نتایج جستجو برای: shrub canopy
تعداد نتایج: 19636 فیلتر نتایج به سال:
remote sensing and aerial photographs are used to produce medium to small scale images. however, for detailed information especially to estimate rangeland vegetation canopy cover there is a need to larger scale images. it is therefore necessary to study the technical applicability of different devices such as short range light airplanes, kites, gliders and balloons. in this research, we focused...
Seventeen herb, shrub and tree species of commercial and ecological importance in southern Africa were exposed at one location to ultraviolet-B (UV-B, 280-315 nm) radiation approx. 35 % above clear-sky background (control). The aims were to assess how UV-B affects canopy area, dry mass, and some biochemical and morphological properties of leaves, and to investigate whether differences between s...
This study tested the applicability of Island Biogeographic Theory to arthropod assemblages on ‘islands’ of creosotebush (Larrea tridentata) across a desert shrubland-grassland ecotone in central New Mexico, U.S.A. We assumed that herbivorous arthropod taxa that specialize on creosotebush view these shrubs as ‘islands’ of suitable habitat in a ‘sea’ of grassland, and used the Island Biogeograph...
Lake sediments from arcto-boreal regions commonly contain abundant Betula pollen. However, palaeoenvironmental interpretations of Betula pollen are often ambiguous because of the lack of reliable morphological features to distinguish among ecologically distinct Betula species in western North America. We measured the grain diameters and pore depths of pollen from three tree-birch species (B. pa...
The worldwide phenomenon of shrub encroachment in grass-dominated dryland ecosystems is commonly associated with desertification. Studies of the purported desertification effects associated with shrub encroachment are often restricted to relatively few study areas, and document a narrow range of possible impacts upon biota and ecosystem processes. We conducted a study in degraded Mediterranean ...
Indirect ecological effects are a common feature of ecological systems, arising when one species affects interactions among two or more other species. We examined how browsing by white-tailed deer (Odocoileus virginianus) indirectly affected the abundance and composition of a web-building spider guild through their effects on the structure of the ground and shrub layers of northern hardwood for...
The establishment of invasive alien species in varied habitats across the world is now recognized as a genuine threat to the preservation of biodiversity. Specifically, plant invasions in understory tropical forests are detrimental to the persistence of healthy ecosystems. Monitoring such invasions using Very High Resolution (VHR) satellite remote sensing has been shown to be valuable in design...
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