Bayreuther Institut für Terrestrische Ökosystemforschung
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Exchange processes at the vegetation-atmosphere-interface: canopy transpiration and conductance as key variables in forests of different structure


From 01/1995 to 12/1997

Principal Investigator: John Tenhunen
Staff: Barbara Köstner
Grant: 0339476 B Vorhersage und Erklärung des Verhaltens und der Belastbarkeit von Ökosystemen unter veränderten Umweltbedingungen

Examining effects of land-use change or changes of the physical and chemical environment on ecosystem function requires knowledge of stand level ecosystem response related to atmospheric factors and forest structure. In this context, canopy transpiration (Ec) andr conductance (gt) of forests are key parameters describing ecosystem function and defining functional types of vegetation. Xylem sapflow measurements were applied to investigate relationships between tree or forest structure and water uptake in order to scale water use of trees to the forest canopy level and to compare forest stands of different structure. In even-aged forests of Picea abies (770m a.s.l.) differences in Ec between stands were high (Ecmax 1.5-2.5 mm d-1) and associated with changes in leaf area/sapwood area relationships and stand density. Maximum canopy conductance decreased with stand age (40 to 140 years) from values of 13 mm s-1 to low values of 5 mm s-1. Correspondingly, coupling of vegetation and atmosphere was typically strong for all spruce stands (mean de-coupling factor ½ = 0.1-0.2, 0.25-0.4 for dry and humid days, respectively) but was more pronounced in the oldest stand compared to the younger stands. In a mixed forest of Fagus sylvatica and Picea abies (380m a.s.l.) estimates of Ec and gt at the tree and stand level were up to twice as high for patches of beech trees (7 mm d-1; 15 mm s-1) compared to spruce (3 mm d-1; 9 mm s-1) although tree density was higher for the spruce compared to the beech stand. Further it was observed, that Ec of beech patches neigbored to spruce could exceed available energy on dry summer days. This indicates that at the landscape level, advection may play an important role in the water use of patchy mosaics of conifers and broad-leaved trees like beech. (final report 1998)

List of publications of this Project

Tenhunen, JD; Valentini, R; Köstner, B; Zimmermann, R; Granier, A: Variation in forest gas exchange at landscape to continental scales, Annales des Sciences Forestières, 55, 1-11 (1998) -- Details
Köstner, B; Schupp, R; Schulze, ED; Rennenberg, H: Sulfur transport in the xylem sap of spruce (Picea abies(L.) Karst.) and its significance for the trees sulfur budget, Tree Physiology, - (1998)
Köstner, B; Falge, E; Alsheimer, M; Geyer, R; Tenhunen, JD: Estimating tree canopy water use via xylem sapflow in an old Norway spruce forest and a comparison with simulation-based canopy transpiration estimates, Annales des Sciences Forestières, 55, 125-139 (1998) -- Details
Alsheimer, M; Köstner, B; Falge, E; Tenhunen, JD: Temporal and spatial variation in transpiration of Norway spruce stands within a forested catchment of the Fichtelgebirge, Germany, Annales des Sciences Forestières, 55, 103-123 (1998) -- Details
Köstner, B; Granier, A; Cermák, J: Sapflow measurements in forest stands: methods and uncertainties, Annales des Sciences Forestières, 55, 13-27 (1998) -- Details
Sturm, N; Köstner, B; Hartung, W; Tenhunen, JD: Environmental and endogenous controls on leaf- and stand-level water conductance in a Scots pine plantation, Annales des Sciences Forestières, 55, 237-253 (1998) -- Details
Wedler, M; Heindl, B; Hahn, S; Köstner, B; Bernhofer, C; Tenhunen, JD: Model-based estimates of water loss from "patches" of the understory mosaic of the Hartheim Scots Pine plantation, Theoretical and Applied Climatology, 53, 135-144 (1996) -- Details
Köstner, B; Alsheimer, M; Tenhunen, JD: Tree canopy transpiration at different sites of a spruce forest ecosystem, Verhandlungen der Gesellschaft für Ökologie, 26, 61-68 (1996) -- Details
Granier, A; Biron, P; Köstner, B; Gay, LW; Najjar, G: Comparisons of xylem sap flow and water vapor flux at the stand level and derivation of canopy conductance for Scots pine, Theoretical and Applied Climatology, 53, 115-122 (1996)
Wedler, M; Köstner, B; Tenhunen, JD: Understory contribution to stand total water loss at an old Norway spruce forest , Verhandlungen der Gesellschaft für Ökologie, 26, 69-77 (1996)
Vogt, R; Gay, L; Tenhunen, JD; Bernhofer, C; Kessler, A: HartX 92 - Vegetation-atmosphere coupling of a Scots pine plantation, Theoretical and Applied Climatology, 53, 1-3 (1996)
Köstner, B; Biron, P; Siegwolf, R; Granier, A: Estimates of water vapor flux and canopy conductance of Scots pine at the tree level utilizing different xylem sap flow methods, Theoretical and Applied Climatology, 53, 105-113 (1996) -- Details
Phillips, N; Oren, R; Zimmermann, R: Radial patterns of xylem sap flow in non-, diffuse- and ring-porous tree species, Plant, Cell and Environment, 19, 983-990 (1996)
Heindl, B; Ostendorf, B; Köstner, B: Lage und forstliche Charakterisierung des Einzugsgebietes Lehstenbach in Bayreuther Institut für Terrestrische Ökosystemforschung (BITÖK): Bayreuther Forum Ökologie, Selbstverlag, 18, 7-13 (1995)
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