景观生态学原理与方法在荒漠化研究中应用的理论分析

荒漠化发生发展的过程实际上是指在自然和人为因素的作用下，生态系统结构遭受破坏、功能过程受阻和演变发生异化的过程，其防治的根本措施是恢复和重建健康的生态系统。所以，景观生态学理念在荒漠化的研究和防治中有着重要的意义。本文从荒漠化与生态系统结构、功能变化、荒漠化与生物多样性、荒漠化生态系统的物质循环和能量流动以及荒漠化生态系统的稳定性等方面论述了景观生态学理念在荒漠化研究中应用的可行性，并重点分析了景观生态学关于景观格局变化的评价指标与荒漠化土地动态变化之间的关系。     

有机修饰改性对旱地土壤吸附镉离子特性的影响

研究了以不同比例十六烷基三甲基溴化铵(CTMAB)单一修饰和十六烷基三甲基溴化铵 十二烷基磺酸钠(CTMAB SDS)混合修饰土娄土耕层对重金属镉离子吸附的影响,结果表明:吸附量顺序为耕层原土>50%CTMAB>100%CTMAB 20%SDS>100%CTMAB,温度升高,吸附量上升;最佳吸附等温线模型可以用BET模型描述,热力学参数的研究表明,吸附自发性与吸附量具有相同的变化规律,反应的焓变与熵变共同决定了反应的自发性。从热力学角度对修饰改性土娄土对Cd2 吸附的机理进行了探讨。     

Functional heterogeneity in resources within landscapes and herbivore population dynamics

Large mammalian herbivores are notorious for their propensity towards population irruptions and crashes, yet many herbivore populations remain relatively stable. I explore how resource heterogeneity within landscapes dampens population instability, using a metaphysiological modelling approach considering patch state distributions. Resource heterogeneity is functionally stabilizing through spreading consumption away from preferred resources before these become critically depleted. Lower-quality resources act as a buffer against starvation during critical periods of the seasonal cycle. Enriching resource quality is destabilizing, even if patch diversity is maintained, because food quantity then becomes the limitation. The potential consequences of landscape fragmentation are explored using the Serengeti ecosystem, characterised by broadscale resource gradients, as a hypothetical example. Further insights provided by the model are illustrated with specific examples concerning the effects of patch scales and waterpoint distribution. A metaphysiological modelling approach enables the basic consequences of landscape heterogeneity to be distinguished from further effects that may arise from specific patch scales and configurations, without the distracting detail of spatially explicit models.     

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.     

The effect of non-inversion tillage and light availability on dispersal and spatial growth of Cynodon dactylon

The invasive ability of Cynodon dactylon is dependent on self dispersal and on cultivation practices. Tillage can seriously change patch biomass and spatial structure, spreading vegetative propagules of the weed. The objectives of this study were: (i) to quantify the effect on non‐inversion tillage on dispersal, establishment and colonization of C. dactylon and (ii) to propose a simple model considering soil cultivation effects and light availability on spatial growth of weed patches. Two experiments were carried out, exploring different soils and environmental conditions. Spatial distribution of vegetative units differed when tillage was conducted with different non‐inversion implements and could be described by simple functions. A minimum patch biomass seems necessary before vegetative structures are vulnerable to movement by cultivation. Only a small proportion of the biomass dispersed from original patches was able to establish. However, simulation showed that the area colonized by C. dactylon mostly increased by means of tillage dispersal, both with and without crop competition, in one growing cycle. It appears sensible to consider changing cultivation practices to reduce weed dispersal and to use crop competition for light to create unsuitable habitats limiting weed colonization.     

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.     

The construction and application of a population physiologically based pharmacokinetic model for methadone in Beagles and Greyhounds

Methadone is an opioid analgesic in veterinary and human medicine. To help develop appropriate pain management practices and to develop a quantitative model for predicting methadone dosimetry, a flow‐limited multiroute physiologically based pharmacokinetic (PBPK) model for methadone in dogs constructed with Berkeley Madonna? was developed. The model accounts for intravenous (IV), subcutaneous (SC), and oral administrations, and compartmentalizes the body into different components. This model was calibrated from plasma pharmacokinetic data after IV administration of methadone in Beagles and Greyhounds. The calibrated model was evaluated with independent data in both breeds of dogs. One advantage of this model is that most physiological parameter values for Greyhounds were taken directly from the original literature. The developed model simulates available pharmacokinetic data for plasma concentrations well for both breeds. After conducting regression analysis, all simulated datasets produced an R ² > 0.80 when compared to the measured plasma concentrations. Comparative analysis of the dosimetry of methadone between the breeds suggested that Greyhounds had ~50% lower 24‐hr area under the curve (AUC) of plasma or brain concentrations than in Beagles. Furthermore, population analysis was conducted with this study. This model can be used to predict methadone concentrations in multiple dog breeds using breed‐specific parameters.     

基于生态文明的半干旱区土地资源综合承载力评价研究

土地资源面积的有限性,位置固定性和区域差异性,造成了其供给稀缺性;而土地资源具有养育、支撑、资源和资产等功能,其需求旺盛;土地资源供给的稀缺性与社会需求的无限性之间存在矛盾。笔者运用经济学的总需求-总供给模型(AD-AS模型),立足生态文明角度,从供求方面对区域土地资源承载力进行探讨,以山西省大同市为案例区。研究结果表明:(1)由耕地需求量、建设用地需求量和生态用地需求量构成的土地资源综合承载力总需求,2011—2015年大同市土地综合承载力总需求分别为0.5309、0.5542、0.5770、0.5797和0.6030;其总体趋势增加;(2)由耕地支撑能力、建设用地支撑能力和生态支撑能力构成的土地综合承载力总供给,2011—2015年大同市土地综合承载力总供给分别为1.423、1.466、2.104、1.531和1.509;(3)2011—2015年大同市土地综合承载力处于超载,2013年超载最大,2015年超载最小,说明大同市的土地资源承载力超载现象在改善。运用此方法进行土地资源综合承载力评价,在土地资源承载力研究中更为科学和合理,使得人们更为关注生态文明,为建立社会、经济、生态和谐的人地关系提供了新的依据。