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
Effects of temperature on intra-annual dynamics of tree-ring formation in conifers of the Alpine timberline.
Rossi, Sergio*,1, Deslauriers, Annie1, Anfodillo, Tommaso1, 1 Università degli Studi di Padova, Padova, Italy
ABSTRACT- Histological analyses were used to describe the timing and dynamics of tree-ring formation in Larix decidua Mill., Pinus cembra L. and Picea abies (L.) Karst. at the timberline in the Eastern Alps. Measurements were taken in two sites with different altitudes and aspects. Wood micro-cores, including the most recent tree-rings, were collected weekly during the 2002-2004 growing seasons. Cross-sections were stained with cresyl fast violet and observed with visible and polarized light to differentiate xylem cells of the growing tree-ring. The number of cells in the cambial zone, radial cell enlargement, secondary wall thickening and mature xylem were counted and the number of days spent in each differentiation phase was estimated. Overall patterns of cambial activity and tree-ring formation appeared to be similar among species, although with 1-2 weeks delay. Tree-ring formation lasted from May to October, producing an average of 2-3 cells per week in L. decidua and P. cembra P. abies produced the highest radial number of cells with 4-5 cells per week. In the colder site (N exposure), a reduction in xylogenesis of 2-4 weeks and fewer cells in the tree ring were observed for all species. Late-persisting snow cover and low soil temperature seemed to be critical factors in determining the onset of cell differentiation. Air temperature significantly affected xylem cell production and, among the different species, P. abies seemed to be the most sensitive. On the contrary, rainfall, with a regular distribution during summer, did not seem to be a constraint to xylogenesis.
Key words: Wood formation, Alpine timberline, Temperature, Precipitation