scholarly journals Modelling temporal variability of in-situ soil water and vegetation isotopes reveals ecohydrological couplings in a willow plot

2021 ◽  
Author(s):  
Aaron Smith ◽  
Doerthe Tetzlaff ◽  
Jessica Landgraf ◽  
Maren Dubbert ◽  
Chris Soulsby
Keyword(s):  
Soil Water ◽  
Biomass Allocation ◽  
Water Availability ◽  
Summer Precipitation ◽  
Water Sources ◽  
Critical Zone ◽  
Root Uptake ◽  
Water Age ◽  
Transit Times

Abstract. The partitioning of water fluxes in the critical zone is of great interest due to the implications for understanding water cycling and quantifying water availability for various ecosystem services. We used the tracer-aided ecohydrological model EcH2O-iso to evaluate water, energy, water stable isotope, and biomass dynamics at an intensively monitored study plot under two willow trees, a riparian species, in Berlin, Germany. Importantly, we assessed the value of in-situ soil and plant water isotope data to quantify xylem water sources and transit times, with coupled estimates of the temporal dynamics and ages of soil and root-uptake water. The willows showed high evapotranspiration water use, with limited percolation of summer precipitation to deeper soil layers due to the dominance of shallow root-uptake (> 80 % in the upper 10 cm). Lower evapotranspiration under grass resulted in higher soil moisture storage, greater soil evaporation and more percolation of soil water. Biomass allocation was predominantly foliage growth (57 % in grass and 78 % in willow). Shallow soil water age under grass was similar to under willows (15–17 days). Considering potential xylem transit times showed a large improvement in the model's capability to estimate xylem isotopic composition and water age, and revealed the high value of in-situ data within modelling. Root-uptake was predominately derived from summer precipitation events (56 %) and had an average age of 35 days, with xylem transport times taking at least 6.2–8.1 days. By evaluating water partitioning, energy and isotope mass-balance, along with biomass allocation, the model revealed multifaceted capabilities for assessing water cycling within the critical zone at high temporal resolution, including xylem water sources and transport, which are all necessary for short and long-term assessment of water availability for plant growth.

scholarly journals Temporal dynamics of tree xylem water isotopes: In-situ monitoring and modelling

2021 ◽  
Author(s):  
Stefan Seeger ◽  
Markus Weiler
Keyword(s):  
Soil Water ◽  
Temporal Dynamics ◽  
Length Distribution ◽  
In Situ Monitoring ◽  
Water Isotopes ◽  
Stable Water Isotopes ◽  
Root Tips ◽  
Water Age ◽  
Isotopic Signatures

Abstract. We developed a setup for a fully automated, high frequency in-situ monitoring system of the stable water isotopes Deuterium and 18O in soil water and tree xylem. The setup was tested for 12 weeks within an isotopic labelling experiment during a large artificial sprinkling experiment including three mature European beech (Fagus sylvatica) trees. Our setup allowed for one measurement every 12–20 minutes, enabling us to obtain about seven measurements per day for each of our 15 in-situ probes in the soil and tree xylem. While the labelling induced an abrupt step pulse in the soil water isotopic signature, it took seven to ten days until the isotopic signatures at the trees' stem bases reached their peak label concentrations and it took about 14 days until the isotopic signatures at 8 m stem height levelled off around the same values. During the experiment, we observed the effects of several rain events and dry periods on the xylem water isotopic signatures, which fluctuated between the measured isotopic signatures observed in the upper and lower soil horizons. In order to explain our observations, we combined an already existing root water uptake (RWU) model with a newly developed approach to simulate the propagation of isotopic signatures from the root tips to the stem base and further up along the stem. The key to a proper simulation of the observed short term dynamics of xylem water isotopes, was accounting for sap flow velocities and the flow path length distribution within the root and stem xylem. Our modelling framework allowed us to identify parameter values that relate to root depth, horizontal root distribution and wilting point. The insights gained from this study can help to improve the representation of stable water isotopes in trees within ecohydrological models and the prediction of transit time distribution and water age of transpiration fluxes.

scholarly journals Evaluation of the ERS Scatterometer-Derived Soil Water Index to Monitor Water Availability and Precipitation Distribution at Three Different Scales in China

2008 ◽  
Vol 9 (3) ◽  
pp. 549-562 ◽  
Author(s):  
Deming Zhao ◽  
Claudia Kuenzer ◽  
Congbin Fu ◽  
Wolfgang Wagner
Keyword(s):  
Soil Moisture ◽  
Soil Water ◽  
Water Availability ◽  
Local Area ◽  
Monthly Precipitation ◽  
Precipitation Data ◽  
Precipitation Distribution ◽  
Water Index ◽  
Global Precipitation Climatology Centre

Abstract In this paper, the capability of the European Remote Sensing Satellite (ERS) scatterometer-derived soil water index (SWI) data to disclose water availability and precipitation distribution in China is investigated. Monthly averaged SWI data for the years 1992–2000 are analyzed to evaluate the use of the SWI as an index to monitor water availability and water stress at three different scales in China and to investigate if it reflects general precipitation distribution characteristics in China. Monthly averaged in situ relative soil moisture from Chinese meteorological gauge stations, as well as monthly precipitation data from the Global Precipitation Climatology Centre (GPCC), are employed to perform comparisons with SWI on local, regional, and countrywide scales. First, since soil moisture is highly affected by the precipitation, area-averaged SWI is compared with in situ relative soil moisture and GPCC precipitation data in one local area. Second, area-averaged SWI and GPCC precipitation data are used to perform comparisons in three regions of China. Finally, the relationship between SWI and GPCC precipitation data in China is investigated on a countrywide scale. Such multiscale analyses with SWI data have not been performed before, and SWI has never been investigated in detail for China. ERS-derived SWI data in China for the years 1992–2000 are evaluated to be a good indicator for water availability on local, regional, and countrywide scales. SWI and SWI anomaly data correlate well with precipitation and in situ soil moisture data. SWI has furthermore been demonstrated to reflect extreme events such as droughts and floods in China, occurring during the investigated period between 1992 and 2000. Additionally, the SWI allows one to monitor increasing soil moisture resulting from snowmelt, which cannot be deduced from precipitation data. The freely available 15-yr (1992–2007) time series SWI data are thus a valuable tool to overcome the scarcity of in situ soil moisture observations, which are usually not available on regional and countrywide scales.

Changes in soil water availability and air-temperature impact biomass allocation and C:N:P stoichiometry in different organs of Stylosanthes capitata Vogel

2021 ◽  
Vol 278 ◽  
pp. 111540
Author(s):  
Dilier Olivera Viciedo ◽  
Renato de Mello Prado ◽  
Carlos Alberto Martinez ◽  
Eduardo Habermann ◽  
Marisa de Cássia Piccolo ◽  
...  
Keyword(s):  
Soil Water ◽  
Air Temperature ◽  
Biomass Allocation ◽  
Water Availability ◽  
Soil Water Availability ◽  
C:N:P Stoichiometry ◽  
Temperature Impact

scholarly journals Temporal dynamics of tree xylem water isotopes: in situ monitoring and modeling

2021 ◽  
Vol 18 (15) ◽  
pp. 4603-4627
Author(s):  
Stefan Seeger ◽  
Markus Weiler
Keyword(s):  
Soil Water ◽  
Temporal Dynamics ◽  
Length Distribution ◽  
In Situ Monitoring ◽  
Water Isotopes ◽  
Root Tips ◽  
Water Age ◽  
Modeling Framework ◽  
Isotopic Signatures

Abstract. We developed a setup for a fully automated, high-frequency in situ monitoring system of the stable water isotope deuterium and 18O in soil water and tree xylem. The setup was tested for 12 weeks within an isotopic labeling experiment during a large artificial sprinkling experiment including three mature European beech (Fagus sylvatica) trees. Our setup allowed for one measurement every 12–20 min, enabling us to obtain about seven measurements per day for each of our 15 in situ probes in the soil and tree xylem. While the labeling induced an abrupt step pulse in the soil water isotopic signature, it took 7 to 10 d until the isotopic signatures at the trees' stem bases reached their peak label concentrations and it took about 14 d until the isotopic signatures at 8 m stem height leveled off around the same values. During the experiment, we observed the effects of several rain events and dry periods on the xylem water isotopic signatures, which fluctuated between the measured isotopic signatures observed in the upper and lower soil horizons. In order to explain our observations, we combined an already existing root water uptake (RWU) model with a newly developed approach to simulate the propagation of isotopic signatures from the root tips to the stem base and further up along the stem. The key to a proper simulation of the observed short-term dynamics of xylem water isotopes was accounting for sap flow velocities and the flow path length distribution within the root and stem xylem. Our modeling framework allowed us to identify parameter values that relate to root depth, horizontal root distribution and wilting point. The insights gained from this study can help to improve the representation of stable water isotopes in trees within ecohydrological models and the prediction of transit time distribution and water age of transpiration fluxes.

scholarly journals Water as a critical zone currency: linking water storage and age to root uptake and biogeochemical transport

2020 ◽  
Author(s):  
Sylvain Kuppel ◽  
Isabelle Braud ◽  
Yves Goddéris ◽  
Sekhar Muddu ◽  
Jean Riotte ◽  
...  
Keyword(s):  
Chemical Weathering ◽  
Spatial Organization ◽  
Spatial Scales ◽  
Water Storage ◽  
Critical Zone ◽  
Root Uptake ◽  
Time Varying ◽  
Peninsular India ◽  
Transit Times ◽  
Flow Pathways

<p><span>Efforts to grasp hydrological functioning in landscapes have gradually been evolving from inferring </span><span><em>when</em></span><span> water output fluxes respond to precipitation and energy inputs in catchments, towards tracking down </span><span><em>which water</em></span><span> is present in the different flow pathways of the critical zone (CZ). In the CZ where almost all terrestrial life developed, quantifying water storage and age (residence times in stores and transit times in fluxes) is key to the understanding of how water is <em>i)</em> available to supply root uptake, <em>ii)</em> in interaction with regolith minerals and biota, and <em>iii)</em> a medium for solute transport. We propose an approach to characterize the dynamics and non-linearities of CZ functioning first by mapping time-varying transit times of water </span><span>exiting as plant transpiration as well as</span><span> soil evaporation and stream discharge, against the corresponding water storage states. This picture is then extended by assessing the resulting relationships between hydrological states and patterns of nutrient concentration in, and export out of, the critical zone. This analysis considers several spatial scales, from the hillslope to the whole catchment. To this end, we use simulations from a cascade of spatially-distributed numerical tools: a process-based ecohydrological model –</span><span> accounting for the coupling between energy balance, critical zone hydrology and vegetation dynamics</span><span>, and a modular chemical weathering model – simulating dissolution/precipitation rates of mineral phases based on kinetics laws. We particularly focus on the long-term experimental tropical catchment of Mule Hole in Peninsular India (part of both </span><span>the </span><span>Indian Kabini CZ </span><span>observatory </span><span>and </span><span>the </span><span>French CZ </span><span>observatory</span><span> network OZCAR), with a highly seasonal hydroclimate and deep unsaturated profile, and where extensive hydrometric and chemical datasets are available for model calibration and evaluation. We discuss the </span><span>interplay between distinctively mobilized critical zone compartments for each output flux,</span> <span>and</span><span> the</span><span> time-varying spatial organization of flow pathways. </span></p>

scholarly journals Publisher Correction: Origin and hydrodynamics of xylem sap in tree stems, and relationship to root uptake of soil water

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yasunori Mahara ◽  
Tomoko Ohta ◽  
Jyunichi Ohshima ◽  
Kazuya Iizuka
Keyword(s):  
Soil Water ◽  
Xylem Sap ◽  
Root Uptake

scholarly journals Characterizing Growing Season Length of Subtropical Coniferous Forests with a Phenological Model

Forests ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 95
Author(s):  
Yuan Gong ◽  
Christina L. Staudhammer ◽  
Susanne Wiesner ◽  
Gregory Starr ◽  
Yinlong Zhang
Keyword(s):  
Climate Change ◽  
Soil Water ◽  
Prescribed Fire ◽  
Water Availability ◽  
Longleaf Pine ◽  
Growing Season ◽  
Soil Water Availability ◽  
Future Climate Change ◽  
Short Term ◽  
Phenological Model

Understanding plant phenological change is of great concern in the context of global climate change. Phenological models can aid in understanding and predicting growing season changes and can be parameterized with gross primary production (GPP) estimated using the eddy covariance (EC) technique. This study used nine years of EC-derived GPP data from three mature subtropical longleaf pine forests in the southeastern United States with differing soil water holding capacity in combination with site-specific micrometeorological data to parameterize a photosynthesis-based phenological model. We evaluated how weather conditions and prescribed fire led to variation in the ecosystem phenological processes. The results suggest that soil water availability had an effect on phenology, and greater soil water availability was associated with a longer growing season (LOS). We also observed that prescribed fire, a common forest management activity in the region, had a limited impact on phenological processes. Dormant season fire had no significant effect on phenological processes by site, but we observed differences in the start of the growing season (SOS) between fire and non-fire years. Fire delayed SOS by 10 d ± 5 d (SE), and this effect was greater with higher soil water availability, extending SOS by 18 d on average. Fire was also associated with increased sensitivity of spring phenology to radiation and air temperature. We found that interannual climate change and periodic weather anomalies (flood, short-term drought, and long-term drought), controlled annual ecosystem phenological processes more than prescribed fire. When water availability increased following short-term summer drought, the growing season was extended. With future climate change, subtropical areas of the Southeastern US are expected to experience more frequent short-term droughts, which could shorten the region’s growing season and lead to a reduction in the longleaf pine ecosystem’s carbon sequestration capacity.

scholarly journals Contrasting Water Use Strategies of Tamarix ramosissima in Different Habitats in the Northwest of Loess Plateau, China

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2791
Author(s):  
Pengyan Su ◽  
Mingjun Zhang ◽  
Deye Qu ◽  
Jiaxin Wang ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Loess Plateau ◽  
Meteoric Water ◽  
Water Source ◽  
Water Sources ◽  
Tamarix Ramosissima ◽  
Water Line ◽  
Meteoric Water Line ◽  
Utilization Ratio

As a species for ecological restoration in northern China, Tamarix ramosissima plays an important role in river protection, flood control, regional climate regulation, and landscape construction with vegetation. Two sampling sites were selected in the hillside and floodplain habitats along the Lanzhou City, and the xylems of T. ramosissima and potential water sources were collected, respectively. The Bayesian mixture model (MixSIAR) and soil water excess (SW-excess) were applied to analyze the relationship on different water pools and the utilization ratios of T. ramosissima to potential water sources in two habitats. The results showed that the slope and intercept of local meteoric water line (LMWL) in two habitats were smaller compared with the global meteoric water line (GMWL), which indicated the existence of drier climate and strong evaporation in the study area, especially in the hillside habitat. Except for the three months in hillside, the SW-excess of T. ramosissima were negative, which indicated that xylems of T. ramosissima are more depleted in δ2H than the soil water line. In growing seasons, the main water source in hillside habitat was deep soil water (80~150 cm) and the utilization ratio was 63 ± 17% for T. ramosissima, while the main water source in floodplain habitat was shallow soil water (0~30 cm), with a utilization ratio of 42.6 ± 19.2%, and the water sources were different in diverse months. T. ramosissima has a certain adaptation mechanism and water-use strategies in two habitats, and also an altered water uptake pattern in acquiring the more stable water. This study will provide a theoretical basis for plant water management in ecological environment protection in the Loess Plateau.

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