Patrick S. Bourgeron

Alpine treeline of western North America; linking organism-to-landscape dynamics

Although the ecological dynamics of the alpine treeline ecotone are influenced by climate, it is an imperfect indicator of climate change. Mechanistic processes that shape the ecotone—seed rain, seed germination, seedling establishment and subsequent tree growth form, or, conversely tree dieback—depend on microsite patterns. Growth forms affect wind and snow, and so develop positive and negative feedback loops that create these microsites. As a result, complex landscape patterns are generated at multiple spatial scales. Although these mechanistic processes are fundamentally the same for all forest-tundra ecotones across western North America, factors such as prior climate, underlying geology and geomorphology, and genetic constraints of dominant tree species lead to geographic differences in the responses of particular ecotones to climate change.

Development at the wildland–urban interface and the mitigation of forest-fire risk

This work addresses the impacts of development at the wildland–urban interface on forest fires that spread to human habitats. Catastrophic fires in the western United States and elsewhere make these impacts a matter of urgency for decision makers, scientists, and the general public. Using a simple fire-spread model, along with housing and vegetation data, we show that fire size probability distributions can be strongly modified by the density and flammability of houses. We highlight a sharp transition zone in the parameter space of vegetation flammability and house density. Many actual fire landscapes in the United States appear to have spreading properties close to this transition. Thus, the density and flammability of buildings should be taken into account when assessing fire risk at the wildland–urban interface. Moreover, our results highlight ways for regulation at this interface to help mitigate fire risk.

Tree spatial patterns and environmental relationships in the forest–alpine tundra ecotone at Niwot Ridge, Colorado, USA

Forest–alpine tundra ecotones (FTEs) are dynamic transition zones between forest and alpine tundra ecosystems that play an important role in regulating ecological processes, which are in turn directly influenced by the spatial patterns of trees and environmental constraints such as topography and climate. Our objectives were to characterize the spatial patterns of tree species and size classes, determine whether spatial patterns of trees differed among three FTE types, and examine FTE- and tree-environmental relationships in our study area on Niwot Ridge, CO, USA. Overall, spatial aggregation was more extensive for seedlings than saplings or trees. Distributions were largely random in limber pine but were highly aggregated in Engelmann spruce and especially subalpine fir, reflecting these species’ relative shade tolerance and expected sequence of establishment following disturbance. Fragmented and patchy tree distributions were observed in the FTE with the most heterogeneous topography, characterized by high relief and associated physical disturbances. The least patchy distributions were associated with the FTE containing a relative absence of disturbance. Intermediate levels of tree aggregation were associated with low topographic relief and presence of meadows and wetlands. Our results emphasize the importance of spatial structure as an initial controlling factor of vegetation pattern in FTEs occurring in the same landscape.

Perspectives pour une Géobiologie des Montagnes

This is a curious little book, and is rather unclassifiable in today’s diversified fields of environmental sciences. The book is worthwhile for the useful compiled historical information and ideas that it presents, but is also highly frustrating in form and substance, even for a French reader. Indeed, the primary drawback for many non-French readers will be that the text is primarily in French. Only short, albeit informative, abstracts in English are found at the beginning of each chapter. The author, Professor Paul Ozenda, now retired, had a distinguished and productive career as a geobotanist, for lack of a better word, spanning over half of the twentieth century. He was a pioneer and leader in the disciplines of plant and vegetation ecology in Europe during that period. It is remarkable that, at an age when some North American ecologists might be content to play golf, Professor Ozenda still exhibits knowledge of and passion for his profession. Indeed, the book is a largely personal reflection on the vast field of mountain biogeography and ecology, in the widest sense of these two terms. The contributions of this book that may be of interest to today’s practitioners fall into three broad categories. First, the book describes the historical development of a particular approach to the study of mountains, their environment, biology, and ecology, which was highly successful and widespread during the past century. It is extremely advantageous to recognize how past advances in this area have led to contemporary approaches to scientific issues. Second, it contains useful information (interpretations, data, maps, citations) that a younger generation of scientists not taught in the fields covered may find difficult to access elsewhere, since many aspects of these materials are no longer part of modern curricula. Third, it contains ideas and concepts that are of use during the present period of large-scale production of maps, monitoring schemes, and interdisciplinary approaches to ecological issues. In essence, the book makes us aware that there is nothing really new in our self-described innovative approaches to ecology and that, successful or not, our predecessors also considered that only integration and synthesis would yield full knowledge and understanding of mountain ecosystems at multiple spatial and temporal scales. Unfortunately, the book suffers from serious weaknesses. Many portions of the text contain arcane jargon that few modern students of the field will feel enthusiastic about and that, in this reviewer’s opinion, has lost its interest and relevance. This is regrettable because the concepts hidden behind the jargon can be interesting and relevant. Furthermore, the author compounds this problem by lengthy discussions of issues that, again in this reviewer’s opinion, can be perceived as sterile refinements of obsolete systems of ideas. This is even more unfortunate, because buried under rather unexciting discussions in what seems to be a foreign language (no pun intended), some significant problems are explored: the distributions of species in response to large geologic phenomena, climatic variability over large areas and multiple temporal scales, and the potential responses of mountain ecosystems to climatic and land use changes, among other topics. The book is well organized to achieve objectives that are clearly formulated in the ‘‘Avant-propos’’ or preamble (pp. V–VII). The ten chapters are articulated in three parts. The first part (chapters 1–3) defines the object of the book, i.e., the mountain systems, their spatial scales, their geographic distributions, and climatic complexity. It also includes a short discussion of the alpine-subalpine ecotone. The second part (chapters 4–6) tackles different dimensions of biodiversity in mountains with a special focus on species richness and withincommunity diversity. The third part (chapters 7–10) attempts a synthesis through integration to explain the vegetation and its floristic composition in mountain systems all over the world. The author presents a conceptual model of vegetation distributions for the European Alps and endeavors to expand it to the rest of the world. This attempt exemplifies both the contributions and weaknesses noted earlier. On one hand, a tremendous amount of useful information is presented. On the other hand, the lengthy discussion of obscure systems of classification borders on the tedious and the frivolous. The book would have benefited from de-emphasizing the typology of mountain systems and expanding the section on the dynamics of vegetation patterns. In summary, this is a really difficult book to review fairly. As the reflection of a European scientist who has contributed to his field of study, it has noteworthy dimensions, especially for students of the Alps. It can be used today to provide background information on integrated mountain ecology. However, it is of limited use for generating new ideas. The choice of citations limits its value as a reference book. For example, this reviewer does not understand the rationale for excluding major North American references on the topic (e.g., Daubenmire, Billings, Peet) while other less relevant references are included. This is also true for the omission of important European references. Still, this book provides some remarkable insights into past work that has influenced the field during the mid-twentieth century.

Plant species richness and species-area relations in a shortgrass steppe in Colorado

Plant species richness and species-area relations were examined for three landscapes (toposequences), each with a summit or upland, a midslope and a toeslope or lowland, in a shortgrass steppe in Colorado. The number of plant species in the largest plot size (0.16 ha) varied from 38 to 53. Neither the exponential relationship: s = a + b log A, nor the power function: S = cAz fit the data equally well in all situations. The processes acting upon species diversity here seem to operate at two spatial scales. The number of species in plots smaller than 3 m 2 was independent of the total number of species in the 0.16-ha plots and was constrained by the presence of the dominant bunchgrasses. Beyond 3 m 2 , species number in each plot size was a function of the total number of species in the 0.16-ha plot.

Changes in biodiversity and trade-offs among ecosystem services, stakeholders, and components of well-being: the contribution of the International Long-Term Ecological Research network (ILTER) to Programme on Ecosystem Change and Society (PECS)

The International Long-Term Ecological Research (ILTER) network comprises > 600 scientific groups conducting site-based research within 40 countries. Its mission includes improving the understanding of global ecosystems and informs solutions to current and future environmental problems at the global scales. The ILTER network covers a wide range of social-ecological conditions and is aligned with the Programme on Ecosystem Change and Society (PECS) goals and approach. Our aim is to examine and develop the conceptual basis for proposed collaboration between ILTER and PECS. We describe how a coordinated effort of several contrasting LTER site-based research groups contributes to the understanding of how policies and technologies drive either toward or away from the sustainable delivery of ecosystem services. This effort is based on three tenets: transdisciplinary research; cross-scale interactions and subsequent dynamics; and an ecological stewardship orientation. The overarching goal is to design management practices taking into account trade-offs between using and conserving ecosystems toward more sustainable solutions. To that end, we propose a conceptual approach linking ecosystem integrity, ecosystem services, and stakeholder well-being, and as a way to analyze trade-offs among ecosystem services inherent in diverse management options. We also outline our methodological approach that includes: (i) monitoring and synthesis activities following spatial and temporal trends and changes on each site and by documenting cross-scale interactions; (ii) developing analytical tools for integration; (iii) promoting trans-site comparison; and (iv) developing conceptual tools to design adequate policies and management interventions to deal with trade-offs. Finally, we highlight the heterogeneity in the social-ecological setting encountered in a subset of 15 ILTER sites. These study cases are diverse enough to provide a broad cross-section of contrasting ecosystems with different policy and management drivers of ecosystem conversion; distinct trends of biodiversity change; different stakeholders’ preferences for ecosystem services; and diverse components of well-being issues.

Suitability for conservation as a criterion in regional conservation network selection

The process of selecting candidate areas for inclusion in a regional conservation network should include not only delineating appropriate land units for selection and defining targets for representing features of interest, but also determining the suitability of land units for conservation purposes. We developed an explicit rating of conservation suitability by applying fuzzy-logic functions in a knowledge base to ecological condition and socio-economic attributes of land units in the interior Columbia River basin, USA. Suitability was converted to unsuitability to comprise a cost criterion in selecting regional conservation networks. When unsuitability was the sole cost criterion or was combined with land area as cost, only about one-third of the area selected was rated suitable, due to inclusion of unsuitable land to achieve representation of conservation targets (vegetation cover-type area). Selecting only from land units rated suitable produced networks that were 100% suitable, reasonably efficient, and most likely to be viable and defensible, as represented in our knowledge-based system. However, several conservation targets were not represented in these networks. The tradeoff between suitability and effectiveness in representing targets suggests that a multi-stage process should be implemented to address both attributes of candidate conservation networks. The suitability of existing conservation areas was greater than that of most alternative candidate networks, but 59% of land units containing conservation areas received a rating of unsuitable, due in part to the presence of units only partially occupied by conservation areas, in which unsuitability derived from conditions in non-conserved areas.

Methods for Determining Historical Range of Variability

Previous chapters have emphasized the dynamic nature of ecosystems, including the occurrence of periodic disturbances. Consequently, current ecosystem composition, structure, and function are likely to operate within ranges of variability that arise from climatic variability, disturbance, and the effects of human activities (Bourgeron and Jensen, 1994; Kaufmann et al., 1994; Morgan et al., 1994; Cissel et al., 1998). Understanding the magnitude and direction of anthropogenic impacts requires knowledge of the range of fluctuations historically experienced by ecosystems as a result of variability in climatic conditions, disturbance regimes, and their interactions (Swetnam and Betancourt, 1998). Therefore, the determination of the historical range of variability (HRV) in key ecosystem patterns and processes is an important part of ecological assessments and results in the characterization of the range of variability in conditions to which ecosystem components (e.g., species) are adapted (Bourgeron and Jensen, 1994; Morgan et al., 1994; Swanson et al., 1994). HRV provides a baseline for evaluating anthropogenic changes and a means for identifying the potential for surprise events to occur (Holling, 1986). Historical conditions serve as a model of the functioning of ecosystems under unmodified disturbance regimes and alternative land-use scenarios. Ecosystem patterns and processes operate at multiple hierarchically structured spatial and temporal scales, and therefore the determination of HRV should be conducted at scales that both meet the objectives of the assessment and are appropriate for the patterns and processes of interest (Bourgeron et al., 1994).

Making Transparent Environmental Management Decisions

An Overview of the Ecosystem Management Decision-Support System.- NetWeaver.- Criterium DecisionPlus.- Use of EMDS in Conservation and Management Planning for Watersheds.- The Integrated Restoration and Protection Strategy of USDA Forest Service Region 1: A Road Map to Improved Planning.- Evaluating Wildfire Hazard and Risk for Fire Management Applications.- Landscape Evaluation and Restoration Planning.- Ecological Research Reserve Planning.- Forest Conservation Planning.- Wildlife Habitat Management.- Measuring Biological Sustainability via a Decision Support System: Experiences with Oregon Coast Coho Salmon.- EMDS 5.0 and Beyond.- Synthesis and New Directions.

Ecosystem Characterization and Ecological Assessments

Ecological assessments are an important component of any strategy for making or reevaluating land management and regulatory decisions (see Chapters 1, 9, and 35; also Slocombe, 1993; Jensen and Bourgeron, 1994; Bourgeron et al., 1995). An important objective of ecological assessments is the identification, location, and description of the biotic and abiotic features of a landscape. Landscape features exhibit heterogeneity at a variety of scales (Turner et al., 1995). This heterogeneity is characterized by identifying relevant patterns and the processes that produce patterns in a landscape (Bourgeron and Jensen, 1994). Distinct patterns and processes occur at a variety of spatial and temporal scales of organization (see Chapter 2). For ecological assessments, an explicit understanding is needed of the scaled relationships of biological and biophysical characteristics from site to regional scales (Lessard, 1995; Lessard et al., 1999). Therefore, the characterization process is a multiscaled approach conducted within a hierarchical framework (Bourgeron and Jensen, 1994; Hann et al., 1994; Bourgeron et al., 1995; Jensen et al., 1996).