Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

Western United States forest wildfire activity is widely thought to have increased in recent decades, yet neither the extent of recent changes nor the degree to which climate may be driving regional changes in wildfire has been systematically documented. Much of the public and scientific discussion of changes in western United States wildfire has focused instead on the effects of 19th- and 20th-century land-use history. We compiled a comprehensive database of large wildfires in western United States forests since 1970 and compared it with hydroclimatic and land-surface data. Here, we show that large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons. The greatest increases occurred in mid-elevation, Northern Rockies forests, where land-use histories have relatively little effect on fire risks and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt.

/pdf/warming-and-earlier-spring-increase-western-u-s-forest-33qvd39h8z.pdf

Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity

■ Abstract Contributions from the field of population biology hold promise for understanding and managing invasiveness; invasive species also offer excellent opportunities to study basic processes in population biology. Life history studies and demographic models may be valuable for examining the introduction of invasive species and identifying life history stages where management will be most effective. Evolutionary processes may be key features in determining whether invasive species establish and spread. Studies of genetic diversity and evolutionary changes should be useful for

/pdf/the-population-biology-of-invasive-species-bdndjv53b3.pdf

The Population Biology of Invasive Species

Climate change 2014 - Synthesis Report

Although the potential genetic risks associated with rare or endangered plants and small populations have been discussed previously, the practical role of population genetics in plant conservation remains unclear. Using theory and the available data, we examine the effects of genetic drift, inbreeding, and gene flow on genetic diversity and fitness in rare plants and small populations. We identify those circumstances that are likely to put these plant species and populations at genetic risk. Warning signs that populations may be vulnerable include changes in factors such as population size, degree of isolation, and fitness. When possible, we suggest potential management strategies.

/pdf/population-genetic-consequences-of-small-population-size-3onkvtfxng.pdf

POPULATION GENETIC CONSEQUENCES OF SMALL POPULATION SIZE: Implications for Plant Conservation

Genetic and evolutionary consequences of small population size in plants: implications for conservation.

The purpose of this paper is to promote a broad and flexible perspective on ecological restoration of Southwestern (U.S.) ponderosa pine forests. Ponderosa pine forests in the region have been radically altered by Euro-American land uses, including livestock grazing, fire suppression, and logging. Dense thickets of young trees now abound, old- growth and biodiversity have declined, and human and ecological communities are in- creasingly vulnerable to destructive crown fires. A consensus has emerged that it is urgent to restore more natural conditions to these forests. Efforts to restore Southwestern forests will require extensive projects employing varying combinations of young-tree thinning and reintroduction of low-intensity fires. Treatments must be flexible enough to recognize and accommodate: high levels of natural heterogeneity; dynamic ecosystems; wildlife and other biodiversity considerations; scientific uncertainty; and the challenges of on-the-ground im- plementation. Ecological restoration should reset ecosystem trends toward an envelope of ''natural variability,'' including the reestablishment of natural processes. Reconstructed historic reference conditions are best used as general guides rather than rigid restoration prescriptions. In the long term, the best way to align forest conditions to track ongoing climate changes is to restore fire, which naturally correlates with current climate. Some stands need substantial structural manipulation (thinning) before fire can safely be reintro- duced. In other areas, such as large wilderness and roadless areas, fire alone may suffice as the main tool of ecological restoration, recreating the natural interaction of structure and process. Impatience, overreaction to crown fire risks, extractive economics, or hubris could lead to widespread application of highly intrusive treatments that may further damage forest ecosystems. Investments in research and monitoring of restoration treatments are essential to refine restoration methods. We support the development and implementation of a diverse range of scientifically viable restoration approaches in these forests, suggest principles for ecologically sound restoration that immediately reduce crown fire risk and incrementally return natural variability and resilience to Southwestern forests, and present ecological perspectives on several forest restoration approaches.

/pdf/ecological-restoration-of-southwestern-ponderosa-pine-533pouc837.pdf

Ecological restoration of southwestern ponderosa pine ecosystems: a broad perspective

Section One: Population biology and genetics of rare species Section Two: Distribution and sampling of genetic variation Section Three: Management and assessment of off-site collections Section Four: Conservation strategies for genetic diversity.

Genetics and conservation of rare plants.

Genetics and Conservation of Rare Plants

2 Environmental Forestry Research, Weyerhaeuser Company, Tacoma, Washington 98422 USA Abstract. Although most temperate forests are actively managed for timber production, few data exist regarding the long-term effects of forest management on understory plant communities. We investigated the responses of understory communities to a factorial com- bination of silvicultural-thinning and nutrient-addition treatments maintained for 12-16 yr in a set of 21-27 yr old Douglas-fir (Pseudotsuga menziesii) plantations. The four thinning levels span those used operationally (final stem densities of 494-1680 trees/ha); the two fertilization levels included a control and N addition in the form of urea at ;60 kg N·ha 21 ·yr 21 , about twice the dosage used operationally. Understory vegetation cover showed significant effects of thinning, with the highest thinning level resulting in the highest observed cover values. However, in some cases low levels of thinning resulted in a reduction in understory cover compared to unthinned con- trols. Understory vegetation declined dramatically in response to urea fertilization, with up to a 10-fold drop in herb-layer cover in unthinned stands. Species richness showed a simpler response to treatments, increasing in response to thinning, but decreasing in response to fertilization. Examination of species-area relationships indicated that effects of thinning and fertilization on species richness were similar across the range of spatial scales examined. Tree canopy cover, assessed by means of hemispherical photograph analysis, increased with fertilization, and estimated understory light levels decreased with fertilization, but neither showed a significant response to thinning at the time of measurement (12-16 yr after tree removal). Thus, treatment effects on understory cover and species richness were not a simple function of canopy cover or estimated light availability. Rather, there was a weak positive relationship between estimated understory light flux and vascular plant cover and diversity in nonfertilized plots, and no such relationship in fertilized plots. The lack of correspondence between treatment effects on canopy cover and understory vegetation may be due to time lags in understory response to changes in canopy cover or to treatment effects not mediated by light availability, such as physical disturbance during thinning operations and toxicity responses following application of urea fertilizer. Species-specific responses to treatments were in part predictable as a function of plant life-form and edaphic association: species affinity for high soil moisture was the best predictor of fertilization responses, while life-form was the best predictor of thinning responses, with ferns and graminoids showing the largest positive responses to thinning. The successional status and stature of understory plant species were not significantly related to treatment responses. In sum, our results indicate that silvicultural thinning and fertilization can have large effects on understory plant diversity and community composition. However, such effects were not a simple function of understory light levels, and conventional ''functional types'' were of only limited value in predicting species-specific responses to silvicultural treatments.

https://faculty.washington.edu/chalpern/Thomasetal1999.pdf

Donald A. Falk

Papers

Genetic and evolutionary consequences of small population size in plants: implications for conservation.

Ecological restoration of southwestern ponderosa pine ecosystems: a broad perspective

Genetics and conservation of rare plants.

Genetics and Conservation of Rare Plants

Plant diversity in managed forests: understory responses to thinning and fertilization