Research sites and sampling parameters.

1Michigan Gradient Study; http://www.webpages.uidaho.edu/nitrogen-gradient/default.htm.2FACTSII, Aspen-FACE; http://www.nrs.fs.fed.us/disturbance/climate_change/face/.3CarboEurope-IP field site; http://www.carboeurope.org/.4SOERE F-ORE-T experimental site; http://www.gip-ecofor.org/f-ore-t/breuil.php.5Biodiversity Exploratories; http://www.biodiversity-exploratories.de/.6Puéchabon experimental site; http://www2.cnrs.fr/sites/communique/fichier/fluxletterlight_1.pdf.7measured using substrate and peroxide, phenol oxidase activity without peroxide was subtracted.n.a. not available.