Global climate change is expected to affect terrestrial ecosystems in a variety of ways. Some of the more well-studied effects include the biogeochemical feedbacks to the climate system that can either increase or decrease the atmospheric load of greenhouse gases such as carbon dioxide and nitrous oxide. Less well-studied are the effects of climate change on the linkages between soil and plant processes. Here, we report the effects of soil warming on these linkages observed in a large field manipulation of a deciduous forest in southern New England, USA, where soil was continuously warmed 5°C above ambient for 7 years. Over this period, we have observed significant changes to the nitrogen cycle that have the potential to affect tree species composition in the long term. Since the start of the experiment, we have documented a 45% average annual increase in net nitrogen mineralization and a three-fold increase in nitrification such that in years 5 through 7, 25% of the nitrogen mineralized is then nitrified. The warming-induced increase of available nitrogen resulted in increases in the foliar nitrogen content and the relative growth rate of trees in the warmed area. Acer rubrum (red maple) trees have responded the most after 7 years of warming, with the greatest increases in both foliar nitrogen content and relative growth rates. Our study suggests that considering species-specific responses to increases in nitrogen availability and changes in nitrogen form is important in predicting future forest composition and feedbacks to the climate system.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-011-2133-7) contains supplementary material, which is available to authorized users.

s m i t h s o n i a n c o n t r i b u t i o n s t o b o t a n y • n u m b e r 1 0 5 Smithsonian Institution Scholarly Press Smithsonian Institution Scholarly PressThe Mesophotic, Coral Reef-Associated, Marine Algal Flora of Puerto Rico, Caribbean Sea David L. Ballantine, Hector Ruiz Torres, and Nilda E. Aponte SERIES PUBLICATIONS OF THE SMITHSONIAN INSTITUTIONEmphasis upon publication as a means of "diffusing knowledge" was expressed by the first Secretary of the Smithsonian. In his formal plan for the Institution, Joseph Henry outlined a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge." This theme of basic research has been adhered to through the years by thousands of titles issued in series publications under the Smithsonian imprint, commencing with Smithsonian Contributions to Knowledge in 1848 and continuing with the following active series: s m i t h s o n i a n c o n t r i b u t i o n s t o b o t a n y • n u m b e r 1 0 5The Cover images, from left to right: Edge of insular shelf, offshore from La Parguera; technical divers' descent to the mesophotic; bottom habit, edge of insular shelf, "Weinberg," offshore from La Parguera. Published by SMITHSONIAN INSTITUTION SCHOLARLY PRESS

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