The magnificent stands of old-growth trees that characterize the forests of western North America depend on periodic fires for their creation or survival. Deprived of that essential disturbance process eventually they die, leaving an overcrowded growth of smaller trees vulnerable to intense blazes and epidemics of insects and disease.

In Mimicking Nature's Fire, forest ecologists Stephen Arno and Carl Fiedler present practical solutions to the pervasive problem of deteriorating forest conditions in western North America. Advocating a new direction in forest management, they explore the promise of "restoration forestry" -- an ecologically based approach that seeks to establish forest structures in which fire can once again serve as a beneficial process rather than as a destructive aberration.

The book begins with an overview of fundamentals: why traditional forestry tried to exclude fire from forests, why that attempt failed, and why foresters and ecologists now recognize the need for management based on how natural ecosystems operate. Subsequent chapters consider: how fire's historic role provides a foundation for designing restoration strategies; why a hands-off approach will not return forests to their historical condition; how management goals influence the strategies used in restoration forestry.

The second part of the book presents case studies of restoration projects in the western United States and Canada, representing different forest types, different historic fire regimes, and contrasting management goals. For each project, the authors describe why and how the project is being conducted, profile forest conditions, and describe methods of treatment. They also report what has been accomplished, identify obstacles to restoration, and offer their candid but understanding evaluation. Mimicking Nature's Fire concludes by placing restoration forestry in the broad context of conserving forests worldwide and outlining factors critical for its success.

Molds, Mushrooms, and Mycotoxins was first published in 1975. Minnesota Archive Editions uses digital technology to make long-unavailable books once again accessible, and are published unaltered from the original University of Minnesota Press editions.

As Professor Christensen has made evident in his earlier books, including The Molds and Man,fungi are significantly interesting in their life-styles and in the many ways in which they affect man. Here he continues his exploration of the lives of the fungi and their relation to man, focusing on the harmful or dangerous effects which certain molds, mushrooms, and other fungi can have on human beings.

The first several chapters deal with fungi that are toxic in one way or another: either the fungi themselves are toxic when consumed, as with poisonous mushrooms and ergot, or the fungi secrete toxic compounds that diffuse into the substance on which they grow, making that substance toxic when eaten. He discusses hallucinogenic as well as poisonous mushrooms and provides extensive information about mycotoxins in human and animal foods, which are recently discovered health hazards.

Other chapters deal with fungus spores, which are a major cause of respiratory allergies, and with fungi which are predators or parasites of insects and nematodes. A chapter is devoted to fungus infections of man and animals, which at times constitute a serious public health problem. Another chapter discusses the nature, cause, and prevention of wood decay in trees and buildings. In a final chapter the author discusses some aspects of organic evolution in general as a background for presenting theories and facts on the evolution of fungi. He summarizes some of the ways in which fungi enter into our lives and economy, and looks to the role of fungi in the future.

The illustrations, in both black and white and color, show some of the fungi and processes that are discussed.

Plants produce a considerable number of structures of one kind, like leaves, flowers, fruits, and seeds, and this reiteration is a quintessential feature of the body plan of higher plants. But since not all structures of the same kind produced by a plant are identical—for instance, different branches on a plant may be male or female, leaf sizes in the sun differ from those in the shade, and fruit sizes can vary depending on patterns of physiological allocation among branches—a single plant genotype generally produces a multiplicity of phenotypic versions of the same organ.

Multiplicity in Unity uses this subindividual variation to deepen our understanding of the ecological and evolutionary factors involved in plant-animal interactions. On one hand, phenotypic variation at the subindividual scale has diverse ecological implications for animals that eat plants. On the other hand, by choosing which plants to consume, these animals may constrain or modify plant ontogenetic patterns, developmental stability, and the extent to which feasible phenotypic variants are expressed by individuals.

An innovative study of the ecology, morphology, and evolution of modular organisms, Multiplicity in Unity addresses a topic central to our understanding of the diversity of life and the ways in which organisms have coevolved to cope with variable environments.