by Audrey Verreault | 30 January 2019
Published in International Journal of Remote Sensing 35(5): 1769-1785
This paper describes the development of a fully automated system for collecting high-resolution spectral data over a forested footprint. The system comprises a pair of off-the-shelf spectrometers in a custom-built thermal enclosure with a fixed off-nadir downward (target)-pointing fibre and upward-pointing fibre for irradiance measurement. Both instruments sample simultaneously via custom-written and user-controlled software during all weathers and sky conditions. The system is mounted on a 25 m eddy covariance scaffolding tower, approximately 7 m from a Scots pine forest canopy. The system was installed at the University of Helsinki’s SMEAR-II Field Station in Hyytiälä in March 2010 and has been operating continuously through a joint programme between the Universities of Edinburgh and Helsinki. The system was designed to capture diurnal and seasonal variation in vegetation light-use efficiency and fluorescence through the capture and analysis of well-defined narrow spectral features, but its implementation would permit the extraction of further optical signals linked to vegetation biophysical variables, and provide a continuous data stream with which to validate satellite data products including vegetation indices such as the photochemical reflectance index (PRI) as well as spectral indicators of solar induced fluorescence.
by Claire Morin | 30 January 2019
Published in Journal of Sustainable Forestry 32: 576-593
Height and diameter of white spruce clones were measured over two growing seasons in a forest nursery and for 4 more yr at two field sites. Clonal heritability (Hc2) was moderate and stable in the nursery, but decreased with age, reaching 0.26 and 0.11 for height and 0.14 and 0.04 for diameter, respectively, at the two field sites. Height exhibited weak to moderate Hc2 and strong genotypic correlations with the different growth characteristics. The strong age-age genotypic correlations (≥0.809) and nursery-plantation correlations (≥0.347) for height indicate that selection for height can be conducted at a young age thus reducing the costs of clonal tests.
by Claire Morin | 30 January 2019
Published in Forest Science 59(3): 345-358. https://doi.org/10.5849/forsci.11-146
In this study, we propose two volume and error variance estimators based on an integrated nonlinear mixed-effects stem taper model. The estimators rely either on a first- or a second-order Taylor series expansion. They were first tested through Monte Carlo simulations. The accuracy of the volume and error variance estimates was then tested against more than 1,000 observations. Empirical and nominal coverage of the confidence intervals were also compared under the assumption of a Gaussian distribution. For the volume estimators, results showed that the first-order estimator tends to slightly underestimate the volume, mainly because the stem taper model had random effects specified in a nonlinear manner. The second-order estimator was more accurate with neither under- nor overestimations of volume. For both the first- and the second-order variance estimators, the confidence intervals had empirical coverage that closely matches nominal coverage for probability levels >0.9. Although the proposed estimators require the stem taper model to predict the squared diameter of the cross section, they have the benefit of providing a tractable estimate of the variance. The covariances between different stem sections are quickly estimated because there is no need for repeated numerical integrations.
by Claire Morin | 30 January 2019
Published in New Forests https://doi.org/10.1007/s11056-013-9388-2
To assess the potential to integrate somatic clones (SC) of desired characteristics in production of high genetic quality seed, controlled crosses between different SCs of black spruce (Picea mariana (Mill) B.S.P.) were used to assess their suitability for the production of viable pollen, cones, seeds and seedlings. These SC produced male and female strobili at an early stage. Pollen, cones and seeds produced were characterized (mass, size, germination); their characteristics were similar to those produced by trees in natural forests or seed orchards. A maternal effect was demonstrated for the cone size and seed mass. Although seeds had excellent germination rates, the somatic biparental crosses were divided into three distinct groups with different germination curves using the Weibull function. Seeds from controlled crosses between different SC enabled the production of high morpho-physiological quality seedlings in a forest nursery. Using black spruce as a model, we showed, for the first time, that SC can be used as seed producers. These encouraging results open new perspectives on the tangible integration of somatic embryogenesis (SE) in the chain of seed, vegetative propagation (cuttings and SE) and production of plants for high productivity plantations. Controlled crosses can be made between SC with the desired characteristics (fewer large branches, fewer nodes, good growth, high wood density, performance, improved yield, etc.), vegetative propagules produced and deployed to clonal tests. After elimination of the worst performing SC, clonal tests can be converted into seed orchards that produce a new generation of seeds of high genetic quality. This will allow the rapid introduction of new materials in elite breeding programs of forest species.
by Marie-Claude Boileau | 30 January 2019
Published in Forest Ecology and Management 320: 1-5. http://dx.doi.org/10.1016/j.foreco.2014.02.017
Sugar maple (Acer saccharum Marsh., hereafter SM) dieback has been of concern in many stands of northeastern North America for decades. In acidic, base-poor forest soils, this phenomenon has often been attributed to calcium (Ca) deficiency. Corrective measures such as dolomitic lime addition (CaMg(CO3)2) have been tested to restore SM vitality in these ecosystems. However, few studies have evaluated the effect of Ca addition alone on SM. Furthermore, liming experiments have showed that the Mg content of lime could induce a nutritional antagonism which hinders potassium (K) uptake. This may have limited the response of SM to dolomitic lime application. To address these issues, two calcium fertilizers with negligible Mg content (CaCO3 and CaSO4.2H2O) were applied at rates of 1, 2 and 4 t Ca ha-1 on SM trees. After 7 years, foliar Ca nutrient concentrations of treated trees increased in both Ca treatments, reaching published concentration ranges for healthy SM trees. These increases were greater than those observed after a similar period in two nearby experiments in which CaMg(CO3)2 and CaCO3 were used at comparable or lower doses. Also, no nutrient antagonism was detected in the present study. Tree crown vigor and basal area growth were improved by the Ca treatments, but the magnitude of the growth response for trees treated with the CaCO3 fertilizer was far less than in the other nearby experiment where CaCO3 was also used. This strongly suggests that Mg nutrition is not a limiting factor in this ecosystem. The comparatively lower growth response of trees to Ca treatments in this study is unclear, but better growth conditions at the studied site, compared to the two other nearby experiments, may have played a role in this phenomenon. Long-term monitoring of these experiments seems warranted to clarify these issues.
