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51.
Review of ground-based methods to measure the distribution of biomass in forest canopies 总被引:1,自引:0,他引:1
Dominik Seidel Stefan Fleck Christoph Leuschner Tom Hammett 《Annals of Forest Science》2011,68(2):225-244
? Context
Ecological research and an effective forest management need accurate information on the structure of the forest canopy to understand the biochemical, physiological and biogeochemical processes within a forest.? Research question
This paper reviews the currently available instruments for measuring the distribution of biomass within forest canopies. We compare the most well-established approaches and present the different measurable parameters. A special focus lies on the resolution of the obtained data.? Results
It was found that only 3D laser scanners offer data with the resolution required by ecologists, private landholders, the forest industry and the public to detect trends in tree growth patterns and canopy interactions in all three spatial dimensions. But data validation, data analysis and parameter extraction are still under development, and the price of the instrument is quite high.? Conclusion
Research should focus on the parameter extraction from terrestrial laser scanner data as this could allow the calculation of functional attributes for different sections of a canopy on a high spatial resolution. It could also help ecologists characterize the structure of forest stands in a quick and precise way. 相似文献52.
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55.
Walter R. Fischer 《植物养料与土壤学杂志》1990,153(2):93-95
The interpretation of K/Ca exchange isotherms by a simple GAPON equation K/Ca exchange isotherms of various soils can be described by a GAPON equation, where the coefficients being fitted to the measured values by iteration. The resulting values for the “labile potassium” are very similar to those of exchangeable K, whereas only 5–25% of the cec is involved in the short-term K/Ca exchange. 相似文献
56.
Michailov GV Sereda MW Brinkmann BG Fischer TM Haug B Birchmeier C Role L Lai C Schwab MH Nave KA 《Science (New York, N.Y.)》2004,304(5671):700-703
In the nervous system of vertebrates, myelination is essential for rapid and accurate impulse conduction. Myelin thickness depends on axon fiber size. We use mutant and transgenic mouse lines to show that axonal Neuregulin-1 (Nrg1) signals information about axon size to Schwann cells. Reduced Nrg1 expression causes hypomyelination and reduced nerve conduction velocity. Neuronal overexpression of Nrg1 induces hypermyelination and demonstrates that Nrg1 type III is the responsible isoform. We suggest a model by which myelin-forming Schwann cells integrate axonal Nrg1 signals as a biochemical measure of axon size. 相似文献
57.
Pasquarello A Petri I Salmon PS Parisel O Car R Toth E Powell DH Fischer HE Helm L Merbach A 《Science (New York, N.Y.)》2001,291(5505):856-859
We determined the structure of the hydrated Cu(II) complex by both neutron diffraction and first-principles molecular dynamics. In contrast with the generally accepted picture, which assumes an octahedrally solvated Cu(II) ion, our experimental and theoretical results favor fivefold coordination. The simulation reveals that the solvated complex undergoes frequent transformations between square pyramidal and trigonal bipyramidal configurations. We argue that this picture is also consistent with experimental data obtained previously by visible near-infrared absorption, x-ray absorption near-edge structure, and nuclear magnetic resonance methods. The preference of the Cu(II) ion for fivefold instead of sixfold coordination, which occurs for other cations of comparable charge and size, results from a Jahn-Teller destabilization of the octahedral complex. 相似文献
58.
Zhou O Zhu Q Fischer JE Coustel N Vaughan GB Heiney PA McCauley JP Smith AB 《Science (New York, N.Y.)》1992,255(5046):833-835
X-ray diffraction and diamond anvil techniques were used to measure the isothermal compressibility of K(3)C(60) and Rb(3)C(60), the superconducting, binary alkali-metal intercalation compounds of solid buckminsterfullerene. These results, combined with the pressure dependence of the superconducting onset temperature T(c) measured by other groups, establish a universal first-order relation between T(c) and the lattice parameter a over a broad range, between 13.9 and 14.5 angstroms. A small secondorder intercalate-specific effect was observed that appears to rule out the participation of intercalate-fullerene optic modes in the pairing interaction. 相似文献
59.
Stomatal opening: role of potassium uptake by guard cells 总被引:16,自引:0,他引:16
R A Fischer 《Science (New York, N.Y.)》1968,160(829):784-785
Stomata in isolated epidermal strips open in response to light plus air free of carbon dioxide when the strips are floated on potassium chloride solutions of low concentrations. This opening depends on the stimulation of active accumulation of potassium in quantities sufficient to account for the observed changes in solute potential of the guard cells. 相似文献
60.
Fischer MH 《Science (New York, N.Y.)》1919,49(1278):615-618