Leaf-level gas exchange and scaling-up of forest understory carbon fixation rates with a ?patch-scale? canopy model

Residual vegetation importance to net CO2 uptake in pine-dominated stands following mountain pine beetle attack in British Columbia, Canada

“…Explanations for the differences in the relative importance of these two sources of variation at the two sites could have resulted from greater patchiness in vegetation at MPB-06. Wedler et al (1996) found understory LAI to be highly variable (1.06-3.25) due to the patchy structure of their forest system; those values are higher, but similar in variability, to the range of LAI encountered across our sites, for which mean broadleaf understory vegetation LAIs at MPB-06 and MPB-03 were 0.48 and 1.08, respectively (Supplementary data, Appendix C). While the ranges in LAI between the two sites were high for single species and aggregated vegetation components, they were less so for the cumulative total LAI for the sites (1.51 for MPB-03 versus 1.36 for MPB-06).…”

“…For example, in two separate studies investigating the contribution of understory vegetation to NEP in even-and uneven-aged pine stands, understory vegetation comprised between 20-27% and 25-35% of total NEP in a 30-year-old Scotch pine (Pinus sylvestris) plantation in northern Germany (Wedler et al, 1996) and in 20-to 80-year-old mixed slash and longleaf pine (Pinus elliottii and Pinus palustris, respectively), stands in Florida (Powell et al, 2008), respectively. In a 13-year-old ponderosa pine (P. ponderosa) stand, understory vegetation accounted for up to 39% of total GEP (Misson et al, 2007), while in a 6-year-old planted sub-boreal clearcut, non-tree vegetation accounted for $86% of GEP (Pypker and Fredeen, 2002b).…”

“…There has been little study on the potential mitigation of C loss to the atmosphere due to enhanced growth of surviving residual overstory and understory vegetation, however. In particular, understory vegetation is often ignored in ecosystem C flux modelling due to complex and variable micro-climate conditions, heterogeneous forest structure, species diversity, and a poor understanding of the physiological response function in these many species and sizes of plants (Wedler et al, 1996).…”

Micro- and mesoclimatology

“…Work on forests has focused on evapotranspiration (Bernhofer et al, 1996a;Holmgren et al, 1996;Joss and Graber, 1996;Sturm et al, 1996), including water vapour flux from the forest floor and understorey (Wedler et al, 1996a; and transpiration estimated by xylem sap flow (Granier et al, 1996a;Ko È stner et al, 1996). In addition, many studies have treated CO 2 exchanges and photosynthesis (Bernhofer et al, 1996b;Joss and Graber, 1996;Lee et al, 1996;Sala and Tenhunen, 1996;Wang, 1996;Wang, K. Y. et al, 1996;Wedler et al, 1996a).…”

The relative photosynthetic contribution of old and new fronds of the wintergreen fern Dryopteris carthusiana, Ontario, Canada1

“…Also, some fern species play an important role in the understory by acting as ecological filters effectively limiting regeneration and growth of some tree species (George and Bazzaz 1999a, 1999b, Engelman and Nyland 2006. More generally, forest understories are important for regulating decomposition and nutrient turnover (Wedler et al 1996).…”