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Resultados 301-310 de 347
The effects of acid precipitation and ozone on the ectomycorrhizae of red spruce saplings
1998
Roth, D.R. (Cornell Univ., Ithaca, NY (USA). Dept. of Natural Resources) | Fahey, T.J.
Phosphine by bio-corrosion of phosphide-rich iron Texto completo
1998
Glindemann, Dietmar | Eismann, Frank | Bergmann, Armin | Kuschk, Peter | Stottmeister, Ulrich
Phosphine is a toxic agent and part of the phosphorus cycle. A hitherto unknown formation mechanism for phosphine in the environment was investigated. When iron samples containing iron phosphide were incubated in corrosive aquatic media affected by microbial metabolites, phosphine was liberated and measured by gas chromatography. Iron liberates phosphine especially in anoxic aquatic media under the influence of sulfide and an acidic pH. A phosphine-forming mechanism is suggested: Phosphate, an impurity of iron containing minerals, is reduced abioticly to iron phosphide. When iron is exposed to the environment (e.g. as outdoor equipment, scrap, contamination in iron milled food or as iron meteorites) and corrodes, the iron phosphide present in the iron is suspended in the medium and can hydrolyze to phosphine. Phosphine can accumulate to measurable quantities in anoxic microbial media, accelerating corrosion and preserving the phosphine formed from oxidation.
Mostrar más [+] Menos [-]Pollution prevention in Colorado commercial greenhouses
1998
Panter, Karen L. | Newman, Steven Earl | Waskom, R. M (Reagan McTier)
Comparison of soil thermal regimes in a deforested area with various grass cover in the Beskids Mts. [Czech Republic]
1998
Tuma, I. (Akademie Ved, Brno (Czech Republic). Ustav Ekologie Krajiny)
The studies of grass communities, which spread in deforested areas, also involved observations of soil thermal regimes. Three sites were chosen in order to determine differences in diurnal and seasonal variations of soil temperatures: (1) open site (barren) without plant cover, (2) site covered by a young, lower and thinner stand of Avenella flexuosa, and (3) old, dense stand of Calamagrostis villosa with a layer of plant litter on the soil surface. Soil temperatures were measured at the soil surface and in the soil depth of 5 and 10 cm. In summer months, the greatest differences in maximal temperatures recorded at the soil surface and at the 5, 10 cm depth between the bare site and the old stand of C. villosa represented 21.6, 15.9, 12.4 deg C, respectively. Soil temperatures measured in the bare plot in autumn months were lower than those in grass stands.
Mostrar más [+] Menos [-]The life history strategy reflected in morphology, biomass allocation and standing crop of Athyrium distentifolium
1998
Fiala, K. | Tuma, I. (Akademie Ved, Brno (Czech Republic). Ustav Ekologie Krajiny) | Pande, K.
Mineral soil nitrogen concentration in grass stands after deforestation
1998
Zahora, J. (Mendelova Zemedelska a Lesnicka Univ., Brno (Czech Republic))
Ammonium and nitrate concentrations in soil were determined in the initial stage of grass stand formation and in old closed grass stands (Avenella flexuosa, Calamagrostis villosa). Higher concentrations of both ammonium and nitrate ions were found in the 0-10 cm soil layer in comparison with the deeper soil layer of 10-20 cm. The amounts of NO3-N and water-soluble NH4+N generally represented only a small part of total mineral nitrogen in samples just removed. Presented data indicate seasonal fluctuations in ammonium and nitrate concentrations in soil.
Mostrar más [+] Menos [-]Athmospheric deposition and soil solution chemistry on plots of third monitoring level in the Sance watershed, Beskids Mts. [Czech Republic]
1998
Moravcik, P. (Ustav pro Vyzkum Lesnich Ekosystemu, Jilove u Prahy (Czech Republic))
Research of basic issues of supraregional biocentre in Knehyne - Certuv Mlyn, the Moravian-Silesian Beskids Mts. [Czech Republic]
1998
Tesar, V. (Mendelova Zemedelska a Lesnicka Univ., Brno (Czech Republic). Fakulta Lesnicka a Drevarska)
The planned supraregional biocentre (SRBC) is a support to the system of landscape ecological stability. The sense of this long-term complex project consists in learning features of the ecotope and dynamics of the forest in its present natural and cultural forms and in all existing stages. A draft management plan will be worked out on this basis for the planned SRBC forest area of 1000 hectares, focused on the dynamic ecological stability.
Mostrar más [+] Menos [-]Evaluation of the water chemism during the flood wave of July 1997 in the Cervik and Mala Raztoka catchment areas in the Beskids Mts. [Czech Republic]
1998
Lochman, V. (Vyzkumny Ustav Lesniho Hospodarstvi a Myslivosti, Jiloviste-Strnady (Czech Republic)) | Chlebek, A. | Jarabac, M.
Investigation of the spruce stand radiation regime
1998
Tomaskova, K. (Mendelova Zemedelska a Lesnicka Univ., Brno (Czech Republic). Lesnicka a Drevarska Fakulta)
Radiation regime is the important part of the energy flow through the stand structure. The goal of the radiation regime studies in the forest stand is to create and develop the technology for radiation measurements and to estimate the impacts of stand density on the radiation regime. The experiment is carried out the Experimental research site Bily Kriz in the Moravian - Silesian Beskydy Mts. with a Norway spruce monocultural stand. Intensities of photosynthetic active radiation, global radiation and intensities of incident and transmitted photosynthetic active radiations through the stand were measured.
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