Home About us Contact
|
Home About us Contact | ||
|
|
||
Microclimate
Selected AbstractsCorticolous arthropods under climatic fluctuations: compensation is more important than migrationECOGRAPHY, Issue 1 2005Andreas Prinzing Animals can cope with fluctuating climates by physiological tolerance, tracking of climatic fluctuations (migration) and compensatory redistribution among (micro)habitats (compensation). Compensation is less demanding and thus more important than migration at large geographic scales. It is not clear however which strategy is more important at the small scale of a microhabitat landscape. I investigated how six arthropod species (Collembola, Oribatei, Psocoptera, Isopoda) respond to microclimatic fluctuations at the surface of exposed tree trunks. Across a nine-month period I characterized the microclimatic zonation of 299 trunks, and focally sampled the arthropods from different microhabitat types (different cryptogam species and bark crevices) within different microclimatic zones. I found that compensatory microhabitat-use was a general phenomenon. The distribution of all species across microhabitats was influenced significantly by ambient microclimate. Also, the arthropods' microhabitat use changed throughout their ontogeny, and microhabitats were used even if they were rare. Most interestingly, the arthropods responded to microclimatic fluctuations primarily by redistribution among microhabitats and less by fluctuations of overall abundances across all microhabitats. Hence compensation was more important than migration. The animals moved for centimeters to decimeters rather than for decimeters to meters; they perceived and utilized their environment primarily at the finest, but also most complex scale. This has implications for the resilience of arthropod populations, their interactions with cryptogams and the turnover of species between macrohabitats. [source] Impact of reindeer grazing on ground-dwelling Carabidae and Curculionidae assemblages in LaplandECOGRAPHY, Issue 4 2003Otso Suominen Reindeer Rangifer tarandus L. grazing shapes forest vegetation, microclimate, and soil respiration in Lapland, especially due to grazing on lichens (Cladina). We studied how these changes and their magnitude affect ground-dwelling species of beetle families Carabidae (predators) and Curculionidae (herbivores), by using pitfall traps to collect invertebrates from pairs of grazed and ungrazed study plots over a wide range of site types. Changes in abundance, composition, richness and diversity of beetle assemblage were tested in relation to magnitude of the impacts on vegetation. The species compositions of Carabidae and Curculionidae differed between grazed and ungrazed plots in all sites. The relative difference between grazed and ungrazed plots in the number of individuals increased linearly with the impact of reindeer on vegetation cover. Carabid beetles, as a family, were more common in grazed plots in all sites. Curculionid beetles were more common in ungrazed plots in the birch dominated sites. This difference was mainly due to the species that feeds on deciduous leaves. In the pine dominated sites with high Cladina cover and more changes in ground vegetation, the number of curculionids feeding on conifers was higher in grazed plots. Species richness and diversity (H') of both families were higher in grazed plots. Of the total 27 species, 11 were found only in grazed plots, while not a single species was found only in ungrazed plots. The relative difference between plots in diversity and evennes (H'/H'max) had humped response to the difference in Cladina cover. The diversity values were greater in grazed plots at the intermediate levels of grazing impact, and only in sites with very low or extremely high Cladina cover difference was the diversity higher in ungrazed plots. The response of beetle diversity resembled the hypotheses suggested for the relationship between grazing and vegetation diversity: greatest positive effect at intermediate grazing intensity and negative effects at unproductive sites. [source] Seasonal polydomy in a polygynous supercolony of the odorous house ant, Tapinoma sessileECOLOGICAL ENTOMOLOGY, Issue 6 2008GRZEGORZ BUCZKOWSKI Abstract 1.,The odorous house ant, Tapinoma sessile, is a native ant species common throughout North America. In its natural habitat, T. sessile is a low-key species that consists of small colonies. In invaded urban areas, T. sessile exhibits extreme polygyny and polydomy and becomes a dominant invasive pest. 2.,The current study examined: (i) the density, persistence, and the spatial distribution of nests in a large supercolony of T. sessile, (ii) trail abundance and overall colony connectivity as facilitated by the network of trails, (iii) the abundance and the spatial distribution of competing ant species, and (iv) the effect of environmental factors on the number and distribution of T. sessile nests. 3.,A distinct pattern of seasonal polydomy was observed, whereby the colony undergoes an annual fission-fusion cycle. The colony occupies one or a few nests during the winter, experiences rapid exponential growth in the spring to colonize available nesting sites, reaches maximum nest density in the summer, and again coalesces in the winter, returning to the same winter location year after year. The trails show spatio-temporal variation as well, depending on the location of nesting and foraging sites. Furthermore, nest movements may be driven by soil microclimate and proximity to man-made structures. 4.,In total, 119 ant nests were discovered in a 3.15 ha plot, 90 (76%) of which belonged to T. sessile. Tapinoma sessile exhibited strong colony connectivity as 78/90 (87%) of nests were connected to at least one other nest by a trail. Mean persistence time for T. sessile nests was 133 ± 5 days. 5.,Results indicate that T. sessile is a highly adaptable native ant species that exhibits a high degree of flexibility in its colony social structure. A high degree of polygyny and polydomy may contribute to its ecological dominance and pest status in urban environments. [source] Seasonal spatial dynamics and causes of nest movement in colonies of the invasive Argentine ant (Linepithema humile)ECOLOGICAL ENTOMOLOGY, Issue 5 2006NICOLE E. HELLER Abstract 1.,Colony organisation and movement behaviour of the Argentine ant (Linepithema humile) was studied over 3 years in field populations in California and in captive colonies in the laboratory. This invasive species is highly polydomous and unicolonial; colonies consist of expansive and fluid networks of nests and trails. The spatial and temporal organisation of colonies may contribute to ecological dominance. 2.,Argentine ant nests and inter-nest trails shift in size, abundance, and location, so that colony networks are spatially contracted in the winter and expanded spring to autumn. Colonies occupy permanent sites; ants migrated to and from the same winter nest locations year after year, and occupied 30% of the same nests repeatedly during seasonal migrations. 3.,Nests were moved on average 2,3 m. Forty-two per cent were occupied less than 1 month, 4% the entire study, and the other 54% lasted 3.9 ± 2.3 months (mean ± SD). 4.,Nests were located within 2,4 m of woody plants, in warm sites in the winter and cool sites in the summer. Both humidity and food availability influenced nest-site choice in laboratory colonies. However, when faced with a trade-off between factors, the ants chose humid nest boxes over nest boxes near food, and ants moved nests only in response to changes in humidity and not distance to food. 5.,The results indicate that L. humile colonies are seasonally polydomous, and that nest movements are driven by changes in microclimate. Colony organisation maintains high local density and increases food supply, which may improve the competitive ability of L. humile colonies and reduce opportunities for species coexistence. [source] Factors influencing the seasonal life history of the pitcher-plant mosquito, Wyeomyia smithiiECOLOGICAL ENTOMOLOGY, Issue 2 2005Alan O. Bergland Abstract., 1.,The effects of resource levels, thermal microclimate, and seasonal oviposition patterns on fecundity and survivorship in the pitcher-plant mosquito, Wyeomyia smithii (Coq.), were examined at a northern Wisconsin bog over the course of 2 years. Wyeomyia smithii are bivoltine at this locality, thereby enabling the study of summer and overwintering generations separately. 2.,Nutrient resources of W. smithii were not limiting and there was no indication of density-dependent survivorship or fecundity. 3.,Oviposition rates were highest in young, large pitchers and individual mosquitoes appeared to allocate only a few eggs to any one leaf. 4.,Winter was the harsh season, and the principal manifestation of seasonal harshness was reduced survivorship. 5.,Overwintering W. smithii that had been oviposited later in the summer had a higher odds of survival than those oviposited earlier in the summer. 6.,It was concluded that dispersal of eggs among many pitchers serves to spread the risk of encountering lethal winter temperatures among spatially unpredictable patches. [source] Phenological model of pear psylla Cacopsylla pyriENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2005L. Schaub Abstract A phenological model of first- and second-generation pear psylla, Cacopsylla pyri L. (Homoptera: Psyllidae), was developed. The model included a time-distributed delay and was based on authors' observations and literature data of termination of reproductive diapause, oviposition-period length, and developmental duration of juvenile stages depending on temperature. After calibrating microclimate, the model provided a good simulation of observations from different orchards in Switzerland and Italy over several years. The model or simulated output tables can be used to improve timing of monitoring and control measures. [source] The life history of Salicaceae living in the active zone of floodplainsFRESHWATER BIOLOGY, Issue 4 2002S. KARRENBERG 1.,Exposed riverine sediments are difficult substrata for seedling establishment because of extremes in the microclimate, poor soil conditions and frequent habitat turnover. Various species of willows and poplars (Salicaceae) appear to be particularly successful in colonising such sediments and are often dominant in floodplain habitats throughout the northern temperate zone. 2.,In many Salicaceae regeneration seems to be adapted to regular disturbance by flooding. Efficient seed dispersal is achieved by the production of abundant seed in spring and early summer, which are dispersed by air and water. Seeds are short-lived and germinate immediately on moist surfaces. Seedling establishment is only possible if these surfaces stay moist and undisturbed for a sufficient period of time. 3.,Larger plants of Salicaceae have exceptional mechanical properties, such as high bending stability, which enable them to withstand moderate floods. If uprooted, washed away or fragmented by more powerful floods these plants re-sprout vigorously. 4.,While these life characteristics can be interpreted as adaptations to the floodplain environment, they may also cause a high genetic variability in populations of Salicaceae and predispose Salicaceae to hybridization. Thus, a feed back between adaptive life history characteristics and the evolutionary process is proposed. [source] Relative importance of microhabitat, plant form and photosynthetic physiology to carbon gain in two alpine herbsFUNCTIONAL ECOLOGY, Issue 2 2001M. J. Germino Abstract 1.,The effects of microhabitat and plant form on sunlight interception, leaf temperatures, frost occurrence and photosynthesis were evaluated for Caltha leptosepala DC and Erythronium grandiflorum Pursh. Both plants are perennials that commonly emerge from alpine snowbanks where the combination of cool temperatures and strong sunlight is among the most extreme for vascular plants. 2., Caltha leptosepala occurred in microsites where colder air accumulates, and has larger, less inclined and more densely clustered leaves compared to E. grandiflorum (which has two steeply inclined leaves). 3.,These differences in microsite and plant form led to leaf temperatures below 0 °C on 70% of nights during the summer growth season in C. leptosepala, compared to only 38% in E. grandiflorum. Leaves of C. leptosepala warmed more slowly on mornings following frosts compared to E. grandiflorum, due to less aerodynamic coupling between leaf and air temperature, and also a 45% smaller ratio of sunlit to total leaf area due to mutual shading among leaves. 4.,As a result, night frost did not affect subsequent CO2 assimilation (A) in E. grandiflorum, while frostless nights and warmer mornings led to 35% greater A in C. leptosepala in the early morning. 5.,There were no appreciable differences in the temperature and light response of photosynthesis between the two species. The apparent quantum yield of A declined only ,8% in both species following frost and exposure to strong sunlight, indicating little adjustment of photosynthetic physiology. 6.,Greater daily carbon gain probably occurs for E. grandiflorum because of its plant form and microclimate, rather than differences in photosynthetic physiology. [source] Near,surface ground temperature regime variability in selected microenvironments, Kärkevagge, Swedish LaplandGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3-4 2002Colin E. Thorn The importance of topographic microvariability in influencing shallow (10,50 cm depths) soil temperature regimes in arctic,alpine Kärkevagge, northern Sweden, from August 1999 to July 2000 is demonstrated using six sites. The ground microclimate on the tops of very large boulders forming an extensive boulder field in the central valley bottom is more comparable to that at an alpine ridge,crest site 300 m higher than it is to the microclimate at the base of one of the boulders. The boulder crests also differ substantially from the more generalized valley,bottom conditions outside the boulder field. Assuming that chemical processes may be active at temperatures at or above 0°C, sites in the valley experience favorable conditions from 159 to 324 days of the year. Aside from the annual cycle, freeze,thaw cycles are infrequent within Kärkevagge. [source] Synergy between small- and large-scale feedbacks of vegetation on the water cycleGLOBAL CHANGE BIOLOGY, Issue 7 2005Marten Scheffer Abstract Predictions of the effects of climate change on the extent of forests, savannas and deserts are usually based on simple response models derived from actual vegetation distributions. In this review, we show two major problems with the implicitly assumed straightforward cause,effect relationship. Firstly, several studies suggest that vegetation itself may have considerable effects on regional climate implying a positive feedback, which can potentially lead to large-scale hysteresis. Secondly, vegetation ecologists have found that effects of plants on microclimate and soils can cause a microscale positive feedback, implying that critical precipitation conditions for colonization of a site may differ from those for disappearance from that site. We argue that it is important to integrate these nonlinearities at disparate scales in models to produce more realistic predictions of potential effects of climate change and deforestation. [source] Vegetation responses in Alaskan arctic tundra after 8 years of a summer warming and winter snow manipulation experimentGLOBAL CHANGE BIOLOGY, Issue 4 2005C.-H. A. Wahren Abstract We used snow fences and small (1 m2) open-topped fiberglass chambers (OTCs) to study the effects of changes in winter snow cover and summer air temperatures on arctic tundra. In 1994, two 60 m long, 2.8 m high snow fences, one in moist and the other in dry tundra, were erected at Toolik Lake, Alaska. OTCs paired with unwarmed plots, were placed along each experimental snow gradient and in control areas adjacent to the snowdrifts. After 8 years, the vegetation of the two sites, including that in control plots, had changed significantly. At both sites, the cover of shrubs, live vegetation, and litter, together with canopy height, had all increased, while lichen cover and diversity had decreased. At the moist site, bryophytes decreased in cover, while an increase in graminoids was almost entirely because of the response of the sedge Eriophorum vaginatum. These community changes were consistent with results found in studies of responses to warming and increased nutrient availability in the Arctic. However, during the time period of the experiment, summer temperature did not increase, but summer precipitation increased by 28%. The snow addition treatment affected species abundance, canopy height, and diversity, whereas the summer warming treatment had few measurable effects on vegetation. The interannual temperature fluctuation was considerably larger than the temperature increases within OTCs (<2°C), however. Snow addition also had a greater effect on microclimate by insulating vegetation from winter wind and temperature extremes, modifying winter soil temperatures, and increasing spring run-off. Most increases in shrub cover and canopy height occurred in the medium snow-depth zone (0.5,2 m) of the moist site, and the medium to deep snow-depth zone (2,3 m) of the dry site. At the moist tundra site, deciduous shrubs, particularly Betula nana, increased in cover, while evergreen shrubs decreased. These differential responses were likely because of the larger production to biomass ratio in deciduous shrubs, combined with their more flexible growth response under changing environmental conditions. At the dry site, where deciduous shrubs were a minor part of the vegetation, evergreen shrubs increased in both cover and canopy height. These changes in abundance of functional groups are expected to affect most ecological processes, particularly the rate of litter decomposition, nutrient cycling, and both soil carbon and nitrogen pools. Also, changes in canopy structure, associated with increases in shrub abundance, are expected to alter the summer energy balance by increasing net radiation and evapotranspiration, thus altering soil moisture regimes. [source] Will photosynthesis of maize (Zea mays) in the US Corn Belt increase in future [CO2] rich atmospheres?GLOBAL CHANGE BIOLOGY, Issue 6 2004An analysis of diurnal courses of CO2 uptake under free-air concentration enrichment (FACE) Abstract The C4 grass Zea mays (maize or corn) is the third most important food crop globally in terms of production and demand is predicted to increase 45% from 1997 to 2020. However, the effects of rising [CO2] upon C4 plants, and Z. mays specifically, are not sufficiently understood to allow accurate predictions of future crop production. A rainfed, field experiment utilizing free-air concentration enrichment (FACE) technology in the primary area of global corn production (US Corn Belt) was undertaken to determine the effects of elevated [CO2] on corn. FACE technology allows experimental treatments to be imposed upon a complete soil,plant,atmosphere continuum with none of the effects of experimental enclosures on plant microclimate. Crop performance was compared at ambient [CO2] (354 , mol mol,1) and the elevated [CO2] (549 ,mol mol,1) predicted for 2050. Previous laboratory studies suggest that under favorable growing conditions C4 photosynthesis is not typically enhanced by elevated [CO2]. However, stomatal conductance and transpiration are decreased, which can indirectly increase photosynthesis in dry climates. Given the deep soils and relatively high rainfall of the US Corn Belt, it was predicted that photosynthesis would not be enhanced by elevated [CO2]. The diurnal course of gas exchange of upper canopy leaves was measured in situ across the growing season of 2002. Contrary to the prediction, growth at elevated [CO2] significantly increased leaf photosynthetic CO2 uptake rate (A) by up to 41%, and 10% on average. Greater A was associated with greater intercellular [CO2], lower stomatal conductance and lower transpiration. Summer rainfall during 2002 was very close to the 50-year average for this site, indicating that the year was not atypical or a drought year. The results call for a reassessment of the established view that C4 photosynthesis is insensitive to elevated [CO2] under favorable growing conditions and that the production potential of corn in the US Corn Belt will not be affected by the global rise in [CO2]. [source] Not seeing the ocean for the islands: the mediating influence of matrix-based processes on forest fragmentation effectsGLOBAL ECOLOGY, Issue 1 2006John A. Kupfer ABSTRACT The pervasive influence of island biogeography theory on forest fragmentation research has often led to a misleading conceptualization of landscapes as areas of forest/habitat and ,non-forest/non-habitat' and an overriding focus on processes within forest remnants at the expense of research in the human-modified matrix. The matrix, however, may be neither uniformly unsuitable as habitat nor serve as a fully,absorbing barrier to the dispersal of forest taxa. In this paper, we present a conceptual model that addresses how forest habitat loss and fragmentation affect biodiversity through reduction of the resource base, subdivision of populations, alterations of species interactions and disturbance regimes, modifications of microclimate and increases in the presence of invasive species and human pressures on remnants. While we acknowledge the importance of changes associated with the forest remnants themselves (e.g. decreased forest area and increased isolation of forest patches), we stress that the extent, intensity and permanence of alterations to the matrix will have an overriding influence on area and isolation effects and emphasize the potential roles of the matrix as not only a barrier but also as habitat, source and conduit. Our intention is to argue for shifting the examination of forest fragmentation effects away from a patch-based perspective focused on factors such as patch area and distance metrics to a landscape mosaic perspective that recognizes the importance of gradients in habitat conditions. [source] Increasing representation of localized dung beetles across a chronosequence of regenerating vegetation and natural dune forest in South AfricaGLOBAL ECOLOGY, Issue 3 2002Adrian L. V. Davis Abstract Aim Species assemblages with high proportions of localized taxa occur in regional islands with a history of strong eco-climatic separation from adjacent systems. Current disturbance in such islands of relictualism or endemism disrupts the distinctive local character in favour of regionally distributed taxa with a wider range of tolerances. However, rehabilitation of the system should restore the localized biota. Thus, we used biogeographical composition to assess progress towards restoration of the dung beetle fauna associated with such an island of endemism following dredge-mining. Location The study was conducted in natural coastal dune forest and a 23-year chronosequence of regenerating dune vegetation in the Maputaland centre of endemism, KwaZulu-Natal, South Africa. Methods Dung beetles were trapped in eight stands of regenerating vegetation of different ages (< 1 year to ~21 years) and in four stands of natural dune forest with differing ecological characteristics defined by measurements of vegetative physiognomy and microclimate. Species groups defined from multivariate analysis of biogeographical distribution patterns and vegetation associations were used to demonstrate quantitative compositional changes in the dung beetle assemblages across the chronosequence to natural forest. Results Three biogeographical groups were defined. One group comprised species widespread in southern Africa or both southern and east Africa. The other two groups were endemic, one to the east coast and the other to Maputaland. There was a general trend from dominance by regionally distributed dung beetle taxa to dominance by locally distributed taxa across the chronosequence of regenerating vegetation from grassland, to open Acacia karroo thicket, to dense A. karroo- dominated woodland. However, this trend was linked closely to the relative physiognomic and microclimatic similarity between the regenerating vegetation and natural forest. Thus, proportions of locally distributed taxa were lower in older chronosequence woodland (~18,~21 years) with its low canopy cover and open understorey than in dense early chronosequence woodland (~9,~12 years), which is physiognomically and microclimatically closer to species-diverse natural forest with its dense canopy and understorey. Overall, the present dung beetle community comprises five species groups. Single widespread (21 spp.) and endemic groups (14 spp.) showed similar patterns of association with early chronosequence grassland and open thicket stands. A single widespread (3 spp.) and two endemic shade-associated groups (3 and 11 spp.) showed differing patterns of association centred, respectively, in late chronosequence woodland, natural forest, or all shaded stands. Main conclusions At 23 years, vegetative regeneration is still at an early stage, but abundant activity of most, although not all species recorded in natural forest, is recovered with the closure of the woodland canopy at ~9 years. Compositional differences with respect to natural forest vary closely with vegetative physiognomy and its effect on the microclimate. Therefore, full compositional recovery is dependent on the re-establishment of natural forest physiognomy and microclimate. [source] Above-stream microclimate and stream surface energy exchanges in a wildfire-disturbed riparian zoneHYDROLOGICAL PROCESSES, Issue 17 2010J. A. Leach Abstract Stream temperature and riparian microclimate were characterized for a 1·5 km wildfire-disturbed reach of Fishtrap Creek, located north of Kamloops, British Columbia. A deterministic net radiation model was developed using hemispherical canopy images coupled with on-site microclimate measurements. Modelled net radiation agreed reasonably with measured net radiation. Air temperature and humidity measured at two locations above the stream, separated by 900 m, were generally similar, whereas wind speed was poorly correlated between the two sites. Modelled net radiation varied considerably along the reach, and measurements at a single location did not provide a reliable estimate of the modelled reach average. During summer, net radiation dominated the surface heat exchanges, particularly because the sensible and latent heat fluxes were normally of opposite sign and thus tended to cancel each other. All surface heat fluxes shifted to negative values in autumn and were of similar magnitude through winter. In March, net radiation became positive, but heat gains were cancelled by sensible and latent heat fluxes, which remained negative. A modelling exercise using three canopy cover scenarios (current, simulated pre-wildfire and simulated complete vegetation removal) showed that net radiation under the standing dead trees was double that modelled for the pre-fire canopy cover. However, post-disturbance standing dead trees reduce daytime net radiation reaching the stream surface by one-third compared with complete vegetation removal. The results of this study have highlighted the need to account for reach-scale spatial variability of energy exchange processes, especially net radiation, when modelling stream energy budgets. Copyright © 2010 John Wiley & Sons, Ltd. [source] A comparison of forest and moorland stream microclimate, heat exchanges and thermal dynamicsHYDROLOGICAL PROCESSES, Issue 7 2008David M. Hannah Abstract Although the importance of riparian forest in moderating stream temperature variability is recognized, most previous research focuses on conifer harvesting effects and summer maximum temperature with highly variable findings. This article compares stream temperature, microclimate and heat exchange dynamics between semi-natural forest and moorland (no trees) reaches in the Scottish Cairngorms over two calendar years to provide a longer-term perspective. Mean daily water column temperature is warmer for moorland than forest in late winter,early spring, but cooler in summer. Daily water column temperature range is greater for moorland than forest. Streambed temperature dynamics are markedly different between reaches, reflecting contrasting groundwater,surface water (GW,SW) interactions. Mean, minimum and maximum daily air temperature is cooler, humidity is lower, and wind speed is much higher for moorland than forest on average. Net radiation is the dominant heat sink in autumn,winter and major heat source in spring,summer for moorland and summer for forest. Net radiation is greater in summer and lower in winter for moorland than forest. Sensible heat is an energy source in autumn,winter and sink in spring,summer, with loss (gain) greater in summer (winter) for moorland than forest. Latent heat is predominantly a sink for both reaches, with magnitude and variability higher for moorland than forest. Streambed heat flux is much smaller than fluxes at the air,water interface, with moorland and forest illustrating seasonal and between-reach differences attributable to different GW,SW interactions. Seasonal patterns in stream energy budget partitioning are illustrated schematically. To our knowledge, this is the first such study of mixed woodland, which generates notably different results to work on coniferous forest. This research provides a process basis to model stream thermal impact of changes in forest practice, and so inform decision making by land and water resource managers. Copyright © 2008 John Wiley & Sons, Ltd. [source] Seasonal snowpack dynamics and runoff in a cool temperate forest: lysimeter experiment in Niigata, JapanHYDROLOGICAL PROCESSES, Issue 20 2005Andrew C. Whitaker Abstract Seasonal snowpack dynamics are described through field measurements under contrasting canopy conditions for a mountainous catchment in the Japan Sea region. Microclimatic data, snow accumulation, albedo and lysimeter runoff are given through the complete winter season 2002,03 in (1) a mature cedar stand, (2) a larch stand, and (3) a regenerating cedar stand or opening. The accumulation and melt of seasonal snowpack strongly influences streamflow runoff during December to May, including winter baseflow, mid-winter melt, rain on snow, and diurnal peaks driven by radiation melt in spring. Lysimeter runoff at all sites is characterized by constant ground melt of 0·8,1·0 mm day,1. Rapid response to mid-winter melt or rainfall shows that the snowpack remains in a ripe or near-ripe condition throughout the snow-cover season. Hourly and daily lysimeter discharge was greatest during rain on snow (e.g. 7 mm h,1 and 53 mm day,1 on 17 December) with the majority of runoff due to rainfall passing through the snowpack as opposed to snowmelt. For both rain-on-snow and radiation melt events lysimeter discharge was generally greatest at the open site, although there were exceptions such as during interception melt events. During radiation melt instantaneous discharge was up to 4·0 times greater in the opening compared with the mature cedar, and 48 h discharge was up to 2·5 times greater. Perhaps characteristic of maritime climates, forest interception melt is shown to be important in addition to sublimation in reducing snow accumulation beneath dense canopies. While sublimation represents a loss from the catchment water balance, interception melt percolates through the snowpack and contributes to soil moisture during the winter season. Strong differences in microclimate and snowpack albedo persisted between cedar, larch and open sites, and it is suggested further work is needed to account for this in hydrological simulation models. Copyright © 2005 John Wiley & Sons, Ltd. [source] Using GIS to relate small mammal abundance and landscape structure at multiple spatial extents: the northern flying squirrel in Alberta, CanadaJOURNAL OF APPLIED ECOLOGY, Issue 3 2005MATTHEW WHEATLEY Summary 1It is common practice to evaluate the potential effects of management scenarios on animal populations using geographical information systems (GIS) that relate proximate landscape structure or general habitat types to indices of animal abundance. Implicit in this approach is that the animal population responds to landscape features at the spatial grain and extent represented in available digital map inventories. 2The northern flying squirrel Glaucomys sabrinus is of particular interest in North American forest management because it is known from the Pacific North-West as a habitat specialist, a keystone species of old-growth coniferous forest and an important disperser of hypogeous, mycorrhizal fungal spores. Using a GIS approach we tested whether the relative abundance of flying squirrel in northern Alberta, Canada, is related to old forest, conifer forest and relevant landscape features as quantified from management-based digital forest inventories. 3We related squirrel abundance, estimated through live trapping, to habitat type (forest composition: conifer, mixed-wood and deciduous) and landscape structure (stand height, stand age, stand heterogeneity and anthropogenic disturbance) at three spatial extents (50 m, 150 m and 300 m) around each site. 4Relative abundances of northern flying squirrel populations in northern and western Alberta were similar to those previously reported from other regions of North America. Capture rates were variable among sites, but showed no trends with respect to year or provincial natural region (foothills vs. boreal). 5Average flying squirrel abundance was similar in all habitats, with increased values within mixed-wood stands at large spatial extents (300 m) and within deciduous-dominated stands at smaller spatial extents (50 m). No relationship was found between squirrel abundance and conifer composition or stand age at any spatial extent. 6None of the landscape variables calculated from GIS forest inventories predicted squirrel abundance at the 50-m or 150-m spatial extents. However, at the 300-m spatial extent we found a negative, significant relationship between average stand height and squirrel abundance. 7Synthesis and applications. Boreal and foothill populations of northern flying squirrel in Canada appear unrelated to landscape composition at the relatively large spatial resolutions characteristic of resource inventory data commonly used for management and planning in these regions. Flying squirrel populations do not appear clearly associated with old-aged or conifer forests; rather, they appear as habitat generalists. This study suggests that northern, interior populations of northern flying squirrel are probably more related to stand-level components of forest structure, such as food, microclimate (e.g. moisture) and understorey complexity, variables not commonly available in large-scale digital map inventories. We conclude that the available digital habitat data potentially exclude relevant, spatially dependent information and could be used inappropriately for predicting the abundance of some species in management decision making. [source] Control of Plutella xylostella using polymer-formulated Steinernema carpocapsae and Bacillus thuringiensis in cabbage fieldsJOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2005S. Schroer Abstract:, Field trials evaluating the potential of the entomopathogenic nematode Steinernema carpocapsae and the feasibility to combine nematodes with Bacillus thuringiensis for sustainable control of the diamondback moth (DBM) Plutella xylostella were conducted in cabbage cultivated in the province Probolinggo, east Java and Indonesia. A single use of 0.5 million S. carpocapsae m,2 applied with a surfactant-polymer-formulation containing 0.3% xanthan and 0.3% Rimulgan® achieved a significant reduction of the insects per plant with >50% control after 7 days. Even 14 days after the application about 45% control was recorded and dead larvae containing nematodes were found. No significant effects were recorded when the formulation was compared with nematodes applied in water or with a surfactant alone. This was attributed to high humidity in the experimental area at the end of the rainy season and a microclimate in the cabbage heads favouring nematode survival. Weekly applications of B. thuringiensis (Turex®) or alternating applications of Turex® and the nematodes achieved >80% control. The application of both biological agents together every second week reached insignificant lower efficacy (70%). Nematodes can be used to substitute ineffective chemical insecticides and alterations with B. thuringiensis can prevent the further development of resistance against the bacterial control agent. [source] Raised thermoregulatory costs at exposed song posts increase the energetic cost of singing for willow warblers Phylloscopus trochilusJOURNAL OF AVIAN BIOLOGY, Issue 4 2005Sally Ward Sexually selected displays, such as bird song, are expected to be costly. We examined a novel potential cost to bird song: whether a less favourable microclimate at exposed song posts would be predicted to raise metabolic rate. We measured the microclimate and height at which willow warblers Phylloscopus trochilus sang and foraged. Song posts were higher than foraging sites. The wind speed was 0.6±0.3 ms,1 greater at song posts (mean±SD, N=12 birds). Song rate and song post selection were not influenced consistently by temperature or wind speed, but the birds sang from lower positions on one particularly windy day. This may have resulted from difficulty in holding on to exposed branches in windy conditions rather than a thermoregulatory constraint. The results suggest that the extra thermoregulatory costs at song posts would increase metabolic rate by an average of 10±4% and a maximum of 25±8% (N=12 birds) relative to birds singing at foraging sites. We estimated that metabolic rate would be 3,8% greater during singing than during quiet respiration because of heat and evaporative water loss in exhaled gases. The combined energy requirements for sound production, thermoregulation at exposed song posts and additional heat loss in exhaled air could increase the metabolic rate of willow warblers by an average of 14,23%, and a maximum of 42,63%, during singing. The energetic cost of singing may thus be much greater for birds in a cold, windy environment than for birds singing in laboratory conditions. [source] The ecological impacts of a migratory bat aggregation on its seasonal roost in Kasanka National Park, ZambiaAFRICAN JOURNAL OF ECOLOGY, Issue 1 2010James W. Byng Abstract The ecological impacts of migratory species on their seasonal environments are poorly known. The effects of several million straw-coloured fruit bats (Eidolon helvum), which migrate seasonally to Kasanka National Park, Zambia each year, on the small area of mushitu,swamp' forest in which they roost, were investigated. The structure of the mushitu forest was profoundly altered by the presence of E. helvum, with increased roost tree mortality, lowering and opening of the forest canopy and a decrease in tree basal area. Eidolon helvum are also thought to increase the severity of fires within their roost site because the structural changes result in a drier microclimate. The effects of increased nitrogen and phosphorous input were less apparent. These findings suggest that the ecological impact of this migratory bat species on its seasonal environment could ultimately threaten the long-term viability of its seasonal roost. Résumé Les impacts écologiques des espèces migratrices sur leurs environnements saisonniers sont peu connus. Les effets de plusieurs millions de roussettes paillées africaines Eidolon helvum qui, chaque année, migrent de façon saisonnière vers le Parc National de Kasanka, en Zambie, furent étudiés dans la petite zone de forêt marécageuse àmushitu où elles se perchent. La structure de la forêt àmushituétait profondément modifiée par la présence d'E. helvum, qui augmentait la mortalité des arbres servant de perchoirs, qui faisait baisser la hauteur et la densité de la canopée et entraînait une diminution de la surface basale des arbres. On pense aussi que la présence d'E. helvum augmente la gravité des feux dans les sites de repos parce que les changements structurels aboutissent à un microclimat plus sec. Les effets de l'apport accru en azote et en phosphore étaient moins apparents. Ces découvertes suggèrent que l'impact écologique de cette espèce de chauve-souris migratrice sur son environnement saisonnier pourrait, à long terme, menacer la viabilité de ses lieux de repos saisonniers. [source] Linkages of plant traits to soil properties and the functioning of temperate grasslandJOURNAL OF ECOLOGY, Issue 5 2010Kate H. Orwin Summary 1.,Global change is likely to alter plant community structure, with consequences for the structure and functioning of the below-ground community and potential feedbacks to climate change. Understanding the mechanisms behind these plant,soil interactions and feedbacks to the Earth-system is therefore crucial. One approach to understanding such mechanisms is to use plant traits as predictors of functioning. 2.,We used a field-based monoculture experiment involving nine grassland species that had been growing on the same base soil for 7 years to test whether leaf, litter and root traits associated with different plant growth strategies can be linked to an extensive range of soil properties relevant to carbon, nitrogen and phosphorus cycling. Soil properties included the biomass and structure of the soil microbial community, soil nutrients, soil microclimate and soil process rates. 3.,Plant species with a high relative growth rate (RGR) were associated with high leaf and litter quality (e.g. low toughness, high nitrogen concentrations), an elevated biomass of bacteria relative to fungi in soil, high rates of soil nitrogen mineralization and concentrations of extractable inorganic nitrogen, and to some extent higher available phosphorus pools. 4.,In contrast to current theory, species with a high RGR and litter quality were associated with soils with a lower rate of soil respiration and slow decomposition rates. This indicates that predicting processes that influence carbon cycling from plant traits may be more complex than predicting processes that influence nitrogen and phosphorus cycling. 5.,Root traits did not show strong relationships to RGR, leaf or litter traits, but were strongly correlated with several soil properties, particularly the biomass of bacteria relative to fungi in soil and measures relating to soil carbon cycling. 6.,Synthesis. Our results indicate that plant species from a single habitat can result in significant divergence in soil properties and functioning when grown in monoculture, and that many of these changes are strongly and predictably linked to variation in plant traits associated with different growth strategies. Traits therefore have the potential to be a powerful tool for understanding the mechanisms behind plant,soil interactions and ecosystem functioning, and for predicting how changes in plant species composition associated with global change will feedback to the Earth-system. [source] Influence of slope and aspect on long-term vegetation change in British chalk grasslandsJOURNAL OF ECOLOGY, Issue 2 2006JONATHAN BENNIE Summary 1,The species composition of fragmented semi-natural grasslands may change over time due to stochastic local extinction and colonization events, successional change and/or as a response to changing management or abiotic conditions. The resistance of vegetation to change may be mediated through the effects of topography (slope and aspect) on soils and microclimate. 2,To assess long-term vegetation change in British chalk grasslands, 92 plots first surveyed by F. H. Perring in 1952,53, and distributed across four climatic regions, were re-surveyed during 2001,03. Changes in vegetation since the original survey were assessed by comparing local colonization and extinction rates at the plot scale, and changes in species frequency at the subplot scale. Vegetation change was quantified using indirect ordination (Detrended Correspondence Analysis; DCA) and Ellenberg indicator values. 3,Across all four regions, there was a significant decrease in species number and a marked decline in stress-tolerant species typical of species-rich calcareous grasslands, both in terms of decreased plot occupancy and decreased frequency within occupied plots. More competitive species typical of mesotrophic grasslands had colonized plots they had not previously occupied, but had not increased significantly in frequency within occupied plots. 4,A significant increase in Ellenberg fertility values, which was highly correlated with the first DCA axis, was found across all regions. The magnitude of change of fertility and moisture values was found to decrease with angle of slope and with a topographic solar radiation index derived from slope and aspect. 5,The observed shift from calcareous grassland towards more mesotrophic grassland communities is consistent with the predicted effects of both habitat fragmentation and nutrient enrichment. It is hypothesized that chalk grassland swards on steeply sloping ground are more resistant to invasion by competitive grass species than those on flatter sites due to phosphorus limitation in shallow minerogenic rendzina soils, and that those with a southerly aspect are more resistant due to increased magnitude and frequency of drought events. [source] Contrasted effects of increased N and CO2 supply on two keystone species in peatland restoration and implications for global changeJOURNAL OF ECOLOGY, Issue 3 2002Edward A. D. Mitchell Summary 1,Significant areas of temperate bogs have been damaged by peat harvesting but may regenerate. These secondary mires, if well managed, may act as strong C sinks, regulate hydrology and buffer regional climate. 2,The potential effects of bog regeneration will, however, depend on the successful establishment of the principal peat formers ,Sphagnum mosses. The influence of hydrology and microclimate on Sphagnum re-growth is well studied but effects of elevated CO2 and N deposition are not known. 3,We carried out two in-situ experiments in a cutover bog during three growing seasons in which we raised either CO2 (to 560 p.p.m.) or N (by adding NH4NO3, 3 g m,2 year,1). The two treatments had contrasting effects on competition between the initial coloniser Polytrichum strictum (favoured by high N) and the later coloniser Sphagnum fallax (favoured by high CO2). 4,Such changes may have important consequences for bog regeneration and hence for carbon sequestration in cutover bogs, with potential feedback on regional hydrological and climatic processes. [source] RING CHARACTERIZATION OF QUALITY INDICES IN BUTTERHEAD LETTUCE CULTIVATED UNDER MULCH AND BARE SOILJOURNAL OF FOOD QUALITY, Issue 4 2010MARÍA G. GOÑI ABSTRACT Butterhead lettuce was characterized by physical, microbiological and nutritional quality indices as a function of plant zoning and soil management (bare soil and mulch). Quality indices were measured in all the rings from the external toward the internal ratio. Assayed indices were: relative water content, water content, free and bound water, and the ratio between free water and total water, leaf area and color, total microbial counts (TMC) and ascorbic acid content (AA). The lettuce characterization by rings showed a remarkable plant zoning as a function of leaf age and development; also, some initial indices were affected by the soil management employed. Plastic mulches affect the microclimate around the plant, resulting in better plant water status. However, the use of black plastic covers could absorb sunlight therefore increasing soil temperature and causing lower AA and higher TMC in lettuce tissue. PRACTICAL APPLICATIONS During lettuce development, each leaf had a different level of exposure to environmental conditions, such as light, humidity, nutrients absorption and temperature affecting the quality indices of the raw material and introducing a source of variability in the physico-chemical, biochemical, nutritional and microbiological indices within the plant. In this way, the location of the leaf within the whole plant is an important factor to be considered. Moreover, during lettuce heads trading, it is a common practice to remove the external leaves as storage advances. These leaves are more perishable than middle and internal ones because of their direct exposure to environmental conditions. Understanding the way in which physical, microbiological and nutritional indices were distributed in the whole lettuce plant could be of interest, to know the value of the losses of regular green grocers' practices, from a nutritional and a safety point of view. [source] Holocene solifluction, climate variation and fire in a subarctic landscape at Pippokangas, Finnish Lapland, based on radiocarbon-dated buried charcoal,JOURNAL OF QUATERNARY SCIENCE, Issue 6 2005John A. Matthews Abstract A large number of radiocarbon dates from charcoal layers buried beneath stacked solifluction lobes at Pippokangas, in the northern boreal zone of Finnish Lapland, are used to reconstruct a Holocene history of solifluction. Although the site is surrounded by Scots pine forest, the solifluction lobes occur on the lower slopes of a kettle hole, the microclimate of which prevents the growth of trees. Samples from the upslope end of charcoal layers have enabled the recognition of four synchronous phases of solifluction lobe initiation: 7400,6700, 4200,3400, 2600,2100 and 1500,500,cal.,yr,BP. Rates of lobe advance are shown to be lobe-dependent and age-dependent: initially, average rates were commonly 0.14,0.19,cm yr,1, later falling to 0.02,0.07,cm,yr,1 or less as the lobes approached the bottom of the slope. The absence of charcoal prior to 8000,cal.,yr,BP, together with single IRSL and TL dates, indicate a relatively stable early Holocene landscape. The onset of solifluction around 7400,cal.,yr,BP. appears to have followed the immigration of pine around the site, which increased the frequency of forest fires. Phases of solifluction activity seem to have been triggered by millennial-scale variations in effective moisture (the climatic hypothesis), rather than episodic burning of the surface vegetation cover (the geoecological hypothesis), although climate may also have affected fire frequency and severity. Copyright © 2005 John Wiley & Sons, Ltd. [source] Spatial pattern and neighbour effects on Helianthemum squamatum seedlings in a Mediterranean gypsum communityJOURNAL OF VEGETATION SCIENCE, Issue 4 2005Adrián Escudero Abstract Question: Do, in a semi-arid gypsum environment, neighbours condition the spatial patterns of emergence, survival and height of Helianthemum squamatum seedlings? Location: Vicinity of Chinchón, province of Madrid, Spain (40°11,N, 3° 35,W, 550 m a.s.l.) Methods: We evaluated the effects of neighbours on the survival and growth of naturally emerging Helianthemum seedlings in a semi-arid area during a two-year period. We followed a two-fold approach based on the use of neighbour models for seedling survival and growth and spatial point pattern analyses for seedling emergence, taking into account the germination date. Results: Seedlings appeared clumped in the vicinity of mature Helianthemum individuals. The neighbour models fitted showed that interactions with neighbours were extremely important for the survival and growth of Helianthemum seedlings. These models also suggest that the effects of neighbours on these variables vary with changes in spatial scale and in the abiotic conditions. Some species exerted negative or positive effects on Helianthemum seedlings only at certain spatial scales, and others exerted negative or positive effects at earlier stages of seedling development, but none later and vice versa. Conclusions: We suggest that the observed patterns are mainly influenced by small-scale modifications in soil conditions and microclimate created by neighbours, which change in time and space. [source] Geographic variation in the use of torpor and roosting behaviour of female western long-eared batsJOURNAL OF ZOOLOGY, Issue 4 2007D. I. Solick Abstract The costs and benefits of torpor may vary across the range of widespread heterothermic species, resulting in different thermoregulatory patterns and other behaviours for individuals inhabiting different environments. We compared torpor use and roosting behaviour for rock-roosting populations of western long-eared bats Myotis evotis living in the mountains and prairies of Alberta, Canada. We monitored body temperatures and located roosts for pregnant and lactating females using radio-telemetry. We also took roost measurements, and assessed roost microclimate using temperature dataloggers. Females in the mountains entered torpor less frequently and spent less time in torpor than bats in the prairies, supporting our hypothesis that reproductive time constraints in the mountains outweigh the benefits of torpor. Alternatively, increased torpor use in the prairies may be attributed to a greater need for water conservation. Females in the mountains minimized thermoregulatory costs and maintained homeothermy by selecting exposed roosts with warm microclimates during pregnancy, and then switching to clustering with other individuals during lactation when conditions were cooler. In the prairies, females roosted alone in cooler, less exposed roost types, which facilitate the use of torpor. Our results illustrate the importance of considering geographic variation in behaviour across the range of a species. [source] Thermoregulation and roost selection by reproductive female big brown bats (Eptesicus fuscus) roosting in rock crevicesJOURNAL OF ZOOLOGY, Issue 3 2003Cori L. Lausen A free-ranging maternity colony of big brown bats Eptesicus fuscus roosting in rock crevices along the South Saskatchewan River in south-eastern Alberta, Canada, was studied to understand better the discrepancy that exists in the literature regarding torpor use by reproductive female bats. Using radio-telemetry, thermoregulatory patterns and roost microclimate were recorded for pregnant, lactating and post-lactating females. Relative torpor use is described in several ways: the proportion of days on which torpor was used, depth, minimum body temperature, time spent in torpor, and a comprehensive torpor unit (degree-min). Pregnant and lactating female E. fuscus used torpor to the same extent overall (degree-min), but pregnant bats used torpor less frequently and with more time in deep torpor. Torpor was used to the greatest extent after weaning (post-lactation). Evidence is presented that the cost:benefit ratio for deep and prolonged periods of torpor may be highest during lactation. Microclimates of rock-crevice roosts mirrored the use of torpor throughout reproduction by bats. Lactation roosts (deeper, larger opening size) were more thermally stable and remained warmer at night compared to the shallow roosts used by pregnant and post-lactating females. It is shown that conclusions about relative use of torpor can differ depending on the units of comparison, necessitating measurement of all aspects of torpor (depth, duration and frequency). Comprehensive measurements, individual-based normothermic temperatures, and a definition of torpor that accounts for all energy savings, allow a more accurate depiction of patterns and facilitates inter-study comparisons. [source] Predicting moisture dynamics of fine understory fuels in a moist tropical rainforest system: results of a pilot study undertaken to identify proxy variables useful for rating fire dangerNEW PHYTOLOGIST, Issue 3 2010David Ray Summary ,The use of fire as a land management tool in the moist tropics often has the unintended consequence of degrading adjacent forest, particularly during severe droughts. Reliable models of fire danger are needed to help mitigate these impacts. ,Here, we studied the moisture dynamics of fine understory fuels in the east-central Brazilian Amazon during the 2003 dry season. Drying stations established under varying amounts of canopy cover (leaf area index (LAI) = 0 , 5.3) were subjected to a range of water inputs (5,15 mm) and models were developed to forecast litter moisture content (LMC). Predictions were then compared with independent field data. ,A multiple linear regression relating litter moisture content to forest structure (LAI), ambient vapor pressure deficit (VPDM) and an index of elapsed time since a precipitation event (d,1) was identified as the best-fit model (adjusted R2 = 0.89). Relative to the independent observations, model predictions were relatively unbiased when the LMC was , 50%, but consistently underestimated the LMC when the observed values were higher. ,The approach to predicting fire danger based on forest structure and meteorological variables is promising; however, additional information to the LAI, for example forest biomass, may be required to accurately capture the influence of forest structure on understory microclimate. [source] | |||||||||||||||||||||||||||||||||||||