Trophic Ecology
[rating 3.0]
The original idea was that ecosystems were connected by their interactions. We noted that the availability of biomass at the bottom of the pyramid affected the other trophic layers. There was the idea that top predators could impact the herbivores. A simple model that has been around for years, the Snowshoe Hare/Lynx model, gave us some understanding of changes in ecological systems. These were fine for most student understandings but the situation has developed rapidly from there. The idea of trophic cascading – that impacts in one part can affect other parts of the food web is also well known but, again, it’s only a simplistic picture. The aim of this text is to produce a far more nuanced understanding of this situation. It’s not just a case of refining knowledge; as humans impact more ecosystems in more ways, it becomes crucial that we are aware of exactly how ecosystems function and how our interactions might cause change that we could not have predicted.
The text focusses on these two sets of interactions – those caused by impacts from the bottom of the trophic system, and those from the top. It starts with a theoretical examination of trophic interactions; a very useful guide to seeing where we are and how we got there. The classic Eltonian pyramid suggests that higher trophic levels are constrained by resources such as nutrient supply and solar radiation – bottom up. The contrast is the top-down model whereby the effects of herbivores and carnivores determine the nutrient level. There are cases for both but the interest here is what happens when we try to connect the two. We can see both within an ecosystem, but what models work when they meet? Further, how does this vary with scale and ecosystem type? The historical background we get here is useful – it illustrates the timespan over which parts of this issue have been researched (almost 100 years if we take Elton’s early work).
This single chapter, comprises all of part 1. Part two looks at a range of ecosystems to explore what is known about top-down and bottom-up systems; firstly as individuals explanations and then to see what can be gleaned from a study of the interfaces between the two. A wide range of ecosystems is discussed from oceans to savannahs but the common elements are there. More importantly, there are numerous examples of the emerging research being carried out and the incongruities that they throw up. These studies are not confined to work within ecosystems but also between them as one set of outputs become another’s input. Part three, titled ‘patterns and processes’ takes these ideas but shows how using them helps us better understand a range of ecological processes. The previous section looked at how trophic interactions worked with an ecosystem. Here, the focus is on those processes that are common across multiple ecosystems such as plant defences, microbial functioning and evolution. There are topics less often covered including the issue of scale and more timely ones such as the role of human action.
Overall, this is a fascinating read. It is clearly aimed at the researcher seeking to integrate the two approaches to create better ecosystem models and, in this regard, it provides an important link between different approaches and ecosystems. As a more general text, it provides some important information helping the reader to make sense of concepts often blurred e.g. trophic cascading. Those wishing to understand the real interactions between and within systems would do well to read this collection of ideas.
