INFLUENCE OF SPATIAL VARIATION IN SAP FLUX DENSITY ON ESTIMATES OF WHOLE-TREE WATER USE IN AVICENNIA MARINA

BackgroundPlant-water relations have been of significant concern in forestry and ecology studies in recent years, yet studies investigating the annual differences in the characteristics of inter-class water consumption in trees are scarce.MethodsWe classified 15 trees from aSchima superbaplantation in subtropical South China into four ranks using diameter at breast height (DBH). The inter-class and whole-tree water use were compared based on three parameters: sap flux density, whole-tree transpiration and canopy transpiration over two years. Inter-class hydraulic parameters, such as leaf water potential, stomatal conductance, hydraulic conductance, and canopy conductance were also compared.Results(1) Mean water consumption of the plantation was 287.6 mm over a year, 165.9 mm in the wet season, and 121.7 mm in the dry season. Annual mean daily water use was 0.79 mm d−1, with a maximum of 1.39 mm d−1. (2) Isohydrodynamic behavior were found inS. superba. (3) Transpiration was regulated via both hydraulic conductance and stoma; however, there was an annual difference in which predominantly regulated transpiration.DiscussionThis study quantified annual and seasonal water use of aS. superbaplantation and revealed the coordinated effect of stoma and hydraulic conductance on transpiration. These results provide information for large-scale afforestation and future water management.

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Rainfall pattern greatly affects water use by Mongolian Scots pine on a sandy soil, in a semi-arid climate

10.5194/bg-2017-69 ◽

2017 ◽

Author(s):

Hongzhong Dang ◽

Lizhen Zhang ◽

Wenbin Yang ◽

Jinchao Feng ◽

Hui Han ◽

...

Keyword(s):

Soil Moisture ◽

Water Use ◽

Sandy Soil ◽

Heavy Rainfall ◽

Rainfall Pattern ◽

Severe Drought ◽

Sap Flux ◽

Sap Flux Density ◽

Tree Water Use ◽

Moderate Drought

Abstract. We report new information on tree water use by Mongolian Scots pine (Pinus sylvestris var. mongolica) growing on a sandy soil, in a region characterised by an erratic rainfall pattern. Measurements were made over three successive years of contrasting annual rainfall – a wet year (2013), a dry year (2014), and a second dry year (2015). The result was the development of worsening levels of drought year by year. Over the three years, sap flux density (Js) was measured at individual tree level in up to 25 trees. The sap flux density values were up-scaled to estimate tree water use at plot level (Ts). Our measurements follow forest plot response to increasing levels of drought which developed over a three-year period as soil moisture conditions gradually worsened from wet, to moderate-drought, to severe-drought, to extreme-drought, in response to the dynamics of a variable rainfall pattern. Values of Ts did not exceed 3.03 mm day−1 (2013), 1.75 mm day−1 (2014) and 1.59 mm day−1 (2015) during the three growing seasons. Total annual stand transpiration over the same three years declined progressively from 290 mm (2013), to 182 mm (2014) and to 175 mm (2015). Satisfactory power-function relationships (R2 = 0.64) between daily Ts and the product of ET0 and the relative extractable soil water (REW) were found. This study helps elucidate the interplay between the effects of the atmosphere and soil moisture on tree water use. Tree water use responded to drought, with daily Ts values decreasing by 5–46 % in response to moderate drought, by 48–62 % in response to severe drought and by 65 % in response to extreme drought. Upon release of moderate drought by heavy rainfall in 2013, daily Ts recovered completely. However, under the severe and extreme droughts in the subsequent dry years, recovery of Ts following heavy rainfall was incomplete (57–58 %). Our results highlight the negative effects of water stress on the growth of mature forest trees, in a sandy soil, in a climate characterised by large intra- and inter-annual variances in rainfall. When the erratic rainfall and sandy soil were also coupled with a declining groundwater table, the result was tree water use fluctuated widely over quite short time scales (months or weeks). Overall, our findings account for the observed premature degradation of these MP plantations in terms of an eco-hydrological perspective.

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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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Responses of Sap Flux Densities of Different Plant Functional Types to Environmental Variables Are Similar in Both Dry and Wet Seasons in a Subtropical Mixed Forest

Forests ◽

10.3390/f12081007 ◽

2021 ◽

Vol 12 (8) ◽

pp. 1007

Author(s):

Kechao Huang ◽

Quan Wang ◽

Dennis Otieno

Keyword(s):

Flux Density ◽

Water Use ◽

Environmental Variables ◽

Environmental Changes ◽

Mixed Forest ◽

Plant Functional Types ◽

Photon Flux ◽

Sap Flux ◽

Sap Flux Density ◽

Functional Types

Subtropical mixed forest ecosystems are experiencing dramatic changes in precipitation and different plant functional types growing here are expected to respond differently. This study aims to unravel the water use patterns of different plant functional types and their responses to environmental changes in a typical subtropical mixed forest in southern China. Diurnal and seasonal sap flux densities of evergreen broad-leaved trees (EBL), deciduous broad-leaved trees (DBL), and conifers (CON), as well as environmental variables, were recorded simultaneously from May 2016 to March 2019. The results showed that the sap flux density of EBL was significantly higher than those of CON and DBL in all seasons, irrespective of dry or wet seasons. Path analysis revealed that seasonal differences in sap flux density were mainly due to variations in photosynthetic photon flux density (PPFD). At saturating PPFD, changes in sap flux density during the day were in response to vapor pressure deficit (VPD). Regression analyses showed that sap flux density increased logarithmically with PPFD, irrespective of functional type. The hysteresis loops of sap flux density and VPD were different among different plant functional types in wet and dry seasons. Our results demonstrated converging response patterns to environmental variables among the three plant functional types considered in this study. Our findings contribute to a better understanding of the water use strategies of different plant functional types in subtropical mixed forests.

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

Ecological Processes ◽

10.1186/s13717-021-00295-4 ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Alanna V. Bodo ◽

M. Altaf Arain

Keyword(s):

Flux Density ◽

Water Use ◽

Sap Flow ◽

Xylem Sap ◽

Red Pine ◽

Sap Flux ◽

Plantation Forest ◽

Sap Flux Density ◽

Flow Measurements ◽

Sapwood Area

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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Effects of Wood Hydraulic Properties on Water Use and Productivity of Tropical Rainforest Trees

Frontiers in Forests and Global Change ◽

10.3389/ffgc.2020.598759 ◽

2021 ◽

Vol 3 ◽

Author(s):

Martyna M. Kotowska ◽

Roman M. Link ◽

Alexander Röll ◽

Dietrich Hertel ◽

Dirk Hölscher ◽

...

Keyword(s):

Flux Density ◽

Water Use ◽

Wood Density ◽

Wood Anatomy ◽

Tree Size ◽

Plant Performance ◽

Strong Positive Correlation ◽

Sap Flux ◽

Sap Flux Density ◽

Stem Increment

The efficiency of the water transport system in trees sets physical limits to their productivity and water use. Although the coordination of carbon assimilation and hydraulic functions has long been documented, the mutual inter-relationships between wood anatomy, water use and productivity have not yet been jointly addressed in comprehensive field studies. Based on observational data from 99 Indonesian rainforest tree species from 37 families across 22 plots, we analyzed how wood anatomy and sap flux density relate to tree size and wood density, and tested their combined influence on aboveground biomass increment (ABI) and daily water use (DWU). Results from pairwise correlations were compared to the outcome of a structural equation model (SEM). Across species, we found a strong positive correlation between ABI and DWU. Wood hydraulic anatomy was more closely related to these indicators of plant performance than wood density. According to the SEM, the common effect of average tree size and sap flux density on the average stem increment and water use of a species was sufficient to fully explain the observed correlation between these variables. Notably, after controlling for average size, only a relatively small indirect effect of wood properties on stem increment and water use remained that was mediated by sap flux density, which was significantly higher for species with lighter and hydraulically more efficient wood. We conclude that wood hydraulic traits are mechanistically linked to water use and productivity via their influence on sap flow, but large parts of these commonly observed positive relationships can be attributed to confounding size effects.

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