Maren Dubbert

Leibniz Centre for Agricultural Landscape Research | ZALF · Research Area 1 “Landscape Functioning“

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 only recently gained attention, such as adaptations in root water uptake depths (within hours to days) or the impr...

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...

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...

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...

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...

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 i...

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...

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....

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...

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 non‐destructive monito...

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...

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 sub-disciplines) of the hydrological cycle such as the unsaturated or sa...

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 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...

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...

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...

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...

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 transpir...

Light use efficiency (LUE) plays a vital role in determination of crop biomass and yield. Important com- ponents of LUE, i.e. canopy structure, nitrogen distribution, photosynthetic capacity and CO2 diffusion conductance were investigated in paddy rice grown under low, normal and high supplemental nitrogen (0, 115, and 180 kg N h...

Water is the main driver of ecosystem productivity in most terrestrial ecosystems worldwide. The predicted increase in rainfall variability and extreme climatic events under future climate conditions are therefore anticipated to strongly affect plant and ecosystem functioning. As 55–70% of terrestrial evapotranspirational water loss is directly con...

Most visitors of a sauna appreciate the heat pulse that is perceived when water is poured on the stones of a sauna stove. However, probably only few bathers are aware that this pleasant heat pulse is caused by latent heat being released onto our skin due to condensation of water vapour. In order to quantify the proportion of condensation water vers...

Savannah-type ecosystems account for 26–30% of global gross primary productivity GPP, with water being one of the major driving factors. In Europe, savannah-type woodlands cover an area of about 1.5 million ha. Here, the recent past has shown a significant decrease in precipitation P in winter and spring as well as a decrease in total annual precip...

Semi-arid ecosystems contribute about 40% to global net primary production (GPP) even though water is a major factor limiting carbon uptake. Evapotranspiration (ET) accounts for up to 95% of the water loss and in addition, vegetation can also mitigate drought effects by altering soil water distribution. Hence, partitioning of carbon and water fluxe...

Savannah-type ecosystems account for 26-30% of global gross primary productivity GPP with water being one of the major driving factors. In Europe, savannah-type woodlands cover an area of about 1.5 million ha. Here, the recent past has shown a significant decrease of precipitation P in winter and spring as well as decrease of total annual precipita...