Integration of geospatial and cattle nutrition information to estimate paddock grazing capacity in Northern US prairie

Spatiotemporal variability in forage quantity and quality requires that regular assessment is needed of the capacity for grasslands to support livestock nutritional requirements. Current methods for estimating grazing capacity are typically production-based and lack the forage quality data necessary to match nutrients in forage with livestock requirements in real time. This paper describes a method for estimating short-term grazing capacity for small (1–20 ha) paddocks using cattle nutrition and high spatial resolution forage data in Geographic Information Systems (GIS) for mixed-grass prairie. We define grazing capacity as the number of days a specific paddock will support the nutritional requirements of beef cattle. We integrate previously published methods for estimating cattle nutritional requirements, forage quality (crude protein) and forage quantity (phytomass) to estimate grazing capacity based on current standing-crop. The model utilizes high-resolution (<30-m) satellite imagery or field data to estimate short-term grazing capacity for small paddocks. Three versions of the model were evaluated on one paddock under cattle use in 2007. One version was parameterized using data collected on June 22 from the Landsat Thematic Mapper (TM), one version was parameterized using data collected June 23 from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and one version was parameterized using data collected June 20 from field clippings. TM and ASTER versions underestimated grazing capacity by four days while the field version overestimated grazing capacity by one day. Results suggest integration of cattle nutrition and forage data in GIS could assist with stocking rate adjustments, but additional trials are needed.     

曝气生物滤池深度处理印染废水的研究

[目的]研究曝气生物滤池对污水厂出水的深度处理效果。[方法]采用上流式曝气生物滤池对污水厂出水进行深度处理,研究气水比、水力负荷对处理效果的影响,分析滤池中沿程微生物活性与污染物降解规律。[结果]在气水比4∶1,水力负荷为0.35m3/(m2·h)时,COD的去除效率为54%,色度的去除率为78%,NH3-N去除率为91%,满足GB/T 18920-2002城市杂用水水质标准。试验条件下,60 cm滤料层以下为COD降解主要区域,60~90 cm为NH3-N降解主要区域。生物量沿滤池高度范围逐渐降低,并趋于稳定,微生物活性呈现先升高后降低再升高的趋势。[结论]该研究可为污水处理厂污水处理工艺提标升级提供基础数据和理论支撑。     

借鉴美国经验科学发展我国的玉米产业

在分析了美国玉米生产的现状和先进经验的基础上,根据我国玉米产业现状,提出了加强优质、专用、抗逆和资源高效利用型玉米新品种的培育与推广;促进节本增效、规范化技术的研制和配套栽培技术的应用,尽可能降低生产成本;逐步建立健全优质、专用玉米标准化生产基地和产业化体系;加强技术培训,培育高素质的产业化生产劳动力;开展玉米产品安全性研究等发展方向或措施,为政府和农业主管部门的宏观决策提供依据。     

高校双语教学的实践与展望

本文通过在双语教学的实践和探索过程中积累的经验，就教学模式、教学手段和教材的处理等总结了有效的举措和经验，分析了教学中所遇到的问题并提出可行的解决办法，最后对将双语教学如何达到教学目标提出了展望。     

吉林省蝶类资源的研究

吉林省蝶类资源比较丰富，根据多年的调查研究，共获蝶类标本１万余份，按照中国蝴蝶分类系统，鉴定并记载了７科９５属，１９４种２０７亚种，其中４１种为吉林省新记录，同时对吉林省蝶类资源及区系成分进行了分析，提出吉林省蝶类昆虫区系特征。     

传统农业技术向现代农业技术的转变-继承、改造和提升

根据中国传统农业技术的特点,通过分析其历史演变过程,对比传统农业技术与现代农业技术的不同特征,提出在实现农业现代化的过程中,要正确对待传统农业技术,继承其优良传统,改造其落后和不完善的地方,最终将传统农业技术提升为现代农业技术的组成部分,是实现传统农业现代农业技术转变的有效途径和必由之路。     

Effects of light and intraspecific competition on growth and crown morphology of two size classes of understory balsam fir saplings

This paper characterizes the growth and crown morphology of young balsam fir saplings naturally regenerated under a gradient of understory light environments and intraspecific competition densities for two size classes (50–100 cm and 100–200 cm). Most growth and crown morphological parameters investigated were strongly related to the natural light gradient investigated (3–83% full sunlight), but the relationship tended to plateau at around 25% full sunlight. The relationships were generally better for the larger size class. Intraspecific competition did not significantly affect growth and crown morphology of saplings receiving less than 25% full sunlight, but it affected relative height growth, relative radial growth and the apical dominance ratio for those receiving more than 25% full sunlight (R²=0.506; p<0.001; R²=0.403; p<0.002; R²=0.348; p<0.001, respectively). These results suggest that live crown ratio, apical dominance ratio and the number of internodal branches can provide, alone or in combination, useful indicators of vigour for understory fir. Such a study provides the basic data inputs required for the development of empirically-derived mechanistic models that can predict understory tree growth and survival.     

Regeneration of Styrax argenteus in natural forest and in plantations of Cupressus lindleyi in Michoacan, Mexico

We evaluated the density and population height structure of Styrax argenteus in natural pine–oak forest and in Cupressus lindleyi plantations in Michoacan, Mexico. We also evaluated whether populations of S. argenteus in pine–oak vegetation and in C. lindleyi plantations had a clumped distribution. Finally, we evaluated whether advanced regeneration of different species was higher under the crown of S. argenteus than around it. Density of S. argenteus was higher in pine–oak forest than under plantations, but density in plantations was high. The structure of populations of S. argenteus in pine–oak vegetation had more individuals with ≤ 0.5 and >2 m, while populations in plantations had more individuals in intermediate height categories. Both populations were clumped. Only one species, Rubus liebmannii had higher densities under S. argenteus, so that other species might also colonize C. lindleyi plantations as a consequence to their affinity to S. argenteus. Although S. argenteus and other native species were apparently establishing under C. lindleyi plantations, Pinus and Quercus, the dominant genera of this forest type, were not. Consequently other activities, like liberation thinning, might be required to re-establish natural vegetation under C. lindleyi plantations.

---

Resumen Evaluamos la densidad y estructura poblacional en categorías de altura para Styrax argenteus en bosque natural de pino-encino y bajo plantaciones de Cupressus lindleyi en Michoacán, México. También evaluamos si las poblaciones de S. argenteus en bosque de pino-encino y bajo plantaciones de C. lindleyi tenían una distribución agregada. Finalmente, evaluamos si la regeneración avanzada de distintas especies era mayor bajo la copa de S. argenteus, que alrededor de ésta. La densidad de S. argenteus fue mayor bajo vegetación de pino-encino que bajo las plantaciones, pero la densidad en plantaciones también fue alta. La estructura poblacional de S. argenetus en vegetación de pino-encino tuvo más individuos ≤ 0.5 y >2 m, mientras que la población en plantaciones tuvo más individuos en categorías de altura intermedias. Solo una especie, Rubus liebmannii tuvo densidades mayores bajo la copa de S. argenteus que alrededor de la misma, por lo que esta especie podría estar también colonizando plantaciones de C. lindleyi como consecuencia de su afinidad con S. argenteus. Aunque S. argenteus y otras especies se establecieron aparentemente en plantaciones de C. lindleyi, no fue así para los géneros dominantes en este tipo de bosque, Pinus y Quercus. Consecuentemente otras actividades, como cortes de liberación, sean necesarias para re-establecer la vegetación natural bajo dichas plantaciones de C. lindleyi.