Coordinating leaf functional traits with branch hydraulic conductivity: Resource substitution and implications for carbon gain

Publication Type:
Journal Article
Citation:
Tree Physiology, 2008, 28 (8), pp. 1169 - 1177
Issue Date:
2008-01-01
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We studied relationships among branch hydraulic conductivity, xylem embolism, stomatal conductance (gs), foliar nitrogen (N) concentration and specific leaf area (SLA) of seven tree species growing at four temperate woodland sites spanning a 464-1350 mm rainfall gradient. Specifically, we examined the question: are gsand foliar N concentration coordinated with branch hydraulic conductivity and, if so, what are the implications for carbon assimilation? Area-based, light-saturated photosynthetic rate (Aa) was uniquely and positively correlated with gsand foliar N concentration. Multiple regression analyses showed that, when variability in SLA was controlled for, the (positive) partial slope for each predictor remained significant. In contrast, there was a negative correlation between gsand foliar N concentration such that, for any given Aa, leaves with a high gsallocated less N to foliage than leaves with a low gs. Foliar N concentration was negatively correlated with branch hydraulic conductivity, whereas gswas positively correlated with branch hydraulic conductivity. These relationships were also significant when variability in leaf area to sapwood area ratio, gsand SLA were controlled for in a multiple regression, suggesting that the relationships were unique and independent of other confounding factors. Trees with low water transport capacity were able to support a high Aaby increasing investment in foliar N. Resource substitution occurred such that there was a trade-off between gsand foliar N in relation to branch hydraulic conductivity. High Aacould be sustained through either a high branch hydraulic conductivity and hence high gsand a low allocation to foliar N, or the effect of a low branch hydraulic conductivity and hence low gscould be offset by a high allocation to foliar N. The results are discussed in relation to mechanisms for minimizing the negative effects of limited water availability on carbon gain. © 2008 Heron Publishing.
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