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

In northern Patagonia, Argentina we quantify changes in fire frequency along a gradient from mesic Nothofagus dombeyi forest to xeric woodlands of Austrocedrus chilensis at the steppe ecotone, and we examine patterns of vegetation change coincident with the changes in fire regimes across a range of spatial scales. At a regional scale changes in land cover types are documented by comparing 1:250 000 scale cover type maps from 1913 and 1985. Changes in landscape structure are analyzed by comparing vegetation patterns on 1:24 000 scale aerial photographs taken in 1940 and 1970. Fire frequency peaked in the late nineteenth-century due to widespread burning and clearing of forests by European settlers late in the century. Subsequently, fire frequency declined dramatically about 1910 due to the cessation of intentional fires and has remained low due to increasingly effective fire exclusion. At a regional scale there has been a dramatic increase during the twentieth century in the proportion of forest cover relative to areas mapped as recent burns or shrublands in 1913. Remnant forest patches that survived the widespread late-nineteenth century burning have coalesced to form more continuous forest covers, and formerly continuous areas of shrublands have become dissected by forest. Under reduced fire frequency there has been a shift in dominance from short-lived resprouting species (mostly shrubs) towards longer-lived species and obligate seed-dispersers such as Austrocedrus chilensis and Nothofagus dombeyi. Due to limited seed dispersal of these tree species, the spatial configuration of remnant forest patches plays a key role in subsequent changes in landscape pattern.

Fire-induced changes in northern Patagonian landscapes

. In the Colorado Front Range, disturbances and climatic variation influence stand structure of ponderosa pine (Pinus ponderosa) along the lower timberline ecotone. Over the past 100 years there has been a shift to a greater density and extent of ponderosa pine at the forest-grassland boundaries. Ponderosa pine regeneration at lower timberline appears to be influenced by fires in the 1860s and decreased grazing pressure in the 1970s–1980s. Climatic variation may also have influenced age structure, even though analyses of age structure at a 10-year class scale prevented the detection of climatic influences occurring at a finer scale. These changes in disturbance regimes, possibly together with moister springs/early summers, created favourable conditions for the increase in density and extent of ponderosa pine at lower timberline ecotone.

Disturbance and Climatic Influences on Age Structure of Ponderosa Pine at the Pine/Grassland Ecotone, Colorado Front Range

The effects of periodic gales on Nothofagus (southern beech) stand devel- opment and landscape dynamics were studied in a 10.4-km2 study area in the Sierra de las Pinturas, part of the Andes in Argentine Tierra del Fuego. We reconstructed blowdown history (patch sizes, dates of origin, return intervals) since the late 1700s to assess how periodic large-scale wind disturbance influenced landscape pattern in a relatively simple system. Most previous studies have focused on single storms in more diverse forests and in landscapes influenced by several disturbance types and human activities. Boundaries of post-blowdown stands were digitized from aerial photographs and analyzed within a geo- graphic information system. Ages of blowdowns and return intervals were determined from scars, growth releases, and maximum tree ages. Discrete blowdown patches (0.1 to >100 ha) covered two-thirds of the study area and ranged from 19 to -200 yr of age, with 20- 30 yr between major events. The meteorology of these storms was unknown, but we suspect they were caused by intense low-pressure systems originating in Antarctica. The mean return interval for 34 sites was 145 yr, with a range of 103-218 yr. Based on treefall size distributions, most stands blown over in the past 100 yr were even-aged, with mean tree dbh (diameter at breast height) between 20 and 32 cm. Aerial photographs taken in 1970 were used for before-and-after comparisons of a 1972 blowdown. Seventy-one percent of the area blown over in 1972 was even-aged, and 35% of the boundaries from this storm exactly coincided with previous stand boundaries. Damage patterns from storms in 1924 and 1972 suggested that forests located on valleys parallel to the wind, windward side slopes, and possibly upper leeward slopes were most vulnerable to blowdown, but few landscape positions escaped being hit by repeated storms. Return intervals were not sig- nificantly related to slope, elevation, or aspect; but surprisingly, shorter return intervals were associated with deeper soils. The landscape pattern of blowdown and recovery shifted over time because of variation among individual storms and because a small proportion of old-growth stands were converted to blowdowns and vice versa. Browsing by guanacos (Lama guanaco), a large native camelid, has severely inhibited tree regeneration during the past 75 yr in small blowdowns and the perimeters of larger ones, converting some stands to open meadows and incipient alpine communities. In the relatively simple Noth- ofagus forests of Tierra del Fuego, periodic gales are the main determinants of forest structure and pattern across a range of scales from small patches to entire landscapes.

Blowdown history and landscape patterns in the andes of tierra del fuego, argentina

Fire History and Vegetation Changes in Northern Patagonia, Argentina

We investigated interannual and multidecadal variability in fire regimes, as related to climate and human land-use in Pike National Forest, central Colorado. Short and long-term trends in fire-scar...

Thomas T. Veblen

Papers

Fire-induced changes in northern Patagonian landscapes

Disturbance and Climatic Influences on Age Structure of Ponderosa Pine at the Pine/Grassland Ecotone, Colorado Front Range

Blowdown history and landscape patterns in the andes of tierra del fuego, argentina

Fire History and Vegetation Changes in Northern Patagonia, Argentina

Climatic and human influences on fire history in Pike National Forest, central Colorado