982 resultados para Mountain railroads.


Relevância:

20.00% 20.00%

Publicador:

Resumo:

This study aimed to describe patterns of diversity of Baetidae (Ephemeroptera) at the ommunity and population levels within the Montseny Mountain range (North-East Iberian Peninsula). We studied both the distribution of 4 species of baetids in 20 sites among three catchments along the altitudinal gradient (350-1700 masl); and the genetic diversity of the mtDNA cytochrome c oxidase subunit I (cox1) gene of the two common species Baetis alpinus and Baetis rhodani. We found a gradual replacement of the dominant species along the altitudinal gradient. Baetis alpinus inhabited sites at high-altitudes, and this species was replaced by B. rhodani when the altitude decreased. Baetis melanonyx and Alainites muticus attained low abundance at all river sections, and no clear altitudinal trend appeared. Our hypothesis at the population level was that genetic structuring is associated with geographic distance and limited by drainage boundaries among the three studied catchments because of the short-time dispersion of adults. Unexpectedly, analyses of molecular variance (AMOVA) and isolation-bydistance (IBD) showed genetic diversity was unstructured by distance for both species, which may be explained by the relatively short spatial scale studied and small topographic barriers among the three catchments. The Generalized Mixed Yule-Coalescent (GMYC) model showed that B. rhodani had two differentiated genetic lineages that co-occurred in all sites. Overall, diversity of baetids was structured at the community level along the altitudinal gradient, whereas it was unstructured at the population level within the Montseny Mountain range.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This study aimed to describe patterns of diversity of Baetidae (Ephemeroptera) at the ommunity and population levels within the Montseny Mountain range (North-East Iberian Peninsula). We studied both the distribution of 4 species of baetids in 20 sites among three catchments along the altitudinal gradient (350-1700 masl); and the genetic diversity of the mtDNA cytochrome c oxidase subunit I (cox1) gene of the two common species Baetis alpinus and Baetis rhodani. We found a gradual replacement of the dominant species along the altitudinal gradient. Baetis alpinus inhabited sites at high-altitudes, and this species was replaced by B. rhodani when the altitude decreased. Baetis melanonyx and Alainites muticus attained low abundance at all river sections, and no clear altitudinal trend appeared. Our hypothesis at the population level was that genetic structuring is associated with geographic distance and limited by drainage boundaries among the three studied catchments because of the short-time dispersion of adults. Unexpectedly, analyses of molecular variance (AMOVA) and isolation-bydistance (IBD) showed genetic diversity was unstructured by distance for both species, which may be explained by the relatively short spatial scale studied and small topographic barriers among the three catchments. The Generalized Mixed Yule-Coalescent (GMYC) model showed that B. rhodani had two differentiated genetic lineages that co-occurred in all sites. Overall, diversity of baetids was structured at the community level along the altitudinal gradient, whereas it was unstructured at the population level within the Montseny Mountain range.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Poster at Open Repositories 2014, Helsinki, Finland, June 9-13, 2014

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Espinhaço and Mantiqueira are two mountain ranges of great importance in Brazil. In the uppermost parts of these areas, unique ecosystems occur, generally associated with rock outcrops, they are collectively called High Altitude Rocky Complexes. These environments show distinct soil and biota characteristics in relation to the surrounding biome. The soils are generally shallow, coarse textured, with high Al3+ and varying amounts of organic matter. Entisols, Inceptsols and Histosols are dominant, directly associated with the rock outcrops, and forming a complex mosaic of soils. Some of these soils are endemic, based on peculiar conditions of parent materials, topography and vegetation, and this pedodiversity is important for detecting unique and endangered soils. In these soils, organic matter is highly humified, with a great amount of soluble forms and conspicuous presence of charcoal. Spodic horizons and dark water rivers are typically associated with quartzite and quartzite outcrops, formed by illuviation of organic compounds, being less common in granitic rocks. The very low nutrient content of these soils and other environmental limitations required the development of specific physiological and morphological plant adaptations. Most high altitude environments are unstable under current climatic conditions, and anthropic interventions may be accelerating this process. Detailed soil surveys are necessary for a better understanding of the role of these soils in ecological processes and for the development of adequate conservation policies.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The high species richness and diversity found in tropical montane habitats are often related to: 1) an effect of climatic and geological history on biotic evolution; 2) the various environmental impacts on species adaptation mechanisms; and 3) the continuous dispersal of fauna and flora in time. However, little is known about how these factors shaped species richness in Brazilian mountains. Official documents on biodiversity in Brazil make no explicit reference to mountains, even though there is a mountain work programme of the Convention on Biological Diversity, which Brazil is a signatory of. This paper discusses the importance of mountain ecosystems in Brazil to show the urgent need to include mountain biodiversity in the national agenda of biodiversity research and conservation.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Kartta kuuluu A. E. Nordenskiöldin kokoelmaan

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The description of the image reads "No. 65 - The great ice mountain and American Falls, Niagara".

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Iron Mountain Route Railway schedule: the great through line St. Louis, Arkansas and Texas to the Hot Springs of Arkansas.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

An important feature of maintaining the agricultural stability in millennia-old mountain oases of northern Oman is the temporary abandonment of terraces. To analyse the effects of a fallow period on soil microbial performance, i.e. microbial activity and microbial biomass, samples of eight terrace soils abandoned for different periods were collected in situ, assigned to four fallow age classes and incubated for 30 days in the laboratory after rewetting. The younger fallow age classes of 1 and 5 years were based on the records of the farmers’ recollections, the two older fallow age classes of 10–20 and 25–60 years according to the increase in the D -to- L ratio of valine and leucine enantiomers. The increase in these two ratios was in agreement with that of the D -to- L ratio of lysine. The strongest relationship was observed between the increase in the D -to- L ratio of lysine and the decrease in soil microbial biomass C. However, the most stringent coherence between the increase in fallow age and soil properties was revealed by the decreases in cumulative respiration and net N mineralisation rates with decreasing availability of substrate to soil microorganisms. During the 30-day incubation following rewetting, relative changes in microbial activity (respiration and net N mineralisation) and microbial biomass (C and N)indices were similar in the eight terrace soils on a fallow age-class-specific level, indicating that the same basic processes occurred in all of the sandy terrace soils investigated.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

For millennia oasis agriculture has been the backbone of rural livelihood in the desertic Sultanate of Oman. However, little is known about the functioning of these oasis systems, in particular with respect to the C turnover. The objective was to determine the effects of crop, i.e. alfalfa, wheat and bare fallow on the CO2 evolution rate during an irrigation cycle in relation to changes in soil water content and soil temperature. The gravimetric soil water content decreased from initially 24% to approximately 16% within 7 days after irrigation. The mean CO2 evolution rates increased significantly in the order fallow (27.4 mg C m^−2 h^−1) < wheat (45.5 mg C m^−2 h^−1) < alfalfa (97.5 mg C m^−2 h^−1). It can be calculated from these data that the CO2 evolution rate of the alfalfa root system was nearly four times higher than the corresponding rate in the wheat root system. The decline in CO2 evolution rate, especially during the first 4 days after irrigation, was significantly related to the decline in the gravimetric water content, with r = 0.70. CO2 evolution rate and soil temperature at 5 cm depth were negatively correlated (r = -0.56,n = 261) due to increasing soil temperature with decreasing gravimetric water content.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

To unravel the settlement history of oases in northern Oman, data on topography, the agricultural setting, water and soil parameters and archaeological findings were collected in the Wadi Bani Awf with its head oasis Balad Seet. Data collection lasted from April 2000 to April 2003 and was based on the establishment of a 3D-georeferenced map of the oasis comprising all its major infrastructural and agronomic features. At today's Balad Seet, a total of 8.8 ha are planted to 2,800 date palms and 4.6 ha are divided into 385 small fields dedicated to wheat, barley, sorghum, oats, alfalfa, garlic, onion, lime and banana. Radiocarbon dating of charcoal in the lower part of the main terrace system determined its age to 911 ± 43 years. Monthly flow measurements of four major aflaj systems showed a total maximum flow of 32 m^3 h^-1 with the largest falaj contributing 78% of the total flow. During drought periods, average water flow decreased by 3% per month, however, with significant differences between the spring systems. The analysis of the tritium/^3helium ratio in the water led to an estimated water age of up to 10 years. In combination with the flow data, this provided insights into the elasticity of the spring flow over time. The use of the natural resources of the Wadi Bani Awf by a pastoral population started probably in the early 3rd millennium BC. The first permanent settlement might have been established at Balad Seet during the first part of the 1st millennium BC. Presumably it was initiated by settlers from al-Hamra, a village at the southern foot of the Hajar mountains. Given an abundant und stable flow of springs, even in periods of drought, the construction of Balad Seet's first irrigation systems may have occurred at this early time. The combination of topographic, agricultural, hydro-pedological and archaeological data allowed assessment of the carrying capacity of this oasis over the three millennia of its likely existence. The changing scarcity of land and water and the eventual optimisation of their use by different aflaj constructions have been major driving forces for the development and apparent relativeley stable existence of this oasis.