Enhanced root exudation induces microbial feedbacks to N cycling in a pine forest under long‐term CO 2 fumigation

The degree to which rising atmospheric CO(2) will be offset by carbon (C) sequestration in forests depends in part on the capacity of trees and soil microbes to make physiological adjustments that can alleviate resource limitation. Here, we show for the first time that mature trees exposed to CO(2) enrichment increase the release of soluble C from roots to soil, and that such increases are coupled to the accelerated turnover of nitrogen (N) pools in the rhizosphere. Over the course of 3 years, we measured in situ rates of root exudation from 420 intact loblolly pine (Pinus taeda L.) roots. Trees fumigated with elevated CO(2) (200 p.p.m.v. over background) increased exudation rates (μg C cm(-1) root h(-1) ) by…

• UD
  U.S. Department of Energy