Authors: Michelle M Turner Hugh A L Henry
Publish Date: 2009/08/19
Volume: 162, Issue: 1, Pages: 227-236
Abstract
While climate warming can increase plant N availability over the growing season by increasing rates of N mineralization increased N mineralization over winter at a time when plant roots are largely inactive coupled with an increased frequency of soil freeze–thaw cycles may increase soil N leaching losses We examined changes in soil net N mineralization and N leaching in response to warming and N addition 6 g m−2 year−1 in a factorial experiment conducted in a temperate old field We used two warming treatments yearround and winteronly warming to isolate the effects of winter warming on soil N dynamics from the yearround warming effects We estimated net N mineralization using in situ soil cores with resin bags placed at the bottom to catch throughput and we measured N leaching using lysimeters located below the plant rooting zone at a depth of 50 cm There were minor effects of warming on changes in soil extractable N and resin N in the soil cores over winter Nevertheless the overall effects of both warming and N addition on net N mineralization the sum of changes in soil extractable N and resin N were not significant over this period Likewise there were no significant treatment effects on the concentration of N in leachate collected below the plant rooting zone However in response to winter warming net N mineralization over summer was approximately double that of both the ambient and yearround warming treatments This result demonstrates a potentially large and unexpected effect of winter warming on soil N availability in this old field systemThe infrastructure for this experiment was funded by the Canadian Foundation for Innovation and the Ontario Research Fund This work was also supported by a Natural Sciences and Engineering Research Council of Canada Discovery Grant to H A L H We thank Gena Braun for assistance in installing the infrastructure PA Niklaus and two anonymous reviewers provided helpful comments on an earlier version of the manuscript All experiments comply with the current laws of Canada where they were performed
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