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Landscape Ecology - Over the past decades, numerous threats from climate- and land-use change to ecosystems have been identified. Grassland ecosystems are among the most endangered in the world and... 相似文献
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H. Burtscher A. Leonardi D. Steiner U. Baltensperger A. Weber 《Water, air, and soil pollution》1993,68(1-2):137-147
At different locations in Zürich (urban and suburban area) ambient aerosol has been measured by a variety of methods. Total mass concentration, black carbon mass concentration, size distribution, Fuchs surface and photoelectric charging of particles (as a measure for the PAH concentration) have been determined. As a reference for “fresh” aerosol, measurements have also been carried out in a car parking garage. By comparing the data obtained at different locations and different times of the day aging processes can be investigated. All measured signals show significant peaks during the rush-hours, indicating that the majority of the particles arise from automotive traffic. Aging is expressed by decreasing number concentrations, increasing diameter (coagulation) and decreasing black carbon and PAH content of the particles. The decrease in PAH and black carbon fraction may be due to mixing of the aerosol with non-combustion particles or by condensation of material from the gas phase on the particle; the decrease in PAH concentration may also be due to degradation of the PAHs. 相似文献
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The entire USDA‐ARS maintained collection of 650 accessions of proso millet (Panicum miliaceum L.) was evaluated for the presence of accessions with waxy (amylose‐free) endosperm starch. Six accessions, five of which derived from mainland China, were identified. Segregation ratios for waxy endosperm were evaluated in F2 and F3 populations derived from crosses between two waxy accessions, PI 436625 (Lung Shu 16) and PI 436626 (Lung Shu 18), and several wild‐type accessions. The waxy trait was found to be under the control of duplicate recessive alleles at two loci, herein designated wx‐1 and wx‐2. Wild‐type alleles at these loci were designated Wx‐1 and Wx‐2. Iodine‐binding revealed a mean grain‐starch amylose concentration of 3.5% in waxy lines and 25.3% in wild‐type proso. Expression of the granule‐bound starch synthase (waxy protein) in waxy lines was reduced to approximately one‐tenth that of wild‐type accessions. The waxy accessions identified now are available for the introgression of this trait into breeding lines adapted to the Great Plains of North America. 相似文献
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W. H. Thompson D. Pietsch J. M. Blumenthal A. M. H. Ibrahim D. D. Baltensperger 《Journal of Agronomy and Crop Science》2013,199(4):299-307
Our study was conducted to determine agronomic optimum seeding rates (AOSR) for irrigated maize under a range of agroecological conditions in Texas. Environmental factors that affect irrigated maize production vary considerably across Texas. This variability imposes region‐specific limitations on statewide maize seeding rate recommendations. Our research examined the efficiency of varying seeding rates on irrigated maize grain yields in five USEPA Level IV Ecoregions that comprise most of the irrigated maize‐producing area of Texas. The selected sites span a distance of 1200 km from south to north Texas and elevations from 20 to 1218 m above mean sea level. We conducted the study over three growing seasons from 2005 through 2007 in two Level IV Ecoregions of the High Plains of North Texas (N), one in the East Central Plains (E), one in the Southern Plains and one in Western Gulf Coastal Plains of South Texas (S). We observed that maximum grain yields and AOSR to achieve maximum maize grain yields vary considerably among ecoregions. In South Texas, we observed grain yield response rates of 125–129, 151 kg 1000 seeds?1 in E and 163–199 kg 1000 seeds?1 in N. We show that growing season average daily minimum air temperature (TMIN) explains most of this variation (r2 = 0.98, P‐value < 0.01) and conclude that seeding rate efficiency is concomitant to TMIN. Maximum grain yields (GYMAX) determined with seeding rate response analysis also varied among ecoregions and with TMIN from south to north Texas, from a low of 8.3 Mg ha?1 in S to a high of 18.4 Mg ha?1 in N (r2 = 0.59, P‐value < 0.01). We conclude that development of agronomic management models by Level IV Ecoregions of Texas combined with site‐specific TMIN climatological data serve as a valid template for delivering robust and agroecozone‐specific irrigated maize seeding rate recommendations in Texas. 相似文献
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Kalberer M Paulsen D Sax M Steinbacher M Dommen J Prevot AS Fisseha R Weingartner E Frankevich V Zenobi R Baltensperger U 《Science (New York, N.Y.)》2004,303(5664):1659-1662
Results from photooxidation of aromatic compounds in a reaction chamber show that a substantial fraction of the organic aerosol mass is composed of polymers. This polymerization results from reactions of carbonyls and their hydrates. After aging for more than 20 hours, about 50% of the particle mass consists of polymers with a molecular mass up to 1000 daltons. This results in a lower volatility of this secondary organic aerosol and a higher aerosol yield than a model using vapor pressures of individual organic species would predict. 相似文献
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S.A. Saseendran D.C. Nielsen D.J. Lyon L. Ma D.G. Felter D.D. Baltensperger G. Hoogenboom L.R. Ahuja 《Field Crops Research》2009
Dryland farming strategies in the High Plains must make efficient use of limited and variable precipitation and stored water in the soil profile for stable and sustainable farm productivity. Current research efforts focus on replacing summer fallow in the region with more profitable and environmentally sustainable spring and summer crops. In the absence of reliable precipitation forecasts for the crop growing season, farmers rely mainly upon knowledge of plant available water (PAW) in the soil profile at planting for making crop choice decisions. To develop a decision support strategy for crop selection based on initial PAW, experiments were conducted with spring triticale (XTiticosecale Wittmack), proso millet (Panicum miliaceum L.), and foxtail millet (Setaria italica L. Beauv.) under artificially controlled Low, Medium, and High initial PAW levels during 2004 and 2005 at Akron, Colorado, and Sidney, Nebraska. The objectives of this study were to adapt an existing cropping systems model for the simulation of triticale and millet and to evaluate simulations from the adapted model by comparing results with field data collected under varying initial PAW conditions. The Root Zone Water Quality Model with DSSAT v4.0 crop growth modules (RZWQM2) was used. Specifically, the Cropping System Model (CSM)–CERES–Wheat module was adapted for simulating triticale, and CSM–CERES–Sorghum (v4.0) module was adapted for simulating proso millet and foxtail millet. Soil water, leaf area index, grain yield, and biomass data for the highest PAW treatment from one crop season for each of the three crops were used to adapt and calibrate the crop modules. The models were then evaluated with data from the remaining PAW treatments. The proso millet module was further tested with four years of data from a crop rotation experiment at Akron from 2003 to 2006. Simulation results indicated that the adapted and calibrated crop modules have the potential to simulate these new crops under a range of varying water availability conditions. Consequently, these models can aid in the development of decision support tools for the season-to-season management of these summer fallow replacement crops under dryland conditions in semi-arid environments. 相似文献
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Schwikowski M. Novo A. Baltensperger U. Delmas R. Gäggeler H. W. Kasper A. Kuhn M. Maupetit F. Nickus U. Preunkert S. Puxbaum H. Rossi G. C. Schöner W. Wagenbach D. 《Water, air, and soil pollution》1997,93(1-4):67-91
In order to investigate the seasonal and geographical distribution of snow concentrations anddeposition fluxes of environmentally relevant ionic species in the Alps, the international programSNOSP was initiated. In the framework of this program, intercomparisons of snow samplingtechniques and analytical methods to determine the ionic species C1-, NO 3 - ,SO 4 2- , K+, Na+, NH4 +, Mg2+, and Ca2+, as well as the pH and the specificconductivity were performed. The concentrations of these species in the snow samples collectedin the SNOSP program varied by orders of magnitude with, e.g., concentrations of NO 3 - , SO 4 2- , and NH4 + ranging from 0.2-60, 0.2-90, and 0.1-60 µeq L-1,respectively. The intercomparisons revealed a reasonable agreement of the determinations of thespecies Cl-, NO 3 - , SO 4 2- , Na+, and NH4 + in snow. Results were less satisfactory for K+, Mg2+, Ca2+,and H+, mainly due to the very low concentrations. In conclusion, recommendations areformulated for the reliable derivation of chemical inventories from snow packs. 相似文献
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F. E. Dowell E. B. Maghirang R. A. Graybosch P. S. Baenziger D. D. Baltensperger L. E. Hansen 《Cereal Chemistry》2006,83(5):537-543
An automated sorting system was developed that nondestructively measured quality characteristics of individual kernels using near‐infrared (NIR) spectra. This single‐kernel NIR system was applied to sorting wheat (Triticum aestivum L.) kernels by protein content and hardness, and proso millet (Panicum miliaceum L.) into amylose‐bearing and amylose‐free fractions. Single wheat kernels with high protein content could be sorted from pure lines so that the high‐protein content portion was 3.1 percentage points higher than the portion with the low‐protein kernels. Likewise, single wheat kernels with specific hardness indices could be removed from pure lines such that the hardness index in the sorted samples was 29.4 hardness units higher than the soft kernels. The system was able to increase the waxy, or amylose‐free, millet kernels in segregating samples from 94% in the unsorted samples to 98% in the sorted samples. The portion of waxy millet kernels in segregating samples was increased from 32% in the unsorted samples to 55% after sorting. Thus, this technology can be used to enrich the desirable class within segregating populations in breeding programs, to increase the purity of heterogeneous advanced or released lines, or to measure the distribution of quality within samples during the marketing process. 相似文献