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111.
112.
Organic acids released from plant roots can form complexes with cadmium (Cd) in the soil solution and influence metal bioavailability not only due to the nature and concentration of the complexes but also due to their lability. The lability of a complex influences its ability to buffer changes in the concentration of free ions (Cd); it depends on the association (, m mol s) and dissociation (, s) rate constants. A resin exchange method was used to estimate and (m mol s), which is the conditional estimate of depending on the calcium (Ca) concentration in solution. The constants were estimated for oxalate, citrate, and malate, three low-molecular-weight organic acids commonly exuded by plant roots and expected to strongly influence Cd uptake by plants. For all three organic acids, the and estimates were around 2.5 10 m mol s and 1.3 × 10 s, respectively. Based on the literature, these values indicate that the Cd- low-molecular-weight organic acids complexes formed between Cd and low-molecular-weight organic acids may be less labile than complexes formed with soil soluble organic matter but more labile than those formed with aminopolycarboxylic chelates. 相似文献
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Peter Michael Link Uwe A. Schneider Richard S. J. Tol 《Environmental Modeling and Assessment》2011,16(4):413-429
Using a bioeconomic model of the cod (Gadus morhua) and capelin (Mallotus villosus) fisheries of the Barents Sea, this study assesses the role of the fishermen’s behavior in reducing or intensifying the effects
on the stocks caused by altered population dynamics. The analysis focuses on the economic development of the fisheries employing
a coupled stock size–hydrography-based fishing strategy, which attempts to maximize returns from fishing over a given number
of fishing periods. Results show that if the fishing strategy is based on a short optimization period of only two fishing
periods, changes in population dynamics have a direct influence on the returns from fishing due to the strong pressure on
the stocks applied by the fisheries. If the strategy is based on a longer optimization period, fishing activities may be deferred
to allow for stock regrowth, which improves the economic performance of the fisheries. However, in that case, the relationship
between population dynamics and fishing activities becomes less clear, as even a reduction of the carrying capacities of the
two species allows for an increase in the amount of fish landed without causing a stock collapse due to an increased efficiency
of fleet utilization. The simulations indicate that management considerations and the time horizon of the fishing strategy
dominate the influence of altered population dynamics on the development of the stocks considered in the model. 相似文献
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116.
Lisa J. Henne Daniel W. Schneider Luis M. Martinez 《Journal of Environmental Planning and Management》2002,45(5):613-632
The cost-effectiveness of rapid assessment approaches make their adaptation for use in developing countries appealing, but biological assessment methods need to be validated before use in new geographic areas. The authors tested the suitability of a family-level biotic index for use in a river in west-central Mexico that receives organic point-source pollution from untreated municipal sewage and sugar-cane processing. The biotic index was highly correlated to dissolved oxygen, and could detect different levels of pollution. Information from rapid assessment biomonitoring was used successfully by local natural resource managers to help bring about improvements in water resource management. 相似文献
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118.
The EU is committed to combat climate change and to increase security of its energy supply. Bioenergy from forestry and agriculture plays a key role for both. Concurrently, the EU agreed to halt the loss of biodiversity within its member states. To fulfil the biodiversity target more nature conservation and restoration sites need to be designated. There are arising concerns that an increased cultivation of bioenergy crops will decrease the land available for nature reserves and for “traditional” agriculture and forestry. To assess the role of bioenergy in light of possible negative impacts on ecosystems, the European Forest and Agricultural Sector Optimization Model (EUFASOM) assesses simultaneously economic and environmental aspects of land use. This study contributes to the assessment by analyzing the effect of bioenergy production on European wetland allocations by incorporating the spatial wetland distribution model SWEDI into EUFASOM. Results show that bioenergy targets increase land competition and thus marginal costs of wetland preservation but also of food prices. The designation of national wetland conservation targets, on the other hand, stimulates land use intensification in countries without these targets and here only a transfer of environmental stresses takes place. The model is able to illustrate regional differences of results. 相似文献
119.
Ansgar Quinkenstein Jens Wöllecke Christian Böhm Holger Grünewald Dirk Freese Bernd Uwe Schneider Reinhard F. Hüttl 《Environmental Science & Policy》2009,12(8):1112-1121
Alley cropping is an agroforestry system that offers a promising land use alternative for the temperate zone. On the same field, the sustainable production of food and biomass is possible, while simultaneously, especially in marginal areas, the ecological function of the landscape can be improved. Thus, alley cropping corresponds with the increasing demand for renewable energy resources and for a specific adaptation to the predicted changes of climatic conditions within Central Europe.However, presently, little knowledge exists regarding the effects of alley cropping on the environment. In this study a literature survey was undertaken to provide an overview of the different ecological benefits arising from alley cropping systems within temperate Europe. Abiotic factors (nutrient cycle, microclimate), biotic factors (biodiversity) and the effects on the carbon cycle are discussed in detail.Summarising, the results showed that alley cropping may be an ecologically advantageous land use system for sustainable food and biomass production in comparison with conventional agricultural practices. As a very flexible, but low-input system, alley cropping can supply biomass resources in a sustainable way and at the same time provide ecological benefits. 相似文献
120.
Bianca Unglaub Jasmin Ruch Marie E. Herberstein Jutta M. Schneider 《Behavioral ecology and sociobiology》2013,67(5):785-794
A reduced predation risk is considered to be a major adaptive advantage of sociality. While most studies are concerned with non-predatory prey species, group-living predators are likely to face similar threats from higher-order predators. We studied the relationship between group size and predation risk in the subsocial crab spider Diaea ergandros by testing predictions from theoretical models including attack abatement as well as the formation of protective retreats. In a field survey, we found predatory clubionid spiders in 35 % of the D. ergandros nests and as predicted, nest size did not correlate with predator presence. In a subsequent laboratory experiment, we observed survival probability, nest construction activity and feeding behaviour including weight development between groups of different sizes as well as in the absence or presence of a predator. Large groups had an advantage in terms of survival and growth compared to smaller groups or single individuals. They also built significantly larger nests than smaller groups, supporting the idea of protective retreat formation being an adaptive benefit to group living. Even though clubionids did attack D. ergandros, they did not significantly affect overall mortality of D. ergandros. The feeding experiment showed that spiders fed on a larger proportion of flies in the presence of a predator. However, these groups gained significantly less weight compared to the control groups, indicating that the potential predators not only act as predators but also as food competitors, constituting a twofold cost for D. ergandros. 相似文献