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Freshwater ecosystems are positioned at low levels in the landscape and receive large inputs of diverse plant-based detritus, a major source of energy for consumers in aquatic ecosystems. We conducted field experiments in Urbana, ...
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Freshwater ecosystems are positioned at low levels in the landscape and receive large inputs of diverse plant-based detritus, a major source of energy for consumers in aquatic ecosystems. We conducted field experiments in Urbana, IL to determine the independent and combined effects of leaves of common tree species including the northern red oak (Quercus rubra L.), sugar maple (Acer saccharum Marshall), and common hackberry (Celtis occidentalis L.) on the performance of container-dwelling mosquitoes, especially Culex restuans Theobald (Diptera: Culicidae). We tested the hypothesis that leaf species have asymmetric effects on adult mosquito production and longevity. Hackberry followed by combined leaf treatments and maple produced the greatest number of pupae, whereas oak leaves produced the fewest. Leaf treatments had no significant effects on adult female sizes but female longevity was significantly lower in oak leaf treatments compared with the other leaf treatments. These findings support the hypothesis that leaf species identity influences the performance of container-dwelling mosquitoes with potential consequences for the transmission of infectious diseases.
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Ecological restoration of eutrophic lakes using aquatic macrophytes is an important and practical technology. Here, we investigated the response of phytoplankton and zooplankton to a large-scale 2015-built aquatic macrophyte enclo...
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Ecological restoration of eutrophic lakes using aquatic macrophytes is an important and practical technology. Here, we investigated the response of phytoplankton and zooplankton to a large-scale 2015-built aquatic macrophyte enclosure (AME, 200,000 m2) screened of by a PVC net in Baima Lake, a eutrophic lake, from spring to autumn of 2019. AME significantly improved water quality by increasing water transparency, and reducing total nitrogen, total phosphorus, and chlorophyll-a content during the growing season. AME significantly decreased phytoplankton abundance and biomass and marginally increased zooplankton abundance and biomass. Phytoplankton and zooplankton communities were closely related to environmental factors, such as water temperature, conductivity, total phosphorus, chemical oxygen demand, and chlorophyll-a inside and outside the AME. The zooplankton:phytoplankton biomass ratio inside was slightly higher than outside the AME. Zooplankton and phytoplankton biomass were significantly positively correlated inside and outside the AME, as were chlorophyll-a and total phosphorus. We found phosphorus to be a key factor limiting primary productivity in Baima Lake, and that bottom-up effects were the main driver to control phytoplankton in the AME. Using aquatic macrophytes to reduce nutrient loads is an effective way to manage eutrophication in Baima Lake.
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Changes in plant community structure and composition of the Mojave Desert in response to greater fire intensity and extent are likely to have strong bottom-up effects on the biological community. The objective of this study was to...
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Changes in plant community structure and composition of the Mojave Desert in response to greater fire intensity and extent are likely to have strong bottom-up effects on the biological community. The objective of this study was to determine how expansive fire in Mojave Desert impacts small mammal communities across seasons. We sampled small mammals in paired burned (4—5 years post-fire) and unbumed areas of Beaver Dam Wash in southwestern Utah. Fire reduced total abundance of small mammals, and species richness and species diversity of the small mammal community. Merriam's kangaroo rat (Dipodomys merriami) responded positively to fire (15% greater in burned areas). Long-tailed pocket mouse (Chaetodipus formosus) and canyon mouse (Peromyscus crinitus) were 91% and 98% less abundant in burned versus unburned areas. The positive response of Merriam's kangaroo rat to fire is most likely correlated with their preference for open foraging microhabitat while other species captured prefer greater and more diverse cover. Because the small mammal community has been dramatically affected by fire, it is likely that top-down control of vegetation structure will be dominated by Merriam's kangaroo rat in burned areas, which may promote more open habitat by limiting the growth of annual and perennial grasses.
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Bottom-up filling of copper for different sub-micrometer trenches was investigated by electroless deposition technique using Janus Green B (JGB) and Triblock copolymers RPE-2520. The bottom-up copper filling usually achieves a rel...
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Bottom-up filling of copper for different sub-micrometer trenches was investigated by electroless deposition technique using Janus Green B (JGB) and Triblock copolymers RPE-2520. The bottom-up copper filling usually achieves a relative high deposition rate of copper in the bottom of trenches through inhibiting the surface deposition or accelerating the bottom deposition of copper. The bottom-up filling behavior of electroless copper deposition for different trenches was investigated in a plating bath containing 0.3 mg/L JGB and 1.0 mg/L RPE-2520. The cross-section image with SEM indicated that the trenches with different widths ranging from 110 to 520 nm were completely filled with electroless copper and that no void was found.
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It is becoming increasingly appreciated that the structure and functioning of ecological food webs are controlled by the nature and level of plant chemicals. It is hypothesized that intraspecific variation in plant chemical resist...
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It is becoming increasingly appreciated that the structure and functioning of ecological food webs are controlled by the nature and level of plant chemicals. It is hypothesized that intraspecific variation in plant chemical resistance, in which individuals of a host-plant population exhibit genetic differences in their chemical contents (called 'plant chemotypes'), may be an important determinant of variation in food web structure and functioning. We evaluated this hypothesis using field assessments and plant chemical assays in the tansy plant Tanacetum vulgare L. (Asteraceae). We examined food webs in which chemotypes of tansy plants are the resource for two specialized aphids, their predators and mutualistic ants. The density of the ant-tended aphid Metopeurum fuscoviride was significantly higher on particular chemotypes (borneol) than others. Clear chemotype preferences between predators were also detected. Aphid specialist seven-spotted ladybird beetles (Coccinella septempunctata) were more often found on camphor plants, while significantly higher numbers of the polyphagous nursery web spider (Pisaura mirabilis) were observed on borneol plants. The analysis of plant chemotype effects on the arthropod community clearly demonstrates a range of possible outcomes between plant-aphid-predator networks. The findings help to offer a deeper insight into how one important factor-plant chemical content-influences which species coexist within a food web on a particular host plant and the nature of their trophic linkages.
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We use a 31 year dataset to assess the effects of resources (rainfall, soil, relief) and disturbance (cattle browsing and fire) on regeneration and growth in a long-lived tree Acacia peuce from arid inland Australia. Temporal and ...
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We use a 31 year dataset to assess the effects of resources (rainfall, soil, relief) and disturbance (cattle browsing and fire) on regeneration and growth in a long-lived tree Acacia peuce from arid inland Australia. Temporal and spatial resource availability had an overwhelming effect on recruitment and stand density; but cattle browsing and fire limited sapling growth and stand persistence, respectively. Seedling establishment over the 31 years was effectively confined to a single prolonged high rainfall phase. Cattle browsing in productive (run-on) patches kept saplings short; while long-fenced and low cattle-use (run-off) patches provided spatial escape opportunities for sapling growth. Fire caused the death of standing plants, but it did not stimulate recruitment, and was therefore an additional limiting factor for stand persistence. Our study provided further support for the central role of prolonged large rainfall events for regeneration in long-lived arid trees, but it also emphasised how disturbance can strongly limit stand regeneration. Overall, we expect that desert trees such as Acacia peuce that are characterised by slow population dynamics will be adversely affected by climate change due to increasingly rare recruitment. Minimisation of disturbance factors will be an increasingly important requirement for the long-term persistence of this species.
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Herbicides are well known for unintended effects on freshwater periphyton communities. Large knowledge gaps, however, exist regarding indirect herbicide impacts on primary consumers through changes in the quality of periphyton as ...
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Herbicides are well known for unintended effects on freshwater periphyton communities. Large knowledge gaps, however, exist regarding indirect herbicide impacts on primary consumers through changes in the quality of periphyton as a food source (i.e., diet-related effects). To address this gap, the grazer Physella acuta (Gastropoda) was fed for 21 days with periphyton that grew for IS days in the presence or absence of the herbicide diuron (8 μg/L) to quantity changes in the feeding rate, growth rate, and energy storage (neutral lipid fatty acids; NLFAs) of P. acuta. Periphyton biomass, cell viability, community structure, and FAs served as proxies for food quality that support a mechanistic interpretation of the grazers' responses. Diuron changed the algae periphyton community and fatty acid profiles, indicating alterations in the food quality, which could explain differences in the snails' feeding rate compared to the control. While the snails' growth rate was, despite an effect size of 55%, not statistically significantly changed, NLFA profiles of P. acuta were altered. These results indicate that herbicides can change the food quality of periphyton by shifts in the algae composition, which may affect the physiology of grazers.
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Multiple human disturbances influence the vegetation, ungulates and Amur tigers (Panthera tigris altaica) in Hunchun Nature Reserve (HNR) in northeastern China. In order to understand the influence and relative contribution of hum...
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Multiple human disturbances influence the vegetation, ungulates and Amur tigers (Panthera tigris altaica) in Hunchun Nature Reserve (HNR) in northeastern China. In order to understand the influence and relative contribution of human disturbance on Amur tigers, prey and vegetation, we conducted the transect lines and plot surveys of human disturbance inside HNR from August to October 2013. We used generalized additive models, generalized liner models and structural equation models to explore the effects of human disturbance on vegetation, prey and Amur tigers. We then used hierarchical partitioning models to quantify the contribution of four main kinds of human disturbance. Our results suggest that all three models indicate that human disturbance can directly and indirectly affect prey and Amur tigers via the Bottom Up chains. Among the human disturbances, grazing activity and ginseng land encroachment impacted vegetation more than roads did; for prey, secondary roads had the greatest impact. Grazing activity, secondary roads and primary roads were the main factors disturbing Amur tigers. The generalized additive model had a stronger detection ability for disturbance prediction than generalized liner and structural equation models. The generalized additive model detected more complex nonlinear interaction relationships between predator and prey or predator, prey and habitat factors. Reducing or eliminating specific types of disturbance will be essential to recover Amur tiger populations and their habitats. (C) 2016 Elsevier B.V. All rights reserved.
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A variety of theories has been developed explaining attention and decision-making. Most studies in this field, which combine eye-tracking and conjoint analysis, use a top-down experimental situation, in which the participant is fo...
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A variety of theories has been developed explaining attention and decision-making. Most studies in this field, which combine eye-tracking and conjoint analysis, use a top-down experimental situation, in which the participant is forced to make a decision. The aim of the present study was to combine a bottom-up aspect, using eye-tracking in which the participant is not forced to make a decision, and a quasi-experiment (choice-based conjoint analysis) to investigate whether the reviewed theories could also predict the results in a bottom-up, top-down situation. Seventeen subjects participated in the experiment in December 2016, investigating visual attention and choice in the case of tomatoes with product characteristics such as price, label, and origin. The results of the study show no significant relationship between visual attention and choice, when not in a top-down situation. A combination of methods and bottom-up situations as well as top-down situations when investigating attention and choice is suggested as demonstrated by this study. The results of this study do not support the popular utility effect theory that assumes a strong relationship between attention and utility.
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Soil macrofauna is an important indicator of soil quality, as it is sensitive to changes in the environment as a result of soil management, which includes soil chemical and physical properties and the diversity of cultivated speci...
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Soil macrofauna is an important indicator of soil quality, as it is sensitive to changes in the environment as a result of soil management, which includes soil chemical and physical properties and the diversity of cultivated species. This study aimed to evaluate the composition and structure of soil macrofauna under a no-tillage system in different crop sequences, with and without crop rotation, over two growing seasons: a rainy summer and a dry winter. The crop sequences were soybean/corn rotation in the summer and corn in the winter; soybean/corn rotation in the summer and sunn hemp in the winter; soybean monoculture in the summer and sunn hemp in the winter; and corn monoculture in the summer and corn monoculture in the winter growing season. The nutrient content of the crop residues left on the soil surface, soil chemical and physical properties, and soil macrofauna were determined. Functional plant groups (grasses or legumes) individually influenced the composition of soil macrofauna more significantly than the effect of crop sequence, with or without rotation, and growing season. Grasses favored an increased density of groups such as Oligochaeta, Isoptera, and Formicidae. In contrast, legumes contributed to the variation in the total density of individuals and Diplura and Coleoptera groups. Furthermore, the influence of functional plant groups (grasses or legumes) on the composition and density of soil macrofauna were related to soil chemical (P and N content) and physical properties (particulate organic carbon and soil moisture), which determined the composition of soil macrofauna groups.
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