by equipewp | 30 January 2019
Published in Agroforest Syst 86(3) : 433-442. The implementation of a management-protection program, using suitable cultivation practices, contributes to rehabilitating marginal areas prone to prolonged waterlogging and preserving biodiversity. Three hybrid poplar clones (‘I-488’, ‘Rimini’ and ‘D-64’) were tested to assess their degree of tolerance to waterlogging by imposing four water regimes over a 1 year period: control (C), non-preconditioned (NPr), and two levels of flood preconditioning (Pr10 and Pr20). During the 2nd year, waterlogging (1.9 ± 0.7 mg/lO2) was imposed on plants from NPr, Pr10 and Pr20 treatments for 60 days followed by drainage. (…)
by Claire Morin | 30 January 2019
Published in Canadian Journal of Forest Research 42: 1796-1809. https://doi.org/10.1139/x2012-125
Base cations (Ca, Mg, and K) are essential nutrients for forest growth. Many studies have reported important decreases in the soils of several forests in eastern North America, partly because of atmospheric acid deposition and forest harvesting. To quantify the impacts of these perturbations on forest base cations, accurate estimation of tree biomass and nutrient content is needed. However, most of tree nutrient contents are calculated with general allometric equations, leading to inaccurate estimates. We thus calculated tree biomass and base cation content for three common forest types in eastern Canada using site-specific allometric equations and compared them with those calculated with general allometric equations and nutrient concentrations of tree compartments taken from the literature. General allometric equations resulted in above-ground tree biomass estimates in the same range as ours (±15%), but the use of nutrient concentrations taken from the literature resulted mainly in overestimation of above-ground tree nutrient content (–13% to +81%), leading to inaccurate wood requirement estimates (–63% to +86%). Therefore, the development of site-specific equations to estimate above-ground tree base cation content is recommended.
by Marie-Claude Boileau | 30 January 2019
Forestry research paper No. 33E
Even though insect outbreaks have been known for centuries in Canadian forests, the economics of control measures was almost completely ignored till recently. This paper presents the highlights and main results of an economic study prepared in 1972 under the auspices of the Québec Department of Lands and Forests Research Service, concerning the feasibility of aerial spraying against spruce budworm. This study arrives at a general pest control policy by comparing nine spraying alternatives in terms of economic criteria. The marginal approach of economic analysis is used. One pre-condition set was that spraying policy must be integrated with other forest policies. The study is based upon certain assumptions concerning entomology, forest management, and economics.
One of the most economically feasible spraying options indicated an 8% rate of return on investment in terms of direct value saved (stumpage value only). It calls for the spraying of softwood and mixedwood stands, for two successive years, then a halt to spraying for two years, and so on till the end of the outbreak.
Without treatment, the minimum annual loss in the outbreak area in Québec could present, over the next forty year period, the following picture:
1- Over two million cunits of timber destroyed (5,6 millions cubic metres)
2- 12,6 million dollars in lost stumpage dues from public forests;
3- 14,7 million dollars in lost taxes;
4- 63,2 million dollars in lost salaries and wages;
5- 17 000 fewer jobs.
by Claire Morin | 30 January 2019
Published in Plant Ecology 213(6): 1027-1035 https://doi.org/10.1007/s11258-012-0062-0
In north-eastern North America, the recent red spruce decline has been linked to atmospheric pollution, notably acid rain, although climate was also advocated as a potential factor. A high resolution lake sediment pollen stratigraphy was obtained to elucidate long-term trends in tree-species abundance in a sugar maple-yellow birch forest. The reconstructed history (~250-1996 A.D.) showed a steady increase of red spruce after 1300 A.D., with a peak between 1600 and 1900 A.D. followed by a strong decline in the last century, while sugar maple and yellow birch experienced an opposite trend. Red spruce abundance reached its apogee during the cool Little Ice Age (LIA) and decreased abruptly when annual temperature in the region increased by 2 °C in the last 125 years. American Beech was much more abundant in the forest before the LIA, typifying a sugar maple-American beech forest as the dominant forest type during the Late Holocene. Our results suggest that climate warming has played an important role in the current red spruce decline, the latter having been initiated well before acidic depositions reached deleterious potential effects on red spruce. Climate warming probably acted as a long-term predisposing factor that was aggravated by atmospheric pollution, in the last decades.
by André Boily | 30 January 2019
Abstract of the paper published in Chen, Y.-R., G.E. Meyer et S.I Tu (eds). Proceeding of SPIE Vol. 5996, 599605 at the Optical Sensors and Sensing Systems for Natural Resources and Food Safety and Quality. October 23, 2005. Boston, Maine. 10 p. doi:10.1117/12.630522
Understanding the dynamics of the global carbon cycle requires an accurate determination of the spatial and temporal distribution of photosynthetic CO2 uptake by terrestrial vegetation. Stress factors may cause sub-optimal photosynthetic function resulting in down-regulation (i.e., reduced rate of photosynthesis). Photosynthetic down-regulation is related to changes in the apparent spectral reflectance of leaves. Present approaches to determine ecosystem carbon exchange rely on meteorological data as inputs to models that predict the relative photosynthetic function in response to environmental conditions inducing stress (e.g., drought, high/low temperatures).
This study examines the determination of ecosystem photosynthetic light use efficiency (LUE) from satellite observations, through measurement of vegetation spectral reflectance changes associated with physiologic stress responses. This approach is possible using the Moderate-Resolution Spectroradiometer (MODIS) on Terra to provide frequent, narrow-band measurements of high radiometric accuracy. Data from reflective MODIS ocean bands were used over land to calculate the Photochemical Reflectance Index (PRI), an index that is sensitive to reflectance changes near 531nm associated with vegetation stress responses exhibited by photosynthetic pigments. MODIS PRI values were compared with LUE calculated from values of CO2 flux measured at the overpass time at a flux tower located in a Douglas fir forest on Vancouver Island in Canada. Preliminary results show a relationship between MODIS PRI and LUE when using MODIS observations in the backscattering direction. These results compare well to previous work at a boreal aspen forest suggesting this approach may be generally useful.
