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1.
The patterns of growth and development have been studied in L. maculatus early life stages of different ecological groups (pelagic and demersal) from Kongsfjorden and Billefjorden (the northwestern coast of West Spitsbergen). It has been found that the growth rate of larvae markedly increases by age 2+ (stage L2), which is due to their transition to exogenous feeding. Consideration is given to changes in the length and condition of the lipid sac (a provisory organ) in the period of its formation, growth, and resorption in the course of ontogeny. The lipid sac reaches the maximum size at stage L4* and is resorbed at stage L5. Analysis of individual variation in the size and body weight of fish early life stages provides the possibility to evaluate the adaptation capacity of a species under specific conditions of the Arctic.  相似文献   

2.
Body size variation across environmental gradients has received considerable attention in evolutionary ecology in recent years. In this study, we investigated body sizes and age structure using skeletochronology in male Polypedates megacephalus from five sites with the attitude ranging from 449 to 1300 m. The results showed age at sexual maturity in males was 2 years old, and the longevity was 5 years old except for Changning population of 3 years. Body size was significantly correlated with age within each population except for Changning population. Average age did not differ significantly among populations. Body size of individuals also did not differ across populations when removing the effect of age, which did not follow Bergmann’s rule.  相似文献   

3.
Populations from different environmental habitats indicate variation in life history traits and these differences are mostly related to longevity, age and size at maturity. In this study, age structure, longevity, survivorship and sexual size dimorphism of Near Eastern fire salamander (Salamandra infraimmaculata) were assessed by means of skeletochronological analysis. Maximum lifespan was recorded to be twelve years in females and eleven years in males and age at maturity was estimated as three and four years for both sexes. Females had significantly larger SVL than that of males, while age structure and mean age did not differ between sexes. Age and body size were positively correlated with each other for both females and males. Since the populations of the Near Eastern fire salamander in Turkey are in decline, the present study which provides preliminary data on life history traits of this species could be helpful for future biological studies.  相似文献   

4.
5.
The influence of recreation activity on grass cover was studied in a herbaceous birch forest within a territory of city development. Effects of the activity depended on size and arrangement of recreation sites. It was found that most of the forest was at the second stage of degradation, while degradation of forest edges was considered as intermediate between the second and third stages. Forest edges and glade-clump communities play a particular role in maintaining the stability of recreational forests.These ecotones are both barriers preventing introduction of alien plant species into a cenosis and centers of dissemination of ruderal and meadow species.  相似文献   

6.
Environmental conditions developing at the boundary of windfall- and fire-damaged forest biocenoses at different stages of progressive succession have a positive effect on the total abundance of rodents, but the role of ecotone in forming the structure of their microhabitats is ambiguous. The complex of biotic and abiotic conditions in the ecotone has a positive influence on the size of shrub coverage area and the abundance of saplings, whereas the influence of the edge effect on other microhabitat parameters (namely, herbaceous and moss coverage) is negative or neutral.  相似文献   

7.
The first birth marks a transition of a woman into motherhood. It contributes substantially to overall fertility of each individual woman. The age at which childbearing begins influences the number of children a woman bears throughout her whole reproductive life span. Thus, the mother’s age at first birth influences the total number of births that she might have in her life, which impacts the size, composition, and future growth of the population. Child-bearing at very young ages is common among the poor in Bangladesh. The objective of the present study is to examine the factors associated with age at first birth among slum dwellers of five selected slums (locally, colony) in Sylhet city corporation area, Bangladesh. The data of this study was collected from 520 women aged 14–50 years. The study found that almost 93% of women were married by the ages of 18 years and about 56% of the women have had their first child by the age of 18 years. The Ordinary Least Squares (OLS) regression model was used to analyze the factors correlated with women’s age at first birth. The regression model is significant with an F-value of 49.48 and can explain 40.4% of the variation in the dependent variable as it is indicated by the R-square.  相似文献   

8.
This research conducted on municipal solid waste management for the first time quantified food spoilage as being 8.8% weight of all officially collected household garbage in the Brazilian city under study. The unexpected size of this waste fraction gave rise to work on the causes of waste and on its distribution over the product life cycle specific to fruit and vegetables. Waste was defined as being the combination of losses and scraps. Administrative shortcomings were identified as basic reasons for waste. At the producer and consumer ends of the cycle, negligence was shown to be the single most important problem. Fruit and vegetables deteriorate during the operations of handling, transport, packaging, storage, selling and consumption. The study detailed the occurrence of waste at all of these stages. In the medium-size Brazilian city, the total waste of fruit and vegetables was shown to amount to 16.6% weight in the marketing stage of the life cycle. At the consumer level, it was measured as 3.4% weight of all household garbage. Specific reasons for this waste were identified at the levels of producer, wholesaler and retailer. Short-term remedies were pointed out that invariably corrected deficient management procedures. It was shown that very simple administrative measures can significantly reduce the spoilage of fruit and vegetables. Long-term strategies involve the creation of sample cases for administration of the fruit and vegetables life cycle at all stages.  相似文献   

9.
Studies on the population structure and dynamics of the stone centipede Monotarsobius curtipes C. Koch in soils of the northern Kola Peninsula have shown that, with respect to abundance and biomass, this species is a dominant of the soil macrofauna and, in particular, of the trophic group of zoophages. Life in high northern latitudes does not disturb the sex and age structure of populations but limits the reproductive activity of these centipedes. Specific biological features of M. curtipes at the northern periphery of its range include the absence of repeated breeding, completion of several developmental (age) stages within a short growing season, and long ontogeny involving several winterings.  相似文献   

10.
通过丹阳市4个村320户农户实地问卷调查,分析了丹阳市宅基地使用权流转意愿的影响因素,由Logistic回归分析模型,给出了影响因素的驱动力、贡献率的数学表达。结果表明:文化程度、宅基地个数、家庭总收入等影响因素对流转意愿呈正相关;户主年龄、家庭人口数量等影响因素对流转意愿呈负相关。同一农户的影响因素在不同阶段对流转意愿度的贡献率不同,家庭收入和户主年龄是影响宅基地流转的主要因素,他们对宅基地流转分别起着推力和阻力作用,在相互作用过程中,两者之间彼此消长。实地抽样结果分析表明,丹阳农村户主文化程度若为初中且年龄在35岁时,家庭收入能达到34 000元的话,宅基地使用权流转意愿度超过50%。以后每年家庭收入能有一定增速的话,农户流转意愿度将持续保持在50%以上。  相似文献   

11.
The mitotic activity and sizes of corneal epithelial cells in postmetamorphic Rana arvaliswere studied in the populations exposed to different degrees of anthropogenic impact in the city of Yekaterinburg. The studies were conducted at the initial stages of frogs' terrestrial life in three consecutive years. Mitotic activity exhibited a slight positive correlation with the liver index, which indirectly reflects the general metabolic rate in young frogs. The combined estimation of proliferative activity, epithelial cell size, and relative liver weight had the highest information value. There was a relationship between the mitotic index and liver index in young frogs from habitats with the highest level of anthropogenic transformation. This indicates that morphogenesis is well-balanced and is likely to decrease the probability of morphological abnormalities in frogs developing in the unstable environment. This physiological property allows the populations to exist and reproduce in urbanized areas.  相似文献   

12.
Changes in the survival parameters of the red fox were analyzed at different phases of the population cycle. It was found that the survival rate in all age classes, including newborns, drastically increased at the phase of population growth. The relationship between the general mortality rate and population size was determined. A hypothesis concerning the mechanism of these changes in the general mortality rate is suggested.  相似文献   

13.
Periodic monitoring (by age stages) of the growth energy and health of trees has been performed in population cultures of white birches established on a half-sib basis (for the first time in Russia). The results show that the pattern of growth and development and the health (survival) of provenances tested in population cultures depend primarily on the ecobiological properties of birch species and also on the distance and direction of seed transfer.  相似文献   

14.
The correlation between the timing of adult emergence and variation in morphophysiological parameters of males and females has been analyzed in the black-veined white Aporia crataegi L. In 2013 to 2015, black-veined white butterflies were collected from a natural population in the south of Sverdlovsk oblast throughout the emergence period; at the same time, adult insects were reared from pupae in individual cages. Comparison of the field observations in nature and the results of rearing preimaginal stages has shown that the largest adults are the first to emerge, while the smallest are the last to emerge. This pattern holds true both for the parameters varying throughout the adult insect life (body weight and relative abdomen weight) and for the permanent characteristic of the “structural” size (wing area). The influence of protandry and food availability to caterpillars on the variation in the size of adult A. crataegi during the period of generation emergence is discussed.  相似文献   

15.
Larval amphibians are particularly likely to encounter variation in rearing temperature and resource availability due to variation in aquatic breeding habitats. In this study, plasticity in growth rates, larval mass, larval period, and size at metamorphosis were examined in Rana kukunoris Nikolskii, 1918 under different combinations of temperature and food level. Larval period and larval body mass was sensitive to food level, and varied with temperature. Tadpoles metamorphosed at an older age at low temperature than those reared at warm temperature. Food level was a significant affect on larval period at low temperature, but not at warm temperature. Mass was heavier for tadpoles reared at low temperatures than those reared at warm temperatures. The effect of food level depended on temperature, because larvae reared at low temperature that were offered a high food level achieved a larger size than larvae offered a low food level, but this did not occur at warm temperature. Therefore, we suggest that high food availability at low temperature prolonged developmental periods, thus larvae are larger as metamorphs than those reared at warm temperatures.  相似文献   

16.
Original data on 14 urban floras in the Ural–Volga region have been analyzed to estimate the effect of the geographic location, topography, climate, size, and age of a city on the species richness of its flora. This parameter in different cities varied from 288 to 973 species, with the proportion of alien species varying from 21 to 41%. Factors of flora richness were estimated by multiple linear regression using principal component estimates obtained by factor analysis of 13 city characteristics as predictors. It has been confirmed that the richness of urban floras depends primarily on the city size, which accounts for greater proportions of variation in the number of native species (56%), the number of alien species (91%), and the total number of species (71%). In addition, variation in the number of native species is determined by terrain elevation (22%), increasing at higher elevations. The proportion of alien species in the urban flora does not depend on the size of the city and is negatively correlated with terrain elevation.  相似文献   

17.
ABSTRACT

This paper establishes a diagnostic model for assessing the rationality of size structure of urban agglomerations (UAs) in China. The model is designed to determine from a three-dimensional index including size distribution index (SDI), size compactness index (SCI), and size efficiency index (SEI). The spatio-temporal pattern of size structure involving the studied 19 UAs and its implications are explored. The results indicate that size structure of China’s UAs advanced from a low rationality development stage to a moderate rationality development stage in 1995–2015. Among them, the SDI and SEI were reasonably high, and the SCI was relatively low. Spatially, the high rationality UAs were distributed across eastern China, while the low rationality UAs were located in western China. UAs with positive size structure possessed typically a dual- or multicenter urban structure, while UAs with negative size structure usually presented as a single-center structure. The evolutionary trajectories of rationality of size structure of UAs can be summarized as four different stages. Our findings suggest that, in addition to consolidating the status of national-level UAs, the development of regional-level UAs should be promoted. Also, the fostering focus and direction should be oriented toward an UA with dual- or multicenter spatial structure.  相似文献   

18.
Results of stationary studies on the spatial location of sables (Martes zibellinaL.) belonging to different age and sex groups are summarized. Mapping the sites where 388 animals were taken, it was found that young animals tended to live near floodplains; adult animals, on watersheds. Analysis of sables taken by commercial hunters (n= 1833) made it possible to estimate the age composition and the degree and spatial distribution of the hunting pressure on sable populations in three areas of the Ob region. The spatial separation of young and reproductive animals is interpreted as a group adaptive response to the specific distribution pattern of different habitats typical of this species and to the pattern of animal elimination. It is proposed to use the specific pattern of animal distribution for maintaining the size of the population that is subject to hunting. Specifically, reserve (reproductive) territories should be organized in watershed areas.  相似文献   

19.
长江口南支邻近水域碎波带仔稚鱼群落结构的差异及关联   总被引:1,自引:0,他引:1  
为探明长江口南支及邻近水域碎波带仔稚鱼群落结构的差异及相互联系,分别对长江口南支、杭州湾北岸与泗礁沙滩碎波带进行小型拖网(1 m×4 m,网目1 mm)取样调查,样品在实验室内进行种类鉴定及数量统计。结果显示:种类组成方面,3处水域分别采集到仔稚鱼11科40种、23科59种与28科46种,共有种7种;洄游性种类、河口性种类与海洋性种类分别为3者优势类群;单位捕捞努力量渔获量(CPUE)长江口南支最高,为41.45 ind./haul,泗礁沙滩最低,为5.72 ind./haul;长江口南支仔稚鱼各发育阶段个体分布相对均匀,杭州湾北岸以稚鱼个体为主,泗礁沙滩以后弯曲期仔鱼占优势;多样性指数杭州湾北岸最高,为2.19,泗礁沙滩最低,为1.75;长江口南支与杭州湾北岸群落相似度较高。数量变动方面,3处水域种类数均为8月最高,CPUE分别于8月、9月与5月达到峰值。生境功能方面,长江口南支兼具定居地、保育场与暂居地等功能,杭州湾北岸与泗礁沙滩则仅为保育场与暂居地;3处水域共有种中国花鲈(Lateolabrax maculatus)分别在不同时间段及不同发育阶段进入3处水域栖息保育,长江口南支及其邻近水域碎波带是其向岸及溯河洄游过程中的重要保育场与中转站。 关键词: 长江口南支;邻近水域;碎波带;仔稚鱼;群落;差异与关联  相似文献   

20.
The current dynamics of ecosystems of the forest-steppe system is most adequately described via determining the probable trajectories of changes in its elements in a simple Markov chain. The obtained data have made it possible to determine the direction of succession and draw its scheme. Theoretically possible series of community development are presented. The succession of community restoration from the spread of shrubs over steppificated fallow lands to the formation of low forests of European bird cherry has been analyzed. The restoration cycle of ecosystem dynamics is described by eight age stages.  相似文献   

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