Summary1. Ecosystem change is predicted to become more prevalent with climate change. Widespread dieback of cushion plants and bryophytes in alpine fellfield on Macquarie Island may represent such change. Loss of the keystone endemic cushion plant, Azorella macquariensis, was so severe that it has been declared critically endangered. 2. We document the dieback and its extent. Due to the rapidity of the event, we sought to infer causes by testing two mechanistic hypotheses: (i) that extensive dieback was due to a pathogen and (ii) that dieback was a consequence of a change in climate that induced stress in several susceptible species. We searched for pathogens using both conventional and next-generation sequencing techniques. We examined plant functional morphology in conjunction with a long-term climate record of plant-relevant climate parameters to determine whether environmental conditions had become inimical for A. macquariensis. 3. Dieback was found across the entire range of A. macquariensis. A survey found 88% of 115 stratified/ random sites contained affected cushions and 84% contained dead bryophytes. Within-site dieback increased over time. 4. No conclusive evidence that A. macquariensis deaths were caused by a definitive diseasecausing pathogen emerged. However, the presence of bacterial, fungal and oomycete taxa, some potentially pathogenic, suggested that stressed cushions could become susceptible to infection. 5. The primary cause of collapse is suspected failure of A. macquariensis and other fellfield species to withstand recent decadal changes in summer water availability. Increased wind speed, sunshine hours and evapotranspiration resulted in accumulated deficits of plant available water spanning 17 years (1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008). High vulnerability to interrupted water supply was consistent with functional morphology of A. macquariensis, and climate change has altered the species' environment from wet and misty to one subject to periods of drying. Journal of Applied Ecology 2015Ecology , 52, 774-783 doi: 10.1111Ecology /1365Ecology -2664 were complex and multiple stressors appeared to be impacting cumulatively may be relevant to other locations.

Abstract:The wound-associated wood that developed 17 months following artificial xylem injury in Eucalyptus globulus (Labill) and Eucalyptus nitens (Maiden) was examined anatomically and chemically. This new tissue located immediately adjacent to the wound site and termed "wound wood" was highly variable consisting of callus, altered wood of increased parenchyma density, and dark extractives, visible to the naked eye. Subsequent chemical analysis of crude wound wood extracts by HPLC coupled to negative ion electrospray mass spectrometry revealed the presence of a diverse range of polyphenolic compounds including hydrolysable tannins, proanthocyanidins, flavanone glycosides, and formylated phloroglucinol compounds. A number of polyphenols were unequivocally identified including engelitin, pedunculagin, and tellimagrandin I. Other compounds present in wound wood include various hydroxystilbene glycosides and volatile terpenes. The importance of the diverse range of secondary metabolites detected in wound wood is discussed in relation to tree wound repair responses. Résumé :Les caractéristiques anatomiques et chimiques du bois associé aux blessures qui s'était développé 17 mois après avoir infligé des blessures artificielles au xylème ont été étudiées chez Eucalyptus globulus (Labill) et Eucalyptus nitens (Maiden). Ces nouveaux tissus situés immédiatement autour de la blessure et appelés « bois blessé » étaient très variés et constitués de calus, de bois altéré avec une densité plus élevée de parenchyme et plus de substances solubles de couleur noire visibles à l'oeil nu. Des analyses chimiques subséquentes d'extraits bruts de bois blessé par chromatographie liquide haute performance couplée à la spectrométrie de masse avec électronébulisation d'ions chargés négati-vement a révélé la présence d'une gamme diversifiée de polyphénols incluant des tannins hydrolysables, des proanthocyanidines, des glycosides flavanoïdes et des phloroglucinols contenant des radicaux formyle. Plusieurs polyphénols ont été catégoriquement identifiés incluant l'engélitine, la pédunculagine, et la tellimagrandine I. D'autres composés présents dans le bois blessé incluent divers hydroxystilbènes glycosides et des terpènes volatiles. L'importance de la gamme variée de métabolites secondaires détectés dans le bois blessé est discutée en relation avec les réactions associées à la cicatrisation des blessures chez les arbres.[Traduit par la Rédaction] Eyles et al. 2339

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