Interpreting the variations in xylem sap flux density within the trunk of maritime pine (Pinus pinaster Ait.): application of a model for calculating water flows at tree and stand levels

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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Vapour flux density and transpiration rate comparisons in a stand of Maritime pine (Pinus pinaster Ait.) in Les Landes forest

Agricultural and Forest Meteorology ◽

10.1016/0168-1923(90)90115-m ◽

1990 ◽

Vol 51 (3-4) ◽

pp. 309-319 ◽

Cited By ~ 95

Author(s):

A. Granier ◽

V. Bobay ◽

J.H.C. Gash ◽

J. Gelpe ◽

B. Saugier ◽

...

Keyword(s):

Flux Density ◽

Transpiration Rate ◽

Pinus Pinaster ◽

Maritime Pine ◽

Pinus Pinaster Ait ◽

Vapour Flux

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Specific responses of sap flux and leaf functional traits to simulated canopy and understory nitrogen additions in a deciduous broadleaf forest

Functional Plant Biology ◽

10.1071/fp18277 ◽

2019 ◽

Vol 46 (11) ◽

pp. 986 ◽

Cited By ~ 1

Author(s):

Liwei Zhu ◽

Yanting Hu ◽

Xiuhua Zhao ◽

Ping Zhao ◽

Lei Ouyang ◽

...

Keyword(s):

Functional Traits ◽

Xylem Sap ◽

Leaf Traits ◽

N Addition ◽

Sap Flux ◽

Sap Flux Density ◽

Leaf Functional Traits ◽

Species Specific ◽

Xylem Sap Flux ◽

N Additions

To investigate the effects of atmospheric nitrogen (N) deposition on water use characteristics and leaf traits of trees, we performed canopy (C50) and understory (U50) N additions as NH4NO3 of 50 kg N ha–1 year–1 in a deciduous broadleaf forest of central China. We measured xylem sap flux, crown area:sapwood area ratio (Ca:As), specific leaf area (SLA), mass-based leaf nitrogen content (Nmass) and leaf carbon isotope ratio (δ13C) of Liquidambar formosana Hance, Quercus acutissima Carruth. and Quercus variabilis Blume. Functional traits under different N addition treatments and their responses among tree species were compared and the relationship between xylem sap flux and leaf functional traits under N additions were explored. Results showed that under U50 sap-flux density of xylem significantly decreased for three tree species. But the effect of C50 on sap flux was species-specific. The decrease of sap-flux density with N additions might be caused by the increased Ca/As. δ13C remained constant among different N addition treatments. The responses of SLA and Nmass to N additions were species- and N addition approaches-specific. The correlation of xylem sap flux with leaf traits was not found. Our findings indicate that the effects of canopy N addition on xylem sap flux and leaf functional traits were species-specific and it is necessary to employ canopy N addition for exploring the real responses of forest ecosystems to climate changes in the future researches.

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