Periodic Reporting for period 1 - FLAME (Future ResiLient Forest in a ChAnging ClimatE: isotope observations and mechanistic modeling of soil water residence time and vegetation water uptake dynamics)
Berichtszeitraum: 2022-07-01 bis 2024-06-30
The FLAME project addresses a critical gap in understanding the dynamics of subsurface water storage and its role in forest ecosystems under changing environmental conditions. The central question is how the seasonal origins, turnover times of water used by plants, and water uptake depths will shift in response to climate change. This is essential for predicting vegetation resilience, particularly under drought stress. The interdisciplinary nature of FLAME bridges hydrology and ecology to provide an integrated view of vegetation response to drought, with a focus on European temperate forests.
The project employs newly developed high-frequency, in-situ measurements of stable water isotopes (δ¹⁸O and δ²H) in soil and tree xylem to trace the origins of water used by plants. This data, combined with mechanistic modeling, will improve our understanding of how forest ecosystems will function under future climate scenarios.
This study presents in-situ observations of water isotopes (δ¹⁸O and δ²H) in tree xylem, soil, and atmosphere providing insights into the sources of water that trees utilize throughout seasonal cycles. By comparing isotopic signatures in different soil layers and within tree xylem, we aim to elucidate how trees modulate their water uptake in response to varying soil moisture availability. Our results offer valuable information on the adaptability of trees to climate variability and their resilience in a changing climate and help understanding the tree hydraulic strategies and their potential responses to ongoing environmental shifts. The specific objectives are FLAMES include:
1. Identify the seasonal origins and turnover time of water used by plants — Track water uptake depths and sources, and how these are altered over time and in response to environmental changes.
2. Determine precipitation partitioning and soil water storage variation over time and their effects on vegetation water uptake patterns.
3. Assess the dynamic response and eco-hydrological connectivity of vegetation— Test the resilience of forests under different environmental scenarios.
The project employs newly developed high-frequency, in-situ measurements of stable water isotopes (δ¹⁸O and δ²H) in soil and tree xylem to trace the origins of water used by plants. This data, combined with mechanistic modeling, will improve our understanding of how forest ecosystems will function under future climate scenarios.
This study presents in-situ observations of water isotopes (δ¹⁸O and δ²H) in tree xylem, soil, and atmosphere providing insights into the sources of water that trees utilize throughout seasonal cycles. By comparing isotopic signatures in different soil layers and within tree xylem, we aim to elucidate how trees modulate their water uptake in response to varying soil moisture availability. Our results offer valuable information on the adaptability of trees to climate variability and their resilience in a changing climate and help understanding the tree hydraulic strategies and their potential responses to ongoing environmental shifts. The specific objectives are FLAMES include:
1. Identify the seasonal origins and turnover time of water used by plants — Track water uptake depths and sources, and how these are altered over time and in response to environmental changes.
2. Determine precipitation partitioning and soil water storage variation over time and their effects on vegetation water uptake patterns.
3. Assess the dynamic response and eco-hydrological connectivity of vegetation— Test the resilience of forests under different environmental scenarios.
The terrestrial ecosystem response to the changes in the atmosphere (CO2, VPD, etc.) and the redistribution of water on land in an era of change are largely unknown. In addition, the effects of such environmental changes in trees’ adaptation strategies and resilience under short and long dry conditions are not yet fully understood.
FLAME project focuses on understanding the effects of the long-term manipulation of soil moisture on Scots pine water take patterns and their resilience and adaptation under environmental changes.Our long-term (20-year) soil moisture manipulation experiment in a drought-prone Scots pine-dominated forest in one of the driest areas of Switzerland-Pfynwald, provides a unique opportunity to study dynamic tree water uptake under various soil moisture conditions. The experiment seeks to determine how trees adjust their water uptake strategies under varying soil moisture conditions and whether they shift to deeper water sources when surface water is scarce.
Within teh framework of FLAME, we established an in situ stable water isotopologues monitoring system to determined hydrogen and oxygen isotope compositions at multiple soil layers, multiple tree xylems, and in atmosphere and precipitation within Pfynwald experimental site at sub-daily temporal resolution. Our observations were complemented by measurements of soil water content, sap flow, tree water deficits and destructive soil and xylem sampling for isotope analysis in the lab.
Our measurements included plots with trees growing under naturally dry conditions (control), irrigated (from 2003 to present), and previously irrigated (irrigation stop; irrigated from 2003–2013; control condition since 2014).
Our observations support the hypothesis that pine forests at naturally dry sites compensate their water deficit from a different source (deeper layers or previous season precipitation) as compared to pines at the irrigated site. However Further research and experimental design is needed to understand the thresholds of these adjustments to environmental shifts.
FLAME project focuses on understanding the effects of the long-term manipulation of soil moisture on Scots pine water take patterns and their resilience and adaptation under environmental changes.Our long-term (20-year) soil moisture manipulation experiment in a drought-prone Scots pine-dominated forest in one of the driest areas of Switzerland-Pfynwald, provides a unique opportunity to study dynamic tree water uptake under various soil moisture conditions. The experiment seeks to determine how trees adjust their water uptake strategies under varying soil moisture conditions and whether they shift to deeper water sources when surface water is scarce.
Within teh framework of FLAME, we established an in situ stable water isotopologues monitoring system to determined hydrogen and oxygen isotope compositions at multiple soil layers, multiple tree xylems, and in atmosphere and precipitation within Pfynwald experimental site at sub-daily temporal resolution. Our observations were complemented by measurements of soil water content, sap flow, tree water deficits and destructive soil and xylem sampling for isotope analysis in the lab.
Our measurements included plots with trees growing under naturally dry conditions (control), irrigated (from 2003 to present), and previously irrigated (irrigation stop; irrigated from 2003–2013; control condition since 2014).
Our observations support the hypothesis that pine forests at naturally dry sites compensate their water deficit from a different source (deeper layers or previous season precipitation) as compared to pines at the irrigated site. However Further research and experimental design is needed to understand the thresholds of these adjustments to environmental shifts.
The FLAME project has made significant progress beyond the state of the art in understanding tree-water relations and forest resilience in the face of climate change. Through innovative methodologies and advanced technologies, such as the High-Frequency tree xylem, soil water, and precipitation Isotope Monitoring System, the project has facilitated real-time data collection and analysis, enabling a deeper understanding of how Scots pine trees adjust their water uptake strategies under varying moisture conditions. These advancements are expected to yield critical insights into the physiological responses of forest ecosystems to climate stressors, ultimately enhancing predictive models of forest dynamics in a changing climate.
The comprehensive datasets produced during the course of the project will inform both academic research and practical forest management strategies. The socio-economic impacts are substantial; insights gained from the project can guide forest management practices, ensuring the sustainability of these ecosystems and their associated services. For instance, by predicting tree mortality and growth under different drought scenarios, forest managers can make informed decisions to mitigate risks. The findings can inform policies aimed at climate adaptation and resilience, fostering community awareness and action in addressing the challenges posed by climate change on forest ecosystems.
The comprehensive datasets produced during the course of the project will inform both academic research and practical forest management strategies. The socio-economic impacts are substantial; insights gained from the project can guide forest management practices, ensuring the sustainability of these ecosystems and their associated services. For instance, by predicting tree mortality and growth under different drought scenarios, forest managers can make informed decisions to mitigate risks. The findings can inform policies aimed at climate adaptation and resilience, fostering community awareness and action in addressing the challenges posed by climate change on forest ecosystems.