鼎湖山旅游路径对针阔混交林个体数量和生物量空间分布格局的影响

以与旅游路径相邻的鼎湖山针阔混交林样地为研究对象,应用垂直路径和平行路径两种样带取样方法,探讨旅游路径影响下不同取样尺度群落个体数量和生物量的空间分布格局,以及不同优势种群空间分布格局对旅游路径干扰的响应.结果表明,群落生物量在各取样尺度上均未检测到显著变化(P>0.05),群落个体数在远离旅游路径方向各取样尺度上均呈显著的增加趋势(P<0.05).优势物种20 m取样尺度的空间分布格局反映了不同种群对旅游路径干扰的不同响应,其中荷木的生物量、豺皮樟的个体数和生物量在远离旅游路径方向上均呈显著增长趋势,其他物种的个体数和生物量变化不显著.     

Monitoring crayfish using a mark-recapture method: potentials,recommendations, and limitations

Crayfish are regarded as useful indicators of environmental quality and freshwater biodiversity. However, reliable methods for monitoring their populations are needed so that this potential can be fully utilised. We report and discuss methodological aspects of the white-clawed crayfish (Austropotamobius pallipes complex) survey conducted in Piedmont, Italy, with the use of mark-recapture. The results suggest that the method can serve as a convenient tool for estimating the size of crayfish populations and inferring their temporal trends. The two populations investigated appeared closed except for wintertime and July. Consequently, the Robust Design, which is regarded as the most reliable mark-recapture approach, can be easily applied. The minimum effective sampling plan for monitoring purposes should comprise one primary period per year, conducted in the summer–autumn season, and consisting of three capture sessions. If gaining insight into the ecology of the investigated species is the prime objective and sufficient resources are available, the optimal plan should include two primary periods (in spring and the summer–autumn season) of five capture sessions each. Capture sessions need to be separated by roughly 2-week intervals in order to avoid the strong, but short-term, negative effect of capturing crayfish on their recapture chances. As the model without heterogeneity in capture probabilities ensures better estimate precision we recommend that data collected for both sexes are analysed separately. Taking into consideration higher male catchabilities and sex ratio being invariably 1:1, it also seems beneficial to estimate only male numbers and double them to achieve total population sizes.     

Science, marketing and wishful thinking in quantitative proteomics

In a recent editorial (J. Proteome Res. 2007, 6, 1633) and elsewhere questions have been raised regarding the lack of attention paid to good analytical practice with respect to the reporting of quantitative results in proteomics. Using those comments as a starting point, several issues are discussed that relate to the challenges involved in achieving adequate sampling with MS-based methods in order to generate valid data for large-scale studies. The discussion touches on the relationships that connect sampling depth and the power to detect protein abundance change, conflict of interest, and strategies to overcome bureaucratic obstacles that impede the use of peer-to-peer technologies for transfer and storage of large data files generated in such experiments.     

Short sampling intervals reveal very rapid root turnover in a temperate grassland

Although root growth and mortality play critical regulatory roles in terrestrial ecosystems, little is known about the temporal scale of these dynamics. In temperate grasslands, root dynamics may be particularly rapid because of the high proportion of production allocated to very fine root biomass. In this study, we used minirhizotron tubes to estimate root growth and mortality in an upland grassland in Yellowstone National Park that was grazed by migratory herds of ungulates. Monthly rates of root growth and mortality were estimated from May to September 2005, by measuring the elongation (growth) and disappearance (mortality) of roots at 3-day intervals. Average daily growth (millimeters of root length) was approximately 5 times greater in May and June than in July, August, and September. Average daily mortality (millimeters of root length) did not differ among months. A comparison of the June-September rates of root growth and mortality derived from sampling at short (3-day) and long (1-month) time intervals indicated that the long sampling intervals underestimated both growth and mortality by approximately 60% relative to the short intervals. These results suggest that estimates of grassland root dynamics from minirhizotrons are influenced significantly by sampling interval length, and that rapid root turnover may play a more critical role in regulating energy and nutrient fluxes in temperate grasslands than has previously been recognized.     

Novel application of species richness estimators to predict the host range of parasites

Host range is a critical life history trait of parasites, influencing prevalence, virulence and ultimately determining their distributional extent. Current approaches to measure host range are sensitive to sampling effort, the number of known hosts increasing with more records. Here, we develop a novel application of results-based stopping rules to determine how many hosts should be sampled to yield stable estimates of the number of primary hosts within regions, then use species richness estimation to predict host ranges of parasites across their distributional ranges. We selected three mistletoe species (hemiparasitic plants in the Loranthaceae) to evaluate our approach: a strict host specialist (Amyema lucasii, dependent on a single host species), an intermediate species (Amyema quandang, dependent on hosts in one genus) and a generalist (Lysiana exocarpi, dependent on many genera across multiple families), comparing results from geographically-stratified surveys against known host lists derived from herbarium specimens. The results-based stopping rule (stop sampling bioregion once observed host richness exceeds 80% of the host richness predicted using the Abundance-based Coverage Estimator) worked well for most bioregions studied, being satisfied after three to six sampling plots (each representing 25 host trees) but was unreliable in those bioregions with high host richness or high proportions of rare hosts. Although generating stable predictions of host range with minimal variation among six estimators trialled, distribution-wide estimates fell well short of the number of hosts known from herbarium records. This mismatch, coupled with the discovery of nine previously unrecorded mistletoe-host combinations, further demonstrates the limited ecological relevance of simple host-parasite lists. By collecting estimates of host range of constrained completeness, our approach maximises sampling efficiency while generating comparable estimates of the number of primary hosts, with broad applicability to many host-parasite systems.     

A Monte Carlo method to account for sampling error in multi-species indicators

The usefulness of biodiversity indicators strongly increases if accompanied by measures of uncertainty. In the case of indicators that combine population indices of species, however, the inclusion of the uncertainty of the species indices has shown to be hard to realize, usually due to imperfections in monitoring programmes. Missing values and time series of different lengths preclude the use of analytical approaches, whereas bootstrapping across sites requires the raw abundance data on the site level, which may not always be available. Sometimes bootstrapping across species rather than sites is opted for, but this approach ignores the uncertainty attached to species indices. We developed a method to account for sampling error of species indices in the calculation of multi-species indicators based on Monte Carlo simulation of annual species indices. The construction of confidence intervals enables various trend assessments, like testing for linear or smooth trends, testing for changes between two time points, testing the significance of a suspected change-point and testing for differences between two multi-species indicators. Here, we compare our method with conventional methods and illustrate the benefits of our approach using Dutch breeding bird indicators.     

东灵山辽东栎林木本植物种间联结取样技术的研究

 在样地面积固定条件下,采用样方设计和样带设计,探讨了样方数目与面积之间的关系,以及样方数目与面积的变化对种间联结的影响。结果表明：正负关联比、平均物种出现率、多物种间X2值、物种对间X2值与显著率以及物种间联结系数的变化范围均可作为确定样方数目与面积的参数。在实际分析中应当综合考虑这些参数,进而选择最佳样方数目及面积进行种间联结分析。在样地总面积均为1 200 m2条件下,样带设计在各项指标上规律性比较明显,样方数为50,面积为25 m2最为合适;样方设计的各项参数稍差一些,需要进一步增加样方总面积才能得到更合适的样方数。分别按选定的最适样方数进行物种对联结性分析,对比分析结果显示样带设计对联结性和关联程度的检测效果好于样方设计,它的研究结果更与实际情况相符合。因此,在总样地面积有限的情况下,样带设计是进行种间联结分析的较好选择。     

Sequential Designs for Genetic Epidemiological Linkage or Association Studies A Review of the Literature

Objectives. The cost of a genetic linkage or association study is largely determined by the number of individuals to be recruited, phenotyped, and genotyped. The efficiency can be increased by using a sequential procedure that reduces time and cost on average. Two strategies for sequential designs in genetic epidemiological studies can be distinguished: One approach is to increase the sample size sequentially and to conduct multiple significance tests on accumulating data. If significance or futility can be assumed with a certain probability, the study is stopped. Otherwise, it is carried on to the next stage. The second approach is to conduct early linkage analyses on a coarse marker grid, and to increase marker density in later stages. Interim analyses are performed to select interesting genomic areas for follow up. The aim of this article is to give a review on sequential procedures in the context of genetic linkage and association studies. Methods. A systematic literature search was performed in the Medline and the Linkage Bibliography databases. Articles were defined as relevant if a sequential design was proposed or applied in genetic linkage or association studies. Results. The majority of proposed study designs is developed to meet the demands of specific studies and lacks a theoretical foundation. A second group of procedures is based on simulation results and principally restricted to the specific simulated situations. Finally, some theoretically founded procedures have been proposed that are discussed in detail. Conclusions. Although interesting and promising procedures have been suggested, they still lack realizations for practical purposes. In addition, further developments are required to adapt sequential strategies for optimal use in genetic epidemiological studies.     

改进的Iwao m-m模型的抽样方法

基于作者1984年提出的改进的Iwao -m模型,本文给出了相应的抽样公式。估计理论抽样数(Q)的公式为: 按照这一方程,可知dQ/dm依赖于α′、γ及m。从数学或生物学的角度来看,这都是更合理的,尤其当-m呈非线性时。     

鱼类早期资源调查中不同网具采集效率的研究

用网目为0.500和0.776mm的筛绢分别制成长度为1.5、2.0和2.5m的弶网、圆锥网和纺锤形网,采用网箱式、滤过式集苗桶和非滤过式集苗桶3种集苗器,于1998年5-6月在长江九江江段进行了采集仔鱼效果的比较研究。结果显示,弶网采集的数量最少,纺锤形网采集的数量最多。不同长度网具采集的数量没有显著差异,但长度为1.5m的圆锥网所采集仔鱼的规格明显小于长度为2.0和2.5m圆锥网所采集的。用网口面积分别为0.38m~2和0.20m~2的圆锥网组与不同类型集苗器进行比较,所采集仔鱼的数量和规格均没有差异。不同网目网具所采集仔鱼的数量没有显著差异,但网目为0.500mm圆锥网所采集仔鱼的平均规格显著小于网目为0.776mm圆锥网的。综合比较,以网目为0.500mm的纺锤形网的采样误差较小。