Disturbing Developments: An Archaeobotanical Perspective on Pinyon-Juniper Woodland Fire Ecology, Economic Resource Production, and Ecosystem History

Abstract

It has long been thought that the only means by which the American Southwest's extensive pinyon-juniper woodlands, with their inherently low primary productivity, could have supported indigenous populations during prehispanic times was with the transformative consequences associated with the widespread cultivation of low-moisture-intolerant domesticated plants, principally maize (Zea mays L.). In this paper we present an alternative to this orthodox view which posits that anthropogenic fire was a vegetation-community management technology that was used to create disturbance patches and to propagate abundant, edible seed-rich ruderals in them. This perspective allows us, as well, to introduce and illustrate the interpretive possibilities of a conceptual scheme that focuses on three resource production types—cultivated wild plants, gathered wild plants, and domesticated plants—with multi-contextual macrobotanical data from a partially burned and rapidly abandoned multi-room settlement (occupied between AD 1070–1080) located south of the Grand Canyon in northern Arizona. By integrating these data with previous archaeobotanical, pollen, and sedimentary micro-charcoal studies, we propose that the systematic cultivation of wild plants in pyrogenic resource patches was a sustainable practice that enhanced food-supply security by insulating populations from the effects of short-term environmental variability and long-term climate change that challenge maize farmers. Importantly, these investigations indicate that low-intensity burning did not involve widespread deforestation, as some models of Holocene climate change suggest, and that prehistoric depopulation and modern fire suppression have altered fundamentally the composition and economic potential of contemporary pinyon-juniper ecosystems.

Early- and middle-Holocene wood exploitation in the Fayum basin, Egypt

“…The cereals identified in the K pits, emmer wheat ( Triticum dicoccum ) and six-row barley ( Hordeum vulgare ), are dry adapted and capable of being grown with limited rainfall, although it is unclear whether precipitation sufficient for rainfall agriculture would have been present in the Fayum even during the early and middle Holocene (Hassan, 1986: 494; Phillipps et al, 2012; Wendrich et al, 2017). As a result, it has been suggested that agriculture in the Fayum took place either at the lakeshore following seasonal recession of the Nile-flood-fed high lake stand (Caton-Thompson and Gardner, 1934; Wenke and Casini, 1989: 147–148; Wenke et al, 1988) or in wadis that channeled winter rains to strategically planted areas (Holdaway et al, 2016: 6), analogous to desert production strategies for maize and other crops in the American Southwest (Fish and Fish, 1992; Fish et al, 1985; Sullivan, 2000; Sullivan et al, 2015). Wood charcoal can distinguish whether basin- or lakeshore thickets were cleared for agriculture, suggesting an agricultural strategy in seasonally inundated soils or whether wood from wadis was cleared and brought to settled locations for fuel, indicating a rainfed agricultural strategy.…”

Ecosystem impacts by the Ancestral Puebloans of Chaco Canyon, New Mexico, USA

“…Extensive natural forest fires are infrequent in this area today, and probably the same was true in the past, because juniper and pinyon plants are widely spaced [ 54 ] and the fuel to support a spreading crown fire is generally not present [ 55 ]. Furthermore, there is evidence that the ancient cultures of the American Southwest undertook periodic low-intensity burning which may have protected the forests from crown fires [ 56 ] as well as improve forage for game [ 34 ]. Lightning strikes do occur, but these are generally limited to the struck tree [ 55 ].…”

Theoretical and Socioecological Consequences of Fire Foodways

“…The data do not include counts of indirect indicators of plant use, such as cone scales, seed coats, nutshell, bark, needles, stems, leaves, wood, or cupules. This method was selected because it tightly constrains frequencies of edible plant parts—seeds or nuts—that in all likelihood were the objects of wild plant cultivation, wild plant gathering, or domesticated plant cultivation (Sullivan et al 2015:44). Ubiquity values are given in parentheses.…”

“…Today, the Upper Basin is blanketed by a dense pinyon-juniper woodland (Vankat 2013) that becomes intermixed with ponderosa pine on its western edge but grades to grassland farther south (Darling 1967). Like so many areas in the upland Southwest occupied between AD 875 and 1200 (Euler 1988), the Upper Basin is thickly stocked with abandoned one- to two-room structures and other features, such as rock alignments and terraces (Sullivan et al 2015), which conventionally have been interpreted as landscape signatures of maize production (e.g., Effland et al 1981; Stewart and Donnelly 1943). However, these appearances are deceiving when we examine the area's modern and ancient environmental characteristics and its archaeo-economic record and evaluate the extent to which they align with the attributes of maize-based foodways.…”

“…3.The results of grain size, soil phosphorous (P), charcoal concentration, and carbon isotope ratio analyses of axial alluvial fan deposits (McNamee 2003; Roos et al 2010) and from botanical and pollen analyses of samples recovered from a wide variety of archaeological contexts (Sullivan and Ruter 2006; Sullivan et al 2015) support the argument that the prehistoric fire regime in the Upper Basin between circa AD 875 and 1200 consisted of frequent, low-intensity, surface, understory anthropogenic fires (West 1984:1310). Mixed-severity or high-severity (lethal) fires (where 20% to more than 70% of the overstory is killed by fire [Williams and Baker 2013:301]) were rare until the area was abandoned (i.e., perennial occupation ceased ca.…”