Functional Differences in Soil Water Pools: a New Perspective on Plant Water Use in Water-Limited Ecosystems

2008 ◽  
pp. 397-422 ◽  
Author(s):  
Ronald J. Ryel ◽  
Carolyn Y. Ivans ◽  
Michael S. Peek ◽  
A. Joshua Leffler
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Plant Water ◽  
Functional Differences ◽  
Plant Water Use ◽  
New Perspective

scholarly journals EcH<sub>2</sub>O-iso 1.0: water isotopes and age tracking in a process-based, distributed ecohydrological model

2018 ◽  
Vol 11 (7) ◽  
pp. 3045-3069 ◽  
Author(s):  
Sylvain Kuppel ◽  
Doerthe Tetzlaff ◽  
Marco P. Maneta ◽  
Chris Soulsby
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Stream Water ◽  
Plant Water ◽  
Model Data ◽  
Energy Propagation ◽  
Isotopic Tracers ◽  
Landscape Characteristics ◽  
Plant Water Use ◽  
Ecohydrological Model

Abstract. We introduce EcH2O-iso, a new development of the physically based, fully distributed ecohydrological model EcH2O where the tracking of water isotopic tracers (2H and 18O) and age has been incorporated. EcH2O-iso is evaluated at a montane, low-energy experimental catchment in northern Scotland using 16 independent isotope time series from various landscape positions and compartments, encompassing soil water, groundwater, stream water, and plant xylem. The simulation results show consistent isotopic ranges and temporal variability (seasonal and higher frequency) across the soil profile at most sites (especially on hillslopes), broad model–data agreement in heather xylem, and consistent deuterium dynamics in stream water and in groundwater. Since EcH2O-iso was calibrated only using hydrometric and energy flux datasets, tracking water composition provides a truly independent validation of the physical basis of the model for successfully capturing catchment hydrological functioning, both in terms of the celerity in energy propagation shaping the hydrological response (e.g. runoff generation under prevailing hydraulic gradients) and flow velocities of water molecules (e.g. in consistent tracer concentrations at given locations and times). Additionally, we show that the spatially distributed formulation of EcH2O-iso has the potential to quantitatively link water stores and fluxes with spatiotemporal patterns of isotope ratios and water ages. However, our case study also highlights model–data discrepancies in some compartments, such as an over-dampened variability in groundwater and stream water lc-excess, and over-fractionated riparian topsoils. The adopted minimalistic framework, without site-specific parameterisation of isotopes and age tracking, allows us to learn from these mismatches in further model development and benchmarking needs, while taking into account the idiosyncracies of our study catchment. Notably, we suggest that more advanced conceptualisation of soil water mixing and of plant water use would be needed to reproduce some of the observed patterns. Balancing the need for basic hypothesis testing with that of improved simulations of catchment dynamics for a range of applications (e.g. plant water use under changing environmental conditions, water quality issues, and calibration-derived estimates of landscape characteristics), further work could also benefit from including isotope-based calibration.

Drivers of spatial and temporal soil water isotope variability in a sub-arctic catchment

2021 ◽  
Author(s):  
Filip Muhic ◽  
Pertti Ala-Aho ◽  
Hannu Marttila ◽  
Björn Klöve
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Isotope Composition ◽  
Growing Season ◽  
Snow Accumulation ◽  
Plant Water ◽  
Catchment Scale ◽  
Data Set ◽  
Plant Water Use ◽  
Water Isotope

&lt;p&gt;Research on ecohydrological separation and plant water use have been increasing in the last few years, and various studies indicate that trees can use winter precipitation as a dominant water source during the growing season. Such studies are of great importance to northern regions, where soil water recharge timing is predicted to be significantly altered due to climate change. In order to assess plant water use in sub-arctic environment, it is necessary to understand how soil water pools under different land covers evolve throughout the year and how cryogenic processes alter the isotope input signal. This field study was conducted from May 2019 to June 2020 in Pallas catchment, located in sub-arctic conditions in Finnish Lapland. Soil cores up to 1 meter depth with 5&amp;#160;cm increments and xylem water of dominant tree species were collected in 4 locations, ranging from forest to shrubland/forest transitional area, and to forested peatland. All locations are positioned on a snow survey, in the vicinity of previously installed groundwater wells and snow lysimeters, and within 2 kilometers of rain gauge. Additional spatial samples of topsoil and xylem water were collected throughout the catchment during 2019 growing season. Relative proportions of tree source water were calculated by Bayesian mixing model MixSIAR. We produce new data set that displays plot and catchment scale soil water heterogeneities in a snow dominated environment, and examine: i) How soil properties affect isotopic composition of soil water?; ii) What is the effect of rising groundwater level on soil water isotope composition?; and iii) How snowpack thickness and melt timing modify soil water isotope patterns? We analyze if these varying pools of water are reflected in tree xylem water. Soil water isotope dynamics under deep snowpack, during and after snowmelt reveal how snow accumulation and melt timing and magnitude influence plant available water for growing season.&lt;/p&gt;

Hydraulic and chemical signalling in the regulation of stomatal conductance and plant water use in field grapevines growing under deficit irrigation

2008 ◽  
Vol 35 (7) ◽  
pp. 565 ◽  
Author(s):  
M. Lucília Rodrigues ◽  
Tiago P. Santos ◽  
Ana P. Rodrigues ◽  
Claudia R. de Souza ◽  
Carlos M. Lopes ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Water Availability ◽  
Dominant Role ◽  
Xylem Sap ◽  
Soil Water Availability ◽  
Vitis Vinifera L ◽  
Plant Water ◽  
Chemical Signalling ◽  
Plant Water Use

Effects of irrigation strategies on stomata and plant water use were studied in field-grown grapevines (Vitis vinifera L.). We assessed the importance of root-derived chemical signals vs. hydraulic signalling in stomatal regulation. The experiment included two treatments with the same water added to the soil (50% ETc) applied either to the whole root system (DI) or to half of the roots, alternating irrigation side every 15 days (PRD). Well-watered plants (FI) (100% ETc) and non-irrigated grapevines (NI) were also studied. Partial stomata closure occurred in both PRD and DI plants. [ABA] of xylem sap remained constant during the day and was maintained throughout the season, with higher values in NI plants. Xylem sap pH was not affected by soil water availability. A positive correlation between ψpd and maximum g s was found, indicating that grapevine stomata strongly respond to plant water status. In contrast, ABA did not explain stomatal control at veraison. At mid-ripening g s was significantly correlated with ABA, apparently interacting with the rise in xylem sap pH. Therefore, our data suggest that hydraulic feedback and feed-forward root-to-shoot chemical signalling mechanisms might be involved in the control of stomata in response to decreased soil water availability, hydraulic signals playing the dominant role.

Parsimonious representation of plant water use strategies via non-dimensional parameter groups

2021 ◽  
Author(s):  
Maoya Bassiouni ◽  
Stefano Manzoni ◽  
Giulia Vico
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Plant Traits ◽  
Water Flux ◽  
Climatic Conditions ◽  
Model Parameters ◽  
Plant Water ◽  
Dimensional Parameter ◽  
Water Limitation ◽  
Plant Water Use

&lt;p&gt;Process-based models are needed to improve estimates of water and carbon cycles in variable climatic conditions. Yet, their utility is often limited by our inability to directly measure plant stomatal and hydraulic traits at scales suitable to quantify characteristics of whole ecosystems. Inferring such parameters from ecosystem-scale data with parsimonious models offers an avenue to address this limitation. To this aim, we use a simple representation of the water flux through the soil-plant-atmosphere continuum (SPAC) and derive a parameterization of Feddes-type soil water-limitation constraints on transpiration (expressed via a soil moisture dependent function &amp;#946;). This parameterization explicitly accounts for community-effective plant eco-physiological traits as encoded in the SPAC model parameters. We express analytically the fractional loss of conductivity in well-watered conditions and the soil saturation thresholds at which transpiration is down-regulated from its well-watered rate and at which transpiration ceases, as a function of non-dimensional parameter groups. These non-dimensional groups combine plant stomatal and hydraulic traits, soil texture and climate. We implement the theoretical &amp;#946; function into a soil water balance and infer distributions of plant traits which best-match FLUXNET observations in a range of biomes. Finally, we analyze the resulting non-dimensional groups to explore patterns in plant water use strategies. Our results indicate that non-dimensional groups reflect combinations of plant traits which are adapted to growing season environmental conditions and these groups may be more meaningful model parameters than individual traits at ecosystem scales. Additionally, using non-dimensional groups instead of focusing on individual parameters reduces risks of equifinality and provides future opportunities to exploit satellite data to quantify robust ecosystem-scale parameters. This analysis provides a parsimonious and functionally accurate alternative to account for ecosystem hydraulic controls and feedbacks and can help overcome limitations of commonly used empirical water-limitation constraints.&lt;/p&gt;

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