Net ecosystem exchange of carbon dioxide and water of far eastern Siberian Larch (<I>Larix cajanderii</I>) on permafrost

Abstract

Abstract.Observations of the net ecosystem exchange of water and CO 2 were made during two seasons in 2000 and 2001 above a Larch forest in Far East Siberia (Yakutsk). The measurements were obtained by eddy correlation. There is a very sharply pronounced growing season of 100 days when the forest is leaved. Maximum half hourly uptake rates are 18 µmol m −2 s −1 ; maximum respiration rates are 5 µmol m −2 s −1 . Net annual sequestration of carbon was estimated at 160 gCm −2 in 2001. Applying no correction for low friction velocities added 60 g C m −2 . The net carbon exchange of the forest was extremely sensitive to small changes in weather that may switch the forest easily from a sink to a source, even in summer. June was the month with highest uptake in 2001.The average evaporation rate of the forest approached 1.46 mm day −1 during the growing season, with peak values of 3 mm day −1 with an estimated annual evaporation of 213 mm, closely approaching the average annual rainfall amount. 2001 was a drier year than 2000 and this is reflected in lower evaporation rates in 2001 than in 2000.The surface conductance of the forest shows a marked response to increasing atmospheric humidity deficits. This affects the CO 2 uptake and evaporation in a different manner, with the CO 2 uptake being more affected. There appears to be no change in the relation between surface conductance and net ecosystem uptake normalized by the atmospheric humidity deficit at the monthly time scale. The response to atmospheric humidity deficit is an efficient mechanism to prevent severe water loss during the short intense growing season. The associated cost to the sequestration of carbon may be another explanation for the slow growth of these forests in this environment.

Water use strategies and ecosystem-atmosphere exchange of CO<sub>2</sub> in two highly seasonal environments

“…But they could still lead to immediate CO 2 efflux, partially due to a response of microbes and roots growing very close to the soil surface, but also due to physical effects of wind-related pressure fluctuations on CO 2 efflux from porous soils (Kimball and Lemon, 1971). Such pulse-respiration responses, smaller in magnitude, have also been found for the Siberian pine and larch forests (e.g., Kelliher et al, 1999;Dolman et al, 2004) and they conceal the respiration-temperature relationship (Arneth et al, 1998).…”

“…It has been observed in a deciduous coniferous larch forest of Eastern Siberia (where rates quite suddenly increased from less than 1 µmol m −2 s −1 to maxima around 5 µmol m −2 s −1 ; Dolman et al, 2004), as well as in the temperate biome ), yet it was notably absent from the Scots pine forest and from mixed evergreen dark taiga forests growing nearby the Betula stand (Röser et al, 2002). It may well represent an important evolutionary trait of the entire system.…”

A compact and stable eddy covariance set-up for methane measurements using off-axis integrated cavity output spectroscopy

“…Additionally, 3% of the data series consisted of spikes (CH 4 velocity (u * ) the turbulence of the atmosphere can become too low for the performance of eddy covariance measurements (Wohlfahrt et al, 2005;Dolman et al, 2004). In order to determine the critical u * value for CH 4 eddy covariance measurements at this specific site, the CH 4 flux data and u * data from periods with incoming shortwave radiation (SWin) <20 W m −2 were selected (Dolman et al, 2004). The nightly CH 4 fluxes showed a significant decrease for periods with u * <0.09 m s −1 (Fig.…”

Spatial and seasonal variations of CO2flux and photosynthetic and respiratory parameters of larch forests in East Asia

“…forests are characterized by their deciduous habit, a trait that allows them to endure the extremely cold and dry winters across high latitudes of Eurasia, including the Siberian taiga (Gower and Richards 1990). These forests are considered to have a strong influence on the terrestrial carbon and energy cycles, because of their vast area and the potentially large carbon stocks in their peat soils in the permafrost (Schulze et al 1999;Dolman et al 2004;Ueyama et al 2010). Siberian forests constitute 20% of the world's forested area (Dolman et al 2004), and larch forests cover 37% (Abaimov et al 1998), 70% (Gunin et al 1999) and 13.6% (Jiang and Zhou 2002) of forested areas in Russia, Mongolia and China, respectively.…”

“…These forests are considered to have a strong influence on the terrestrial carbon and energy cycles, because of their vast area and the potentially large carbon stocks in their peat soils in the permafrost (Schulze et al 1999;Dolman et al 2004;Ueyama et al 2010). Siberian forests constitute 20% of the world's forested area (Dolman et al 2004), and larch forests cover 37% (Abaimov et al 1998), 70% (Gunin et al 1999) and 13.6% (Jiang and Zhou 2002) of forested areas in Russia, Mongolia and China, respectively. Larch forests on the permafrost region are considered to be a vulnerable ecosystem, because of the rapid warming during the past few decades due to climate change and irreversible degradation by permafrost melting (Demek 1994).…”