Optimal biomass allocation in heterogeneous environments in a clonal plant—Spatial division of labor

When interconnected ramets of clonal plants are growing in heterogeneous environments, ramets may specialize to uptake locally abundant resources rather than scarce resources. This biomass allocation pattern may result in more efficient sharing of resources through physiological integration and an overall benefit to the plants (spatial division of labor; DoL).     

The welfare effects of fuel conservation policies in a dual-fuel car market: Evidence from India

We estimate a model of vehicle choice and kilometers driven to analyze the long-run impacts of fuel conservation policies in the Indian car market. We simulate the effects of petrol and diesel fuel taxes and a diesel car tax, taking into account their interactions with the pre-existing petrol fuel tax and car sales taxes. At levels sufficient to reduce total fuel consumption by 7%, the increased diesel and petrol fuel taxes both yield deadweight losses (net of externalities) of about 4 (2010) Rs./L. However, at levels sufficient to reduce total fuel consumption by 2%, the increased petrol fuel tax results in a deadweight loss per liter of fuel conserved that is greater than that caused by the diesel fuel tax. This reflects both the high pre-existing tax on petrol fuel and the high own-price elasticities of fuel demand in India. A tax on diesel cars that results in the same diesel market share as the large diesel fuel tax actually has a negative deadweight loss per liter of fuel conserved. The welfare effects of all three policy instruments are positive, once the external benefits of reducing fuel consumption are added to the excess burden of taxation.     

Too hot to handle: The effects of high temperatures during pregnancy on adult welfare outcomes

This paper studies the long-term effects of high temperatures during pregnancy on later-life outcomes for Chinese adults. Adults experienced one additional high-temperature day during in utero period, on average, attain 0.02 fewer years of schooling, increase the risk of illiteracy by 0.18%, achieve lower standardized word-test score by 0.48%, and are shorter by 0.02 cm. The impacts are greater in the first and second trimesters. Additionally, we find that income effects represent one important channel to explain the adverse effects of hot weather. Back-of-the-envelope predictions suggest that by the end of the 21st century, a 0.14–0.54 reduction in years of education and a 0.21–0.84 cm reduction in height is likely to result from climate change, ceteris paribus.     

Market equilibrium and welfare effects of a fuel tax in China: The impact of consumers' response through driving patterns

We investigate the market equilibrium and welfare effects of a fuel tax in China relative to an alternative policy instrument that rations the number of new automobile sales through auctioned quotas. Unlike those of previous studies, our modeling approach incorporates both household car purchase and utilization decisions, the latter of which have been ignored in previous studies on China's fuel tax. Ignoring this margin of choice will underestimate the fuel tax's ability to mitigate externalities. Using detailed household-level panel data and a fixed effects econometric specification, we estimate the fuel price elasticity of vehicle miles traveled is −0.59 on average. The results of the counterfactual analysis suggest that a 51% increase in tax-inclusive gasoline prices will reduce car sales by 24.9% but increase social welfare to a degree that depends on vehicles' lifetime. We find that compared to auctioned quotas, the fuel tax results in greater car sales but higher social welfare.     

Exploring the effects of individual traits and within-colony variation on task differentiation and collective behavior in a desert social spider

Social animals are extraordinarily diverse and ecologically abundant. In understanding the success of complex animal societies, task differentiation has been identified as a central mechanism underlying the emergence and performance of adaptive collective behaviors. In this study, we explore how individual differences in behavior and body size determine task allocation in the social spider Stegodyphus dumicola. We found that individuals with high body condition indices were less likely to participate in prey capture, and individuals’ tendency to engage in prey capture was not associated with either their behavioral traits or body size. No traits were associated with individuals’ propensity to participation in web repair, but small individuals were more likely to engage in standard web-building. We also discovered consistent, differences among colonies in their collective behavior (i.e., colony-level personality). At the colony level, within-colony variation in behavior (aggressiveness) and body size were positively associated with aggressive foraging behavior. Together, our findings reveal a subtly complex relationship between individual variation and collective behavior in this species. We close by comparing the relationship between individual variation and social organization in nine species of social spider. We conclude that intraspecific variation is a major force behind the social organization of multiple independently derived lineages of social spider.     

Disentangling the effects of heterogeneity, stochastic dynamics and sampling in a community of aquatic insects

A dynamic and heterogeneous species abundance model generating the lognormal species abundance distribution is fitted to time series of species data from an assemblage of stoneflies and mayflies (Plecoptera and Ephemeroptera) of an aquatic insect community collected over a period of 15 years. In each year except one, we analyze 5 parallel samples taken at the same time of the season giving information about the over-dispersion in the sampling relative to the Poisson distribution. Results are derived from a correlation analysis, where the correlation in the bivariate normal distribution of log abundance is used as measurement of similarity between communities. The analysis enables decomposition of the variance of the lognormal species abundance distribution into three components due to heterogeneity among species, stochastic dynamics driven by environmental noise, and over-dispersion in sampling, accounting for 62.9, 30.6 and 6.5% of the total variance, respectively. Corrected for sampling the heterogeneity and stochastic components accordingly account for 67.3 and 32.7% of the among species variance in log abundance. By using this method, it is possible to disentangle the effect of heterogeneity and stochastic dynamics by quantifying these components and correctly remove sampling effects on the observed species abundance distribution.     

The influence of slope collapse on water exchange between a pit lake and a heterogeneous aquifer

Slope collapse will reduce the water exchange. Slope collapse will affect the spatial distribution of the water exchange. Precipitation have the most impact on the dynamics of the water exchange. Due to the increase in open pit mining, pit lakes have become common surface water features, posing a potential risk to subsurface aquifer. In this study, a pit lake–groundwater interaction model is built based on the general program MODFLOW with the LAK3 package. For the first time, the effects of lake-slope collapse and aquifer heterogeneity on pit lake–groundwater interactions are analyzed by dividing the lake into six water exchange zones based on the aquifer lithology and groundwater level. Our investigation and simulations reveal a total water exchange from groundwater to the lake of 349000 m³/a without collapse of the pit lake slope, while the total net water exchange under slope collapse conditions is 248000 m³/a (i.e., a reduction of 1.40-fold). The monthly net water exchange per unit width from groundwater to the lake reaches the largest in April, shifting to negative values in zone IV from June to August and in zone V in June and July. Moreover, the monthly net water exchange per unit width decreases from north to south, and the direction and magnitude of water exchange are found to depend on the hydraulic gradients between the lake and groundwater and the hydraulic conductivity of the slope collapse.     

Understanding the sources and effects of abandoned,lost, and discarded fishing gear on marine turtles in northern Australia

Globally, 6.4 million tons of fishing gear are lost in the oceans annually. This gear (i.e., ghost nets), whether accidently lost, abandoned, or deliberately discarded, threatens marine wildlife as it drifts with prevailing currents and continues to entangle marine organisms indiscriminately. Northern Australia has some of the highest densities of ghost nets in the world, with up to 3 tons washing ashore per kilometer of shoreline annually. This region supports globally significant populations of internationally threatened marine fauna, including 6 of the 7 extant marine turtles. We examined the threat ghost nets pose to marine turtles and assessed whether nets associated with particular fisheries are linked with turtle entanglement by analyzing the capture rates of turtles and potential source fisheries from nearly 9000 nets found on Australia's northern coast. Nets with relatively larger mesh and smaller twine sizes (e.g., pelagic drift nets) had the highest probability of entanglement for marine turtles. Net size was important; larger nets appeared to attract turtles, which further increased their catch rates. Our results point to issues with trawl and drift‐net fisheries, the former due to the large number of nets and fragments found and the latter due to the very high catch rates resulting from the net design. Catch rates for fine‐mesh gill nets can reach as high as 4 turtles/100 m of net length. We estimated that the total number of turtles caught by the 8690 ghost nets we sampled was between 4866 and 14,600, assuming nets drift for 1 year. Ghost nets continue to accumulate on Australia's northern shore due to both legal and illegal fishing; over 13,000 nets have been removed since 2005. This is an important and ongoing transboundary threat to biodiversity in the region that requires attention from the countries surrounding the Arafura and Timor Seas. Entender las Fuentes y Efectos de Equipo de Pesca Abandonado, Perdido y Desechado sobre las Tortugas Marinas del Atlántico Norte     

Foliage profiles of individual trees determine competition,self-thinning,biomass and NPP of a Cryptomeria japonica forest stand: A simulation study based on a stand-scale process-based forest model

A simulation study was carried out to investigate simultaneously the effects of eco-physiological parameters on competitive asymmetry, self-thinning, stand biomass and NPP in a temperate forest using an atmosphere–vegetation dynamics interactive model (MINoSGI). In this study, we selected three eco-physiological relevant parameters as foliage profiles (i.e. vertical distribution of leaf area density) of individual trees (distribution pattern is described by the parameter η), biomass allocation pattern in individual tree growth (χ) and the maximum carboxylation velocity (V_max). The position of the maximal leaf area density shifts upward in the canopy with increasing η. For scenarios with η < 4 (foliage concentrated in the lowest canopy layer) or η > 12 (foliage concentrated in the uppermost canopy layer), a low degree of competitive asymmetry was produced. These scenarios resulted in the survival of subordinate trees due to a brighter lower canopy environment when η < 4 or the generation of spatially separated foliage profiles between dominant and subordinate trees when η > 12. In contrast, competition between trees was most asymmetric when 4 ≤ η ≤ 12 (vertically widespread foliage profile in the canopy), especially when η = 8. In such cases, vertically widespread foliage of dominant trees lowered the opportunity of light acquisition for subordinate trees and reduced their carbon gain. The resulting reduction in carbon gain of subordinate trees yielded a higher degree of competitive asymmetry and ultimately higher mortality of subordinate trees. It was also shown that 4 ≤ η ≤ 12 generated higher self-thinning speed, smaller accumulated NPP, litter-fall and potential stand biomass as compared with the scenarios with η < 4 or η > 12. In contrast, our simulation revealed small effects of χ or V_max on the above-mentioned variables as compared with those of η. In particular, it is notable that greater V_max would not produce greater potential stand biomass and accumulated NPP although it has been thought that physiological parameters relevant to photosynthesis such as V_max influence dynamic changes in forest stand biomass and NPP (e.g. the greater the V_max, the greater the NPP). Overall, it is suggested that foliage profiles rather than biomass allocation or maximum carboxylation velocity greatly govern forest dynamics, stand biomass, NPP and litter-fall.     

The effects of the risk of fire on the optimal rotation of a forest

The effects of the risk of fire or other unpredictable catastrophe on the optimal rotation period of a forest stand are investigated. It is demonstrated that when fires occur in a time-independent Poisson process, and cause total destruction, the policy effect of the fire risk is equivalent to adding a premium to the discount rate that would be operative in a risk-free environment. Other cases are also investigated and in each a modified form of the Faustmann formula is derived and a “marginal” economic interpretation given.     

The effects of a coal power plant on the environment and wildlife in southeastern Turkey

This study was carried out to determine the possible effects of the Afsin-Elbistan Coal Power Plant (AECPP) on the environment.. The soil and plant samples were collected, based on the dominant wind direction, which is from northeast to southwest and we defined the northeast part of the plant as the less contaminated direction (LCD) and the southwest part as the more contaminated direction (MCD). The results indicated that the AECPP created environmental problems and caused contaminations especially in the MCD. The results of the statistical analysis for the measured attributes between the LCD and the MCD showed that there were significant differences for pH, SO4(-2)-S, Ni and Pb. Significant correlations were found between the distance from the AECPP and some of the measured soil and plant parameters in the MCD. The concentrations of SO4(-2)-S, Ni and Pb decreased as the distance increased. The discharge water carries a potential risk for the aquatic life and soil health in the area. The honey quality was also affected negatively by fly ash and emission.     

Experimental test of the effects of a non-native invasive species on a wintering shorebird

The abundance of nearly one-quarter of the world's shorebird species is declining. At the same time, the number of non-native species in coastal ecosystems is increasing rapidly. In some cases, non-native species may affect negatively the abundance and diversity of shorebird prey species. We conducted an experimental study of the effects of the introduced European green crab (Carcinus maenas) on prey consumption by wintering Dunlin (Calidris alpina) in a central California estuary. We placed green crabs and Dunlin sequentially in field enclosures and measured changes in density of benthic invertebrate prey (e.g. polychaetes and small clams), Dunlin biomass, and gut contents of both Dunlin and crabs and observed foraging behavior of Dunlin. Green crabs significantly affected Dunlin foraging success through both direct and indirect multitrophic linkages. In enclosures with high densities of green crabs, crab foraging reduced the availability of polychaetes, and Dunlin consumed significantly fewer polychaetes compared with Dunlin in enclosures without crabs. High densities of green crabs were also associated with increased availability of small clams. Dunlin consumed significantly more small clams compared with Dunlin in enclosures without crabs. In our literature survey of studies of effects of non-native invasive species on shorebirds, we found three prior experiments that addressed the effect of non-native invasive species on shorebirds. Results of two of these studies showed positive direct effects of non-native invertebrates on shorebirds, 1 showed negative direct effects of a non-native plant on shorebirds through habitat conversion, and none showed indirect effects of non-native invertebrates. We suggest future management of shorebirds explicitly examine how non-native marine species, particularly invertebrates, directly and indirectly affect shorebirds.     

基于景观连接度的斑块分级的尺度效应

认识到尺度对景观格局分析结果的影响,生态学家们越来越多地进行尺度效应的相关研究.已有的尺度效应研究多注重描述景脱格局指数对尺度变化的响应,这只能对景观的状态进行描述.无法辨别那些对景观功能具有重要意义的关键景观元素.文章选取8个景观连接度指数.通过改变最小制图单元和物种的搜索范围,研究尺度对斑块分等定级的影响,并据此确定各连接度指数的尺度敏感性.结果表明:景观中斑块的相对重要性随尺度变化而变化,其变化程度因指数而异.其中,AWF为尺度效应最不明显的指数,PC和IIC次之,其余指数(NL,NC,LCP,H和F)的尺度效应均十分显著;在衡量景观的连通性时,除IIC外的其他所有指数的尺度效应均十分显著.由此说明,根据连接度指数确定的斑块相对重要性的尺度敏感性与该指数本身的尺度敏感性无关.     

盐胁迫对3种冷季型草坪草生长的影响

冷季型草坪草在不同盐离子含量的胁迫下生长,其各项生理指标都会发生相应的变化,这些变化可以反应出不同草坪草抗逆性的强弱.本实验所用的品种为早熟禾P.Pratensis L.、黑麦草L.Perenne L.、高羊茅F.Arundinacea Schreb..3种草均为冷季型草坪草.将氯化钠溶液设为5个处理,其质量分数分别为0.1%、0.2%、0.3%、0.6%、0.9%和一个对照,每个处理3次重复.将处理后3种草坪草的种子,播于营养钵中,实验室内培养.每日浇灌相对应的盐溶液,浇灌量为约2/3的溶液流出.待幼苗长到5～7 cm时,进行测定.在盐胁迫条件下,通过对黑麦草、高羊茅、早熟禾的发芽率、POD酶活性、质膜相对电导率等生理指标测定的研究,结果表明黑麦草抗盐性较强,早熟禾的耐盐性较弱.为在盐碱地上种植草坪提供了参考依据.     

The sublethal effects of a detergent on the reproduction,development, and settlement in the polychaetous annelid Capitella capitata

The effect of polyethylene-glycol fatty acid was studied on the various stages throughout the life cycle of Capitella capitata. All concentrations tested reduced the number of trochophores, metatrochophores, and young benthic worms and increased the time required to reach the next stage in an inverse relationship to concentration. Only the higher concentrations of detergent influenced the survival rate and the number of eggs produced and laid. A 90% decrease in the number of benthic worms produced occurred between the control and the highest concentration employed (100 mg/l). The effect of the detergent was similar in field and laboratory-collected larvae.     

The effects of size-dependent predation risk on the interaction between behavioral and life history traits in a stream-dwelling isopod

In field surveys, laboratory observations and field-based assays of behavior, I examined the effects of size-dependent predation risk on the interaction between size at reproductive maturity and maternal care behavior in the stream-dwelling isopod, Lirceus fontinalis. L. fontinalis exhibit population-specific sizes at reproductive maturity which result in population differences in predation risk during the adult phase. Females from streams containing salamander larvae (that prefer small prey) mature at large sizes and then become relatively safe from predation. Females from streams containing fish (that consume all size classes of prey equally) mature at small sizes and remain at risk. I tested whether these differences in expected survival were reflected in the behavior of females during the maternal phase (i.e., the period during which females exhibit maternal care). Female L. fontinalis carry developing juveniles inside a brood pouch. I simulated predatory attacks on gravid female L. fontinalis from the different population types and found that female behavior correlated with population differences in risk. When “attacked”, females from streams with predatory fish (that experience high risk to adult females) released juveniles from the brood pouch, whereas females from populations with predatory salamander larvae (that pose relatively little risk to adult females) did not release juveniles. I discuss the results with reference to the joint evolution of behavioral and life history traits. Received: 6 March 1996 /Accepted after revision: 12 August 1996     

The effects of a no. 2 fuel oil and two crude oils on the growth and photosynthesis of microalgae

Seawater, when equilibrated with a sample of No. 2 fuel oil, becomes toxic in varying degrees to growth of representative types of microalgae, two blue-greens, a diatom, two greens, and a dinoflagellate. For a sensitive organism such as Thalassiosira pseudonana, Strain 3H, 5 ml of seawater equilibrated with fuel oil (containing 15 mg/l of organics) in 20 ml of growth medium is lethal, or roughly in the range of 40 to 400 ppb if the toxic material(s) constitute 1 to 10% water also immediately stops photosynthesis in organism 3H. For other microalgae tested e.g. 580 (a green alga) and PR-6 (a blue-green alga), similar effects on growth and photosynthesis were found, but required higher concentrations of the oil-equilibrated seawater. Water solubles from Kuwait or Southern Louisiana crude oils (when the straight crude oil was equilibrated 1:8 with seawater) were not toxic; however, specific fractions obtained by distillation did show some water-soluble toxicity. Growth experimetns in open or closed growth systems revealed that most organisms were inhibited by varying amounts of these two crude oils when in direct contact with them. Organism 580 would not grow above 5 μl of Southern Louisiana/25 ml of medium, or 10 μl of Kuwait/25 ml of medium (oil in direct contact with algae). With both the seawater equilibrated with fuel oil and the crude oils, the toxic activity is mainly localized in medium and higher boiling fractions derived from distillation cuts from these materials.     

Modeling population effects of the Deepwater Horizon oil spill on a long-lived species

The 2010 Deepwater Horizon (DWH) oil spill exposed common bottlenose dolphins (Tursiops truncatus) in Barataria Bay, Louisiana to heavy oiling that caused increased mortality and chronic disease and impaired reproduction in surviving dolphins. We conducted photographic surveys and veterinary assessments in the decade following the spill. We assigned a prognostic score (good, fair, guarded, poor, or grave) for each dolphin to provide a single integrated indicator of overall health, and we examined temporal trends in prognostic scores. We used expert elicitation to quantify the implications of trends for the proportion of the dolphins that would recover within their lifetime. We integrated expert elicitation, along with other new information, in a population dynamics model to predict the effects of observed health trends on demography. We compared the resulting population trajectory with that predicted under baseline (no spill) conditions. Disease conditions persisted and have recently worsened in dolphins that were presumably exposed to DWH oil: 78% of those assessed in 2018 had a guarded, poor, or grave prognosis. Dolphins born after the spill were in better health. We estimated that the population declined by 45% (95% CI 14–74) relative to baseline and will take 35 years (95% CI 18–67) to recover to 95% of baseline numbers. The sum of annual differences between baseline and injured population sizes (i.e., the lost cetacean years) was 30,993 (95% CI 6607–94,148). The population is currently at a minimum point in its recovery trajectory and is vulnerable to emerging threats, including planned ecosystem restoration efforts that are likely to be detrimental to the dolphins’ survival. Our modeling framework demonstrates an approach for integrating different sources and types of data, highlights the utility of expert elicitation for indeterminable input parameters, and emphasizes the importance of considering and monitoring long-term health of long-lived species subject to environmental disasters. Article impact statement: Oil spills can have long-term consequences for the health of long-lived species; thus, effective restoration and monitoring are needed.     

The effects of aggregation on the performance of the inverse method and indicators of network analysis

Food webs are usually aggregated into a manageable size for their interpretation and analysis. The aggregation of food web components in trophic or other guilds is often at the choice of the modeler as there is little guidance in the literature as to what biases might be introduced by aggregation decisions. We examined the impacts of the choice of the a priori model on the subsequent estimation of missing flows using the inverse method and on the indices derived from ecological network analysis of both inverse method-derived flows and on the actual values of flows, using the fully determined Sylt-Rømø Bight food web model. We used the inverse method, with the least squares minimization goal function, to estimate ‘missing’ values in the food web flows on 14 aggregation schemes varying in number of compartments and in methods of aggregation. The resultant flows were compared to known values; the performance of the inverse method improved with increasing number of compartments and with aggregation based on both habitat and feeding habits rather than diet similarity. Comparison of network analysis indices of inverse method-derived flows with that of actual flows and the original value for the unaggregated food web showed that the use of both the inverse method and the aggregation scheme affected indices derived from ecological network analysis. The inverse method tended to underestimate the size and complexity of food webs, while an aggregation scheme explained as much variability in some network indices as the difference between inverse-derived and actual flows. However, topological network indices tended to be most robust to both the method of determining flows and to the inverse method. These results suggest that a goal function other than minimization of flows should be used when applying the inverse method to food web models. Comparison of food web models should be done with extreme care when different methodologies are used to estimate unknown flows and to aggregate system components. However, we propose that indices such as relative ascendency and relative redundancy are most valuable for comparing ecosystem models constructed using different methodologies for determining missing flows or for aggregating system components.     

pH变化对酸性土壤酶活性的影响

采用酸性土壤,以添加酸或碱的方式,研究酸化或碱化对土壤酶活性的影响.结果表明,培养过程中对照土壤微生物C量(Cmic)变化与土壤pH变化密切相关,Cmic大时pH值相对较低,显示土壤中微生物活动加剧对土壤pH下降的影响.除过氧化物酶外,土壤pH值变化对土壤酶活性影响较大.脲酶、过氧化氧酶、酸性磷酸酶、碱性磷酸酶、脱氢酶、多酚氧化酶和蛋白酶活性大致呈现酸化抑制碱化激活的规律.前期酸碱添加都抑制了酸性磷酸酶、碱性磷酸酶、脱氢酶活性,中期酸碱添加都抑制了多酚氧化酶活性,后期酸碱添加都抑制了蛋白酶活性.蔗糖酶活性呈现前期酸化激活碱化抑制,中期酸碱都以激活为主,后期碱化又呈现抑制作用.纤维素酶活性变化没有明显规律性.总体上酸添加对土壤酶活性主要起抑制作用,碱添加主要起激活作用.土壤Cmic变化和酶活性变化之间有着较为密切的关系,存在酸化抑制Cmic碱化激活Cmic的现象,pH变化对微生物活性的影响是造成土壤酶活性变化的主要因素.