On the scaling and standardization of charcoal data in paleofire reconstructions

Understanding the biogeography of past and present fire events is particularly important in tropical forest ecosystems, where fire rarely occurs in the absence of human ignition. Open science databases have facilitated comprehensive and synthetic analyses of past fire activity, but charcoal datasets must be standardized (scaled) because of variations in measurement strategy, sediment type, and catchment size.  Here, we: i) assess how commonly used metrics of charcoal scaling perform on datasets from tropical forests; ii) introduce a new method called proportional relative scaling, which down-weights rare and infrequent fire; and iii) compare the approaches using charcoal data from four lakes in the Peruvian Amazon. We found that Z-score transformation and relative scaling (existing methods) distorted the structure of the charcoal peaks within the record, inflating the variation in small-scale peaks and minimizing the effect of large peaks. Proportional relative scaling maintained the structure of the original non-scaled data and contained zero values for the absence of fire. Proportional relative scaling provides an alternative scaling approach when the absence of fire is central to the aims of the research or when charcoal is infrequent and occurs in low abundances

On the scaling and standardization of charcoal data in paleofire reconstructions

Understanding the biogeography of past and present fire events is particularly important in tropical forest ecosystems, where fire rarely occurs in the absence of human ignition. Open science databases have facilitated comprehensive and synthetic analyses of past fire activity, but charcoal datasets must be standardized (scaled) because of variations in measurement strategy, sediment type, and catchment size.  Here, we: i) assess how commonly used metrics of charcoal scaling perform on datasets from tropical forests; ii) introduce a new method called proportional relative scaling, which down-weights rare and infrequent fire; and iii) compare the approaches using charcoal data from four lakes in the Peruvian Amazon. We found that Z-score transformation and relative scaling (existing methods) distorted the structure of the charcoal peaks within the record, inflating the variation in small-scale peaks and minimizing the effect of large peaks. Proportional relative scaling maintained the structure of the original non-scaled data and contained zero values for the absence of fire. Proportional relative scaling provides an alternative scaling approach when the absence of fire is central to the aims of the research or when charcoal is infrequent and occurs in low abundances

Data from: Mauritius on fire: tracking historical human impacts on biodiversity loss

Fire was rare on Mauritius prior to human arrival (AD 1598); subsequently three phases of elevated fire activity occurred: c. 1630-1747, 1787-1833, and 1950-modern. Elevated fire frequency coincided with periods of high human impact evidenced from the historical record, and is linked to the extinction of island endemics

Quantifying local-scale changes in Amazonian forest cover using phytoliths

The ecosystem services and immense biodiversity of Amazon rainforests are threatened by deforestation and forest degradation. A key goal of modern archaeology and paleoecology in Amazonia is to establish the extent and duration of past forest disturbance by humans. Fossil phytoliths are an established proxy to identify the duration of disturbance in lake sedimentary and soil archives. What is not known, is the spatial scale of such forest disturbances when identified by phytoliths. Here we use phytolith assemblages to detect local-scale forest openings, provide an estimate of extent, and consider long-term forest recovery. We use modern phytolith assemblages of 50 Amazonian lakes to i) assess how phytolith assemblages vary across forest cover at 5 spatial scales (100 m, 200 m, 500 m, 1 km, 2 km), ii) model which phytolith morphotypes can accurately predict forest cover at 5 spatial scales, and iii) compare phytoliths with pollen to quantify their relative ability to detect forest cover changes. DCA results show phytolith assemblages could be used to differentiate low, intermediate, and high forest cover values, but not to distinguish between biogeographical gradients across Amazonia. Beta regression models show Poaceae phytoliths can accurately predict forest cover within 200 m of Amazonian lakes. This modern calibration dataset can be used to make quantitative reconstructions of forest cover changes in Amazonia, to generate novel insights into long-term forest recovery. Combining phytoliths and pollen provides a unique opportunity to make qualitative and quantitative reconstructions of past vegetation changes, to better understand how human activities, environmental and climatic changes have shaped modern Amazonian forests

Gosling_Mauritius_data

1)SITE INFORMATION 1.1)Geography 1.2)Study site 2) CORE INFORMATION 2.1)Description 2.2)Radiocarbon dates 2.3)Chronology 2.4)Charcoal data 2.4.1) Macroscopic charcoal, size range 75-160 µm, particle counts 2.4.2) Macroscopic charcoal, size range >160 µm, particle counts 2.4.3) Macroscopic charcoal, size range >160 µm, area 2.4.4) Macroscopic charcoal, size range >160 µm, volume 2.5) Loss-on-ignition data 3)REFERENCE

Ecological responses to land use change in the face of European colonization of Haytí island

Caribbean island ecosystems underwent significant landscape transformations in the centuries after Columbus landed in the archipelago in AD1492, but there is no agreement as to the degree and extent of pre-Columbian human impacts and the long-term trends of ecosystem disturbance and recovery. Here, we present an integrative analysis of three palaeoenvironmental records in the northern Caribbean island of Haytí (currently Dominican Republic and Haiti), to assess regional landscape transformation and human impacts in pre- and post-Columbian times. We examine biotic and abiotic indicators of landscape and ecosystem change along the Columbus’ Route, the first European extractive transport route built in the Americas. Our data show that indigenous populations transformed the landscape between 1000 and 450 cal yr BP through slash-and-burn agricultural practices. Depopulation and forced population displacement through relocation of indigenous people into Spanish mining areas triggered the recovery and expansion of forests in the valley, coastal plain and mountains. In contrast, mangroves near the first permanent European colonial outpost in the Americas (La Isabela) underwent no significant impacts related to climatic, indigenous, and early colonial pressures. All ecosystems studied have suffered degradation through deforestation during the last 200 years leading to the present fragmented landscapes. In islands with long histories of human settlement such as Haytí, reconstructing temporal and spatial aspects of human transformations and impacts on the environment is crucial to improving our understanding of the drivers and mechanisms of ecosystem degradation and recovery

Human occupation and ecosystem change on Upolu (Samoa) during the Holocene

Aim: To track the peopling of the South Pacific and assess their impact on terrestrialand aquatic ecosystemsLocation: Upolu, SamoaMethods: A sedimentary record covering the last c. 10,500 years was recovered from the volcanic crater that contains Lake Lanoto’o near the centre of Upolu Island. Information on past ecological change was obtained from microscopic and macroscopic remains extracted from the sediments: charcoal (fire history), pollen/spores and plant remains (vegetation history), and lake status (algae/cyanobacteria). Information on the depositional environment and climate was obtained from geochemical and sedimentary analysis: loss-on-ignition (sediment composition), cryptotephras (volcanic eruptions), and precipitation regime (Ti/inc). The environmental history developed was compared with the archaeological record from the region.Results: Charcoal material was found in the Lake Lanoto’o sediments at higher abundances and more frequently in samples from the period after the first archaeological evidence of people on Upolu (c. 2900-2700 years ago). No abrupt shift is recognised in the vegetation or aquatic ecosystem assemblages coincident with the arrival of people on the island.Main conclusions: Macrocharcoal is demonstrated to be an effective proxy for detecting human occupation of Upolu around 2800 years ago. The immediate impact of these settlers on the vegetation seems to have been minimal, however, a subsequent opening up of the landscape is suggested through the gradual increase in ferns. The absence of any significant change in the aquatic community associated with, or after, the arrival of people on the islands suggests that humans rarely visited the lake. We suggest that on Upolu a simple model of decreasing human impact away from coastal areas is applicable

Ecological responses to land use change in the face of European colonization of <i>Haytí</i> island

Caribbean island ecosystems underwent significant landscape transformations in the centuries after Columbus landed in the archipelago in AD1492, but there is no agreement as to the degree and extent of pre-Columbian human impacts and the long-term trends of ecosystem disturbance and recovery. Here, we present an integrative analysis of three palaeoenvironmental records in the northern Caribbean island of Haytí (currently Dominican Republic and Haiti), to assess regional landscape transformation and human impacts in pre- and post-Columbian times. We examine biotic and abiotic indicators of landscape and ecosystem change along the Columbus’ Route, the first European extractive transport route built in the Americas. Our data show that indigenous populations transformed the landscape between 1000 and 450 cal yr BP through slash-and-burn agricultural practices. Depopulation and forced population displacement through relocation of indigenous people into Spanish mining areas triggered the recovery and expansion of forests in the valley, coastal plain and mountains. In contrast, mangroves near the first permanent European colonial outpost in the Americas (La Isabela) underwent no significant impacts related to climatic, indigenous, and early colonial pressures. All ecosystems studied have suffered degradation through deforestation during the last 200 years leading to the present fragmented landscapes. In islands with long histories of human settlement such as Haytí, reconstructing temporal and spatial aspects of human transformations and impacts on the environment is crucial to improving our understanding of the drivers and mechanisms of ecosystem degradation and recovery

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

The data were used to evaluate long-term (~10,000 y) changes in the functional composition of tree communities in Amazonian and Andean forests, and how these changes are explained by climate change, droughts, and disturbances. The dataset contains community-weighted means (CWM) over time of four traits: wood density, seed mass, leaf area and adult tree height. Traits were weighted by taxon abundances derived from fossil pollen records. The dataset also contains data on climate (d18O), temperature, droughts (El Niño frequency), fire disturbance (from charcoal abundance), and other general disturbances (from Cecropia abundance)