Radial variations in xylem sap flux in a temperate red pine plantation forest

Abstract Background Scaling sap flux measurements to whole-tree water use or stand-level transpiration is often done using measurements conducted at a single point in the sapwood of the tree and has the potential to cause significant errors. Previous studies have shown that much of this uncertainty is related to (i) measurement of sapwood area and (ii) variations in sap flow at different depths within the tree sapwood. Results This study measured sap flux density at three depth intervals in the sapwood of 88-year-old red pine (Pinus resinosa) trees to more accurately estimate water-use at the tree- and stand-level in a plantation forest near Lake Erie in Southern Ontario, Canada. Results showed that most of the water transport (65%) occurred in the outermost sapwood, while only 26% and 9% of water was transported in the middle and innermost depths of sapwood, respectively. Conclusions These results suggest that failing to consider radial variations in sap flux density within trees can lead to an overestimation of transpiration by as much as 81%, which may cause large uncertainties in water budgets at the ecosystem and catchment scale. This study will help to improve our understanding of water use dynamics and reduce uncertainties in sap flow measurements in the temperate pine forest ecosystems in the Great Lakes region and help in protecting these forests in the face of climate change.

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Water use of interior Douglas-fir

Canadian Journal of Forest Research ◽

10.1139/x99-233 ◽

2000 ◽

Vol 30 (4) ◽

pp. 534-547 ◽

Cited By ~ 4

Author(s):

David G Simpson

Keyword(s):

Flux Density ◽

Water Use ◽

Early Summer ◽

Douglas Fir ◽

Stem Volume ◽

Curvilinear Relationship ◽

Sap Flux ◽

Sap Flux Density ◽

Sapwood Area ◽

Xylem Pressure Potential

Water use of individual Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) trees was measured in two plots at a forest site in southern British Columbia, Canada. Average daily early summer water use by trees with diameters of 7.5-70 cm varied from 1.8 to 166 L. Sap flux density (cm3 water/cm2 sapwood per hour) was linearly related to shoot xylem pressure potential and was found to increase with increasing vapour pressure deficit (VPD) and short-wave irradiance (I), reaching maximum rates with VPD > 0.6 kPa and I > 200 W·m-2. Daily sap flux density varied among trees but was not related to tree diameter, so an average value of 1137.4 L·m-2 sapwood area was used to estimate average early summer stand transpiration for the two plots of 1.08 and 1.5 mm·d-1. A close curvilinear relationship (r2 = 0.85) was found between stem cross-sectional area increment and sapwood area. The relationship was only slightly better (r2 = 0.89) between area increment and early summer individual tree water use. Stand volume growth for 1988-1998 for the two plots was 36-47 m3·ha-1. Stem volume relative growth rate over this 10-year period is estimated at 0.027 and 0.029 m3·m-3·a-1.

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Assessing variation in the radial profile of sap flux density in Pinus species and its effect on daily water use

Tree Physiology ◽

10.1093/treephys/24.3.241 ◽

2004 ◽

Vol 24 (3) ◽

pp. 241-249 ◽

Cited By ~ 133

Author(s):

C. R. Ford ◽

M. A. McGuire ◽

R. J. Mitchell ◽

R. O. Teskey

Keyword(s):

Flux Density ◽

Water Use ◽

Radial Profile ◽

Sap Flux ◽

Sap Flux Density ◽

Pinus Species ◽

Daily Water

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A Direct Method for Estimating the Average Sap Flux Density Using a Modified Granier Measuring System

Functional Plant Biology ◽

10.1071/pp96099 ◽

1997 ◽

Vol 24 (5) ◽

pp. 701 ◽

Cited By ~ 11

Author(s):

Ping Lu

Keyword(s):

Flux Density ◽

Sap Flow ◽

Direct Method ◽

Estimation Error ◽

Original Method ◽

Measuring System ◽

Sap Flux ◽

Sap Flux Density ◽

Average Value ◽

Modified Method

The Granier sap flow measuring system that normally uses one analogue input channel of a datalogger for each sensor was modified to enable one channel to measure the average value of signals from two or more sensors. The sap flux density calculated from this average value of signals was very close (difference < 6.0%) to the arithmetic mean of the sap flux densities measured separately by means of individual sensors (using two or more input channels). The dynamics of the sap flux density measured by the modified method were similar to those measured by the original method. On a per-channel basis, the modified method reduced the ‘estimation error’ of sap flux density by 4–14-fold compared to the original method. By using the modified Granier system, the error in sap flow measurement that is usually associated with limited sampling can be substantially reduced without the need for extra dataloggers, the greatest item of expense.

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The importance of conduction versus convection in heat pulse sap flow methods

Tree Physiology ◽

10.1093/treephys/tpaa009 ◽

2020 ◽

Vol 40 (5) ◽

pp. 683-694

Author(s):

Michael A Forster

Keyword(s):

Flux Density ◽

Sap Flow ◽

Peclet Number ◽

Velocity Measurement ◽

Measurement Range ◽

Heat Pulse ◽

Sap Flux ◽

Sap Flux Density ◽

Péclet Number ◽

Fast Methods

Abstract Heat pulse methods are a popular approach for estimating sap flow and transpiration. Yet, many methods are unable to resolve the entire heat velocity measurement range observable in plants. Specifically, the Heat Ratio (HRM) and Tmax heat pulse methods can only resolve slow and fast velocities, respectively. The Dual Method Approach (DMA) combines optimal data from HRM and Tmax to output the entire range of heat velocity. However, the transition between slow and fast methods in the DMA currently does not have a theoretical solution. A re-consideration of the conduction/convection equation demonstrated that the HRM equation is equivalent to the Péclet equation which is the ratio of conduction to convection. This study tested the hypothesis that the transition between slow and fast methods occurs when conduction/convection, or the Péclet number, equals one, and the DMA would be improved via the inclusion of this transition value. Sap flux density was estimated via the HRM, Tmax and DMA methods and compared with gravimetric sap flux density measured via a water pressure system on 113 stems from 15 woody angiosperm species. When the Péclet number ≤ 1, the HRM yielded accurate results and the Tmax was out of range. When the Péclet number > 1, the HRM reached a maximum heat velocity at approximately 15 cm hr −1 and was no longer accurate, whereas the Tmax yielded accurate results. The DMA was able to output accurate data for the entire measurement range observed in this study. The linear regression analysis with gravimetric sap flux showed an r2 of 0.541 for HRM, 0.879 for Tmax and 0.940 for DMA. With the inclusion of the Péclet equation, the DMA resolved the entire heat velocity measurement range observed across 15 taxonomically diverse woody species. Consequently, the HRM and Tmax are redundant sap flow methods and have been superseded by the DMA.

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Contribution of Advanced Regeneration of Pinus radiata D. Don. to Transpiration by a Fragment of Native Forest in Central Chile Is out of Proportion with the Contribution to Sapwood Area

Forests ◽

10.3390/f11020187 ◽

2020 ◽

Vol 11 (2) ◽

pp. 187

Author(s):

Don A. White ◽

Richard P. Silberstein ◽

Francisco Balocchi-Contreras ◽

Juan Jose Quiroga ◽

Pablo Ramírez de Arellano

Keyword(s):

Climate Change ◽

Leaf Area ◽

Flux Density ◽

Pinus Radiata ◽

Native Forest ◽

Sap Flux ◽

Sap Flux Density ◽

Sapwood Area ◽

Central Chile ◽

Potential Index

The transpiration of Nothofagus glauca (Phil.) Krasser and advanced Pinus radiata D. Don. regeneration was measured in a fragment of native N. glauca forest. Over the eight months of this study, P. radiata contributed approximately 60% of the total stand transpiration. This was out of proportion with the approximately 34% of the stand sapwood area contributed by P. radiata. This was due to the significantly greater sap flux density of the P. radiata compared to the N. glauca between May and October. Though the results are from a small study conducted as part of a larger experiment, it is argued that they suggest that invasion by P. radiata may substantially increase the risk from climate change to reserves of N. glauca forest in the Maule region of central Chile. In some reserves of N. glauca forest, Forestal Arauco S.A. manually removed P. radiata that regenerated after the wildfire of January 2017. This was a costly operation and there is a need for indices to assess competition. The ratio of sapwood area to leaf area is suggested as a potential index for assessing competition to identify stands at risk.

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Spatial variations in xylem sap flux density in the trunk of orchard-grown, mature mango trees under changing soil water conditions

Tree Physiology ◽

10.1093/treephys/20.10.683 ◽

2000 ◽

Vol 20 (10) ◽

pp. 683-692 ◽

Cited By ~ 87

Author(s):

P. Lu ◽

W. J. Muller ◽

E. K. Chacko

Keyword(s):

Soil Water ◽

Flux Density ◽

Xylem Sap ◽

Spatial Variations ◽

Sap Flux ◽

Sap Flux Density ◽

Water Conditions ◽

Soil Water Conditions ◽

Xylem Sap Flux

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Spatial variability of xylem sap flow in mature beech (Fagus sylvatica) and its diurnal dynamics in relation to microclimate

Botany ◽

10.1139/b08-112 ◽

2008 ◽

Vol 86 (12) ◽

pp. 1440-1448 ◽

Cited By ~ 29

Author(s):

An Saveyn ◽

Kathy Steppe ◽

Raoul Lemeur

Keyword(s):

Fagus Sylvatica ◽

Sap Flow ◽

Xylem Sap ◽

Radial Profile ◽

Vapour Pressure Deficit ◽

Climatic Conditions ◽

General Function ◽

Sap Flux Density ◽

Sapwood Area ◽

Diurnal Variability

The spatial and diurnal variability of sap flow in a mature beech tree ( Fagus sylvatica L.) was investigated on days with different climatic conditions (sunny, cloudy, rainy), during the summer. Sap flux density (v) was measured with six heat field deformation probes placed around the stem circumference. Each probe measured v at six sapwood depths. Daily v exhibited clear radial variation, and the shape of the radial profile of v differed substantially among circumferential positions. At some positions, daily v decreased monotonically towards the stem centre, whereas at others it showed an almost monotonic increase. Hence, the conducting sapwood area of the beech was highly asymmetrical. At all positions, conducting sapwood reached beyond the deepest sampled sapwood depth, precluding correct estimations of total sap flow. The radial profile of v also differed among measuring days. A general trend was that the inner sapwood contributed relatively more to total sap flow under better weather conditions. Besides variations among days, the shape of the radial profile of v also showed within-day variations. The contribution of the inner sapwood to total sap flow increased in the afternoon, with increasing vapour pressure deficit and photosynthetic active radiation. Because of large circumferential and temporal variability, no general function for the radial profile of v could be developed.

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Influence of temporospatial variation in sap flux density on estimates of whole-tree water use in Avicennia marina

Trees ◽

10.1007/s00468-014-1105-z ◽

2014 ◽

Vol 29 (1) ◽

pp. 215-222 ◽

Cited By ~ 14

Author(s):

Bart A. E. Van de Wal ◽

Adrien Guyot ◽

Catherine E. Lovelock ◽

David A. Lockington ◽

Kathy Steppe

Keyword(s):

Flux Density ◽

Water Use ◽

Avicennia Marina ◽

Sap Flux ◽

Sap Flux Density ◽

Tree Water Use ◽

Whole Tree

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Water Use by Chinese Pine Is Less Conservative but More Closely Regulated Than in Mongolian Scots Pine in a Plantation Forest, on Sandy Soil, in a Semi-Arid Climate

Frontiers in Plant Science ◽

10.3389/fpls.2021.635022 ◽

2021 ◽

Vol 12 ◽

Author(s):

Hongzhong Dang ◽

Xueli Zhang ◽

Hui Han ◽

Shuai Chen ◽

Mingyang Li

Keyword(s):

Soil Water ◽

Water Use ◽

Scots Pine ◽

Xylem Sap ◽

Soil Layer ◽

Northern China ◽

Plantation Forest ◽

Sap Flux Density ◽

Chinese Pine ◽

Dry Conditions

The diversity of plant water use patterns among species and ecosystems is a matter of widespread debate. In this study, Chinese pine (Pinus tabuliformis, CP) and Mongolian Scots pine (Pinus sylvestris var. mongolica, MP), which is co-exist in the shelterbelt plantations in the Horqin Sandyland in northern China, were chosen for comparison of water use traits by monitoring xylem sap flow alongside recordings of the associated environmental factors over four growing seasons. Continuous sap flux density measurements were converted into crown projected area transpiration intensity (Tr) and canopy stomatal conductance (Gs). The results indicated that MP showed a higher canopy transpiration intensity than in CP, with Tr daily means (±standard deviation) of 0.84 ± 0.36 and 0.79 ± 0.43 mm⋅d–1, respectively (p = 0.07). However, the inter-annual variability of daily Tr in MP was not significant, varying only approximately a 1.1-fold (p = 0.29), while inter-annual variation was significant for CP, with 1.24-fold variation (p < 0.01). In particular, the daily mean Tr value for CP was approximately 1.7-times higher than that of MP under favorable soil moisture conditions, with values for relative extractable soil water within the 0–1.0 m soil layer (REW) being above 0.4. However, as the soil dried out, the value of Tr for CP decreased more sharply, falling to only approximately 0.5-times the value for MP when REW fell to < 0.2. The stronger sensitivity of Tr and/or Gs to REW, together with the more sensitive response of Gs to VPD in CP, confirms that CP exhibits less conservation of soil water utilization but features a stronger ability to regulate water use. Compared with MP, CP can better adapt to the dry conditions associated with climate change.

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