Nitrogen and phosphorus addition impact soil N2O emission in a secondary tropical forest of South China

Abstract

Nutrient availability greatly regulates ecosystem processes and functions of tropical forests. However, few studies have explored impacts of N addition (aN), P addition (aP) and N×P interaction on tropical forests N2O fluxes. We established an N and P addition experiment in a tropical forest to test whether: (1) N addition would increase N2O emission and nitrification, and (2) P addition would increase N2O emission and N transformations. Nitrogen and P addition had no effect on N mineralization and nitrification. Soil microbial biomass was increased following P addition in wet seasons. aN increased 39% N2O emission as compared to control (43.3 μgN2O-N m−2h−1). aP did not increase N2O emission. Overall, N2O emission was 60% greater for aNP relative to the control, but significant difference was observed only in wet seasons, when N2O emission was 78% greater for aNP relative to the control. Our results suggested that increasing N deposition will enhance soil N2O emission, and there would be N×P interaction on N2O emission in wet seasons. Given elevated N deposition in future, P addition in this tropical soil will stimulate soil microbial activities in wet seasons, which will further enhance soil N2O emission.

Nitrous oxide fluxes and dissolved N gases (N2 and N2O) within riparian zones along the agriculturally impacted San Joaquin River

“…In addition, the N 2 O-N:N 2 -N ratio was an order of magnitude higher (range 0.01-0.03) than any other groundwater sampled. These results support many previous studies that have shown high concentrations of NO 3 -contribute to higher concentrations of N 2 O (Weier et al 1993;Skiba et al 1998;Wang et al 2014).…”

Phosphorus addition enhances loss of nitrogen in a phosphorus-poor soil

“…Different letters above bars indicate significant differences among the P addition and N addition treatments (P < 0.05, Tukey's HSD test). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 limited by P. Phosphorus addition increased nitrification, denitrification and gaseous N emissions in upland (Mori et al, 2010;Fisk et al, 2014;Wang et al, 2014;Zhang et al, 2014) and wetland soils (White and Reddy, 2003). Microbes in general have a high P requirement, mostly for synthesis of RNA that can contribute 70e90% of total microbial P, which increases with increased microbial activity (Makino and Cotner, 2004;Franklin et al, 2011).…”

Nutrient addition effects on tropical dry forests: a mini-review from microbial to ecosystem scales

“…A fertilization study in a TDF in India showed that N pools and mineralization rates increased with added N (Verma et al, 2013); however, both nitrogen cycling (Saynes et al, 2005) and nutrient addition effects on N cycling in another TDF in Mexico depended on season and forest successional status (Solís and Campo, 2004). Last, nitric and nitrous oxide emissions should increase under N deposition, particularly during the wet season (Erickson et al, 2002;Wang et al, 2014), and especially from N-saturated or P-limited forests (Hall and Matson, 1999).…”