Osvaldo Valeria

The use of ground penetrating radar for remote sensing the organic layer – mineral soil interface in paludified boreal forests

Black spruce forests that are located in the Clay Belt, within the boreal region of eastern North America, are prone to paludification. Paludification is a natural process where organic layer accumulates on the forest floor, leading to substantial decreases in forest productivity. This study assessed the ability of using ground penetrating radar (GPR) to remotely sense the organic layer – mineral soil (OL–MS) interface (representing organic layer thickness (OLT)), which has a major influence on the occurrence of paludification in this region. The two chosen sites for this study represented different types of soil and organic layer thicknesses that are linked to different degrees of paludification: low to moderately paludified (site A) and highly paludified (site B). At each site, GPR measurements were collected along three 40 m parallel transects at 20 cm intervals with 200 MHz antenna. GPR interpretations were compared with field manual probing measurements. Detection of this continuous interface was successful at site A (r = 0.93, P < 0.001), but mesic and humic horizon clay content limited radar depth penetration, rendering the OL–MS undetectable at site B. However, we found that GPR data, coupled with ground truth information, were effective in mapping the thickness of the organic fibric horizon (r = 0.79, P < 0.001) at site B, which could be considered as an indicator of the OLT in highly paludified areas. Overall, GPR appeared effective for mapping the OL–MS interface in the low to moderately paludified site, which is attractive for implementing forest management strategies that will help to stop the advance of paludification.

Monitoring the state of a large boreal forest region in eastern Canada through the use of multitemporal classified satellite imagery

Multitemporal classification of Landsat imagery was used to measure and monitor the state of the forest over a large area (11.6 million ha) of boreal forest in eastern Canada using four criteria for a 20 year period (1985–2005). The Enhancement-Classification Method was used in this study. Forty-eight thematic classes based on Canadas National Forest Inventory were identified, then grouped into 13 indicators, and reorganized within four main criteria: (i) forest versus nonforest land cover, (ii) forest development stage, (iii) forest cover type, and (iv) forest cover density. Validation based on 2973 high-resolution geo-referenced digital aerial colour photos of the 2005 classified images showed an overall accuracy of the four criteria of 83%, 68%, 58%, and 62%, respectively. The change in each indicator between 1985 and 2005 could be summarized as: (i) a decrease in productive forest area of 0.4% (approx. 43 000 ha); (ii) a 4.6% decrease in mature stand area, with a concomitant increase in areas classified as vegetated (1.3%) and regenerated (3.4%); (iii) concentration of harvesting pressure on coniferous and mixed stands with respective reductions of 8.2% and 0.8%, due to their conversion to deciduous stands; and (iv) an increase in low-density stands (3.1%) and a decrease in high-density stands (8.3%). These results demonstrate that medium-resolution (30 m) remote sensing tools can be used both to monitor the state of the boreal forest and to produce key indicators, which were extracted from the multidate Landsat satellite imagery.

Ecosystem management in paludified boreal forests: enhancing wood production, biodiversity, and carbon sequestration at the landscape level

Canada’s boreal forest represents an important contributor of the world’s wood supply industry. However, maintaining or increasing productivity of the boreal forest may be challenging in areas dominated by forested peatlands. Moreover, sustainable management of these forests must also consider other important aspects of the forest ecosystem such as biodiversity and carbon sequestration. To address these concerns, ecosystem-based management has been implemented in some Canadian jurisdictions, such as in regions where a large portion of the boreal forest is dominated by forested peatlands. The objectives of this paper are (1) to summarize our current understanding of how natural disturbances influence stand dynamics and biodiversity in forested peatlands, and (2) to review the main differences between natural and managed forest stands with respect to soil properties, stand productivity, understory plant communities. We also discuss how even-age management regime succeeds or fails to preserve old forests and how this loss affects both forest structure and habitat diversity at the landscape level. We conclude by showing how, in boreal forested peatlands, forest management could contribute to carbon sequestration and mitigate projected climate change.