Geospatial modeling approach to monument construction using Michigan from A.D. 1000–1600 as a case study

Building monuments was one way that past societies reconfigured their landscapes in response to shifting social and ecological factors. Understanding the connections between those factors and monument construction is critical, especially when multiple types of monuments were constructed across the same landscape. Geospatial technologies enable past cultural activities and environmental variables to be examined together at large scales. Many geospatial modeling approaches, however, are not designed for presence-only (occurrence) data, which can be limiting given that many archaeological site records are presence only. We use maximum entropy modeling (MaxEnt), which works with presence-only data, to predict the distribution of monuments across large landscapes, and we analyze MaxEnt output to quantify the contributions of spatioenvironmental variables to predicted distributions. We apply our approach to co-occurring Late Precontact (ca. A.D. 1000–1600) monuments in Michigan: (i) mounds and (ii) earthwork enclosures. Many of these features have been destroyed by modern development, and therefore, we conducted archival research to develop our monument occurrence database. We modeled each monument type separately using the same input variables. Analyzing variable contribution to MaxEnt output, we show that mound and enclosure landscape suitability was driven by contrasting variables. Proximity to inland lakes was key to mound placement, and proximity to rivers was key to sacred enclosures. This juxtaposition suggests that mounds met local needs for resource procurement success, whereas enclosures filled broader regional needs for intergroup exchange and shared ritual. Our study shows how MaxEnt can be used to develop sophisticated models of past cultural processes, including monument building, with imperfect, limited, presence-only data

Palm phytoliths of mid-elevation Andean forests

Palms are one of the most common tropical plant groups. They are widespread across lowland tropical forests, but many are found in higher altitudes have more constrained environmental ranges. The limited range of these species makes them particularly useful in paleoecological and paleoclimate reconstructions. Palms produce phytoliths, or silica structures, which are found in their vegetative parts (e.g., wood, leaves, etc.). Recent research has shown that several palms in the lowland tropical forests produce phytoliths that are diagnostic to the sub-family or genus-level. Here we characterize Andean palm phytoliths, and determine whether many of these species can also be identified by their silica structures. All of our sampled Andean palm species produced phytoliths, and we were able to characterize several previously unclassified morphotypes. Some species contained unique phytoliths that did not occur in other species, particularly Ceroxylon alpinium, which is indicative of specific climatic conditions. The differences in the morphologies of the Andean species indicate that palm phytolith analysis is particularly useful in paleoecological reconstructions. Future phytolith analyses will allow researchers to track how these palm species with limited environmental ranges have migrated up and down the Andean slopes as a result of past climatic change. The phytolith analyses can track local-scale vegetation dynamics, whereas pollen, which is commonly used in paleoecological reconstructions, reflects regional-scale vegetation change

Comment on “Persistent effects of pre-Columbian plant domestication on Amazonian forest composition”

Levis et al. (Research Articles, 3 March 2017, p. 925) concluded that pre-Columbian tree domestication has shaped present-day Amazonian forest composition.The study, however, downplays five centuries of human influence following European arrival to the Americas.We show that the effects of post-Columbian activities in Amazonia are likely to have played a larger role than pre-Columbian ones in shaping the observed floristic patterns.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138830/1/eaan8347.full.pdf85Description of eaan8347.full.pdf : main articl

Columbus’ footprint in Hispaniola:A paleoenvironmental record of indigenous and colonial impacts on the landscape of the central Cibao Valley, northern Dominican Republic

The 1100-year sedimentary record of Laguna Biajaca reveals human-driven landscape changes in the central Cibao Valley, Dominican Republic, Hispaniola. This sediment-filled cutoff meander is located in close proximity to pre-Colonial archaeological sites and a Colonial urban hub. It provided a nutrient-rich floodable locus for agricultural activities for indigenous communities and for the first introduction of Old World crops and cattle in the Americas. Integration of paleoecological proxies revealed the formation of a clear-water body surrounded by a palm-rich forested landscape around 1100 cal yr BP. Changes in the drainage system were linked to human-driven deforestation, which also changed the composition of the vegetation and fungal communities around the site between AD 1150 and 1500 (800 and 700 cal yr BP). Pre-Colonial modifications of the landscape were primarily the result of fire-use and small-scale clearings. Crop cultivation developed between AD 1250 and 1450 (700–500 cal yr BP). Within decades after Columbus’ arrival in Hispaniola in AD 1492, the first impacts of European colonization included the abandonment of indigenous sites and the introduction of Old World domesticated animals. During the 15th and 16th centuries the area underwent intensive land-clearing that allowed for larger scale crop cultivation. An increase of aquatic vegetation points to sediment-filling around AD 1700 (250 cal yr BP). At that time, cattle breeding expanded and rapidly provoked eutrophication while, concurrently, monocultures became regionally established. This paper provides a framework of past environmental dynamics and offers an opportunity to place archaeological findings in a context of natural and anthropogenic change

Sporormiella as a tool for detecting the presence of large herbivores in the Neotropics

The reliability of using the abundance of Sporormiella spores as a proxy for the presence and abundance of megaherbivores was tested in southern Brazil. Mud-water interface samples from nine lakes, in which cattle-use was categorized as high, medium, or low, were assayed for Sporormiella representation. The sampling design allowed an analysis of both the influence of the number of animals using the shoreline and the distance of the sampling site from the nearest shoreline. Sporormiella was found to be a reliable proxy for the presence of large livestock. The concentration and abundance of spores declined from the edge of the lake toward the center, with the strongest response being in sites with high livestock use. Consistent with prior studies in temperate regions, we find that Sporormiella spores are a useful proxy to study the extinction of Pleistocene megafauna or the arrival of European livestock in Neotropical landscapes

Modern pollen rain predicts shifts in plant trait composition but not plant diversity along the Andes–Amazon elevational gradient

This is the final version. Available on open access from Wiley via the DOI in this record. Aims: Terrestrial ecosystems are changing in biodiversity, species composition and functional trait composition. To understand the underlying causes of these changes and predict the long-term resilience of the ecosystem to withstand future disturbances, we can evaluate changes in diversity and composition from fossil pollen records. Although diversity can be well estimated from pollen in temperate ecosystems, this is less clear for the hyperdiverse tropics. Moreover, it remains unknown whether functional composition of plant assemblages can be accurately predicted from pollen assemblage composition. Here, we evaluate how community-weighted mean (CWM) traits and diversity indices change along elevation. Location: Amazon–Andes elevation gradient in Peru. Methods: We used 82 modern pollen samples and 59 vegetation plots along the elevation gradient, and calculated CWM traits and diversity indices for each pollen sample and vegetation plot. We also quantified the degree to which taxa are over- or underrepresented by their pollen, by dividing the relative pollen abundance by the relative basal area abundance in the nearby vegetation survey plots (i.e. the R-rel values). Results: We found that CWM wood density increased, and CWM adult height and leaf area decreased with elevation. This change was well predicted by pollen assemblages, indicating that CWM trait–environment relationships based on pollen abundance data provide meaningful results. Diversity (richness, Shannon and Simpson) decreased with elevation for vegetation plots, but these trends could not be observed from pollen assemblages. Conclusions: Our results demonstrate that more research is needed to develop methods that lead to accurate diversity estimates from pollen data in these tropical ecosystems, but that CWM traits can be calculated from pollen data to assess spatial shifts in functional composition. This opens opportunities to calculate CWM traits from fossil pollen data sets in the tropics, with broad implications for improving our understanding and predictions of forest dynamics, functioning and resilience through time.Nederlandse Organisatie voor Wetenschappelijk Onderzoe

Warming, drought, and disturbances lead to shifts in functional composition: a millennial‐scale analysis for Amazonian and Andean sites

Tropical forests are changing in composition and productivity, probably in response to changes in climate and disturbances. The responses to these multiple environmental drivers, and the mechanisms underlying the changes, remain largely unknown. Here, we use a functional trait approach on timescales of 10,000 years to assess how climate and disturbances influence the community-mean adult height, leaf area, seed mass, and wood density for eight lowland and highland forest landscapes. To do so, we combine data of eight fossil pollen records with functional traits and proxies for climate (temperature, precipitation, and El Niño frequency) and disturbances (fire and general disturbances). We found that temperature and disturbances were the most important drivers of changes in functional composition. Increased water availability (high precipitation and low El Niño frequency) generally led to more acquisitive trait composition (large leaves and soft wood). In lowland forests, warmer climates decreased community-mean height probably because of increased water stress, whereas in highland forests warmer climates increased height probably because of upslope migration of taller species. Disturbance increased the abundance of acquisitive, disturbance-adapted taxa with small seeds for quick colonization of disturbed sites, large leaves for light capture, and soft wood to attain fast height growth. Fire had weak effects on lowland forests but led to more stress-adapted taxa that are tall with fast life cycles and small seeds that can quickly colonize burned sites. Site-specific analyses were largely in line with cross-site analyses, except for varying site-level effects of El Niño frequency and fire activity, possibly because regional patterns in El Niño are not a good predictor of local changes, and charcoal abundances do not reflect fire intensity or severity. With future global changes, tropical Amazonian and Andean forests may transition toward shorter, drought- and disturbance-adapted forests in the lowlands but taller forests in the highlands

Data from: Holocene variability of an Amazonian hyperdominant

Little is known regarding the long-term stability or instability of Amazonian plant communities. We assessed whether the most abundant species, hyperdominants, may have risen to prominence at the Pleistocene–Holocene transition, following subsequent changes in moisture regimes, or as a result of human activity later in the Holocene. The fossil pollen history of the commonest western Amazonian tree, Iriartea deltoidea (hereafter Iriartea), is investigated using fossil pollen data from 13 lakes. Iriartea is a monospecific genus with diagnostic pollen. It is also considered a ‘useful’ plant, and its abundance could have been enriched by human action. Iriartea pollen was found to have increased in abundance in the last 3000 years, but did not show a consistent relationship with human activity. The suggestion that the hyperdominants in modern Amazonian forests are a legacy of pre-Columbian people is unsupported. The abundance of Iriartea pollen is related to increasing precipitation, not human activity over the last 3000 years. This member of the hyperdominant category of Amazonian trees has only recently acquired this status. Synthesis. Our findings are consistent with the observation that communities in complex systems are ephemeral. The populations of even the most abundant species can change over a few tens of generations. The relative abundance of tree species, even in relatively stable systems such as those of Amazonian floodplains, changes on ecological not evolutionary timescales

Bamboo‐dominated forests and pre‐Columbian earthwork formations in south‐western Amazonia

Aim: To determine whether the c. 160,000 km2 patch of bamboo‐dominated forests (Guadua spp.) in Amazonia is associated with pre‐Columbian earthwork (geoglyph) formation. Location: South‐western Amazonia. Methods: We modelled the distribution of Guadua‐dominated forests and geoglyphs with Maxent, which uses occurrence points and a suite of environmental parameters. We compared the modelled distribution of Guadua with mapped distributions derived from remote sensing data, and with the modelled distribution of geoglyphs. Results: The modelled Guadua distribution closely fitted previously mapped estimates. Based on our analyses, the best predictors for the distribution of Guadua‐dominated forests are temperature seasonality and close proximity to hilly terrain. Distance to bamboo forest and precipitation of the driest quarter were the most significant predictors of geoglyph distributions. Main conclusions: This study suggests that the most parsimonious explanation for the association of geoglyphs and bamboo forests in south‐western Amazonia is that pre‐Columbian people constructed geoglyphs near the edges of the semelparous Guadua forests. After die‐off events, the large fuel load of dead vegetation would burn easily, providing a much easier mechanism of forest clearing than was possible in closed‐canopy forests. These results highlight the interplay of ancient human activity with observed biogeographical patterns, and suggest that pre‐Columbian settlement patterns may reflect the heterogeneity of forest types found within Amazonian rain forests

Holocene Iriartea percentages for thirteen lakes in Amazonia

The csv file contains the data for 13 lakes in Amazonia. Columns include site name, depth, age, Iriartea percentage, and maize percentage (when available)