Spatial ecology of golden jackal in farmland in the Ethiopian Highlands

The spatial ecology of golden jackal Canis aureus was studied on farmland adjacent to the Bale Mountains National Park in southern Ethiopia during 1998–2000. Three adult and four subadult jackals were captured in leg‐hold traps and radiotagged. The range size of the adult jackals varied from 7.9 to 48.2 km² and the subadults from 24.2 to 64.8 km² . These ranges are the largest recorded for this species. Range overlap of the tagged jackals averaged 54%, which, in conjunction with observations of associations between individuals, suggested that all the tagged jackals belonged to one social group. Tagged jackals were observed alone on 87% of occasions despite the extensive overlap in individual ranges. Pairs consisting of a male and female were the most commonly observed group and larger groups were seen on only five occasions. Jackals in this population appeared less gregarious than observed elsewhere. The jackals used all the habitats available to them, particularly at night when they foraged in Artemesia and Hypericum bush and farmland. During the day they were more frequently found in Hagenia and Juniper woodland and their diurnal resting sites were characterized by thick cover. This is the first detailed study of golden jackals in a human‐modified landscape in Africa and further demonstrates the flexibility in behaviour and ecology exhibited by this species throughout its range.     

Species–energy relationships and habitat complexity in bird communities

Species–energy theory is a commonly invoked theory predicting a positive relationship between species richness and available energy. The More Individuals Hypothesis (MIH) attempts to explain this pattern, and assumes that areas with greater food resources support more individuals, and that communities with more individuals include more species. Using a large dataset for North American birds, I tested these predictions of the MIH, and also examined the effect of habitat complexity on community structure. I found qualitative support for the relationships predicted by the MIH, however, the MIH alone was inadequate for fully explaining richness patterns. Communities in more productive sites had more individuals, but they also had more even relative abundance distributions such that a given number of individuals yielded a greater number of species. Richness and evenness were also higher in structurally complex forests compared to structurally more simple grasslands when controlling for available energy.     

Use of Restored Small Wetlands by Breeding Waterfowl in Prince Edward Island, Canada

Abstract Since 1990 under the Eastern Habitat Joint Venture over 100 small wetlands have been restored in Prince Edward Island, Canada. Wetlands were restored by means of dredging accumulated sediment from erosion to emulate pre‐disturbance conditions (i.e., open water and extended hydroperiod). In 1998 and 1999 we compared waterfowl pair and brood use on 22 restored and 24 reference wetlands. More pairs and broods of Ring‐necked Ducks, Gadwall, Green‐winged Teal, and American Black Ducks used restored versus reference wetlands. In restored wetlands waterfowl pair density and species richness were positively correlated with wetland/cattail area, percent cattail cover, and close proximity to freshwater rivers. In addition, a waterfowl reproductive index was positively correlated with percent cattail cover. Green‐winged Teal pair occurrence in restored wetlands was positively correlated with greater amounts of open water and water depths. American Black Duck pairs occurred on most (86%) restored wetlands. Restored small wetlands likely served as stopover points for American Black Duck broods during overland or stream movements, whereas they likely served as a final brood‐rearing destination for Green‐winged Teal broods. We suggest that wetland restoration is a good management tool for increasing populations of Green‐winged Teal and American Black Ducks in Prince Edward Island.     

Influences of habitat features and human disturbance on use of breeding sites by a declining population of southern fur seals (Arctocephalus australis)

Southern fur seals Arctocephalus australis in Peru have declined gradually over the past decade, and declined dramatically (72%) as a result of low food availability during the severe El Niño in 1997–98. In 1999, seals abandoned some historically important breeding sites. This is particularly alarming because new sites were not colonized. Our objective was to examine how habitat features and human disturbance influenced whether sites were currently used, abandoned or apparently not used in the past by fur seals for breeding. Data were collected on 14 variables at 70 potential breeding sites at three guano reserves in Peru. Discriminant analysis revealed significant multivariate differences among sites currently used for breeding, abandoned sites and unused sites ( F =5.97, P <0.00001), and the model classified 74% of sites correctly. Currently used sites were less likely to have human disturbance and more likely to have offshore islands, stacked rocks, tide pools and abundant shade. Separate discriminant analyses for each reserve produced similar results. Habitat associated with thermoregulation (e.g. shade or pools) may be more important to fur seals in Peru, which breed at lower latitudes and are at greater risk of overheating on land than other populations. Habitat with minimized human access may be especially important to seals in small populations in which individuals may perceive themselves as more vulnerable because of decreased vigilance and dilution effects. Seals in our study selected breeding habitat with stacked rocks, which create shade and tide pools for thermoregulation and make human access difficult; but pups might suffer higher mortality in this habitat. We hypothesize that fur seals in Peru may exhibit an Allee effect, whereby suitability of habitat varies with population abundance.     

Suitability of habitat for spawning lake trout

We provide further insight into the reproductive ecology and spawning requirements of lake trout. New comparative information about substrate characteristics, sediment transport, quality of interstitial water at spawning substrates, and the role of temperature in site selection and time of spawning is given for lakes Simcoe and Manitou (Ontario) and Seneca Lake (New York). Spawning lake trout commonly use stable lag deposits derived from glacial sediments, or relict features such as fans, bars or submerged talus slopes. Artificial breakwaters of broken material may also provide suitable substrates. Optimal particle sizes range from 4 to 10 cm diameter but larger materials to 30 cm are also successfully utilized for spawning. The transport of finer particulates by wind generated water movements may limit the suitability of some substrates and successful spawning sites are usually remote from depositional effects. Successful embryo development is associated with low nutrient conditions, with high dissolved oxygen (>7 mg L^-1) and with low un-ionized ammonia (<12.5 g L^-1) in the interstitial water of spawning substrates. Shallow-water spawning appears to be the common strategy of colonizing lake trout. Some deepwater spawning in the Great Lakes may reflect initial colonization in shallow-water and adaptation to later increases in water level, but some may also reflect unique behavioural and physiological adaptations. Temperature is an important cue, and many wild and hatchery stocks spawn at 8 to 13 °C with latitudinal shifts in the actual time of spawning. These requirements are summarized as a dichotomous key for evaluation of approaches to restoration of lost or damaged lake trout stocks.Presented at the Conference on Rehabilitation of Lake Trout in the Great Lakes: A Critical Assessment (sponsored by the Great Lakes Fishery Commission, Ann Arbor, Michigan, January 10–14, 1994).     

Fish and decapod crustaceans inhabiting drifting algae in Jervis Bay,New South Wales

Abstract This study documents the fish and decapod crustaceans inhabiting a bed of Gracilaria verrucosa that was drifting on the bottom of a temperate marine embayment in relatively deep water (15- 18m) during autumn 1991. Fauna were sampled with diver-operated enclosure nets. Relatively few species inhabited the algae at this time, and the assemblage was primarily a subset of that in adjacent Posidonia australis beds. Three fish species [Neoodax balteatus (Odacidae), Cristiceps australis (Clinidae), Siphamia cephalotes (Apogonidae)] and one species of crab [Nectocarcinus tuberculosus (Portunidae)] dominated the catches numerically. A further 14 fish and decapod species were relatively rare. Neoodax balteatus, C. australis and N. tuberculosus were caught at all life stages and appeared to be permanent residents of the Gracilaria. Few juveniles of other species were captured, which indicates that these algal wracks may not be an important nursery habitat for seasonally resident fish species. Trachurus novaezelandiae and a number of other fish species that associate with a variety of benthic habitats appeared to be transient visitors. The biomass of algae varied significantly within the bed, but algal biomass was not a good indicator of faunal abundances. The low species richness of the fish and decapod crustacean assemblage may be related to both lower recruitment in deeper water and to unfavourable characteristics of the alga.     

毛乌素沙地草地种植管理咨询系统的开发

 本研究初步开发了一个用于毛乌素沙地草地种植管理咨询的专家系统ASSG。这个系统将当地生态系统管理专家们的经验知识和对土壤水分动态的理论研究成果结合起来以产生对于土地利用和种植的作物种类及品种的最优管理策略和最适的植被覆盖率。本系统利用3个层次的推理过程和结构化的知识库,通过咨询过程—步步地引导用户得到最优种植管理策略。在每—层次的推理中,本系统提供给用户多重选择,根据用户的意愿进行下一步的推理。这一推理的交互作用机制为用户获得适宜的咨询结果提供了最大的便利性。本系统的主体部分山Turbo Prolog语言完成,该语言是一种用于开发专家系统的描述性语言。基于土壤水分平衡原理的最优植被覆盖率模型由C语言实现,并应用多语言编程技术将之嵌入程序主体中。系统的样本运行结果表明本系统运行便利,并能产生合理的种植管理策略。     

松嫩草原碱化草地角碱蓬群落水分生态的研究

 本文采用自行设汁的蒸散仪和加拿大Campbe 11科学仪器公司生产的自动气象设备测定了松嫩草原碱化草地角碱蓬群落的蒸散、蒸腾量、太阳辐射及空气温度等环境因子。分析结果表明生长季的睛天条件下,角碱蓬群落的蒸散、蒸腾速率的日进程均为单峰曲线,且各月份间差异很大。群落蒸腾速率与太阳辐射强度、空气温度、相对湿度、风速等环境因子紧密相关,其中与太阳辐射强度呈极显著正相关关系。生长季降雨量和土壤含水量在角碱蓬群落水分循环与平衡的过程中起重要调节作用。1992年6～8月的生长季中,角碱蓬群落总的水分亏缺较少(6.3mm),但各月份间差异很大,其中6月份水分亏缺最高(30.1mm)。     

人类口腔小生境微生物的多样性

本文论述了人类口腔中微生物的物种多样性,口腔小生境的复杂性与微生物多样性的关系,以及口腔中微生物变化与人类疾病和健康的关系。     

High-elevation rock outcrop vegetation of the Southern Appalachian Mountains

Abstract. Species composition patterns and vegetation-environment relationships were quantified for high-elevation rock outcrops of the Southern Appalachian Mountains, an infrequent and insular habitat in a forested landscape. Outcrops occur over a wide geographic range encompassing extensive variation in both geology and climate. Geographic-scale factors interact with site-scale factors to produce variation in vegetation among outcrops. Similarly, site-scale factors interact with micro-scale factors to produce variation in vegetation within outcrops. To provide a quantitatively-based classification of outcrop vegetation we used a TWINSPAN analysis of 154 100-m² plots. We recognized nine communities that primarily correspond to different combinations of elevation, bedrock type, geography, and moisture. Within outcrops of a single bedrock type, vegetation composition of 100-m² plots was consistently correlated with elevation and solar radiation, but relationships to soil nutrients varied with bedrock type. Both site-scale (100 m²) factors (e.g. elevation, slope, aspect, and bedrock type) and plot-scale (1-m²) microsite factors (e.g. soil depth, vegetation height, soil nutrients) were strongly correlated with species composition at the 1-m² level. Environment can be used to predict composition more effectively for 100-m² plots on a single bedrock type than either across bedrock types or at a 1-m² scale. Composition-environment relationships resemble those described for outcrop systems from other regions with pronounced topographic relief more than they do those described for the nearby but flatter and lower-elevation outcrops of the Southeastern Piedmont. There is strong spatial autocorrelation in this community, perhaps owing to dispersal limitation. Consequently, a comprehensive conservation strategy must include reservation of both a range of geologic types and a range of geographic locations.