基于两层次线性混合效应模型的杉木林单木胸径生长量模型   总被引：8，自引：0，他引：8  

李春明 《林业科学》2012,48(3):66-73

基于两层次线性混合效应模型方法,建立江西省杉木人工林单木胸径生长量模型.研究所用数据来自于长期观测的固定样地数据,数据库包括82个区域、365个样地、5416株树木共计16248条记录.为了解决不同区域及不同样地之间的差异,本文构建的混合模型分别考虑样地层次、区域层次及两层次的随机参数效应.针对数据存在的重复测量及嵌套结构特性,在模拟时选择合适的异方差和自相关模型矩阵来解决此类问题.最后利用独立的抽样验证数据对模拟结果进行验证.结果表明:林分断面积、对象木胸径、林分内大于对象木的断面积之和与对象木胸径的比值以及海拔对单木胸径生长量有显著影响.与林业中常用的传统最小二乘方法相比,采用混合效应模型方法后模型的模拟精度和验证精度均有提高.选择适合的异方差和自相关函数后,模型比只考虑参数的随机效应有更好的适应性,并体现出了混合效应模型的灵活性和准确性.  相似文献   

Management of calving in Norwegian cubicle-housed dairy herds.     

H P Kjaestad  E Simensen 《Acta veterinaria Scandinavica》2001,42(1):131-137

Sixty of the 65 dairy farms with cubicle houses in the Norwegian county of Oppland were included in a field study of the management of calving in 1990. The farmers recorded the location of the cow when giving birth, farmer presence and whether assistance was given during calving, occurrence of suckling, and time after birth when cow and calf were separated. Such data were recorded for a total of 1125 calvings. About 10% occurred on pasture, while 78% of the remaining calvings took place in the cubicle-equipped section. Thirteen percent calved in a calving pen, the remaining cows being tethered at the time of calving. Thirty-two percent of the calvings took place in houses lacking a calving pen altogether. Farmers were present during 41% of the calvings. Suckling most frequently occurred after pasture calvings, and was least frequent after calvings within the cubicle-equipped section of the cowhouse. Injuries to the calf caused by trampling or contact with fittings etc. were rare, and no more common in association with calving in the cubicle-equipped section than with calving taking place with the cow isolated from the rest of the herd. All calves were removed from their dams within 24 h after birth.  相似文献   

Contribution of a straw bedding to digestible nutrient intake of pigs fed diets based on either native or pregelatinized potato starch     

S.T.M. Staals  J.E. Bolhuis  H. van den Brand  W.J.J. Gerrits   《Livestock Science》2007,109(1-3):104-107

In a 2 × 2 factorial arrangement, 16 groups of 12 pigs were assigned to one of two housing systems (straw bedding, S vs. Barren, B) and to one of two starch types (native, N vs. pregelatinized potato starch, P, each included at 35%) to study effects on apparent faecal digestible nutrient intakes. Intake of straw from bedding material was estimated, using several markers, and results are discussed. Straw intake of the S-pigs was estimated between 143 and 234 g DM/d for P-pigs and between 96 and 156 g DM/d for N-pigs, depending on the method used. Nutrient digestibility was reduced in N-pigs when compared with P-pigs. Intake of digestible dry matter, energy, starch and ADF was increased in S-pigs, but the intake of digestible protein was reduced. Despite greatly reduced nutrient digestibility in S-pigs, additional digestible nutrient intake due to housing on a straw bedding can be considerable.  相似文献   

佳木斯市保障性住房建设浅析     

孙力伟 《林业科技情报》2013,45(2):80-81

东北边陲名城佳木斯市于2011～2012年建设规模近90万m2的保障性住房工程,此工程解决了当地近三万中低收入居民的居住问题,本项目是扶持城市居民住房困难群体政策性补助工程,具有良好的社会效益。  相似文献   

跃层式住宅设计探讨     

邹卫红 《湖南农业大学学报(自然科学版)》2000,(3)

论述了跃层式住宅诞生的必然性及优越性,提出了跃层式住宅的设计原则.  相似文献   

意大利蜜蜂近距离采蜜量与工蜂日龄的关系     

周冰峰  王秀红  刘宏艳  杨和平 《福建农林大学学报(自然科学版)》1999,28(2):1

在距蜂箱１０ ｍ 的地点放置质量浓度为０．７５ ｋｇ· Ｌ－ ３的蔗糖液，以测定各日龄意蜂的个体采蜜量．结果表明，采集蜂最小日龄为３ 日龄，１３～２７ 日龄段的工蜂采蜜量最高，每只蜜蜂每次采集６９．４４～７５．２５ ｍ ｇ；１２ 日龄以前的标记蜂采蜜量不稳定，随着日龄的增长逐渐趋于稳定；在测定地点，标记蜂１１ 日龄开始明显增多，直到２８ 日龄后减少．根据实验结果可以初步判定，近距离采集的适龄采蜜蜂为 １３～２７ 日龄．此项研究结果对蜜蜂饲养管理技术的改进有重要参考价值．  相似文献   

Seasonal stream habitat of adult Sakhalin taimen,Parahucho perryi,in the Bekanbeushi River system,eastern Hokkaido,Japan     

Kentaro Honda  Haruka Kagiwada  Nobuyuki Takahashi  Kazushi Miyashita 《Ecology of Freshwater Fish》2012,21(4):640-657

Behavioural tracking of endangered adult Sakhalin taimen (Parahucho perryi) by acoustic telemetry was conducted in the Bekanbeushi River system that flows through eastern Hokkaido in 2008–2010. A total of 39 tracked P. perryi showed extensive use of the river system, both upstream and downstream, regardless of the month or year. No tracked adult P. perryi stayed in the ocean for more than 1 day. Some of the fish (20%) dwelled in upstream habitat consistently from spring to autumn, while 40% of individuals showed wide utilisation of the entire upstream and downstream systems. Although 39.4% of tracked fish utilised two or more primary tributaries to the main river, 6.1% used only the main river system. Distinct variability was observed between individuals based on the proportion of time spent in each stream reach (up‐, mid‐, and downstream). A trend was observed in 2008 and 2010 showing that tracked fish moved to the upper stream reaches when water temperatures downstream increased. This trend was not observed in 2009 when the summer water temperature downstream was more than 2 °C below average when compared to 2008 and 2010. Our results suggest that adult P. perryi in the Bekanbeushi River system exhibit high behavioural plasticity, that is, the fish can select habitats based on their own individual requirements. Our results also demonstrate the importance of physical continuity among river reaches both upstream and downstream such that P. perryi does not experience barriers in moving to optimal habitats.  相似文献   

论个群目标一致性机理及和谐管理路径     

赵含韫 《安徽农业大学学报》2004,(1):70-74

个体目标与群体目标的矛盾是管理过程中的一项基本矛盾。个体与群体之间的相互依存和相互作用表明了在尊重个体需要的同时，可以实现个群目标的一致性，而这只有通过提倡以人为本的管理思想，实行和谐管理才能实现。  相似文献   

银杏叶用品种的初步筛选研究   总被引：1，自引：0，他引：1  

陈法志  杨守坤  陈宝林 《湖北林业科技》2002,(1):11-13

通过对收集的１６个银杏优良单株４年生嫁接苗的叶产量、黄酮含量进行初步比较研究，结果表明：不同单株间叶产量、黄酮含量存在显著差异；银杏植株各器官中黄酮合量以芽最高，叶次之，根枝较低。综合分析表明：ＷＬ１６８号表现最优，其次为桂林３号等，可在生产中推广应用。  相似文献   

黑琥珀李株和冠幅与土壤养分相关的研究     

柳春华  廖永平  曾秋敏  吕伟仲  王平  陈伟祥  张鑫燕 《浙江林业科技》2001,21(4):21-24

应用逐步回归和通径分析，对土壤养分与黑琥珀李株产和冠幅增长的相关关系进行了研究，结果表明，土壤的机质，水解氮，速效磷和速效钾4个养分因子对黑琥珀李株产和冠幅的增长都有着显著和极显著的相关关系，其中以速效磷对产量和冠幅的增长作用最为显著，并且4种土壤养分因子之间存在着相互关联，互为作用的关系，因此，旋肥时应各种营养元素综合考虑，不能偏施。  相似文献