Sapwood as the scaling parameter- defining according to xylem water content or radial pattern of sap flow?

Čermák, Jan; Nadezhdina, Nadezhda

doi:10.1051/forest:19980501

Cited by 140 publications

(57 citation statements)

References 8 publications

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“…Most species with differentiated sapwood and heartwood contain about 10-12% v water in the heartwood (Cermák and Nadezhdina 1998;Kravka et al 1999). This water is bound, evidently strongly held by the physical forces in the xylem, and is not available for physiological processes (Zimmermann and Brown 1971).…”

Section: Discussionmentioning

confidence: 99%

“…Nevertheless the moisture content varies among species. In most gymnosperms and some angiosperms it is higher in sapwood than in heartwood while in some other angiosperms the opposite occurs (Cermák and Nadezhdina 1998). There are also many species where differences in moisture in either zone cannot be found (Kozlowski and Pallardy 1997), which makes its direct determination difficult.…”

Section: Introductionmentioning

confidence: 99%

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Laurel forests in Tenerife, Canary Islands

Morales

Jiménez

González‐Rodríguez

et al. 2002

Trees

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The general wood structure, vessel size and distribution along the stem xylem radius and in petioles were studied in Laurus azorica trees living in a Tenerife laurel forest. The fractions of volume occupied by dry matter, water and air in percentage of wood fresh volume were also studied. The wood showed a diffuse-porous structure, with solitary vessels or vessels somewhat clustered in small radially oriented groups. Vessels had a diameter ranging from 20 to 130 µm. This diameter was minimal close to the pith, increased more than 2-fold with age, and reached its maximum width close to the cambium. Vessel density decreased from 36 vessels mm -2 near the pith to about 13 vessels mm -2 near the cambium. Accordingly, the lumen area was small in young xylem close to the pith (0.0015 mm 2 ), reaching a value 5 times larger (0.007 mm 2 ) near the cambium than in the centre of the stem. Lumen area of vessels in petioles was about 1.5% of petiole cross-sectional area and thus much lower than in stems. Mean hydraulic diameter of these vessels was about 20 µm, and mean vessel density about 136 per petiole. There were only small differences in proportions of dry matter, water and air along stem radius. The relevance of each one of these fractions in the wood is discussed as evidence of the possible existence of a number of embolized vessels dispersed in the total functional cross-sectional area of the xylem.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laurel forests in Tenerife, Canary Islands

Morales

Jiménez

González‐Rodríguez

et al. 2002

Trees

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“…In this case the transpiration estimates depend on a sub-sample of trees that is assumed representative of the population of trees within the stand. Errors can also occur if the radial patterns of sap flow in the tree trunks are not considered (Hatton et al, 1995;Cermák and Nadezhdina, 1998). In addition, up-scaling from the sample trees to the whole stand requires an accurate estimate of the distribution of suitable biometric parameters of the stand (Cermák and Kucera, 1990;Cermák 1989).…”

Section: Four Methods To Assess (Evapo)transpiration: Strengths and Wmentioning

confidence: 99%

Water flux estimates from a Belgian Scots pine stand: a comparison of different approaches

Meiresonne

Sampson

Kowalski

et al. 2003

Journal of Hydrology

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Four distinct approaches, that vary markedly in the spatial and temporal resolution of their measurement and process-level outputs, are used to investigate the daily and seasonal water vapour exchange in a 70-year-old Belgian Scots pine forest. Transpiration, canopy interception, soil evaporation and evapotranspiration are simulated, using a stand-level process model (SECRETS) and a soil water balance model (WAVE). Simulated transpiration was compared with up-scaled sap flow measurements and simulated evapotranspiration to eddy covariance measurements.Reasonable agreement in the temporal trends and in the annual water balance between the two models was observed, however daily and weekly predictions often diverged. Most notably, WAVE estimated very low, to no transpiration during late autumn, winter and early spring when incident radiation fell below ,50 W m 22 while SECRETS simulated low (0.1-0.4 mm day 21 ) fluxes during the same period. Both models exhibited similar daily trends in simulated transpiration when compared with sap flow estimates, although simulations from SECRETS were more closely aligned. In contrast, WAVE over-estimated transpiration during periods of no rainfall and under-estimated transpiration during rainfall. Yearly, total evapotranspiration simulated by the models were similar, i.e. 658 mm (1997) and 632 mm (1998) for WAVE and 567 mm (1997) and 619 mm (1998) for SECRETS.Maximum weekly-average evapotranspiration for WAVE exceeded 5 mm day 21 , while SECRETS never exceeded 4 mm day 21 . Both models, in general, simulated higher evapotranspiration than that measured with the eddy covariance technique. An impact of the soil water content in the direct relationship between the models and the eddy covariance measurements was found.The results suggest that: (1) differentmodel formulations can reproduce similar results dependingon the scale at which outputs are resolved, (2) SECRETS estimates of transpiration were well correlated with the empirical measurements, and (3) neither model fitted favourably to the eddy covariance technique. q

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“…The radial profile of conducting pathways was examined in stems of many woody species from different viewpoints including the homogeneity of water supply to crowns, plant protection against insects or proper integration of sap flow rates to obtain correct data on whole plant water use (Kozlowski and Wignet 1963;Swanson 1971;Waisel et al 1972;Edwards and Booker 1984;Hatton et al 1990;Cermák et al 1992;Cermák and Nadezhdina 1998;Jiménez et al 2000;Nadezhdina et al 2001).…”

Section: Introductionmentioning

confidence: 99%

“…The true functional area of conducting xylem may differ significantly from that of sapwood if estimated by the usual methods (e.g. based on tissue water content or presence of living cells), as was shown in several contrasting species (Cermák and Nadezhdina 1998). To elucidate the functional situation along the stem radius, theoretically calculated properties of the conducting system were compared to those obtained by direct measurements using staining and stem heat balance sap flow rate measurement techniques.…”

Section: Introductionmentioning

confidence: 99%

Laurel forests in Tenerife, Canary Islands

Čermák

Jimenez

González‐Rodríguez

et al. 2002

Trees

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The efficiency of the conductive system in about 40-year-old Laurus azorica trees growing in a laurel forest was evaluated by comparing main stems and leaves (petioles) on the basis of theoretical sap flow values (1) calculated from vessel anatomy (taking vessels as ideal capillaries), (2) derived from measured dye velocity and (3) data taken from direct sap flow measurements. It was found that actual sap flow rate per wood area increases in stems from the pith towards the cambium. The outermost part of the stem is the most important part of the tree for conducting water. Maximum actually measured transpiration (sap flow rate) for the stand was practically identical to the theoretical rate calculated based on petiole anatomy, but it was about 45 times lower than that calculated based on stem anatomy. This illustrates the safety features of stem wood, which due to its high vessel density, is capable of transporting all the water required even when only a small area of its vessels is working. In the petioles, xylem is more efficiently used, but almost all vessels must work in order to supply water to leaves and any disturbance may cause leaf loss.

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Sapwood as the scaling parameter- defining according to xylem water content or radial pattern of sap flow?

Cited by 140 publications

References 8 publications

Laurel forests in Tenerife, Canary Islands

Laurel forests in Tenerife, Canary Islands

Water flux estimates from a Belgian Scots pine stand: a comparison of different approaches

Laurel forests in Tenerife, Canary Islands

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