Species composition, effect radiation

Plant productivity is determined by factors such as plant species composition, moisture, soil fertility, growing season length, and solar radiation—many of which are affected by human activities. All else equal, increases in primary productivity and production of plant tissues will lead to increases in soil C stock, while decreases will lead to decreases in soil C stock. The rate of change in soil C stock is determined by the difference between C inputs and outputs, as well as the turnover times of the soil C, which are often not known. Here we review briefly how some environmental factors are expected to alter productivity and explore how the effects on stock depend on the number of soil carbon pools and their turnover times. 

M.L. Bothwell, D. Sherbet, A.C. Roberge, R.J. Daley (1993). Influence of natural ultraviolet radiation on lotic periphytic diatom community growth, biomass accrual and species composition short-term versus long-term effects. J. Phycoi, 29,24-35. 

First effects of radiation on species composition 50% Reduction in diversity of species... 

UV-B has various direct adverse effects on human health (skin cancer, immunosuppression, eye disorders), terrestrial plants and aquatic organisms [DNA alterations, photosynthesis inhibition, reduced growth, photoresponsiveness suppression (see Chapter 116)]. Moreover, due to the differences in UV-B sensitivity and adaptation among the various species, shifts in species composition may occur as a consequence of increased UV-B radiation, thus leading indirectly to alterations in ecosystems. ... 

Keiller DR, Holmes MG (2001) Effects of long-term exposure to elevated UV-B radiation on the photosynthetic performance of five broad-leaved tree species. Photosynth Res 67 229-240 Kogami H, Hanba YT, Kibe T, Terashima I, Masuzawa T (2001) C02 transfer conductance, leaf structure and carbon isotope composition of Polygonum cuspidatum leaves from low and high altitudes. Plant Cell Environ 24 529-538... 

Additives Effect on the Catalyzed Monomer Solution. Soluble dyes can be added to the catalyzed monomer solution to color the final wood-polymer composite. Any color of the visible spectrum can be added, browns to simulate black walnut, red and blues for national colors. The color emphasizes the grain structure of the particular species and combines with the polymer to add a three-dimensional depth not present in surface-finished wood. A dense black wood-polymer, so desirable for musical instruments, is difficult to obtain because of wood s light color and the tendency of the microstructure to chromatographically separate a dye of several components into its separate colors. Dyes have an inhibiting effect on the polymerization of wood-monomer composites, some more so than others. Additional catalyst can be added to overcome this inhibition, but in the radiation process of a given geometry additional time must be allowed for complete curing. 

C. Sebastian, R. Scheuerlein, D.-P. Hader (1994). Effects of solar and artificial ultraviolet radiation on pigment composition and photosynthesis in three Prorocentrum species. J. Exp. Mar. Biol. Ecoi, 182,251-263. 

The greenhouse effect takes place in the lower part of the atmosphere, called the troposphere. This phenomenon is an enhancement of natural processes which manages the radiation balance at the Earth s surface owing to a permanent increase of the GHG concentrations. For a better understanding of this problem we should consider the chemical composition of the troposphere and residence times of some species of interest, the temperature profile in the whole atmosphere and the increasing concentrations of greenhouse gases. 

Competition methods are employed for ratios of less than 5-10% when two isotopic species react at different rate a mixture of the two will change composition (except at 100% reaction) and yield a product having a different isotopic composition from the reactant. This will give us a measure of the isotope effect. Radioactive isotopes give specific radiation (counts/sec/mole) proportional to the ratio of radioactive over stable isotope radioactivity may be measured with a precision better than 1%. 

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