Differential composition in the age of mates in Bonelli’s eagle populations: The role of spatial scale, non-natural mortality reduction, and the age classes definition

Monitoring of the age of mates, a method proposed to detect early warning signals for demographic trends in long-lived bird populations, showed different patterns when the study was performed on a single Bonelli’s eagle subpopulation of Andalusia (South of Spain) than when the whole region is taken into account. In this respect, we discuss the role of the spatial scale, the origin of reduction in non-natural mortality and the definition of the used age classes. For a correct monitoring of the age of mates in the Bonelli’s eagle, we propose the two age classes previously suggested, adult and non-adult, but paying particular attention to the late subadult individuals, specially when the monitoring is performed in a wide region by different field work groups. Likewise, it is necessary for monitoring age of breeders in long-lived species with deferred maturity to collect data from a sample well distributed over space, taking regularly into account pairs from the edge and from the centre of population. Besides, it is important to monitor those subpopulations with different known threats, providing them their relative importance among the whole population. Finally, conventional monitoring of the age of mates seems to generally be a reliable way to predict viability changes of bird populations, except when adult by adult replacements take place by reduction in juvenile mortality.     

Survival and spatial fidelity of moufl on (<Emphasis Type="Italic">Ovis gmelini</Emphasis>): A Bayesian analysis of an age-dependent capture-recapture model

We study the influence of age and sex on survival and spatial fidelity of moufl on (Ovis gmelini) in the Caroux-Espinouse massif. Survival and movement probabilities are estimated through a Bayesian analysis of an age-dependent capture-recapture model. Prior information is based on external data, namely on radio-tracked animals. Recapture rates differed between age, sexes, and areas. Whatever the area, survival of males and females less than 5 years old was high and decreased for older animals, particularly males. Female spatial fidelity was high; males were as faithful as females to their capture area in their first 2 years of life but gradually used distinct areas in two successive years as they were getting older.     

Foraging site fidelity shapes the spatial organisation of a population of female western barbastelle bats

Information about the spatial distribution of individual foraging habitats, which determines the space required by a population to be viable, is vitally important for the conservation of bats. Detailed knowledge of this kind is crucial for the design of nature reserves and management plans. Recent field studies that examined habitat use and home range distribution of bats largely ignored factors like traditional range use vs. intra- and interspecific competition, which may be responsible for the spatial organisation of a population home range. We investigated the home range sizes and distribution of a maternity colony of the western barbastelle bat via radio telemetry in four consecutive tracking sessions (2004-2007). Based on 19 data sets with a total of 2737 fixes obtained from 12 females, we examined (i) how colony members partition the population home range (home range overlap analysis), and (ii) if individuals tracked over several years exhibit site fidelity. Home range sizes ranged from 125 to 2551 ha (median: 403 ha), with a median number of 2 core areas (range: 1-5 core areas per individual per year). The core area sizes ranged from 5 to 285 ha (median: 67 ha). A home range and core area overlap analysis showed that site fidelity across years seems to be more important for home range distribution than competition among colony members. This allows researchers to combine information from several years to get a deeper insight into the population’s spatial requirements.     

The use of gypsum for preventing soil sodification: effect of gypsum particle size and location in the profile

Laboratory studies were conducted on a mixture of surface soils from the Nile Delta (Egypt). Twenty-two soil columns, initially saturated both with respect to their water-holding capacity and to their base exchange capacity with calcium, contained 0.0, 0.25, 0.5, 1.0 and 2.0 per cent solid gypsum in the total weight of the solid material in the column. Three particle sizes of gypsum (>0.5, 0.5–1 and 1–2 mm) were mixed either with the top layer or with the whole soil column. The result of leaching these columns with saline water (36 meq 1^?1 NaCl+4 meq 1^?1 CaCl₂) at 0.1 cm h^?1 was compared with a mathematical model based on thermodynamic equilibria. The three different particle sizes gave the same experimental results. Applying a given amount of gypsum to the surface soil was more effective in reducing the exchangeable sodium percentage (ESP) than mixing the same quantity through the soil. The mathematical model adequately predicted the changes in the soil column.     

Solid phase microextraction of volatile emissions of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae): influence of fly sex, age, and mating status

Considerable efforts have been devoted to understanding the courtship behavior and pheromone communication of medflies; however, the sex pheromone composition is still a controversial subject. The discovery of new components affecting medfly behavior would be of interest for medfly control methods based on semiochemicals. This work describes volatile compounds emitted by Ceratitis capitata collected using solid phase microextraction. The volatile study was conducted according to an experimental design with three factors (sex, age, and mating status) assumed to be relevant for better understanding the chemical communication. Emission data were treated by means of principal component analysis, a statistical methodology not previously applied to the study of volatiles emitted by fruit flies. The characterization of emission patterns could be useful for the selection of compounds to be further investigated in biological assays to improve knowledge of the key semiochemicals involved in medfly behavior.     

Conservation of European wild rabbit populations when hunting is age and sex selective

Several predator species at risk of extinction in Southwestern Europe are dependent on the population density of European wild rabbits Oryctolagus cuniculus. Rabbit populations in the region, however, have recently undergone dramatic decreases in population density, which may be exacerbated by hunting. Current hunting policies set the autumn-winter season, just before the start of rabbit reproduction, as the main hunting season, and previous theoretical models have estimated that the current hunting season may have the greatest negative impact on rabbit abundance and should be changed. We utilised a model for rabbit population dynamics to determine the effects of the timing of hunting during two seasons, summer and autumn, on the tendency of rabbit populations to be over-harvested and on the number of rabbits hunted. This model included field estimates of age- and sex-selection biases of hunting by shotgun. Scenarios with different hunting rates and sex- and age-selection probabilities of hunting were simulated for populations with different turnover levels and with and without compensatory mortality mechanisms. Field estimations showed that hunting in summer was juvenile-biased whereas autumn hunting was juvenile- and male-biased. In contrast to previous findings, our modelling results suggested that hunting in autumn may be the most conservative option for harvesting of rabbit populations, since these populations were more prone to be over-harvested during the summer. The differences between the two seasons in number of rabbits hunted were dependent on population dynamics and hunting sex- and age-selection probabilities. Our findings suggest that altering of current hunting policies would not optimise the exploitation or conservation of wild rabbit populations, but that the latter may be improved by some changes in the timing of hunting.     

The rhizosphere effect of tea on soil microbes in a Himalayan monsoonal location

Monthly investigations of the microbial population associated with tea soils, in terms of colony-forming units assessed by the plate-count method, were carried out at three different soil depths for a period of 12 months. Three groups of microbes, bacteria, actinomycetes, and fungi, were examined. Contrary to general observations, the rhizosphere: soil ratios were found to be consistently below 1 in samples taken from established tea bushes, indicating an overall negative rhizosphere effect. Interactions among certain microorganisms may also have contributed to this effect. Nevertheless, the rhizosphere of young tea plants and that of a number of other perennial plants, of different ages, growing in established tea fields, appeared to stimulate microbial growth. The negative effect of the rhizosphere of older tea bushes does not appear to be a common phenomenon that is related to the aging of plants in general, but seems to be unique and specific to tea plants.     

The effect of post-fire stand age on the boreal forest energy balance

Fire in the boreal forest renews forest stands and changes the ecosystem properties. The successional stage of the vegetation determines the radiative budget, energy balance partitioning, evapotranspiration and carbon dioxide flux. Here, we synthesize energy balance measurements from across the western boreal zone of North America as a function of stand age following fire. The data are from 22 sites in Alaska, Saskatchewan and Manitoba collected between 1998 and 2004 for a 150-year forest chronosequence. The summertime albedo immediately after a fire is about 0.05, increasing to about 0.12 for a period of about 30 years and then averaging about 0.08 for mature coniferous forests. A mature deciduous (aspen) forest has a higher summer albedo of about 0.16. Wintertime albedo decreases from a high of 0.7 for 5- to 30-year-old forests to about 0.2 for mature forests (deciduous and coniferous). Summer net radiation normalized to incoming solar radiation is lower in successional forests than in more mature forests by about 10%, except for the first 1–3 years after fire. This reduction in net radiative forcing is about 12–24 W m⁻² as a daily average in summer (July). The summertime daily Bowen ratio exceeds 2 immediately after the fire, decreasing to about 0.5 for 15-year-old forests, with a wide range of 0.3–2 for mature forests depending on the forest type and soil water status. The magnitude of these changes is relatively large and may affect local, regional and perhaps global climates. Although fire has always determined stand renewal in these forests, increased future area burned could further alter the radiation balance and energy partitioning, causing a cooling feedback to counteract possible warming from carbon dioxide released by boreal fires.     

A partial chloroform-fumigation technique to characterise the spatial location of bacteria introduced into soil

Bioluminescence-marked cells of Pseudomonas fluorescens were inoculated into soil by introduction into pores of two different size classes (< 6 and 30–60 m neck diameter). Partial chloroform fumigation resulted in a differential killing of cells depending on the placement of the inoculum within the soil pore network and on the period of fumigation. Reduced survival was associated with increasing periods (30–120 min) of fumigation, and with inoculum placement into larger rather than smaller pores. Comparison of the effects of partial fumigation on cells introduced into four soils of contrasting pore-size distribution highlighted the need to calibrate the method on the basis of air/water-filled pore space and chloroform diffusion dynamics for different soil types. It is proposed that partial fumigation facilitates spatial characterisation of the distribution of bacterial cells introduced into soils.     

The nitrogen content of corn grain as affected by hybrid,population, and location

Abstract

Samples were taken from 9 of the 20 major experiments which comprised the Illinois commercial corn (Zea mays L.) performance trial and evaluated for grain yield, percent grain N, and grain N yield.

The mean percent N in the grain was 1.54%, with 91.8% of the samples between 1.34 to 1.74%. Although location and plant population affected the mean values, the range of values about the mean was relatively unaffected. Grain N yield was more closely correlated with grain yield than with percent grain N.     

The role of life-history and location of barriers to migration in the spatial distribution and conservation of fish assemblages in a coastal river system

Water resource development in coastal river catchments contributes to poor fish assemblage health due to the effects of barriers to migration and altered flow regimes. Impacts of migration barriers on fish assemblages depend primarily on the location of each barrier within the river network and migration needs of regional fish fauna. This study examined how temporal and spatial patterns in the distribution and composition of fish assemblages was associated with varying estuarine connectivity and migration barriers in higher altitude reaches in the eastern Hunter River catchment, temperate Australia. Species richness and abundances of diadromous species were expected to be greater in a tributary catchment with unrestricted connectivity to the Hunter River estuary when compared to a neighbouring tributary catchment with restricted connectivity. Six diadromous species were sampled only, or in greater abundances, in the unrestricted tributary when compared to the restricted tributary. As a consequence, assemblage composition in the restricted tributary was dominated by non-diadromous species. Greater abundances of the amphidromous Cox’s gudgeon (Gobiomorphus coxii) were sampled in the unrestricted tributary following their estuarine-freshwater upstream juvenile migration period when compared to the restricted tributary. Differences in the accumulations of migratory species immediately downstream of upland barriers between the two levels of estuary connectivity indicate that migration barriers in lowland reaches have significant effects throughout the entire catchment. Results of this study indicate that the location of each barrier to migration within river networks has varying consequences for catchment-scale connectivity loss and assessing the impacts of multiple barriers. Determining the effects and most appropriate management of migration barriers requires that all obstructions within a river network are recognised, as multiple barriers can have cumulative and interacting consequences for freshwater fish fauna, especially diadromous species.     

土壤水盐空间变异尺度效应的研究

水文学和土壤学中的尺度问题是目前水土科学研究的前沿课题之一。该文利用空间信息科学——地质统计学、根据设计的各种田间网格，在一维和二维(平面)空间中初步研究了黄河河套平原长胜试验区中小尺度的土壤水分和盐分随采样尺度所表现出的空间变异(结构性)的某些规律，表明采样尺度的划分和选取与水分和盐分的空间变异性大小有密切关系，尺度效应的研究对于指导农业技术研究中野外采样系统设计、节省外业调查的工作量及科学地进行内业计算、评估和揭示农业工程中具有地学特征的区域性自然规律有重要作用。     

How much do site age, habitat structure and spatial isolation influence the restoration of rainforest beetle species assemblages?

Reforestation has been suggested as a way to mitigate the effects of tropical rain forest loss. However, factors influencing the successful colonisation of biota into newly created rainforest are poorly understood. We assessed beetle species assemblages with flight interception traps, in sites undergoing rainforest restoration across the largely cleared landscape of the Atherton Tablelands in north-eastern Queensland, Australia. There were two levels of site age (2-4 years and 6-17 years) and two distances from intact rainforest (adjacent and >0.9 km), with six sites in each treatment, together with six reference sites in each of pasture and small rainforest remnants (n = 36 sites). Multivariate metrics were used to assess the restored sites’ relative similarity to pasture and rainforest, in terms of both physical habitat structure and beetle species composition within ten family groups. Older restoration sites were structurally most similar to rainforest. Older sites and those adjacent to rainforest had a more rainforest-like beetle species composition (without significant interaction). However, even the closer and older sites had a substantially lower abundance and richness of rainforest-associated beetles than did rainforest. Age effects were generally stronger than distance effects, with the latter appearing to be entirely driven by rare rainforest species. Beetle assemblage similarity to rainforest was more strongly correlated with structural similarity to rainforest than with age, except within older sites. The use of revegetation techniques which lead to more rainforest-like structural conditions appears to be of over-riding importance in catalysing the rapid acquisition of volant rainforest beetle assemblages in the initial stages of restoration.     

Population sizes, site fidelity and residence patterns of Australian snubfin and Indo-Pacific humpback dolphins: Implications for conservation

Very little is known about the ecology of snubfin Orcaella heinsohni and Indo-Pacific humpback dolphins Sousa chinensis in Australian waters. We used photo-identification data collected between 1999 and 2002 in Cleveland Bay, northeast Queensland, to estimate abundance, site fidelity and residence patterns of these species in order to make recommendations for their effective conservation and management. Our abundance estimates indicate that less than a hundred individuals of each species inhabit this coastal area. Even with relatively unbiased and precise abundance estimates population trends will be extremely difficult to detect in less than three years unless changes in population size are very high (>20% p.a.). Though both species are not permanent residents in Cleveland Bay, they both used the area regularly from year to year following a model of emigration and reimmigration. Individuals of both species spend periods of days to a month or more in coastal waters of Cleveland Bay before leaving, and periods of over a month outside the study area before entering the bay again. Because of their small population sizes and movement patterns, snubfin and humpback dolphins are particularly vulnerable to local extinction. Our results illustrate that: (1) detection of population trends should not be a necessary criterion for enacting conservation measures of both species in this region, and (2) efforts to maintain viable populations of both species in Cleveland Bay must include management strategies that integrate anthropogenic activities in surrounding areas.     

Formation of hemoglobin adducts of acrylamide after its ingestion in rats is dependent on age and sex

The effect of fiber and fat contents of food and of age and sex of animals on the formation of hemoglobin adducts of acrylamide (AA-Hb) in blood has been studied. The results suggest that the absorption of acrylamide (AA) present in food is not affected by the fiber or fat contents of food. However, AA-Hb resulting from the intake of an aqueous solution of AA is dependent on the age and sex of rats: AA-Hb levels were higher in females than in males (3.53- and 2.55-fold higher, respectively, for AA doses of 25 and 100 mg/kg) and in younger than in older rats (30.1% higher in 1.5 month old as compared to 14 month old rats). In males, AA-Hb levels found after the oral administration of AA in an aqueous solution were significantly lower than those found after dietary or intravenous administration. In conclusion, these results show the existence of significant differences in AA bioavailability from an aqueous solution depending on the sex and age of animals. If similar differences also occur in humans, they would be relevant to assess the exposure of different subpopulations to AA.     

The effect of tea plantation age on soil water-stable aggregates and aggregate-associated carbohydrate in southwestern China

Soil carbohydrates constitute an important component of soil organic matter (SOM), and substantially contribute to the stabilization of soil aggregates. Here, we aimed to investigate the distribution of water-stable aggregates and carbohydrates within water-stable aggregates of soil in tea plantations located in Zhongfeng Township of Mingshan County, Sichuan, which is in southwest China. Samples were collected from tea plantations of different ages (18, 25, 33, and 55 years old) and an area of abandoned land was used as a control(CK). We also examined correlations between soil carbohydrates fractions and aggregate stability. The results showed that the mean weight diameter (MWD) of soil aggregates in the tea plantations was significantly higher than that the control. Furthermore, the soil aggregate stability was significantly enhanced in tea plantations, with the 25-year-old plantation showing the most pronounced effect. Soils in the plantations were also characterized by higher concentrated acid-extracted carbohydrate content, and carbohydrate content in both surface and sub-surface layers were higher in the 25-year-old plantation. We also detected a significant positive correlation between the carbohydrate content of soil and MWD after tea plantation (P < 0.01). Notably, the association between dilute-acid extracted carbohydrate and the aggregate stability showed the highest correlation, indicating this carbohydrate fraction could be used as an index to reflect changes in soil quality during tea plantation development. We should develop a potential fertilisation programme to maintain SOM- Carbohydrates within aggregates and the appropriate pH for preventing soil structure degradation after 25 years of tea planting.     

种植大豆地表土壤溅蚀效应及其空间分布特征

为系统研究种植大豆条件下农地溅蚀速率变化特征并建立简单易用的模型,评价大豆种植对土壤溅蚀的影响,采用室内模拟降雨的方法,测定了不同降雨强度(40 mm h-1和80 mm h-1)、不同大豆生长阶段(始花期、盛花期、结荚期和始粒期)下的穿透雨强度和溅蚀速率,分析了大豆冠下溅蚀速率与叶面积指数和穿透雨强度的关系,探讨了冠下溅蚀速率的空间分布特征.结果表明:与裸地相比,在大豆全生育期,大豆冠下平均溅蚀速率在设计雨强40 mm h-1和80 mm h-1下,分别减少了62.85％和60.74％.冠下平均溅蚀速率随叶面积指数增加呈显著的增加趋势,且随降雨强度的增大而显著增加.冠下各点溅蚀速率受相应各点的穿透雨强度影响在80 mm h-1设计雨强下较为显著,随穿透雨强度的增加而增加.大豆冠下溅蚀速率的空间分布与穿透雨的分布具有一定的对应性,即冠下穿透雨较为集中的区域会在一定程度上增加溅蚀的发生,并导致冠下溅蚀速率分布不均,大豆冠下穿透雨是冠下溅蚀产生和分布的主要能量来源.该研究提出的大豆冠下溅蚀速率模型可为坡耕地土壤侵蚀防治和农田灌溉有效利用提供理论支持.