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Nitrogen deposition and forest nitrogen cycling along an urban–rural transect in southern China
Author(s) -
FANG YUNTING,
YOH MUNEOKI,
KOBA KEISUKE,
ZHU WEIXING,
TAKEBAYASHI YU,
XIAO YIHUA,
LEI CHUNYI,
MO JIANGMING,
ZHANG WEI,
LU XIANKAI
Publication year - 2011
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2010.02283.x
Subject(s) - throughfall , transect , cycling , environmental science , leaching (pedology) , soil acidification , subtropics , nitrification , nitrogen , deposition (geology) , soil ph , ecosystem , soil water , hydrology (agriculture) , agronomy , environmental chemistry , ecology , forestry , soil science , chemistry , geography , biology , geology , paleontology , geotechnical engineering , organic chemistry , sediment
Abstract There is increasing concern over the impact of atmospheric nitrogen (N) deposition on forest ecosystems in the tropical and subtropical areas. In this study, we quantified atmospheric N deposition and revealed current plant and soil N status in 14 forests along a 150 km urban to rural transect in southern China, with an emphasis on examining whether foliar δ 15 N can be used as an indicator of N saturation. Bulk deposition ranged from 16.2 to 38.2 kg N ha −1 yr −1 , while the throughfall covered a larger range of 11.7–65.1 kg N ha −1 yr −1 . Foliar N concentration, NO 3 − leaching to stream, and soil NO 3 − concentration were low and NO 3 − production was negligible in some rural forests, indicating that primary production in these forests may be limited by N supply. But all these N variables were enhanced in suburban and urban forests. Across the study transect, throughfall N input was correlated positively with soil nitrification and NO 3 − leaching to stream, and negatively with pH values in soil and stream water. Foliar δ 15 N was between −6.6‰ and 0.7‰, and was negatively correlated with soil NO 3 − concentration and NO 3 − leaching to stream across the entire transect, demonstrating that an increased N supply does not necessarily increase forest δ 15 N values. We proposed several potential mechanism that could contribute to the δ 15 N pattern, including (1) increased plant uptake of 15 N‐depleted soil NO 3 − , (2) foliage uptake of 15 N‐depleted NH 4 + , (3) increased utilization of soil inorganic N relative to dissolved organic N, and (4) increased fractionation during plant N uptake under higher soil N availability.