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1.
Despite overwhelming evidence for a negative effect of inbreeding on fitness in plants and nonhuman animals, the exact nature of its effect in humans remains subject to debate. To obtain a better understanding of the effects of inbreeding on reproductive success in humans, we reconstructed the genealogies of the current inhabitants of a small and isolated Swiss village and used these to estimate the level of inbreeding of both members of all married couples, as well as their relatedness (i.e. the level of inbreeding of their offspring). Although there was no effect of parental relatedness on the number of children a couple had, we found that inbred mothers, but not inbred fathers, had significantly fewer children. Thus, although related couples did not have fewer children themselves, their inbred daughters did leave them with fewer grandchildren. Thereby, we provide evidence for the existence of inbreeding depression in human fertility, also in relatively outbred and egalitarian communities.  相似文献   

2.
A long-term study of land tenure, land transfer, and succession in one subclan of the Chimbu in the Papua New Guinea highlands takes up the relations between the agricultural cycle, family, and population growth in a period of rapid commercialization and cash cropping. Over a generation, land was held and allocated within families, among families within the subclan, and to kin and affines in neighboring groups. The land tenure, ownership, and use system allows for a very great deal of individual movement and land gifts, temporary or long-term, by land owner to kin and friends. Despite an agnatic ideology, individuals and local groups opportunistically accommodate to land needs. As cultivation becomes more intensive and semi-permanent, there appears to be a progression from fluidity of land rights in the clan or subclan to anchoring of rights and boundaries to individuals and families. It is suggested that this characterizes Chimbu land tenure; it is not a postcolonial phenomenon.  相似文献   

3.
The distribution and ecology of benthic, periphytic and planktonic rotifers were investigated in a wide range of alpine waterbodies in Austria. A total of 162 substrate classified samples was taken at 60 sampling sites situated between 1824 m and 2753 m a.s.l. in the Central Alps (predominantly gneiss) and between 1290 m and 1643 m a.s.l. in the Northeastern Calcareous Alps. Multivariate analysis allowed the recognition of distinct sampling site groups. Different groups of taxa were identified on the basis of their total frequencies of occurrence and frequency of co-occurrence. Several species were shown to have distributions restricted to particular groups of habitats. Habitat complexity, as indicated by taxon diversity and density of submersed vegetation, pH, conductivity, and temperature seem to be the principal components affecting community composition and distribution of single species in alpine waterbodies. Highest diversities were measured in limestone solution lakes and acid bog ponds on primary bedrock.  相似文献   

4.
Grasslands cover about 40% of the ice‐free global terrestrial surface, but their quantitative importance in global carbon exchange with the atmosphere is still highly uncertain, and thus their potential for carbon sequestration remains speculative. Here, we report on CO2 exchange of an extensively used mountain hay meadow and pasture in the Swiss pre‐Alps on high‐organic soils (7–45% C by mass) over a 3‐year period (18 May 2002–20 September 2005), including the European summer 2003 heat‐wave period. During all 3 years, the ecosystem was a net source of CO2 (116–256 g C m?2 yr?1). Harvests and grazing cows (mostly via C export in milk) further increased these C losses, which were estimated at 355 g C m?2 yr?1 during 2003 (95% confidence interval 257–454 g C m?2 yr?1). Although annual carbon losses varied considerably among years, the CO2 budget during summer 2003 was not very different from the other two summers. However, and much more importantly, the winter that followed the warm summer of 2003 observed a significantly higher carbon loss when there was snow (133±6 g C m?2) than under comparable conditions during the other two winters (73±5 and 70±4 g C m?2, respectively). The continued annual C losses can most likely be attributed to the long‐term effects of drainage and peat exploitation that began 119 years ago, with the last significant drainage activities during the Second World War around 1940. The most realistic estimate based on depth profiles of ash content after combustion suggests that there is an 500–910 g C m?2 yr?1 loss associated with the decomposition of organic matter. Our results clearly suggest that putting efforts into preserving still existing carbon stocks may be more successful than attempts to increase sequestration rates in such high‐organic mountain grassland soils.  相似文献   

5.
6.
Temperatures in mountain areas are increasing at a higher rate than the Northern Hemisphere land average, but how fauna may respond, in particular in terms of phenology, remains poorly understood. The aim of this study was to assess how elevation could modify the relationships between climate variability (air temperature and snow melt‐out date), the timing of plant phenology and egg‐laying date of the coal tit (Periparus ater). We collected 9 years (2011–2019) of data on egg‐laying date, spring air temperature, snow melt‐out date, and larch budburst date at two elevations (~1,300 m and ~1,900 m asl) on a slope located in the Mont‐Blanc Massif in the French Alps. We found that at low elevation, larch budburst date had a direct influence on egg‐laying date, while at high‐altitude snow melt‐out date was the limiting factor. At both elevations, air temperature had a similar effect on egg‐laying date, but was a poorer predictor than larch budburst or snowmelt date. Our results shed light on proximate drivers of breeding phenology responses to interannual climate variability in mountain areas and suggest that factors directly influencing species phenology vary at different elevations. Predicting the future responses of species in a climate change context will require testing the transferability of models and accounting for nonstationary relationships between environmental predictors and the timing of phenological events.  相似文献   

7.
The microscale variation and spatial genetic structure of the alpine plant species Primula minima L. was analysed using AFLPs. AFLP analysis based on three primer combinations and 123 fragments revealed no identical genotypes among the 86 studied samples from a 300 × 300 cm plot. Variation within the study plot was high: Nei's gene diversity was 0.22, Shannon's information index 0.33 and the percentage of polymorphic bands was 60.9. Cluster analysis revealed four main groups of genetically similar individuals and mapping these individuals resulted in a clear spatial pattern, with samples from the same group often located close together. The observed microscale structure was corroborated using a Mantel test, which revealed significant correlation of genetic and spatial distances, and by the results of a spatial autocorrelation analysis that indicated a high level of similarity between adjacent samples. An analysis of molecular variance revealed clear differentiation (18%) between the spatial groups. Overall gene flow within the plot was 1.11 and ranged from 0.33 between the spatially most distant groups to 2.33 between directly neighbouring groups. The extraordinary level of diversity detected in this study indicates an unexpectedly strong relevance of reproduction by seed for the species P. minima in alpine grasslands. The strong microscale variation suggests, however, that there is limited dispersal of seeds. Clonal reproduction is of subsidiary importance to sexual reproduction and seems to occur only over very small distances.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 549–556.  相似文献   

8.
9.
Establishing secure tenure is widely recognized as a fundamental component of sustainable forest management. Policy-makers generally prefer privatization to achieve these ends, although common property institutions may also be appropriate. But if common property tenure is insecure and fails to control exploitation, theory predicts that private tenure should lead to better forest conditions. In this case study of a western Honduras community, forest mensuration data were collected from four private forests and two relatively open access common property forests. Statistical analyses failed to find consistent, significant differences in vegetation structure or soils related to tenure. Notable contrasts between forests reflected historical conditions and owner preferences. Neither form of tenure appeared to emphasize concerns for sustainable management, and ongoing processes of change constrained the possibility for limiting common property forest exploitation. The study adds to others which show that the outcomes of private or common property tenure relate substantially to the socioeconomic, political, and ecological context.  相似文献   

10.
Why do Solomon Islands’ villagers continue to engage with large scale logging projects by foreign companies when they have decades of experience of the disadvantages of such deals? This paper explores village level narratives of equality surrounding a logging dispute in a village on Kolombangara Island in the Western Province of the Solomon Islands. Drawing on empirical evidence I seek to understand firstly, why villagers continue to engage with logging companies, and secondly, why seemingly viable and financially attractive alternative forestry projects may not be taken up. Additionally, I examine legal recognition of a local conservation Non‐Government organisation as an environmental ‘stakeholder’, with an accepted interest in customary land as distinct from the categorisation of ‘landowners’. I conclude that village communities may continue to engage with foreign logging companies, despite their clear knowledge of the disadvantages of such projects, partly as a means of maintaining some measure of social equality in the village.  相似文献   

11.
Information about mosquito ecology in the high mountain ecosystems of the Neotropical region is sparse. In general, few genera and species have been reported in these ecosystems and there is no information available on habitats and the mosquitoes occupying them. In the present study, specimens collected from NW Colombia in HME were grouped using larval habitat data via an Operational Taxonomic Unit (OTU) determination. A total of 719 mosquitoes was analyzed belonging to 44 OTUs. The analysis considered habitat features and clustered the specimens into six groups from A‐F. Five of these included species from different genera, suggesting common habitat requirements. Group E with four genera, seven subgenera, and six species occupied the highest areas (above 3,000 m), whereas three groups (B, D, F) were detected at lower altitudes (1,960–2,002 m). Bromeliads were the most common larval habitat, with 47% (335/719) of the specimens; five genera, six subgenera, and eight species were identified and classified into 66% (29/44) of the OTUs. This work showed some similarities to the habitat requirements and provides a grouping system that constitutes an important baseline for the classification of mosquito fauna from high mountain ecosystems according to altitude and larval habitat.  相似文献   

12.
Aims To assess the potential distribution of an obligate seeder and active pyrophyte, Cistus salviifolius, a vulnerable species in the Swiss Red List; to derive scenarios by changing the fire return interval; and to discuss the results from a conservation perspective. A more general aim is to assess the impact of fire as a natural factor influencing the vegetation of the southern slopes of the Alps. Location Alps, southern Switzerland. Methods Presence–absence data to fit the model were obtained from the most recent field mapping of C. salviifolius. The quantitative environmental predictors used in this study include topographic, climatic and disturbance (fire) predictors. Models were fitted by logistic regression and evaluated by jackknife and bootstrap approaches. Changes in fire regime were simulated by increasing the time‐return interval of fire (simulating longer periods without fire). Two scenarios were considered: no fire in the past 15 years; or in the past 35 years. Results Rock cover, slope, topographic position, potential evapotranspiration and time elapsed since the last fire were selected in the final model. The Nagelkerke R2 of the model for C. salviifolius was 0.57 and the Jackknife area under the curve evaluation was 0.89. The bootstrap evaluation revealed model robustness. By increasing the return interval of fire by either up to 15 years, or 35 years, the modelled C. salviifolius population declined by 30–40%, respectively. Main conclusions Although fire plays a significant role, topography and rock cover appear to be the most important predictors, suggesting that the distribution of C. salviifolius in the southern Swiss Alps is closely related to the availability of supposedly competition‐free sites, such as emerging bedrock, ridge locations or steep slopes. Fire is more likely to play a secondary role in allowing C. salviifolius to extend its occurrence temporarily, by increasing germination rates and reducing the competition from surrounding vegetation. To maintain a viable dormant seed bank for C. salviifolius, conservation managers should consider carrying out vegetation clearing and managing wild fire propagation to reduce competition and ensure sufficient recruitment for this species.  相似文献   

13.
Aim To determine how the distribution and cover of different vegetation types are affected by physical factors and livestock in a mountain range with a long evolutionary history of grazing. Location Upper vegetation belt of the Córdoba mountains (1700–2800 m a.s.l., 31º34′ S, 64º50′ W) in central Argentina. Methods Using GIS, we analysed the relationships of plant cover types to physical features (physiography and topography) and indicators of accumulated livestock pressure (distance to human settlements and roads) through multinomial logistic regression. We predicted a present vegetation map which was validated with a real map. We then constructed two maps simulating minimum and maximum values of accumulated livestock pressure for the whole area. Map comparisons allowed evaluation of the possible influence of livestock, both in extension and intensity. Results Both physical features and livestock pressure influenced the occurrence of vegetation units. The overall accuracy of the predicted map at the pixel level was low (26%) indicating low habitat specificity of the vegetation units. We suggest that some part of the unaccounted for variance was due to livestock pressure patterns that were not fully captured by our indicators. Our models proved adequate for predicting the total percentages of vegetation units at coarser scales. The extrapolations showed that under a history of low livestock pressure, such as in sites far away from human settlements and roads, the area would be dominated by woodlands, tussock grasslands and natural rock outcrops. Under a history of heavy livestock pressure, in turn, rock exposed by erosion, tussock grasslands and natural rock outcrops would dominate. Main conclusions Vegetation units showed low habitat specificity, and were associated with accumulated livestock pressure, indicating that livestock and its associated activities are important factors structuring the landscape and have important consequences for the integrity of the ecosystem. Results suggest that although this system evolved with large herbivores, it has experienced irreversible degradation processes, and intensification of current domestic livestock pressure is likely to lead to even more land degradation.  相似文献   

14.
Meteorological and climatic processes in mountain regions play a key role in many environmental systems, in particular the quantity and quality of water that influences both aquatic ecosystems and economic systems often far beyond the boundaries of the mountains themselves. This paper will provide a general overview of some of the particular characteristics of mountain weather and climate, to highlight some of the unique atmospheric features that are associated with regions of complex topography. The second part of the paper will focus upon characteristics of climate and climatic change in the European Alps, a region with a wealth of high quality data that allows an assessment on how climate and dependent environmental systems have evolved in the course of the 20th century and how alpine climate may undergo further changes to “global warming” in the 21st century, as the atmosphere responds to increasing levels of greenhouse gases that are expected in coming decades.  相似文献   

15.
山体绿地是喀斯特山地城市内典型的城市绿地景观类型,其对于改善城市生态环境、提升喀斯特山地城市生态服务功能具有重要作用.以黔中典型喀斯特山地城市安顺市为研究对象,运用2011年和2016年两期热红外遥感影像和城市景观结构空间数据,在反演分析城市热岛效应及其强度时空分布特征的基础上,运用冷热点分析剖析了山体绿地与城市热岛效...  相似文献   

16.
罗万云  钟方雷  王光耀 《生态学报》2020,40(8):2636-2646
农户是生态治理政策的"践行者",也是政策效果的"检验者",其满意度对政策的可持续实施至关重要。基于甘肃省沙化土地封禁保护区周边1417份农户调查数据,运用帕累托分析方法和Ordered Logit模型,就沙化土地封禁保护政策的农户满意度及影响因素展开分析。研究结果表明:沙化土地封禁保护政策的农户总体满意度介于"一般"和"满意"之间,均值为3.67("非常满意"为5);外部影响因素分析表明,政策实施效果中风沙危害削减程度、荒漠化逆转程度、家庭收入提升状况、破坏行为减少程度与农户满意度之间存在正相关性;生态变化感知中的风沙强度、水资源紧缺程度对农户满意度起负向作用,降雨(雪)次数变化、荒漠植被盖度对农户满意度起正向作用。农户内部自身因素中,家庭人均收入、耕地、政府补贴、性别、教育程度、健康状况与农户满意度均通过显著性检验。控制变量因素中地方政府治理重视程度与农户满意度呈正相关性,平原地区的农户满意度明显高于山区。从政策角度看,农户生计改善是未来沙化土地封禁保护政策成功实施的关键保障。  相似文献   

17.
Background: Gradients in the amounts and duration of snowpack and resulting soil moisture gradients have been associated with different plant communities across alpine landscapes.

Aims: The extent to which snow additions could alter plant community structure, both alone and in combination with nitrogen (N) and phosphorus (P) additions, provided an empirical assessment of the strength of these variables on structuring the plant communities of the alpine tundra at Niwot Ridge, Colorado Front Range.

Methods: A long-term snow fence was used to study vegetation changes in responses to snowpack, both alone and in conjunction with nutrient amendments, in plots established in dry and moist meadow communities in the alpine belt. Species richness, diversity, evenness and dissimilarity were evaluated after 20 years of treatments.

Results: Snow additions, alone, reduced species richness and altered species composition in dry meadow plots, but not in moist meadow; more plant species were found in the snow-impacted areas than in nearby controls. Changes in plant community structure to N and N + P additions were influenced by snow additions. Above-ground plant productivity in plots not naturally affected by snow accumulation was not increased, and the positive responses of plant species to nutrient additions were reduced by snow addition. Plant species showed individualistic responses to changes in snow and nutrients, and indirect evidence suggested that competitive interactions mediated responses. A Permanova analysis demonstrated that community dissimilarity was affected by snow, N, and P additions, but with these responses differing by community type for snow and N. Snow influenced community patterns generated by N, and finally, the communities impacted by N + P were significantly different than those affected by the individual nutrients.

Conclusions: These results show that changes in snow cover over a 20-year interval produce measureable changes in community composition that concurrently influence and are influenced by soil nutrient availability. Dry meadow communities exhibit more sensitivity to increases in snow cover whereas moist meadow communities appear more sensitive to N enrichment. This study shows that the dynamics of multiple limiting resources influence both the productivity and composition of alpine plant communities, with, species, life form, and functional traits mediating these responses.  相似文献   

18.
Constructing a Wild Mushroom Panopticon: The Extension of Nation-State Control over the Forest Understory in Oregon, USA. For most of the 20th century, wild mushrooms on national forests in the United States fell under a de facto open-access management regime. As consumer demand for wild mushrooms increased, a nation-state wild mushroom management regime based on the use of disciplinary power emerged on many national forests in the Pacific Northwest region. Data from an ethnographic study conducted during the late 1990s illustrate how the simultaneous application of three core surveillance technologies—categorization, monitoring, and tracking, and the creation of a panopticon surveillance system—enabled the Forest Service to enforce nation-state claims to wild mushrooms. The data indicate that many pickers are unsupportive of the new regulatory system because it has transformed what was once their living space into a working place. Pickers also point out that the system does little to protect or enhance the growth of wild mushrooms. The study supports conclusions from previous studies that disciplinary power techniques play a critical role in the capacity of modern states to extend their control over mobile populations and natural resources.  相似文献   

19.

Aim

Human activity is known to greatly influence species occurrences. In forest ecosystems, biodiversity is often believed to be influenced by two habitat characteristics: (1) forest continuity, related to a minimum length of time in a wooded state since a threshold date; and (2) stand maturity, related to the availability of late‐developmental‐forest attributes. In a context of ongoing global biodiversity loss, qualifying the effect of past and present human activity on forest ecosystems while taking into account variations in abiotic factors is of primary importance for conservation.

Location

Temperate mountain forests in the Northern Alps.

Method

Based upon a sampling design crossing forest continuity (ancient vs. Recent) and stand maturity (mature vs. overmature), and while controlling for the effect of two major environmental factors, soil and climate, we explored the individual response of saproxylic beetle, springtail, herbaceous plant and epiphytic macrolichen species to past and present human activity.

Results

Forest continuity influenced the occurrence of relatively few species, indicating that past land use had almost no legacy effect on the species occurring in the study forests today. In contrast, stand maturity had an overall positive effect on species occurrences. However, our results showed that species occurrences were more obviously influenced by abiotic conditions. Indeed, beyond the effect of continuity and maturity factors, the probability of presence of numerous species was best explained by climate and soil.

Main conclusions

Overall, we show that species occurrence was more influenced by stand maturity than by forest continuity, but also that site‐specific characteristics were of great importance in explaining the probability of presence for numerous species. In the ecological context of alpine forests, these findings emphasize the need to better control for climatic and edaphic conditions in order to (1) improve accuracy in predicting species occurrence and (2) better design areas of conservation interest.
  相似文献   

20.
Direct impacts of human land use and indirect impacts of anthropogenic climate change may alter land cover and associated ecosystem function, affecting ecological goods and services. Considerable work has been done to identify long‐term global trends in vegetation greenness, which is associated with primary productivity, using remote sensing. Trend analysis of satellite observations is subject to error, and ecosystem change can be confused with interannual variability. However, the relative trends of land cover classes may hold clues about differential ecosystem response to environmental forcing. Our aim was to identify phenological variability and 10‐year trends for the major land cover classes in the Great Basin. This case study involved two steps: a regional, phenology‐based land cover classification and an identification of phenological variability and 10‐year trends stratified by land cover class. The analysis used a 10‐year time series of Advanced Very High Resolution Radiometer satellite data to assess regional scale land cover variability and identify change. The phenology‐based regional classification was more detailed and accurate than national or global products. Phenological variability over the 10‐year period was high, with substantial shifts in timing of start of season of up to 9 weeks. The mean long‐term trends of montane land cover classes were significantly different from valley land cover classes due to a poor response of montane shrubland and pinyon‐juniper woodland to the early 1990s drought. The differential response during the 1990s suggests that valley ecosystems may be more resilient and montane ecosystems more susceptible to prolonged drought. This type of regional‐scale land cover analysis is necessary to characterize current patterns of land cover phenology, distinguish between anthropogenically driven land cover change and interannual variability, and identify ecosystems potentially susceptible to regional and global change.  相似文献   

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