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Intermediate Altitudes (intermediate + altitude)
Selected AbstractsSoil conservation in Polylepis mountain forests of Central Argentina: Is livestock reducing our natural capital?AUSTRAL ECOLOGY, Issue 4 2010DANIEL RENISON Abstract Mountain forests and their soils provide ecological services such as maintenance of biodiversity, provision of clean water, carbon capture and forage for livestock rearing, which is one of the principal economic activities in mountain areas. However, surprisingly little is known about livestock impact in South American mountain forest soils. With the aim of understanding how livestock and topography influence patterns of forest cover, soil compaction, soil loss and soil chemical properties, we analysed these parameters in 100 Polylepis australis woodland plots situated in the humid subtropical mountains of Central Argentina. We used distance from the nearest ranch as an objective index of historical livestock impact and measured standard topographic variables. Our main results reveal that distance from ranch in all cases partly explains tree canopy cover, soil loss, soil compaction and soil chemical properties; suggesting a strong negative effect of livestock. Intermediate altitudes had more tree canopy cover, while landscape roughness , a measure of the variability in slope inclination and aspect , was negatively associated to soil impedance and acidity, and positively associated to soil organic matter content. Finally, flatter areas were more acid. We conclude that livestock has had a substantial influence on forest soil degradation in the Mountains of Central Argentina and possibly other similar South American mountains. Soil degradation should be incorporated into decision making when considering long-term forest sustainability, or when taking into account retaining livestock for biodiversity conservation reasons. Where soil loss and degradation are ongoing, we recommend drastic reductions in livestock density. [source] Global patterns of genetic variation in plant species along vertical and horizontal gradients on mountainsGLOBAL ECOLOGY, Issue 2 2008Takafumi Ohsawa ABSTRACT Aim To understand global patterns of genetic variation in plant species on mountains and to consider the significance of mountains for the genetic structure and evolution of plant species. Location Global. Methods We review published studies. Results Genetic diversity within populations can vary along altitudinal gradients in one of four patterns. Eleven of 42 cited studies (26% of the total) found that populations at intermediate altitudes have greater diversity than populations at lower and higher altitudes. This is because the geographically central populations are under optimal environmental conditions, whereas the peripheral populations are in suboptimal situations. The second pattern, indicating that higher populations have less diversity than lower populations, was found in eight studies (19%). The third pattern, indicating that lower populations have lower diversity than higher populations, was found in 10 studies (24%). In 12 studies (29%), the intrapopulation genetic variation was found to be unaffected by altitude. Evidence of altitudinal differentiation was found in more than half of these studies, based on measurements of a range of variables including genome size, number of chromosomes or a range of loci using molecular markers. Furthermore, great variation has been found in phenotypes among populations at different altitudes in situ and in common garden experiments, even in cases where there was no associated variation in molecular composition. Mountains can be genetic barriers for species that are distributed at low elevations, but they can also provide pathways for species that occupy high-elevation habitats. [Correction added after publication 9 October 2007: ,less diversity' changed to ,greater diversity' in the second sentence of the Results section of the Abstract] Main conclusions Genetic diversity within populations can vary along altitudinal gradients as a result of several factors. The results highlight the importance of phenotypic examinations in detecting altitudinal differences. The influence of mountain ridges on genetic differentiation varies depending, inter alia, on the elevation at which the species occurs. Based on these findings, zoning by altitudes or ridges would be helpful for the conservation of tree populations with the onset of global warming. [source] Genetic differentiation and natural hybridization between the Sardinian endemic Maniola nurag and the European Maniola jurtinaJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2007A. GRILL Abstract The Mediterranean island of Sardinia is known for its multitude of unique genetic lineages. We view one of them in a larger phylogeographic context. The endemic Sardinian Meadow Brown butterfly, Maniola nurag, is restricted to the mountainous areas of the island, whereas its widespread close relative, Maniola jurtina, also occurs on the coast. At intermediate altitudes the species' distributions overlap. There, a number of individuals exhibit phenotypic characteristics intermediate between the two species. We examined patterns of intra- and interpopulation variation in 10 M. nurag populations from Sardinia and 16 M. jurtina populations from Sardinia and continental Europe, as well as 17 intermediate individuals, sampled in 1999,2002, by means of allozyme markers, combining it with a morphometric analysis based on 18 wing-characters of 52 males. At the 15 loci studied (aldolase, aat-1, aat-2, g6pdh, gpd, idh-1, idh-2, mdh-1, mdh-2, mpi, me, leu-ala, pgi, pgm, and 6pgdh), 76 different alleles were detected, 63 of which were shared by M. nurag and M. jurtina. None of the loci was found to be alternatively fixed between the two species. In that respect, this study testifies to the difficulties that may arise when trying to identify hybrids from genotypic data. Levels of genetic variation in island populations (M. jurtina: HO = 0.137,0.189; M. nurag: HO = 0.141,0.270) were comparable to those of mainland M. jurtina (HO = 0.141,0.236). A Bayesian admixture analysis supported the hypothesis of mixed (hybrid) ancestry of individuals occurring at intermediate altitudes. Similarly, neighbour-joining and unweighted pair-group method with arithmetic averaging (UPGMA) analyses, as well as morphometrics hinted at the existence of a Maniola -hybrid zone in Sardinia at intermediate altitudes. We discuss the results in the light of the phylogeography of other Sardinian taxa with the aim to reach a general understanding of the biogeographic history of this island's endemic species. [source] Palaeoindian occupation of the Atacama Desert, northern Chile,JOURNAL OF QUATERNARY SCIENCE, Issue 7-8 2005Martin Grosjean Abstract Palaeoindian occupation of the Atacama Desert in northern Chile has been found between 12,600 and 10,200,cal.,yr,BP. The new site at Salar Punta Negra (24°28,S/60°53,W/2976,m) includes about 1000 classifiable, mostly unifacial artefacts and, uniquely, three different diagnostic types of early projectile points. Two of the Lateglacial/early Holocene projectile types have wide distribution and are known from different geographical areas in South America: the Palaeoindian ,Fell' fish-tail point mainly from the southern cone of South America, and the triangular ,Tuina' points typical of the Puna of the south-central Andes in northern Chile and northwestern Argentina. In addition, we found a third type, a stemmed point typical for the Salar Punta Negra. Filling a large geographical gap of ,Fell' occupation, the site at Salar Punta Negra provides evidence for generally much higher mobility and diversity of early cultures, and supports an Andean-Pacific route for early human exploration of South America to the south through the desert at intermediate altitudes. Contemporaneous high-amplitude climatic changes were fundamental preconditions to provide adequate environments and habitats, and to make Palaeoindian hunting-gathering occupation possible in the Atacama Desert. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||