Species patterns in foliar nitrogen concentration, nitrogen content and 13C abundance for understory saplings across light gradients (original) (raw)

Plant and Soil, 2009

Abstract

ABSTRACT Soil nitrogen (N) supply and uptake by regenerating trees is an important ecosystem attribute but difficult to quantify in partial-cut forests where light availability varies. The foliar attributes of N concentration (N%) and N per unit area (Na) may help characterize the influence of soil nutrition, but ideally the relationship between soils and foliage would be tested separately by species across well-defined light gradients. To do this, we examined foliar attributes of four tree species across gradients of light availability in 12year-old partially-cut forests in northwest British Columbia, Canada. There were no differences in forest floor or mineral soil N mineralization rates across the light gradients, and for western hemlock (Tsuga heterophylla) and hybrid white spruce (Picea glauca x sitchensis), this consistent level of soil N supply corresponded with unchanging foliar N%. In contrast, foliar N% of Betula papyrifera (paper birch) and Thuja plicata (western redcedar) declined with shading, perhaps due to shifts in root-shoot biomass allocation for B. papyrifera, and climatic constraints on shade tolerance for T. plicata. Leaf δ13C approached an asymptote at approx. 40% full light for the coniferous species, but increased linearly with light for B. papyrifera. Foliar Na was linearly correlated with leaf δ13C for three species, reflecting the dual effect of light and nutrition on photosynthesis processes, and suggesting that foliar Na may be a simple parameter to integrate both resource constraints on regenerating saplings. These results demonstrate both support for and limits to foliar attributes among species in isolating soil N effects against light constraints in partial-cut forests.

Robert Guy hasn't uploaded this paper.

Let Robert know you want this paper to be uploaded.

Ask for this paper to be uploaded.