Application of Flux and Stable Isotope Techniques for Studying Interactions at the Soil-Plant-Atmosphere Continuum
About My Research
Maren Dubbert has long term expertise in eco-physiology and ecohydrology, developing novel flux and isotope based approaches to partition water and carbon cycling in various land-use types spanning temperate grasslands, rice fields, and Mediterranean savanna type woodlands (Dubbert et al., 2014a;Piayda et al., 2014;NayHtoon et al., 2018;Kübert et al., 2019). Outstanding is her cross-scale approach, which ranges from ecosystem flows (eddy covariance method of stand and understory) to chamber measurements (branch, soil, herbaceous layer) to vegetation structure. By doing so, she has challenged dominating approaches and consistently implemented existing theory, which represents a significant scientific development for isotope-based ecosystem analysis. She has validated the Craig-Gordon model under field conditions (Dubbert et al., 2013) demonstrating the importance of accurate characterization of environmental parameters. Furthermore, she was able to show for the first time that the stable water isotope fractionation processes during the phase transition of leaf water into the vapor phase in the stomata lead to the fact that the isotopic composition of the transpiration signal in Mediterranean species is strongly depleted during the day, i.e. it is not in isotopic equilibrium (Dubbert et al., 2014, 2017, Kübert et al., 2022). Apart from her work on biosphere atmosphere exchange, she has extensively contributed to improve our understanding of root-water-uptake dynamics and water movement in soils and plants (Dubbert et al., 2018;Magh et al., 2020;Deseano-Diaz et al., 2022;Dubbert et al., 2022). In particular, she advocates holistic, interdisciplinary approaches, combining plant ecoohysiology, ecohydrology and ecology to resolve currently limited understanding of the dynamic optimization of the root system in regard to conflicting demands in terms of water and nutrient uptake, particularly under drought. Thus, her work has fundamentally changed the understanding of water stable isotope fractionation and modelling in the rapidly expanding research field of ecohydrology and significantly contributed to an improved understanding of soil-plant-atmosphere dynamics (Dubbert & Werner, 2019).
How Picarro Analyzers Helped
Maren Dubbert has long-term experience in the application of flux and stable isotope techniques for studying interactions at the soil-plant-atmosphere continuum (e.g. Dubbert et al., 2013, 2014a,b, 2017, 2018;Kuebert et al., 2019, 2020, 2022;Kuehnhammer et al., 2019). Since the earliest days of her scientific career has significantly utilized newly developed isotope based laser spectroscopy and was on the forefront of the development of in situ isotope monitoring systems by coupling various generations of Picarro water laser spectrometers to gas-exchange chambers (from the leaf to canopy top chambers and nowadays modern automated gantry crane chamber systems), as well as semi permeable membrane sensors enabling the estimation of xylem or soil water isotopic signatures. Prior to the advent of laser spectroscopy, the now quickly expanding field of ecohydrology faced significant technical limitations: relying of isotope ratio mass spectrometry, the direct estimation of water isotopic signatures in the gas phase and in high resolution was impossible. Questions related to partitioning of ecosystem water fluxes (e.g. partitioning evapotranspiration into plant transpiration and soil evaporation) or root water uptake dynamics (e.g. dynamic changes in uptake depths), were impossible to answer. In terms of root water uptake the combination of in-situ observation of soil and xylem isotopes with with stable isotope mixing models currently provide the only in-situ and highly resolved method to quantify the water uptake depth probabilities of individual plants or communities. While their use was once limited to the classification of plant species reliance on rainwater versus groundwater (Evaristo and McDonnell, 2017), such techniques are now routinely used in the fields of hydrology and ecohydrology (Dubbert et al., 2018;2019;Kühnhammer et al., 2019, Deseano-Diaz et al., 2022).
Consequently, without the development of isotope laser spectroscopy, the recent knowledge gain in eco-physiology and ecohydrology, which has been a central pillar of the career development of Maren Dubbert´s research, would have been impossible.