Revista Chilena de Historia Natural 84 (2): 269-277, 2011
RESEARCH ARTICLE
Effects of light availability and growth rate on leaf lifespan of four temperate
rainforest Proteaceae
Although comparative studies have revealed much about the environmental
correlates of leaf lifespan and its integration with other leaf traits, a comprehensive theory of leaf lifespan is still lacking.
The influence of growth rate on self-shading may be a key proximate determinant of both inter- and intra-specific variation
in leaf lifespans. If this were the case, we would expect leaf lifespans of fast growing light-demanding species to respond
more strongly to light environment than those of shade-tolerant species. We monitored growth and leaf survival of juvenile
trees of four temperate rainforest Proteaceae in southern Chile, in order to explore the influences of light environment and
self-shading on leaf lifespan. Leaf lifespans tended to decrease with increasing diffuse light availability, and slopes of these
relationships were steeper in two light-demanding species (Embothrium coccineum, Lomatia
hirsuta) than in two more shade tolerant species (Lomatia ferruginea, Gevuina avellana).
This pattern mirrored interspecific variation in relationships of height growth with light availability, height growth rates of
the two light-demanding species responding more strongly to light availability than did growth of L. ferruginea
and G. avellana. Path analysis suggested that light availability influenced leaf lifespans
primarily through the influence of growth on self-shading: when rate of leaf production was held constant by multiple
regression, light availability per se had no significant influence on leaf lifespans of any of the four species. However, 29 to
79 % of intraspecific variation in leaf lifespan remained unexplained by light environment and leaf production rate. If self-
shading is fact the main proximate control on leaf lifespan, information on the elevational distribution of photosynthetic
photon flux may enhance the explanatory power of studies of this nature.
Key words:
height growth,
LAI-2000, path analysis, self-shading, shade tolerance
