PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Intra-annual xylem development in seven boreal tree species.
Ko Heinrichs, Derrick1, Tardif, Jacques1, Bergeron, Yves2, 1 Centre for Forest Interdisciplinary Research, University of Winnipeg, Winnipeg, Manitoba, Canada2 Chaire industrielle CRSNG-UQAT-UQAM en aménagement forestier durable, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec, Canada
ABSTRACT- Detailed anatomical investigations of tree-ring growth throughout the growing season are becoming more frequently used in dendroclimatology. However, notably missing are studies examining North American boreal species and multiple-species comparisons growing under similar ecological conditions. Intra-annual xylem development was studied by repeatedly taking microcore tree stem samples throughout the growing season from seven boreal tree species growing on an island in Lake Duparquet, Québec. Additionally, band dendrometers were installed on each tree to record stem circumference fluctuations, and numerous sensors recorded local climatic variables. The species examined were Abies balsamea, Betula papyrifera, Picea glauca, Picea mariana, Pinus banksiana, Pinus resinosa, and Thuja occidentalis. Weekly microcore samples were processed for image analysis, allowing cell and ring characteristics to be measured. This study has three objectives, i) to compare seasonal xylem development of seven boreal tree species, ii) to assess growth-climate associations, and iii) to provide fine scale calibration for band dendrometers. Cambial activity was observed in all species on May 16, 1999, when sampling began. A. balsamea and P. resinosa were the first species to produce a complete tangential file of xylem cells (late May), while B. papyrifera was the latest (early June), with a range of 17 days among the species. Comparison of xylem production and development among species over the growing season was conducted using eight variables per species. Each variable was modelled using a Gompertz function. Typical sigmoidal curves were characteristic of ring width, number of cells, number of earlywood cells, maximum wall thickness, and maximum wall to lumen ratio, over the growing season. Alternately, minimum lumen area, minimum lumen length, and minimum cell length each generally resembled a negative exponential curve. Growth and developmental rates were found to be mostly similar among species. Cell production was found to be 90% complete as early as the first week of August for P. glauca and T. occidentalis, while both P. mariana and P. resinosa were latest (the first week of September).
Key words: boreal tree species, xylem cell production, gompertz function, growth-climate associations