Coops N.C.,University of British Columbia |
Tompaski P.,University of British Columbia |
Nijland W.,University of British Columbia |
Rickbeil G.J.M.,University of British Columbia |
And 3 more authors.
Ecological Indicators | Year: 2016
Most efforts to link remote sensing to species distributions and movement have focused on indirect estimates of traits based on components of physiological and functional biodiversity. Such a view reflects one perspective on the general needs (habitat) of species. However, information on the vertical and horizontal structure of habitat may play a critical role in defining what a suitable habitat is. The development and application of highly accurate airborne laser scanning (ALS) systems, which are capable of describing the three-dimensional distribution of vegetation, have significant potential value in deriving quantitative relationships between species distributions and their habitat structure. In this paper we review the use of ALS for biodiversity studies, and propose a three-dimensional index which captures the three main components of vertical and horizontal vegetation structure: height, cover, and complexity. Once developed, we apply the index across the forested area of the Canadian province of Alberta, and compare and contrast the differences across natural subregions and land cover types. We also demonstrate how the index can be used with biodiversity data, in this case examining patterns in avian species richness. We conclude with a discussion on the potential use of the habitat structure index with other biodiversity-related research. © 2016 Elsevier Ltd. All rights reserved.
Murphy P.N.C.,Teagasc |
Ogilvie J.,University of New Brunswick |
Meng F.-R.,University of New Brunswick |
White B.,Forest Management Branch |
And 2 more authors.
Ecological Modelling | Year: 2011
This article examines the utility of a digitally derived cartographic depth-to-water (DTW) index to model and map variations in drainage, vegetation and soil type and select soil properties within a forested area (40ha) of the Swan Hills, Alberta, Canada. This index was derived from a LiDAR (Light Detection and Ranging) derived digital elevation model (DEM), with at least 1 ground return per m2. The resulting DTW pattern was set to be zero along all DEM-derived flow channels, each with a 4ha flow-initiation threshold. Soil type (luvisol, gleysol, mesisol), drainage type (very poor to excessive), vegetation type (hydric to xeric) and forest floor depth were determined along hillslope transects. These determinations conformed more closely to the DEM-derived log10(DTW) variations (R2>60%) than to the corresponding variations of the widely used topographic wetness index (TWI) (R2<25%). Setting log10(DTW) thresholds to represent the wet to moist to dry transitions between vegetation, drainage and soil type enabled a high-resolution mapping of these types across the study area. Also determined were soil moisture content, coarse fragment and soil particle composition (sand, silt, clay), pH, total C, N, S, P, Ca, Mg, K, Fe, Al, Mn, Zn, and available Ca, Mg, K, P and NH4, by soil layer type and depth. Most of these variables were also more correlated with log10(DTW) than with TWI, with and without soil layer depth as an additional regression variable. These variables are, therefore, subject to topographic controls to at least some extent, and can be modelled and mapped accordingly, as illustrated for soil moisture, forest floor depth and pH across the study area, from ridge tops to depressions. Further examinations revealed that the DEM-produced DTW and TWI patterns complemented one another, with DTW delineating soils in relation to local water-table influences, and with TWI delineating where the water would flow and accumulate. © 2011 Elsevier B.V.
Chhin S.,University of Alberta |
Chhin S.,Michigan State University |
Hogg E.H.,Natural Resources Canada |
Lieffers V.J.,University of Alberta |
Huang S.,Forest Management Branch
Tree Physiology | Year: 2010
This study tests the hypothesis that ring growth in the upper stem portion of trees is affected by climatic conditions differently than rings formed at breast height (1.3 m). A total of 389 trees from a network of 65 lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) sites in Alberta were examined using detailed stem analysis in order to examine interannual patterns of basal area increment and volume increment at different positions along the stem. Growth at lower sections of the bole was mainly driven by temperature and moisture conditions in the seasons prior to the growing season in the year of ring formation, while upper stem growth was more related to conditions during the year of growth, i.e., temperature in the early summer, or moisture in late winter to early spring. This translates into increased allocation of wood to the lower stem when prior late summer conditions are cool and wet, prior winters are mild (warm with little snow) and early summer conditions in the year of ring formation are hot and dry.
Gendreau-Berthiaume B.,University of Alberta |
Macdonald S.E.,University of Alberta |
Stadt J.J.,Forest Management Branch
Ecological Applications | Year: 2016
Understanding processes driving mortality in forests is important for comprehension of natural stand dynamics and for informing natural disturbance-based ecosystem management. There has been considerable study of mortality in forests during the self-thinning phase but we know much less about processes driving mortality in stands at later successional stages. We addressed this through study of five 1-ha spatially explicit permanent plots in mature (111-186 yr old in 2012) Pinus contorta stands in the Canadian Rocky Mountains using data from repeated measurements over a 45-yr period, dendrochronological information, and point pattern analysis. We tested the hypothesis that these stands had completed the self-thinning/density-dependent mortality stage of succession. Contrary to our expectations, the self-thinning phase can persist for more than 140 yr following stand establishment. Our fiindings suggest this was attributable to prolonged post-fire establishment periods due to surface fires in three of the plots while in the other two plots moist conditions and slow growth most likely delayed the onset of competition. Several pieces of evidence indicated the importance of density-dependent mortality in these stands over the study period: (1) The diameter distribution of individuals changed from initially right-skewed toward normality as a result of mortality of smaller-diameter stems. (2) Individuals of lower canopy positions were proportionally more affected by mortality. (3) When compared to the pre-mortality pattern, surviving stems in all stands had an increasingly uniform spatial distribution. In two of the plots, recent windthrow and/or ingrowth initially hindered our ability to detect density-dependent mortality but our dendrochronological sampling and permanent plot data allowed us to untangle the different processes at play; in doing so we demonstrate for the first time how density-independent processes can mask underlying density-dependent mortality processes in older stands. Mortality of larger dominant canopy trees increased over the study period and mortality of dominant stems was a random process in all stands suggesting these stands were approaching the end of the self-thinning stage and that density-independent processes might soon become more important. Our results provide an improved understanding of mortality processes that can be applied to natural disturbance-based ecosystem management. © 2016 by the Ecological Society of America.
White B.,Forest Management Branch |
Ogilvie J.,University of New Brunswick |
Campbell D.M.H.,University of New Brunswick |
Hiltz D.,University of New Brunswick |
And 5 more authors.
Canadian Water Resources Journal | Year: 2012
With increasing scarcity of natural resources, there is a need to provide resource managers and planners with maps that reliably inform about areas vulnerable to hydrological risks, including areas with ephemeral to intermittent flows. This paper demonstrates that the newly developed Wet-Areas Mapping (WAM) process using LiDAR-based point cloud data addresses some of these needs. This is done by portraying local flow patterns, soil drainage, soil moisture regimes and natural vegetation type across mapped areas in a numerically robust and consistent manner. As a result, WAM-derived maps are useful for "surprise-free" operations planning in several areas of natural resource planning (forestry, parks and recreation, oil and gas extraction, land reclamation), and also serve as field guides for locating and delineating flow channels, road-stream crossings, wet areas and wetlands. © 2012 Canadian Water Resources Association.