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851.
Coral reefs are highly dynamic and productive marine ecosystems, providing habitat and refuge for an enormous number of species
including fish, invertebrates and algae. With increased anthropogenic pressures and global climate change, many coral reefs
are rapidly declining. Currently, there is limited knowledge on condition and community assemblage composition of shallow
fringing coral reefs along the south-eastern coast of Queensland, Australia. With increased demand to determine existence
of coastal fringing reefs by National Regional Management groups, a rapid cost effective method to determine reef composition
and condition was required. The aim of this study was to determine the benthic structure and extent of two small coastal fringing
reefs (Hummock Hill Reef and Stringers Reef) along the Southern Great Barrier Reef. Reef substrate assessments were carried
out using a rapid assessment technique and a Point Intercept Method (PIM). The data were analysed and classified using a Geographic
Information System (GIS). Percent substrate cover was calculated using a visual basic image analysis program. The Point intercept
method showed higher accuracy over the rapid assessment technique (up to 15–40% difference) and was thus deemed a more suitable
classification tool for reefs with high structural complexity and heterogeneity. This study focused on piloting a rapid, cost
effective Point Intercept Technique using random point count methodology to document coral benthic habitat and extent over
a commonly used rapid assessment method as a tool for reef coastal management and conservation. The two techniques were compared
and substrate classification success, limitations and errors were discussed. 相似文献
852.
Extrapair paternity in birds has been the focus of an increasing number of studies over the last decades. Nevertheless, there is little knowledge about extrapair copulation (EPC) behavior. In this study, we investigate whether female bluethroats (Luscinia s. svecica) with no extrapair offspring (EPO) in their broods really have been sexually monogamous or if they have copulated with extrapair males. We used an experimental approach to prevent transfer of sperm from the social male during copulation by fitting a rubber tube around the cloaca of randomly chosen males. If the females mated to these males do not participate in EPCs, they will produce infertile eggs, whereas females that copulate with extrapair males will only produce EPO. We found that 87% (n=15) of the experimental pairs compared to only 36% (n=51) of unmanipulated pairs produced EPO. Our result therefore suggests that females having no EPO may still have copulated with extrapair males and that promiscuity may be an obligate sexual strategy among bluethroat females.Communicated by S. Pruett-Jones 相似文献
853.
群落中物种多度格局的研究综述 总被引:4,自引:0,他引:4
张金屯 《生态与农村环境学报》1997,(4)
物种多度格局是群落结构的重要内容,但在目前的生态学研究中对其重视不够;多度格局研究早在30年代就开始,在过去的数十年中得到了重要发展;现已建立了多种多度格局模型,它们各有所长;多度格局与物种多样性指数结合,对群落结构研究更具意义;在多度格局研究中也有一些问题值得讨论。 相似文献
854.
讨论了自然遗产的概念,通过对自然遗产概念的讨论进一步分析了自然遗产的特征并对自然遗产进行了分类,最后对自然遗产与文化遗产、自然遗产与地质遗迹进行了辨析 相似文献
855.
Markus Metz Georg M. Klump Thomas W. P. Friedl 《Behavioral ecology and sociobiology》2007,61(9):1369-1381
The red bishop (Euplectes orix) is a highly polygynous and colonial weaverbird. Males construct several nests within their territories to which they try
to attract females, and females are solely responsible for incubation and raising offspring. In this paper, we describe the
characteristics of the red bishop’s mating system as a biological market and investigate the role of nests built by males
as a traded commodity in a mating market. As timing of breeding in red bishops in arid and semi-arid zones depends on rainfall
patterns which are often unpredictable, there are temporal changes in demand for and supply of nests within a breeding season,
with breeding activities of males and females being highly synchronised. We found that males increased their nest-building
speed with increased female breeding activity independently of rainfall, indicating that supply follows demand in this mating
market. The supply of nests was always larger than the demand for nests. Construction costs for nests increased with demand
for nests as indicated by shorter nest-building duration and shorter building delays between two consecutively built nests
at times of high breeding activity. Males as a trading class are chosen according to the age of their nests offered, with
young nests having a higher probability of being accepted by females. Furthermore, female choosiness with regard to nest age
decreased when their own market value decreased, as predicted by biological market theory. The temporal changes of breeding
activity together with the female preference for young and fresh nests require that males quickly adjust nest-building activity
to varying female demand for new nests. However, males with a better adjustment of building speed to female breeding activity
did not gain higher mating success. 相似文献
856.
The vegetative cover in semi-arid lands typically occurs as patches of individual species more or less separated from one another by bare ground. We have adapted two methods to quantify the spatial pattern of such cover from measurements across patches on transects.Transects were laid in several directions across digital maps of the land surface or across the land itself, and the distances between successive patch boundaries were measured. The distances were ranked in order, and their cumulative distributions were computed and modeled with gamma functions. The parameters of the model provided estimates of the mean distance across patches. The means for different directions were further tested for anisotropy. Transitions between classes on the transects estimate the probabilities with which the different species occur next to others (and to bare ground) and so describe the arrangement of the patches occupied by the different species.The methods were tested with data from mosaic patterns at three semi-arid sites dominated by the tussock grass Stipa tenacissima. The differences in the estimated mean boundary spacings from site to site accorded with prior qualitative assessment, as did the estimated anisotropy. The transition matrices and the estimated proportions of cover showed the dominance of the bare soil with which all the individual species are intimately associated. The transitions also suggest the presence of both positive and negative relations among the main species. Those between Stipa tenacissima and Brachypodium retusum seem to be facilitative, as do those between this grass and the shrub Anthyllis cytisoides. In contrast, Globularia alypum seems to inhibit the other species.We also estimated transition probabilities geostatistically by summing the indicator variograms of the individual species. Standard variogram models were then fitted to describe the ordered series of values, and these again produced results that accorded with visual impressions. 相似文献
857.
Metapopulation models assume that inter-patch dispersal dominantly depends on distance between patches and the dispersal capability of organisms in question. We used a spatially explicit, individual-based model to investigate the potential effect of patch constellation on the exchange of individuals between patches. We simulated migration of individuals from a start- into a target-patch with both patches having the same size and shape. Simulation experiments were carried out for four patch constellations and two different movement patterns. Our results demonstrate a substantial effect of patch constellation on the exchange of individuals. They also show that the magnitude and even the direction of this effect crucially depends on their movement pattern. We conclude that particularly for highly correlated movement patterns patch shape and constellation can not readily be ignored when modelling inter-patch dispersal between habitat-islands. 相似文献
858.
中国东部南北样带中南段典型植被类型NDVI变化分析 总被引:6,自引:0,他引:6
以IGBP第15条国际标准样带——中国东部南北样带中南段的植被为主要研究对象,对该区域应用NDVI(normalized difference vegetation index)数据进行植被类型划分,共划分为三大类35小类.在此基础上,选择6种不同气候区域典型的森林植被类型,对其NDVI变化进行分析,从而得出:NDVI随着纬度的降低变化逐渐减小;通过研究经向年内:NDVI变化,发现4月份研究区域南北:NDVI指数变化最明显;分析NDVI均值变化可知,从暖温带到北亚热带植被指数NDVI形成明显的阶跃,从而判定植被指数NDVI对短期气候变化具有明显的指示性,并发现通过植被指数NDVI的季节变化曲线,可以较为准确地判定森林、草原、农作物等大类型,图4表1参15。 相似文献
859.
多位点酶电泳在黄芪根瘤菌分类中的应用 总被引:2,自引:0,他引:2
报导了分析根瘤菌各种多位点酶的电泳缓冲系统和染色方法,并对黄芪根瘤菌进行了分类研究,结果表明:采用多位点酶电泳图谱进行聚类可得到与数值分类基本一致的结果,证实这是一种行之有效、简便快速的分类方法. 相似文献
860.
J. Ojeda E. Sanchez A. Fernandez-Palacios J. M. Moreira 《Journal of Coastal Conservation》1995,1(2):109-118
This paper deals with the application of satellite images to characterize some aspects of the circulation dynamics of the
Tinto-Odiel estuary using turbidity patterns as ‘natural tracers’. 15 images (Landsat TM and Spot HRV) were processed to provide
synoptic, instantaneous views of the circulation patterns under different environmental conditions. In addition, a comparison
was made between results of oceanographic field work, using biplanes and fluorescent tracers, and satellite image turbidity
patterns used as ‘ground truth’ data for specific hydroclimatic situations. This approach allowed (1) the identification and
mapping of dynamic processes of interest during a theoretical tidal cycle, (2) the elaboration of additional information on
the ‘flow schemes’ at the mouth of the estuary with improved spatial and temporal resolution, and (3) the supply of basic
data to improve the knowledge of exchange processes between estuarine and coastal waters. The results of this study are considered
to be useful for the management of the estuarine system. 相似文献