Ecologists use stable isotopes (delta13C, delta15N) to better understand food webs and explore trophic interactions in ecosystems. Traditionally, delta13C vs. delta15N bi-plots have been used to describe food web structure for a single time period or ecosystem. Comparisons of food webs across time and space are increasing, but development of statistical approaches for testing hypotheses regardi...

Background and objectives: Iran was reported in the high-risk group of World Food Security Map in 2008 .Identifying food insecurity is first step for executing interventions. Measuring household food security is its cornerstone. SAMAT System was designed to provide a variety of GIS-based reports to policy makers and managers in the field of food security. Methods and Materials: SAMAT system wa...

Climate change disrupts ecological systems in many ways. Many documented responses depend on species' life histories, contributing to the view that climate change effects are important but difficult to characterize generally. However, systematic variation in metabolic effects of temperature across trophic levels suggests that warming may lead to predictable shifts in food web structure and prod...

In food webs, many interacting species coexist despite the restrictions imposed by the competitive exclusion principle and apparent competition. Yet, fundamental understanding, even of minimal conditions for coexistence, is lacking. Using the generalized Lotka-Volterra equations, we show that sustainable coexistence necessitates a nonzero determinant of the interaction matrix, a requirement tha...

The food chain refers to a natural system by which energy is transmitted from one organism to another. In fact, a food chain consists of producers, consumers and decomposition. Presence of complex food web increase the stability of the ecosystem. Classical food chain theory arises from Lotka-Volterra model. In the present paper, the dynamics behavior of three level food chain is studied. A syst...

The abiotic environment has strong influences on the growth, survival, behavior, and ecology of aquatic organisms. Biotic interactions and species life histories interact with abiotic factors to structure the food web. One measure of food-web structure is food-chain length. Several hypotheses predict a linear relationship between one environmental variable (e.g., disturbance or ecosystem size) ...

Seagrass beds provide important habitat for a wide range of marine species but are threatened by multiple human impacts in coastal waters. Although seagrass communities have been well-studied in the field, a quantification of their food-web structure and functioning, and how these change across space and human impacts has been lacking. Motivated by extensive field surveys and literature informa...