Introduction

The realization of strategies for sustainable land use assumes specificresearch concepts from the local to the global scale (micro-, meso- andmacroscale). Therefore, landscape ecological science has to provideinvestigation methods for all these different scales. By combiningtop-down and bottom-up approaches in addition tocoupled GIS-model applications and traditional methods, the investigation oflandscape ecological structures and processes seems to be possible. Thepresented studies show this approach on examples of two study areas in EasternGermany: A watershed of 400 km² and an administrativedistrict of about 4000 km². The scale-specificapplicability of several models and methods were tested for theseinvestigations, and the validation of the calculated results are presented. Animportant outcome of the project should be the prevention of conflicts betweenagriculture, water management and soil, and water and nature conservation;based onrecommendations for land use variants with decreased pollutant loading withinagricultural areas. The scale specific investigations can be considered as abase for establishing sustainable land use.This revised version was published online in May 2005 with corrections to the Cover Date.     

An ecological risk assessment for spinosad use on cotton

Spinosad is a reduced-risk insecticide with a novel mode of action that provides an alternative to older classes of insecticides such as organophosphates, carbamates and pyrethroids. A comprehensive ecological risk assessment for spinosad use in US cotton crops is presented within a framework of tiered levels of refinement following the guidelines of the US EPA for ecological risk assessments. Toxicity information for a variety of species is documented and utilized, environmental concentrations estimated, and risk characterizations in the form of risk quotients are quantified. Results indicate that spinosad use in cotton does not exceed the most conservative Tier I levels of concern (LOC) values for groundwater, mammals and birds or acute risk to aquatic organisms. Use of very conservative Tier I screening methods resulted in exceeding LOC values for chronic exposure for some aquatic organisms, thus prompting further refinement. When the exposure prediction was refined using less conservative, Tier II mechanistic environmental fate transport models to predict offsite transport and environmental concentrations, chronic risk was not predicted for these species. Spinosad is acutely toxic to bees under laboratory conditions, but toxicity of residue studies and field studies indicate that under actual use conditions the impact on bees is minimal.     

AA肉鸡腿肌重活体估测方法的探讨

以AA肉鸡商品代为试验材料,分析0、7、14、21、28、35、42日龄公、母鸡整体和腿肌的累积生长,建立腿肌重(y)与活重(x)之间的直线回归、幂回归、指数回归、对数回归及多项式回归方程,探讨腿肌重的活体估测方法。结果表明,AA肉鸡的腿肌在后期生长迅速,尤其是公鸡在35～42日龄时期表现突出;腿肌重(y)与活重(x)的幂回归、直线回归、多项式回归方程的拟合精度均在0.95左右,效果较好。     

应用可拓学原理评价黄瓜根分泌物的化感潜势

 对黄瓜组培根分泌物的化感潜势进行可拓评价, 得出黄瓜组培根分泌物对菜豆幼苗生长有显著促进作用, 而对其它3种作物有明显的毒害作用, 毒害程度为黄瓜>甜瓜>番茄。同时, 建立了黄瓜组培根分泌液的化感效应的数学模型R_E = [ k₁R_p0 / ( k₂ - k₁ ) ] ( e^{- k1t} - e^{- k2t} ) ( e- ^k1a - e^{- k2a} ) , 说明了黄瓜组培根分泌液的化感效应与组培根培养时间( t) 以及根分泌液浓度( a) 显著相关。黄瓜根分泌物对4种受体作物显示出显著的化学干扰差异, 论证了植物种内(间) 发生的干扰作用与植物的品种(系) 有关, 从理论上得出菜豆可以作为黄瓜的间套作物或下茬作物。     

勺状亚侧耳菌丝培养特性的研究

研究了C源、N源、pH、温度和料水比及不同培养基对勺状亚侧耳(Hohenbuehelia petaloides)Hp.831菌丝生长的影响。试验结果表明,该菌丝生长的最适温度、pH、C源、N源和含水量分别为25～30℃、6～7、羧甲基纤维素钠、蛋白胨和60%～70%;马铃薯和松针的热水提取液可促进该菌菌丝生长;该菌菌丝在配方7培养料上长势最好,菌丝生长动态符合logistic方程:Y=109.6/(1 60.1131e-0.1894x)(y=菌丝生长长度mm,x=培养时间d)。     

Determining landscape extent for succession and disturbance simulation modeling

Dividing regions into manageable landscape units presents special problems in landscape ecology and land management. Ideally, a landscape should be large enough to capture a broad range of vegetation, environmental and disturbance dynamics, but small enough to be useful for focused management objectives. The purpose of this study was to determine the optimal landscape size to summarize ecological processes for two large land areas in the southwestern United States. We used a vegetation and disturbance dynamics model, LANDSUMv4, to simulate a set of nine scenarios involving systematically varied topography, map resolution, and model parameterizations of fire size and fire frequency. Spatial input data were supplied by the LANDscape FIRE Management Planning System (LANDFIRE) prototype project, an effort that will provide comprehensive and scientifically credible mid-scale data to support the National Fire Plan. We analyzed output from 2,000 year simulations to determine the thresholds of landscape condition based on the variability of burned area and dominant vegetation coverage. Results show that optimal landscape extent using burned area variability is approximately 100 km² depending on topography, map resolution, and model parameterization. Variability of dominant vegetation area is generally higher and the optimal landscape sizes are larger in comparison to those features determined from burned area. Using the LANDFIRE project as a case study, we determined landscape size and map resolution for a large mapping project, and showed that optimal landscape size depends upon geographical, ecological, and management context. This paper was written and prepared by U.S. Government employees on official time, and therefore is in the public domain and not subject to copyright. The use of trade or firm names in this paper is for reader information and does not imply endorsement by the U.S. Department of Agriculture of any product or service.     

44个柚品种果实Vc与酸含量回归关系的计算机拟合

根据1991-1994年连续4年观测资料的平均值,对44个柚品种果实Vc与酸含量的相关关系,通过计算机编程进行了直线方程、双曲线、指数函数、幂函数、对数函数、S型曲线和二次多项式曲线等8种常见方程式配合,确定了二次多项式Y=32.12-135.18X 50.43X~2(相关指数R=0.868)为其最适合的回归方程.另外,各年份间这种回归曲线图表现相对一致,更进一步证实柚品种基因型中果实VC与总酸含量之间确实存在着一种极显著而稳定的相关关系.     

农业引进技术消化吸收模型及其演化仿真

对于农业技术的引进,必须综合考虑技术应用地区的经济发展状况、市场规模以及其他影响技术消化吸收的要素.农户人力资本均等程度较高但均值较低的地区应引进应用难度系数较低的中间技术或者原始技术；人力资本均值较高且方差较大的地区则应引进应用难度系数较大的尖端技术或者先进技术.农业引进技术消化吸收的进程取决于农业技术扩散,而农业技术扩散同时受两种效应影响,即学习效应和研发推动效应.在学习效应推动下,对于农户人力资本方差较大的经济,在技术扩散早期扩散速度较快,而在技术扩散后期则扩散速度较慢.另一方面,在研发推动下,对于人力资本方差较小的经济,技术扩散较快.     

弧形流道结构参数对灌水器水力性能影响的数值模拟

应用计算流体动力学CFD数值软件FLUENT6.3,模拟了滴灌灌水器弧形及弧齿形二种结构形式流道的流场水力性能。结果表明,弧形流道的消能方式主要为沿程水头损失,弧形流道灌水器的流态指数在0.7左右,而弧齿形流道中存在许多流动漩涡区,因此,其消能方式主要为局部水头损失,弧齿形灌水器的流态指数在0.5左右。通过对比分析认为:弧齿形流道水力性能优于弧形流道,可以通过结构参数优化设计,减小0流速区域,强化旋涡区,提高弧齿形灌水器的水力性能与抗堵塞能力,灌水器设计中推荐采用弧齿形流道结构形式。     

种公鹿茸重性状与年龄相关的统计分析

本文探讨了我国人工选育的双阳梅花鹿和西丰梅花鹿品种、长白山梅花鹿品系、天山马鹿清原品系和乌兰坝东北马鹿等 5个品种品系种公鹿的茸重性状与鹿年龄的关系 ,结果表明 ,在一定年龄段 ,茸重性状与年龄之间呈强正相关并建立了相应的线性回归方程 ,为预测并比较茸鹿种公鹿各年龄时的茸重水平和制定茸重标准及早选种等提供了科学依据