John Dodson

Australian Nuclear Science and Technology Organization, Environment, Faculty Member

Followers

Following

Co-authors

Public Views

Environmental scientist who works in Sydney (Australia) and Xi'an (China). Main research on human impacts on environmental systems of Australia, Pacific Islands and China.
Address: Kirrawee, New South Wales, Australia

less

University College London

VIT University

Interests

Uploads

Papers by John Dodson

Weihe Basin Drilling Project (WBDP): Cenozoic tectonic-monsoon interactions

Download

Quantitative Holocene climatic reconstructions for the lower Yangtze region of China

Climate Dynamics, 2017

Quantitative proxy-based and high-resolution palaeoclimatic datasets are scarce for the lower rea... more Quantitative proxy-based and high-resolution palaeoclimatic datasets are scarce for the lower reaches of the Yangtze River (LYR) basin. This region is in a transitional vegetation zone which is climatologically sensitive; and as a birthplace for prehistorical civilization in China, it is important to understand how palaeoclimatic dynamics played a role in affecting cultural development in the region. We present a pollen-based and regionally-averaged Holocene climatic twin-dataset for mean total annual precipitation (PANN) and mean annual temperature (TANN) covering the last 10,000 years for the LYR region. This is based on the technique of weighted averaging-partial least squares regression to establish robust calibration models for obtaining reliable climatic inferences. The pollen-based reconstructions generally show an early Holocene climatic optimum with both abundant monsoonal rainfall and warm thermal conditions, and a declining pattern of both PANN and TANN values in the middle to late Holocene. The main driving forces behind the Holocene climatic changes in the LYR area are likely summer solar insolation associated with tropical or subtropical macro-scale climatic circulations such as the Intertropical Convergence Zone (ITCZ), Western Pacific Subtropical High (WPSH), and El Niño/Southern Oscillation (ENSO). Regional multi-proxy comparisons indicate that the Holocene variations in precipitation and temperature for the LYR region display an in-phase relationship with other related proxy records from southern monsoonal China and the Indian monsooninfluenced regions, but are inconsistent with the Holocene moisture or temperature records from northern monsoonal China and the westerly-dominated region in northwestern China. Overall, our comprehensive palaeoclimatic dataset and models may be significant tools for understanding the Holocene Asian monsoonal evolution and for anticipating its future dynamics in eastern Asia.

Download

Water management and wheat yields in ancient China: Carbon isotope discrimination of archaeological wheat grains

The Holocene

The evaluation of ancient crop production and its response to climate change is key to exploring ... more The evaluation of ancient crop production and its response to climate change is key to exploring the ancient demographic and social changes. Wheat is currently the third most widely cultivated crop worldwide and was a major component across of the agricultural systems of the ancient Eurasia. In this study, the Δ13C values of 116 charred wheat grains from 28 archaeological sites, with direct AMS 14C dating of 3952 ± 66 to 389 ± 73 cal yr BP, across northern China are reported. The result shows that the Δ13C values estimated wheat yields ranged from 0.5 to 2.5 Mg ha−1, during the past 4000 years. The water supply and grain yield of wheat cultivation is the highest in China during the Bronze Age; however, the water supply and yield were significantly affected by climate fluctuation in the middle-late Holocene. No significant long-term trend of increasing wheat yield is observed over this interval, but a correlation between Δ13C values estimated wheat yield and cyclical climate changes ...

Download

Dynamics of temperate rainforest from fine resolution pollen analysis, Upper Ringarooma River, northeastern Tasmania

Austral Ecology, 1998

ABSTRACT

Regional‐Scale Precipitation Anomalies in Northern China During the Holocene and Possible Impact on Prehistoric Demographic Changes

Geophysical Research Letters, 2018

Sensitive changes in precipitation influence the stability of semiarid ecosystem, rain-fed agricu... more Sensitive changes in precipitation influence the stability of semiarid ecosystem, rain-fed agriculture, and densely populated society in northern monsoonal China (NC). However, shortage of regional-scale quantitative syntheses imposes restrictions on investigating long-term relationships among precipitation dynamics, possible climatic forces, and prehistoric demographic fluctuations. Herein, we contribute a regionally compiled anomaly record for Holocene annual mean precipitation (PANN) relative to its modern-day values in NC. The Holocene PANN variations in NC may be essentially determined by changing thermal gradients of continental land-ocean and west-east equatorial Pacific, profoundly affecting strength and location of West Pacific Subtropical High that may principally modulate intensity of East Asian summer monsoon and resultant rainfall in NC. Importantly, variation partitioning analysis quantitatively demonstrates that the overall changes of precipitation (43.3%) may play a more important role than temperature (3.2%) and their shared effects (0.8%) in independently accounting for long-term variation of regional-scale Holocene population fluctuations in NC.

Download

Environmental Catastrophes and Recoveries in the Holocene

PAGES news, 2002

Download

Megadrought and cultural exchange along the proto-silk road

Science Bulletin, 2021

Arid Central Asia (ACA), with its diverse landscapes of high mountains, oases, and deserts, hoste... more Arid Central Asia (ACA), with its diverse landscapes of high mountains, oases, and deserts, hosted the central routes of the Silk Roads that linked trade centers from East Asia to the eastern Mediterranean. Ecological pockets and ecoclines in ACA are largely determined by local precipitation. However, little research has gone into the effects of hydroclimatic changes on trans-Eurasian cultural exchange. Here, we reconstruct precipitation changes in ACA, covering the mid-late Holocene with a U-Th dated,~3 a resolution, multi-proxy time series of replicated stalagmites from the southeastern Fergana Valley, Kyrgyzstan. Our data reveal a 640-a megadrought between 5820 and 5180 a BP, which likely impacted cultural development in ACA and impeded the expansion of cultural traits along oasis routes. Instead, it may have diverted the earliest transcontinental exchange along the Eurasian steppe during the 5th millennium BP. With gradually increasing precipitation after the megadrought, settlement of peoples in the oases and river valleys may have facilitated the opening of the oasis routes, ''prehistoric Silk Roads", of trans-Eurasian exchange. By the 4th millennium BP, this process may have reshaped cultures across the two continents, laying the foundation for the organized Silk Roads.

Download

The Holocene vegetation cover of Britain and Ireland: Overcoming problems of scale and discerning patterns of openness

Quaternary Science Reviews, 2013

The vegetation of Europe has undergone substantial changes during the course of the Holocene epoc... more The vegetation of Europe has undergone substantial changes during the course of the Holocene epoch, resulting from range expansion of plants following climate amelioration, competition between taxa and disturbance through anthropogenic activities. Much of the detail of this pattern is understood from decades of pollen analytical work across Europe, and this understanding has been used to address questions relating to vegetation-climate feedback, biogeography and human impact. Recent advances in modelling the relationship between pollen and vegetation now make it possible to transform pollen proportions into estimates of vegetation cover at both regional and local spatial scales, using the Landscape Reconstruction Algorithm (LRA), i.e. the REVEALS (Regional Estimates of VEgetation Abundance from Large Sites) and the LOVE (LOcal VEgetation) models. This paper presents the compilation and analysis of 73 pollen stratigraphies from the British Isles, to assess the application of the LRA and describe the pattern of landscape/woodland openness (i.e. the cover of low herb and bushy vegetation) through the Holocene. The results show that multiple small sites can be used as an effective replacement for a single large site for the reconstruction of regional vegetation cover. The REVEALS vegetation estimates imply that the British Isles had a greater degree of landscape/woodland openness at the regional scale than areas on the European mainland. There is considerable spatial bias in the British Isles dataset towards wetland areas and uplands, which may explain higher estimates of landscape openness compared with Europe. Where multiple estimates of regional vegetation are available from within the same region interregional differences are greater than intra-regional differences, supporting the use of the REVEALS model to the estimation of regional vegetation from pollen data.

Download

Scientific drilling workshop on the Weihe Basin Drilling Project (WBDP): Cenozoic tectonic–monsoon interactions

Scientific Drilling, 2020

The Weihe Basin, enclosed by the Chinese Loess Plateau to the north and the Qinling Mountains to ... more The Weihe Basin, enclosed by the Chinese Loess Plateau to the north and the Qinling Mountains to the south, is an outstanding, world-class continental site for obtaining high-resolution multi-proxy records that reflect environmental changes spanning most of the Cenozoic. Previous geophysical and sedimentary studies indicate that the basin hosts 6000-8000 m thick fluvial-lacustrine sedimentary successions spanning the Eocene to Holocene. This sedimentary record provides an excellent and unique archive to decipher long-term tectonicclimate interactions related to the uplift of the Tibetan Plateau, the onset/evolution of the Asian monsoon, and the development of the biogeography of East Asia. Owing to its location at the interface of the opposing westerly and Asian monsoon circulation systems, the Weihe Basin also holds enormous promise for providing a record of changes in these circulation systems in response to very different boundary conditions since the Eocene. To develop an international scientific drilling programme in the Weihe Basin, the Institute of Earth Environment, Chinese Academy of Sciences, organized a dedicated workshop with 55 participants from eight countries. The workshop was held in Xi'an, China, from 15 to 18 October 2019. Workshop participants conceived the key scientific objectives of the envisaged Weihe Basin Drilling Project (WBDP) and discussed technical and logistical aspects as well as the scope of the scientific collaboration in preparation for a full drilling proposal for submission to the International Continental Scientific Drilling Program (ICDP). Workshop participants mutually agreed to design a two-phase scientific drilling programme that will in a first phase target the upper 3000 m and in a second phase the entire up to 7500 m thick sedimentary infill of the basin. For the purpose of the 7500 m deep borehole, the world's only drill rig for ultra-deep scientific drilling on land, Crust 1, which previously recovered the entire continental Cretaceous sediments in the Songliao Basin, will be deployed in the WBDP.

Download

PEP II Meeting

PAGES news, 1998

Download

Pollen preservation and its potential influence on paleoenvironmental reconstruction in Chinese loess deposits

Review of Palaeobotany and Palynology, 2017

Abstract Pollen analysis in loess sediment has long been used to reconstruct Quaternary environme... more Abstract Pollen analysis in loess sediment has long been used to reconstruct Quaternary environmental change. However, caution should be taken as the reconstructed paleovegetation may be biased if pollen preservation is ignored. This paper investigates spatio-temporal pollen preservation condition and its causal factors in Chinese loess deposits, based on studying pollen of samples in three glacial and interglacial units across a climate gradient in China. We show that pollen concentration decreases from the cool and dry North China to warmer and wetter climate in more southerly locations at the same period. Pollen concentration in loess deposits is influenced by both pollen preservation and production, and the former one becomes the overwhelming factor where climate is quite warm and wet. Climate can influence pollen preservation by enhancing conditions for oxidation and microbial attack. Increasing temperature and moisture facilitates both the oxidation process and microbial destruction, which can result in pollen deterioration in loess deposits. In addition, a high soil pH can also cause pollen damage over time. These factors favour the relative preservation of several taxa such as Artemisia , Aster , Taraxacum , Pinus and Chenopodiaceae, and this leads to them dominating pollen spectra of Chinese loess deposits. The original pollen record suffers from the differential loss of taxa, especially toward southern loess regions and the absence of broadleaf forests or forest steppe reconstructed by pollen records may be attributable to this.

The 9.2 ka event in Asian summer monsoon area: the strongest millennial scale collapse of the monsoon during the Holocene

Climate Dynamics, 2017

Numerous Holocene paleo-proxy records exhibit a series of centennial-millennial scale rapid clima... more Numerous Holocene paleo-proxy records exhibit a series of centennial-millennial scale rapid climatic events. Unlike the widely acknowledged 8.2 ka climate anomaly, the likelihood of a significant climate excursion at around 9.2 cal ka BP, which has been notably recognized in some studies, remains to be fully clarified in terms of its magnitude and intensity, as well as its characteristics and spatial distributions in a range of paleoclimatic records. In this study, a peat sediment profile from the Dajiuhu Basin in central China was collected with several geochemical proxies and a pollen analysis carried out to help improve understanding of the climate changes around 9.2 cal ka BP. The results show that the peat development was interrupted abruptly at around 9.2 cal ka BP, when the chemical weathering strength decreased and the tree-pollen declined. This suggests that a strong drier regional climatic event occurred at around 9.2 cal ka BP in central China, which was, in turn, probably connected to the rapid 9.2 ka climate event co-developing worldwide. In addition, based on the synthesis of our peat records and the other Holocene hydrological records from Asian summer monsoon (ASM) region, we further found that the 9.2 ka event probably constituted the strongest abrupt collapse of the Asian monsoon system during the full Holocene interval. The correlations between ASM and the atmospheric 14C production rate, the North Atlantic drift ice records and Greenland temperature indicated that the weakened ASM event at around 9.2 cal ka BP could be interpreted by the co-influence of external and internal factors, related to the changes of the solar activity and the Atlantic Meridional Overturning Circulation (AMOC).

Quantifying climatic variability in monsoonal northern China over the last 2200 years and its role in driving Chinese dynastic changes

Quaternary Science Reviews, 2017

Our understanding on the spatial-temporal patterns of climatic variability over the last few mill... more Our understanding on the spatial-temporal patterns of climatic variability over the last few millennia in the East Asian monsoon-dominated northern China (NC), and its role at a macro-scale in affecting the prosperity and depression of Chinese dynasties is limited. Quantitative high-resolution, regionally-synthesized palaeoclimatic reconstructions as well as simulations, and numerical analyses of their relationships with various fine-scale, numerical agro-ecological, social-economic, and geo-political historical records during the period of China's history, are presented here for NC. We utilize pollen data together with climate modeling to reconstruct and simulate decadal-to centennial-scale variations in precipitation or temperature for NC during the last 2200 years (-200-2000 AD). We find an overall cyclic-pattern (wet/warm or dry/cold) in the precipitation and temperature anomalies on centennial-to millennial-scale that can be likely considered as a representative for the entire NC by comparison with other related climatic records. We suggest that solar activity may play a key role in driving the climatic fluctuations in NC during the last 22 centuries, with its quasi ~100, 50, 23, or 22-year periodicity clearly identified in our climatic reconstructions. We employ variation partitioning and redundancy analysis to quantify the independent effects of climatic factors on accounting for the total variation of 17 fine-grained numerical Chinese historical records. We quantitatively illustrate that precipitation (67.4 %) may 3 have been more important than temperature (32.5 %) in causing the overall agro-ecological and macro-geopolitical shifts in imperial China with NC as the central ruling region and an agricultural heartland over the last 2200 years.

Download

Dietary responses of Sahul (Pleistocene Australia–New Guinea) megafauna to climate and environmental change

Paleobiology, 2017

Throughout the late Quaternary, the Sahul (Pleistocene Australia–New Guinea) vertebrate fauna was... more Throughout the late Quaternary, the Sahul (Pleistocene Australia–New Guinea) vertebrate fauna was dominated by a diversity of large mammals, birds, and reptiles, commonly referred to as megafauna. Since ca. 450–400Ka, approximately 88 species disappeared in Sahul, including kangaroos exceeding 200kg in size, wombat-like animals the size of hippopotamuses, flightless birds, and giant monitor lizards that were likely venomous. Ongoing debates over the primary cause of these extinctions have typically favored climate change or human activities. Improving our understanding of the population biology of extinct megafauna as more refined paleoenvironmental data sets become available will assist in identifying their potential vulnerabilities. Here, we apply a multiproxy approach to analyze fossil teeth from deposits dated to the middle and late Pleistocene at Cuddie Springs in southeastern Australia, assessing relative aridity via oxygen isotopes as well as vegetation and megafaunal diets u...

Download

The nature of fluctuating lakes in the southern Amu-dar'ya delta

Palaeogeography, Palaeoclimatology, Palaeoecology, 2015

ABSTRACT

Late Quaternary fire regimes of Australasia

Quaternary International, 2012

We have compiled 223 sedimentary charcoal records from Australasia in order to examine the tempor... more We have compiled 223 sedimentary charcoal records from Australasia in order to examine the temporal and spatial variability of fire regimes during the Late Quaternary. While some of these records cover more than a full glacial cycle, here we focus on the last 70,000 years when the number of individual records in the compilation allows more robust conclusions. On orbital time scales, fire in Australasia predominantly reflects climate, with colder periods characterized by less and warmer intervals by more biomass burning. The composite record for the region also shows considerable millennial-scale variability during the last glacial interval (73.5e14.7 ka). Within the limits of the dating uncertainties of individual records, the variability shown by the composite charcoal record is more similar to the form, number and timing of DansgaardeOeschger cycles as observed in Greenland ice cores than to the variability expressed in the Antarctic ice-core record. The composite charcoal record suggests increased biomass burning in the Australasian region during Greenland Interstadials and reduced burning during Greenland Stadials. Millennial-scale variability is characteristic of the composite record of the subtropical high pressure belt during the past 21 ka, but the tropics show a somewhat simpler pattern of variability with major peaks in biomass burning around 15 ka and 8 ka. There is no distinct change in fire regime corresponding to the arrival of humans in Australia at 50 AE 10 ka and no correlation between archaeological evidence of increased human activity during the past 40 ka and the history of biomass burning. However, changes in biomass burning in the last 200 years may have been exacerbated or influenced by humans.

Download

Plant Geography

New Zealand Geographer, 1977