by Svetlana Savin | 30 January 2019
Published in Forest Ecology and Management 56: 13-28
Casuarina equisetifolia Forst. & Forst. plantations, established to stabilize sand dunes on the north coast of Senegal and thus protect inland agricultural areas, were sampled to determine if growth and yield were affected by microtopography. Microtopographical position, classified as interdune depressions, flanks, or summits, was found to have a highly significant effect on height, diameter, and volume growth. Maximum mean annual height increment was attained at Age 6 years (1.6 m year-1) in interdune depressions, at Age 7.5 (1.3 m year -1) on flanks, and at Age 8.5 (1.1 m year-1) on summits. Diameter distributions showed that the interdune depressions had a greater percentage of large diameter trees than flanks of summits. Maximum mean annual volume increment was 4.2 m3 ha-1 year-1 at Age 18 years for the interdune depressions, 2.0 m3 ha-1 year-1 at Age 29 for flanks, and 1.7 m3 ha-1 year-1 at Age 30 for summits. Thus, different rotation lengths can be recommended for specific microsites depending on microtopographical position and on whether fiber production or soil amelioration is the dominant management objective.
by Svetlana Savin | 30 January 2019
Final Report. April 29, 1996. 20 p.
by Svetlana Savin | 30 January 2019
Published in Canadian Journal of Forest Research 33: 2452-2459
Precommercial thinning is often used to control stand density in naturally regenerated balsam fir (Abies balsamea (L.) Mill.) stands. Early stand density control could have beneficial effects on longer term stand stability through a modification of stem shape and root development. To assess the effect of precommercial thinning, two thinned and two unthinned stands were selected. Root sections were collected at 25 cm from the centre of the stem for all major roots (diameter greater than 2 cm). A disk was also cut at breast height level. From these disks, response in radial growth was determined. Detailed root measurements were taken on the sample disks to assess treatment effect on the following variables: asymmetry in root cross-sectional area (CSA) distribution, individual root shape, as well as changes in root shape over time. A quick and pronounced response in root growth occurred. This response was greater than that observed in the trunk. No asymmetry in root CSA distribution was observed at the stand level. Trees allocated more to radial growth above the biological centre of the root both in treated and control stands, but this trend was increased by thinning. Roots also tended to develop T-beam shapes over time, both in control and thinned stands. Most roots initially did not possess an I-beam shape and did not develop one during the course of the study. According to our results, trees respond quickly to the new growing conditions created by thinning by increasing biomass allocation to parts of the roots where mechanical stresses are greater.
by André Boily | 30 January 2019
Published in Tree Seed Working Group – News Bulletin. 46(December) : 10-12.
by Claire Morin | 30 January 2019
Published in Plant Soil 300: 173-183
The decline of sugar maple (Acer saccharum Marsh.) in forest of north-eastern North America is an important environmental issue. In this study, relationships between, soil, wood and foliar chemistry were assessed for 17 stands distributed within a large area of the Québec sugar maple forest and that were growing on soils with a strong gradient of acidity and base saturation. There were many significant relationships between variables describing the acid-base status of the top-B soil (Ca and Mg concentrations, exchangeable acidity and base saturation) and Ca and Mn concentrations and Ca/Mn and Mg/Mn in tree tissues. Manganese was the element that showed the strongest inverse non-linear relationships with top-B soil base saturation with variance explanation of 71 and 65%, for wood and foliage, respectively. The 17 sites were divided in two groups according to their level of decline. The declining stands had significantly higher wood Mn and Mg concentrations and lower Ca/Mn ratios and significantly higher foliar Mn and lower Ca and Al concentrations. It was impossible to determine if these differences were a cause or a symptom of sugar maple health. However, the increase in Mn concentrations in tree tissues with increasing soil acidity, as well as the higher Mn concentrations in declining as compared to healthy stands suggest that Mn, as well as low Ca availability, could be an important contributing factor in the sugar maple decline.
