1,721,032 research outputs found
Extensive and intensive cost/benefit thermodynamic indicators for the study of the development of trophic networks: application to the lagoon of Venice food web
No full textExtensive and intensive cost/benefit thermodynamic indicators for the study of the development of trophic networks are presented.
The characteristics of a suitable indicator are discussed and two state indicators are proposed, based on the assumption that costs and benefits of the ecosystem growth have to be in balance. The first one, the benefit/cost indicator (BC), is a function of well known state indicators, that fully satisfies the properties required although is difficult to
compute and complex to understand. Nevertheless, from the researcher point of view, this indicator gives interesting insights into
system behavior. The second, the supply demand balance (SDB), is an indicator based on two main assumptions, the first one
being that an ecosystem can be represented by a network of compartments and flows, the second that the metabolic rates scale
across species approximately as the (3/4) power of mass. The SDB indicator summarizes the distance of an ecosystem from an
optimal state in a single number. Under these assumptions the SDB indicator can be regarded as a measure of ecosystem state. It
is easy to compute and simple to understand. SDB looks like a good indicator both for scientific and practical uses to understand
where the ecosystem is going. A tentative application of these indicators to the lagoon of Venice food web is presented
Valutazione della dispersione atmosferica di idrocarburi dal sito contaminato della area ex-IP - La Spezia
No full textRapport
Quantifying nitrogen retention in surface flow wetlands for environmental planning at the landscape-scale
Full text linkSurface flow wetlands are valued highly for their high nutrient retention potential and their unique biodiversity. At
present, there are an increasing number of activities aimed at restoring these sites as multifunctional landscape
entities. The success of wetland restoration is however clearly dependent on the site selection to achieve the specific
restoration goals. This study first presents a tool to identify the most suitable areas for the restoration of surface flow
wetlands for water quality improvement in a given catchment and secondly compares three different mathematical
equations in order to quantify the effect of nitrogen retention when restoring the previously selected, most suitable
wetland sites. For site selection, a score system was developed which is linked to a Geographical Information System.
The score system combines information from a given catchment in eight data layers including soil substrate, actual
land use, relief features, hierarchical drainage basin classification, river proximity and socio-economic factors. The
score system was applied to a potential use situation in the Neuwu ̈hrener Au watershed (40 km2) in northern
Germany belonging to the Baltic Sea drainage basin. Three areas were identified as most suitable for the restoration
of surface flow wetlands. Their potential effect on nitrogen retention was evaluated using three different equations:
(I) a linear relation between wetland load and a wetland; (II) an exponential equation between wetland load and
wetland area; and (III) an exponential equation between wetland load and hydraulic retention time. The linear
approach calculates increasing wetland retention with increasing upstream catchment area and appears to overestimate
nitrogen retention in wetlands located more downstream. The two exponential equations calculated nitrogen
retention in the three wetlands in the same order of magnitude. The results from the siting procedure and the
prediction of nitrogen removal rates are useful for decision makers in wetland planning to base their decision on best
available data and knowledge. The model comparison allows the incorporation of uncertainty in the decision progress
which is seen as a necessary requirement when quantifying biological processes in environmental planning. © 2002
Elsevier Science B.V. All rights reserved
A GIS-based score system for siting and sizing of created or restored wetlands: Two case studies
Full text linkWater bodies are impacted by watershed loads in terms of nutrients and xenobiotics.
This impact impairs the designated uses of the water body. Often preventive actions and end-of-pipe
treatments do not reach the acceptable load to ensure the water quality standard in the water body.
Wetlands are suitable tools for improving the self-purification capacity of a water system and can be
used as a tool to reduce pollutant loads in a river network. This paper presents a methodology for
the Siting and Sizing of created or restored wetlands at the watershed level, based on Geographical
Information Systems (GIS) technique and estimations of wetland required area. The final outputs of
the methodology are a Land Score System for Siting and a first rough estimation for the Sizing. The
combination of these two elements is expected to be useful as a planning tool for watershed management
and wetland planning. In order to assess the reliability of the procedure two very different
case-studies are considered
Nutrient emissions from river systems to coastal areas. A model application to the Po river (Italy)
No full textThe nutrient emission model MONERIS (MOdelling Nutrient Emissions into River Systems) is applied to the Po catchment,
a large (>70,000 km2), densely populated, highly agriculturally exploited and industrialized landscape. The catchment is located
in northern Italy. The Po River discharges into the northwestern Adriatic Sea. Model runs cover the period 1991–2000. The
purpose is to model the catchment in 2001, estimating nutrient emissions and natural background in the basin and loads to the
coastal area. The model was calibrated with data for the period 1990–1995. After validation with data for the period 1995–2000,
the model is used to evaluate future catchment management scenarios.
MONERIS is a spatially distributed parameters steady state model with a time scale of 5 years. The emissions considered
are originated from diffuse and point sources and delivered trough various pathways (groundwater, erosion, overland flow,
atmospheric deposition, urban systems and WWTPs). In order to estimate nutrient loads to the river system, MONERIS includes
a retention model.
An overview of model input requirements, data needs and related problems and solutions adopted is presented in the paper.
Simulated and measured data of several sections along the river are compared for calibration and validation. The relative
importance of different nutrient generation pathways are evaluated. Finally, forecasted yearly nutrient loads at the outlet of
PO basin for the years 2001, 2008 and 2016, consequence of different basin management scenarios, are presented. The results
are ready to be supplied to a water quality Coastal Zone Model, allowing us to evaluate significant switches in trophic state
conditions of the coastal ecosystem
Quo vadis ecosystem?
Full text linkThe description of ecosystems’ evolution is a challenge for many scientists. Several attempts have been made, mostly using
compartments and flows, to describe the structure of ecosystems and holistic indicators or goal functions (GF) to describe the
state and the trend of their evolution. Under a steady flow of energy from the environment, an ecosystem can increase the biomass
by enlarging the number of individuals and/or their body weights until a certain steady state level. In this situation neither the
structure (e.g. species composition) nor the pattern of flows linking its compartments vary and both biomass and flow reach an
“optimal” level. Benefits compensate the costs of the ecosystem evolution.
A question is open: when can an ecosystem be considered to be in an optimal state and how does it reach this state? The answer
to this question is also useful to solve the problems related to the concept of reference state as posed in the Water Framework
Directive (WFD, EU, 2000/60/EC).
In order to answer this question the characteristics of a suitable indicator are discussed and two state indicators are proposed,
based on the assumption that costs and benefits of the ecosystem growth have to be in balance. The first one, the benefit/cost
indicator (BC), is a function of well known state indicators, that fully satisfies the properties required although is difficult to
compute and complex to understand. Nevertheless, from the researcher point of view, this indicator gives interesting insights into
system behavior. The second, the supply demand balance (SDB), is an indicator based on two main assumptions, the first one
being that an ecosystem can be represented by a network of compartments and flows, the second that the metabolic rates scale
across species approximately as the (3/4) power of mass. The SDB indicator summarizes the distance of an ecosystem from an
optimal state in a single number. Under these assumptions the SDB indicator can be regarded as a measure of ecosystem state. It
is easy to compute and simple to understand. SDB looks like a good indicator both for scientific and practical uses to understand
where the ecosystem is going. Finally the applicability of SDB is investigated by computing its values for 33 trophic networks
describing the food webs of different aquatic ecosystems
Ecological processes. In Encyclopedia of Ecology
No full textEcology is the science of the interrelations between living organisms and their environments. These interrelations are complex, varied, and hierarchical. As such, it is a broad and diverse discipline that covers topics from natural selection to population dynamics to biogeochemistry to ecosystem health and sustainability. Our aim in this compendium is to aggregate, in one major reference work, a thorough overview that does justice to this diversity and, at the same time, makes connections between the topics. The result is the five-volume work before you, containing over 530 expertly authored entries. The entries together form a comprehensive picture of the science of ecology and its major subdisciplines. Individually, the entries are succinct, informative, state-of-the-art reviews for use as research references or teaching aids. The Encyclopedia of Ecology covers many facets of this wide-ranging and far-reaching field including:
1.
Behavioral ecology
2.
Ecological engineering
3.
Ecological informatics
4.
Ecological modeling
5.
Ecological processes
6.
Ecosystems
7.
Ecotoxicology
8.
Evolutionary ecology
9.
General ecology
10.
Global ecology
11.
Human ecology
12.
Population dynamics
13.
Systems ecolog
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