Grimmias of the World

Primary Succession and Ecosystem Rehabilitation by Lawrence Walker and Roger del Moral begins with a good introduction suggesting why one would want to learn about this topic. The authors’ treatments on soils, soil development, and soil processes are excellent. They describe early colonists of bare soil sites and discuss factors that influence the rate of early succession. Many ecological and climatic factors are well described, as is the role of modeling in the study and analysis of successional processes. Modeling, experimentation, and the search for generalities are three possible tools the authors recognize for analyzing successional processes, however they focus their discussion on modeling, providing minimal dialogue on the other two methods. The universal principles and theories that guide any rehabilitation project are thoroughly covered by the authors, but few specific examples are provided. Those that are included are small in scale, generally comprised of experimental research plots or severely disturbed mining areas. While useful for those working in such dimensions, it is not representative of the large-scale rehabilitation projects frequently undertaken in western North America following wildfire. Such projects can exceed 50,000 acres in size, and are commonly greater than 10,000 acres. The U.S. Forest Service and the Bureau of Land Management spend millions of dollars each year on these types of projects, many of which are actively rehabilitated due to the presence of ‘‘transformer’’ species such as exotic annual grasses. In the Great Basin, the introduction of cheatgrass, Bromus tectorum, has drastically altered successional pathways and fire regimes. The concept of ‘‘transformer’’ species invasion and implementation of rehabilitation treatments under such conditions is not addressed, but would have provided additional relevant discussion topics. The glossary is excellent and the discussion of successional theory is thorough. However, I was disappointed that bryophytes and lichens are addressed only in broad categorical terms throughout the book. The decline of Sphagnum moss from air pollution and acid rain is discussed in brief, but few other cryptogams are directly mentioned. Many primary successional sites I am aware of have high cover of either mosses or lichens or both; however, such sites were discussed only in terms of their vascular plants. I contend that cryptogams are also capable of modifying a sites’ microclimate sufficiently to be considered successional species. Vascular plants that serve as nurse plants are discussed, but the importance of cryptogams in this same role is not. Until the last two chapters, this book does not emphasize the concept of stochastic ecology and how it can drive succession. The authors do little to promote the more modern concept in plant ecology of ‘‘state and transition’’, though it is mentioned in the discussion of rehabilitation in Chapter 8 and in ‘‘Future Directions’’ in Chapter 9. I would not recommend this book for students. In fact, this book illustrates the need for a modern treatment on primary succession with more emphasis on the critical role of cryptogams. While it serves as a good reference on theoretical modeling of successional processes, most readers of THE BRYOLOGIST will be disappointed by the few references to cryptogams. —ROGER ROSENTRETER, Bureau of Land Management, Idaho State Office, Boise, Idaho 83709, U.S.A.