Prehistoric reef-building coral occurrence in north Peru

Discovery of a late Pleistocene (∼13,300 cal BP) reef-building coral species (Pocillopora damicornis) at the prehistoric Huaca Prieta settlement in Peru raises the question of its origin. Did it arrive in northern Peru from tropical Ecuador via larval dispersal in south-flowing El Niño currents or over land by human trading? The Holocene distribution of Pocillopora in the eastern Pacific extends as far south as southern Ecuador and possibly northern Peru. The marine climate during the late Pleistocene was cooler and likely limited the occurrence of corals at today’s latitudinal range. This suggests that overland or onshore transport was the most likely means of a southerly introduction, thus supporting interpretative models of early human movement along the Pacific coast of South America

Stable Isotope Biogeochemistry of Seabird Guano Fertilization: Results from Growth Chamber Studies with Maize (Zea Mays)

Stable isotope analysis is being utilized with increasing regularity to examine a wide range of issues (diet, habitat use, migration) in ecology, geology, archaeology, and related disciplines. A crucial component to these studies is a thorough understanding of the range and causes of baseline isotopic variation, which is relatively poorly understood for nitrogen (δ(15)N). Animal excrement is known to impact plant δ(15)N values, but the effects of seabird guano have not been systematically studied from an agricultural or horticultural standpoint.This paper presents isotopic (δ(13)C and δ(15)N) and vital data for maize (Zea mays) fertilized with Peruvian seabird guano under controlled conditions. The level of (15)N enrichment in fertilized plants is very large, with δ(15)N values ranging between 25.5 and 44.7‰ depending on the tissue and amount of fertilizer applied; comparatively, control plant δ(15)N values ranged between -0.3 and 5.7‰. Intraplant and temporal variability in δ(15)N values were large, particularly for the guano-fertilized plants, which can be attributed to changes in the availability of guano-derived N over time, and the reliance of stored vs. absorbed N. Plant δ(13)C values were not significantly impacted by guano fertilization. High concentrations of seabird guano inhibited maize germination and maize growth. Moreover, high levels of seabird guano greatly impacted the N metabolism of the plants, resulting in significantly higher tissue N content, particularly in the stalk.The results presented in this study demonstrate the very large impact of seabird guano on maize δ(15)N values. The use of seabird guano as a fertilizer can thus be traced using stable isotope analysis in food chemistry applications (certification of organic inputs). Furthermore, the fertilization of maize with seabird guano creates an isotopic signature very similar to a high-trophic level marine resource, which must be considered when interpreting isotopic data from archaeological material

Amazonian Dark Earths in Western Amazonia?

Western Amazonia is a large region that includes a global biodiversity hotspot (the Yasuni National Park) and which still retains large tracts of intact native rainforest. Along the Napo River (Fig. 1), which originates in the Ecuadorian eastern lowlands and discharges into the Peruvian reaches of the Amazon River, current human settlement is uneven and highly dispersed. In Ecuador, towns are associated with the encroachment of oil extraction activities and the expansion of the agricultural frontier; small villages are found along an expanding road network and also dot the banks of the main rivers; and small groups of nomadic peoples, some in voluntary isolation from our industrialised society, inhabit the rugged interfluvial terrain beyond the main rivers. In Peru, small villages dot the middle reaches of the Napo River and its main tributaries, and there are also reports of indigenous groups in voluntary isolation. Larger settlements become more prevalent in the lower Napo, closer to the Amazon River and within reach of the road network leading to the Peruvian city of Iquitos

Structuring properties of irrigation systems: Understanding relations between humans and hydraulics through modeling

Irrigation systems were clearly important in ancient times in supplying crops with water. This requires physical distribution facilities and socio-political arrangements to coordinate between actors. Resulting systems are highly diverse, and are being studied extensively within archeology and history. Whether initiated by a central authority or emerging from small-scale initiatives, irrigation systems are shaped through activities of individuals, households, and small groups into patterns and landscapes. This article discusses how hydraulic modeling techniques are powerful methodologies to study such irrigation development. Modeling daily interactions by agents and water fluxes will build better understanding of irrigation systems as anthropogenic landscapes. Three case studies will be used to illustrate this argument. A current irrigation system in Arequipa, Peru, shows that one can relate irrigation infrastructure and social action. A second case from Peru on a pre-Colombian irrigation system suggests that one can link irrigation system, water flows, and settlement. In the third case in the Jordan Valley, this possible link between irrigation and settlement is further studied.Water ManagementCivil Engineering and Geoscience