Factors affecting plant species distribution in hedgerows of southern Quebec

Woody linear features of farmlands have received much attention as pools of diversity in European countries, but they have, in comparison, been little considered in eastern North American ecological studies. Here, we evaluate the relative contribution of environmental conditions, history of management practices within hedgerows, and adjacent land-use on herb and shrub species distribution in woody hedgerows of agricultural landscapes of southern Quebec, Canada. We pay particular attention to the distribution of forest herbs and weed species and identify the main factors that explain their presence. We also evaluate the amount of spatial structuring in the species data and explanatory variables.Our results show significant differences in species composition related to the unique influence of all sets of factors considered. Adjacent land-use (from intensive crop to fallow land) remains the best predictor of overall species distribution, followed by environmental conditions and history of management practices. The probability of finding forest herbs in hedgerows increases as intensity of adjacent agricultural practices (from intensive crop to fallow land) decreases. Potential weed species, on the other hand, are more likely to be found within narrow hedgerows adjacent to the more intensively managed fields. We discuss the results in terms of the interactions between the different determinants of plant diversity in hedgerows and demonstrate the necessity to distinguish between multiple structuring factors to devise proper conservation strategies. Such strategies will have to take into account the ecological as well as the agricultural exploitation context in which linear features are found to be effective.     

土地集约经营的经济学原理及途径探讨

通过论述土地集约经营的基本涵义,运用现代西方经济学原理对土地集约利用的经济问题进行分析;并结合土地集约经营的内涵,分析了土地集约经营的主要影响因素;同时根据我国实际,探讨了实行农地和市地集约经营的主要途径。     

关于抗滑稳定安全系数K的讨论

在具体使用刚体极限平衡分析法进行各种抗滑稳定分析时,由于对抗滑力(矩)和滑动力(矩)的认识不同,使所得抗滑稳定安全系数值有所差异。本文就抗滑稳定安全系数定义的物理概念及其合理性进行了讨论。     

植物叶缘锯齿发育调控的研究进展

叶片是植物重要的营养器官,叶片的形成模式和发育涉及激素信号和转录因子间复杂遗传网络的调控。叶缘锯齿的产生是植物对不同环境长期适应的结果,对植物应对高温、干旱等逆境胁迫及响应光周期都有十分重要的作用。为了更清晰地认识植物叶缘锯齿的发育过程,本研究对植物叶缘锯齿形成过程中重要的调控因子及其调控机制进行了分类和总结。叶缘锯齿的发育受生长素、细胞分裂素、赤霉素等植物激素,NAM/CUC、TCP、SPL等转录因子,KNOX基因家族及其他调节因子的调控,并在单叶和复叶植物中表现出明显不同的调控模式。植物叶缘锯齿发育仍有很多未知的调控因子,因此,未来一个重要的研究方向就是要继续挖掘和鉴定更多参与植物叶缘锯齿发育的调控因子,并进一步解析其作用的分子机制,从而为今后通过调控叶形为其他作物性状改良提供理论依据。     

青海湖芨芨草干草原浅层土壤温度和导温率的基本特征

通过解析芨芨草(Achnatherum splendens)干草原原生植被生长季中期5、10、20、40、60和80cm 6个土层连续监测的土壤温度资料,探讨其生长季土壤温度和土壤导温率的基本特征。结果表明:芨芨草干草原表层(<20cm)土壤温度日变化明显,遵循正弦波动规律;20-40cm为正弦波动和线性振荡的过渡层,40cm以下无显著日变化。土壤温度日变化振幅(A)和相位(φ)随土壤深度(z)增加分别呈现几何级数衰减(A=4.60e-6.74z,R2=0.93)和线性延迟(φ=6.14z+7.67,R2=0.95)模式;表层土壤温度对脉冲式降水表现为渐变式响应并出现同温层;典型晴天下土壤导温率(κ)随土壤深度增加而指数升高(κ=2×10-7e4.21z,R2=0.92),34.7cm土层的土壤温度日变化与5.0cm反相,而土壤温度日变化恒温层为86.0-102.0cm土层。     

星豹蛛在丘陵山地的活动规律初步研究

用陷阱法和目测法对丘陵区各个栖境的星豹蛛Pardosa astrigera C．L．Koch(Ly- cosidae：Pardosa C．L．Koch)做了初步调查研究,结果表明,星豹蛛5月下旬前主要在边界、沟渠、碎石路和斜坡处活动,而苹果园中相对较少。当边界、沟渠和碎石路植被长高后,星豹蛛迁移至周围的苹果园中。6月下旬7月下旬苹果园中星豹蛛受高温影响数量下降明显；8月下9月其数量又有较大回升。研究还发现,10月中下旬星豹蛛在背阴地带出现的频率明显少于光照较好的地带；同期星豹蛛可能还有趋向干枯杂草的习性。     

祁连山冷龙岭北麓冰川缘地文冠果引种栽培

在祁连山冷龙岭北麓冰川缘地——中牧甘肃山丹马场海拔高度不同的5个试验地(海拔分别为2 560、2 900、2 800、2 500、2 480 m,分别记作spot i,i=0,…,4))引种文冠果.结果表明:1～3年生文冠果播种苗平均苗高由高到低顺序:spot 0＞spot 3＞spot 4＞spot 2＞spot 1,其中spot 1播种苗、插根苗和移植苗连年生长量为零,spot 2苗木连年生长量部分为零.5个试验点的播种苗、插根苗、移植苗地下部分越冬成活率均达到100％.苗木平均枯梢率由大到小依次为spot 1＞spot 2＞spot 4＞spot 0＞spot 3.其中移植苗的枯梢较播种苗轻.在试验地发现文冠果苗木有黄化病和立枯病.spot 3、spot 0、spot 4所在地较适合文冠果的栽培,4年生播种苗在样地3只有1株结果,5年生时无开花及结果的情况.     

尤溪县林缘山脚田边生物防火林带建设现状与对策

阐述尤溪县林缘山脚田边生物防火林带建设基本情况,以及设置山脚田边生物防火林带的重要性、山脚田边生物防火林带在防火中的作用,提出营造山脚田边生物防火林带的对策措施,为今后进一步推动山脚田边生物防火林带建设提供参考。     

Relationships between dairy cow mastitis and fertility management and farm performance

A field study was carried out on 38 dairy farms in the Netherlands to determine the relationship between mastitis and fertility management with 305-day milk production and gross margin. Questionnaires were used to get insight into the farmers' management. Out of 150 variables related to mastitis and fertility management, and technical and economic results, 44 variables were selected based on correlation of ≥0.25 or ≤−0.25 with milk production and/or gross margin. These variables were used in two separate partial least-squares (PLS) analyses. PLS has the advantage that it can handle a large number of variables in relation to the number of cases. The PLS-model of 305-day milk production had R² = 0.54 and showed a positive relation between 305-day milk production and awareness of the farmer regarding bulk somatic-cell count (BSCC), the goal level of the farmer for BSCC, and hygiene of the milking parlour. Fertility was negatively related to 305-day milk production, in spite of a relatively good fertility management on high-producing farms. R² = 0.46 for gross margin. The aspiration level of fertility did not seem to affect gross margin, but awareness of BSCC and calving interval (CI) had positive effects. Such awareness seemed a general parameter for good economic results, because it was correlated with different aspects of gross margin.     

公路边坡稳定性分析及防治措施

内蒙古集呼高速公路K450段地处丘陵地区,以路堑形式通过,施工中发现坡体岩土结构较复杂,雨季后期,该段突然发生滑动破坏,本文对边坡稳定问题进行了研究,分析了产生边坡稳定的主要原因,对边坡稳定提出了相应的整治措施,收到了良好的效果。