Project

Discipline

climate reconstruction; stable isotopes; tree rings; tree physiology; Boreal forests; elevated CO2; Siberia; Alps; Medieval optimum; Little ice age; photosynthesis; carbon dioxide

Lead
Lay summary
High-latitude and high-altitude forests are sensitive ecosystems that are more exposed to global warming in recent decades than forests of the temperate zones. As a result of the accelerating climate change, these forests may undergo severe changes regarding spatial distribution and species composition, the carbon, water and nitrogen cycles. This will have tremendous consequences for the sustainable functioning of the ecosystems and potential feedbacks to the atmosphere, such as increased release of greenhouse gases from soils. Insight into extreme past climate conditions and the response of Boreal and Alpine forests to these conditions provides an invaluable analogy for the potential future response. Trees from temperature-limited sites are known as sensitive proxies for climate reconstruction, while the availability of well-preserved wood in these regions enable the deciphering of past environmental conditions for centuries up to millennia.In this project, our main goal is to obtain a comprehensive description of the climatic and environmental changes during pronounced warm and cool periods of the past 1500 years. We want to achieve this goal by addressing the following three objectives:1) we aim to better quantify the magnitude of temperature and precipitation variability for known periods of extreme climate conditions, focusing on the cold anomaly around 536AD, the Medieval optimum period, the “little ice age” period and the last century,2) we will use the combined analysis of tree-ring width, carbon and oxygen isotopes and physiological models to decipher the response of the trees in terms of photosynthesis and water-use during these periods,3) and we want to determine the spatial and temporal coherence of large-scale climate events for Europe and northern Eurasia.We have access to unique dated tree-ring material from three sites in Northern Siberia and one site from the Alps that cover the investigation periods. We will use ring-width as a measure of growth and stable isotope ratios of carbon and oxygen of tree-ring cellulose as a measure of photosynthesis and water-use, while both isotopes are also related to temperature and precipitation. By applying a coupled photosynthesis-isotope fractionation model, which is driven by microclimate, photosynthesis, and soil water balance, we will be able to relate climatic to physiological changes. The results of the project will enable us to better understand the response of trees in temperature-limited environment to a changing climate.

Direct link to Lay Summary

Last update: 21.02.2013

Number	Title	Start	Funding scheme

High-latitude and high altitude forests are sensitive ecosystems that are more exposed to global warming in recent decades than forests of the temperate zones. As a result of the accelerating climate change, these forests may undergo severe changes regarding spatial distribution and species composition, the carbon, water and nitrogen cycles. This will have tremendous consequences for the sustainable functioning of the ecosystems and potential feedbacks to the atmosphere, such as increased release of greenhouse gases from soils. Insight into extreme past climate conditions and the response of Boreal and Alpine forests to these conditions provides an invaluable analogy for the potential future response. Trees from temperature-limited sites are also known as sensitive proxies for climate reconstruction, while the availability of well-preserved wood in these regions enable the deciphering of past environmental conditions for centuries up to millennia.In this project, our main goal is to obtain a comprehensive description of the climatic and environmental changes during pronounced warm and cool periods of the past 1500 years. We want to achieve this goal by addressing the following three objectives:1) we aim to better quantify the magnitude of temperature and precipitation variability for known periods of extreme climate conditions, focusing on the cold anomaly around AD 536, the Medieval optimum period AD 900-1150, the maximum of the so-called “little ice age” period (AD 1600-1815) and the last century (1900 to present),2) we will use the combined analysis of tree-ring width, carbon and oxygen isotopes and physiological models to decipher the response of the trees in terms of photosynthesis and water-use during these periods,3) and we want to determine the spatial and temporal coherence of large-scale climate events for Europe and northern Eurasia.With the proposed periods, we cover climate anomalies on different time-scales (years to centuries), different rates of change (from sudden to gradual) and of different direction (warming or cooling). All these events are known to be large-scale events, but with different spatial extent. We have access to unique dated tree-ring material from three sites in Northern Siberia and one site from the Alps that cover the investigation periods. The site coverage will enable us to retrieve large-scale climatic connections, considering also oxygen isotope variations in ice-cores from Altai and Greenland and other published tree-ring records for comparison. We will use ring-width as a measure of growth and stable isotope ratios of carbon and oxygen of tree-ring cellulose as a measure of photosynthesis and water-use, while both isotopes are also related to temperature and precipitation. By applying a coupled photosynthesis-isotope fractionation model, which is driven by microclimate, photosynthesis, and soil water balance, we will be able to relate climatic to physiological changes. This project combines in an innovative way aspects of climatology, physiology and modeling, and applies them to a world-wide unique data set of historic wood. The results of the project will enable us to better understand the response of trees in temperature-limited environment to a changing climate.