Maren Dubbert

• Dr. rer. nat.
• Working Group Head at Leibniz Centre for Agricultural Landscape Research

In recent years, research interest in plant water uptake strategies has significantly grown in many disciplines such as hydrology, plant ecology and ecophysiology. Quantitative modelling approaches to estimate plant water uptake and the spatio-temporal dynamics significantly advanced from different disciplines across scales. Despite this progress,...

The isotopic composition of xylem water (δX ) is of considerable interest for plant source water studies. In-situ monitored isotopic composition of transpired water (δT ) could provide a non-destructive proxy for δX -values. Using flow-through leaf chambers, we monitored 2-hourly δT -dynamics in two tropical plant species, one canopy-forming tree a...

Tracing and quantifying water fluxes in the hydrological cycle is crucial for understanding the current state of ecohydrological systems and their vulnerability to environmental change. Especially the interface between ecosystems and the atmosphere that is strongly mediated by plants is important to meaningfully describe ecohydrological system func...

In the light of the ongoing global climate crisis and the related increases in extreme hydrological events, it is crucial to assess ecosystem resilience and – in agricultural systems – to ensure sustainable management and food security. For this purpose, a comprehensive understanding of ecosystem water cycle budgets and spatiotemporal dynamics is i...

This study investigated the influence of vegetation and microforms on methane (CH4) balances of a rewetted bog in north-west Germany. The two study sites are in close proximity on the same former peat extraction area, one dominated by Sphagnum-mosses and the other one by a dense Betula pubescens stand with a high Eriophorum vaginatum cover. The con...

The spatial variation of soil water isotopes (SWI)—representing the baseline for investigating root water uptake (RWU) depths with water stable isotope techniques—has rarely been investigated. Here, we use spatial SWI depth profile sampling in combination with unmanned aerial vehicle (UAV) based land surface temperature estimates and vegetation ind...

Introduction Increasing greenhouse gas emissions pose a strong threat due to accelerating global warming. N2O emissions are highly important in this regard as N2O is a very powerful greenhouse gas. Agriculture is the main human-induced source for N2O emissions, contributing roughly 60% to total N2O emissions. Soil amorphous silica (ASi) contents ar...

Rewetted bogs with high water levels (WL) and mire‐specific vegetation are crucial carbon (C) sinks, but their function might be threatened by tree encroachment, a phenomenon widespread in the northern hemisphere that often coincides with low WL. This might impact C cycling both at the ecosystem and microform scale in multiple ways, but so far, dat...

Investigating greenhouse gases (GHGs) and water flux dynamics within the soil–plant–atmosphere interphase is key for understanding ecosystem functioning, as they reflect the ecosystem's responses to environmental changes. Understanding these responses is essential for developing sustainable agricultural systems that can help to adapt to global chal...

Stable isotope ratios of hydrogen (δ2H) and oxygen (δ18O) are crucial for studying ecohydrological dynamics in forests. However, most studies are confined to single sites, resulting in a lack of large-scale isotope data for understanding tree water uptake. Here, we provide a first systematic isotope dataset of soil and stem xylem water collected du...

Increasing greenhouse gas emissions pose a strong threat due to accelerating global warming. N 2 O emissions are highly important in this regard as N 2 O is a very powerful greenhouse gas. Agriculture is the main human-induced source for N 2 O emissions contributing roughly 60% to total N 2 O emissions. Soil amorphous silica (ASi) contents are redu...

Modern agriculture’s goal of improving crop resource acquisition efficiency relies on the intricate relationship between the root system and the soil. Root and rhizosphere traits play a critical role in the efficient use of nutrients and water, especially under dynamic environments. This review emphasizes a holistic perspective, challenging the con...

Water-stable isotopes are commonly used in hydrological and ecological research. Until now, measurements were obtained either by taking a destructive sample in the field (such as a soil or plant sample) and extracting its water in the laboratory, or by directly measuring it in the field using semi-permeable membranes. These methods, however, presen...

Investigating greenhouse gases (GHG) and water flux dynamics within the soil-plant-atmosphere-interphase is a key for understanding ecosystem functioning, as these dynamics reflect the ecosystem's responses to environmental changes. Understanding these responses is hence essential for developing sustainable agriculture systems that can help to adap...

Phosphorus (P) availability severely limits plant growth due to its immobility and inaccessibility in soils. Yet, visualization and measurements of P uptake from different root types or regions in soil are methodologically challenging. Here, we explored the potential of phosphor imaging combined with local injection of radioactive ³³P to quantitati...

Encroachment of vascular plants (VP) in temperate raised bogs, as a consequence of altered hydrological conditions and nutrient input, is widely observed. Effects of such vegetation shift on water and carbon cycles are, however, largely unknown and identification of responsible plant physiological traits is challenging. Process-based modelling offe...

The spatial variation of soil water isotopes (SWI) - representing the baseline for investigating root water uptake (RWU) depths with water stable isotope techniques - has rarely been investigated. Here, we use spatial SWI depth profile sampling in combination with unmanned aerial vehicle (UAV) based land surface temperature estimates and vegetation...

The analysis of the stable isotopic composition of hydrogen and oxygen in water samples from soils and plants can help to identify sources of vegetation water uptake. This approach requires that the heterogeneous nature of plant and soil matrices is carefully accounted for during experimental design, sample collection, water extraction and analyses...

Mitigating the global climate crisis and its consequences, such as more frequent and severe droughts, is one of the major challenges for future agriculture. Therefore, identifying land use systems and management practices that reduce greenhouse gas (GHG) emissions and promote water use efficiency (WUE) is crucial. This, however, requires accurate a...

Climate change is increasing the frequency and severity of short-term (~1 y) drought events—the most common duration of drought—globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in t...

Beneficial and negative effects of species interactions can strongly influence water fluxes in forest ecosystems. However, little is known about how trees dynamically adjust their water use when growing with interspecific neighbours. Therefore, we investigated the interaction effects between Fagus sylvatica (European beech) and Picea abies (Norway...

Using isotopic spike experiments, we investigated the existence and magnitude of soil‐mediated isotopic effects and of the interaction between isotopically distinct soil water pools, both associated in isotopic mismatches between water extracted from soil and soil water taken up by the roots. For this, we applied and compared four established techn...

We monitored stable water isotopes in liquid precipitation and atmospheric water vapour (δ v ) using in situ cavity ring‐down spectroscopy (CRDS) over a 2 month period in an urban green space area in Berlin, Germany. Our aim was to better understand the origins of atmospheric moisture and its link to water partitioning under contrasting urban veget...

Deep rooting is considered a central drought-mitigation trait with vast impact on ecosystem water cycling. Despite its importance, little is known about the overall quantitative water use via deep roots and dynamic shifts of water uptake depths with changing ambient conditions. Knowledge is especially sparse for tropical trees. Therefore, we conduc...

Quantitative knowledge about ecohydrological partitioning across the critical zone in different types of urban green space is important to balance sustainable water needs in cities during future challenges of increasing urbanization and climate warming. We monitored stable water isotopes in liquid precipitation and atmospheric water vapour (δ ) usi...

Urban green spaces are highly valuable in supporting the climate and infrastructure of cities through rainwater retention, evaporative cooling and shading. Investigating the diurnal and seasonal ecohydrological process dynamics in the urban soil-plant-atmosphere continuum is crucial to understand what types of landcover might best balance water red...

Mitigating the global climate crisis and its consequences, such as more frequent and severe droughts, is one of the major challenges for future agriculture. Therefore, identifying land use systems and management practices that reduce greenhouse gas emissions (GHG) and promote water use efficiency (WUE) is crucial. This, however, requires accurate a...

Recent advances in plant hydraulics indicate that the hydraulic behaviour (i.e. the degree of isohydricity) of plants might be more flexible than previously thought. While there is now evidence that seasonal abiotic factors, such as vapour pressure deficit or photosynthetically active photon flux density, can modify the isohydricity in plants, less...

In light of ongoing global climate crisis and related increases in extreme hydrological events, it is increasingly crucial to assess ecosystem resilience and - in agricultural systems - to ensure sustainable management and food security. For that, comprehensive understanding of ecosystem water cycle budgets and spatio-temporal dynamics are indispen...

The cells in tree sapwood form a network of interconnected conduits which enables the transport of water and nutrients from the tree roots to the canopy. Sapwood depth must be assessed when tree water use is estimated from sap flow velocities. However, current approaches to assess sapwood depth are either not applicable universally, or require expe...

Aims We aimed at assessing the influence of above- and below-ground environmental conditions over the performance of Centaurea jacea L., a drought-resistant grassland forb species. Methods Transpiration rate, CO2 assimilation rate, leaf water potential, instantaneous and intrinsic water use efficiency, temperature, relative humidity, vapor pressur...

Understanding of plant hydraulic strategies (i.e. the degree of iso‐/anisohydricity) is crucial to predict the response of plants to changing environmental conditions such as climate‐change induced extreme drought. Several abiotic factors, including evaporative demand, have been shown to seasonally modify the isohydricity of plants. However, the im...

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 use stable water isotopes to help evaluate water, energy, and biomass dynamics at an intensi...

The ecological impacts of climate change encompass significant consequences on the interactions of soil-plant-atmosphere-continuum and flux dynamics and will thus affect forest ecosystems. Much work needs to be done to understand the distribution of ecosystem specific flow pathways and the characteristic timescales of water movement. Understanding...

Root water uptake (RWU) is an important critical zone process, as plants can tap various water sources and transpire these back into the atmosphere. However, knowledge about the spatial and temporal dynamics of RWU and associated water sources at both high temporal resolution (e.g. daily) and over longer time periods (e.g. seasonal) is still limite...

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 monitor...

Root water uptake is an important critical zone process, as plants can tap various water sources and transpire these back into the atmosphere. However, knowledge about the spatial and temporal dynamics of root water uptake and associated water sources at both high temporal resolution (e.g. daily) and over longer time periods (e.g. seasonal) is stil...

Recent studies have highlighted the importance of understanding ecohydrological drought feedbacks to secure water resources under a changing climate and increasing anthropogenic impacts. In this study, we monitored and modelled feedbacks in the soil-plant-atmosphere continuum to the European drought summer 2018 and the following two years. The phys...

Disentangling ecosystem evapotranspiration (ET) into evaporation (E) and transpiration (T) is of high relevance for a wide range of applications, from land surface modelling to policymaking. Identifying and analysing the determinants of the ratio of T to ET (T/ET) for various land covers and uses, especially in view of climate change with an increa...

Knowledge of plant hydraulic strategies (isohydric vs anisohydric) is crucial to predict the response of plants to changing environmental conditions, such as climate-change induced extreme drought. Several abiotic factors, such as evaporative demand, have been shown to seasonally modify the isohydricity of plants, however, the impact of biotic fact...

Droughts can strongly affect grassland productivity and biodiversity, but responses differ widely. Nutrient availability may be a critical factor explaining this variation, but is often ignored in analyses of drought responses. Here, we used a standardized nutrient addition experiment covering 10 European grasslands to test if full‐factorial NPK‐ad...

• Nitrogen (N) loading and extreme drought were found to strongly alter biomass production, species composition, carbon and water fluxes of temperate grasslands. Such changes at the community level are often attributed to species and functional group‐specific responses in phenology and/or physiology. • In a multifactorial field experiment, we studi...

Sap flow measurements are essential for estimating whole plant- and ecosystem water use. Yet, several challenges and pitfalls exist in the application and analysis of sap flow data, such as the determination of zero-flow (ΔTmax). Here, we used different methods to estimate ΔTmax and their effect on the determination of sap flow of Quercus suber L....

While water stable isotopes are often depicted as 'powerful' tools for tackling our deficit of understanding of given ecohydrological processes, amongst which the partitioning of evapotranspiration (ET) into soil evaporation and plant transpiration (T), the methods utilizing these isotopes are still based on destructive sampling and retrospective a...

About 500 My ago, the major challenge faced by the first terrestrial plant was the acquisition of water resources. Nowadays, water availability is still one of the main environmental factors shaping the evolution of terrestrial plants. Hence, the study of the ability of different plant species to extract water from the soil and deliver it to the ca...

The number of ecohydrological studies involving water stable isotope measurements has been increasing steadily due to technological (e.g., field-deployable laser spectroscopy and cheaper instruments) and methodological (i.e., tracer approaches or improvements in root water uptake models) advances in recent years. This enables researchers from a bro...

Tropical rain forests are greatly dependent on water supply and are highly efficient in water cycling. Soil infiltration rates as well as tree transpiration rates are high in these often seasonally dry ecosystems. Both deforestation and climate change have been shown to cause drought stress in tropical forests, the former through the increase of ru...

Forest water use has been difficult to quantify. One promising approach is to measure the isotopic composition of plant water, e.g., the transpired water vapor or xylem water. Because different water sources, e.g., groundwater versus shallow soil water, often show different isotopic signatures, isotopes can be used to investigate the depths from wh...

Ecohydrological isotope based field research is often constrained by a lack of temporally explicit soil water data, usually related to the choice of destructive sampling in the field and subsequent analysis in the laboratory. New techniques based on gas permeable membranes allow to sample soil water vapor in situ and infer soil liquid water isotopi...

In the present study we investigated water use strategies of mature stands of Fagus sylvatica (European Beech) with and without co-cultivation of Abies alba (Silver fir) during a summer drought and subsequent rewetting through simulated heavy precipitation in a temperate forest in south-west Germany. We used a combination of sap flow analysis, wate...

Root water uptake is a key ecohydrological process for which a physically based understanding has been developed in the past decades. However, due to methodological constraints, knowledge gaps remain about the plastic response of whole plant root systems to a rapidly changing environment. We designed a laboratory system for nondestructive monitorin...

Abstract. The number of ecohydrological studies involving water stable isotopes has been increasing steadily due to technological (i.e. field deployable laser spectroscopy and cheaper instruments) and methodological (i.e. tracer approaches or improvements in root water uptake models) advances in recent years. This enables researchers from a broad s...

Two important threats to the sustainable functioning of seminatural grasslands in temperate zones are (1) nutrient loading due to agricultural fertilization and pollution, and (2) the increase of extreme drought events due to climate change. These threats may cause substantial shifts in species diversity and abundance and considerably affect the ca...

The time that water takes to travel through the terrestrial hydrological cycle and the critical zone is of great interest in Earth system sciences with broad implications for water quality and quantity. Most water age studies to date have focused on individual compartments (or subdisciplines) of the hydrological cycle such as the unsaturated or sat...

In situ methods enabling high-resolution measurements of water isotopes in the tree xylem have already been tested but are not yet widely applied. However, such methods would be tremendously helpful in understanding water uptake in plants and related research questions (e.g. uptake depths, non-steady-state of transpiration, impact on groundwater re...

In this study, we installed a prior tested sampling technique based on polypropylene tubing that enables continuous in situ monitoring of the isotopic composition of soil pore water vapor in a grassland in Southern Germany. We set up rainout shelters to induce water limited conditions and applied two artificial isotopically labeled rain pulses, eac...

• Successful alien plant invasion is influenced by both climate change and plant–plant interactions. We estimate the single and interactive effects of competition and extreme weather events on the performance of the global legume invader Lupinus polyphyllus (Lindl.). • In three experimental studies we assessed (i) the stress tolerance of seedling a...

The ‘two‐water‐worlds’ hypothesis is based on stable isotope differences in stream, soil and xylem waters in dual isotope space. It postulates no connectivity between bound and mobile soil waters, and preferential plant water uptake of bound soil water sources. We tested the pool‐weighted impact of isotopically distinct water pools for hydrological...

The time water takes to travel through the hydrological cycle is of great interest in earth system sciences because water travel times reflect how water flows through landscapes, with implications for water quality and quantity. To date, most water age studies have focused on the individual compartments of the water cycle such as the unsaturated an...

Plants mediate water fluxes within the soil–vegetation–atmosphere continuum. This water transfer in soils, through plants, into the atmosphere can be effectively traced by stable isotopologues of water. However, rapid dynamic processes have only recently gained attention, such as adaptations in root water uptake depths (within hours to days) or the...

Reduced precipitation treatments often are used in field experiments to explore the effects of drought on plant productivity and species composition. However, in seasonally snow-covered regions reduced precipitation also reduces snow cover, which can increase soil frost depth, decrease minimum soil temperatures and increase soil freeze–thaw cycles....

Drought is a major environmental constrain affecting plant performance and survival, particularly in Mediterranean ecosystems. Terpenoids may play a protective role under these conditions, however, observations of drought effects on plant terpenoid emissions are controversial ranging from decreased emissions to unaffected or increased release of te...

For more than two decades, research groups in hydrology, ecology, soil science, and biogeochemistry have performed cryogenic water extractions (CWEs) for the analysis of δ2H and δ18O of soil water. Recent studies have shown that extraction conditions (time, temperature, and vacuum) along with physicochemical soil properties may affect extracted soi...

Agricultural crops play an important role in the global carbon and water cycle. Global climate change scenarios predict enhanced water scarcity and altered precipitation pattern in many parts of the world. Hence, a mechanistic understanding of water fluxes, productivity and water use efficiency of cultivated crops is of major importance, i.e. to ad...

LAI and T/ETo relationship. Relationship between T/ETo and LAI of (a) paddy and (b) rainfed rice.LAI was calculated as leaf area per ground area where Leaf area (LA) was determined with a Leaf Area Meter (LI−3000A, LI−COR, USA). T/ETo was calculated as the ratio of estimated daily transpiration of the LAI measurement date (Eqs 3 and 6) to estimated...

Simulated canopy transpiration. Simulated canopy transpiration followed the seasonal trends of measured leaf transpiration (Mean ± SE) of (a) rainfed rice (b) paddy rice. (PNG)

Water and carbon fluxes, grain yield and water use efficiency of paddy and rainfed rice. Net Ecosystem Exchange (NEE, -NEE = GPP+ Reco) is the balance between photosynthetic uptake and release of carbon dioxide by autotrophic and heterotrophic respiration. Gross primary production (GPP) is photosynthetic uptake. Ecosystem respiration (Reco) is resp...

Calculations of net radiation and ET. (DOCX)

LAI and NDVI relationship. Relationship between NDVI and LAI of (a) paddy rice and (b) rainfed rice. LAI was calculated as leaf area per ground area where Leaf area (LA) was determined with a Leaf Area Meter (LI−3000A, LI−COR, USA). NDVI was measured by Cropscan (Cropscan Inc., USA). (PNG)

Field management activities and timeline in DOY. (DOCX)

Correlation matrix of carbon and water fluxes and environmental variables of paddy rice. (DOCX)

Correlation matrix of carbon and water fluxes and environmental variables of rainfed rice. (DOCX)

Simulated daily crop growth. Simulated daily crop growth of paddy and rainfed rice a) LAI, b) NDVI, c) Dual crop coefficient (Kcb). Daily Kcb was simulated based on daily NDVI, after following Choudhury 1994. (PNG)

GRAMI rice crop model flow diagram adapted from (Maas, 1995; Ko et al., 2015.). (PNG)

Comparison of different crop ET estimation methods. Mk, PT, 56PM, m56PM80, m56PM100, m56PM120 are conventional reference crop ET (ET0, grass as reference crop) estimation methods while m56PMmrc is reference crop ET of rice (ET0, healthy and well-watered rice as reference crop). Kcb_FAO is the FAO recommended hypothetical basal crop coefficients (Pr...

For more than two decades, research groups in hydrology, ecology, soil science and biogeochemistry have performed cryogenic water extractions for the analysis of δ²H and δ¹⁸O of soil water. Recent studies have shown that extraction conditions (time, temperature, and vacuum) along with physicochemical soil properties may affect extracted soil water...

The presence of vegetation alters hydrological cycles of ecosystems. Complex plant–soil interactions govern the fate of precipitation input and water transitions through ecosystem compartments. Disentangling these interactions is a major challenge in the field of ecohydrology and a pivotal foundation for understanding the carbon cycle of semi-arid...

Oxygen isotope signatures of transpiration (δE) are powerful tracers of water movement from plant to global scale. However, a mechanistic understanding of how leaf morphological/physiological traits effect δE is missing. A laser spectrometer was coupled to a leaf-level gas-exchange system to measure fluxes and isotopic signatures of plant transpira...