Abstract
Soil is a significant source of atmospheric N2O, and soil N2O emissions at a global scale are greatly affected by environment changes that include continuous deposition of atmospheric nitrogen and changing precipitation distribution. However, to date, field simulations of multiple factors that control the interaction between nitrogen deposition and precipitation on forest soil N2O emissions are scarce. In this study, we conducted a 2-year continuous assessment of N2O emissions from November 2012 to October 2014 at a nitrogen addition and rainfall reduction manipulation platform in an old broad-leaved Korean pine mixed forest at Changbai Mountain in northeastern China. We found that N2O emissions from control plots were 1.25 ± 0.22 kg N2O-N ha−1 a−1. Nitrogen addition significantly increased N2O emissions, with the emission factor of 1.59%. A 30% reduction in rainfall decreased N2O emissions by 17–45%. However, in combination, nitrogen addition and rainfall reduction increased N2O emissions by 58–140%, with the emission factor of 3.19%, and had a larger promotional effect than the addition of nitrogen alone. Our results indicated that drought slightly decreases forest soil N2O emission; however, with increasing deposition of atmospheric N in temperate forest soils, the effect of drought might become altered to increase N2O emission.
Highlights
N2O emission rates from three replicates in NF (B), FF (C), RR (D) and rainfall-reduction and N-fertilization (RRF) (E) treatments measured from November 2012 to October 2014 are shown by the black circles
The mean annual N2O emission from NF plots was 1.25 ± 0.22 kg N2O-N ha−1 a−1, which is consistent with data reported in previous studies on N2O emissions for temperate forest soils[12,23,24,25]
The response of soil N2O emissions to nitrogen addition and rainfall reduction was studied for two continuous years in an old broad-leaved Korean pine mixed forest at Changbai Mountain in northeastern China
Summary
N2O emission rates from three replicates in NF (B), FF (C), RR (D) and RRF (E) treatments measured from November 2012 to October 2014 are shown by the black circles. Broad-leaved Korean pine (Pinus koraiensis) mixed forest covers an area of 42 334 ha in the Changbai Mountain region and is one of the dominant forest types in northeastern China. This area is exposed to high nitrogen deposition of at least 23 kg N ha−1 a−1 20 and receives less precipitation in the summer and fall[21]. To examine the influence of an increase in nitrogen deposition, a decrease in precipitation and the effect of annual variability in temperature and precipitation on soil N2O emissions, both nitrogen addition and rainfall reduction were experimentally manipulated at this site. We hypothesized that rainfall reduction would amplify the stimulatory effect of nitrogen addition on N2O emissions, for less leaching losses of nitrogen[22]
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