Interspecific variation in sapling mortality in relation to growth and soil moisture

Citation
Jp. Caspersen et Rk. Kobe, Interspecific variation in sapling mortality in relation to growth and soil moisture, OIKOS, 92(1), 2001, pp. 160-168
Citations number
38
Categorie Soggetti
Environment/Ecology
Journal title
OIKOS
ISSN journal
00301299 → ACNP
Volume
92
Issue
1
Year of publication
2001
Pages
160 - 168
Database
ISI
SICI code
0030-1299(200101)92:1<160:IVISMI>2.0.ZU;2-8
Abstract
To examine the causes of landscape variation in forest community compositio n we have quantified sapling mortality as a function of growth and soil moi sture for seven dominant species in transition oak-northern hardwood forest s of the northeastern USA. We located saplings in sites that encompassed a wide range of variation in soil moisture and light availability. In mesic c onditions, the probability of mortality decays rapidly with increasing grow th among shade tolerant species and more gradually among shade intolerant s pecies: the rank order of survivorship at low growth rates is Tsuga canaden sis > Fagus grandifolia > Acer saccharum > Fraxinus americana > Acer rubrum > Quercus rubra > Pinus strobus. The relationship between probability of m ortality and growth does not vary with soil moisture among species insensit ive to drought: Tsuga canadensis, Quercus rubra, and Pinus strobus. However , probability of mortality increases substantially with decreasing soil wat er availability for the other four species. Acer saccharum and Fagus grandi folia have high mortality rates under xeric conditions even when their grow th is not suppressed. Acer rubrum and Fraxinus americana exhibited a steady but more gradual increase in the probability of mortality with decreasing soil moisture. Among the five deciduous hardwood species me examined there is a weak inverse relationship between the ability to survive growth suppre ssion, a measure of shade tolerance, and the ability to survive in xeric co nditions, a measure of drought tolerance. Tsuga canadensis, however, is tol erant of growth suppression and exhibits high survivorship in xeric conditi ons, while Pinus strobus is intolerant of growth suppression but insensitiv e to soil moisture. Species differences in water-dependent mortality are co nsistent with the species distributions across landscape gradients of soil water availability.