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Effect of N fertilization on CO2, CH4, and N2O fluxes from a Larix gmelinii forest soil in a continuous permafrost region of central Siberia

Tomoaki Morishita1, Yojiro Matsuura2, Takuya Kajimoto2, Akira Osawa3, Olga Zyryanova4, Anatoly Prokushkin4
1 Shikoku Research Center, Forestry and Forest Products Research Institute
2 Forestry and Forest Products Research Institute
3 Kyoto University
4 V.N.Sukachev Institute

P 3.14 in Fluxes between the atmosphere and ecosystems

Poster Session 2 on Tuesday, 16:30-18:00

In boreal forest of Russia, it is predicted that N deposition from atmosphere will increase near future. N fertilization could change microbial activity in the soil, and greenhouse gas (CO2, CH4, and N2O) dynamics c ould change due to the changes of microbial activity. There are many studies of greenhouse gas dynamics in boreal forest those were conducted in North America and Europe on the discontinuous or absence of permafrost, but a few in continuous permafrost region of Russia. The purpose of this study is to clarify the effect of N fertilization on greenhouse gases flux in a Larix gmerinii forest (ca. 100 years old) in Central Siberia, Russia. The study site was located in Tura (64o 19’ N, 100o 13’ E), Central Siberia. The mean annual temperature and precipitation are –9.2 °C and 317 mm, respectively. The surface soil is frozen from mid-October to the beginning of May. Mosses and lichens covered 10 to 20 cm thick on the forest floor. Control (CP) and N fertilization plots (NP) (15 x 15m) were established in the forest in 2004. In summer season from 2004, granular forms of urea (total 60 kg N ha-1 yr-1 in each year) were applied by hand. Gas flux was measured by using a closed chamber technique. The mean soil temperature and moisture at NP (5.8±4.5 °C, 0.22±0.07 m3 m-3) was not different at CP (5.4±4.3 °C, 0.21±0.05 m3 m-3). The CO2 flux at NP (65±39 mg CO2-C m-2 h-1) was significantly higher than that at CP (47±28 mg CO2-C m-2 h-1) (P < 0.01) in all measurements. The urea fertilization would promote root or microbial respiration. CH4 tended to be taken up by soil (max., –7.3 ug CH4-C m-2 h-1), while N2O tended to be emitted from the soil (max., 2.2 ug N2O-N m-2 h-1). There was no significant difference in CH4 and N2O between CP and NP. CH4 uptake rate decreased with increase in soil moisture (P = 0.02). On the other hand, N2O emission rate decreased with soil moisture increasing (P =0.06), and high N2O emission rate was observed at NP in lower soil moisture condition. In various ecosystems, N fertilization such as NH4+ and urea decrease CH4 uptake and increase N2O emission from soils in relation to nitrification. In this site, the strong immobilization was observed possibly due to poor nutrient at NP. Therefore, there was no clear decrease in CH4 uptake and increase in N2O emission.

Letzte Änderung 02.04.2014