Response of North American ecosystem models to multi-annual periodicities in temperature and precipitation

Ecosystem models typically use input temperature and precipitation data generated stochastically from weather station means and variances. Although the weather station data are based on measurements taken over a few decades, model simulations are usually on the order of centuries. Consequently, observed periodicities in temperature and precipitation at the continental scale that have been correlated with largscale forcings, such as ocean-atmosphere dynamics and lunar and sunspot cycles, are ignored. We investigated how these natural climatic fluctuations affect aboveground biomass in ecosystem models by incorporating some of the more pronounced continental-scale cycles in temperature (4, 11, 80, 180 year periods) and precipitation (11 and 19 year periods) into models of three North American forests (using LINKAGES) and one North American grassland (using STEPPE). Even without inclusion of periodicities in climate, long-term dynamics of these models were characterized by internal frequencies resulting from vegetation birth, growth and death processes. Our results indicate that long-term temperature cycles result in significantly lower predictions of forest biomass than observed in the control case for a forest on a biome transition (northern hardwoods/boreal forest). Lower-frequency, higher-amplitude temperature oscillation caused amplification of forest biomass response in forests containing hardwood species. Shortgrass prairie and boreal ecosystems, dominated by species with broad stress tolerance ranges, were relatively insensitive to climatic oscillations. Our results suggest periodicities in climate should be incorporated within long-term simulations of ecosystems with strong internal frequencies, particularly for systems on biome transitions.     

调整营养制度降低肉仔鸡饲养成本的研究

设计３个试验研究了调整营养制度,降低肉仔鸡饲养成本的措施。试验结果表明,让肉仔鸡从３周龄提前到２周龄时由生长前期料换用生长中期料,不影响其３７日龄体重及０～３７日龄的饲料利用。在无严重应激存在的情况下,肉仔鸡上市（４９日龄）前３周内的基础日粮中不补加微量元素和２周内不补加维生素不影响生长和饲料转化率。以上对肉仔鸡生长前、后期营养摄入量的调整均可有效降低饲养成本     

青海半干旱农区对气候变暖后适应状况的探讨

本文从掌握的青海半干旱农业区－“河湟”谷地部分气象资料出发,建立地区蒸发量与年平均气温间的回归方程,探讨全球变化后这些地区干燥指数状况可能发生的改变。现今４０年来,该区域干暖与湿冷相配合;气温趋暖化并非显著,但干燥指数有所上升,区域向湿润发展。当设定未来平均气温升高２℃,降水量增加１０％时,青海半干旱农业区,在未来气候情景下蒸发量的增加比降水的增加来得快,将导致干旱胁迫加重。但降水量增加２０％时,     

Pencycuron dissipation in soil: effect of application rate and soil conditions

Dissipation of the fungicide pencycuron was examined under controlled laboratory conditions in clay loam soils from rice cultivated fields of alluvial soil (Typic udifluvent) and coastal saline soil (Typic endoaquept) at field rate, twice the field rate and 10 times the field rate with and without decomposed cow manure maintained at 60% of maximum water-holding capacity (WHC) and waterlogged soil condition. The half-life values depended on the initial concentrations of pencycuron. Pencycuron, in general, degraded fastest in coastal saline soil and in soil amended with decomposed cow manure at 60% of maximum WHC of soil.     

Potential colonization of newly available tree-species habitat under climate change: An analysis for five eastern US species

We used a combination of two models, DISTRIB and SHIFT, to estimate potential migration of five tree species into suitable habitat due to climate change over the next 100 years. These species, currently confined to the eastern half of the United States and not extending into Canada, are Diospyros virginiana (persimmon), Liquidambar styraciflua (sweetgum), Oxydendrum arboreum (sourwood), Pinus taeda (loblolly pine), and Quercus falcata var. falcata (southern red oak). DISTRIB uses a statistical approach to assess potential suitable habitat under equilibrium of 2 × CO₂. SHIFT uses a cellular automata approach to estimate migration and is driven primarily by the abundance of the species near the boundary, forest density inside and outside of the boundary, and distance between cells. For each cell outside the current boundary, SHIFT creates an estimate of the probability that each unoccupied target cell will become colonized over 100 years. By evaluating the probability of colonization within the potential ‘new’ suitable habitat, we can estimate the proportion of new habitat that might be colonized within a century. This proportion is low (<15%) for all five species, suggesting that there is a serious lag between the potential movement of suitable habitat and the potential for the species to migrate into the new habitat. However, humans could hasten the migration of certain species by physically moving the propagules, especially for certain rare species that are unable to move sufficiently through fragmented landscapes, or even more common species, e.g., beech, that have lost many of their animal dispersers.     

Associations between management, climate, and Escherichia coli O157 in the faeces of feedlot cattle in the Midwestern USA

Our objective was to generate hypotheses for potential on-farm control strategies for Escherichia coli O157 by identifying associations between management practices and climate, and the presence of E. coli O157 in feedlot cattle. Faeces were obtained from 10,622 cattle in 711 pens on 73 feedlots between May and August 2001. Management and climate information was obtained by questionnaire and observation at the time of sampling. The prevalence of E. coli O157 was 10.2% at the sample level, 52.0% at the pen-level, and 95.9% at the feedlot-level. The factors associated with the presence of E. coli O157 in cattle faeces were the frequency of observing cats in the pens or alleys (most common when observed daily), the presence of E. coli O157 in the water tanks (positive association), the historical use of injectable mass medication (positive association), the use of antibiotics in the ration or water (negative association), the wetness of the pen, number of cattle in the pen (negative association), wind velocity (positive association), and height of the feed bunk (positive association).     

Holocene palaeo-invasions: the link between pattern, process and scale in invasion ecology?

Invasion ecology has made rapid progress in recent years through synergies with landscape ecology, niche theory, evolutionary ecology and the ecology of climate change. The palaeo-record of Holocene invasions provides a rich but presently underexploited resource in exploring the pattern and process of invasions through time. In this paper, examples from the palaeo-literature are used to illustrate the spread of species through time and space, also revealing how interactions between invader and invaded communities change over the course of an invasion. The main issues addressed are adaptation and plant migration, ecological and evolutionary interactions through time, disturbance history and the landscape ecology of invasive spread. We consider invasions as a continuous variable, which may be influenced by different environmental or ecological variables at different stages of the invasion process, and we use palaeoecological examples to describe how ecological interactions change over the course of an invasion. Finally, the use of palaeoecological information to inform the management of invasions for biodiversity conservation is discussed.     

南山气候与荷斯坦奶牛泌乳量的关系

南山是中国南方独特的天然草场,气候温凉,年平均气温11.2℃,最热月7月平均气温为18.4℃,极端最高气温26.8℃,最冷月1月平均气温2.2℃,极端最低气温-16.0℃,荷斯坦奶牛耐寒怕热,适宜温度为11-16℃,适宜在南山养殖,每头奶牛年产奶量为6900 kg,达到产奶量先进水平,其产奶量高峰值在6月,产奶量低值出现在10月.     

Prolonged summer droughts retard soil N processing and stabilization in organo-mineral fractions

Prolonged summer droughts are projected to occur as a consequence of climate change in Central Europe. The resulting reduced soil water availability may lead to alterations in rates of soil processes such as nitrogen partitioning among soil organic matter fractions and stabilization within soil. To study the effect of climate change-induced drought on (1) the distribution of nitrogen among soil organic matter fractions and (2) nitrogen stabilization, we performed a space-for-time climate change experiment. We transferred intact plant–soil–microbe mesocosms of a Rendzic Leptosol with a young beech tree from a slope with northwestern exposure in southern Germany characterized by a cool-moist microclimate across a narrow valley to a slope with southwestern exposure with a warm-dry microclimate, which reflects projected future climatic conditions. A control transfer was also done on the northwest-facing slope within the same area of origin. We combined a homogenous ¹⁵N labeling approach using ammonium nitrate with a physical fractionation procedure and chemical soil extraction protocols. Our aim was to follow the partitioning of ¹⁵N in different soil organic matter fractions, i.e. light fractions, organo-mineral fractions, and extractable soil fractions including microbial biomass, ammonium, nitrate, and dissolved organic nitrogen. Within less than one growing season, we observed a modified partitioning of recently applied inorganic ¹⁵N between different soil fractions in relation to drier summer conditions, with attenuated nitrogen turnover under drought and consequently significantly higher ¹⁵N concentrations in the relatively labile light fractions. We ascribed this effect to a decelerated mineralization immobilization turnover. We conclude that prolonged summer droughts may alter the stabilization dynamics because the induced inactivity of microorganisms may reduce the transfer of nitrogen to stabilization pathways. A retarded stabilization in organo-mineral associations enhances the risk of nitrogen losses during extreme rainfall events, which are projected to increase in the 21st century predicted by future climate change scenarios for Central Europe.     

针对复杂地形的遥感干旱监测研究的可行性分析

2008年以来，我国北方大部分地区发生严重干旱，监测精度的高低直接影响着防旱、抗旱工作的开展。由于目前我国还没有一套完善的干旱监测方法，使得干旱监测的精度问题一直存在。针对全国复杂地形，对其不同气候区的干旱情况应用不同的监测方法进行可行性分析，提出了一些新的理论和方法，一定程度上提高了监测精度，形成了一个较为完备的干旱监测体系。