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  • 1
    ISSN: 1432-1939
    Keywords: Key words Bear ; Nitrogen ; Nutrient flow ; Salmon ; Spruce
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We quantified the amount, spatial distribution, and importance of salmon (Oncorhynchus spp.)-derived nitrogen (N) by brown bears (Ursus arctos) on the Kenai Peninsula, Alaska. We tested and confirmed the hypothesis that the stable isotope signature (δ15N) of N in foliage of white spruce (Picea glauca) was inversely proportional to the distance from salmon-spawning streams (r=–0.99 and P〈0.05 in two separate watersheds). Locations of radio-collared brown bears, relative to their distance from a stream, were highly correlated with δ15N depletion of foliage across the same gradient (r=–0.98 and –0.96 and P〈0.05 in the same two separate watersheds). Mean rates of redistribution of salmon-derived N by adult female brown bears were 37.2±2.9 kg/year per bear (range 23.1–56.3), of which 96% (35.7±2.7 kg/year per bear) was excreted in urine, 3% (1.1±0.1 kg/year per bear) was excreted in feces, and 〈1% (0.3± 0.1 kg/year per bear) was retained in the body. On an area basis, salmon-N redistribution rates were as high as 5.1±0.7 mg/m2 per year per bear within 500 m of the stream but dropped off greatly with increasing distance. We estimated that 15.5–17.8% of the total N in spruce foliage within 500 m of the stream was derived from salmon. Of that, bears had distributed 83–84%. Thus, brown bears can be an important vector of salmon-derived N into riparian ecosystems, but their effects are highly variable spatially and a function of bear density.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 95 (1993), S. 164-170 
    ISSN: 1432-1939
    Keywords: Herbivore-plant interactions ; Foraging ecology ; Habitat selection ; Ruminants ; Cervus elaphus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We tested the idea that ruminants allocate their feeding time to habitat patches in relation to foraging efficiency. We used five tame red deer (Cervus elaphus) in an enclosure planted with four treatment of timothy grass (Phleum pratense) differing in their stage of growth. Older swards offered higher biomass but lower nutritional quality than younger swards. We observed time spent feeding in each treatment during each of seven trials. We measured goodness-of-fit between observed times and predictions from two alternative hypotheses differing in optimization strategy (maximizing versus matching), and a third, null hypothesis. We tested the hypotheses using two alternative currecies: digestible protein, and digestible dry matter or energy. Although digestible protein concentration and dry-matter digestibility were highly correlated (r=0.763, P〈0.001), the wider range of digestible protein made it the much more sensitive measure of forage quality. Distributions of feeding time closely matched estimated intake rates of digestible protein (R infPred sup2 =0.899) across all animals and trials. The other hypotheses were rejected. The results have important ecological implications in showing the underlying role of food in the selection of habitat by ruminants, and that simple, mechanistic models of forage intake and digestion can be scaled up to the level of animal behavioural choices.
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  • 3
    Publication Date: 2006-03-01
    Description: Interest in mixed red alder (Alnus rubra Bong.) conifer young-growth stands has grown in southeast Alaska, USA, because they appear to provide much more productive understory vegetation and wildlife habitat than do similar-aged pure conifer stands. We studied understory vegetation in nine even-aged young-growth stands (3842 years old) comprising a gradient of red alder conifer overstory composition, with red alder ranging from 0% to 86% of stand basal area. Conifers were Sitka spruce (Picea sitchensis (Bong.) Carr.), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western redcedar (Thuja plicata Donn ex D. Don). We measured understory biomass and net production (current annual growth) in each stand by species and plant part and estimated carrying capacity for black-tailed deer (Odocoileus hemionus sitkensis Cowan) with a food-based habitat model. Highly significant positive relations (P 〈 0.002) were found between red alder basal area and all of the following: total understory biomass (r2 = 0.743), net production of shrubs (r2 = 0.758) and herbs (r2 = 0.855), and summer carrying capacity for deer (r2 = 0.846). The high correlation between red alder and herbaceous production is especially important, because herbs are least abundant and most difficult to maintain in young-growth conifer forests of this region. Red alder offers prospects for increasing understory vegetation biomass and its food value for deer and other wildlife when included as a hardwood overstory species in mixed hardwoodconifer young-growth forests.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 4
    Publication Date: 2010-04-01
    Description: The effects of precommercial thinning on the understory vegetative cover of 16- to 18-year-old spruce–hemlock ( Picea sitchensis (Bong.) Carrière – Tsuga heterophylla (Raf.) Sarg.) stands were studied in seven replicate areas over seven growing seasons postthinning. Vegetative cover was analyzed at the class level, but species-specific effects were examined in relation to their value as food for Sitka black-tailed deer ( Odocoileus hemionus sitkensis Cowan). When compared with unthinned controls, thinned stands (3.6–6.3 m spacing) had significantly greater understory cover. However, all thinned spacings led to similar understory cover. Conifer cover recovered to about two-thirds of its prethinning level within seven growing seasons posttreatment. Understory nonconiferous cover increased during the first 2–4 years postthinning but began to decline with increasing conifer cover during the next 3 years, nearly reaching pretreatment levels by year 7. In unthinned understories, vegetative cover had declined and was significantly lower than that beneath thinned stands. Summer food resource values for deer were increased by thinning. Winter food resource values were increased by thinning for snow-free conditions but were unaffected for conditions when herb-layer forbs were buried by snow.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 5
    Publication Date: 2007-09-01
    Print ISSN: 0305-0270
    Electronic ISSN: 1365-2699
    Topics: Biology , Geography
    Published by Wiley
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  • 6
    Publication Date: 1987-03-01
    Description: Biomass of understory vegetation was sampled inside and outside four 19- to 21-year-old deer enclosures in the Alexander Archipelago of southeastern Alaska. Three sites were old-growth forests of western hemlock (Tsugaheterophylla (Raf.) Sarg.) –Sitka spruce (Piceasitchensis (Bong.) Carr.) and one site was an even-aged spruce–hemlock stand. In vitro dry-matter digestibility, fiber, nitrogen, and phosphorus concentrations of western hemlock seedlings and Alaska blueberry (Vacciniumalaskensis How.) inside and outside each exclosure also were compared. Analysis of variance indicated that Alaska blueberry and trailing bramble (Rubuspedatus Sm.) had greater biomass inside than outside the exclosures. No differences in chemical composition or digestibility of blueberry or hemlock inside and outside the exclosures occurred across sites. Results indicated that although deer may exert moderate to strong influence on the species composition and biomass of forest understories, their effect on dry-matter digestibility, fiber, nitrogen, and phosphorus concentrations of individual species may be negligible.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 7
    Publication Date: 1996-09-01
    Description: We studied six 1.2-ha stands, two each of three types of forest: (1) old-growth, riparian floodplain forest, (2) old-growth, upland forest, and (3) 40-year-old, red alder (Alnusrubra Bong.) riparian forest originating after clear-cut logging of floodplain forest. Sitka spruce (Piceasitchensis (Bong.) Carrière) dominated the old-growth riparian stands and shared dominance with western hemlock (Tsugaheterophylla (Raf.) Sarg.) in the uplands. Regeneration was predominantly spruce in the alder riparian, spruce and hemlock in the old-growth riparian, and hemlock in the upland stands. Total understory biomass and ground cover did not differ significantly between forest types, but species-specific biomasses did differ (P 〈 0.05). Understory of the upland forest was dominated by early blueberry (Vacciniumovalifolium Sm.) and Alaska blueberry (Vacciniumalaskensis How.), while that of both riparian types was dominated by devilsclub (Oplopanaxhorridum (Sm.) Miq.). Other species-specific differences occurred in forbs (three species) and mosses (three species). Contrary to typical stand age–understory relations in upland conifer forests of the region, the understory of the 40-year-old red alder stands was very species rich and productive.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 8
    Publication Date: 1988-01-01
    Description: The relationships between seral stage and nutrient and organic composition of five plant species used as forage by Sitka black-tailed deer were investigated in hemlock–spruce forest in southeastern Alaska. One shrub, three forbs, and one conifer species were collected during May, July, and October to ascertain differences among seral stands in seasonal patterns of nutrient levels, in vitro dry matter digestibility, astringency, and the concentrations of phenolics, terpenes, total nonstructural carbohydrates, and cyanide. In the shrub and forbs, concentrations of N, P, and K tended to be higher in leaves from forested than from open clear-cut areas, and higher in May than in July and October. These nutrients tended to covary in an opposite manner to Ca, Mg, and Na and in a similar manner to the trace elements Cu, Zn, Mn, and Fe, although these patterns were inconsistent. In these species there was also a general pattern of higher levels of total nonstructural carbohydrates, astringency, and phenolics in the three young open stands than in the shaded forest understories of the two oldest stands. Dry matter digestibility did not differ across stands but did vary seasonally. The among-stand differences in foliage chemical composition may have resulted from differences in the availability of light. While seral stage affected both the inorganic and organic quality of understory forage species, the combined results suggest that the impact on N economy of deer is greater than that on their energy economy.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 9
    Publication Date: 1993-01-01
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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  • 10
    Publication Date: 1999-12-10
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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