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Highest Altitudes (highest + altitude)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Volatile components of Thymus vulgaris L. from wild-growing and cultivated plants in Jordan

FLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2007
M. Hudaib
Abstract The composition of the essential oil hydrodistilled from the aerial parts of Thymus vulgaris L. grown in Jordan has been determined by GC and GC,MS. Variations in oil composition and yield between cultivated and wild-growing plants collected from different localities, at different altitudes, have been also evaluated. Higher oil yields were observed in plants growing wild (3.7,5.6% of dried material) than in cultivated plants (1.1,2.0%), and those collected from the Mshaqar region, in the middle of Jordan and at the highest altitude, were the richest in oil (,5.4%). Generally, the oil was characterized by marked levels of phenolic monoterpenoids (mainly thymol and carvacrol) in the range 70.8,89.0%. High levels of the monoterpenoid hydrocarbons p -cymene (3.4,8.2%) and , -terpinene (1.6,7.7%) were also observed. Other major components were 1,8-cineole (up to 2.1%), , -thujone (up to 1.2%), camphor (up to 1.1%) and , -caryophyllene (0.2,2.8%). With the exception of plants growing wild in the Ramtha region, in the far north of Jordan, carvacrol was found as the principal phenol of all other oils (50.6,86.1%) and was dominant (>85%) in wild plant oils. The oil from Ramtha was characterized by the highest level of thymol (,63.8%) as the dominant phenol and was most abundant in p -cymene (8.2%), 1,8-cineole (2.1%) and , -terpinene (7.7%). In addition to assigning carvacrol or thymol chemotypes to the plant, the high content of active monoterpenoid phenols strongly suggests a potential use of Jordanian thyme oil in cough products and antimicrobial,herbal drug combinations. Copyright © 2007 John Wiley & Sons, Ltd. [source]

A global change-induced biome shift in the Montseny mountains (NE Spain)

GLOBAL CHANGE BIOLOGY, Issue 2 2003
Josep Peñuelas
Abstract Shifts in plant species and biome distribution in response to warming have been described in past climate changes. However, reported evidence of such shifts under current climate change is still scarce. By comparing current and 1945 vegetation distribution in the Montseny mountains (Catalonia, NE Spain), we report here a progressive replacement of cold-temperate ecosystems by Mediterranean ecosystems. Beech (Fagus sylvatica) forest has shifted altitudinally upwards by ca. 70 m at the highest altitudes (1600,1700 m). Both the beech forests and the heather (Calluna vulgaris) heathlands are being replaced by holm oak (Quercus ilex) forest at medium altitudes (800,1400 m). This beech replacement has been observed to occur through a progressive isolation and degradation of beech stands. In ,isolated' (small and surrounded by holm oaks) beech stands, beech trees are 30% more defoliated, beech recruitment is 41% lower, and holm oak recruitment is three times higher than in ,continental' (large and continuous) beech stands. The progressively warmer conditions, complemented by the land use changes (mainly the cessation of traditional land management) are the apparent causes, providing a paradigmatic example of global change affecting distributions of plant species and biomes. [source]

Low-temperature resistance in Polylepis tarapacana, a tree growing at the highest altitudes in the world

PLANT CELL & ENVIRONMENT, Issue 3 2001
F. Rada
ABSTRACT The Polylepis tarapacana forests found in Bolivia are unique with respect to their altitudinal distribution (4200,5200 m). Given the extreme environmental conditions that characterize these altitudes, this species has to rely on distinct mechanisms to survive stressful temperatures. The purpose of this study was to determine low-temperature resistance mechanisms in P. tarapacana. Tissue was sampled for carbohydrate and proline contents and micro-climatic measurements were made at two altitudes, 4300 and 4850 m, during both the dry cold and wet warm seasons. Supercooling capacity (,3 to ,6 °C for the cold dry and ,7 to ,9 °C for the wet warm season) and injury temperatures (,18 to ,23 °C for both seasons), determined in the laboratory, indicate that P. tarapacana is a frost-tolerant species. On the other hand, an increase in supercooling capacity, as the result of significant increase in total soluble sugar and proline contents, occurs during the wet warm season as a consequence of higher metabolic activity. Hence, P. tarapacana, a frost-tolerant species during the colder unfavourable season, is able to avoid freezing during the more favourable season when minimum night-time temperatures are not as extreme. [source]

Are Ecosystem Composition, Structure, and Functional Status Related to Restoration Success?

RESTORATION ECOLOGY, Issue 2 2006
A Test from Semiarid Mediterranean Steppes
Abstract Theoretical models emphasize the importance of considering the composition, structure, and functioning of an ecosystem when restoring it. However, there is a lack of empirical studies evaluating how these ecosystem attributes are linked, if any, to the success of restoration actions. We conducted experimental plantings of the native late-successional shrub Pistacia lentiscus in 10 semiarid steppes located in southeast Spain and related seedling survival rates to measures of ecosystem structure and composition and to surrogates of ecosystem functioning. Seedling survival widely differed among the studied steppes and 17 months after planting ranged from 0 to 89%. Mortality occurred mostly during the first summer in the field, coinciding with a strong drought lasting 3 months. Survival was lower in the steppes located at the highest altitudes and with the highest values of total plant cover, species richness, shrub cover, and functionality. Seedling survival was mainly controlled by abiotic conditions and showed a negative relationship with some of the surrogates of ecosystem functioning evaluated. Our results suggest, but cannot confirm, that the functional status of the ecosystem may not limit the early stages of establishment of P. lentiscus in semiarid steppes and that abiotic conditions play an overriding role in this process. If true, its introduction in these areas would not necessarily need a previous phase of recovery of ecosystem functions like nutrient cycling and infiltration. [source]