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• Ecological security is defined as if humans' life quality can be guaranteed. • Both availability and affordability should be considered in ecological security. • A two concentric circles model was constructed to evaluate ecological security. • Ecological security coefficients can be calculated quickly by the geometric model. As human influences on natural ecosystems continue to expand, the utilization of natural resources is approaching a threshold where unsustainability threatens the security of human society. As the challenging tradeoffs between human resource demand, ecological sustainability and the security of human society have become more widely recognized, ecological security issues have received extensive attention. However, despite the emergence of substantial body of scientific research on these broader issues, there is still no broad consensus on the definition of ecological security and how it should be applied to mediate resource use and conservation dilemmas. Across the body of published research in this subject area, the criteria and evaluation methods are often so different that the results of different studies are difficult to compare. In this paper, we propose that ecological security refers to the degree to which the condition of ecosystem can support a certain level of socioeconomic development or quality of life. We propose a simple geometric model to quantify ecological security in two dimensions: the availability of ecosystem services and the affordability of humans. The availability dimension is determined by the supply and demand of ecosystem services and the affordability dimension is determined by the cost and the paying capacity balance to obtain ecosystem services. Then, we applied this model to two hypothetical cases to demonstrate its usefulness. The most important feature of the proposed model is that it enables the quick evaluation of important aspects of ecological security for a study area using eight key factors. Although the shape and geographic characteristics of a study area are usually more complex than the hypothetical case, our model can be applied if the conditions are properly simplified or adjusted. [ABSTRACT FROM AUTHOR]

In this paper, the authors continue developing a Linguistic Theory of the Complex Systems models, but in terms of Semantics. Each symbol (transformed function) is syntactically a lexeme, carrying an associated sememe or atomic semantic unit. Each sememe can be decomposed into semes or quantic semantic unities. They may be studied as semantic systems, associated with syntactic systems that serve them as superstructure, with two levels: the quantic and the atomic. Also, it is demonstrated that for all models of complex reality, there exists a complex model from the syntactic and semantic point of view. [ABSTRACT FROM AUTHOR]

In this paper we perform a scenario analysis to assess the likely ecosystem structural shifts that might be induced by seven alternative management scenarios relative to current simulated lake dynamics of Los Molinos reservoir, a monomictic lake located in Argentina. To carry out the scenario analysis, first, we formulate, calibrate and validate a mechanistic biogeochemical model to characterize the nutrients and phytoplankton dynamics of the reservoir under study. The model includes a set of partial differential algebraic equations, which results from dynamic mass balances on main phytoplankton groups, nutrients, dissolved oxygen and biochemical demand of oxygen. We consider the main sources of nutrient loading and the dominant phytoplankton groups. The parameter estimation model is a constrained dynamic optimization problem that has been formulated within an equation oriented control vector parameterization environment. We estimated sixteen parameters, previously identified as the most influential ones. Numerical results for calibration and validation phases show good agreement with field data, and then, we use the proposed model as a prospective tool. The obtained results for the designed nutrient loading scenarios indicate the importance of the impacts of current livestock practices and sewage/collective septic tanks discharges on the water quality. Model predictions indicate that the combination of reduction in nutrient loading from the sewage of residential areas in the lake shore, and implementation of measures to mitigate nutrient exports from livestock production will render the most beneficial effects over the studied ecosystem, thus promoting the improvement of the current ecological state of the reservoir. This is the first time such an approach has been applied to the study of Los Molinos catchment. Thus, the proposed ecological model constitutes a management tool to assess the anthropogenic impacts over this freshwater resource. [ABSTRACT FROM AUTHOR]

The composition, structure, and dynamics of riparian vegetation are under great pressure from natural and anthropogenic disturbances. Regarding the riparian vegetation system, how to assess the effects of disturbances on system, analyze schemes of coupled disturbances and vegetation, and identify the significant effects are fundamental basis of corresponding management. This paper reviews the statistical, empirical, and analytical vegetation models, of which the assumptions, logic, and typical applicability are examined aiming at selecting the most appropriate model for a given case. This study suggests the current challenges of riparian vegetation modeling are as follows: (1) How to integrate multiple anthropogenic disturbances in riparian vegetation modeling for management decision support and (2) How to develop models that are suitable for multi-scale vegetation system that can reflect both long- and short-term effects under various disturbances. [ABSTRACT FROM AUTHOR]

Phytoplankton blooms are very important events allowing the understanding of the coastal ecosystem dynamics, namely in situation of permanent or transient nutrient enrichment. The main objective of this paper is the study of the phytoplankton dynamics and the primary production rates along a strong gradient of salinity in a temperate lagoon, resulting from extreme weather conditions of a very wet spring season and corresponding to high river runoff and nutrient inputs. A 3D-ecological model consisted in a coupled physical and biological model based on the description of light-nutrients dependent phytoplankton and macroalgae growth, the phytoplankton production respiration and mortality, the nutrient cycling, as well as the zooplankton growth, was set up and applied to the Ria de Aveiro lagoon ecosystem in order to fulfil the purposes. The comparison between simulation and observation show that the model is a useful tool to understand the ecological status of the lagoon. On the other hand the model applications can be focused on local mechanisms controlling the main distribution of the biochemical variables in the lagoon as well as on the interaction between local conditions and the advective transport, induced by tides that influence the local balance and determine the bloom occurrence inside the lagoon. The modelling results show that during the study period the nutrient inputs from the freshwater tributaries support the uptake and growth of phytoplankton, reflecting high chlorophyll-a and dissolved oxygen concentrations as well as high values of the primary production. Their spatial distributions depend on local conditions and present a variability imposed by the lagoon characteristics and morphodynamics. The central areas and the far end areas, due to their shallowness and the proximity to the river boundaries, show the highest chlorophyll-a, primary production and dissolved oxygen concentration values, whereas those close to the lagoon mouth, where the influence of the transport and the dispersion by the tidal currents is dominant, show, in general, moderate values, unless a transport from the ocean boundary occurs. [Copyright &y& Elsevier]

Abstract: This paper will discuss TRIPLEX-Flux, a process-based model that estimates net ecosystem production (NEP) as well as analyzing the level of sensitivity of the model''s response by simulating CO2 flux in an existing old black spruce BOREAS site in central Canada. The research objectives were: (1) to test the TRIPLEX-Flux model simulations against flux tower measurements; and (2) to examine parameter and input variable effects on model response via sensitivity analysis. Validation of NEP data at 30min intervals derived from tower and chamber measurements showed that the NEP data from the model corresponded well with the measured NEP from the BOREAS site (R 2 >0.65). Sensitivity analysis demonstrated different levels of sensitivity between morning and noon periods and from the current to doubled atmospheric CO2 concentrations. Additionally, the comparison of different algorithms to calculate stomatal conductance showed that the NEP predicted by the model using the iteration algorithm was consistent with the results using a constant C i/C a of 0.74 for current and 0.81 for doubled CO2 concentrations. Varying parameter and input variable values by ±10% resulted in a similar model response between morning and noon periods (less than or equal to 27.6% and 27.4%, respectively). Most parameters were more sensitive at noon than they were in the morning except for those that were correlated with air temperature, suggesting that air temperature has considerable influence over model sensitivity for these parameters/variables. Air temperature effect was greater under doubled than it was under current atmospheric CO2 concentrations. In contrast, model sensitivity to CO2 decreased under doubled CO2 concentrations. [Copyright &y& Elsevier]

High frequency dissolved oxygen measurements in Mediterranean coastal lagoons show different dynamics on different time scales. In this paper the seasonal and daily dynamics are analysed and discussed and a continuous simulation model is developed to represent them for the salt lake of Fogliano (Italy). Field and laboratory experiments evidenced that primary production slows down in highly oxygenated and irradiated summer days, acting in feedback regime with the oxygen already present in the media, that wind stress contributes in exceeding the oxygen saturation concentration and that there is a firm correlation between oxygen consumption at the sediment layer and overhanging water temperature. Water temperature, solar radiation and wind regime are the forcing functions of the model; the main state variables are dissolved oxygen and detritus in the pelagic and benthic layers, together with carbon dioxide and vegetal biomass. The slow seasonal and fast diel dynamics are both revealed by the model evidencing detailed aspects of oxygen dynamics in a coherent agreement with field observed data trends. [Copyright &y& Elsevier]

A new remote-sensing-based land surface model, named ecosystem–atmosphere simulation scheme (EASS), is introduced in this paper. The principle motivation for formulating EASS is to provide realistic partition of energy fluxes at regional scales as well as consistent estimates of carbon assimilation rates. EASS has the following characteristics: (i) satellite data are used to describe the spatial and temporal information on vegetation, and in particular, we use a foliage clumping index (Ω) in addition to leaf area index to characterize the effects of three-dimensional canopy structure on radiation, energy and carbon fluxes; (ii) energy and water exchanges and carbon assimilation in the soil–vegetation–atmosphere system are fully coupled and are simulated simultaneously; (iii) the energy and carbon assimilation fluxes are calculated with stratification of sunlit and shaded leaves to avoid shortcomings of the “big-leaf” assumption. Model experiments shows that the simulation realism and accuracy by the new strategy are enhanced about 9–14% compared with the “big-leaf model”. Moreover, Ω is useful for accurate separation of sunlit and shaded leaves in the canopy. The accuracy in simulation of energy and carbon fluxes increase about 5–8% by considering the effects of Ω on the radiation interception and the separation of sunlit and shaded leaves; (iv) snow and soil simulations are emphasized by including a flexible and multiple layer scheme. EASS has been tested and validated against multiple-year observed data at several sites. EASS is proved to be overall successful in capturing variations in energy fluxes, canopy and soil temperatures, and soil moisture over diurnal, synoptic, seasonal and inter-annual temporal scales. [Copyright &y& Elsevier]

Queensland fruit fly, Bactrocera (Dacus) tryoni (QFF) is arguably the most costly horticultural insect pest in Australia. Despite this, no model is available to describe its population dynamics and aid in its management. This paper describes a cohort-based model of the population dynamics of the Queensland fruit fly. The model is primarily driven by weather variables, and so can be used at any location where appropriate meteorological data are available.In the model, the life cycle is divided into a number of discreet stages to allow physiological processes to be defined as accurately as possible. Eggs develop and hatch into larvae, which develop into pupae, which emerge as either teneral females or males. Both females and males can enter reproductive and over-wintering life stages, and there is a trapped male life stage to allow model predictions to be compared with trap catch data.All development rates are temperature-dependent. Daily mortality rates are temperature-dependent, but may also be influenced by moisture, density of larvae in fruit, fruit suitability, and age. Eggs, larvae and pupae all have constant “establishment” mortalities, causing a defined proportion of individuals to die upon entering that life stage. Transfer from one immature stage to the next is based on physiological age. In the adult life stages, transfer between stages may require additional and/or alternative functions. Maximum fecundity is 1 400 eggs per female per day, and maximum daily oviposition rate is 80 eggs/female per day. The actual number of eggs laid by a female on any given day is restricted by temperature, density of larva in fruit, suitability of fruit for oviposition, and female activity. Activity of reproductive females and males, which affects reproduction and trapping, decreases with rainfall. Trapping of reproductive males is determined by activity, temperature and the proportion of males in the active population.Limitations of the model are discussed. Despite these, the model provides a useful agreement with trap catch data, and allows key areas for future research to be identified. These critical gaps in the current state of knowledge exist despite over 50 years of research on this key pest. By explicitly attempting to model the population dynamics of this pest we have clearly identified the research areas that must be addressed before progress can be made in developing the model into an operational tool for the management of Queensland fruit fly. [Copyright &y& Elsevier]