Colette Ansseau

Effects of repeated sewage sludge application on plant community diversity and structure under agricultural field conditions on podzolic soils in eastern Quebec.

In Quebec, municipal sewage sludge application on agricultural lands is relatively recent and there are many concerns related to potential contamination and loss of plant productivity. This study aimed at monitoring the impacts of repeated, long-term application of sewage sludge on agricultural lands under operating field conditions. Eight paired study sites (treated and control) in three regions of the Eastern Townships (Que., Canada) were selected. Vegetation surveys were carried out twice a season for 2 years and soil samples were collected. Diversity index (D), yield production and percentage of weeds were measured in each field. The average number of species per site and treatment varied from 10 to 36 but the differences between control and treated plots for all sites were not significant. The diversity indices significantly varied between sites due to original soil composition differences between locations. In some cases, significant differences in diversity existed between paired treated and control fields. However, weed percentage did not necessarily vary in those same fields suggesting that change in diversity did not lead to changes in number of weeds. Soil chemical composition showed that significant variation existed between sites but not between paired fields. Correlation performed between diversity, production, weed frequency and soil parameters showed that variation in D was negatively correlated with Mg and positively with pH. At the same time, the percentage of weeds was negatively associated with K, Ca and pH (P<0.05). Although sewage sludge produced little direct effect on the ecological parameters, analyses suggest that some soil chemical factors may affect plant diversity and percentage of weeds. These results indicate that plant community ecology may be affected by changes in environmental conditions but in a complex manner. Monitoring programs should be developed to evaluate the long-term impacts of repetitive sludge application on agricultural lands.

A semi‐empirical model to estimate the biomass production of forest canopies from spectral variables Part 1: Relationship between spectral variables and light interception efficiency

Abstract Empirical studies using remotely sensed data to estimate forest stand parameters have shown that the biological variable which is most closely functionally linked to the spectral response of the canopy is the leaf area index (LAI). The LAI is highly important for the photosynthetic functioning of the canopy since it has a dominant influence on the light interception capability or efficiency e(i). This efficiency depends on the LAI and on the optical properties of the canopy elements and it is also functionally linked to the canopy reflectance. Furthermore, this efficiency is linked to the biomass production of forest canopies since this latter is the result of photosynthesis, through which a fraction of the intercepted incident solar energy is converted into biomass. We propose a semi‐empirical model between ei and canopy reflectance (in terms of normalized difference vegetation index (NDVI)) which results from coupling semi‐empirical models of reflectance and light interception which are based o...

Analysis of boreal forest dynamics using the global vegetation index

The objective of this research is to characterize the dynamics of the boreal forest as defined by the period, duration and intensity of photosynthetic activity of the vegetation cover using composite images of the global vegetation index (GVI) derived from NOAA‐AVHRR data. The relationship between GVI data and climatic factors, in particular growing degree‐days and evapotranspiration, is also analyzed. Visible and near infrared AVHRR channels in the global database were corrected for sensor drift and atmospheric effects using the simplified atmospheric correction method (SMAC) developed at LERTS (Rahman and Dedieu, 1994). These corrected data were used to calculate GVI data from April 1985 to December 1991. The results demonstrate the promising potential of GVI data for characterizing the global dynamics of the boreal forest in the regions considered in this study (Eastern Canada, Alaska, Siberia and Finland). Observed variations of vegetation growth parameters of each region can be interpreted in terms o...

Comparing Carbon Pools and Tree Growth in Balsam Fir (Abies balsamea) and Black Spruce (Picea mariana) Forest Ecosystems Located Along a Climatic Gradient

Abstract: Carbon (C) content in several forest ecosystem pools, including trees, understory species, downed logs, litter, soil organic and mineral layers, and fine roots, and tree growth were compared in balsam fir (Abies balsamea) and black spruce (Picea mariana) ecosystems located along a climatic gradient in eastern Canada spanning regions that differed by 4 °C in mean annual temperature. A total of 19 experimental sites were established, 12 in balsam fir ecosystems and 7 in black spruce ecosystems. Diameter at breast height (dbh), height growth rate, and C contents in trees, understory species, downed logs, litter, and soil organic and mineral layers did not differ significantly between northern and southern experimental sites (P < 0.05). The only C pool that differed significantly among the regions was fine roots. Tree ring data collected on trees greater than 5 cm in dbh at all the sites were related to monthly climatic data between April and October, the active physiological season at the latitudes of the study. The relationships derived indicated that the differential effects of significant climatic variables along the climatic gradient were more important for black spruce than balsam fir. These results suggest that the changes in climatic conditions in the next 100 y may have a relatively small effect on the productivity and C allocation of both forest types when located within a range of climatic conditions similar to those of this study.

Analyse régionale des simulations climatiques du modèle canadien de circulation générale de l'atmosphère pour le territoire québécois

Abstract Current understanding of the possible nature of climatic change at the regional scale is limited by the spatial resolution of General Circulation Models (GCM). The use of GCM outputs without correction linked to the spatial variability of the variables can bring significant errors in their utilization at the regional scale. The potential of the Canadian GCM for regional applications in Quebec has been analysed by comparison to the climatic normals of temperature and precipitation, measured over the Quebec climatological network, on an annual and seasonal basis. This analysis has been undertaken with the support of a geographical information system (GIS) (PAMAP). In summary, a difference between the climatic normal and the GCM output has been estimated at 20% for temperature and 30% for precipitation. We present an analysis of a corrected regionalized scenario for the province of Quebec of the possible climatic change simulated by the Canadian GCM under the hypothesis of a doubling of atmospheric ...

INTÉGRATION DE LA TÉLÉDÉTECTION DANS UN SYSTÈME D'INFORMATION GÉOGRAPHIQUE POUR LA MODÉLISATION DE L'IMPACT CLIMATIQUE SUR LA FORÊT BORÉALE AU QUÉBEC

SUMMARYThe boreal forest is one of the largest biomes on the Earths surface and a major storehouse of organic carbon. It is of major economic importance to Quebec and similar northern regions, where it serves as the resource base of major industries such as timber, wildlife, and recreation. Because of its location, size, and ecology, the boreal forest is a high-risk area for the potential effects of global environmental changes.The object of the research project is to study the global transformations of the boreal forest ecosystem with regard to climate changes and to investigate synoptic remote sensing as a tool for quantifying bio-geophysical characteristics of the boreal forest biome.The analysis of the dynamics of its evolution is carried out using an ecological model (a “Gap” model such as the one proposed by Bonan, 1990) integrated into a geographic information system (GIS). The input parameters to the vegetation model consist of scenario simulations based on the general circulation model of the Ca...