystems in the region to detrimental responses to acid rain in the 20th century. We also show that nitrogen availability was increasing concurrently with the depletion of calcium. This is the first study, to our knowledge, to reconstruct continuous changes in nutrient availability for a northern forest ecosystem on the millennial time scale. The results alter our assessments of the speed and trajectory of nutrient limitation in forests and suggest that reformulation of global models of forest productivity may be necessary.

[Abstract]

The pace and degree of nutrient limitation are among the most critical uncertainties in predicting terrestrial ecosystem responses to global change. In the northeastern United States, forest growth has recently declined along with decreased soil calcium (Ca) availability, suggesting that acid rain has depleted soil Ca to the point where it may be a limiting nutrient. However, it is unknown whether the past 60 y of changes in Ca availability are strictly anthropogenic or partly a natural consequence of long-term ecosystem development. Here, we report a high-resolution millennial-scale record of Ca and 16 other elements from the sediments of Mirror Lake, a 15-ha lake in the White Mountains of New Hampshire surrounded by northern hardwood forest. We found that sedimentary Ca concentrations had been declining steadily for 900 y before regional Euro-American settlement. This Ca decline was not a result of serial episodic disturbances but instead the gradual weathering of soils and soil Ca availability. As Ca availability was declining, nitrogen availability concurrently was increasing. These data indicate that nutrient availability on base-poor, parent materials is sensitive to acidifying processes on millennial timescales. Forest harvesting and acid rain in the postsettlement period mobilized significant amounts of Ca from watershed soils, but these effects were exacerbated by the long-term pattern. Shifting nutrient limitation can potentially occur within 10,000 y of ecosystem development, which alters our assessments of the speed and trajectory of nutrient limitation in forests, and could require reformulation of global models of forest productivity.},
  keywords = {*imported-from-citeulike-INRMM,~INRMM-MiD:c-14073752,~to-add-doi-URL,anthropogenic-changes,calcium,ecology,ecosystem,forest-resources,historical-perspective,modelling,primary-productivity,temperate-forests,united-states,wood-production},
  number = {25}
}

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