Robert McCulloch

Hunter-gatherers, biogeographic barriers and the development of human settlement in Tierra del Fuego

Tierra del Fuego represents the southernmost limit of human settlement in the Americas. While people may have started to arrive there around 10 500 BP, when it was still connected to the mainland, the main wave of occupation occurred 5000 years later, by which time it had become an island. The co-existence in the area of maritime hunter-gatherers (in canoes) with previous terrestrial occupants pre-echoes the culturally distinctive groups encountered by the first European visitors in the sixteenth century. The study also provides a striking example of interaction across challenging natural barriers.

High Latitude Dust in the Earth System

Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (≥50°N and ≥40°S) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 km2 and contribute at least 80–100 Tg yr−1 of dust to the Earth system (~5% of the global dust budget); both are projected to increase under future climate change scenarios.

IMPACT OF NEOTECTONICS ON THE RECORD OF GLACIER AND SEA LEVEL FLUCTUATIONS, STRAIT OF MAGELLAN, SOUTHERN CHILE

ABSTRACT. This paper presents evidence for a neotectonic influence on Late Pleistocene/Holocene records of environmental change in the southern Strait of Magellan. We concentrate on one site, Puerto del Hambre, a key location for reconstructing palaeoenvironmental change in southernmost South America. We report geomorphological, structural geological, seismic and topographic data that all show the site has been affected by postglacial faulting. There is also indirect evidence from the site stratigraphy that the site has been displaced. Also, recent faulting explains some of the puzzles associated with interpretation of the palaeoenvironmental record at Puerto del Hambre. The implication of this work is that neotectonic faulting had a pervasive influence in the southern part of the Strait of Magellan and southernmost Tierra del Fuego, and thus affects glacial or sea level reconstructions in the area.

Successional patterns along soil development gradients formed by glacier retreat in the Maritime Antarctic, King George Island

BackgroundMaritime Antarctica is severely affected by climate change and accelerating glacier retreat forming temporal gradients of soil development. Successional patterns of soil development and plant succession in the region are largely unknown, as are the feedback mechanisms between both processes. Here we identify three temporal gradients representing horizontal and vertical glacier retreat, as well as formation of raised beaches due to isostatic uplift, and describe soil formation and plant succession along them. Our hypotheses are (i) plants in Antarctica are able to modulate the two base parameters in soil development, organic C content and pH, along the temporal gradients, leading to an increase in organic carbon and soil acidity at relatively short time scales, (ii) the soil development induces succession along these gradients, and (iii) with increasing soil development, bryophytes and Deschampsia antarctica develop mycorrhiza in maritime Antarctica in order to foster interaction with soil.ResultsAll temporal gradients showed soil development leading to differentiation of soil horizons, carbon accumulation and increasing pH with age. Photoautptroph succession occurred rapidly after glacier retreat, but occurrences of mosses and lichens interacting with soils by rhizoids or rhizines were only observed in the later stages. The community of ground dwelling mosses and lichens is the climax community of soil succession, as the Antarctic hairgrass D. antarctica was restricted to ornithic soils. Neither D. antarctica nor mosses at the best developed soils showed any sign of mycorrhization.ConclusionTemporal gradients formed by glacier retreat can be identified in maritime Antarctic, where soil development and plant succession of a remarkable pace can be observed, although pseudo-succession occurs by fertilization gradients caused by bird feces. Thus, the majority of ice-free surface in Antarctica is colonized by plant communities which interact with soil by litter input rather than by direct transfer of photoassimilates to soil.

A Holocene record of environmental change from Río Zeballos, Central Patagonia

There are few continuous palaeoenvironmental records spanning the Holocene in Andean Southern Patagonia near the Northern Patagonian Ice Field (~47°S). Insights into the environmental context for human–landscape interactions have relied mostly on data extrapolated from distant extra-Andean locations that suggest limited environmental change during the Holocene. La Frontera (46°52′S), a high altitude site on the southern beech forest–steppe ecotone boundary in the Río Zeballos valley, provides lithostratigraphical and palaeoecological evidence, constrained by 14C dating and tephrochronology, for dynamic environmental change during the last ~8000 years. An initial amelioration in environmental conditions after c. 8210 cal. BP was followed by a reversal to colder conditions between c. 7420 and 6480 cal. BP, coincident with initial human occupation within the Paso Roballos and Lago Pueyrredón basin. Between c. 6480 and 3700 cal. BP, the woodland/steppe composition continued to fluctuate in response to climatic change. After c. 3700 cal. BP, a gradual shift to more stable and temperate conditions, punctuated by increased fire activity, is contemporary with the later phases of human occupation extending up into the Paso Roballos–Río Zeballos corridor.

Palaeoenvironmental evidence for woodland conservation in Northern Iceland from settlement to the twentieth century

ABSTRACT Narratives of Norse arrival in Iceland highlight the onset of land degradation and loss of woodland cover as major and long-term environmental consequences of settlement. However, deliberate and sustained land resource management in Iceland is increasingly being recognised, and in this paper we assess whether woodland areas were deliberately managed as fuel resources. Our study location is the high status farm site at Hofstaðir in northern Iceland. A palynological record was obtained from a small basin located just inside the farm boundary wall and the geoarchaeological record of fuel use obtained from waste midden deposits associated with the farm. Both environmental records are temporally constrained by tephrochronology and archaeological records. When viewed within the broader landscape setting, our findings suggest that there was near continuous use of birch wood from early settlement to the present day, that it was actively conserved throughout the occupation of the site and that there were clear distinctions in fuel resource utilisation for domestic and more industrial purposes. Our analyses open discussion on the role of local woodlands and their management in the Norse farm economy.