by Audrey Verreault | 16 November 2022
Published in Forests 2022(13): 1926. https://doi.org/10.3390/f13111926
Eastern spruce budworm (Choristoneura fumiferana Clem.) is considered the most important disturbing insect in coniferous stands in eastern North America. During an outbreak, spruce budworm can cause severe defoliation in balsam fir (Abies balsamea (L.) Mill.), which can affect wood properties such as moisture content and mechanical properties. This project aimed to assess the influence of the duration of spruce budworm defoliation on the wood quality of mature balsam fir trees. To do this, we studied sapwood proportion, decay, moisture content, mechanical properties and tracheid dimensions in stands that had suffered three, four or five years of defoliation. We also compared living and dead balsam firs and evaluated the change in wood properties with time. Our results showed that dead balsam firs suffered from a loss of wood quality rapidly after their death, particularly in terms of moisture content and decay in the sapwood. Sapwood proportion was similar between living and dead trees, but the sapwood of dead trees contained more decay and had a lower moisture content than living trees. Mechanical properties and tracheid dimensions were 10% and 4% lower in dead trees than in living trees. We did not observe any major differences in wood properties between the three durations of defoliation, suggesting that wood degradation occurs before that. The study did not make it possible to determine the optimal duration of defoliation to harvest the stands.
by Marie-Claude Boileau | 14 November 2022
Published in Forestry: An International Journal of Forest Research, vol. 94(5): 611–629.
Manual aerial photo interpretation is used as a cost-effective source of data for forest inventories; however, the process of photo interpretation is inherently subjective and is often undertaken by multiple photo-interpreters for a given forest management area. In contrast, airborne laser scanning (ALS) data enable characterization of forest structures in a systematic fashion with quantifiable levels of accuracy and precision that often exceed required targets and standards. Yet, the gains associated with the use of new technologies for forest inventory are difficult to measure because the quality of existing photo-interpreted inventories have rarely been quantified.
Using ALS data as a reference, the objective of this study was to quantify the precision of photo-interpreted estimates of forest stand height and canopy cover (CC). We examined forest inventories from three study sites in three different forest regions of Canada. Each of the study sites was located within a different provincial jurisdiction with unique photo interpretation standards and forest ecosystems. Stand-level estimates of forest height and cover were compared to reference estimates generated from the ALS data. Overall, our results indicated that precision was greater for photo-interpreted estimates of height. While the relationship between photo-interpreted estimates of height and ALS estimates of height were generally linear and consistent for all study sites, relationships for CC were non-linear. Precision for both stand height and cover varied by dominant species, inventory stand structure, age and ALS canopy complexity. In most cases, the difference between the photo-interpreted estimate and the ALS estimate was statistically significant. Also, the variability in photointerpretation precision as a function of the aforementioned factors was not consistent among our three study sites, indicating that site-specific forest conditions and photo-interpretation procedures influence the precision of photo-interpreted estimates. The influence of local forest conditions and interpretation procedures are therefore important considerations to quantify the potential relative gains in precision, which may be afforded by technologies such as ALS for forest inventory programs.
by Marie-Claude Boileau | 14 November 2022
Paru dans Canadian Journal of Forest Research, vol. 4, p. 1750-1757.
A shadow fraction method was previously developed for mapping forest attributes of northern black spruce forests. This paper evaluates application of the method to (i) balsam fir stands, (ii) stands with higher volume and biomass than those of previous studies, and (iii) stands with a higher composition of deciduous trees and steeper slopes. Models developed for new test sites in central Labrador and western Newfoundland were not statistically different from previous models for biomass, volume, and basal area. Relative root-mean-square errors (RMSEr) for central Labrador were slightly lower than those found in other test sites (RMSEr = 24%–29%) but higher for western Newfoundland (RMSEr = 37%–43%), attributed to the higher upper limit of measured attributes and increased presence of deciduous trees. Results suggest that reasonable estimates can be generated for conifer forests of northeastern Canada; however, an alternative solution is needed where mixed and deciduous stands prevail. Measurement of ground plots over a wider range of species composition and forest structure is recommended for broader application to northern boreal forests and to further assess the potential role of the shadow fraction method in national-scale inventory programs.
by Marie-Claude Boileau | 14 November 2022
Published in Forestry Chronicle, vol. 95(2), 101-112.
Canada’s forests have frequently been characterized using binary classifications such as intact/non-intact or managed/unmanaged. A more nuanced classification approach is needed to better understand the geography of forest management in Canada. The best way to represent Canada’s complex diversity of forest management regimes with a simple classification is to categorize according to ownership, protection status and tenure. We gathered federal, provincial and territorial geospatial datasets and used a binary decision tree approach in GIS to classify land into nine classes: (i) Protected, (ii) Restricted, (iii) Federal Reserve, (iv) Indian Reserve, (v) Treaty/Settlement, (vi) Private, (vii) Long-Term Tenure, (viii) Short-Term Tenure, and (ix) Other. These classes are broad; management intensity may vary considerably within classes. Not all forests in Long-Term Tenure or Short-Term Tenure areas are available for timber supply. Government regulations establish considerable reserve areas within forest management units where harvesting is not permitted. The resulting map dataset is current to 2017 and will need to be updated as land designations change.
by Marie-Claude Boileau | 14 November 2022
Published in Canadian Journal of Remote Sensing., vol 39. p. 217-231. https://doi.org/10.5589/m13-030
The aim of this study was to develop an imputing method to map forest stand attributes (height and volume) using panchromatic aerial photographs with a spatial resolution of 30 cm and Landsat images. The method was tested on several black spruce-dominated sites in Québec, Canada. The method involved four procedures: (i) measuring the shadow fraction from panchromatic aerial photographs; (ii) generating regression models between the shadow fraction and forest attributes; (iii) locally mapping the forest attributes as a grid layer (30 m × 30 m); and (iv) expanding the forest attributes from the local maps to a large study area using an imputation approach. Regression models between the shadow fraction and stand attributes were calibrated with ground sample plots and a series of 73 aerial photographs.
The portion of each aerial photograph that was used was restricted to its centre (between 6.2° and 11.3°) to improve goodness-of-fit. Small local maps of stand attributes were thus produced from the shadow fraction and used as the training dataset for an imputing approach, a k nearest-neighbours algorithm, with the aim of mapping forest attributes over a large area.
