Robert A. Dull

California Lutheran University · Earth and Environmental Sciences

The Tierra Blanca Joven (TBJ) eruption of the Ilopango caldera in central El Salvador was one of the largest Holocene volcanic events in Central America, and its ecological and cultural impacts were felt throughout El Salvador and adjoining areas of Guatemala and Honduras. Early radiocarbon measurements established a ca. A. D. 260 ± 114 calendar da...

Pre-Columbian farmers of the Neotropical lowlands numbered an estimated 25 million by 1492, with at least 80 percent living within forest biomes. It is now well established that significant areas of Neotropical forests were cleared and burned to facilitate agricultural activities before the arrival of Europeans. Paleoecological and archaeological e...

The greatest atmospheric aerosol loading event of the past two millennia occurred in the year ca. AD 536. A ‘dry fog’ (dense stratospheric aerosol cloud) enveloped the earth and was followed by protracted cooling lasting more than a decade from ca. A.D 536-550. Tree ring records, historical accounts, and archaeological evidence suggest that effects...

Aim Stratigraphic pollen records are used to assess historic vegetation changes that have transpired in a North American mountain meadow since the introduction of Old World livestock species in the middle 1800s.Location Monache Meadows is located on the Kern Plateau in the Sierra Nevada mountain range, California, U.S.A. It is situated along the up...

El Salvador is both the most densely populated and the most severely deforested country in the continental Americas. The convergence of these two facts leads inevitably to questions of Malthusian resource scarcity, Boserupian agricultural intensification, and the population–environment debate. Despite compelling evidence for demographic causes of l...

Ilopango volcano (El Salvador) erupted violently during the Maya Classic Period (250–900 CE) in a densely-populated and intensively-cultivated region of the southern Maya realm, causing regional abandonment of an area covering more than 20,000 km². However, neither the regional nor global impacts of the Tierra Blanca Joven (TBJ) eruption in Mesoame...

Neotropical biomass burning reconstructions synthesized from soil and sedimentary charcoal records indicate a period of reduced biomass burning sustained for several centuries after ~500 cal. yr BP. Proxy records of solar irradiance, El Niño events, temperature, and precipitation document regionally variable climate-related trends that do not accou...

Fire regimes in the lowland Neotropics are affected both by anthropogenic land use practices and natural climate variability. In Central America it is widely recognized that fire has been used as an agricultural tool for thousands of years, but the role of anthropogenic ignition as a determinant of past biomass burning frequency and magnitude has b...

A shallow coring program in Lake Nicaragua was completed in May/June 2006 by the University of Texas (UT Department of Geography and UT Institute for Geophysics). A total of 35 sediment cores with lengths ranging between 12 cm and 100 cm along with five longer cores were extracted from the lake using a gravity corer and a modified manual square rod...

It is now well established that Precolumbian farmers of Mexico and Central America were responsible for widespread environmental degradation before the arrival of Europeans. Relatively little is known, however, of the chronology, severity, and exact geographic distribution of these anthropogenic landscape impacts. This article addresses questions o...

In May of 2006 we used a chartered ferry boat to collect 520 km of seismic data, 886 km of 3.5 kHz subbottom profiler data, and 35 cores from Lake Nicaragua. The lake covers an area of 7700 km2 within the active Central American volcanic arc, forms the largest lake in Central America, ranks as the twentieth largest freshwater lake in the world, and...

An ∼8000-cal-yr stratigraphic record of vegetation change from the Sierra de Apaneca, El Salvador, documents a mid-Holocene warm phase, followed by late Holocene cooling. Pollen evidence reveals that during the mid-Holocene (∼8000–5500 cal yr B.P.) lowland tropical plant taxa were growing at elevations ∼200–250 m higher than at present, suggesting...

The historical ecology of the Ahuachapan savanna is reconstructed from a 4.83-m sediment core from Laguna Llano del Espino, Ahuachapan, western El Salvador. Stable carbon isotopes (13C), pollen, and charred grass cuticles indicate Holocene grassland dominance from at least ca. 3300 cal yr B.P. to the present. The role of people in the creation and...

Stratigraphic studies of lake sediments were carried out in the Rio Paz Valley and Sierra de Apaneca of western El Salvador. Pollen, charcoal, and organic matter content of the sediments record the Holocene environmental history of the region. Reported here are records from four lake sites, Lagunas Cuzcachapa, El Trapiche, Llano, and Verde. All sit...

Typescript. Thesis (M.A.)--San Francisco State University, 1995. Includes bibliographical references (leaves 76-83).