长期定位施肥对棕壤无机磷形态及其有效性的影响Ⅰ．对各形态无机磷含量比例

对定位施肥的棕壤土壤无机磷形态分级的研究结果表明：长期无磷素投入的N、CK区，Ca10-P含量下降了约25％，而O－P下降了11.6%-30%，施肥后，土壤中无机磷的增量主要是形成Fe－P和Al-P,其次对有机肥中的磷是形成Ca8－P和Ca2－P。连续14年的高量有机肥和磷肥配施，使土壤各形态无机磷占全磷比例的先后顺序发生了很大的变化，其比例由大到小依次为：Fe-P(22.76%)、O-P（14.6%)、Al-P(12.49%)、Ca10-P(9.13%)、Ca8-P(7.99%)、Ca2-P(6.58%),而原始土壤中则是：O－P（24.21%),Ca10-P、Fe-P(17.87%,16.68%),Al-P、Ca8-P(1.71%,1.57%),Ca2-P(0.23%)。     

基于3S的森林植被面积空间抽样方法

以辽宁省为例,应用中分辨率成像光谱仪影像(MODIS)数据进行森林信息提取,并选取森林面积为研究对象,采用网格单元作为抽样单元,应用随机、系统、分层的抽样方法对辽宁省森林面积进行抽样估算,在获得最优抽样方法的基础上进行第2阶段抽样,设计不同样本容量水平下的森林面积空间抽样方法试验。结果表明:以县森林面积覆盖百分比为分层标志的分层抽样方法抽样效率最高,在第2阶段抽样估算的8种样本容量水平下,当样本容量为8时,抽样精度达到95%,并且所需样本数量最少,达到了森林面积抽样精度要求。应用此方法能够减少森林资源调查成本和工作量,可以结合遥感、地理信息系统和全球定位系统技术(3S技术),进行大区域范围森林面积的监测。     

百日草白粉病的空间分布和抽样技术研究

[目的]对百日草白粉病的空间分布型及抽样技术进行研究,为指导百日草白粉病的化学防治工作提供参考。[方法]采用空间分布型指标确定病害的空间分布型;利用Iwao公式确定理论抽样数,制作百日草白粉病的序贯抽样检索表。[结果]百日草白粉病的空间分布型在发病初期(平均病级数小于2.0)为聚集分布;随着病害发生程度增加,病害的聚集程度逐渐变小,当植株的平均病级数为2.5~4.0时,病害的分布型会转变为随机分布;当植株的平均病级数大于4.5时,病害的分布型会转变为均匀分布。计算出不同发病程度及不同精确度要求下的理论抽样数,得到序贯抽样检索表。[结论]该研究给出的理论抽样数及序贯抽样检索表是科学实用的抽样方法。     

玉米田间试验取样方法的研究

在玉米田间试验中,用平均穗重取样和随机果穗取样测得的结果与小区单收单打的结果作比较,结果表明用平均穗重取样测得的结果与小区单收单打所得结果基本相符,在玉米田间试验中用平均穗重取样法优于果穗随机取样法,能更好地反映客观实际。     

Integrating models of relative abundance of species with the dry-weight-rank method for the botanical analysis of forest understorey vegetation

The objective of this work was to determine the applicability of the dry‐weight‐rank (DWR) method for evaluating the botanical composition of forest understorey vegetation. An analysis of plant species abundance was carried out, and instead of ranking the three most abundant species, as is commonly used, up to twelve ranks were scored. Concurrently, four models of relative abundance distribution (RAD) of species were compared for their ability to explain the abundance of species in the study area. The Power‐fraction model resulted in the best goodness‐of‐fit and it was subsequently used to produce the coefficients for the DWR method. Lin's concordance correlation coefficient, the adjusted coefficient of determination, the residual standard deviation and Spearman's rank‐order correlation coefficient indicated a good performance of the DWR method. Biomass data and the Shannon index for diversity were also considered. Further analyses showed that there was a trade‐off between the number of ranks scored and the accuracy of the botanical composition produced by the DWR method. It is concluded that, so long as the RAD model that explains the distribution of plant species is known, the DWR method can be applied to forest understorey vegetation.     

Optimisation of sample size for the detection of latent infection byRalstonia solanacearum in potato seed tubers in the highlands of Peru

Summary A sampling strategy was evaluated in the Andean highlands of Peru to optimise the detection ofRalstonia solanacearum in seed tubers harvested from symptomless crops. A sensitive and specific serological method developed at CIP was used to detect the pathogen in latently infected tubers. Optimum sample size was evaluated for symptomless crops after analysing various numbers of composite samples and using a binomial distribution model to calculate the detection probabilities.R. solanacearum was detected in all lots from fields with visible symptoms, so validating the detection technique. About half of the seed lots from apparently healthy fields at altitudes of up to 3,100 m were found positive for the pathogen.R. solanacearum was detected with 99% probability in samples of 350 tubers from seed lots from symptomless crops. This number of seed tubers could feasibly be processed in a seed-health test without incurring too high a cost for labour and materials.     

Sampling and development of economic injury levels for Anthonomus rubi Herbst adults

Field studies were conducted in northwestern Turkey from 1998–2000 to examine population dynamics of adult strawberry blossom weevils (Anthonomus rubi Herbst), and to establish economic injury levels based on the relationship between densities of overwintered adults and yield losses. Adult weevils were sampled weekly in untreated and insecticide-treated plots using a sweep net. Sweep net catches showed that the abundance of A. rubi adults had two peaks; the first between late-April and early-May, and the second between late-June and mid-July. Linear regression revealed a strong relationship between overwintered and new-generation adult densities. The overwintered-generation adults had generally higher mean population densities than the new-generation. A significant linear decrease was observed in strawberry yields as densities of overwintered-generation adults increased. Percentage yield losses varied between 1.64% and 13.42% among sites. Estimated economic injury levels ranged from 1.00 to 4.00 adults per sweep depending on the management scenario, control cost, control efficacy, and crop value.     

The life-cycle of the compost worm Eisenia fetida (Oligochaeta)

To determine the full potential of the compost worm Eisenia fetida as waste processor and as source of protein, the life-cycle of this species had to be studied thoroughly. The development, growth and reproduction of Eisenia fetida were studied on cattle manure under favourable conditions of moisture, temperature and nutrition. Data were gathered over a period of 600 days. Apart from the life-cycle this study also indicated that this species can be reproductively active for more than 500 days. This is significantly longer than had previously been believed. Each cocoon produced a mean of 2,7 hatchlings after a mean incubation period of 23 days. These worms attained sexual maturity after 40 to 60 days and produced their first cocoons within four days after mating took place.     

基于高分辨率影像的城市和平原绿化调查技术研究

基于高分辨率影像,采用成数抽样原理的调查方法,对城市和平原绿化调查与监测技术进行研究.通过解决界线确定、样点布设、遥感判读、实地核查、精度分析等技术难点,形成一整套完善的调查技术流程,并对直接影响调查工作量的样点数量进行探讨.经实际应用,结果显示：研究区调查成果翔实,成果数据有很高的精度保证,采用该技术开展城市和平原绿化调查,能够有效解决城市和平原区调查制高点问题、数据综合分析问题及调查成果可靠性问题.     

Determining sample size for assessing species composition in grassland 1

Species composition is measured in grasslands for a variety of reasons. Commonly, observations are made using the wheel‐point apparatus. However, the problem of determining optimum sample size has not yet been satisfactorily resolved. In this study the wheel‐point apparatus was used to record 2 000 observations in each of a range of sample sites. A random number generator was used to select 30 sets of samples of size N (number of point‐observations) from each sample site. A measure of similarity for each sample with every other in a set was calculated to establish the variation that may be expected for that sample size. The Richards function was used to determine the sample size (number of point‐observations) required to retrieve a minimum level of precision. It is proposed that 100 point‐observations are sufficient for coarse management scale investigations, 200 for monitoring programmes and 300 for detailed scientific studies.