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Abstract Detail


Pratt, Brandon [1], Jacobsen, Anna [2].

Xylem transport safety and efficiency differs among South African fynbos shrub life history types and between two sites differing in mean rainfall.

Xylem safety and efficiency were analyzed for stems of evergreen fynbos shrubs communities in the Mediterranean-type climate region of South Africa. We hypothesized that species with different life history types would differ in xylem function on account of their different regeneration niches as has been found previously for chaparral shrubs inhabiting the Mediterranean-type climate region in California. Comparisons were made among four different life history types: post-fire non-sprouters; facultative sprouters; obligate sprouters; and opportunists. Measurements included xylem resistance to water stress-induced cavitation (xylem safety) and xylem specific hydraulic conductivity (xylem efficiency) at a dry site and a wetter site. Life history types differed in hydraulic traits: xylem safety was greater in life history types with disturbance-dependent recruitment. In contrast, water stress resistance was lowest in obligate resprouters that recruit seedlings during fire-free intervals in the litter layer of shady microsites. Among life history types, greater xylem safety came at the cost of reduced hydraulic efficiency. This pattern was also observed between field sites, with most taxa from a drier site having greater levels of cavitation resistance and lower levels of Ks than taxa from a wetter site. We conclude that xylem traits are linked to differences in life history types in fynbos species. The differences among life history type in hydraulic traits are not the same between morphologically convergent chaparral and fynbos communities. This suggests that chaparral and fynbos life history types are not convergent in their hydraulic traits and regeneration niches. Differences in rainfall reliability and mineral nutrients are hypothesized to explain the lack of convergence.

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1 - CALIFORNIA STATE UNIVERSITY BAKERSFIELD, DEPARTMENT OF BIOLOGY, 9001 Stockdale Highway, Bakersfield, CA, 93311-1099, USA, 310-740-7653
2 - California State University Bakersfield, 9001 Stockdale Hwy, 61 SCI, Bakersfield, CA, 93311, USA

life history
stem hydraulics

Presentation Type: Oral Paper:Papers for Topics
Session: 23
Location: Fayette/Hyatt
Date: Tuesday, July 10th, 2012
Time: 9:00 AM
Number: 23005
Abstract ID:224

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