Does drought incite tree decline and death in Austrocedrus chilensis forests?

AMOROSO, M.; DANIELS, L.D.; VILLALBA, R.; CHERUBINI, P.

JOURNAL OF VEGETATION SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2015 vol. 26 p. 1171 - 1183

1100-9233

AbstractQuestions: Is mal del cipres, the widespread decline and death of Austrocedruschilensis trees, caused by a single pathogen or multiple factors? Using a noveldendrochronological approach, we disentangled the influences of climatic variation on the radial growth decline and death of A. chilensis trees in declining forests.We distinguish possible causes of reduced radial growth and mortality fromautogenic processes driven by stand development. We present a conceptualmodel of forest decline includingmultiple factors that predispose, incite and contributed to decreased radial growth and death of A. chilensis.Location: A. chilensis forests onmesic sites in northern Patagonia, Argentina.Methods: We used dendrochronology to determine the years of (1) onset ofradial growth decline of 301 living and dead trees stratified by canopy position atdecline onset, and (2) mortality of 339 trees stratified by radial growth patternsand canopy position at death. Events were years with low or high numbers oftrees initiating decline or dying. We tested the hypothesis that onset of decline and mortality were concurrent with drought for individual trees, using contingency tables, and for events, using superposed epoch analysis.Results: Climatic variability acts as an environmental stress inciting and contributing to stand-level forest decline. The onset of radial growth decline and mortality of individual trees were significantly associated with summermoisture deficits. High-magnitude onset-of-decline andmortality events were concurrent with adverse climatic conditions.Conclusions: Climatic variation and drought incite and contribute to tree- andstand-level decline andmortality in A. chilensis forests. Deciphering the effects of stand development is critical as autogenic processes independently drive tree mortality and mediate the effects of climatic variability on A. chilensis forest decline. Based on our results, we present a conceptual model within the framework of a forest decline process, and conclude A. chilensis mortality is a forest decline process driven by complex interactions between allogenic abiotic and biotic factors and autogenic stand development processes. Site conditions, genetic variation and sex of trees are predisposing factors that likely interact with the pathogen Phytophthora.