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51.
In 1988 an experiment was established to stimulate the effect of windthrow on low-and high-productivity forest types in coastal British Columbia. It was hypothesized that site productivity may be improved by mixing the upper 1 m of the organic matter and mineral soil. Results of this study indicated that soil mixing (1) slightly increased soil pH and temperature on both forest types after 2 and 5 years, (2) decreased all soil nutrient availability indices on the high productivity type after 2 years, but resulted in no difference from the control after 5 years, and (3) decreased microbial activity and cellulose loss rate and most soil nutrient availability indices on the low-productivity type after 2 and 5 years. Soil mixing greatly reduced Gaultheria shallon above-ground biomass on both low- and high productivity forest types, whereas biomass of Epilobium angustifolium and other plant species increased slightly on the high-productivity type after 2 and 5 vears. Tsuga heterophylla was taller on high-productivity type and on mixed plots in both types after 2 and 5 years. Thuja plicata was taller on the high-productivity type after 5 years only. The increased conifer growth measured on the mixed low-productivity type was attributed to higher levels of available nutrients due to reduced G. shallon competition. 相似文献
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The reaction during the early stage of photodiscoloration of constituents in western hemlock [Tsuga heterophylla (Raf. Sarg., Pinaceae] sapwood was investigated with chemical methods. The main photodiscoloring constituents, hydroxymatairesinol, allohydroxymatairesinol, -conidendrin, and oxomatairesinol, were used as substrates for light-irradiation experiments in vitro. The structures of photodiscoloration reaction products were elucidated by isolation and instrumental analyses and/or co-high-performance liquid chromatography analyses with authentic specimens. The experiment was undertaken to distinguish each series of liquid phases using chloroform, water (both including a trace of methanol), and methanol, and the solid phase. The reaction products allohydroxymatairesi (2), oxomatairesinol (3), -conidendrin (4), allo-7-methoxymatairesinol (5), 7-methoxymatairesinol (6), and vanillin (7) were isolated or detected in the reaction mixture of a hydroxymatairesinol system. The reaction products hydroxymatairesinol (1), 3, 4, 5, 6, and 7 were confirmed in the reaction system of allohydroxymatairesinol, which was an epimer of hydroxymatairesinol. Product 3 was confirmed from the -conidendrin system, and reaction product 7 was confirmed from oxomatairesinol. The photodiscoloration reaction of western hemlock sapwood could be initiated by the formation of phenoxy radicals from the respective constituents. The reaction was then presumed to progress via formation of a quinonemethide intermediate in many of them. It was suggested that the reactive species, such as phenoxy radical or quinonemethide intermediate, formed by lightirradiation might be converted to quinone derivatives and colored oligomers. Products 1, 2, 3, 4, and 7, formed from substrates such as hydroxymatairesinol, allohydroxymatairesinol, -conidendrin, and oxomatairesinol, were the same as the original metabolic constituents of western hemlock. Therefore it was concluded that the photodiscoloration of western hemlock depends not on the quantitative level of a few respective metabolites but, rather, on the coexistence of many metabolites.Part of this paper was presented at the 46th Annual Meeting of Japan Wood Research Society at Kumamoto, April 1996 相似文献
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Summary Feeding by the isopod, Oniscus asellus, produced changes in the sulfur constituents of leaf litter substrates (Acer negundo, A. saccharum, Fagus grandifolia, Picea rubens, and Tsuga canadensis). Isopod consumption of leaf litter generally accelerated the mineralization of carbon-bonded S and increased the formation of ester sulfate in all substrates. After the isopod egestion of A. negundo leaves, fecal decomposition over 6 weeks increased total S concentration from 68 to 120 mol S/g due to the catabolism of organic carbon. During the same period sulfate decreased from 34 to 20 mol S/g and carbon-bonded S increased from 34 to 100 mol S/g. Thus the total S pool in aged feces became enriched with organic S (83% of total S). Macroinvertebrate consumption accelerated the transformation of S constituents and the carbon-bonded S concentration approached that of the Oa organic horizon of a northern hardwood forest.Dedicated to the late Prof. Dr. M.S. Ghilarov 相似文献
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We compare forest floor microbial communities in pure plots of four tree species (Thuja plicata, Tsuga heterophylla, Pseudotsuga menziesii, and Picea sitchensis) replicated at three sites on Vancouver Island. Microbial communities were characterised through community level physiological profiles (CLPP), and profiling of phospholipid fatty acids (PLFA).Microbial communities from cedar forest floors had higher potential C utilisation than the other species. The F layer of the forest floor under cedar contained significantly higher bacterial biomass (PLFA) than the F layer under the other three tree species. There were differences in microbial communities among the three sites: Upper Klanawa had the highest bacterial biomass and potential C utilisation; this site also had the highest N availability in the forest floors. Forest floor H layers under hemlock and Douglas-fir contained greater biomass of Gram positive, Gram negative bacteria and actinomycetes than F layers based on PLFA, and H layers under spruce contained greater biomass of Gram negative bacteria than F layers. There were no significant differences in bacterial biomass between forest floor layers under cedar. Fungal biomass displayed opposite trends to bacteria and actinomycetes, being lowest in cedar forest floors, and highest in the F layer and at the site with lowest N availability. There were also differences in community composition among species and sites, with cedar forest floors having a much lower fungal:bacterial ratio than spruce, hemlock and Douglas-fir. The least fertile Sarita Lake site had a much greater fungal:bacterial ratio than the more fertile San Juan and Upper Klanawa sites. Forest floor layer had the greatest effect on microbial community structure and potential function, followed by site, and tree species. The similarity in trends among measures of N availability and microbial communities is further evidence that these techniques provide information on microbial communities that is relevant to N cycling processes in the forest floor. 相似文献
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Alexander M. Evans 《Journal of Sustainable Forestry》2013,32(3):223-240
ABSTRACT The hemlock woolly adelgid (HWA, Adelges tsugae Annand) an invasive exotic insect, may extirpate eastern hemlock (Tsuga canadensis (L.) Carrière) trees from native forests, but other hemlock species could be planted to occupy their ecological niche. This study tests two of the most likely replacement species candidates: western hemlock (T. heterophylla (Raf.) Sargent) and Chinese hemlock (T. chinensis (Franchet) Pritzel). Low survival rates, slow growth, and infestation by HWA of western hemlock in eastern hemlock forests shows that the western hemlock is not a likely candidate for planting in the northern portion of eastern hemlock's range. In contrast, Chinese hemlock grew at rates similar to eastern hemlock and did not show any signs of HWA infestation. In this study, damage from deer was a much bigger problem than growth reductions from HWA. 相似文献
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We conducted a multi-temporal spatial analysis of forest cover for a 9600 ha landscape in northern Wisconsin, U.S.A., using data from pre-European settlement (1860s), post-settlement (1931), and current (1989) periods. Using GIS we have shown forest landscape changes and trajectories that have been generally described in aggregate for the norther Great Lake States region. We created the pre-European settlement map from the witness tree data of the original federal General Land Office survey notes. The 1931 cover was produced from the Wisconsin Land Economic Inventory, and the 1989 cover map was based on color infrared photography. We used GIS to analyze 1) land area occupied by different forest types at different dates, 2) temporal transitions between dates and their driving proceses, and 3) successional trajectories with landforms and spatial associations of forest types. Over the 120 year period, forest cover has changed from a landscape dominated by old-growth hemlock (Tsuga canadensis) and hardwood forests (Acer saccharum, Betula alleghaniensis) to largely second-growth hardwoods and conifers. The former dominant hemlock is largely eliminated from the landscape. From 1860 to 1931, large-scale disturbances associated with logging were the dominant processes on the landscape. Early successional forest types covered much of the landscape by the 1930s. From 1931 to 1989, succession was the dominant process driving forest transitions as forest types succeeded to a diverse group of upland hardwood and conifer forest types. If successional trajectories continue, a more homogeneous landscape may develop comprised of both a northern hardwood type dominated by sugar maple, and a boreal conifer/hardwood forest. 相似文献
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