海南岛尖峰岭热带森林蒸散*

本文用能量平衡-波文比法在海南岛尖峰岭地区对热带森林的蒸散进行三年早季和雨季49d的测定,测定数据用逐步回归法建立多元回归方程,把降雨量作为因变量置于回归方程中,引进新参数AWE表示可供蒸散的水分,计算出森林全年蒸散量,并用Penman-Monteith方程作对比,分别计算出森林每日蒸散值。其结果是:用EBBR法测定和计算的森林全年蒸散值分别为534.7mm(1983年)、520.7mm(1984年)和564.0mm(1985年),分别占年降雨量的30.4％、30.2％和44.9％。而用Penman-Monteith方程计算的森林全年蒸散值分别为721.1mm(1983年)、714.8mm(1984年)和728.4mm(1985年),分别占年降雨量的41.0％、41.5％和58.0％。用这两种方法计算的日平均蒸散的最小值分别是0.36mm和0.49mm,日平均蒸散的最大值分别为2.55mm和3.14 mm。     

Socio-economic factors affecting the income of small-scale agroforestry farms in hill country areas in Yemen: A comparison of OLS and WLS determinants

Yemen is a less-developed country in the Arabian Peninsula, with only 3% arable land. An agroforestry land-use system has been practiced traditionally by small-scale farmers, but is associated with low productivity and income. A study has been undertaken to determine the socio-economic attributes of farmers that influence the financial performance of agroforestry and non-agroforestry farms in the Bura’a Mountain region. A survey was conducted of 150 farmers involved in both agroforestry and non-agroforestry. Both OLS and WLS regression were applied, and coefficients compared in terms of consistency and goodness of fit. Incomes of farmers were found to be influenced by education, area of land, livestock holding, family size, and whether coffee is grown, but not farmer’s age. The WLS method produced efficient and consistent results, whereas OLS regression was affected by the heteroscedasticity. The findings of the study indicate that the farmers of the study area are in need of financial and technical support from government to increase their income. Infrastructural development and public intervention in developing farmers’ technical know-how could enhance production and ensure the optimum use of land as well as soil and water conservation.     

思茅松树脂道数量与产脂力回归关系研究

对35个思茅松高产脂嫁接无性系的树脂道个数进行测定,并对其与产脂力的关系进行回归分析。结果表明:树脂道个数与产脂力的相关关系较为紧密,经过对18个回归方程的拟合,得出树脂道个数与产脂力的最佳回归方程为:y=a+becx。     

Temporal development of crown condition of beech and oak as a response variable for integrated evaluations

The evaluation uses the longest available time series for beech and oak defoliation in Germany. The data from Hesse, starting from 1984, show a typical pattern: for the first 12 years, a continuous increase in defoliation was observed ranging from an average value of 14% in 1984 to a peak value of 30%. This was followed by a subsequent decrease in the loss of foliage accompanied by a high variability, until the last monitoring in 2003, where an average value of 25% defoliation was observed. For both tree species, the years of trend reversal were identical. The same pattern was observed in the German federal states: Rhineland-Palatinate, North Rhine-Westphalia, and Bavaria. The year of trend reversal was identical in Hesse and Rhineland-Palatinate. In North Rhine-Westphalia, it occurred 1 year earlier and in Bavaria 3 years earlier. Whereas defoliation trends were clearly demonstrated, tree mortality did not appear on a large scale. The sample trees were grouped into four discrete clusters according to their annual defoliation values from 1984 to 2003. In 1996, the clusters represent 15, 25, 35, and 50% defoliation values. Regarding beech in Hesse, there was no overlap in the defoliation curves observed among the different clusters. These four clusters having different degrees of defoliation over the whole time span of 20 years were used for a further detailed statistical analysis. For discrete variables like crown spacing and—in the case of beech—fruit bearing, mosaic plots were applied in order to visualize relations of low dimensional contingency tables, with defoliation trends being used as the response variable. The data show for beech a very clear relation between defoliation and age, relative crown spacing, stand composition, and fruit bearing. Regarding oak, besides age and relative crown spacing, the years with significant appearance of biotic stress factors—leaf eating insects—show a clear relation to trends of defoliation. The statistical model used in this study—logistic regression—allows applying a multinomial response variable and a number of continuous or categorical explanatory variables. With this approach, an iterative optimized selection of effect variables was used to test the relevance of different variables on the defoliation pattern of the same four clusters mentioned above. For this, the variables were grouped in an iterative process with five steps, starting with a few basic variables of tree and site information, and ending with a total of more than 20 variables in the fifth step. The process selects first the variables which are of significance on the defoliation, and calculates the possible errors in the grouping of the different trees to the four clusters. In this analysis of beech, the basic tree and stand variables: age, relative crown spacing, stand composition and fruit bearing proved to be the most relevant group of parameters, with the other variables explaining the variation of defoliation only to a minor extent. More complex model levels do not change any basic selected variables; however, Cation Exchange Capacity (CEC), C/N-ratio, Al- and Ca-proportion of CEC are additionally selected and give a hint of the relevance of soil conditions. Regarding beech, the errors of the statistical model are lower compared to oak.     

白榆无性系叶面积数学模型初步研究

对 2 5个白榆无性系叶片的长度 (X1)、宽度 (X2 )、面积 (Y)作了测量 ,采用最小二乘法分别求得每个白榆无性系叶片长度与面积、宽度与面积以及长宽与面积的回归方程及其相关系数 ,并对其进行了系统聚类分析 ,同时还通过多元回归求得白榆无性系叶面积通用模型 (Y =1 1754X10 74 2 1·X2 1 12 53 )。本研究得出的白榆无性系叶面积数学模型有较高的准确性 ,可在实际中应用。     

棉花优化栽培的群体光分布动态及光合生产的研究

本文应用二次正交旋转组合设计的方法探讨了密度、氮素、单株留果枝数及缩节安化控对棉花群体内光分布动态及光合生产的影响。结果表明，密度和氮素是影响群体内光强大小及干物重高低的主要因子，７月３１日左右是棉花群体内光强的最低阶段。叶面积系数和基部相对光强有极显著负相关（ｒ＝－０．９６１３），叶面积系数保持在３．５６～３．８２，可使棉株基部光强在蕾铃脱落临界光强之上。相对临界光强为１．９２％～３．８５％。此外，开花后干物质日增量与棉株叶片的净同化率呈极显著正相关（ｒ＝０．９１８７）。     

小麦后移栽棉的氮肥、密度效应及器官建成动态研究

采用二次均匀设计，研究氮肥和密度对小麦后移栽棉皮棉产量及其它主要经济性状的影响，建立了产量等性状的二次模型，通过对产量模型的分析，提出小麦后移栽棉适宜的施氮量为２１０～２３０ｋｇ／ｈｍ２、密度为４．７５万～４．９０万株／ｈｍ２．同时建立了不同器官（如株高、总果枝等）的建成动态模型，并提出小麦后移栽棉不同生育阶段器官建成动态的合理指标     

都市农业农户科技信息服务需求的影响因素分析——以天津设施种植业为例

以天津设施种植业为例,在实地调研和问卷调查的基础上,运用二项逻辑斯谛回归模型分析了都市农业农户对科技信息服务需求意愿的影响因素。研究结果表明:农户对科技信息服务的需求大,同时,农户特征因素(学历)、技术诱导因素(家庭收入、设施类型、长期种植人数)、信息来源因素(信息渠道多样性、参加培训讲座次数)、农户主观因素(废物处理技术关注度、优质化肥农药关注度)均对农户科技信息服务需求有显著影响。据此提出组建多元化的农业科技信息服务队伍,兼顾信息服务内容的实用性与前瞻性,创新多层、多维的信息服务模式等对策建议。     

A Predictive Method of Index on Power Consumption in a Resident Unit

In this paper, a series of data on power consumption and the numbers of household appliance in a resident unit of a district, were analyzed by regression technique. A curve of the index on power consumption of a resident unit in a district has been gained. This curve was tested by another series of data obtained at the same time.