Title

When do nurse plants stop nursing? Temporal changes in water stress levels in Austrocedrus chilensis growing within and outside shrubs

Authors

Authors

C. I. Nunez; E. Raffaele; M. A. Nunez;F. Cuassolo

Comments

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Abbreviated Journal Title

J. Veg. Sci.

Keywords

Cupressaceae; Nahuel Huapi National Park; Patagonia; Plant interactions; Water potential; NORTHERN PATAGONIA; POSITIVE INTERACTIONS; FACILITATION; COMMUNITIES; COMPETITION; TREE; AVAILABILITY; RESTORATION; GRADIENT; SHIFTS; Plant Sciences; Ecology; Forestry

Abstract

Question Does the proximity of shrubs affect seasonal water stress of young Austrocedrus chilensis trees (a native conifer of the Austral Temperate Forest of South America) in xeric sites? Location A. chilensis xeric forest in northwest Patagonia, Argentina. Methods We examined the dependence of predawn twig water potential on tree development (seedling to adult) and proximity to nurse shrubs during spring and summer. We analysed spatial associations of seedlings, saplings and adult trees with nurse shrubs, and also evaluated if trees affected shrub canopy vitality. Results Water stress in Austrocedrus trees was affected by shrub presence. Small trees (i.e.< 0.5 m in height) growing in the open were most stressed, particularly in summer. Small trees growing within a shrub canopy had low water stress and little change between spring and summer. The opposite trend, however, was true for the medium-height category (i.e. 0.5-1.5 m in height); trees in this size category were more stressed when growing within the shrub canopy than in the open. Larger Austrocedrus trees (i.e.> 2 m in height) were not affected by shrub presence. Austrocedrus trees were spatially associated with shrubs in all height classes; however, the percentage of living shrub canopy decreased with tree height. Conclusions In xeric areas of northwest Patagonia, the strength and direction of interactions between A. chilensis and shrubs, in terms of tree water stress, are dynamic and modulated by tree size and environmental conditions. Overall, positive effects of shrubs on early developmental stages appear to be more important than subsequent negative interactions, since nursing effects could generate a spatial association of shrubs and Austrocedrus trees that persists through later successional stages. These findings shed light on mechanisms behind successional changes, and have important conservation and management implications.

Journal Title

Journal of Vegetation Science

Volume

20

Issue/Number

6

Publication Date

1-1-2009

Document Type

Article

Language

English

First Page

1064

Last Page

1071

WOS Identifier

WOS:000271189200009

ISSN

1100-9233

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