Sapling growth as a function of light and landscape-level variation in soil water and foliar nitrogen in northern Michigan |
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Authors: | Richard K Kobe |
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Institution: | (1) Department of Forestry, Michigan State University, Natural Resources Building, East Lansing, MI 48824-1222, USA |
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Abstract: | Interspecific differences in sapling growth responses to soil resources could influence species distributions across soil
resource gradients. I calibrated models of radial growth as a function of light intensity and landscape-level variation in
soil water and foliar N for saplings of four canopy tree species, which differ in adult distributions across soil resource
gradients. Model formulations, characterizing different resource effects and modes of influencing growth, were compared based
on relative empirical support using Akaike’s Information Criterion. Contrary to expectation, the radial growth of species
associated with lower fertility (Acer rubrum and Quercus rubra) was more sensitive to variation in soil resources than the high fertility species Acer saccharum. Moreover, there was no species tradeoff between growth under high foliar N versus growth under low foliar N, which would
be expected if growth responses to foliar N mediated distributions. In general, there was functional consistency among species
in growth responses to light, foliar N, and soil water availability, respectively. Foliar N influenced primarily high-light
growth in F. grandifolia, A. rubrum, and Q. rubra (but was not significant for A. saccharum). In A. saccharum and A. rubrum, for which soil water availability was a significant predictor, soil water and light availability simultaneously limited
growth (i.e., either higher light or water increased growth). Simple resource-based models explained 0.74–0.90 of growth variance,
indicating a high degree of determinism. Results suggest that nitrogen effects on forest dynamics would be strongest in high-light
early successional communities but that water availability influences growth in both early successional and understory environments. |
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Keywords: | Forest dynamics Forest composition Forest communities Resource effects Species distributions Succession |
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