禽蛋基本特性参数分析与试验

为了探讨与禽蛋大小头自动定向排列机理相关的基本特征参数分布和估算模型,测定了禽蛋的几何尺寸、质心位置、体积和质量,研究了禽蛋几何尺寸与体积、质量的关系。结果表明,禽蛋的几何尺寸和质量都呈正态分布;禽蛋质心位于禽蛋长径中点处,相对于长径与短径交点向小头侧偏移3～5 mm,质心位置称重法优于支撑法;用标准椭球体体积计算方法估算的3种禽蛋体积与实测体积相关性均在0.94以上;禽蛋质量与禽蛋估算体积的相关性优于与长径、短径、蛋形指数、禽蛋长径处椭圆面积的三元和一元线性回归,3种禽蛋质量模型的相关系数均在0.95以上。     

农田土壤颗粒尺寸分布分维及颗粒体积分数的空间变异性

盐渍土膜下滴灌过程中的土壤理化性质存在空间变异性,对灌溉管理有一定影响。该文根据3个不同尺度下土壤采样及颗粒尺寸分布（PSD）测定结果,探讨了土壤PSD分维和颗粒体积分数之间的定量关系,分析了各尺度和综合尺度下土壤PSD分维和颗粒体积分数的经典统计特征和地质统计特征,根据颗粒体积分数的半方差函数计算了不同尺度颗粒体积分数的分形维,并做出了等值线图。研究表明,土壤PSD分维与黏粒的体积分数呈正相关关系,黏粒体积分数增大引起PSD分维增加的原因在于细颗粒的比表面积比粗颗粒的大;各尺度土壤PSD分维及颗粒体积分数均无强变异特征;不同尺度下土壤PSD分形维的半方差函数中块金和基台值均非常低;50 m尺度土壤PSD分维和黏粒体积分数的等值线图具有类似的集中度和走势,而砂粒体积分数和粉粒体积分数则具有相反的集中度和走势。该研究说明土壤PSD分维和颗粒体积分数都有一定的尺度依赖性。     

华北土石山区模拟降雨下土壤溅蚀研究

采取野外模拟降雨试验,研究了降雨强度、降雨动能以及降雨历时对溅蚀量的影响规律,分析了溅蚀土粒的距离、方位的分布特征,以及溅蚀土粒的粒径组成规律。研究结果表明:雨滴击溅过程中,在不同强度的降雨作用下,下坡方向产生的溅蚀量最大,上坡方向产生的溅蚀量最小。溅蚀总搬运量与溅蚀净搬运量均与降雨强度呈正相关。溅蚀量与降雨强度呈指数函数关系,与降雨动能呈现线性函数关系。溅蚀率与降雨历时呈现指数函数关系。溅蚀土粒主要分布在0~10 cm,占溅蚀总搬运量的45.40%~57.75%,在50~60 cm内的溅蚀量所占比例不高于1.75%。溅蚀量与溅蚀距离呈负指数函数关系。溅蚀土粒径小于等于2 mm,溅蚀土粒中细砂粒和粗粉粒百分比与原状土壤较为接近,粗砂粒百分比远低于原状土壤,而粘粒百分比高于原状土壤,粉粒百分比低于原状土壤。溅蚀土粒中细砂粒(0.05~0.2 mm)最易于被溅蚀,而小粒径(小于0.002 mm)和大粒径(大于0.2 mm)土壤颗粒不易被溅蚀。当降雨强度足够大时,对于同种特征的土壤,溅蚀土粒存在稳定的粒径组成。当降雨强度保持不变时,溅蚀平均粒径随溅蚀距离的增加而变小。溅蚀距离在0~30 cm,溅蚀平均粒径的变化率较大;随溅蚀距离的不断增加,溅蚀平均粒径的变化率较小。     

不同空间粒度下地表水体分布格局多样性研究

选取河南省北部、中部和南部典型研究样区,将空间粒度方法引入并应用于地表水体多样性的研究中。在总结前人研究水体多样性测度方法的基础上,提出新的方法——空间分布长度指数(MSHDLI),并在1 km×1 km网格尺度下研究MSHDLI、水网密度(RD)和空间分布面积指数(MSHDAI)的粒度效应、相关性和相关系数的粒度响应、尺度效应关系及回归模型。结果表明:随着粒度的增加,MSHDLI、RD和MSHDAI的粒度响应曲线均为下降型;MSHDLI与RD和MSHDAI有显著的相关关系,平均相关系数r分别为0.997和0.878(P0.01),且MSHDLI与RD、MSHDAI相关系数的粒度效应属于显著正相关关系;MSHDLI与RD的拟合度函数均是对数函数,MSHDLI与MSHDAI的拟合度函数均是多项式函数;由三者的多元线性回归模型可知MSHDLI与RD、MSHDAI线性相关且对它们的解释程度达到95%以上。MSHDLI可以将RD描述水资源广度和MSHDAI描述水资源空间分布离散性的优势结合起来。     

基于2DVD的非旋转折射式喷头水滴直径分布规律

采用基于三维视频粒子测量原理的视频雨滴谱仪(Two-dimensional video disdrometer,2DVD)对喷灌机中常用的Nelson D3000型喷头在多个工作压力下水滴直径沿射程的分布进行了测量,分析了水滴直径沿射程的变化趋势及水滴速度、水滴角度与水滴直径之间的关系。结果表明:水滴直径与射程符合指数函数关系,在距离喷头相同测点处,水滴直径随工作压力的升高而减小,而射程末端的水滴直径随着压力的升高而增大;水滴速度随水滴直径增加而增大,两者呈对数关系;水滴落地时与地面夹角(简称水滴角度)随水滴直径增加呈减小趋势,水滴直径小于1.0 mm时,50、100、150和200 kPa工作压力下,与地面夹角为90°的水滴个数占总水滴数的比值分别为90.46%、84.46%、89.91%和89.15%,其余水滴与地面夹角在30°~89°之间,水滴直径在1.0~2.25 mm范围内,水滴角度随水滴直径的增加迅速减小,水滴直径大于2.25 mm时减小趋势变缓,4个工作压力下最大直径水滴落地时与地面夹角平均值为45°;工作压力对于水滴直径与速度、水滴直径与角度之间的关系影响较小。     

柴油理化特性对高压共轨柴油机微粒粒度分布的影响

利用TSI EEPS3090微粒粒度测试系统,试验研究了高压共轨柴油机燃用不同理化特性调和柴油时的微粒成分及微粒排放粒度分布特征,揭示了燃料着火性能及燃料组分对微粒排放特性的影响规律。研究结果表明,对于不同着火性能的燃料,中小负荷工况下微粒数量浓度分布曲线大致呈单峰结构,峰值位于30nm附近,排气中绝大多数微粒粒径处于5~300nm之间。适当提高燃料十六烷值,能够缩短滞燃期,增大扩散燃烧期比例,有助于减少核态微粒的排放数量。同时,燃料含硫量对核态微粒排放影响较大,含硫量高将导致核态微粒排放量增加。随十六烷值增加,排气微粒中可溶性有机物质（SOF）比例减小,干碳烟（DS）比例上升。     

土壤不同粒级中C、N、P、K的分配及N的有效性研究

本试验首先把７种采自不同省份的耕作土壤进行物理分级,然后测定了土壤Ｃ、Ｎ、Ｐ、Ｋ在不同粒级中的分布,同时还进行不同粒有中Ｎ的有效笥研究。结果表明：在不同粒级中Ｃ、Ｎ含量和分布均随土壤颗粒的加粗而逐渐下降,血Ｃ／Ｎ比则与此相反。在〈２μｍ粒级中Ｎ的有效性最高,随着土壤颗粒粒和戏的加粗有效性逐渐降低,在酸性土壤中Ｐ主要分布在较细的粒级中,而在石灰性土壤中则粗有效性逐渐降低。在酸性土壤中Ｐ主要分布在较细     

轻小型移动式喷灌机组现状及其与国外的差距

节水灌溉是农业现代化的重要组成部分，发展节水灌溉、提高水的利用率是实现农业现代化的必由之路。通过对国内相关厂家的调研，初步分析了我国轻小型移动式喷灌机组的现状及其与国外先进水平之间存在的差距。在此基础上，提出了今后研究工作的具体目标。     

Aggregation studied by laser diffraction in relation to plowing and liming in the Cerrado region in Brazil

In the Cerrado savanna region in Brazil, the effects of different land use on Oxisol aggregation were studied using laser diffraction grain size analyses. The topsoil of plowed systems had significantly lower amount of macroaggregates (2000–194 μm) and a significantly higher amount of soil in the microaggregate size and primary particle fraction (<76 μm) compared to pastures and the native Cerrado. In plowed systems low in soil organic carbon (SOC), lime had a negative effect on aggregate stability. Lime addition had no effect on topsoil aggregation in land use systems that were not plowed regularly and generally had a higher SOC content. For all the studied topsoils, pH_KCl was positively correlated with the amount of clay dispersed after 3 h of shaking in water. SOC did not influence clay dispersion in the range of soils studied. In continuous cropping systems in the Cerrado region, with a combination of mechanical stress and low SOC, liming will cause an increase in small aggregates and primary particles and hence contribute to a destabilization of the soil structure.     

Estimates of minimum viable population sizes for vertebrates and factors influencing those estimates

Population size is a major determinant of extinction risk. However, controversy remains as to how large populations need to be to ensure persistence. It is generally believed that minimum viable population sizes (MVPs) would be highly specific, depending on the environmental and life history characteristics of the species. We used population viability analysis to estimate MVPs for 102 species. We define a minimum viable population size as one with a 99% probability of persistence for 40 generations. The models are comprehensive and include age-structure, catastrophes, demographic stochasticity, environmental stochasticity, and inbreeding depression. The mean and median estimates of MVP were 7316 and 5816 adults, respectively. This is slightly larger than, but in general agreement with, previous estimates of MVP. MVPs did not differ significantly among major taxa, or with latitude or trophic level, but were negatively correlated with population growth rate and positively correlated with the length of the study used to parameterize the model. A doubling of study duration increased the estimated MVP by approximately 67%. The increase in extinction risk is associated with greater temporal variation in population size for models built from longer data sets. Short-term studies consistently underestimate the true variances for demographic parameters in populations. Thus, the lack of long-term studies for endangered species leads to widespread underestimation of extinction risk. The results of our simulations suggest that conservation programs, for wild populations, need to be designed to conserve habitat capable of supporting approximately 7000 adult vertebrates in order to ensure long-term persistence.