Controls over N<sub>2</sub>O, NO<sub>x</sub> and CO<sub>2</sub> fluxes in a calcareous mountain forest soil

Abstract

Abstract. We measured nitrogen oxides (N2O and NOx), dinitrogen (N2) and carbon dioxide (CO2) emissions from a spruce-fir-beech forest soil in the North Tyrolean limestone Alps in Austria. The site received 12.1 kg nitrogen via wet and dry deposition. Fluxes of nitric oxide (NO) were measured by an automatic dynamic chamber system on an hourly basis over a two year period. Daily N2O emissions were obtained by a semi-automatic gas measuring system. In order to cover spatial variability biweekly manual measurements of N2O and CO2 emissions were carried out, additionally. For acquiring information on the effects of soil and meteorological conditions and of N-deposition on N-emissions we chose the autoregression procedure (time-series analysis) as our means of investigation. Hence, we could exclude the data's autocorrelation in the course of the time. We found that soil temperature, soil moisture and wet N-deposition followed by air temperature and precipitation were the most powerful influencing parameters effecting N-emissions. With these variables up to 89% of observed temporal variations of N-emissions could be explained. During the two-year investigation period between 2.5 and 3.5% of deposited N was reemitted in form of N2O whereas only 0.2% were emitted as NO. At our mountain forest site the main end-product of microbial activity processes was N2 and trace gases (N2O and NO) were only of minor importance.

Methodical study of nitrous oxide eddy covariance measurements using quantum cascade laser spectrometery over a Swiss forest

“…This was not expected and should receive more attention in future studies. Furthermore, there is a need to increase our understanding of N 2 O uptake reported in many studies (Pihlatie et al, 2005b, Leahy and Kiely, 2006, Kitzler et al, 2006, Neftel et al, 2007 which is also evident in our data (Table 2) in order not to overestimate the greenhouse forcing effect of N 2 O fluxes from natural ecosystems.…”

“…Their chamber fluxes are roughly a factor two larger than their eddy covariance fluxes. Kitzler et al (2006) measured bi-weekly during two years with manual chambers in a similar forest with comparable nitrogen deposition rates (see Burkard et al, 2003 for conditions at our site) and yielded mean N 2 O fluxes of 0.31±0.02 µmol m −2 h −1 . Although vegetation, soil type and calcareous ground are very comparable to the Lägeren site, their measurements were at a higher elevation where trees are less tall and annual temperature is 1.7 • C colder (6.5 vs. 8.2 • C) which may already be responsible for the differences in fluxes.…”

Soil pH was the main controlling factor of the denitrification rates and N2/N2O emission ratios in forest and grassland soils along the Northeast China Transect (NECT)

“…Wolf and Brumme (2003) recorded N 2 /N 2 O emission ratios of 1.0 for an acidic mineral soil (pH ¼ 3.8) and 1.25 for a less acidic mineral soil (pH ¼ 5.2) in watersaturated conditions, using a 15 N tracer technique. Kitzler et al (2006) obtained an N 2 /N 2 O emission ratio of 6, measured using the acetylene inhibition technique, for a shallow calcareous mountain forest soil (pH ¼ 6.4). Wolf and Brumme (2003) Dannenmann et al (2008) reported high N 2 /N 2 O emission ratios (ranging from 21 to 220) for intact soil cores taken from a mountainous beech forest ecosystem (pH > 6) and suggested that the low value for the N 2 /N 2 O emission ratio (e.g., in Kitzler et al 2006) may have been due to artefacts of the applied acetylene inhibition technique.…”

“…Kitzler et al (2006) obtained an N 2 /N 2 O emission ratio of 6, measured using the acetylene inhibition technique, for a shallow calcareous mountain forest soil (pH ¼ 6.4). Wolf and Brumme (2003) Dannenmann et al (2008) reported high N 2 /N 2 O emission ratios (ranging from 21 to 220) for intact soil cores taken from a mountainous beech forest ecosystem (pH > 6) and suggested that the low value for the N 2 /N 2 O emission ratio (e.g., in Kitzler et al 2006) may have been due to artefacts of the applied acetylene inhibition technique. Notwithstanding that the methods used in previous investigations could affect the absolute value of the N 2 / N 2 O ratio, the effects of soil pH on this ratio were confirmed here.…”

The carbon and nitrogen biogeochemistry of a montane Norway spruce (Picea abies (L.) Karst.) forest: a synthesis of long-term research

“…The early build-up of a continuous snow cover ensures that the soil is well insulated and remains unfrozen in most years. Although the soils are rather cool and moist, soil biological activity is high (Härtel et al 2002;Kitzler et al 2006; Diaz-Pines Lopez de los . Root density is highest in the O-and A-horizons, and few roots are found as deep as 60 cm.…”