Assessing the potential impacts of alternative landscape designs on amphibian population dynamics

An individual-based, spatially explicit population model was used to predict the consequences of future land-use alternatives for populations of four amphibian species in two central Iowa (midwest USA) agricultural watersheds. The model included both breeding and upland habitat and incorporated effects of climatic variation and demographic stochasticity. Data requirements of the model include life history characteristics, dispersal behavior, habitat affinities, as well as land use and landcover in geographic information systems databases. Future scenarios were ranked according to change in breeder abundance, saturation, and distribution, compared to baseline conditions. Sensitivity of simulation results to changes in model parameters was also examined. Simulated results suggest that while all four species modeled are likely to persist under present and future scenario conditions, two may be more at risk from future landscape change. Although the study species are all widespread generalists regarded as having a low conservation priority, they depend on wetlands and ponds, increasingly endangered habitats in agricultural landscapes. Broader conservation strategies in the region would ensure that these currently common organisms do not become the endangered species of the future.This revised version was published online in May 2005 with corrections to the Cover Date.     

Simulating evolution of glyphosate resistance in Lolium rigidum II: past, present and future glyphosate use in Australian cropping

Glyphosate is a key component of weed control strategies in Australia and worldwide. Despite widespread and frequent use, evolved resistance to glyphosate is rare. A herbicide resistance model, parameterized for Lolium rigidum has been used to perform a number of simulations to compare predicted rates of evolution of glyphosate resistance under past, present and projected future use strategies. In a 30‐year wheat, lupin, wheat, oilseed rape crop rotation with minimum tillage (100% shallow depth soil disturbance at sowing) and annual use of glyphosate pre‐sowing, L. rigidum control was sustainable with no predicted glyphosate resistance. When the crop establishment system was changed to annual no‐tillage (15% soil disturbance at sowing), glyphosate resistance was predicted in 90% of populations, with resistance becoming apparent after between 10 and 18 years when sowing was delayed. Resistance was predicted in 20% of populations after 25–30 years with early sowing. Risks of glyphosate resistance could be reduced by rotating between no‐tillage and minimum‐tillage establishment systems, or by rotating between glyphosate and paraquat for pre‐sowing weed control. The double knockdown strategy (sequential full rate applications of glyphosate and paraquat) reduced risks of glyphosate and paraquat resistance to <2%. Introduction of glyphosate‐resistant oilseed rape significantly increased predicted risks of glyphosate resistance in no‐tillage systems even when the double knockdown was practised. These increased risks could be offset by high crop sowing rates and weed seed collection at harvest. When no selective herbicides were available in wheat crops, the introduction of glyphosate‐resistant oilseed rape necessitated a return to a minimum‐tillage crop establishment system.     

桃品种需冷量评价模式的探讨

 通过1986～2001年对450余份桃品种需冷量的7．2℃模式、0～7．2℃模式(不包括0℃)和犹它模式比较分析，归纳出桃品种需冷量的评价模式为：以秋季日平均温度稳定低于7．2~C的日期为需冷量测定的起点，以0～7．2℃累积低温值作为需冷量的评价标准比较适宜；犹它模式在中需冷量和长需冷量范围内能有效预测休眠的结束，而不适宜低需冷量品种的测定；7．2℃模式不适宜作为需冷量的评价模式。品种的需冷量与叶芽开放和始花期的相关系数分别为0．52和0．58，均达到极显著水平。提出了桃品种需冷量评价的系列标准参照品种。     

Using traffic flow theory to model traffic mortality in mammals

Traffic has a considerable effect on population and community dynamics through the disruption and fragmentation of habitat and traffic mortality. This paper deals with a systematic way to acquire knowledge about the probabilities of successful road crossing by mammals and what characteristics affect this traversability. We derive a model from traffic flow theory to estimate traffic mortality in mammals related to relevant road, traffic and species characteristics. The probability of successful road crossing is determined by the pavement width of the road, traffic volume, traversing speed of the mammals and their body length. We include the traversability model in a simple two-patch population model to explore the effects of these road, traffic and species characteristics on population dynamics. Analysis of the models show that, for our parameter ranges, traffic volume and traversing speed have the largest effect on traffic mortality. The population size is especially negatively affected when roads have to be crossed during the daily movements. These predictions could be useful to determine the expected effectiveness of mitigating measures relative to the current situation. Mitigating measures might alter the road and traffic characteristics. The effects of these changes on traffic mortality and population dynamics could be analysed by calculating the number of traffic victims before and after the mitigating measures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Body weight growth Model of Datong Yak in Qinghai

Summary:This study was conducted to develop a suitable model for describing the growth pattern of the yak. The data used consisted of body weight records of 76 growing yak aged between 5 to 37 months. Three mathematical models were applied to describe the growth curves during this development period:①Y1=20.105 + 11. 250x-0. 526x2 ;used for describing the growth curve of yak aged 5 to 13 months;②Y2 = -359.687 + 49. 977x - 1. 249x2 ;used for animals aged 13 to 25 months;and ③Y3 = -833. 339 + 63. 772x - 1. 019x2 ;used for animals aged 25 to 37 months.     

Effect of dasatinib in a xenograft mouse model of canine histiocytic sarcoma and in vitro expression status of its potential target EPHA2

Canine histiocytic sarcoma (HS) is an aggressive and highly metastatic tumor. Previously, the kinase inhibitor dasatinib was shown to have potent growth inhibitory activity against HS cells in vitro, possibly via targeting the EPHA2 receptor. Here, the in vivo effect of dasatinib in HS cells was investigated using a xenograft mouse model. Moreover, the expression status of EPHA2 was examined in six HS cell lines, ranging from insensitive to highly sensitive to dasatinib. In the HS xenograft mouse model, dasatinib significantly suppressed tumor growth, as illustrated by a decrease in mitotic and Ki67 indices and an increase in apoptotic index in tumor tissues. On Western blot analysis, EPHA2 was only weakly detected in all HS cell lines, regardless of sensitivity to dasatinib. Dasatinib likely results in the inhibition of xenograft tumor growth via a mechanism other than targeting EPHA2. The findings of this study suggest that dasatinib is a targeted therapy drug worthy of further exploration for the treatment of canine HS.     

畜禽粪污资源化利用模式能值评价与比较分析——以新疆呼图壁县为例

基于典型案例,采用能值分析法对沼气工程模式、生物有机肥生产模式和堆积发酵还田模式进行定量的能值评价、分析及比较.结果 表明:三种模式从成本、生产效率、自我支持能力、处理废弃物能力、对环境的压力等方面来看效益都较好.但在系统自组织能力、可持续性方面,生物有机肥模式和堆积发酵还田模式效益均差、沼气工程模式效益最好.并认为应...     

增减施有机肥对红壤性水稻土团聚体稳定性及胶结物的影响

利用具有35a的长期定位试验,在保证原定位试验继续正常开展的前提下,将原化肥处理改施有机肥,原有机肥处理改施化肥或增施有机肥,分析增减施有机肥后耕层土壤团聚体稳定性总有机碳(TOC)及其组分和铁铝氧化物的变化与作用关系,探究胶结物对红壤性水稻土团聚体稳定性变化的影响。结果表明:化肥(CF)及常量有机肥(NOM)处理增施有机肥后,团聚体平均重量直径(MWD)变化不明显,易氧化有机碳(EOC)分别升高87.44%和20.53%;高量有机肥(HOM)及NOM处理减施有机肥后,MWD分别显著降低8.39%和6.80%,高改化(H-C)处理的TOC、轻组有机碳(LFOC)及粗颗粒态有机碳(cPOC)含量显著降低,而常改化(N-C)处理的TOC及其组分变化不明显。无论增施还是减施有机肥,铁铝氧化物含量的变化规律不明显。相关及结构方程模型分析表明,大于0.25mm团聚体含量是影响团聚体稳定性的唯一直接影响因素;影响MWD及大于0.25mm团聚体含量的效应系数由大到小依次为:易氧化有机碳、轻组有机碳、游离氧化铁、络合态铁。因此,大于0.25mm大团聚体在红壤性水稻土的团聚体稳定性中发挥主导作用,有机碳...     

土壤有机碳循环研究进展

阐述了国内外土壤有机碳含量模型、循环机理和影响因素等方面的研究进展和土壤有机碳循环研究中最新的理论成果。     

小麦条锈病气象预测方法及遥感监测研究进展

从影响小麦条锈病发生发展的大尺度气候背景、局地气象因子两方面,对小麦条锈病发生发展的气象预测研究进行了综述,指出了常规预测方法存在的问题和难点。概述了高光谱遥感在小麦条锈病监测中的应用,并对遥感与作物模型的结合进行了探讨,在此基础上展望了基于大气环流的小麦条锈病中、长期预测及G IS辅助的遥感技术在小麦条锈病监测方面的应用前景。