michael bird

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Armando Marques-Guedes

UNL - New University of Lisbon

Inmaculada Carrasco

Universidad Pablo de Olavide

Michael Neale

Virginia Commonwealth University

Marcia L Hattori

CSIC (Consejo Superior de Investigaciones Científicas-Spanish National Research Council)

Laura Muñoz-Encinar

CSIC (Consejo Superior de Investigaciones Científicas-Spanish National Research Council)

Viacheslav Kuleshov

Stockholm University

Diego Villar

National Scientific and Technical Research Council

JUAN MANUEL MONTERROSO MONTERO

University of Santiago de Compostela

Gilberto Perez Roldan

Universidad Autónoma de San Luis Potosí

Matilde Arnay

Universidad de La Laguna

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Papers by michael bird

A 33,000-year paleohydrological record from Sanamere Lagoon, north-eastern tropical savannas of Australia

Quaternary Research, Dec 29, 2022

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A global carbon and nitrogen isotope perspective on modern and ancient human diet

Proceedings of the National Academy of Sciences, 2021

Significance The carbon and nitrogen isotope composition of human tissues can be used to infer di... more Significance The carbon and nitrogen isotope composition of human tissues can be used to infer dietary information. We transformed isotope compositions of 13,666 modern and ancient analyses to make them comparable on a common scale. This reveals that the isotope dietary breadth of modern humans is highly compressed when compared to populations predating the development in 1910 of modern industrial fertilizer by the Haber–Bosch method. However, modern humans that still use “traditional” subsistence strategies retain remarkably similar isotope dietary breadth to all pre-Haber–Bosch human populations. Increased reliance on industrial agriculture and pastoralism is resulting in a cascade of “rewiring” to remaining food webs globally that can reduce the resilience of global ecosystems in the face of accelerating environmental change.

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Landscape rules predict optimal superhighways for the first peopling of Sahul

Nature Human Behaviour, 2021

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A new Holocene sea-level record for Singapore

The Holocene, 2021

Relative sea-level (RSL) records from far-field regions distal from ice sheets remain poorly unde... more Relative sea-level (RSL) records from far-field regions distal from ice sheets remain poorly understood, particularly in the early Holocene. Here, we extended the Holocene RSL data from Singapore by producing early Holocene sea-level index points (SLIPs) and limiting dates from a new ~40 m sediment core. We merged new and published RSL data to construct a standardized Singapore RSL database consisting of 88 SLIPs and limiting data. In the early Holocene, RSL rose rapidly from −21.0 to −0.7 m from ~9500 to 7000 cal. yrs. BP. Thereafter, the rate of RSL rise decelerated, reaching a mid-Holocene highstand of 4.0 ± 4.5 m at 5100 cal. yrs. BP, before falling to its present level. There is no evidence of any inflections in RSL when the full uncertainty of SLIPs is considered. When combined with other standardized data from the Malay-Thai Peninsula, our results also show substantial misfits between regional RSL reconstructions and glacial isostatic adjustment (GIA) model predictions in the...

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Net landscape carbon balance of a tropical savanna: Relative importance of fire and aquatic export in offsetting terrestrial production

Global Change Biology, 2020

The magnitude of the terrestrial carbon (C) sink may be overestimated globally due to the difficu... more The magnitude of the terrestrial carbon (C) sink may be overestimated globally due to the difficulty of accounting for all C losses across heterogeneous landscapes. More complete assessments of net landscape C balances (NLCB) are needed that integrate both emissions by fire and transfer to aquatic systems, two key loss pathways of terrestrial C. These pathways can be particularly significant in the wet–dry tropics, where fire plays a fundamental part in ecosystems and where intense rainfall and seasonal flooding can result in considerable aquatic C export (ΣFaq). Here, we determined the NLCB of a lowland catchment (~140 km2) in tropical Australia over 2 years by evaluating net terrestrial productivity (NEP), fire‐related C emissions and ΣFaq (comprising both downstream transport and gaseous evasion) for the two main landscape components, that is, savanna woodland and seasonal wetlands. We found that the catchment was a large C sink (NLCB 334 Mg C km−2 year−1), and that savanna and w...

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Biochar-based fertilizer: Supercharging root membrane potential and biomass yield of rice

Science of The Total Environment, 2020

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Radiocarbon Dating of the Human Occupation of Australia Prior to 40 ka BP—Successes and Pitfalls

Radiocarbon, 2001

Charcoal samples from ancient human occupation sites in Australia have been subjected to a rigoro... more Charcoal samples from ancient human occupation sites in Australia have been subjected to a rigorous pretreatment and stepped combustion regime in order to explore the possibility that these sites may be older than previous radiocarbon dating had suggested. In one case, the Devil's Lair site in southwest Australia, the methodology has clearly removed vestiges of contamination by more modern carbon and has led to a revised radiocarbon chronology that provides evidence for human occupation of southwest Australia by at least 44 ka BP and probably by 46–47 ka BP. In contrast, charcoal from the Nauwalabila site has been so severely altered that insufficient of the original carbon remains for reliable 14C dating. Finally, where the charcoal is well preserved, such as at the Carpenter's Gap site, the new results provide reassurance that earlier 14C results of ∼40 ka BP are indeed true ages and are not simply at the limit of the 14C technique.

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What caused extinction of the Pleistocene megafauna of Sahul?

Proceedings of the Royal Society B: Biological Sciences, 2016

During the Pleistocene, Australia and New Guinea supported a rich assemblage of large vertebrates... more During the Pleistocene, Australia and New Guinea supported a rich assemblage of large vertebrates. Why these animals disappeared has been debated for more than a century and remains controversial. Previous synthetic reviews of this problem have typically focused heavily on particular types of evidence, such as the dating of extinction and human arrival, and have frequently ignored uncertainties and biases that can lead to misinterpretation of this evidence. Here, we review diverse evidence bearing on this issue and conclude that, although many knowledge gaps remain, multiple independent lines of evidence point to direct human impact as the most likely cause of extinction.

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Climate change not to blame for late Quaternary megafauna extinctions in Australia

Nature communications, Jan 29, 2016

Late Quaternary megafauna extinctions impoverished mammalian diversity worldwide. The causes of t... more Late Quaternary megafauna extinctions impoverished mammalian diversity worldwide. The causes of these extinctions in Australia are most controversial but essential to resolve, because this continent-wide event presaged similar losses that occurred thousands of years later on other continents. Here we apply a rigorous metadata analysis and new ensemble-hindcasting approach to 659 Australian megafauna fossil ages. When coupled with analysis of several high-resolution climate records, we show that megafaunal extinctions were broadly synchronous among genera and independent of climate aridity and variability in Australia over the last 120,000 years. Our results reject climate change as the primary driver of megafauna extinctions in the world's most controversial context, and instead estimate that the megafauna disappeared Australia-wide ∼13,500 years after human arrival, with shorter periods of coexistence in some regions. This is the first comprehensive approach to incorporate unce...

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Bat guano: record of climate change

AccessScience

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Neolithic societies c. 4000-2000 years ago: Austronesian farmers?

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Structural, physiognomic and aboveground biomass variation in savanna-forest transition zones on three continents. How different are co-occurring savanna and forest formations?

Biogeosciences Discussions, 2014

Through interpretations of remote sensing data and/or theoretical propositions, the idea that for... more Through interpretations of remote sensing data and/or theoretical propositions, the idea that forest and savanna represent "alternative stable states" is gaining increasing acceptance. Filling an observational gap, we present detailed stratified floristic and structural analyses for forest and savanna stands mostly located within zones of transition (where both vegetation types occur in close proximity) in Africa, South America and Australia. Woody plant leaf area index variation was related in a similar way to tree canopy cover for both savanna and forest with substantial overlap between the two vegetation types. As total woody plant canopy cover increased, so did the contribution of middle and lower strata of woody vegetation to this total. Herbaceous layer cover also declined as woody cover increased. This pattern of understorey grasses and herbs being progressively replaced by shrubs as canopy closure occurs was found for both savanna and forests and on all continents....

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Foliar trait contrasts between African forest and savanna trees: genetic versus environmental effects

Functional Plant Biology, 2015

Variations in leaf mass per unit area (Ma) and foliar concentrations of N, P, C, K, Mg and Ca wer... more Variations in leaf mass per unit area (Ma) and foliar concentrations of N, P, C, K, Mg and Ca were determined for 365 trees growing in 23 plots along a West African precipitation gradient ranging from 0.29 to 1.62 m a–1. Contrary to previous studies, no marked increase in Ma with declining precipitation was observed, but savanna tree foliar [N] tended to be higher at the drier sites (mass basis). Generally, Ma was slightly higher and [N] slightly lower for forest vs savanna trees with most of this difference attributable to differences in soil chemistry. No systematic variations in [P], [Mg] and [Ca] with precipitation or between trees of forest vs savanna stands were observed. We did, however, find a marked increase in foliar [K] of savanna trees as precipitation declined, with savanna trees also having a significantly lower [K] than those of nearby forest. These differences were not related to differences in soil nutrient status and were accompanied by systematic changes in [C] of...

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Carbon isotopic signatures of soil organic matter correlate with leaf area index across woody biomes

Journal of Ecology, 2014

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Contributions of woody and herbaceous vegetation to tropical savanna ecosystem productivity: a quasi-global estimate

Tree Physiology, 2008

To estimate the relative contributions of woody and herbaceous vegetation to savanna productivity... more To estimate the relative contributions of woody and herbaceous vegetation to savanna productivity, we measured the 13 C/ 12 C isotopic ratios of leaves from trees, shrubs, grasses and the surface soil carbon pool for 22 savannas in Australia, Brazil and Ghana covering the full savanna spectrum ranging from almost pure grassland to closed woodlands on all three continents. All trees and shrubs sampled were of the C 3 pathway and all grasses of the C 4 pathway with the exception of Echinolaena inflexa (Poir.) Chase, a common C 3 grass of the Brazilian cerrado. By comparing the carbon isotopic compositions of the plant and carbon pools, a simple model relating soil δ 13 C to the relative abundances of trees + shrubs (woody plants) and grasses was developed. The model suggests that the relative proportions of a savanna ecosystem's total foliar projected cover attributable to grasses versus woody plants is a simple and reliable index of the relative contributions of grasses and woody plants to savanna net productivity. Model calibrations against woody tree canopy cover made it possible to estimate the proportion of savanna productivity in the major regions of the world attributable to trees + shrubs and grasses from ground-based observational maps of savanna woodiness. Overall, it was estimated that 59% of the net primary productivity (N p ) of tropical savannas is attributable to C 4 grasses, but that this proportion varies significantly within and between regions. The C 4 grasses make their greatest relative contribution to savanna N p in the Neotropics, whereas in African regions, a greater proportion of savanna N p is attributable to woody plants. The relative contribution of C 4 grasses in Australian savannas is intermediate between those in the Neotropics and Af-rica. These differences can be broadly ascribed to large scale differences in soil fertility and rainfall.

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Environmental controls on the stable carbon isotopic composition of soil organic carbon: implications for modelling the distribution of C3 and C4 plants, Australia

Tellus B: Chemical and Physical Meteorology, 2008

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Soil carbon inventories and carbon-13 on a latitude transect in Siberia

Tellus B: Chemical and Physical Meteorology, 2002

We present soil organic carbon (SOC) inventories and carbon isotope compositions from over 900 sa... more We present soil organic carbon (SOC) inventories and carbon isotope compositions from over 900 samples collected in areas of minimally disturbed mature vegetation on freely drained soils (excluding peatlands) on a 1000 km transect along the Yennisey River, central Siberia. Carbon inventories over 0-30 cm depth range widely from 1.71 to 7.05 kg m -2 . While an effect of changing climate or vegetation along the transect cannot be ruled out, the observed differences in SOC inventories are largely the result of variations in mineral soil texture, with inventories in fine-textured soils being approximately double those in coarse-textured soils. The δ 13 C values of SOC in the 0-5 cm interval ranged from -26.3 to -28.0‰, with δ 13 C values for the 5-30 cm interval being 0.9 ± 0.8‰ (1σ ) enriched in 13 C relative to the 0-5 cm samples. The average δ 13 C value for the 0-5 cm interval for all samples was -27.1 ± 0.6‰ (1σ ) and for the full 0-30 cm interval the average was -26.5 ± 0.5‰ (1σ ). In general, δ 13 C values were higher in coarse-textured soils and lower in fine-textured soils. The results of detailed sampling of soils in Pinus sylvestris forest growing on sand near the Zotino flux tower suggest an SOC inventory in these soils of 2.22 ± 0.35 kg m -2 over 30 cm and an average δ 13 C value of -26.3 ± 0.2‰ over the 0-5 cm depth interval and -25.9 ± 0.3‰ over 0-30 cm. Recent burning had no effect on SOC inventories, but clearing has led to an average 25% decrease on SOC inventories from 0-30 cm over 12 yr. Neither burning nor clearing had a discernible effect on the δ 13 C value of SOC.

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