The die-off, triggered by the drought from 2000-2003, is estimated to have affected up to 17% of Colorado aspen forests. In 2002, the drought subjected the trees to the most extreme growing season water stress of the past century.
While often not killing the trees directly, the drought damaged the ability of the trees to provide water to their leaves, leading to a decline in growth and increased mortality that has continued for a decade after the drought. The research is published on-line in Global Change Biology. Another related study appeared earlier this year in the same journal.
Until recently, there has been little attention paid to what drought characteristics (seasonal differences, severity, or durations) actually cause trees to die. Scientists additionally have lacked a sufficient understanding of the processes that lead to die-offs, which inhibits the ability to predict how climate change can affect different ecosystems.
The recent study was led by brothers Leander and William Anderegg.* William was a Ph.D. student while Leander was an undergraduate at the time of the research at Carnegie. The team looked at the dynamics of water availability to the trees by examining the ratio of oxygen isotopes in the sap contained in the tree "veins" that transport water. Isotopes are atoms with the same number of protons, but different numbers of neutrons and their ratios are signatures of where and when water originates, among other features.
"Mother nature provides us with natural fingerprints in the ratio of oxygen isotopes," explained Leander. "They tell us about the type of water available to the trees. For instance, summer rain has different isotopic ratios than winter snow. So we can use these markers to figure out where and when the water found in tree veins was taken up, which in turn helps us determine drought impacts."
The scientists examined the isotopes in the aspen sap during natural and experimental drought in an area in Colorado that had heavy tree casualties. It turns out that aspens generally use shallow soil moisture, which evaporated quickly with increased temperatures during the summer drought of 2002. They then looked at climate data finding that these high temperatures were part of a long-term increasing trend, likely linked with climate change, a unique feature of this drought that separates it from earlier less damaging droughts.
"Forests store about 45 percent of the carbon found on land," remarked William. "Widespread tree death can radically transform ecosystems, affecting biodiversity, posing fire risks, and even harming local economies. Rapid shifts in ecosystems, particularly through vegetation die-offs could be among the most striking impacts of increased drought and climate change around the globe."
In a previous study the brothers, with colleagues, looked at two competing theories for how forest trees die during a drought. One hypothesis was that the trees starved due to decreased photosynthesis. Another was that the system for transporting water within a tree was damaged beyond repair. They looked at both carbon starvation and water-transportation stress and found no evidence of significantly decreased carbon reserves. They did find a notable depressed function in the trees' water-transport systems, especially in the roots—some 70 percent loss of water conductivity.
This study pinpoints the trigger of this loss—summer temperature was the most important climate variable for explaining aspen death by drying out surface soil and stressing the trees' water-transport system. Joe Berry, a co-author and Carnegie staff scientist, noted that understanding how and where the trees get their water was key to unraveling cause and effect in this study.
"Since there is a very strong upward trend in Colorado summer temperatures, they could link tree death to climate change," said Chris Field, director of the Carnegie department. This study is a milestone in linking plant-level physiology measurements with large-scale climate to predict vulnerability to climate change in these forests.
Interestingly, this type of climate-change hot summer drought actually occurred again in 2012, which could indicate more tree die-offs are in the pipeline for the near future.
*Other researchers on the paper are John Abatzoglou, University of Idaho; Alexandra Hausladen, Stanford University; and Joseph Berry, Carnegie. The work was supported by Carnegie, the Bill Lance Center for the American West, Morrison Institute, Phi Beta Kappa Northern California Association, Jasper Ridge Biological reserve, Stanford VPUE Program, NSF DDIG Program, and THE Stanford Biology SCORE Program.
Published related work includes:Anderegg, W.R.L., Plavcova, L., Anderegg, L.D.L. Hacke, U.G., Berry, J.A., Field, C.B. (2013) Drought's legacy: multiyear hydraulic deterioration underlies widespread aspen forest die-off and portends increased future risk. Global Change Biology. doi: 10.1111/gcb.12100,
The Department of Global Ecology was established in 2002 to help build the scientific foundations for a sustainable future. The department is located on the campus of Stanford University, but is an independent research organization funded by the Carnegie Institution. Its scientists conduct basic research on a wide range of large-scale environmental issues, including climate change, ocean acidification, biological invasions, and changes in biodiversity.
The Carnegie Institution for Science has been a pioneering force in basic scientific research since 1902. It is a private, nonprofit organization with six research departments throughout the U.S. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
Leander Anderegg | EurekAlert!
Worldwide Success of Tyrolean Wastewater Treatment Technology
27.05.2016 | Universität Innsbruck
How nanoparticles flow through the environment
12.05.2016 | Schweizerischer Nationalfonds SNF
Auf biologischem Weg und mit geringem Energieeinsatz wandelt ein an der Universität Innsbruck entwickeltes Verfahren in Kläranlagen anfallende Stickstoffverbindungen in unschädlichen Luftstickstoff um. Diese innovative Technologie wurde nun gemeinsam mit dem US-Wasserdienstleister DC Water weiterentwickelt und vermarktet. Für die Kläranlage von Washington DC wird die bisher größte DEMON®-Anlage errichtet.
Das DEMON®-Verfahren wurde bereits vor elf Jahren entwickelt und von der Universität Innsbruck zum Patent angemeldet. Inzwischen wird die Technologie in rund...
A biological and energy-efficient process, developed and patented by the University of Innsbruck, converts nitrogen compounds in wastewater treatment facilities into harmless atmospheric nitrogen gas. This innovative technology is now being refined and marketed jointly with the United States’ DC Water and Sewer Authority (DC Water). The largest DEMON®-system in a wastewater treatment plant is currently being built in Washington, DC.
The DEMON®-system was developed and patented by the University of Innsbruck 11 years ago. Today this successful technology has been implemented in about 70...
Genauer sind sie jetzt schon, aber noch nicht so zuverlässig. Daher haben optische Uhren, die schon einige Jahre lang als die Uhren der Zukunft gelten, die...
Für Zukunftstechnologien wie Elektromobilität und erneuerbare Energien ist der Einsatz von starken Dauermagneten von großer Bedeutung. Für deren Herstellung werden Seltene Erden benötigt. Dem Fraunhofer-Institut für Werkstoffmechanik IWM in Freiburg ist es nun gelungen, mit einem selbst entwickelten Simulationsverfahren auf Basis eines High-Throughput-Screening (HTS) vielversprechende Materialansätze für neue Dauermagnete zu identifizieren. Das Team verbesserte damit die magnetischen Eigenschaften und ersetzte gleichzeitig Seltene Erden durch Elemente, die weniger teuer und zuverlässig verfügbar sind. Die Ergebnisse wurden im Online-Fachmagazin »Scientific Reports« publiziert.
Ausgangspunkt des Projekts der IWM-Forscher Wolfgang Körner, Georg Krugel und Christian Elsässer war eine Neodym-Eisen-Stickstoff-Verbindung, die auf einem...
Ein internationales Forschungsteam, darunter Wissenschaftler der University of Queensland, hat im Süden Australiens einen erfolgreichen Hyperschallgeschwindigkeitstestflug absolviert und damit futuristische Reisemöglichkeiten greifbarer gemacht.
Flugreisen von London nach Sydney in unter zwei Stunden werden, dank des HiFiRE Programms, immer realistischer. Im Rahmen dieses Projekts werden in den...
27.05.2016 | Veranstaltungen
27.05.2016 | Veranstaltungen
27.05.2016 | Veranstaltungen
27.05.2016 | Seminare Workshops
27.05.2016 | Seminare Workshops
27.05.2016 | Förderungen Preise