The increased water-soluble organic carbon and microbial biomass carbon explained the increased CH4 uptake under high P addition.
High-dose P addition significantly increased the soil CH4 uptake by 15.80% and 16.23% under the HP and HNHP treatments, respectively, while N addition alone and low P addition (LP and HNLP) did not significantly affect CH4 uptake as compared with the control. N and P interactive additions slightly (not significant) stimulated the N2O emissions as compared with that under the N addition alone treatment. The SEM analysis indicated that increased N2O emissions under N addition were primarily explained by the increase in available N and contributed more to the stimulated NH4+-N contents. P addition alone (LP and HP) did not significantly affect the soil N2O emissions as compared with the control. The results indicated that N addition alone (HN) significantly (p < 0.05) increased the soil N2O emissions by 30.15% and 80.47% over annual and 4-month periods, mainly owing to the elevated NH4+-N content. Here, we conducted experiments with N (high N addition: 15 g N/m2, HN), P (low: 5 g P/m2, LP high: 15 g P/m2, HP) and their interactive (HNLP and HNHP) treatments to investigate how N and P additions affected CH4 and N2O exchanges in an N-rich Chinese fir plantation (Cunninghamia lanceolata), and further explored the underlying mechanisms through the structural equation model (SEM) analysis. Extra N additions were reported to cause nutrient imbalance and phosphorus (P) limitation in many tropical and subtropical forests, and further result in changes in soil nitrous oxide (N2O) and methane (CH4) fluxes. Increased nitrogen (N) inputs in subtropical forest ecosystems were widely reported.
Although P fertilization may alleviate the stimulated effects of atmospheric N deposition on N2O emission in N-rich forests, this effect may only occur under high N deposition and/or long-term P addition, and we suggest future investigations to definitively assess this management strategy and the importance of P in regulating N cycles from regional to global scales. However, both P and NP addition had no significant effect on N2O emission in all three forests, suggesting that P addition alleviated the stimulation of N2O emission by N addition in the old-growth forest. N addition significantly increased N2O emission in the old-growth forest but not in the two younger forests.
Mean N2O emission was shown to be significantly higher in the old-growth forest (13.9 ± 0.7 µg N2O-N m−2 h−1) than in the mixed (9.9 ± 0.4 µg N2O-N m−2 h−1) or pine (10.8 ± 0.5 µg N2O-N m−2 h−1) forests, with no significant difference between the latter two. From February 2007 to October 2009, monthly quantification of soil N2O emission was performed using static chamber and gas chromatography techniques.
Trebs treats binghamton ny plus#
The following four treatments were established in each forest: Control, N addition (150 kg N ha−1 yr−1), P addition (150 kg P ha−1 yr−1), and NP addition (150 kg N ha−1 yr−1 plus 150 kg P ha−1 yr−1). In this study, we examined the effects of N and P additions on soil N2O emission in an N-rich old-growth forest and two N-limited younger forests (a mixed and a pine forest) in southern China to test the following hypotheses: (1) soil N2O emission is the highest in old-growth forest due to the N-rich soil (2) N addition increases N2O emission more in the old-growth forest than in the two younger forests (3) P addition decreases N2O emission more in the old-growth forest than in the two younger forests and (4) P addition alleviates the stimulation of N2O emission by N addition. In many tropical forests, however, elevated N deposition has caused soil N enrichment and further phosphorus (P) deficiency, and the interaction of N and P to control soil N2O emission remains poorly understood, particularly in forests with different soil N status. Nitrogen (N) deposition is generally considered to increase soil nitrous oxide (N2O) emission in N-rich forests.
0 kommentar(er)
