TY  - JOUR
A1  - Frank, Dorothe A.
A1  - Reichstein, Markus
A1  - Bahn, Michael
A1  - Thonicke, Kirsten
A1  - Frank, David
A1  - Mahecha, Miguel D.
A1  - Smith, Pete
A1  - Van der Velde, Marijn
A1  - Vicca, Sara
A1  - Babst, Flurin
A1  - Beer, Christian
A1  - Buchmann, Nina
A1  - Canadell, Josep G.
A1  - Ciais, Philippe
A1  - Cramer, Wolfgang
A1  - Ibrom, Andreas
A1  - Miglietta, Franco
A1  - Poulter, Ben
A1  - Rammig, Anja
A1  - Seneviratne, Sonia I.
A1  - Walz, Ariane
A1  - Wattenbach, Martin
A1  - Zavala, Miguel A.
A1  - Zscheischler, Jakob
T1  - Effects of climate extremes on the terrestrial carbon cycle: concepts, processes and potential future impacts
JF  - Global change biology
N2  - Extreme droughts, heat waves, frosts, precipitation, wind storms and other climate extremes may impact the structure, composition and functioning of terrestrial ecosystems, and thus carbon cycling and its feedbacks to the climate system. Yet, the interconnected avenues through which climate extremes drive ecological and physiological processes and alter the carbon balance are poorly understood. Here, we review the literature on carbon cycle relevant responses of ecosystems to extreme climatic events. Given that impacts of climate extremes are considered disturbances, we assume the respective general disturbance-induced mechanisms and processes to also operate in an extreme context. The paucity of well-defined studies currently renders a quantitative meta-analysis impossible, but permits us to develop a deductive framework for identifying the main mechanisms (and coupling thereof) through which climate extremes may act on the carbon cycle. We find that ecosystem responses can exceed the duration of the climate impacts via lagged effects on the carbon cycle. The expected regional impacts of future climate extremes will depend on changes in the probability and severity of their occurrence, on the compound effects and timing of different climate extremes, and on the vulnerability of each land-cover type modulated by management. Although processes and sensitivities differ among biomes, based on expert opinion, we expect forests to exhibit the largest net effect of extremes due to their large carbon pools and fluxes, potentially large indirect and lagged impacts, and long recovery time to regain previous stocks. At the global scale, we presume that droughts have the strongest and most widespread effects on terrestrial carbon cycling. Comparing impacts of climate extremes identified via remote sensing vs. ground-based observational case studies reveals that many regions in the (sub-)tropics are understudied. Hence, regional investigations are needed to allow a global upscaling of the impacts of climate extremes on global carbon-climate feedbacks.
KW  - carbon cycle
KW  - climate change
KW  - climate extremes
KW  - climate variability
KW  - disturbance
KW  - terrestrial ecosystems
Y1  - 2015
U6  - https://doi.org/10.1111/gcb.12916
SN  - 1354-1013
SN  - 1365-2486
VL  - 21
IS  - 8
SP  - 2861
EP  - 2880
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Guerrero, Martin A.
A1  - Fang, Xuan
A1  - Miller Bertolami, Marcelo Miguel
A1  - Ramos-Larios, Gerardo
A1  - Todt, Helge Tobias
A1  - Alarie, Alexandre
A1  - Sabin, Laurence
A1  - Miranda, Luis F.
A1  - Morisset, Christophe
A1  - Kehrig, Carolina
A1  - Zavala, Saul A.
T1  - The inside-out planetary nebula around a born-again star
JF  - Nature Astronomy
N2  - Planetary nebulae are ionized clouds of gas formed by the hydrogen-rich envelopes of low- and intermediate-mass stars ejected at late evolutionary stages. The strong UV flux from their central stars causes a highly stratified ionization structure, with species of higher ionization potential closer to the star. Here, we report on the exceptional case of HuBi 1, a double-shell planetary nebula whose inner shell presents emission from low-ionization species close to the star and emission from high-ionization species farther away. Spectral analysis demonstrates that the inner shell of HuBi 1 is excited by shocks, whereas its outer shell is recombining. The anomalous excitation of these shells can be traced to its low-temperature [WC10] central star whose optical brightness has declined continuously by 10 magnitudes in a period of 46 years. Evolutionary models reveal that this star is the descendant of a low-mass star (≃1.1 M⊙) that has experienced a ‘born-again’ event1 whose ejecta shock-excite the inner shell. HuBi 1 represents the missing link in the formation of metal-rich central stars of planetary nebulae from low-mass progenitors, offering unique insight regarding the future evolution of the born-again Sakurai’s object2. Coming from a solar-mass progenitor, HuBi 1 represents a potential end-state for our Sun.
KW  - Astronomy and astrophysics
KW  - Astronomy and planetary science
KW  - Interstellar medium
KW  - Stars
KW  - Stellar evolution
Y1  - 2018
U6  - https://doi.org/10.1038/s41550-018-0551-8
SN  - 2397-3366
VL  - 2
IS  - 10
SP  - 784
EP  - 789
PB  - Nature Publ. Group
CY  - London
ER  -