Document: CHR-3-29-2

Survival and growth of seedlings of 12 Chilean temperate rainforest trees in contrasting light environments: gas exchange and allocational correlates.

LUSK, C.* and A.L.DEPOZO

Universidad de Concepcie, Chile ¹

Abstract:
The dominant paradigm of tree life histories attributes contrasting suites of traits to "pioneer" and "non-pioneer" species, emphasizing strong interrelationships between growth, regenerative and life history traits. However, there is still disagreement as to the physiological determinants of some of the trade-offs involved. Furthermore, there has been little work on southern temperate rainforests, where life history variation may be less straightforward than that proposed by the prevailing paradigm. We measured survival and growth of seedlings of 12 Chilean temperate rainforest trees in two light environments (150 y 15 moles m^-2 s^-1), in order to examine diversity of seedling behaviour in this forest type, and to identify the physiological/morphological correlates of this variation. RGR and biomass allocation parameters were estimated by harvesting plants in both light treatments. RGR in high light was highly correlated (P < 0.0001) with photosynthetic capacity. Mortality in low light was positively correlated with light compensation point (P = 0.03) and with photosynthetic capacity (P = 0.02). Furthermore, high-light RGR was positively correlated with low-light mortality (P = 0.01). Neither mortality nor growth in either treatment was significantly correlated with any biomass allocation trait. Although the seedlings of long-lived light-demanding species showed similar low-light mortality to short-lived "classic" pioneers, the latter grew much faster in high light. Gas exchange traits appear to be major determinants of interspecific variation in seedling performance. However, the limited range of variation in light compensation points suggests that traits other than those which we measured are also probably important in determining shade tolerance differences. The heterogeneity evident among the shade-intolerant species suggests that a single axis of trait variation is insufficient to describe tree life history variation in Chilean temperate rainforests.

Keywords: gas exchange, LAR, RGR, SLA, tree life histories

This abstract is being presented at: 3:15 PM in session:
Oral Session #10: Light Relations in Plants.