Evapotranspiration of beech stands and transpiration of beech leaves subject to atmospheric CO2 enrichment

Abstract

Beech trees (Fagus sylvatica L.) show reduced stomatal conductance and increased leaf area index in response to increased atmospheric CO(2) concentration. To determine whether the reduction in stomatal conductance results in lower stand evapotranspiration, we compared transpiration on a leaf-area basis and stand evapotranspiration on a ground-area basis in young European beech trees growing in greenhouses at ambient (360 +/- 34 micro mol mol(-1)) and elevated (698 +/- 10 micro mol mol(-1)) CO(2) concentrations. Trees were grown in homogenized natural soil at constant soil water supply for two growing seasons. At light saturation, leaf transpiration rates were, on average, 18% lower in the elevated CO(2) treatment than in the ambient CO(2) treatment. Mean transpiration coefficients (transpiration/net CO(2) uptake) of leaves were 179 and 110 in the ambient and elevated CO(2) treatments, respectively, indicating improved water use efficiency in trees in the elevated CO(2) treatment. Total leaf conductance was decreased by 32% at light saturation. The elevated CO(2) treatment resulted in a 14% reduction in stand evapotranspiration. In both CO(2) treatments, evapotranspiration increased linearly at a rate of 0.2 kg H(2)O m(-2) day(-1) for each 1 degrees C rise in air temperature between 14 and 25 degrees C. We conclude that, under Central European conditions, water losses from deciduous forest stands will be reduced by a doubling of tropospheric CO(2) concentration.

Carbon and water fluxes in Beech–Spruce model ecosystems in response to long‐term exposure to atmospheric CO2 enrichment and increased nitrogen deposition

“…From a substantial number of recent studies examining leaves from forest trees, no evidence was found of stomatal adjustment in response to elevated CO 2 (Ellsworth et al 1995;Teskey 1995;Körner & Würth 1996;Tognetti et al 1996). These findings contrast with those reported for the dense sapling stands of Beech of Overdieck & Forstreuter (1994) which describe a significant reduction in the evapotranspiration rate under elevated CO 2 , despite of a 45% increase in LAI and a comparatively small decrease (18%) in stomatal conductance, perhaps this is attributable to the very special behaviour of small saplings not transferable to bigger trees (Loehle 1995). Grassland ecosystems, however, generally tend to reduce their water consumption under elevated CO 2 (Owensby et al 1997;Zaller & Arnone 1997;Jackson et al 1998).…”

Environmental control of leaf area production: Implications for vegetation and land‐surface modeling

“…This was primarily a result of our incorporating Chen et al, 1997aChen et al, , 1997bEwers et al, 1999;Lawson et al, 2001;Lee et al, 1997;Mayeux et al, 1997;Mullholland et al, 1997Mullholland et al, , 1998Rowland-Bamford et al, 1991;Rudorff et al, 1996;Sims et al, 1999woody 8 Ceulemans et al, 1995Idso et al, 1993;Jach et al, 2000;Overdieck and Forstreuter, 1994;Tingey et al, 1996 global field data, which meant that LAI data were aggregated from experimental plots having soils of differing texture, composition and nutrient composition. Fertilization regimes also differed between studies; nitrogen (N) was added alone or with small amounts of phosphorus (P) and potassium (K), equal parts N:P:K, or large amounts of macronutrients (N, P, K) with small additions of micronutrients (i.e., S, Zn).…”

Interactive effects of elevated [CO2] and drought on cherry (Prunus avium) seedlings II. Photosynthetic capacity and water relations

“…The daily pattern of E per unit of leaf area was also not affected in a different experiment on F. sylvatica using the branch-bag technique (Dufre# ne et al, 1993). However, evapotranspiration on a ground-area basis was reduced and leaf-area index increased in a small stand of F. sylvatica grown in elevated [CO # ] (Overdieck & Forstreuter, 1994).…”