Homogeneity of δ15N in needles of Masson pine (Pinus massoniana L.) was altered by air pollution

The present study investigated the changes of delta N-15 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 N-15 in the three sections of both current- and previous-year needles were found evenly distributed, while at the polluted stands, delta N-15 values in the needles were revealed significantly different from the tip to the base sections. The results implied that the distribution of delta N-15 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 N-15 values among pine needle sections should be reconsidered and should not be primarily ignored when the needle delta N-15 values were used to assess plant responses to air pollution. (C) 2009 Elsevier Ltd. All rights reserved.