The species-area relation II. A second model for continuous sampling

A second mathematical model describing the species-area relation was proposed for continuous expanding of sample area. This model is expressed as S=λ ln(1+x/E) where S is the number of species occurring in an area x, and λ and E are the constants termed specific diversity and elemental area respectively. As a result of testing the validity of the model for several sets of data, it was shown that the above equation would provide an adequate fit to a group of species belonging to a single synusia which exists in an open habitat. The ecological implications of parameters involved were discussed and the characteristic area presented previously (Kobayashi , 1974) was defined in terms of E. The relation between results obtained by discrete sampling and continuous sampling was examined and the possibility of converting one to another was suggested.     

Multi-stage sampling for population estimation

Summary Multi-stage sampling is a convenient technique suited to the desnity estimation of biological populations living in habitats with complicated structures. This paper describes a general method of its application to population estimation in which the preliminary information on the spatial distribution pattern of the population under study can be incorporated as the parameters of the mean crowding-mean relationship. The formulae that are necessary to perform sequential or double sampling plans for its efficient application are derived. The procedure of application of the method is explained with a numerical example. This study was supported by science research fund from the Ministry of Education.     

Development of an optimal sampling protocol for millipedes (Diplopoda)

This study determined a millipede sampling protocol that was efficient, replicable, and thorough, by testing commonly used methods (pitfall trapping, hand collection, and leaf litter collection with Berlese extraction) at sites where the fauna had been intensively sampled, so that the results of different sampling protocols (‘experimental sampling’) could be compared to the previously known fauna of each site (determined by ‘baseline sampling’). Two methods of collecting leaf litter were compared. One method allowed the collector to choose the locations from which to sample leaf litter, while the second method used randomly generated locations. Experimental sampling took place at both an upland site (Swallow Cliff Woods, Cook Co, IL) and a wetland site (Cedarburg Bog, Ozaukee Co, WI) where reliable baseline data was available. The optimal protocol for millipedes was found to consist of a combination of the hand collection and the a priori litter methods. In studies where there are constraints on time or resources devoted to sampling or processing, this protocol can be reduced to the single most effective method, hand collection. Overall, the a priori litter collection method was more effective than the random litter collection method.     

农业环境中土壤取样误差研究

对自然条件下8种土壤类型、39个取样地块的25个土壤理化参数的取样误差进行了综合研究。结果表明,不同地块间,按累计取样误差大小排序为:池塘>地块边缘>自留地>林地>商品菜地>旱地>水田>滩地。在所有地块测定项目中,取样误差最大的是Cl^-,平均高达70%以上,其次是土壤有效磷,除滩地外取样误差基本上都超过30%;有效钾和全硫的取样误差也多在20%以上;取样误差最小的理化参数与成土母质有关,其中包括各种重金属和全量P、K、Mg以及pH和砂粒等,除极个别外,误差都在10%以下;2种粒度的土壤水分、碳酸钙、粉砂、粘粒、有机碳、全量N、Na、Ca、B和As等11项理化参数的取样误差居中,误差变动于10%～20%之间。聚类分析可以将不同测定项目大致分为3类,客观反映了人类活动对土壤理化参数分布均匀性的影响。     

Shallow pore water sampling in reef sediments

Several new techniques have been developed to allow the geochemical characterization of shallow pore waters in reefs. First, a new method was developed for using non-metallic well-points to sample pore waters from shallow depths (<1 m) in coral reefs with unconsolidated substrates. These PVC well-points can be made faster and at less expense than well-points made of stainless steel. They also eliminate metal contamination and are free from the problems of corrosion in sea water. Additional improvements in sampling techniques maximize the spatial resolution of geochemical gradients and address the problems of atmospheric contamination associated with the sampling of dissolved gases. Data taken from Checker Reef, Oahu, Hawaii, illustrate the application of these methods. Accepted: 1 December 1999     

Affinity analysis: effects of sampling

I explored the effects of sampling on three measures of regional diversity: diversity (the number of species), diversity (mean similarity among sites), and diversity (mosaic diversity and structure around mean similarity). Two sampling effects were modelled by computer simulation, number of sites sampled and intensity of sampling within sites, using plant community data from Michigan, North Carolina, and Costa Rica. Estimates of the number of species were sensitive to both sampling effects. Estimates of mean similarity were unaffected by the number of sites sampled but were sensitive to the intensity of sampling. Estimates of mosaic diversity were relatively unaffected by the number of sites sampled, if the number was above 30 sites and outlier sites were removed, and were not sensitive to the intensity of sampling. I offer mean similarity as a multi-gradient complement to diversity measured as the turnover of species along a single gradient.     

General ranked set sampling with cost considerations

Nahhas, Wolfe, and Chen (2002, Biometrics58, 964-971) considered optimal set size for ranked set sampling (RSS) with fixed operational costs. This framework can be very useful in practice to determine whether RSS is beneficial and to obtain the optimal set size that minimizes the variance of the population estimator for a fixed total cost. In this article, we propose a scheme of general RSS in which more than one observation can be taken from each ranked set. This is shown to be more cost-effective in some cases when the cost of ranking is not so small. We demonstrate using the example in Nahhas, Wolfe, and Chen (2002, Biometrics58, 964-971), by taking two or more observations from one set even with the optimal set size from the RSS design can be more beneficial.     

土壤养分循环实地采样调查方法

讨论了一种在区域尺度上研究生态系统中土壤养分循环的样区采样及调查方法.即在满足土壤养分循环研究所要求的代表性、重现性、随机性及时间性等原则的基础上,利用地形图及航空照片等资料,在区域中选定合适面积和数量的样区后,在各样区内按统一标准采集土壤和植物样品.考虑区域土壤养分循环受自然环境条件和社会经济条件等因素的制约,野外采样过程中有必要对采样单元的实地情况进行调查记载,并就样区内所有农户的基本状况、种植业结构及肥料投入等有关土壤养分循环的影响因子进行农户调查.对我国亚热带农业生态系统中土壤养分循环进行了案例研究,探讨了该采样调查方法在土壤养分循环研究中的应用.     

Why sampling scheme matters: the effect of sampling scheme on landscape genetic results

There has been a recent trend in genetic studies of wild populations where researchers have changed their sampling schemes from sampling pre-defined populations to sampling individuals uniformly across landscapes. This reflects the fact that many species under study are continuously distributed rather than clumped into obvious “populations”. Once individual samples are collected, many landscape genetic studies use clustering algorithms and multilocus genetic data to group samples into subpopulations. After clusters are derived, landscape features that may be acting as barriers are examined and described. In theory, if populations were evenly sampled, this course of action should reliably identify population structure. However, genetic gradients and irregularly collected samples may impact the composition and location of clusters. We built genetic models where individual genotypes were either randomly distributed across a landscape or contained gradients created by neighbor mating for multiple generations. We investigated the influence of six different sampling protocols on population clustering using program STRUCTURE, the most commonly used model-based clustering method for multilocus genotype data. For models where individuals (and their alleles) were randomly distributed across a landscape, STRUCTURE correctly predicted that only one population was being sampled. However, when gradients created by neighbor mating existed, STRUCTURE detected multiple, but different numbers of clusters, depending on sampling protocols. We recommend testing for fine scale autocorrelation patterns prior to sample clustering, as the scale of the autocorrelation appears to influence the results. Further, we recommend that researchers pay attention to the impacts that sampling may have on subsequent population and landscape genetic results. The U.S. Government's right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.     

根际微域研究中土样采集方法的研究进展

综述了６０年代以来植物根际微域研究中土壤样品的采集方法。认为根际土样采集的发愤趋势是从田间的各采集到室内模拟实验的精细划分，再把模拟装置运用到田间，最终达到指导生产的目的。同时，随着根际概念的拓（生态界面Ｅｃｏ－ｂｏｕｎｄａｒｙ ｌａｙｅｒ），根际土样的采集朝着保持原位和更精细的方向发展。     

Distribution-abundance relationship for passerines breeding in Tunisian oases: test of the sampling hypothesis

The positive relationship between local abundance and distribution of species is a widely recognized pattern in community ecology. However, it has been suggested that this relationship can simply be an artefact of sampling because locally rare species are less detectable then locally abundant ones, and hence their distribution can easily be underestimated. Here, we use count data to investigate the relationship between distribution and abundance of passerines breeding in a sample of oases from southern Tunisia, and we provide a test of the sampling artefact hypothesis. In particular, we checked for a difference in detection probability between localized and widespread species, and we tested if increasing the sampling effort affects the significance of the relationship. A significant positive relationship between the average local abundance of passerine species and the proportion of occupied oases was found. The use of a capture-recapture approach allowed us to estimate and to compare the detection probabilities of localized and widespread species subsets. We found that localized species were locally less detectable than widespread species, which is consistent with the main assumption of the sampling artefact hypothesis. However, increasing the detection probability of species by conducting more counts did not affect the significance of the relationship, which did not give support to the sampling artefact hypothesis. Our work implies that sampling contributed to the distribution-abundance relationship we found, but that it is unlikely that such a relationship could entirely be explained by an artefact of sampling. It also underlines the insight that can be gained by using probabilistic approaches of estimating species number and detection probability when attempting to disentangle sampling from ecological effects in community ecology studies.     

Spatial autocorrelation and sampling design in plant ecology

Using spatial analysis methods such as spatial autocorrelation coefficients (Moran's I and Geary's c) and kriging, we compare the capacity of different sampling designs and sample sizes to detect the spatial structure of a sugar-maple (Acer saccharum L.) tree density data set gathered from a secondary growth forest of southwestern Québec. Three different types of subsampling designs (random, systematic and systematic-cluster) with small sample sizes (50 and 64 points), obtained from this larger data set (200 points), are evaluated. The sensitivity of the spatial methods in the detection and the reconstruction of spatial patterns following the application of the various subsampling designs is discussed. We find that the type of sampling design plays an important role in the capacity of autocorrelation coefficients to detect significant spatial autocorrelation, and in the ability to accurately reconstruct spatial patterns by kriging. Sampling designs that contain varying sampling steps, like random and systematic-cluster designs, seem more capable of detecting spatial structures than a systematic design.Abbreviations UPGMA = Unweighted Pair-Group Method using Arithmetic Averages