Cm. Kaelke et al., Trade-offs in seedling survival, growth, and physiology among hardwood species of contrasting successional status along a light-availability gradient, CAN J FORES, 31(9), 2001, pp. 1602-1616
Citations number
106
Categorie Soggetti
Plant Sciences
Journal title
CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE
To better understand the regeneration ecology of northern red oak (Quercus
rubra L.) in mesic forests, we compared its seedling growth and physiology
with those of two other hardwoods, differing in successional status, along
a gradient in light availability ranging from forest understories (2.6% of
full light) to small clearings (69% of full light). Oak's relative growth r
ate (RGR) closely resembled that of shade-tolerant sugar maple (Acer saccha
rum Marsh.), and the positive response of both to increasing light was mode
st, especially beyond a relative light availability of 15%. Intolerant trem
bling aspen (Populus tremuloides Michx.) outgrew the others when relative l
ight availability exceeded 5%, and its RGR increased more or less linearly
with increasing light. However, there was a rank reversal of RGR in deep sh
ade, where maple and oak had a higher RGR than aspen. This reversal was mir
rored by seedling demography, as aspen survival was comparatively high in s
mall clearings but negligible in deep shade. Aspen's low RGR and poor survi
val in low light were associated with a high rate of shoot dark respiration
and minimal allocation to starch reserves. Aspen's high RGR in openings wa
s attributed primarily to a high photosynthetic capacity per unit leaf mass
. Thus, differential growth and survival among species could be explained i
n part by trade-offs in attributes that promoted rapid growth in high light
at the expense of a favorable carbon balance in low light, or vice versa.
Oak's suite of traits facilitated a positive carbon balance in perhaps all
but the darkest understories. We suggest that the lack of persistence of oa
k seedlings in many understory environments may center around factors (e.g.
, vulnerability to biotic stresses) not directly related to carbon gain.