Entity

Time filter

Source Type


Ducey M.J.,University of New Hampshire | Astrup R.,Norsk Institutt for Skog Og Landskap | Seifert S.,TU Munich | Pretzsch H.,TU Munich | And 3 more authors.
Photogrammetric Engineering and Remote Sensing | Year: 2013

Terrestrial lidar (TLS) is an emerging technology for deriving forest attributes, including conventional inventory and canopy characterizations. However, little is known about the influence of scanner specifications on derived forest parameters. We compared two TLS systems at two sites in British Columbia. Common scanning benchmarks and identical algorithms were used to obtain estimates of tree diameter, position, and canopy characteristics. Visualization of range images and point clouds showed clear differences, even though both scanners were relatively high-resolution instruments. These translated into quantifiable differences in impulse penetration, characterization of stems and crowns far from the scan location, and gap fraction. Differences between scanners in estimates of effective plant area index were greater than differences between sites. Both scanners provided a detailed digital model of forest structure, and gross structural characterizations (including crown dimensions and position) were relatively robust; but comparison of canopy density metrics may require consideration of scanner attributes. © 2013 American Society for Photogrammetry and Remote Sensing. Source


Lilles E.B.,University of Alberta | Lilles E.B.,Bulkley Valley Research Center | Purdy B.G.,University of Alberta | Purdy B.G.,Environment Canada | And 2 more authors.
Canadian Journal of Soil Science | Year: 2012

We examined height and basal area growth over time for trembling aspen and white spruce in plots along a salinity gradient at six naturally saline sites in northern Alberta, as a benchmark for forest productivity on reclaimed saline sites. We measured root distributions and analyzed foliage for ions, nutrients and carbon and nitrogen stable isotope ratios. Both species grew on soil conditions previously considered unsuitable for forest vegetation [pH>8.5; electrical conductivity>10 dS m-1, sodium adsorption ratio>13 at depth (50-100 cm)] yet there was little evidence of nutritional toxicities or deficiencies. Aspen basal area growth decreased 50% as salinity increased, but aspen was commercially productive (site index=22) on soils with electrical conductivity of 7.8 dS m-1 at 50-100 cm depth. Growth of white spruce seemed to be unaffected by salinity level differences, but 78% of white spruce site indexes were less than 13 and would be considered non-productive. Both species showed growth declines over time, compared with non-saline reference growth curves, and rooted primarily in the forest floor and top 20 cm of soil. This suggests that rooting limitations may constrain longer-term productivity of forests established on sites with salinity at depth. Source


Amoroso M.M.,CONICET | David Coates K.,British Columbia Ministry of forests | David Coates K.,Bulkley Valley Research Center | Astrup R.,Bulkley Valley Research Center | Astrup R.,Norwegian Forest And Landscape Institute
Forest Ecology and Management | Year: 2013

A mountain pine beetle (MPB) epidemic is currently ravaging large areas of interior British Columbia (BC) with significant implications for ecosystem services including future timber supply and community economic stability. Information is needed on future stand dynamics in areas of impacted forests that are unlikely to be salvaged logged. Of greatest concern are stands dominated by lodgepole pine (>50% timber volume). Predicting how surviving trees in these areas respond and grow and the timing and species composition of natural regeneration ingress is of critical importance for multiple forest values. We undertook a retrospective study in the Flathead Valley of southeastern British Columbia where an intense MPB epidemic peaked in 1979-1980. Our objective was to gain insight into stand recovery and stand self-organization as influenced by species-specific growth responses of different sized secondary structure trees (individual seedling, sapling, sub-canopy and canopy trees surviving the epidemic) and post-beetle regeneration dynamics. MPB mortality rates, the percent of basal area killed by beetles, varied from 42% to 100% with most stands between 60% and 80%. In general, all surviving secondary structure released but the extent of growth release exhibited species variability. Release of surviving canopy lodgepole pine trees was often dramatic and greatest in stands with high total stand MPB mortality rates. Ingress of natural regeneration was slow in the first few years after MPB attack but there was a strong pulse of recruitment 10-20. years post disturbance which then slowed considerably. Nearly 30. years after the MPB attack, the stocking and composition of the understories have changed dramatically. Overall, the occurrence of the MPB epidemic resulted in more structurally and compositionally diverse stands leading to multiple successional pathways different from those of even-age pine dominated stands. The recovery and self-organization of unsalvaged natural stands in the Flathead Valley was a complicated process. It has provided insights for future forest management in areas impacted by the current massive MPB epidemic ongoing for the past decade in western North America. © 2013 Elsevier B.V. Source


Clason A.J.,University of Alberta | Clason A.J.,Bulkley Valley Research Center | Macdonald S.E.,University of Alberta | Haeussler S.,Bulkley Valley Research Center | Haeussler S.,University of Northern British Columbia
Ecoscience | Year: 2014

Forests dominated by the endangered tree species whitebark pine (Pinus albicaulis) are threatened by multiple stresses (fire suppression, climate change) and disturbances (white pine blister rust [Cronartium ribicola], mountain pine beetle [Dendroctonus ponderosae]). To gain insight into how these ecosystems respond, we quantified vegetation change over 2 decades (21-29 y) in xeric and submesic P. albicaulis ecosystems near the northern edge of the species' range on the leeward side of the Coast Mountains of British Columbia, Canada. We compared changes in overstory and understory vegetation composition of these stands to changes in mesic, non-whitebark pine ecosystems in the same region. Multi-response permutation procedure (MRPP) analysis showed that the overstory of xeric whitebark pine ecosystems became compositionally similar to mesic ecosystems, i.e., there was increased dominance by Abies lasiocarpa or Tsuga mertensiana. Yet understory composition in xeric whitebark pine stands changed little and there was continued regeneration of P. albicaulis. Submesic whitebark pine stands developed a dense canopy dominated by T. mertensiana, and although their understories did not become compositionally similar to mesic ecosystems, there was minimal P. albicaulis regeneration. Understory stability in xeric and submesic whitebark pine ecosystems over 21-29 y suggests compositional resilience in these ecosystems to multiple stresses and disturbances. However, ongoing disturbance affecting both overstory and understory P. albicaulis might still result in the loss of this keystone species. Source


Filotas E.,University of Quebec at Montreal | Parrott L.,University of British Columbia | Burton P.J.,University of Northern British Columbia | Chazdon R.L.,University of Connecticut | And 10 more authors.
Ecosphere | Year: 2014

Complex systems science provides a transdisciplinary framework to study systems characterized by (1) heterogeneity, (2) hierarchy, (3) self-organization, (4) openness, (5) adaptation, (6) memory, (7) non-linearity, and (8) uncertainty. Complex systems thinking has inspired both theory and applied strategies for improving ecosystem resilience and adaptability, but applications in forest ecology and management are just beginning to emerge. We review the properties of complex systems using four well-studied forest biomes (temperate, boreal, tropical and Mediterranean) as examples. The lens of complex systems science yields insights into facets of forest structure and dynamics that facilitate comparisons among ecosystems. These biomes share the main properties of complex systems but differ in specific ecological properties, disturbance regimes, and human uses. We show how this approach can help forest scientists and managers to conceptualize forests as integrated social-ecological systems and provide concrete examples of how to manage forests as complex adaptive systems. © 2014 Filotas et al. Source

Discover hidden collaborations