Effects Of Multiple Environmental Factors Research Articles

Experimental beetle metapopulations respond positively to dynamic landscapes and reduced connectivity.

Interactive effects of multiple environmental factors on metapopulation dynamics have received scant attention. We designed a laboratory study to test hypotheses regarding interactive effects of factors affecting the metapopulation dynamics of red flour beetle, Tribolium castaneum. Within a four-patch landscape we modified resource level (constant and diminishing), patch connectivity (high and low) and patch configuration (static and dynamic) to conduct a 23 factorial experiment, consisting of 8 metapopulations, each with 3 replicates. For comparison, two control populations consisting of isolated and static subpopulations were provided with resources at constant or diminishing levels. Longitudinal data from 22 tri-weekly counts of beetle abundance were analyzed using Bayesian Poisson generalized linear mixed models to estimate additive and interactive effects of factors affecting abundance. Constant resource levels, low connectivity and dynamic patches yielded greater levels of adult beetle abundance. For a given resource level, frequency of colonization exceeded extinction in landscapes with dynamic patches when connectivity was low, thereby promoting greater patch occupancy. Negative density dependence of pupae on adults occurred and was stronger in landscapes with low connectivity and constant resources; these metapopulations also demonstrated greatest stability. Metapopulations in control landscapes went extinct quickly, denoting lower persistence than comparable landscapes with low connectivity. When landscape carrying capacity was constant, habitat destruction coupled with low connectivity created asynchronous local dynamics and refugia within which cannibalism of pupae was reduced. Increasing connectivity may be counter-productive and habitat destruction/recreation may be beneficial to species in some contexts.

Ecological correlates and determinants in the geographical variation of deer morphology

Previous studies on patterns in ungulate size variations have emphasized the effect of a particular environmental factor such as Bergmann's rule and the island rule. However, although multiple environmental factors may influence the body size, these studies focused on a single factor, and various measurements that may be influenced by different environmental factors (at least partly) were used as indices of body size. In this study, we used several skull and limb measurements to examine size variations among island populations of sika deer (Cervus nippon) in southern Japan considering the effects of multiple environmental factors. We found that all measurements differed markedly between populations. We focused on the skull and limb condylobasal length (CBL) and metacarpal length because they had the most important variations among the populations and the largest sample sizes. The common environmental factors influencing CBL and metacarpal length were island area and precipitation. Since these environmental factors reflect the availability of food resources, the causal factor of body size variation may be food resources. Interpopulation variation in metacarpal length was greater than that of CBL, indicating that metacarpal length may be affected by additional factors besides the common factors shared with CBL. Specific environmental factors influencing relative (CBL adjusted) metacarpal length were precipitation and slope. A common direct cause of those environmental factors was discussed in relation to topography. Analyses of phenotypic variation using multiple measurements with multiple environmental factors are useful to gain insight into underlying causes and can lead to identification of a measurement-specific variation with a specific driving force.

A Post-hoc Analysis of the Combined Effect of Multiple Environmental Factors in Daylighting Design

A Post-hoc Analysis of the Combined Effect of Multiple Environmental Factors in Daylighting Design

China's terrestrial carbon balance: Contributions from multiple global change factors

[1] The magnitude, spatial, and temporal patterns of the terrestrial carbon sink and the underlying mechanisms remain uncertain and need to be investigated. China is important in determining the global carbon balance in terms of both carbon emission and carbon uptake. Of particular importance to climate-change policy and carbon management is the ability to evaluate the relative contributions of multiple environmental factors to net carbon source and sink in China's terrestrial ecosystems. Here the effects of multiple environmental factors (climate, atmospheric CO2, ozone pollution, nitrogen deposition, nitrogen fertilizer application, and land cover/land use change) on net carbon balance in terrestrial ecosystems of China for the period 1961–2005 were modeled with newly developed, detailed historical information of these changes. For this period, results from two models indicated a mean land sink of 0.21 Pg C per year, with a multimodel range from 0.18 to 0.24 Pg C per year. The models' results are consistent with field observations and national inventory data and provide insights into the biogeochemical mechanisms responsible for the carbon sink in China's land ecosystems. In the simulations, nitrogen deposition and fertilizer applications together accounted for 61 percent of the net carbon storage in China's land ecosystems in recent decades, with atmospheric CO2 increases and land use also functioning to stimulate carbon storage. The size of the modeled carbon sink over the period 1961–2005 was reduced by both ozone pollution and climate change. The modeled carbon sink in response to per unit nitrogen deposition shows a leveling off or a decline in some areas in recent years, although the nitrogen input levels have continued to increase.

Stressed crops emit more methane despite the mitigating effects of elevated carbon dioxide.

Recent studies using single environmental variables show that under aerobic conditions terrestrial plants can emit methane (CH4). However, the effects of multiple environmental factors - as components of global climate change - on aerobic CH4 emissions have been little studied. We examined the combined effects of temperature, carbon dioxide (CO2) and watering regime on CH4 emissions from six commonly cultivated crop species: faba bean, sunflower, pea, canola, barley and wheat. Plants were grown from seeds in controlled-environment growth chambers under two temperature regimes (24°C day/20°C night and 30°C day/26°C night), two CO2 concentrations (380 and 760µmolmol-1) and two watering regimes (well watered and water stressed). Plants were grown first under 24/20°C for 1 week from sowing, and then placed under experimental conditions for a further week. After the specified time, plant growth, gas exchange and CH4 emission rates were determined. Our results revealed that higher temperature and water stress significantly enhance CH4 emissions from plants, whereas elevated CO2 had the opposite effect and partially reverses the promotive effects of these factors. We suggest that the despite the mitigating effects of rising atmospheric CO2, CH4 emission may be higher in the face of ongoing global climate change in warmer and drier environments.

Hypoxia drives plastic divergence in cichlid body shape

Organisms experience multiple selective agents that can influence phenotypes through heritable and/or plastic changes, often reflecting complex interactions between phenotype and environment. Environmental factors can directly influence phenotypes, but also indirectly affect phenotypic variation when genetic/plastic change in one trait results in correlated genetic/plastic change in another trait. In fishes, body shape is a trait that might be particularly prone to influence from environmental pressures that act on other morphological features. Variation in dissolved oxygen among aquatic environments has a large impact on the size of the gills and brains of fishes. It is likely that dissolved oxygen interacts with other environmental factors to both directly and indirectly influence patterns of body shape variation. We examined effects of dissolved oxygen on body shape variation among populations of an African cichlid fish (Pseudocrenilabrus multicolor) from multiple high- and low-oxygen sites within a single drainage in Uganda. A split-brood laboratory experiment was used to estimate plasticity of gill and brain size, and we used morphometric analyses to identify variation in body shape in F1 offspring. Several analyses enabled us to identify genetic effects among populations, and effects of oxygen acting either directly on body shape or indirectly through its effects on gill and brain size. A large part of the variation in body shape was due to plastic variation in gill size associated with dissolved oxygen. Fish raised under low oxygen had deeper heads and shorter bodies, and this variation was driven by both direct effects of oxygen and indirect effects of gill size variation. Body shape variation in fishes should reflect interacting effects of multiple environmental factors that act directly or indirectly on morphology. Body shape might be particularly difficult to predict when phenotypes are plastic, because changes among populations would occur rapidly and be unrelated to genetic variation.

Combined Effects of Temperature, Ultraviolet‐B Radiation, and Watering Regime on Growth and Physiological Processes in Canola (Brassica napus) Seedlings

Relatively few studies have investigated plant responses to the combined effects of multiple environmental factors. We studied the responses of canola (Brassica napus) seedlings to combinations of temperatures (22°/18°C and 28°/24°C), ultraviolet‐B (UVB) radiation levels (5 [ambient] and 10 [enhanced] kJ m−2 d−1), and watering regimes (well watered and water stressed). The higher temperature decreased stem diameter, leaf area, individual organ and total‐plant dry mass (DM), net CO2 assimilation (AN), water use efficiency (WUE), the chlorophyll (Chl) a–Chl b ratio, and UV‐absorbing compounds but increased specific leaf mass (SLM), leaf mass ratio (LMR), shoot‐root ratio (SRR), and Chl b. Enhanced UVB reduced leaf number and area, DM accumulation, SLM, LMR, AN, WUE, carotenoids, and Chl a:Chl b but increased leaf area ratio, SRR, and ethylene evolution. Water stress decreased plant growth, leaf moisture, leaf, stem, and total DM, LMR, SRR, and gas exchange but increased photosynthetic pigments, UV‐absorbing...

Footprints in the Oceans

SYSTEMS BIOLOGY Laboratory research works well in identifying the responses of individual organisms to a series of environmental changes; it is rather more difficult, however, to carry out analogous studies of how community structure and function are influenced by the environment and by interactions among ecosystem residents. Gianoulis et al. have documented the metabolic adaptations of microbial communities using metagenomic data culled from the Global Ocean Survey, which has sampled sites in the Atlantic and Pacific Oceans. Analytical approaches enabled them to examine the effects of multiple environmental factors (including temperature, salinity, sample depth, and average chlorophyll content) on metabolic pathways. Some pathways were associated with particular environments, providing what could be called a metabolic footprint. In contrast, some amino acid biosynthetic pathways varied with the environment, yet others did not. Rather than reflecting the energetic potential of the environment, this variation may indicate the presence or absence of valuable metals, such as cobalt, that are used to make catalytic cofactors. Potentially, metabolic footprints might be used as sensitive detectors of environmental change. — BJ Proc. Natl. Acad. Sci. U.S.A. 106 , 1374 (2009).

Growth and condition of 0-group European flounder, Platichthys flesus as indicator of estuarine habitat quality

The purpose of this present study was to use the growth rates, RNA–DNA ratio and morphometric (Fulton’s K) condition indices measured on 0-group juveniles European flounder, as a means of comparing the quality of estuarine nursery habitats. The Seine estuary, heavily impacted by manmade modifications and one of the most contaminated in Europe, was compared to two smaller estuaries considered as clean (low domestic, agricultural and industrial effluents). Indicators of human disturbance (sediment chemical contaminants) as well as biotic data (macrobenthos abundances) were used to establish between-site differences in environmental quality. The abundance of macrobenthos (potential preys for juvenile) was high and not significantly different among the three estuaries confirming the important role played by estuaries as feeding grounds. Sediment metal concentrations (Cd, Cr, Cu, Pb, Zn) were significantly higher in the Seine than in the Canche and Authie estuaries. Otolith growth was closely related to somatic fish growth, and we used daily otolith increments from the previous 10 days before capture as an indicator of 0-group flounder recent growth (RG). RG did not vary significantly among flounders from the Canche and Authie estuaries and individuals from the Seine had slower RG. RNA–DNA ratio and K values were also significantly lower in individuals from the Seine compared to those of the Authie or the Canche. Pollution (e.g. metal contaminants) is the most likely cause of growth and condition differences among estuaries. The results of this study suggest that habitat-specific fish growth and condition are useful proxies for habitat quality since they integrate the effect of multiple environmental factors.

Modeling of wind and temperature effects on modal frequencies and analysis of relative strength of effect

Wind and temperature have been shown to be the critical sources causing changes in the modal properties of large-scale bridges. While the individual effects of wind and temperature on modal variability have been widely studied, the investigation about the effects of multiple environmental factors on structural modal properties was scarcely reported. This paper addresses the modeling of the simultaneous effects of wind and temperature on the modal frequencies of an instrumented cable-stayed bridge. Making use of the long-term monitoring data from anemometers, temperature sensors and accelerometers, a neural network model is formulated to correlate the modal frequency of each vibration mode with wind speed and temperature simultaneously. Research efforts have been made on enhancing the prediction capability of the neural network model through optimal selection of the number of hidden nodes and an analysis of relative strength of effect (RSE) for input reconstruction. The generalization performance of the formulated model is verified with a set of new testing data that have not been used in formulating the model. It is shown that using the significant components of wind speeds and temperatures rather than the whole measurement components as input to neural network can enhance the prediction capability. For the fundamental mode of the bridge investigated, wind and temperature together apply an overall negative action on the modal frequency, and the change in wind condition contributes less to the modal variability than the change in temperature.

Amphibian declines: future directions

Abstract.The amphibian decline problem is complex, and there is no easy solution. I highlight four major areas of future research that should increase our ability to detect declines, elucidate their underlying mechanisms, and advance our capacity to manage and conserve amphibian populations. First, a statistically sensitive monitoring approach is necessary to determine the distribution and abundance of amphibian populations, to assess whether they are declining, and to quantify the extent of declines. Most amphibian populations characteristically fluctuate, detection probabilities may be low for many species and populations tend to decline in numbers between years more often than they increase. These traits make establishing monitoring programmes difficult and distinguishing declines from natural fluctuations challenging. It is thus necessary to determine the best monitoring techniques based on their statistical power and to use appropriate statistical methods for detecting population trends. Secondly, although amphibian population studies occur most commonly at single or few breeding sites, research should occur often at the landscape level, and conservation efforts should focus on suitable habitat (whether or not it is occupied) and dispersal capabilities of species. Metapopulation dynamics are probably important for many species, but we must be cautious how we define metapopulations. That is, the term ‘metapopulation’ is currently used to define a wide range of demographic situations in amphibian populations, each with different management implications. Thirdly, recent advances in molecular genetic techniques make it possible to infer demographic events such as effects of recent fragmentation, bottlenecks or hybridization. Molecular techniques can be used in conjunction with census surveys to bolster knowledge about demographic processes such as declines. Alternatively, in the absence of long‐term census data, molecular data can be used to infer population trends. New genomic approaches may make estimating adaptive genetic variation more feasible. Fourthly, multi‐factorial studies are needed to disentangle the complexity of the several putative causes that probably interact to cause amphibian declines. Recent studies demonstrate the value of a multi‐factorial approach, and more work is needed to elucidate the synergistic effects of multiple environmental factors affecting amphibian populations simultaneously worldwide.

環境評価点を用いた銀の大気腐食に対する寿命評価

Atmospheric corrosion test data for silver were analyzed which were obtained in various sites in Japan. A new corrosion life assessment method was developed. The method took into account the interactive effect of multiple environmental factors on the decrease in metal weight during corrosion tests. The simple and practically useful formula for corrosion life prediction was established in terms of environmental indices and the formula could enable the evaluation of time dependent loss of metal weight based on the environmental assessment.

Survival of the hermit crab, Clibanarius vittatus, exposed to selenium and other environmental factors.

Recent investigations of water quality criteria have frequently examined the effects of a pollutant; however, a more realistic investigation would consider effects of multiple environmental factors and their interactions with the pollutant. Awareness of selenium as a pollutant is increasing. The growing sulfur and petroleum industries are only two of the potential sources of the element on the Texas coast. Geologically, selenium occurs widely and can enter the environment via the weathering of rocks and soils (NAS 1976). The element may also enter the environment as a result of the combustion of fossil fuels (Fleming et at. 1979; Bertine & Goldberg 1971; Gutenmann and Bache 1976). It can also be a runoff contaminant from soil dressing containing selenium in selenium deficient areas (GisselNielson and Gissel-Nielson 1973). Since selenium tends to accumulate in sediments (Sidelnikova 1970), dredging operations might also increase available selenium in the marine environment.