90 research outputs found
Bendix Kansas City Division technological spinoff through 1978
No full textThe results of work of Bendix Kansas City Division are made available in the form of technical reports that are processed through the DOE Technical Information Center in Oak Ridge. The present report lists the documents released by the Division, along with author and subject indexes. Drawing sets released are also listed. Locations of report collections in the U.S., other countries, and international agencies are provided. (RWR
The potential distribution of tropical lowland cloud forest as revealed by a novel MODIS-based fog/low stratus night-time detection scheme
No full textFog is a crucial driver of epiphyte richness in tropical montane cloud forests but its spatial occurrence and role in tropical lowland areas is poorly understood. Recent studies in French Guiana have reported high epiphyte richness in previously undescribed "tropical lowland cloud forest" (LCF) due to radiation fog. Here, we analyze the spatial extent of fog/low stratus (FLS) in lowland forests of French Guiana using the frequency distribution by means of night-time MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data for the years 2007-2010. The analysis is based on a newly developed dynamic threshold-test method relying on brightness temperature differences between thermal and mid-infrared bands. Individual thresholds for the discrimination between fog/low stratus and cloud-free pixels were retrieved by radiative transfer calculations and validated using discriminant analysis. The thresholds dynamically depend on total precipitable water (TPW) and the terrain-induced maximum possible sub-pixel fog coverage. The results of the new retrieval were validated using in-situ data and compared to results from existing fog detection algorithms, showing an improvement of the new detection scheme regarding the capability to detect sub-pixel fog coverage under varying TPW. FLS frequency maps derived from the novel fog classification scheme indicate a widespread distribution of night-time fog in river valleys, marking a multitude of potential areas for LCF throughout French Guiana. LCF is probably not only a local phenomenon but also may be widely distributed in river valleys in the lowland tropics, with significant consequences for biodiversity mapping in tropical lowland areas. (C) 2014 Elsevier Inc. All rights reserved.German Research Foundation (DFG) [BE 1780/13-1, GR 1588/12-1
Diversity and vertical distribution of epiphytic liverworts in lowland rain forest and lowland cloud forest of French Guiana
No full textRecent evidence is emerging that tropical cloud forests are not restricted to mountains, but may also be found in tropical lowland areas, the so-called 'tropical lowland cloud forest' (LCF). LCF occurs in river valleys with high air humidity and morning fog, and is rich in epiphytes. We explored the diversity of bark-inhabiting liverworts in LCF, a group of organisms known to be sensitive indicators of humidity. To test the hypothesis that LCF differs in species richness and species composition from lowland rain forest without fog (LRF), we sampled liverwort diversity in LCF and LRF on 48 whole trees in two sites in French Guiana. Sampling efficiency (=no. of species found as percentage of estimated total number of species) was about 90% in both forest types. Species richness in LCF was significantly higher than in LRF and species composition differed in all height zones; moreover, LCF had three times more indicator species. Indicators of LCF included shade epiphytes and generalists that occurred also in montane forests, those of LRF were sun epiphytes characteristic of rather dry, open sites. The detected differences in liverwort diversity of LCF and LRF are explained by the more humid conditions in LCF as compared with LRF. A comparison of liverwort richness along elevational gradients in the Neotropics showed that species richness differs more strongly among forest type (rain forest, cloud forest) than among elevation and that lowland cloud forests may be richer in species than montane rain forests. The data indicate that elevational comparisons of bryophyte species diversity in the Tropics should make a distinction between rain forests and cloud forests.German Research Foundation (DFG) [GR 1588/13-1, BE 1780/13-1
Seasonality of weather and tree phenology in a tropical evergreen mountain rain forest
No full textBendix J, Homeier J, Ortiz EC, et al. Seasonality of weather and tree phenology in a tropical evergreen mountain rain forest. International Journal of Biometeorology. 2006;50(6):370-384.Flowering and fruiting as phenological events of 12 tree species in an evergreen tropical mountain rain forest in southern Ecuador were examined over a period of 3-4 years. Leaf shedding of two species was observed for 12 months. Parallel to the phenological recordings, meteorological parameters were monitored in detail and related to the flowering and fruiting activity of the trees. In spite of the perhumid climate of that area, a high degree of intra- and inter-specific synchronisation of phenological traits was apparent. With the exception of one species that flowered more or less continuously, two groups of trees could be observed, one of which flowered during the less humid months (September to October) while the second group started to initiate flowers towards the end of that phase and flowered during the heavy rains (April to July). As reflected by correlation coefficients, the all-time series of meteorological parameters showed a distinct seasonality of 8-12 months, apparently following the quasi-periodic oscillation of precipitation and related cloudiness. As revealed by power spectrum analysis and Markov persistence, rainfall and minimum temperature appear to be the only parameters with a periodicity free of long-term variations. The phenological events of most of the plant species showed a similar periodicity of 8-12 months, which followed the annual oscillation of relatively less and more humid periods and thus was in phase or in counter-phase with the oscillations of the meteorological parameters. Periods of unusual cold or dryness, presumably resulting from underlying longer-term trends or oscillations (such as ENSO), affected the homogeneity of quasi-12-month flowering events, fruit maturation and also the production of germinable seeds. Some species show underlying quasi-2-year-oscillations, for example that synchronise with the development of air temperature; others reveal an underlying decrease or increase in flowering activity over the observation period, influenced for instance by solar irradiance. As Ecuador suffers the highest rate of deforestation in South America, there is an urgent need for indigenous plant material for reforestation. A detailed knowledge of the biology of reproduction in relation to governing external factors (mainly climate) is thus required
Epiphyte Biomass and Canopy Microclimate in the Tropical Lowland Cloud Forest of French Guiana
No full textRecent work on bryophyte diversity in lowland forests of northern South America has suggested the existence of a new type of cloud forest, the 'tropical lowland cloud forest' (LCF). LCF occurs in river valleys in hilly areas with high air humidity and morning fog, and is rich in epiphytes. We explored epiphyte abundance and canopy microclimate of LCF in a lowland area (200-400 m asl) near Saul, central French Guiana. We analyzed the vertical distribution of epiphytic cover and biomass on 48 trees, in LCF and in lowland rain forest (LRF) without fog. Trees in LCF had significantly more epiphytic biomass than in LRF; mean total epiphytic biomass in LCF was about 59 g/m(2), and 35 g/m(2) in LRF. In all height zones on the trees, total epiphyte cover in LCF exceeded that in LRF, with ca 70 percent mean cover in LCF and ca 15 percent in LRF. During both wet and dry seasons, mean diurnal relative air humidity (RH) was higher in LCF than in LRF, and persistence of high RH after sunrise significantly longer in LCF. We suggest that the prolonged availability of high air humidity in LCF and the additional input of liquid water through fog, enhance epiphyte growth in LCF by shortening the desiccation period and lengthening the period of photosynthetic activity of the plants.German Research Foundation (DFG) [GR 1588/13-1, BE 1780/13-1
PHYLOGENETIC NICHE CONSERVATISM DOES NOT EXPLAIN ELEVATIONAL PATTERNS OF SPECIES RICHNESS, PHYLODIVERSITY AND FAMILY AGE OF TREE ASSEMBLAGES IN ANDEAN RAINFOREST
No full textPhylogenetic niche conservatism (PNC) is the tendency of species within a clade to retain ancestral traits and to persist in their primary ecological niches on geological time scales. It links evolutionary and ecological processes and has been hypothesized to explain patterns of species richness and the composition of species assemblages. Decreasing patterns of species richness along latitudinal gradients were often explained by the combination of ancient tropical climates, trait retention of tropical lineages and environmental filtering. PNC also predicts decreasing phylodiversity and family age with decreasing tropicality and has been invoked to explain these patterns along climatic gradients across latitudinal as well as elevational gradients. However, recent studies on tree assemblages along latitudinal and elevational gradients in South America found patterns contradicting the PNC framework. Our study aims to shed light on these contradictions using three different metrics of the phylogenetic composition that form a gradient from recent evolutionary history to deep phylogenetic relationships. We analyzed the relationships between elevation and taxonomic species richness, phylodiversity and family age of tree assemblages in Andean rainforests in Ecuador. In contrast to predictions of the PNC we found no associations of elevation with species richness of trees and increasing clade level phylodiversity and family age of the tree assemblages with elevation. Interestingly, we found that patterns of phylodiversity across the studied elevation gradient depended especially on the deep nodes in the phylogeny. We therefore suggest that the dispersal of evolutionarily old plant lineages with extra-tropical origins influences the recent composition of tree assemblages in the Andes. Further studies spanning broader ecological gradients and using better resolved phylogenies to estimate family and species ages are needed to obtain a deeper mechanistic understanding of the processes that drive the assembly of tree communities along elevational gradients
Canopy level fog occurrence in a tropical lowland forest of French Guiana as a prerequisite for high epiphyte diversity
No full textFog frequency and the meteorological processes leading to fog formation have never been studied in depth in tropical lowland forest areas. This study provides detailed evidence of frequent fog occurrence in lowland valleys of central French Guiana. Fog frequency showed a clear diurnal course, with a maximum before sunrise; average fog duration was 4.6 h. The diurnal course of visibility was positively correlated with the diurnal course of humidity in the above-canopy air. Fog persistence correlated significantly with atmospheric parameters during the dry season, but not during the rainy season. The main trigger of fog development in the lowland forest seemed to be precipitation, leading to higher soil moisture, greater evapotranspiration and, thus, higher water content of air. An increasing temperature difference between valley and hill sites after sunset, together with more frequent down-slope winds during nights with long fog periods, points at some influence of katabatic flows. The frequent occurrence of fog in the valleys correlated with significantly higher epiphyte diversities in valley forests as compared to hill forests, and supported the occurrence of the hitherto undescribed, epiphyte-rich "tropical lowland cloud forest" (LCF) in the valleys. The higher epiphyte diversity in LCF coincided with significantly higher relative air humidity in LCF than in hill forest. The ecological benefits of fog for the epiphytes in LCF are surplus of moisture and delayed onset of the stress period, particularly in the dry season. (C) 2010 Elsevier B.V. All rights reserved.German Research Foundation (DFG) [BE 1780/13-1, GR 1588/12-1
Log of Apollo Lunar Surface Experiments Package technical memoranda (ATM)
No full textGives the ATM number, issue date, author, and title for the ALSEP technical memoranda (ATM) from Bendix
DIVERSITY AND VERTICAL DISTRIBUTION OF FILMY FERNS AS A TOOL FOR IDENTIFYING THE NOVEL FOREST TYPE "TROPICAL LOWLAND CLOUD FOREST"
No full textRecent studies on bryophyte and macrolichen diversity in lowland forests of northern South America have shown the existence of a novel forest type, the "tropical lowland cloud forest" (LCF). LCF is very rich in epiphytes and occurs in lowland river valleys where radiation fog in the morning provides an additional input of liquid water. Because of their dependence on frequent precipitation and low evaporation, Hymenophyllaceae (filmy ferns) are a suitable group for studying moisture availability. We sampled epiphytic Hymenophyllaceae on 32 trees in French Guiana, 16 in LCF and 16 in adjacent rain forest (LRF). Abundance of Hymenophyllaceae was significantly higher in LCF than in LRF. Only 10% of trees in LRF were inhabited by filmy ferns, in contrast to 70% in LCF. Moreover, the number of species recorded in LCF (9) was more than twice as high than in LRF (4), and the mean number per tree 8 times higher. Species restricted to the understory of LRF occurred in the canopy of LCF. We attribute the detected differences in diversity and vertical distribution of Hymenophyllaceae in the two forest types to the occurrence of fog in LCF, enhancing the availability of liquid water and thus Facilitating the establishment and growth of the filmy ferns. Also, radiation protection against evaporative loss seems to play a crucial role in the vertical distribution of filmy fern diversity. The observed differences in filmy fern diversity and distribution in LCF and LRF represent novel traits separating the two forest types, and indicate that Hymenophyllaceae species are sensitive indicators of lowland cloud forest.German Research Foundation (DFG) [GR 1588/13-1, BE 1780/13-1
THERMAL STRUCTURE OF A MEGADIVERSE ANDEAN MOUNTAIN ECOSYSTEM IN SOUTHERN ECUADOR AND ITS REGIONALIZATION
No full textThe thermal structure of a megadiverse mountain ecosystem in southern Ecuador is examined on the basis of temperature measurements inside the natural mountain forest and at open-sites along an altitudinal gradient from 1600 to 3200 m. The main methodological aim of the current study is to develop in air temperature regionalization tool to provide spatial datasets on average monthly mean, minimum and maximum temperature by using observation data. The maps, based on data of the period 1999-2007, are needed by ecological projects working on various plots where no climate station data arc available. The temperature maps arc generated by combining a straight forward detrending technique with a Digital Elevation Model and a satellite-based land cover classification which also provides the relative forest cover per pixel. The topical aim of the study is to investigate the thermal structure Of both manifestations Of Our ecosystem (pastures and natural vegetation) with special considerations to the ecosystem temperature regulation service by converting natural forest into pasture. The results reveal a clear thermal differentiation over the year, partly triggered by the change of synoptic weather situation but also by land cover effects. Thermal amplitudes are particularly low during the main rainy season when cloudiness and air humidity are high, but markedly pronounced in the relative dry season when daily irradiance and Outgoing nocturnal radiation cause distinct differences between the land cover units. Particularly the lower pasture areas gained by slash and burn of the natural forest exhibit the most extreme thermal conditions while the atmosphere inside the mountain forest is slightly cooler clue to the regulating effects of the dense vegetation. Thus, clearing the forest clearly reduces the thermal regulation function (regulating ecosystem services) of the ecosystem which might become Problematic under future global warming
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