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PARENT SESSION
Oral Session # 38: Forest Ecology II: Soils, Carbon, and Nutrient Cycling.
Presiding: B Clinton
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 100.

Productivity and leaf/canopy traits for deciduous and evergreen conifers over a soil resource gradient.

Gerlach, John1, Walters, Michael*,1, 1 Michigan State University, East Lansing, Michigan, USA

ABSTRACT- Studies have shown that productivity can be similar for evergreen and deciduous conifers on a given site, but how productivity and related leaf and canopy traits change over soil resource gradients is less well known. For the deciduous species European larch (Larix decidua) and the evergreen species red pine (Pinus resinosa ), based on reported differences in leaf and canopy traits, we hypothesized a site quality by species interaction with larch having greater productivity at high soil resource availability and red pine having greater productivity at low soil resource availability. We tested this hypothesis with soil, vegetation, and productivity data collected from 27 geographically paired larch and pine plantations distributed over the Great Lakes region. Our gradient was characterized by autocorrelation of potential N mineralization, and nitrification with available soil water holding capacity (AWC). Over the entire range of AWC, larch had greater productivity (site index and net primary productivity), and there was a weak species by AWC interaction with larch site index increasing more with AWC than pine. Over the AWC gradient larch had greater % leaf N, and annual N loss, and lower area based leaf N, and canopy N mass than red pine. Foliar carbon isotope discrimination () indicated that larch was less water use efficient that pine over the AWC gradient, but did not vary with AWC. For both species, leaf N (both area and mass bases) was more strongly related to site index than any other leaf/canopy characteristic and leaf N increased with AWC. Our results do not support a productivity-resource availability tradeoff between larch and pine.

Key words: Larix decidua, Pinus resinosa, Forest productivity