Loss Of Trees In Nemaha County, Nebraska, Since 1856 Due To Agricultural Expansion

Forest surveys of Nebraska were conducted in 1955 and 1977 (Shasby, 1977). These surveys sought to characterize species, total area, and size classes of economically important trees. Information gained from these surveys is very alarming. The counties of Nernaha, Otoe, and Richardson in the southeastern survey district have lost between 34.7% and 53.9% of their trees during that 22-yr period. These are critical losses considering that these counties are only 2.8% to 5.5% forested. The purpose of this study was to investigate historical changes in tree vegetation that occurred in Nemaha County. The trees as they occurred in the county when settlers started to colonize this part of Nebraska were studied. For this, the General Land Office surveys were helpful. Information of this type has been used to categorize presettlement forests in several states (Steams, 1949; Spurr, 1951; Shanks, 1953; Bourdo, 1956; Wuenscher and Valiunas, 1967; Leitner and J ackson, 1981). Most of these studies did not concentrate on using available information to define losses in vegetation that occurred since the original surveys. Information in the General Land Office surveys can be used to determine the location, area, size classes, and species of trees that occurred in the past

Loss Of Trees In Nemaha County, Nebraska, Since 1856 Due To Agricultural Expansion

Forest surveys of Nebraska were conducted in 1955 and 1977 (Shasby, 1977). These surveys sought to characterize species, total area, and size classes of economically important trees. Information gained from these surveys is very alarming. The counties of Nernaha, Otoe, and Richardson in the southeastern survey district have lost between 34.7% and 53.9% of their trees during that 22-yr period. These are critical losses considering that these counties are only 2.8% to 5.5% forested. The purpose of this study was to investigate historical changes in tree vegetation that occurred in Nemaha County. The trees as they occurred in the county when settlers started to colonize this part of Nebraska were studied. For this, the General Land Office surveys were helpful. Information of this type has been used to categorize presettlement forests in several states (Steams, 1949; Spurr, 1951; Shanks, 1953; Bourdo, 1956; Wuenscher and Valiunas, 1967; Leitner and J ackson, 1981). Most of these studies did not concentrate on using available information to define losses in vegetation that occurred since the original surveys. Information in the General Land Office surveys can be used to determine the location, area, size classes, and species of trees that occurred in the past

Exploring the symbiotic pangenome of the nitrogen-fixing bacterium Sinorhizobium meliloti

<p>Abstract</p> <p>Background</p> <p><it>Sinorhizobium meliloti </it>is a model system for the studies of symbiotic nitrogen fixation. An extensive polymorphism at the genetic and phenotypic level is present in natural populations of this species, especially in relation with symbiotic promotion of plant growth. AK83 and BL225C are two nodule-isolated strains with diverse symbiotic phenotypes; BL225C is more efficient in promoting growth of the <it>Medicago sativa </it>plants than strain AK83. In order to investigate the genetic determinants of the phenotypic diversification of <it>S. meliloti </it>strains AK83 and BL225C, we sequenced the complete genomes for these two strains.</p> <p>Results</p> <p>With sizes of 7.14 Mbp and 6.97 Mbp, respectively, the genomes of AK83 and BL225C are larger than the laboratory strain Rm1021. The core genome of Rm1021, AK83, BL225C strains included 5124 orthologous groups, while the accessory genome was composed by 2700 orthologous groups. While Rm1021 and BL225C have only three replicons (Chromosome, pSymA and pSymB), AK83 has also two plasmids, 260 and 70 Kbp long. We found 65 interesting orthologous groups of genes that were present only in the accessory genome, consequently responsible for phenotypic diversity and putatively involved in plant-bacterium interaction. Notably, the symbiosis inefficient AK83 lacked several genes required for microaerophilic growth inside nodules, while several genes for accessory functions related to competition, plant invasion and bacteroid tropism were identified only in AK83 and BL225C strains. Presence and extent of polymorphism in regulons of transcription factors involved in symbiotic interaction were also analyzed. Our results indicate that regulons are flexible, with a large number of accessory genes, suggesting that regulons polymorphism could also be a key determinant in the variability of symbiotic performances among the analyzed strains.</p> <p>Conclusions</p> <p>In conclusions, the extended comparative genomics approach revealed a variable subset of genes and regulons that may contribute to the symbiotic diversity.</p

Multi-messenger searches via IceCube’s high-energy neutrinos and gravitational-wave detections of LIGO/Virgo

We summarize initial results for high-energy neutrino counterpart searches coinciding with gravitational-wave events in LIGO/Virgo\u27s GWTC-2 catalog using IceCube\u27s neutrino triggers. We did not find any statistically significant high-energy neutrino counterpart and derived upper limits on the time-integrated neutrino emission on Earth as well as the isotropic equivalent energy emitted in high-energy neutrinos for each event

In-situ estimation of ice crystal properties at the South Pole using LED calibration data from the IceCube Neutrino Observatory

The IceCube Neutrino Observatory instruments about 1 km3 of deep, glacial ice at the geographic South Pole using 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. A unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. Birefringent light propagation has been examined as a possible explanation for this effect. The predictions of a first-principles birefringence model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties do not only include the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube LED calibration data, the theory and parametrization of the birefringence effect, the fitting procedures of these parameterizations to experimental data as well as the inferred crystal properties.</p