Changes in net ecosystem exchange of CO ₂ , latent and sensible heat fluxes in a recently clear-cut spruce forest in western Russia: results from an experimental and modeling analysis

Abstract

Ecosystem carbon dioxide, energy, and water fluxes were measured using eddy covariance in a fresh clear-cut surrounded by a mixed spruce-birch-aspen forest in the boreal zone of European Russia. Measurements were initiated in spring 2016 following timber harvest and continued for five months. The influence of surrounding forest on air flow and turbulent fluxes within the clear-cut were examined using a process-based two-dimensional (2D) hydrodynamic turbulent exchange model. The clear-cut was a source of CO 2 to the atmosphere prior to onset of vegetation growth during early spring. During this period the mean daily latent (LE) and sensible (H) heat fluxes were very similar and the Bowen ratio (b = H/LE) averaged about 1.0. Daily net ecosystem exchange of CO 2 (NEE) was around 0 gC m À2 d À1 following onset of vegetation growth from mid-spring through summer, while b declined to 0.6-0.7. There was strong diurnal variability in NEE, LE and H over the measurement period that was governed by solar radiation and temperature as well as the leaf area index (LAI) of regrown vegetation. Modeled vertical CO 2 and H 2 O fluxes along a transect that crossed the clear-cut and coincided with the dominate wind direction showed that the clear-cut strongly influenced turbulent fluxes within the atmospheric surface layer. Furthermore, modeled atmospheric dynamics suggested that the clear-cut had a large influence on turbulent fluxes in the downwind forest, but little impact on the upwind side. An aggregated approach including field measurements and process-based models can be a useful approach to estimate energy, water and carbon dioxide fluxes in non-uniform forest landscapes.

Greenhouse gas and energy fluxes in a boreal peatland forest after clearcutting

“…The mean daily QE at Lettosuo during spring and summer right after the clearcutting varied mostly within 0.5-2.5 MJ m -2 day -1 and within 1.0-4.0 MJ m -2 day -1 during the second spring and summer. Compared to the values of 2-10 MJ m -2 day -1 measured in an upland forest in Western Russia (Mamkin et al, 2016), our numbers are low. In the case of QH, the fluxes at Lettosuo were systematically lower than those reported by Mamkin et al (2016), but the difference was not as large as for QE.…”

Mathematical Modeling of Vegetation Heterogeneity and Complex Topography Effects on Turbulent Exchange of GHG within the Atmospheric Surface Layer

“…The developed 2D and 3D models are based on a system of averaged Navier-Stokes and continuity equations for the mean wind-speed components using a 1.5-order closure scheme [5][6][7][8][9][10]:…”

Some relationships between thermodynamic characteristics and water vapor and carbon dioxide fluxes in a recently clear-cut area

“…д.) [Mamkin et al, 2016;Ольчев и др., 2017а]. Исследуемая территория относится к атлантико-континентальной европейской области умеренного климатического пояса с умеренно-теплым летом и продолжительной холодной зимой с устойчивым снежным покровом.…”

“…Сплошная рубка леса на исследуемом участке была произведена в марте-апреле 2016 г. [Mamkin et al, 2016]. После расчистки вырубленного участка и вывоза древесины на вырубке оставалось большое количество пней, полуразложившегося древесного опада и порубочных остатков.…”

“…Измерения были начаты 7 апреля 2016 года, сразу же после вывода с вырубки лесозаготовительной техники, и проводились непрерывно в течение всего вегетационного периода, до конца октября 2016 г. [Mamkin et al, 2016;Ольчев и др., 2017].…”