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Rainfall level at which significant segmented linear regression breakpoints occur in soil prop- erties, suggesting points in climate forcing in which chemical buffering mechanisms are overcome.
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![Geologic map [17] showing the Luatele flows, ~20,000 years old...](publication/370919049/figure/fig2/AS:11431281429702312@1746713967850/Geologic-map-17-showing-the-Luatele-flows-20-000-years-old-oranges-and-the-Lata_Q320.jpg)
Soils and agriculture are inextricably linked, in the past as well as today. The Pacific islands, which often represent organized gradients of the essential soil-forming factors of substrate age and rainfall, represent excellent study systems to understand interactions between people and soils. The relationship between soil characteristics and indi...
Contexts in source publication
Context 1
... linear regression was used to explore non-linearities in the response of soil parameters to the climatic forcing of rainfall (Table 2). Due to limited sampling, this analysis was only conducted for the well-sampled soils of the main Luatele shield. ...Context 2
... accuracy of both soil age and rainfall is questionable, especially for rainfall which is modeled with only a single rainfall station with a short history on the island. The highly significant, positive linear relationship between the relatively immobile element niobium and rainfall (Table 2) suggests that the patterning of rainfall is reasonably accurate, but we cannot speak directly to the magnitude of rainfall. The exceptional drainage anecdotally observed in the Ta' ¯ u soils, coupled with the concentrated delivery of precipitation, may drive rainfall to bypass the soils through preferential flow paths, reducing the interaction and causing the soils to behave as if they were drier [64]. ...Similar publications
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Citations
... The northermost perpedicular transect sampled the Lalomaunga Alluvium (see Fig 2). We include here data on soil pH and % Base Saturation as these measures appear correlated to archaeological distributions in Sāmoa [16,88]. We compared the results of soil testing to elevation and the distribution of archaeological features, largely in dryland areas. ...
... Agriculture removes nutrients from the environment and inputs them into edible crops. While there are many elemental and other variables that characterize nutrient availability, both soil pH and % Base Saturation are reliable general indicators for crops on tropical Pacific islands [94,95], and Sāmoa specifically [88]. Soil pH and % Base Saturation (see S5 Appendix for data) vary considerably through the transects (Fig 11). ...
... p < 0.001). A sharp decline in % Base Saturation values occurs around 150-160 masl, with all samples above 155 masl exhibiting % Base Saturation values below 30%, a threshold constraining dryland agricultural patterning in Polynesia, including in Sāmoa [16,88,94]. The large mound complex is located near this elevational boundary. ...
In this research we identify the processes leading to hierarchical society in a region of Sāmoa, the often-labelled ʻbirthplace’ of the Polynesian chiefdoms. Our analyses in the Falefa Valley on ʻUpolu island combine lidar mapping and ground survey to reveal an extensive system of archaeological features: rock walls, ditches, and platforms. Excavation and radiocarbon dating underpin a feature chronology and characterize feature variation. Soil nutrient analyses and geoarchaeological coring indicate spatial differences in the agricultural potentional of the valley and human modification of the environment over time. Our results demonstrate that the construction of large rock walls, some several hundred meters long, began approximately 900–600 years ago, shortly after rapid population rise in Sāmoa. This was followed by the building of small rock walls, often enclosing rectilinear fields or platforms. Both rock wall types are concentrated in the western and northern regions of the valley and greater rock wall densities are associated with areas of higher agricultural potential. The earliest wall construction was penecontemporaneous with partial forest removal that created a more productive wetland environment in the southeastern region of the valley, an area later a focus of agricultural ditching. We propose that with population rise the variable fertility of agricultural land became a significant resource gradient, influencing the population in two ways. First, areas of more fertile agricultural land promoted territorial behaviour, including large rock walls, and led to a collective action problem. Second, niche construction in the form of human-induced environmental change created a productive wetland agricultural system that was enhanced with a reticulate ditch network, the maintenance of which also led to a collective action problem. We conclude that in the Falefa Valley, the second largest catchment in Sāmoa, collective action problems were the cause of increased social hierarchy and may underlie the origins of chiefdoms throughout Polynesia.
... Along with environmental constraints, soil fertility was a key factor in describing the extent of agricultural development and agroecological form in Polynesia, as it qualified or disqualified certain agroecological systems from efficient production (Autufuga et al., 2023;Ladefoged et al., 2009;Quintus & Lincoln, 2020;Vitousek et al., 2004Vitousek et al., , 2010Vitousek et al., , 2014. Soil fertility, or the capacity of soil to supply nutrients and water to plants, of the Examples of Agroforestry (A), which is more intensively managed, includes a higher degree of light penetration and a greater proportion of herbaceous plants, and Novel Forest (B), which is less intensively managed, consists of a closed canopy and greater proportion of trees volcanic shield surfaces in Hawai'i is largely determined as a function of weathering potential and substrate age (Autufuga et al., 2023;Chadwick et al., 2021;Vitousek et al., 2021). ...
... Along with environmental constraints, soil fertility was a key factor in describing the extent of agricultural development and agroecological form in Polynesia, as it qualified or disqualified certain agroecological systems from efficient production (Autufuga et al., 2023;Ladefoged et al., 2009;Quintus & Lincoln, 2020;Vitousek et al., 2004Vitousek et al., , 2010Vitousek et al., , 2014. Soil fertility, or the capacity of soil to supply nutrients and water to plants, of the Examples of Agroforestry (A), which is more intensively managed, includes a higher degree of light penetration and a greater proportion of herbaceous plants, and Novel Forest (B), which is less intensively managed, consists of a closed canopy and greater proportion of trees volcanic shield surfaces in Hawai'i is largely determined as a function of weathering potential and substrate age (Autufuga et al., 2023;Chadwick et al., 2021;Vitousek et al., 2021). In this case, weathering potential is largely a function of climate-driven water availability. ...
Agriculture is one of the most fundamental ways in which human societies interact with the environment. The form and function of agriculture have important socio-political implications in terms of yields, labor requirements, variability and resilience, and elite control. Hawai‘i has been used as a model system for the discussion of coupled human and natural systems, and how the uneven distribution of agricultural opportunities has manifested in the political ecology. However, consideration of agriculture has emphasized forms with physical infrastructure documented through archaeology and have not included arboricultural forms that were extensive among Pacific Islands. We leverage existing, independent data sets to build and validate spatial models of two intensities of arboriculture across the Hawaiian archipelago: Agroforestry and Novel Forest. Model validation demonstrates good accuracy that includes both expected and unexpected sources of errors. Results of the models demonstrate that arboricultural techniques accounted for ~70% of the agricultural potential by area and ~40% of the agricultural potential by yield. Unlike existing agricultural forms modeled, such as flooded wetland terrace cultivation and rainfed field production, which have strong distributional patterns based on the age of the islands, arboricultural potential is well distributed across all the islands. The extent, distribution, and characteristics of arboricultural methods provide important augmentation of the current narrative of production dynamics and distribution, and the political ecology, of pre-contact Hawai‘i.
