利用模糊数学方法预测秋白菜适宜收获期     

吉奇 《安徽农业科学》2010,38(18):9387-9388,9399

依据秋白菜受冻的日最低气温指标,利用本溪市1957～2008年逐日最低气温资料,应用模糊数学隶属度函数预测日最低≤-7℃的初日趋势,建立多元回归模型预测日最低气温≤-7℃初日,为指导秋白菜适时收获、合理安排上期提供科学的气象依据。  相似文献   

供水系统数值模拟   总被引：1，自引：0，他引：1  

薛国新  路淼  肖立川 《排灌机械》2002,20(6):23-25

对供水系统的数值模拟计算进行了研究，一般地，管中的部分阻力参数可以通过实测而得到，但依据它们常不足以确定系统状态，为此，基于直流电路的计算方法，对样本数据使用最小二乘法，得到了一种确定管路未知阻力参数的模型，由此确定系统状态，该模型对于灌溉网等的设计具有参考价值。  相似文献   

线性回归分析中重复与非重复性问题研究     

刘建慧 《北京农学院学报》1998,13(3):94-99

本文就一元线性回归，分相同水平及不同水平两种情形，讨论了重复与非重复试验对回归方程精度的影响，得到如下结论：相同水平序列下，重复试验的回归精度高于非重复试验；不同水平序列下非重复试验的回归方程的精度在一定条件下可能高于重复试验，并给出了此时应满足的水平设置条件。  相似文献   

牛病毒性腹泻-粘膜病病毒地方株动物回归试验     

张宝宁  赵月兰  秦建华  郭红斌  包永占  田席荣 《中国农学通报》2007,23(3):15-18

【目的】自流产奶牛粪便及血液中分离得到的非细胞病变型牛病毒性腹泻-粘膜病病毒(BVDV),为了解分离毒株的特性,进行回归动物试验;【方法】将此分离毒回归2月龄健康犊牛,接毒25天后扑杀剖检,观察临床症状及病理变化。自犊牛体内采取脾、骨髓、肠淋巴结及血液接种MDBK细胞进行培养,分离病毒,进行细胞传代,将此细胞毒进行RT-PCR检测;【结果】犊牛表现为典型的急性病毒性腹泻症状和病变。自病料分离病毒经MDBK细胞盲传至第9代,均未出现细胞病变。将此细胞毒进行RT-PCR检测,扩增出相应的665bp的片段;【结论】将分离株接种易感犊牛以复制出BVD-MD病症,并从试验牛体内分离得到BVDV,从而进一步确证分离到的毒株属BVDV。  相似文献   

Assessment of rice leaf growth and nitrogen status by hyperspectral canopy reflectance and partial least square regression   总被引：9，自引：0，他引：9  

Hung T. Nguyen  Byun-Woo Lee   《European Journal of Agronomy》2006,24(4):349-356

  相似文献   

喀斯特小流域土壤饱和导水率垂直分布特征   总被引：9，自引：1，他引：9  

付同刚  陈洪松  王克林 《土壤学报》2015,52(3):538-546

土壤剖面饱和导水率(Saturated hydraulic conductivity,Ks)的垂直分布对土壤水文过程有极其重要的影响,但在地质背景特殊的喀斯特地区其研究还相对匮乏。通过测定典型喀斯特小流域内23个土壤剖面(0~10、10~20、20~30、30~50、50~70、70~100 cm)土壤Ks及土壤碎石含量(Rock fragment content,RC)、容重(Bulk density,BD)、毛管孔隙度(Capillary porosity,CP)、非毛管孔隙度(Non-capillary porosity,NCP)、土壤有机碳(Soil organic carbon,SOC)等土壤性质,并结合各样点的坡位(Slope position,SP)、坡度(Slope gradient,SG)、坡向(Slope aspect,SA)、裸岩率(Bare rock,BR)、土地利用类型(Land-use type,LU)等环境因素,应用偏相关分析和典范对应分析(CCA)的方法,研究了喀斯特小流域Ks的垂直分布特征及其主要影响因素。结果表明,Ks随土壤深度的增加而减小并可用对数函数模拟(R2=0.848)。20~100 cm各层Ks变幅较小且变异接近,因此在水文模型中可用20~30 cm土壤Ks代替深层。土壤性质中,RC与Ks的相关系数(0.484)最大。环境因素对Ks垂直分布的影响依次为SPSGSALUBR。由此可知,RC是影响Ks最重要的土壤性质,而SP则是影响Ks垂直分布最重要的环境因素。该结果有利于弄清喀斯特地区降雨入渗规律及其主要影响因素,为小流域植被恢复及水文模型的构建提供科学依据。  相似文献   

Bird communities, roads and development: prospects and constraints of applying empirical models     

Kevin J. Gutzwiller  Wylie C. Barrow Jr. 《Biological conservation》2003,113(2):239-243

Our objectives were to explain the prospects and constraints of applying empirical models that relate bird community metrics to broad-scale characteristics of roads and development. We explored the practical value of regression models that were derived for a large protected area in the Chihuahuan Desert. These models related bird species richness, relative abundance, or probability of occurrence to total length of roads within each of two spatial extents (1- and 2-km radii), distance to the nearest road, distance to the nearest development, or the two-way interactions of these variables. Empirical models can be used to inform conservation decisions, to parameterise simulation models for conservation planning, to identify threshold levels of road and development variables, and to determine the focus of management experiments for confirmatory hypothesis testing and improvement of model realism.  相似文献   

Breeding bird response to partially harvested riparian management zones     

Christopher J. Chizinski  Anna PetersonJoAnn Hanowski  Charles R. BlinnBruce Vondracek  Gerald Niemi 《Forest Ecology and Management》2011,261(11):1892-1900

We compared avian communities among three timber harvesting treatments in 45-m wide even-age riparian management zones (RMZs) placed between upland clearcuts and along one side of first- or second-order streams in northern Minnesota, USA. The RMZs had three treatments: (1) unharvested, (2) intermediate residual basal area (RBA) (targeted goal 11.5 m²/ha, realized 16.0 m²/ha), and (3) low RBA (targeted goal 5.7 m²/ha, realized 8.7 m²/ha). Surveys were conducted one year pre-harvest and three consecutive years post-harvest. There was no change in species richness, diversity, or total abundance associated with harvest but there were shifts in the types of birds within the community. In particular, White-throated Sparrows (Zonotrichia albicollis) and Chestnut-sided Warblers (Dendroica pensylvanica) increased while Ovenbirds (Seiurus aurocapilla) and Red-eyed Vireos (Vireo olivaceus) decreased. The decline of avian species associated with mature forest in the partially harvested treatments relative to controls indicates that maintaining an unharvested RMZ adjacent to an upland harvest may aid in maintaining avian species associated mature forest in Minnesota for at least three years post-harvest. However, our observations do not reflect reproductive success, which is an area for future research.  相似文献   

麻疯树人工林单木生物量与生产力模型研究     

何亚平  李建刚  李云秀  费世民  蔡小虎  王鹏 《四川林业科技》2011,32(3):5-17,4

回归分析法是构建单木生物量模型进而估算群体生物量的基本方法。本文研究了攀枝花市马店河一个麻疯树4年人工林生物量与生产力模型的构建过程,运用相关生长定律分析参数合理性,并筛选了适宜的模型构建参数。首先,用地径、高度、D2H、树冠直径、冠幅、枝下高、树冠垂直投影体积这些灌木生物量测定中经常采用的外部形态指标构建麻疯树单木生物量模型,得到拟合性最好的幂函数、抛物线、对数函数模型。其次,采用树体构型指标,如枝条数量（不同年龄枝级）与分支率（总体分支率、）参数构建单木生物量模型,得到相关性不等的幂函数、抛物线模型。用年龄平均法与直径增量法同时估算了麻疯树单木生产力,分别为Pa=4.93±3.92 kg.a-1,Pd=4.59±3.82 kg.a-1,方差分析差异不明显。经回归,获得单木生产力模型。通过排序,获得对生产力贡献较大的因子,并对筛选的因子进行多元回归,得到Y=∑AiXi（其中Ai为第i个常数,Xi为第i个变量,i为测定变量总个体）,提高了估算的精确度。分析表明,地径、冠幅直径、冠幅、冠幅垂直体积都能较为准确的估算单木生物量、生产力,但生殖生物量估算相关系数在0.8以下（0.607〈r2〈0.753）,精确度不高,表明生殖自身特性的独特性。  相似文献   

Genotypic differences of maize in grain yield response to deficit irrigation     

Harun Kaman  Cevat KirdaSertan Sesveren 《Agricultural Water Management》2011,98(5):801-807

This study was undertaken to investigate genotypic differences of five maize cultivars in grain yield response to two different modes of deficit irrigation, conventional deficit irrigation and partial root zone irrigation. Three irrigation treatments were implemented: (1) FULL irrigation, the control treatment where plant water requirement, 100% Class-A pan evaporation, was fully met and the furrows on both sides of the plant rows were irrigated; (2) partial root zone irrigation (PRI), 35% deficit irrigation, compared to FULL treatment, was applied in every other furrow thus irrigating only one side of the plant rows. The furrows irrigated were alternated every irrigation; (3) conventional deficit irrigation (CDI), the same amount of water as PRI was applied in furrows on both sides of the plant rows, similar to FULL irrigation treatment. Five maize cultivars (P.31.G.98, P.3394, Rx:9292, Tector and Tietar) showing extreme growth response to water stress were selected out of ten cultivars tested with earlier completed greenhouse-pot experiment. A split-plot experimental design, comprising three irrigation treatments and five maize cultivars with four replicates, was used during two years of work, in 2005 and 2006. Total of nine irrigations, with one-week irrigation interval, were annually applied using a drip-irrigation system. Soil water status was monitored using a neutron moisture gauge, in addition to measuring leaf water potential and above-ground biomass production throughout the growing season. Grain yield and other yield attributes were measured at harvest as well as assessing differences in plant root distributions. Decrease in grain yield and harvest index of the tested cultivars, compared to FULL treatment, was proportionally less under PRI than CDI. Whether or not a significant yield advantage can be obtained under PRI compared to CDI showed significant (P < 0.05) genotypic variability. Tector and Tietar among the tested cultivars of maize showed significantly higher grain yield (P < 0.05) under PRI than CDI. The yield advantage of the genotypes (P.3394 and Tector) under PRI compared to CDI seems related to their enhanced root biomass developed under PRI.  相似文献