北京市珍珠泉乡不同昆虫采集方法采集效果对比分析

为了探究科研调查中不同昆虫采集方法的采集效率差异,在北京珍珠泉乡不同的生境类型中,采用样线法、马氏网法、灯诱法、陷阱法(糖醋液)4种采集方法进行昆虫采集,按生境类型对不同采集方法采集的昆虫进行统计分析.在实验中共采集昆虫3996头,隶属12目87科,其中在昆虫种类数量上,鳞翅目最多,其次是半翅目和鞘翅目;在数量上,半翅...     

Geographic,seasonal, and diurnal surface behavior of harbor porpoises

During ship surveys harbor porpoises are only visible when breaking the sea surface to breathe, while during aerial surveys they may be seen down to 2 m below the surface. The fractions of time spent at these two depths can be used for correcting visual surveys to actual population estimates, which are essential information on the status and management of the species. Thirty‐five free‐ranging harbor porpoises (Phocoena phocoena) were tracked in the region between the Baltic and the North Sea for 25–349 d using Argos satellite transmitters. No differences were found in surface behavior between geographical areas or the size of the animals. Slight differences were found between the two sexes and time of day. Surface time peaked in April, where 6% was spent with the transmitter above surface and 61.5% between 0 and 2 m depth, while the minimum values occurred in February (3.4% and 42.5%, respectively). The analyses reveal that individual variation among porpoises is the most important factor in explaining variation in surface rates. However, the large number of animals documented in the present study covering a wide range of age and sex groups justifies the use of the seasonal average surface times for correcting abundance surveys.     

基于样带—地理探测器的陆桥通道沿线建制市建成区绿地率区域差异影响机理研究

在中国新型城镇化转型发展背景下，科学认识城市绿地建设水平的影响机理是提升人居环境质量、实现城市绿色发展的重要前提。选取陆桥通道样带为研究区域，采用地理探测器方法，探究 1996—2016 年沿线样带 139 个建制市建成区绿地率区域差异的影响机理。研究表明： 1）沿线样带市域建成区绿地率逐年提升，但存在明显时空分异，呈东西部两头高、中部低的“U”型格局； 2）地理探测显示样带市域建成区绿地率差异是自然、经济和政策等因素非线性或双因子作用的结果，年均温为核心主导因子，园林城市政策、海拔高程是次要解释力； 3）自然地理本底是奠定差异的重要基础，政策引领是关键，经济水平是直接推动因素，产业结构、土地供给和基础设施为外部主导动力。研究定量化呈现了自然因素对城市绿地建设水平区域差异的大尺度、长期性影响；探测“自然—经济—政策”多维因素的综合作用，更精准地对城市绿地建设分类施治，是典型区域和典型方法在学科领域的一次尝试。     

Review of Some Important Techniques in Wildlife Sampling and Sampling Errors

This paper reviews some of the important methods for estimating animal numbers or densities based on (i) direct counts of population units as used in quadrat, strip, line-transect and line-intercept sampling and (ii) indirect counts and indices, such as capture-mark recapture, change-in-ratio, catch-effort methods and indices based on track counts, call, roadside and pellet-group counts, etc.     

Fluctuations in the abundance of butterflies, 1976–82

Abstract. 1. A scheme for monitoring the abundance of butterflies at about eighty sites in Britain is described.
2. Indices of abundance are presented for twenty-nine species for the years 1976–82.
3. There are marked differences between species in the scale of annual fluctuations.
4. Some species show correlations between successive index values; for example the summer generation index of Pieris brassicae is highly correlated with the spring generation index.
5. The annual changes in the index values of many species are highly Correlated. The index values themselves also show positive correlations, but these are less strong.
6. The drought of 1976 is believed to have severely depressed populations of many species in 1977.
7. The data do not indicate any general fall in butterfly numbers over the period at the sites in the scheme.
8. The sites are not representative of the countryside as a whole, but, for a number of species, it is considered that the index values reflect wider trends.     

A new approach for detecting visibility bias for the fixed-width transect method

Four road counts and four series of daily road counts of 28.4% sampling intensity were carried out at Wildlife Ranching and Research Ltd (WRR), Athi River, Kenya, between December 1966 and July 1987 to test the applicability of the method to the WRR environment. The results, however, exhibited high variation. Difficulties were encountered when applying the Anderson & Pospahala (1970) method to detect the existence of visibility bias in the distribution of Thomson's gazelle. An alternative approach, based on the regression of group size on the right angle sighting distance was applied to detect the existence of visibility bias.     

The breeding migration of Littorina arcana Hannaford Ellis, 1978 (Prosobranchia: Littorinidae)

Two species of rough winkle, the oviparous Littorina arcana and the ovoviviparous L. saxatilis are very similar in their outward appearance and are commonly syntopic. This has led some researchers to regard these species as conspecific and to suggest that reproductive modality is not a fixed characteristic. However, the syntopy of these species is much more complex than has been supposed and data presented here show how the seasonally reproducing L. arcana migrates downshore during its breeding period, into areas where L. saxatilis is comparatively sparse. This results in a separation of the breeding populations of the two species and consequently a spatial separation of their juveniles, at least in their early stages. Selection pressures on the breeding animals and young juveniles will therefore differ.     

Total Counts Versus Line Transects for Estimating Abundance of Small Gopher Tortoise Populations

Abstract: Status and trends of gopher tortoise (Gopherus polyphemus) populations are a critical information need for natural resource managers, researchers, and policy makers. Many tortoise populations are small and isolated, which can present challenges for deriving population estimates. Our objective was to compare abundance and density estimates for a small tortoise population derived using a total burrow count versus estimates obtained with line transect distance sampling (LTDS) using repeated surveys. We also compared results of the 2 survey methods using standard burrow-to-tortoise correction factors versus assessing occupancy of all burrows with a camera scope. In addition, we compared LTDS data obtained using a compass and measuring tape to define transects to those obtained using a Global Positioning System (GPS) and Personal Data Assistant (PDA) field computer to navigate transects. Line transect distance sampling with repeated surveys (both with a measuring tape and compass and with a GPS—PDA) yielded sufficient observations of tortoises to calculate population estimates. From 18% to 31% of burrows were occupied by tortoises as determined with the burrow camera. We found 25 burrows during the LTDS survey that we did not find in the total count survey, which demonstrated that the assumption of 100% detection for the total count was not met; hence, density or abundance measurements derived with this method were underestimates. We recommend using GPS—PDA technology, scoping all burrows detected, and using LTDS with repeated surveys to estimate abundance and density for small gopher tortoise populations.     

Landscape monitoring of semi-arid rangelands in the Kenyan Rift Valley

A sampling system was devised and used from 1992 to 1996 in annual grassland and open woodland of the south-west Kenyan Rift Valley. The monitoring was designed to detect vegetation changes consequent on the attempted removal of the tsetse vectors of trypanosomiasis in cattle during a simultaneous trapping programme. The sampled sites covered most vegetation-landscape types, and have led to a better understanding of processes within some. Although fluctuations in pastoralist use and occupancy have been observed, no change in vegetation can be attributed to increased grazing or browsing. Although there is high climatic variability some vegetation types seemed stable over the period studied, and some trends appear to be predictable.