International Programs

Gaps in the forest canopy allow more light to reach the understory. Since light in the understory is heterogeneous, understanding the physiological processes in gaps and non-gaps will improve estimates of carbon balance. This research outlines an approach for defining carbon balance for Salal (Gaultheria shallon Pursh.), a dominant understory shrub in Pacific Northwest old growth forests, growing in gaps and non-gaps.
The carbon balance of salal foliage was estimated using a three-step approach. Ambient photosynthesis of salal was surveyed in gaps and non-gaps using a LiCor Photosynthetic Gas Exchange System. The LAI and percent cover of salal in gaps and non-gaps was measured using a species/area curve and the line intercept method. Finally, leaf-based measurements were scaled to determine stand-level carbon use of salal in and out of gaps.
I hypothesized that photosynthetic capacity and respiration value differences between gap and non-gap salal foliage could be accounted for by water potential and nitrogen content measurements. To further characterize salal in gaps and non-gaps in the understory, sun/shade leaf characteristics such as leaf mass to leaf area ratios, light curves and A/Ci curves were compared.
Scaling from individual plant based estimates to stand-level estimates show the importance of gaps in the understory carbon balance. While salal covers the forest floor equally, the multileveled leaf-canopy of salal in gaps and the higher photosynthetic capacity of salal foliage in gaps contribute to the larger carbon balance role that salal foliage in gaps has when compared to salal foliage in non-gaps.