Sheep vegetation management for controlling competing vegetation in young conifer plantations in the central interior of British Columbia, Canada
In British Columbia, sheep vegetation management (SVM) is a relatively new technique; thus, limited data are available for examining its benefits on conifer growth. We collected field data from young mixed-conifer plantations of lodgepole pine (Pinus contorta) and hybrid spruce (Picea glauca × P. engelmannii) in blocks which had been grazed in 2005 and 2006 as well as from ungrazed blocks. Our main objective was to determine if sheep grazing had a significant effect on the growth of hybrid spruce. We measured stem diameter at 15 cm height above the root collar (D15) and cumulative internodal length (IL). Cumulative IL was calculated from the node corresponding to the year 2002–2010 (positions 2–10). The height to diameter ratio (height to the base of the leader (position 10)/D15; HDR) was calculated to determine if seedlings prioritized growth in terms of height or diameter. There was no significant grazing treatment effect on D15 and HDR when compared to the control treatment; however IL was significantly affected after the second grazing treatment in 2006 (position 6) and became increasingly important with time (positions 7–10). Based on our results, we suggest that SVM could be an effective method for controlling competing vegetation and thus, increase annual tree growth for areas with similar site characteristics as those found within the plantations sampled.
Evaluation of competitive effects of green alder, willow and other tall shrubs on white spruce and lodgepole pine in Northern Alberta
In boreal forests of western Canada, lodgepole pine (Pinus contorta Dougl. ex. Loud.) and white spruce (Picea glauca (Moench) Voss) often grow together with numerous tall shrubs such as green alder (Alnus crispa (Ait.) Pursh) and little-tree willow (Salix spp.). In an area south of Grande Prairie, Alberta, Canada, we examined the effects of shrubs, herbs and other trees on nutrient and light availability and growth of white spruce and lodgepole pine. For white spruce the best competition measure (tested against volume increments of the past 3 years) was visually estimated % ground cover times the height of the competitor (VCHT) with light (DIFN) ranking in third place. For lodgepole pine, DIFN was the best competition measure for predicting volume increment and the best competition index was again VCHT. Taller conifers had a stronger competitive effect than tall shrubs, with their effect on white spruce being larger than that on lodgepole pine. Comparison of the effects of alder and willow indicates that both species are having negative effects on growth of pine and spruce on these sites with green alder having a stronger influence on spruce than pine due to the smaller size of the spruce. Herbaceous cover was having more effect on white spruce than lodgepole pine and may be related to both their height and differences in rooting depth. The results did not show any significant relationship (p > 0.05) between nitrogen availability and cover of alder and willow and between conifer foliar nutrient concentrations and cover of alder andwillow.Ourstudysuggeststhat thecurrentAlbertaregenerationstandards maybeoverestimatingtheeffectthatcompetingvegetationhas on conifer growth since significant growth reduction occurs only at high shrub densities. Crown Copyright # 2007 Published by Elsevier B.V. All rights reserved.
Morpho-biometric Relationship, Relative Condition Factor and Meat Yield of Distant Scallop Bractechlamys vexillum (Reeve, 1853) in Asid Gulf, Philippines
Understanding the relationships of morphometric and biometric characters of a species allows the prediction of one trait from the other and generate a measure of relative condition. These relationships were studied for the Distant scallop Bratechlamys vexillum (Reeve, 1853) in Asid Gulf. Representative samples collected during the dry season (May 2018, n = 99) and wet season (September 2018, n = 100) were used to analyse these relationships through models of simple linear and power regression analyses, revealing allometric growth patterns. For both periods, it was revealed that shell width (SW) is a slightly better predictor than the height (SH) for total weight (TW) (R2 = 0.90 and 0.92) and the adductor muscle weight (AW) (R2 = 0.78 and 0.80). The strong functional relationship was also observed between TW and AW (R2 = 0.80 and 0.81). The relative condition factors (Kn) were high in both seasons. High meat yields were also observed in May (12.77 %) and September (14.26 %). The significant difference in meat yields (P < 0.05) can be a result of the seasonal difference manifested by the dynamics of energy partitioning during gametogenesis and spawning. These biological metrics are vital inputs in analysing mariculture prospects for the resource and a contribution to the scarce information on the biology of the species.