The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Rainer Kurmayer - One of the best experts on this subject based on the ideXlab platform.
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Variation in peptide Net Production and growth among strains of the toxic cyanobacterium Planktothrix spp.
European Journal of Phycology, 2009Co-Authors: Simone Kosol, Johanna Schmidt, Rainer KurmayerAbstract:Cyanobacteria frequently form mass developments in surface waters. Populations consist of strains that differ in the Production of bioactive peptides, e.g. microcystins (MC) inhibiting protein phosphatases 1 and 2A and anabaenopeptins (APN) inhibiting carboxypeptidases. Forty-nine strains (18 green-pigmented (phycocyanin-rich) P. agardhii strains and 31 red-pigmented (phycoerythrin-rich) P. rubescens strains) of the filamentous cyanobacterium Planktothrix (Anagnostidis et Komarek) were analysed for their MC and APN Net Production rates. These rates were compared with (i) the pigmentation, (ii) the proportion of extra- and intracellular peptide concentrations and (iii) the cellular growth rates under standardized laboratory conditions. Excluding the strains lacking MC and APN, the MC and APN contents varied up to 14-fold and 12-fold, each. The variation in minimum and maximum peptide content (0.32–4.51 µg MC mg−1 dry weight; 0.85–10.32 µg APN mg−1 dry weight) exceeded the variation found for chlorophyll a ...
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the abundance of microcystin producing genotypes correlates positively with colony size in microcystis sp and determines its microcystin Net Production in lake wannsee
Applied and Environmental Microbiology, 2003Co-Authors: Guntram Christiansen, Rainer Kurmayer, Ingrid ChorusAbstract:The working hypotheses tested on a natural population of Microcystis sp. in Lake Wannsee (Berlin, Germany) were that (i) the varying abundance of microcystin-producing genotypes versus non-microcystin-producing genotypes is a key factor for microcystin Net Production and (ii) the occurrence of a gene for microcystin Net Production is related to colony morphology, particularly colony size. To test these hypotheses, samples were fractionated by colony size with a sieving procedure during the summer of 2000. Each colony size class was analyzed for cell numbers, the proportion of microcystin-producing genotypes, and microcystin concentrations. The smallest size class of Microcystis colonies ( 100 μm) showed the highest proportion of microcystin-producing genotypes, the lowest proportion of non-microcystin-producing cells, and the highest microcystin cell quotas. The microcystin Net Production rate was nearly one to one positively related to the population growth rate for the larger colony size classes (>100 μm); however, no relationship could be found for the smaller size classes. It was concluded that the variations found in microcystin Net Production between colony size classes are chiefly due to differences in genotype composition and that the microcystin Net Production in the lake is mainly influenced by the abundance of the larger (>100-μm) microcystin-producing colonies.
Kenneth S. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Net Production of oxygen in the subtropical ocean
Nature, 2008Co-Authors: Stephen C. Riser, Kenneth S. JohnsonAbstract:The question of whether the plankton communities in low-nutrient regions of the ocean, comprising 80% of the global ocean surface area, are Net producers or consumers of oxygen and fixed carbon is a key uncertainty in the global carbon cycle. Direct measurements in bottle experiments indicate Net oxygen consumption in the sunlit zone, whereas geochemical evidence suggests that the upper ocean is a Net source of oxygen. One possible resolution to this conflict is that primary Production in the gyres is episodic and thus difficult to observe: in this model, oligotrophic regions would be Net consumers of oxygen during most of the year, but strong, brief events with high primary Production rates might produce enough fixed carbon and dissolved oxygen to yield Net Production as an average over the annual cycle. Here we examine the balance of oxygen Production over three years at sites in the North and South Pacific subtropical gyres using the new technique of oxygen sensors deployed on profiling floats. We find that mixing events during early winter homogenize the upper water column and cause low oxygen concentrations. Oxygen then increases below the mixed layer at a nearly constant rate that is similar to independent measures of Net community Production. This continuous oxygen increase is consistent with an ecosystem that is a Net producer of fixed carbon (Net autotrophic) throughout the year, with episodic events not required to sustain positive oxygen Production.
K.p. Singh - One of the best experts on this subject based on the ideXlab platform.
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Effect of farmyard manure and chemical fertilizer on total Net Production, yield, and root necromass in a dryland rice-lentil agroecosystem
Tropical Agriculture, 1995Co-Authors: Nandita Ghoshal, K.p. SinghAbstract:Effects of farmyard manure (FYM) and chemical fertilizer on crop biomass [total Net Production (TNP)], yield, and root necromass were studied in a tropical dryland rice-lentil rotation agroecosystem. Total Net Production of rice which was greater than that of lentil increased significantly with exogenous nutrient inputs. During both crops aboveground Net Production (ANP) was recorded till the final harvest but no belowground Net Production (BNP) was recorded after the grain or seed-forming stage. Compared to the control, enhancement of TNP in rice was comparable for fertilizer (32%) and FYM (30%) treatments, but in lentil FYM showed a greater effect (43%) compared to fertilizer (29%) application. Grain or seed yield accounted for about 11% of TNP in both crops. Similar to TNP, rice yield showed a greater response to fertilizer (50%) compared to FYM (44%) while lentil yield responded more to FYM (43%) than to fertilizer (1%). Farmyard manure application resulted in greater necromass accumulation compared to fertilizer application. Rice contributed the major portion of root necromass in the crop land. While root necromass increased through the rice crop period, it decreased consistently through that of the lentil crop.
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Biomass and Net Production of teak plantations in a dry tropical region in India
Forest Ecology and Management, 1992Co-Authors: S.b. Karmacharya, K.p. SinghAbstract:Abstract In an age series of teak plantations (4, 14 and 30 years old), raised in a dry tropical region in northern India, an analysis of the standing crop biomass and aboveground Net Production was made through non-descructive methods. Allometric regressions were developed relating girth to weights of bole wood, bole bark, branch, leaf and inflorescence. Annual girth increments were recorded. The aboveground biomass ranged from 25.7 to 76.9 t ha −1 . The proportion of woody biomass was 56% of the total at 4 years, increasing to 91% of the total by 30 years. On the contrary, the proportion of leaf biomass decreased from 34% of the total at 4 years to 7% at 30 years. Very high aboveground Net Production was obtained at 4 years (25.6 t ha −1 year −1 ), but Net Production decreased with age (14 and 12.9 t ha −1 year −1 at 14 and 30 years). The share of bole decreased from 54% of total Net Production at 4 years to 44% of the total at 30 years, with increase in age much less dark than wood was produced. The reproductive parts comprised 2% of biomass but accounted for 9% of Net Production at 30 years. At 30 years these plantations attained the level of biomass and Net Production found in uneven-aged natural dry deciduous forests of the same region.
Krisztina Szalontai - One of the best experts on this subject based on the ideXlab platform.
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Structure and Production of the metazoan zooplankton in Lake Balaton (Hungary) in summer
Hydrobiologia, 2003Co-Authors: Laura Parpală, László Tóth, Victor Zinevici, Péter Németh, Krisztina SzalontaiAbstract:Taxonomical diversity, numerical density, biomass, Production, and biomass turnover of the metazoan zooplankton of Lake Balaton were compared between two different open water areas with different primary Production, in the summers 1998, 1999, and 2000. Density of the zooplankton showed 1.1 to 3.2 fold differences between the less and more trophic areas. Density of the crustaceans, add up to the total density of rotifers and veligers. Net Production of the primary consumers (filter-feeders and sedimentators) in the more trophic area exceeded 2 to 4 times of that in the less trophic area. In secondary consumer (predatory) level, such a difference had not been observed. The ratio between the Net Production of the primary and secondary consumers changed in the range of 4.7 to 5.9 and 14.5 to 30.3 in the less and the more trophic areas, respectively. Gross Production of the zooplankton exceeded 8.5 to 9.1 and 5.1 to 5.9 times of the Net Production in the less and the more trophic areas, respectively. Biomass turnover time of the zooplankton was 8.41 and 7.79 days, in the less and the more trophic area, if Net Production was considered. Considering the gross Production, that was 2.5 and 2.2 days, respectively.
Peter F. Newton - One of the best experts on this subject based on the ideXlab platform.
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Forest Production model for upland black spruce stands : Optimal site occupancy levels for maximizing Net Production
Ecological Modelling, 2005Co-Authors: Peter F. NewtonAbstract:Abstract The objective of this study was to develop a forest Production model for determining optimal density management regimes for upland black spruce ( Picea mariana (Mill.) B.S.P.) stands based on the maximization of Net Production. This objective was attained via the development of an allometrically extended stand density management diagram (SDMD), which was used to describe the mass dynamics of biotic and abiotic tree components by initial density regime, site quality and fine root turnover rate. Specifically, periderm, stem, branch, foliage and abiotic crown masses were estimated employing multivariate allometric regression functions based on data derived from 125 destructively sampled trees. Below-ground mass estimates were obtained using generalized allometric relationships derived from the literature. Abiotic masses included three basic components: (1) allometrically estimated retained woody debris consisting of abiotic crown structures that remained attached to the main stem; (2) fine woody debris arising from needle loss, root turnover, and abscission of modular components; (3) coarse woody debris arising from trees which incurred mortality through self-thinning. The algorithmic version of the model (1) simultaneously calculates periodic annual Net Production estimates (Mg/ha/year) by 10-year intervals over 100-year rotation lengths for eight initial density conditions, (2) given (1), determines the occupancy level for which Net Production is maximized for each stage of development (decade interval), and (3) given (2), determines the optimal size–density trajectory within the context of a SDMD. Additionally, results derived from multiple model simulations employing a range of initial densities (1500, 1650,…, 16,350 stems/ha), site indices (9, 10,…, 15 m) and fine root turnover rates (0.2, 0.3,…,0.8 proportion/year), indicated that black spruce productivity was maximized when site occupancies were maintained slightly below the zone of imminent competition mortality. Instructions for acquiring an executable version of the model through the InterNet are also included.
