『Abstract
Understanding forest carbon cycling responses to atmospheric
N deposition is critical to evaluating ecosystem N dynamics. The
natural abundance of 15N (δ15N) has been
suggested as an efficient and non-invasive tool to monitor N pools
and fluxes. In this study, three successional forests in southern
China were treated with four levels of N addition. In each treatment,
we measured rates of soil N mineralization, nitrification, N2O emission and inorganic N leaching as well as
n concentration and δ15N (p＜0.05). Also, N addition
decreased the δ15N of top soil in the N-poor pine and
mixed forests and significantly increased that of organic and
mineral soils in N-rich broadleaf forests (p＜0.05). In addition,
the soil N2O emission flux and inorganic
N leaching rate increased with increasing N addition and were
positively correlated with increasing N addition and were positively
correlated with the 15N enrichment factor (εp/s)
of forest ecosystems. Our study indicates that δ15N
of leaf, litter and soil integrates various information on plant
species, forest stand age, exogenous N input and soil N transformation
and loss, which can be used to monitor N availability and N dynamics
in forest ecosystems caused by increasing N deposition in the
future.
Keywords: N transformation; N loss; 15N natural abundance
successional stages; N addition; Subtropical China』
Introduction
Materials and methods
Site descriptions
Experimental design
Sampling and analysis
Soil N transformation and loss
Statistical analysis
Results
Foliar N concentration and δ15N
Soil N concentration and δ15N
Soil N transformation and loss
Relationship between the 15N enrichment factor and
N cycling rates
Discussion
Effects of N addition on N cycling
Effects of plant species and forest succession on foliar δ15N
Effects of applied N fertilizer on the δ15N of foliage
and top soil
N isotope fractionation simulating by N addition
Conclusions
Acknowledgements
References