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

Statistics for Spatial Data.

https://hal.archives-ouvertes.fr/hal-00457602/document

A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests

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Modern Applied Statistics With S

The terrestrial carbon sink has been large in recent decades, but its size and location remain uncertain. Using forest inventory data and long-term ecosystem carbon studies, we estimate a total forest sink of 2.4 ± 0.4 petagrams of carbon per year (Pg C year–1) globally for 1990 to 2007. We also estimate a source of 1.3 ± 0.7 Pg C year–1 from tropical land-use change, consisting of a gross tropical deforestation emission of 2.9 ± 0.5 Pg C year–1 partially compensated by a carbon sink in tropical forest regrowth of 1.6 ± 0.5 Pg C year–1. Together, the fluxes comprise a net global forest sink of 1.1 ± 0.8 Pg C year–1, with tropical estimates having the largest uncertainties. Our total forest sink estimate is equivalent in magnitude to the terrestrial sink deduced from fossil fuel emissions and land-use change sources minus ocean and atmospheric sinks.

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A Large and Persistent Carbon Sink in the World’s Forests

QUESTIONS: Increased wildfire activity is resulting in plant community‐type conversions worldwide. In some regions, fire‐sensitive forests are being replaced by flammable fire‐resilient communities, increasing the likelihood of reburning due to positive fire feedbacks. Here we evaluated whether fire severity affects post‐fire plant community flammability attributes that lead to community‐type conversions and changes in the likelihood of reburning. Specifically, we assessed how fire severity, the dominant pre‐fire vegetation, and distance to unburned remnant forest may shape post‐fire community properties and flammability trajectories in northwestern Patagonia. LOCATION: Northwestern Patagonia, Argentina. METHODS: We repeated sampling of Nothofagus pumilio, Nothofagus dombeyi, and Austrocedrus chilensis forests and native shrublands (composed of multiple shrub species) two and 18 years after fires that burned at low‐ to very high‐severity levels, and measured community structure and flammability attributes. RESULTS: Eighteen years after fire, forests that burned at moderate to very high severity were unable to recover and were replaced by more flammable shrublands and grasslands. Following low‐severity fire, fine‐fuel density was lower and forest recovery was enhanced by greater survival of remnant seed trees. Burnt shrublands increased in abundance across all severity classes but attained highest fine‐fuel production after moderate‐ to very high‐severity fire. CONCLUSIONS: Low fire severity, by enabling regeneration of forests that are less flammable than shrublands, diminishes the likelihood of reburning, thus establishing a negative feedback favorable to forest perpetuation. Conversely, moderate to very high fire severity leads to a positive feedback by promoting conversion to shrublands and greater fine‐fuel accumulation. This increases the likelihood of reburning, reinforcing the persistence of pyrophytic communities and favoring landscape‐scale loss of fire‐sensitive forests. This fire severity‐mediated positive feedback may in many regions worldwide further amplify warming‐related wildfire activity increases, posing serious threats to the persistence of fire‐sensitive ecosystems.

Increased fire severity triggers positive feedbacks of greater vegetation flammability and favors plant community‐type conversions

Increasing rates of subalpine tree mortality linked to warmer and drier summers

In the temperate forests of the southern Andes, southern beech species (Nothofagus), the dominant tree species of the region, experience severe defoliation caused by caterpillars of the Ormiscodes genus (Lepidoptera: Saturniidae). Despite the recent increase in defoliation frequency in some areas, there is no quantitative information on the spatial extent and dynamics of these outbreaks. This study examines the spatial patterns of O. amphimone outbreaks in relation to landscape heterogeneity. We mapped defoliation events caused by O. amphimone in northern (ca. 40–41°S) and southern Patagonian (ca. 49°S) Nothofagus forests from Landsat imagery and analyzed their spatial associations with vegetation cover type, topography (elevation, slope angle, aspect) and mean annual precipitation using overlay analyses. We used these data and relationships to develop a logistic regression model in order to generate maps of predicted susceptibility to defoliation by O. amphimone for each study area. Forests of N. pumilio are typically more susceptible to O. amphimone outbreaks than lower elevation forests of other Nothofagus species (N. dombeyi and N. antarctica). Stands located at intermediate elevations and on gentle slopes (<15°) are also more susceptible to defoliation than higher and lower elevation stands located on high angle slopes. Stands in areas with intermediate to high precipitation, relative to the distribution of Nothofagus along the precipitation gradient, are more susceptible to O. amphimone attack than are drier areas. Our study represents the first mapping and spatial analysis of insect defoliator outbreaks in Nothofagus forests in South America.

Spatial prediction of caterpillar (Ormiscodes) defoliation in Patagonian Nothofagus forests

Tree susceptibility to potentially lethal agents is determined not only by attributes of individual trees, but also by neighborhood effects at a range of scales. For example, effects of disturbances on individual trees are often contingent on the size, configuration, and other properties of neighboring trees. Wildfires can modify postfire properties of individual trees as well as of entire forest stands, both of which can affect subsequent ecological processes, including subsequent disturbances. In recent years, much has been learned about how disturbances interact, but numerous questions concerning underlying mechanisms remain unresolved. For example, the relative importance of forest properties at different spatial scales in determining how fires affect forest susceptibility to subsequent disturbances is not well understood. This study explicitly compares the relative importance of tree vs. fine-scale neighborhood effects (e.g., stand properties at <7 m radii), on susceptibility to a 1940s' spruce beetle outbreak. Attributes of individual trees and of stand structure were spatially reconstructed at five 250-m2 sites that were partly burned in the late 19th century and then affected by spruce beetle outbreak in the 1940s. Random Forest models and classification trees were used to compare the relative importance of variables for susceptibility to spruce beetle attack. Individual tree properties (diameter at breast height and age) were the most important predictors of susceptibility to the outbreak across all sites combined and at each of the sites individually. In contrast, neighborhood effects were poor predictors of susceptibility. This study suggests wildfires reduce susceptibility to outbreaks primarily by reducing the size of postfire live trees and only secondarily by modifying stand structure. One implication of this is that management strategies that aim to modify stand structure over large areas in order to reduce susceptibility to spruce beetle outbreaks may be unnecessarily intensive.

https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecs2.1485

The relative importance of tree and stand properties in susceptibility to spruce beetle outbreak in the mid-20th century

This paper reports on the capability of the long-lived conifer Pilgerodendron uviferum in southwestern South America to record fire scars, making it the southernmost tree-ring fire recording species on Earth. We present detailed descriptions of the fire-scar morphology of this species and compare tree-ring fire-scar dates to independent sources of fire dates. The fire scars found on Pilgerodendron uviferum are morphologically similar to those found on conifers in western North America. All fire scars were crossdated on 80 out of 96 sampled cross-sections collected at 8 dispersed sites. Groups of micro-rings were the most common anatomical feature that impeded crossdating of fire-scar dates. A total of 597 fire-scar tips were successfully crossdated on these 80 cross-sections. The average number of fire scars per cross-section was 7.4, and the full collection of crossdated fire scars spanned from 1570 to 2004 AD. The crossdated fire-scar dates were highly synchronous within stands, and years of a...

Thomas T. Veblen

Papers

Increased fire severity triggers positive feedbacks of greater vegetation flammability and favors plant community‐type conversions

Increasing rates of subalpine tree mortality linked to warmer and drier summers

Spatial prediction of caterpillar (Ormiscodes) defoliation in Patagonian Nothofagus forests

The relative importance of tree and stand properties in susceptibility to spruce beetle outbreak in the mid-20th century

Pilgerodendron uviferum: The Southernmost Tree-Ring Fire Recorder Species