Allometric scaling of resource acquisition by ruminants in dynamic and heterogeneous environments

We present a mechanistic formulation of the intake response of ruminants to vegetation biomass based solely on physiological and morphological parameters that scale allometrically with the animal's body mass. The model is applied to describe herbivore-vegetation interactions in dynamic and heterogeneous landscapes with low quality but abundant “tall grass” and high quality but sparsely available “short grass”, under two conditions: “uncoupled” (such that the effect of food intake on vegetation biomass can be neglected), or “coupled” (such that the vegetation biomass is determined by herbivore feeding). The results show that under uncoupled conditions, the minimum acceptance (proportion of vegetation consumed by the herbivore) at which the herbivore can leave its current patch without reducing its intake rate is when it has depleted the current patch by the energetic cost required to travel to another patch. The maximum acceptance at which the herbivore should leave its patch is when it has depleted the current patch by the cumulative energetic cost of traveling, handling, cropping, and digesting. Under coupled conditions, the optimal acceptance equals half the relative growth rate of the vegetation. Analytical solutions are obtained for equilibrium values for utilization of the vegetation, and for the densities of vegetation and ruminants, expressed in physiological and morphological herbivore parameters.     

Primary productivity and the flux of dissolved organic matter in several marine environments

Primary productivity and the flux of DO¹⁴C, dissolved saccharides (DSAC) and dissolved free primary amines (DFPA) were followed in the Sargasso Sea, Caribbean and upwelling waters of Peru. Average carbon fixation rates were 42.8, 292.8 and 4791.6 mg C m^-2 d^-1, respectively, with nocturnal respiration rates ranging from 9.8–16.3% of gross photosynthesis for the 3 areas. The release of DO¹⁴C, as a percentage of the total carbon fixed in photosynthesis, was non-detectable in the Sargasso Sea, and 3.2 and 4.4% for the Caribbean and Peruvian phytoplankton communities. Few significant changes in DSAC concentrations were recorded over a 36-h incubation period in the Sargasso Sea and Caribbean stations, whereas light-dependent accumulations of DSAC and DFPA were noted in Peruvian stations which were strongly correlated with total phytoplankton productivity. In the Peruvian stations, the average accumulation rate was 234 mg DSAC-C m^-2h^-1 while the average rate of nocturnal decomposition was 141 mg DSAC-C m^-2h^-1; diurnal and nocturnal rates of DFPA accumulation and decomposition were similar (2 mg DFPA-C m^-2h^-1). These data were used to calculate bacterial production in the upwelling waters of Peru. A general discussion of ¹⁴C-technique and routine analytical techniques for DSAC analysis is presented, as DSAC flux exceeded DO¹⁴C flux by 17-fold in coastal Peruvian stations.     

Gridded meteorological data as a resource for mechanistic macroecology in coastal environments

Gridded weather data were evaluated as sources of forcing variables for biophysical models of intertidal animal body temperature with model results obtained using local weather station data serving as the baseline of comparison. The objective of the study was to determine which gridded data are sufficient to capture observed patterns of thermal stress. Three coastal sites in western North America were included in this analysis: Boiler Bay, Oregon; Bodega Bay, California; and Pacific Grove, California. The gridded data with the highest spatial resolution, the 32-km North American Regional Reanalysis (NARR) and the 38-km Climate Forecasting System Reanalysis (CFSR), predicted daily maximum intertidal animal temperature most similarly to the local weather Station data. Time step size was important for variables that change rapidly throughout the day, such as solar radiation. There were site-based differences in the ability of the model to predict daily maximum intertidal animal temperature, with the gridded data predictions being the closest to local weather station predictions in Boiler Bay, Oregon. In a review of gridded data used as part of ecological studies, there was broad use of the data across subject areas and ecosystems so the recent improvements in the spatial (from 2 degrees to 32 km) and temporal scales (from 6 hours to 1 hour) of gridded data will further add to the applicability within the ecological community particularly for mechanistic studies.     

Community change in the variable resource habitat of the abyssal northeast Pacific

Research capable of differentiating resource-related community-level change from random ecological drift in natural systems has been limited. Evidence for nonrandom, resource-driven change is presented here for an epibenthic megafauna community in the abyssal northeast Pacific Ocean from 1989 to 2004. The sinking particulate organic carbon food supply is linked not only to species-specific abundances, but also to species composition and equitability. Shifts in rank abundance distributions (RADs) and evenness, from more to less equitable, correlated to increased food supply during La Ni?a phases of the El Ni?o Southern Oscillation. The results suggest that each taxon exhibited a differential response to a sufficiently low dimension resource, which led to changes in community composition and equitability. Thus the shifts were not likely due to random ecological drift. Although the community can undergo population-level variations of one or more orders of magnitude, and the shape of the RADs was variable, the organization retained a significant consistency, providing evidence of limits for such changes. The growing evidence for limited resource-driven changes in RADs and evenness further emphasizes the potential importance of temporally variable disequilibria in understanding why communities have certain basic attributes.     

Constraints on foraging success due to resource ecology limit colony productivity in social insects

The benefit of group living is a fundamental question in social evolution. For sociality to evolve, each individual must gain in terms of some fitness component by living in larger groups. However, in social insects, a decrease in per capita success in brood production has been observed in larger groups. While it has been proposed that this decrease could be outweighed by an increase in the predictability of success, a functional basis to this hypothesis has so far never been demonstrated. In this paper, using foraging economics as a functional proxy to colony productivity, we construct a model to explore how number of foragers in the colony interacts with the ecology of resources to influence per capita foraging success and its predictability. The results of the model show that there is no increase in per capita foraging success in larger colonies under most circumstances, though there is an increase in its predictability. We then test the model with empirical data on the foraging behavior of the primitively eusocial wasp, Ropalidia marginata. The consistency between the data and the model suggests that foraging economics could provide a robust functional basis in explaining the relationship between colony size and productivity.     

On inferring population trends of mobile waterbirds from aerial transect surveys in variable environments

Environmental and Ecological Statistics - Monitoring waterbird populations in Australia is challenging for reasons of counting logistics, and because population aggregation and dispersion can shift...     

Waste to resource: use of water treatment residual for increased maize productivity and micronutrient content

Environmental Geochemistry and Health - Soil degradation, which is linked to poor nutrient management, remains a major constraint to sustained crop production in smallholder urban agriculture (UA)...     

Meta-analysis: trophic level, habitat, and productivity shape the food web effects of resource subsidies

Studies of the effects of cross-habitat resource subsidies have been a feature of food web ecology over the past decade. To date, most studies have focused on demonstrating the magnitude of a subsidy or documenting its effect in the recipient habitat. Ecologists have yet to develop a satisfactory framework for predicting the magnitude of these effects. We used 115 data sets from 32 studies to compare consumer responses to resource subsidies across recipient habitat type, trophic level, and functional group. Changes in consumer density or biomass in response to subsidies were inconsistent across habitats, trophic, and functional groups. Responses in stream cobble bar and coastline habitats were larger than in other habitats. Contrary to expectation, the magnitude of consumer response was not affected by recipient habitat productivity or the ratio of productivity between donor and recipient habitats. However, consumer response was significantly related to the ratio of subsidy resources to equivalent resources in the recipient habitat. Broad contrasts in productivity are modified by subsidy type, vector, and the physical and biotic characteristics of both donor and recipient habitats. For this reason, the ratio of subsidy to equivalent resources is a more useful tool for predicting the possible effect of a subsidy than coarser contrasts of in situ productivity. The commonness of subsidy effects suggests that many ecosystems need to be studied as open systems.     

Microbial relationships in surface-mine revegetation

The establishment and interrelationships of microorganisms with soil and plant processes during reclamation are greatly influenced by the composition of the planting medium and vegetation practices. While in some instances the parent material may be used as the vegetation medium, the practice of topsoiling, particularly the direct haul method, may be beneficial in introducing microorganisms and improving the quality of the plant growth medium of spoils that are chemically or physically less desirable than the native soils. The influence of different vegetation types on soil development on surface mines may be a reflection of physioiogical differences that affect microbial development in the rhizosphere. Such differences include levels of carbohydrate translocated to the root system and/or released into the surrounding soil; the plant's effectiveness as a mycorrhizal host; and the rate of degradation of plant residues. It has become apparent that microbial interactions are an important part of plant and soil processes in reclamation. While some of the microorganisms important in plant growth and soil development can be introduced readily by management practices, the majority usually are disseminated by natural means and only gradually become a part of the microbial population. More research is needed on developing new methods or refining current procedures for early introduction of these microorganisms in reclamation practices.     

Microbial relationships in surface-mine revegetation

The establishment and interrelationships of microorganisms with soil and plant processes during reclamation are greatly influenced by the composition of the planting medium and vegetation practices. While in some instances the parent material may be used as the vegetation medium, the practice of topsoiling, particularly the direct haul method, may be beneficial in introducing microorganisms and improving the quality of the plant growth medium of spoils that are chemically or physically less desirable than the native soils. The influence of different vegetation types on soil development on surface mines may be a reflection of physioiogical differences that affect microbial development in the rhizosphere. Such differences include levels of carbohydrate translocated to the root system and/or released into the surrounding soil; the plant's effectiveness as a mycorrhizal host; and the rate of degradation of plant residues. It has become apparent that microbial interactions are an important part of plant and soil processes in reclamation. While some of the microorganisms important in plant growth and soil development can be introduced readily by management practices, the majority usually are disseminated by natural means and only gradually become a part of the microbial population. More research is needed on developing new methods or refining current procedures for early introduction of these microorganisms in reclamation practices.     

Barnacle suspension-feeding in variable flow

Suspension-feeding behavior of the adult barnacleSemibalanus balanoides (L.), collected at Woods Hole, USA, in 1987 and 1988, was studied in variable conditions of unidirectional and oscillating water flow. Barnacles growing on rocks were placed in a laboratory flume and exposed to precise patterns of water flow created with a specially designed electronic-circuit controlling a motor-driven propeller submersed in the flume. Laser darkfield and brightfield illumination were used to video-record the movement of suspended particles and dye in the flume and barnacle activity. When water was accelerated unidirectionally past feeding barnacles, they consistently changed feeding behavior from actively sweeping their thoracic appendages (cirri) through the water in slow-flow to passively holding cirri into the current in faster flow. The mean water velocity at which this behavioral switch occurred was 3.10 cm s^–1. In slow-flow, each active sweep of the cirri created a feeding vortex that caused suspended particles to swirl into the capture zone of the following sweep. Barnacles in simulated wave-action conditions (oscillatory flow) fed passively, and orientated extended cirri to flow direction. Cirri were rapidly reoriented with the same frequency at which flow direction reversed. Slow-motion analysis of one barnacle feeding in oscillating flow (0.65 Hz) indicated that reversal of the orientation of the cirri began 0.19 s before the water itself started to reverse direction. In additional experiments, barnacles were exposed to a repetitive pattern of accelerating-decelerating flow. During each flow cycle, barnacles switched from active to passive feeding as water accelerated. Repeated exposure of an individual to the same flow-cycle caused a consistent decrease in the water-velocity threshold at which the behavioral switch occurred.     

中国土地生产力变化的情景分析

中国土地生产力变化态势是当前国内外学术界、决策界关注的焦点问题之一.介绍了土地生产力估算系统(ESLP)的原理与功能模块并利用该系统研究了中国土地生产力的变化态势.ESLP是在气温、降水、辐射水平、土壤质地等自然因素控制下,受土地利用方向与强度影响的,考虑土地系统不同的投入水平和管理措施的区域土地生产力估算系统.ESLP关注土地生产力变化的时空动态,能表达出不同投入管理水平下土地生产力的时空变化.文章应用ESLP研究了1988年和2000年中国土地生产力变化及其空间分异特征,将估算结果与1988年和2000年全国分县粮食产量数据的比较与验证表明,基于ESLP估算的各县土地生产力与各县粮食总产量具有很高的相关性,在一定程度上反映一个区域的粮食生产能力.在此基础上,应用ESLP预测了2010与2020年在气候变化情景下土地生产力的变化,预测结果显示,虽然局部地区土地生产力有小幅减少趋势,但从全国来看,土地生产力增长趋势明显.平均来看,2010年比2000年增长4.4%,而到2020年,土地生产力的增长幅度达到10.7%.不过在各个农业生态分区上,不同年份土地生产力变化差异较大,在2010年和2020年长江中下游区土地生产力均呈一定幅度的下降,而甘新区和西藏区只在2010年土地生产力有小幅下降.该研究结论对我国编制土地利用规划与粮食生产方面的决策具有重要的参考价值.     

Primary productivity in the Gulf of California

Primary productivity data from 6 cruises in the Gulf of California are summarized. A total of 31 stations with 133 samples was available. The Gulf of California represents a subtropical area with exceptionally high rates of primary productivity. This fact may be accounted for by temporary seasonal upwelling, a wind-mixed water column down to the shallow thermocline, especially in the northern part of the Gulf, and by tidal mixing, especially in the Ballenas Channel between Baja California and the island Angel de la Guardia. Rates of primary productivity in the Gulf of California are comparable to those in areas such as the Bay of Bengal, the upwelling areas off the west coast of Baja California, or North Africa. They are about 2 to 3 times greater than that in the open Atlantic or the open Pacific at similar latitudes.Contribution from the Scripps Institution of Oceanography, University of California, San Diego. This work was part of the Scripps Tuna Oceanography Research Program. It was supported by the Bureau of Commercial Fisheries under contract number 14-17-0007-963. Shiptime was provided from funds of the National Science Foundation.     

Invading introduced species in insular heterogeneous environments

We are concerned with the development and analysis of a predator–prey system designed for heterogeneous insular environments; populations are native preys exposed to introduced and invading predators and competitor preys. We first look at the unstructured model; this yields a singular system of ordinary differential equations having interesting dynamical features, such as finite time extinction or persistence of populations. Next we build a spatially heterogeneous structured model upon developing a reaction–diffusion system; then, using numerical experiments we analyze some typical effects of spatial heterogeneities on the persistence or extinction of native or introduced and invading species. The case of Kerguelen sub-Antartic heterogeneous islands where both domestic cats and alien preys have been introduced is taken as an example.     

磺胺嘧啶在水中的微生物降解研究

为了探明磺胺嘧啶在水中的环境行为,通过室内模拟降解实验分别研究了磺胺嘧啶在湖水和猪场废水中的好氧和厌氧微生物降解,考察了供氧方式和有机质含量对磺胺嘧啶微生物降解的影响。结果表明:磺胺嘧啶在猪场废水中厌氧微生物降解速率高于其好氧组,而磺胺嘧啶在湖水中厌氧微生物降解速率低于其好氧组。磺胺嘧啶在湖水和猪场废水中的好氧或厌氧微生物降解均较缓慢,这可能与其较强的抑菌性和微生物的营养状况有关。通过微生物培养还研究了好氧降解时磺胺嘧啶对湖水中微生物种群生长的影响,数据显示:磺胺嘧啶对湖水和猪场废水中细菌的生长具有一定的刺激作用,而对真菌和放线菌的生长影响不明显。     

Evaluation of potential topsoil productivity

A biomass productivity model based on soil properties and climate is developed from literature and used to evaluate and compare potential effects of mining and reclamation on several soils in the continental United States. Soil productivity is assumed to vary as a product of root distribution function modified by five soil properties: available water, aeration porosity, bulk density, electrical conductivity, and pH. Yield limiting property levels are derived from literature and input soil data are obtained from available USDA Soil Conservation Service information on typical profiles. Modelled values of potential productivity after mining, indicate problems and limitations to be expected. The proposed model can be used as a guide to reclamation strategy, to restore the land to premining conditions, or at times to enhance productivity of a reclaimed area.     

Microbial mediated arsenic biotransformation in wetlands

Arsenic (As) is a pervasive environmental toxin and carcinogenic metalloid. It ranks at the top of the US priority List of Hazardous Substances and causes worldwide human health problems. Wetlands, including natural and artificial ecosystems (i.e. paddy soils) are highly susceptible to As enrichment; acting not only as repositories for water but a host of other elemental/chemical moieties. While macroscale processes (physical and geological) supply As to wetlands, it is the micro-scale biogeochemistry that regulates the fluxes of As and other trace elements from the semi-terrestrial to neighboring plant/aquatic/atmospheric compartments. Among these fine-scale events, microbial mediated As biotransformations contribute most to the element’s changing forms, acting as the ‘switch’ in defining a wetland as either a source or sink of As. Much of our understanding of these important microbial catalyzed reactions follows relatively recent scientific discoveries. Here we document some of these key advances, with focuses on the implications that wetlands and their microbial mediated transformation pathways have on the global As cycle, the chemistries of microbial mediated As oxidation, reduction and methylation, and future research priorities areas.

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微生物燃料电池产电研究及微生物多样性分析

以乙酸钠为阳极底物,碳毡材料为阴阳电极,构建了无介体双室微生物燃料电池(Microbial fuel cell,MFC),研究不同阴极受体、外接电阻、乙酸钠浓度和不同接种方式等因素对电池产电性能的影响.根据不同接种方式下微生物燃料电池产电性能差异,利用PCR-DGGE技术对不同接种方式下的微生物多样性进行分析.研究结果表明:在500 mL的阴阳极反应体系中,当接入500 Ω外电阻,阴极电子受体为高锰酸钾,阳极乙酸钠质量浓度为6.46 g/L,只接入附着有大量微生物的电极时,微生物燃料电池产电性能最好,最大电功率密度可达353.57 mW/m2,库伦效率为39.35%;微生物多样性分析显示.δ-变形菌纲、β-变形菌纲和拟杆菌门的菌种更适应微生物燃料电池的运行环境,能在电极上大量富集.提高电池的产电性能.是电极上的优势菌群.图8表1参21