Homogeneity of delta(15)N in needles of Masson pine (Pinus massoniana L.) was altered by air pollution.

The present study investigated the changes of delta(15)N values in the tip, middle and base section (divided by the proportion to needle length) of current- and previous-year needles of Masson pine (Pinus massoniana L.) from two declining forest stands suffering from air pollution, in comparison with one healthy stand. At the healthy stand, delta(15)N in the three sections of both current- and previous-year needles were found evenly distributed, while at the polluted stands, delta(15)N values in the needles were revealed significantly different from the tip to the base sections. The results implied that the distribution of delta(15)N among different parts or sections in foliages was not always homogeneous and could be affected by air pollution. We suggested that the difference of delta(15)N values among pine needle sections should be reconsidered and should not be primarily ignored when the needle delta(15)N values were used to assess plant responses to air pollution. Copyright 2009 Elsevier Ltd. All rights reserved.