The Implication of Climate Change on Forest Research

Plant and Soil

, Volume 168, Issue 1, pp 593-600

Mechanisms of carbon and nutrient release and retention in beech forest gaps

III. Environmental regulation of soil respiration and nitrous oxide emissions along a microclimatic gradient
  • Rainer BrummeAffiliated withForest Ecosystem Research Centre, University of Göttingen, Institute of Soil Science and Forest Nutrition

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Abstract

Fluxes of CO2 and N2O were measured along a microclimatic gradient stretching from the centre of a gap into a mature beech stand using an automated chamber method. Simultaneously the regulating factors like soil water tensions, soil temperatures, nitrate concentrations were measured along the gradient. The daily mean values of the fluxes of CO2 and N2O were divided into classes of temperature and furthermore subdivided into classes of soil water tension to assess the significance of each regulating factor.

Soil respiration at the centre of the gap was 40% lower compared to the rooted mature stand. The difference was explained by root respiration. At both sites soil respiration was primarily controlled by the soil temperature with an average Q10 value of 2.3 over the different classes of temperature and soil water tension. Soil water tension reduced the soil respiration by up to 20% only by soil water tension above 400–600 hPa at the mature stand. The formation of N2O was reduced when the soil temperature was below 10°C or the soil water tension exceeded 200 hPa. Therefore the N2O emission was 6 times higher at the unrooted centre of the gap due to the high moisture content in the growing season. Higher nitrate concentration doubled the N2O emission at the unrooted edge of the canopy and resulted in losses of 6.4 kg N ha-1 within six months. Above 10°C and below 200 hPa the N2O emission depended strongly upon the temperature with varying Q10 values over the different classes of temperature and soil water tension. High Q10 values up to 14.4 have been calculated below 14°C and were explained by several processes with synergetic effects.

Key words

CO2 emission gaps N2O emission Q10 values root respiration temperate beech forest