scholarly journals Robust Estimation of Absorbing Root Surface Distributions From Xylem Water Isotope Compositions With an Inverse Plant Hydraulic Model

2021 ◽  
Vol 4 ◽  
Author(s):  
Hannes P. T. De Deurwaerder ◽  
Marco D. Visser ◽  
Félicien Meunier ◽  
Matteo Detto ◽  
Pedro Hervé-Fernández ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Soil Water ◽  
Robust Estimation ◽  
Inverse Modeling ◽  
Sap Flow ◽  
Soil Water Potential ◽  
Modeling Method ◽  
Flow Monitoring ◽  
Root Surfaces ◽  
Water Isotope

The vertical distribution of absorbing roots is one of the most influential plant traits determining plant strategy to access below ground resources. Yet little is known of natural variability in root distribution since collecting field data is challenging and labor-intensive. Studying stable water isotope compositions in plants could offer a cost-effective and practical solution to estimate the absorbing root surfaces distribution. However, such an approach requires developing realistic inverse modeling techniques that enable robust estimation of rooting distributions and associated uncertainty from xylem water isotopic composition observations. This study introduces an inverse modeling method that supports the assessment of the root allocation parameter (β) that defines the exponential vertical decay of a plants’ absorbing root surfaces distribution with soil depth. The method requires measurements obtained from xylem and soil water isotope composition, soil water potentials, and sap flow velocities when plants’ xylem water is sampled at a certain height above the rooting point. In a simulation study, we show that the approach can provide unbiased estimates of β and its associated uncertainty due to measuring errors and unmeasured environmental factors that can impact the xylem water isotopic data. We also recommend improving the accuracy and power of β estimation, highlighting the need for considering accurate soil water potential and sap flow monitoring. Finally, we apply the inverse modeling method to xylem water isotope data of lianas and trees collected in French Guiana. Our work shows that the inverse modeling procedure provides a robust analytical and statistical framework to estimate β. The method accounts for potential bias due to extraction errors and unmeasured environmental factors, which improves the viability of using stable water isotope compositions to estimate the distribution of absorbing root surfaces complementary to the assessment of relative root water uptake profiles.

An assessment of potato sap flow as affected by soil water status, solar radiation and vapour pressure deficit

1999 ◽  
Vol 79 (2) ◽  
pp. 245-253 ◽  
Author(s):  
R. Gordon ◽  
D. M. Brown ◽  
A. Madani ◽  
M. A. Dixon
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Vapour Pressure ◽  
Sap Flow ◽  
Water Status ◽  
Vapour Pressure Deficit ◽  
Potato Cultivars ◽  
Rapid Decline ◽  
Plant Variation ◽  
Flow Monitoring

Water-use of three field-grown potato cultivars (Atlantic, Monona and Norchip) was examined using a commercially available sap flow monitoring system over three consecutive growing seasons. The objectives of the investigation were to utilize the sap flow system to assess the water use of three field-grown potato cultivars. This included an assessment of the relationship between environmental conditions, water status and measured sap flow including the plant-to-plant variation in sap flow and an evaluation of relative transpiration in relation to the soil water status.Each cultivar maintained daily sap flow close to the atmospheric potential transpiration until approximately 70% of the available water was depleted. Under conditions where the soil was drier (>70% depleted), Monona potato plants exhibited a more rapid decline in transpiration than Norchip and Atlantic.Hourly sap flow rates were closely related to solar irradiance, especially under well-watered conditions, with no apparent light saturation point. Vapour pressure deficit effects on sap flow were less pronounced, although maximum vapour pressure deficits encountered were only 2 kPa. Key words: Water use, sap flow, transpiration, potato

scholarly journals Diurnal variation in xylem water isotopic signature biases depth of root-water uptake estimates

2019 ◽  
Author(s):  
Hannes De Deurwaerder ◽  
Marco D. Visser ◽  
Matteo Detto ◽  
Pascal Boeckx ◽  
Félicien Meunier ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Soil Water ◽  
Water Uptake ◽  
Sap Flow ◽  
Soil Water Potential ◽  
Root Water Uptake ◽  
Isotopic Signature ◽  
Stem Length ◽  
Individual Plant ◽  
List Type

SummaryStable water isotopes are a powerful and widely used tool to derive the depth of root water uptake (RWU) in lignified plants. Uniform xylem water isotopic signature (i-H2O-xyl) along the length of a lignified plant is a central assumption, which has never been properly evaluated.Here we studied the effects of diurnal variation in RWU, sap flow velocity and various other soil and plant parameters on i-H2O-xyl signature within a plant using a mechanistic plant hydraulic model.Our model predicts significant variation in i-H2O-xyl along the full length of an individual plant arising from diurnal RWU fluctuations and vertical soil water heterogeneity. Moreover, significant differences in i-H2O-xyl emerge between individuals with different sap flow velocities. We corroborated our model predictions with field observations from French Guiana and northwestern China. Modelled i-H2O-xyl varied considerably along stem length ranging up to 18.3‰ in δ2H and 2.2‰ in δ18O, largely exceeding the range of measurement error.Our results show clear violation of the fundamental assumption of uniform i-H2O-xyl and occurrence of significant biases when using stable isotopes to assess RWU. As a solution, we propose to include monitoring of sap flow and soil water potential for more robust RWU depth estimates.

Phytophthora cinnamomi: Population Densities in Forest Soils

1977 ◽  
Vol 25 (5) ◽  
pp. 461 ◽  
Author(s):  
G Weste ◽  
P Ruppin
Keyword(s):  
Environmental Factors ◽  
Soil Water ◽  
Phytophthora Cinnamomi ◽  
Soil Water Potential ◽  
Forest Community ◽  
Population Densities ◽  
Sclerophyll Forest ◽  
Soil Temperatures ◽  
Disease Extension ◽  
Pathogen Populations

Population densities of Phytophthora cinnamomi, associated disease and environmental factors were studied concurrently during a 2-year period in three different forest ecosystems. Pathogen populations showed seasonal variation, low values being obtained for winter months associated with soil temperatures less than 10°C. Populations increased with warmer temperatures for spring and summer, but declined during dry periods in late summer or early autumn when the soil water potential was lower than -9 bars, although at that period soil temperatures were favourable. High populations were recorded in autumn, then declined with decrease in soil temperatures during winter. Correlation coefficients indicated a highly significant relationship between pathogen populations and soil temperatures from autumn to early summer, and between soil moisture and pathogen population for summer and autumn, in the Brisbane Ranges independently of site. The same pattern was evident in wetter forests at Narbethong and savannah woodlands at Wilson's Promontory, although results were not significant. Disease was evident wherever the pathogen occurred among susceptible hosts. The savannah woodland, the dry shrubby sclerophyll forest and the wetter sclerophyll forest all contained susceptible dominants; consequently disease was associated with changes in the forest community such as early death of the understorey, later die-back and death of the trees, and an increase in sedges and in bare ground. Symptoms and deaths increased with time from invasion. The severity of disease and its rate of extension, apart from spread by free water, were associated with environmental factors such as shallow soil, poor drainage and low soil water-holding capacity. These were characteristic of the Brisbane Ranges, where destruction of the forest community was severe and the rate of disease extension rapid. In the deep krasnozem at Narbethong and the deep sands of Wilson's Promontory, destruction was confined to the most susceptible hosts, disease extension was continuous but slow, and deaths occurred in a mosaic throughout the infected zone.

scholarly journals How does soil water potential limit the seasonal dynamics of sap flow and circumference changes in European beech?

2014 ◽  
Vol 60 (1) ◽  
pp. 19-30 ◽  
Author(s):  
Zuzana Sitková ◽  
Paulína Nalevanková ◽  
Katarína Střelcová ◽  
Peter Fleischer Jr. ◽  
Marek Ježík ◽  
...  
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Sap Flow ◽  
Soil Water Potential ◽  
European Beech ◽  
Weather Conditions ◽  
Growing Season ◽  
Control Group ◽  
Average Volume ◽  
Beech Stand

Abstract We focus on the analysis of sap flow and stem circumference changes in European beech (Fagus sylvatica, L.) in relation to available soil water and weather conditions during the growing seasons 2012 and 2013. The objective was to examine how soil water potential affects growth and transpiration of a mature beech stand situated at the lower distributional limit of beech in Slovakia. To be able to evaluate beech response to soil water shortage, we irrigated a group of 6 trees during the period of pronounced drought, while the control group of other 6 trees remained exposed to actual weather conditions. Mean air temperatures of both seasons were considerably above the long-term average and the temporal pattern of precipitation differed between the years. During the whole growing season 2012, beech samples transpired an average volume of 6.9 m3 of water in the control and 7.7 m3 in the irrigated group. A slightly higher average volume was found in the growing season 2013 under both treatments (7.7 m3 in control and 10.5 m3 in irrigated trees). In the drought period 2012, when the irrigation experiment was commenced, the sap flow in the control group was reduced by 30% as compared with the irrigated group. In 2013, a 38.1% difference in sap flow was observed between the groups. Sap flow in the non-irrigated trees decreased with reducing soil moisture, and ceased at soil water potential -0.6 MPa. In both treatments and years, we found significant correlations between hourly sap flow and investigated weather variables. A reduction in stem circumferences of the control trees, which was observed during stem shrinkage phase, was up to 19% in 2012 and 10% in 2013. We conclude that stem circumference shrinkage during the peak of soil drought was induced by the cessation in the sap flow process.

Effect of Soil Water Potential of Two Soils on Soybean Emergence 1

1979 ◽  
Vol 71 (6) ◽  
pp. 980-982 ◽  
Author(s):  
L. G. Heatherly ◽  
W. J. Russell
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential

scholarly journals A Data-Driven Method for the Temporal Estimation of Soil Water Potential and Its Application for Shallow Landslides Prediction

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1208
Author(s):  
Massimiliano Bordoni ◽  
Fabrizio Inzaghi ◽  
Valerio Vivaldi ◽  
Roberto Valentino ◽  
Marco Bittelli ◽  
...  
Keyword(s):  
Machine Learning ◽  
Water Potential ◽  
Soil Water ◽  
Temporal Trends ◽  
Soil Water Potential ◽  
Shallow Landslides ◽  
Water Dynamics ◽  
Data Driven ◽  
Machine Learning Techniques ◽  
Physically Based

Soil water potential is a key factor to study water dynamics in soil and for estimating the occurrence of natural hazards, as landslides. This parameter can be measured in field or estimated through physically-based models, limited by the availability of effective input soil properties and preliminary calibrations. Data-driven models, based on machine learning techniques, could overcome these gaps. The aim of this paper is then to develop an innovative machine learning methodology to assess soil water potential trends and to implement them in models to predict shallow landslides. Monitoring data since 2012 from test-sites slopes in Oltrepò Pavese (northern Italy) were used to build the models. Within the tested techniques, Random Forest models allowed an outstanding reconstruction of measured soil water potential temporal trends. Each model is sensitive to meteorological and hydrological characteristics according to soil depths and features. Reliability of the proposed models was confirmed by correct estimation of days when shallow landslides were triggered in the study areas in December 2020, after implementing the modeled trends on a slope stability model, and by the correct choice of physically-based rainfall thresholds. These results confirm the potential application of the developed methodology to estimate hydrological scenarios that could be used for decision-making purposes.

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