Citation: Terrestrial Ecosystems, John D. Aber & Jerry M. Melillo, (Philadelphia: Saunders College Publishing, 1991).
Terrestrial Ecosystems is the text chosen by Dr. Tim Seastedt for the EPO biology course Ecosystem Ecology (EPOB 4170/5170). Aber and Melillo present the overview of ecosystems necessary to understand environmental problems affecting thoseecosystems.
Terrestrial Ecosystems is divided into four sections. The first section provides useful technical information to those making decisions about wild life habitat and ecosystems. The focus of this section is the nature of ecosystem studies. Aber and Melillo offer a definition of ecosystem and a brief history of the study and significance of ecosystem studies. They outline the important characteristics of terrestrial ecosystems; their relationship to major vegetation and soil types; correlations between climate and ecosystem structure and variation within climatic regions. Two chapters are devoted to the measurement of ecosystem function. Specifically, nutrient and water balances withinecosystems are examined and the methods for their measurement discussed. The cycles for carbon, magnesium, calcium, sulphur and nitrogen are discussed in detail and graphically presented. The application of systems analysis to ecosystems is advocated and the limitations to a systems approach examined.
Section two provides information for those concerned with the management ofecosystems, specifically the management of vegetation and habitat and the inter-dependent nature of ecosystems. This section examines the processes controlling ecosystem structure and function. The energy balance, within both a single leaf and the ecosystem as a whole is explained. Aber and Melillo acknowledge the complex relationship between the water balance and vegetation growth and its affect on light attenuation and thus total photosynthesis within the system. The affect of soil chemistry and biological modification on nutrient availability and their relationship to resource allocation and primary productivity is examined in depth. Specifically, litter decomposition; origin of soil organic matter and plant-soil interactions are shown to affect nutrient cycles. Plant - herbivore interaction and the relation between herbivore activity and ecosystem characteristics is presented. Likewise, the characteristics of fire dependent ecosystems are presented.
Section three provides information for those concerned with the affect of both anthropomorphic and natural disturbances on ecosystems and habitat. This section examines disturbance, succession and ecosystem function in three different systems: fire and succession in the taiga forests on interior Alaska; interactions among vegetation, herbivores and predators in the Serengeti and the absence of fire andherbivory in the northern hardwood forests of New England. All three examinations relate the affect ofdisturbances (or lack thereof) on the characteristics of an ecosystem. These affects are asserted to be non-static and mutual.
The final section is helpful for understanding the methods and tools used for managing ecosystems and some of the difficulties associated therewith. This section examines human impacts on local, regional and global ecosystems. This section discusses the use of computer models for forest ecosystem management. It discusses agriculturalecosystems which resulted from the activities of indigenous peoples and those which result from modern intensive agricultural practices. It compares the characteristics of both to those of sustainable agrosystems. The authors acknowledge the difficulties associated with determining the magnitude of pollution effects on terrestrial ecosystems and some of the sources of that pollution. In summary Aber and Melillo address the global carbon question and its role in global biogeochemisrty and global change. They briefly examine the use of remote sensing for measuring change in both regional and global environments. Terrestrial Ecosystems presents an overview of ecosystem function which facilitate understanding environmental problems affecting ecosystems.