What is and ecosystem

Concept Of Ecosystem

Introduction

In the previous lectures in class we have learned about the Earth and its environment, and we have learned about the diversity of life on the planet and about ecological interactions between species. Now we will combine these two basic components and consider how the environment and life interact in (ecosystems). But before that we should return to a topic introduced at the very start of class, which is that of sustainability and how we view it in terms of system science.

Sustainability and System Science - An ecosystem consists The example used at the start of class was to consider that I give everyone a dollar each time you come to class. The question was: Is that sustainable? In lecture we agreed that more information was needed to answer that question. For example, we needed to know how much money do I have, or the “stock” of money (e.g., if there were 100 students in class and I had a stock of $100, this would work once...). What if I spend money on other stuff like food? What is the "input" or renewal rate of money in my bank account, compared to how fast I consume money? What if the class size grows because class popularity increases? Right away we see that this is a “system” that has a balance point in it that depends on many other parts of the “system”.

Scientific Concepts, applied to ecosystems and to sustainability.

We see that working through this simple example illustrates how complex the issue of sustainability can become.  However, what we also find is that in all such problems there is a common set of key scientific concepts and principles that we will learn to understand in this course – these concepts include the following (there will be more specific examples given later on):

Standing Stock = the amount of material in a "pool", such as the amount of oil in the ground or greenhouse gases in the atmosphere. 

Mass Balance = asking the question of "do the numbers add up?" If I need $100 each class to give to students, but I only have $1, then the mass balance is off. We can also use a mass balance equation to determine how a system is changing over time (we will do this in a later lecture for heat-trapping gases in the atmosphere).

Material Flux Rate = the input or output of material from a system, such as the amount of oil we pump out of the ground each year, or the amount of greenhouse gas we pump into the atmosphere each year by buring fossil fuels.

Residence Time = the standing stock divided by the flux rate, which provides the average time that materials spent circulating in a pool - for example, the residence time of methane in the atmosphere is about 7 years.

What is an Ecosystem?

An ecosystem consists of the biological community that occurs in some locale, and the physical and chemical factors that make up its non-living or abiotic environment. There are many examples of ecosystems -- a pond, a forest, an estuary, a grassland. The boundaries are not fixed in any objective way, although sometimes they seem obvious, as with the shoreline of a small pond. Usually the boundaries of an ecosystem are chosen for practical reasons having to do with the goals of the particular study.

The study of ecosystems mainly consists of the study of certain processes that link the living, or biotic, components to the non-living, or abiotic, components. (Energy transformations) and biogeochemical cycling are the two main processes that comprise the field of ecosystem ecology. As we learned earlier, ecology generally is defined as the interactions of organisms with one another and with the environment in which they occur. We can study ecology at the level of the individual, the population, the community, and the ecosystem.

Studies of individuals are concerned mostly about physiology, reproduction, development or behavior, and studies of populations usually focus on the habitat and resource needs of individual species, their group behaviors, population growth, and what limits their abundance or causes extinction. Studies of communitie examine how populations of many species interact with one another, such as predators and their prey, or competitors that share common needs or resources.