Bog Surface Research Articles

The influence of the hydrometeorological factors on the CO2 fluxes from the oligotrophic bog surface.

The influence of the hydrometeorological factors on the CO2 fluxes from the oligotrophic bog surface.

Investigation of buried karst sinkholes under a bog using ground penetrating radar (GPR) and electrical resistivity tomography (ERT)

AbstractActive evaporite karst processes in the Baltic states are associated with a few relatively small regions where gypsum rocks can be found close to the Earth's surface. One of these areas lies in the vicinity of the Pandu bog. However, such a possibly active karst region, which is covered by peat and in which the mapping of karst formations is complex, has not been previously investigated. In this study, we present a buried and peat‐filled karst cover‐collapse sinkhole mapping approach that involves a combination of ground‐penetrating radar (GPR), electrical resistivity tomography (ERT) and conventional boreholes. A detailed map of the bog's substratum topography was constructed from a geophysical surveying dataset. It reveals 15 distinctly expressed sinkholes with diameters of several tens of metres. Overall, 140 potential sinkholes were also mapped using remote sensing data in the vicinity of the bog. Higher electrical resistivity anomalies were identified inside the peat; they coincide with scatter‐free zones in GPR data and water layers in boreholes. Highly disturbed internal peat layering was also detected in these sinkholes. It is suggested that these water layers and disturbed peat layering may have formed due to the subsidence of the lower peat layers, and thus they represent relatively younger sinkholes. This is also supported by evidence from orthophoto maps, which showed the formation and disappearance of surficial lakes and depressions on the bog surface. Our results revealed the presence of active and widespread karst processes under the bog that have not been previously noticed despite the fact that they have implications for the assessment of geohazards in this area.

Water level variation at a beaver pond significantly impacts net CO2 uptake of a continental bog

Abstract. The carbon (C) dynamics of northern peatlands are sensitive to hydrological changes owing to ecohydrological feedbacks. We quantified and evaluated the impact of water level variations in a beaver pond (BP) on the CO2 flux dynamics of an adjacent, raised Sphagnum–shrub-dominated bog in southern Canada. We applied the CoupModel to the Mer Bleue bog, where the hydrological, energy and CO2 fluxes have been measured continuously for over 20 years. The lateral flow of water from the bog to the BP was estimated by the hydraulic gradient between the peatland and the BP's water level and the vertical profile of peat hydraulic conductivity. The model outputs were compared with the measured hydrological components, CO2 flux and energy flux data (1998–2019). CoupModel was able to reproduce the measured data well. The simulation shows that variation in the BP water level (naturally occurring or due to management) influenced the bog net ecosystem exchange (NEE) of CO2. Over 1998–2004, the BP water level was 0.75 to 1.0 m lower than during 2017–2019. Simulated net CO2 uptake was 55 gCm-2yr-1 lower during 1998–2004 compared to 2017–2019 when there was no BP disturbance, which was similar to the differences in measured NEE between those periods. Peatland annual NEE was well correlated with water table depth (WTD) within the bog, and NEE also shows a linear relation with the water level at the BP, with a slope of −120 gCO2-Cm-2yr-1m-1. The current modelling predicts that the bog may switch from CO2 sink to source when the BP water levels drop lower than ∼ 1.7 m below the peat surface at the eddy covariance (EC) tower, located on the bog surface 250 m from the BP. This study highlights the importance of natural and human disturbances to adjacent water bodies in regulating the net CO2 uptake function of northern peatlands.

PROPOSAL FOR THE INCLUSION OF TWO ACTIVE RAISED BOGS IN THE ROSCI0116 MOLHAȘURILE CĂPĂȚÂNEI PROTECTED AREA OF COMMUNITY INTEREST

Oligotrophic peat bogs reach the southern boundary of their European distribution area in the Romanian Carpathians. They shelter boreal species considered glacial relicts, surviving from the Würmian III period. Such areas (habitats) conserving relict species have major phytohistorical importance. They provide insights into the history of forest vegetation in the region and past climatic conditions. Based on floristic, phytocoenological and phytogeographical data, we propose to include two active raised bogs, namely “Calul de Piatră” and “Izvorul văii Șoimului” in the ROSCI0116 Molhașurile Căpățânei site of community interest. The inclusion of the two bogs in the ROSCI0116 Molhașurile Căpățânei protected area will increase the peat bog surface in the Apuseni Mountains and will be beneficial for the conservation of the wetland habitats and their typical flora, both very vulnerable to natural and anthropogenic disturbances.

Origin and fate of dissolved inorganic carbon in a karst groundwater fed peatland using δ13CDIC

Continental hydrosystems and in particular peatlands play an important role in the carbon cycle of the Critical Zone (CZ). Peatlands are important sinks for organic carbon and have therefore been extensively studied. However, peatlands are not only important for the fate of organic carbon, but they also affect the cycle of Dissolved Inorganic Carbon (DIC) of the peatland and the surrounding watershed. The fate of DIC is particularly complex in peatlands in limestone-dominated regions, because bicarbonate concentrations in surface and groundwater are high and the interaction between peatlands and surrounding hydrosystems are facilitated by the presence of highly permeable karst aquifers. In the present paper we study the origin and the fractionation of DIC in a peatland located on top of a karst aquifer. The study is based on hydrochemical and isotopic (δ13CDIC) data from samples recovered during 2 campaigns (low flow, high flow) at various depths within the Forbonnet peatland (Jura Mountains, eastern France), at the peatland outlet and at adjacent karst springs representing the underlying aquifer. In order to evaluate secondary fractionation processes, the measured δ13CDIC compositions were compared to modeled values considering the origin of DIC and potentially associated fractionation and speciation processes. The main results are: (1) DIC is lost at the bog surface by CO2 outgassing. (2) The δ13CDIC compositions of deep catotelm pore waters from the bog were much heavier than the modeled values. We relate this discrepancy to methanogenesis and show that this process is favored by reduced conditions at pH ∼ 6 and a HCO3− content of ∼1 mmol/L, most probably due to punctual groundwater inflows at the base of the bog. Finally, contrasted δ13CDIC compositions between the bog and the fen of the peatland reveal an additional ecohydrological control on DIC speciation.

Summer soil CO2 emission from bog surface: controlling factors

The peatlands in the northern hemisphere cover just 3% of the global landmass but their impact to the carbon emission is huge. The current climate changes exert influence on these ecosystems by changing water supply, temperature regime, plant growing activity and others. Nowadays studies predicted the important role of the northern bogs and peatlands as an additional source of atmospheric CO2. In our study we estimated how microrelief and microclimatic conditions can control the CO2 emission from the bog area. We compared also the waterlogged bog conditions and forest ecosystem to find out the main drivers of soil emission dynamics during the summer season. The rate of CO2 emission varies widely within bog area depending on the microrelief of the area: hollow – 0.74±0.03, ridge – 1.69±0.08 kg CO2 m–2. The comparative analysis versus the forest area showed that the upland parts of the bog area are not inferior to the forest area in terms of the emission rate. Moisture conditions determined the CO2 efflux for the hollow site (r=0.49, p<0.05) and forested area (r=0.39, p<0.05). The temperature impact is observed for all sites and it is significant throughout the season.

Late Holocene peat paleodust deposition in south-western Sweden - exploring geochemical properties, local mineral sources and regional aeolian activity

Atmospheric mineral dust not only interacts with the climate system by scattering incoming solar radiation and affecting atmospheric photochemistry, but also contributes critical nutrients to marine and terrestrial ecosystems. In a high-resolution analysis of paleodust deposition, peat development and soil dust sources, we assess the interplay between dust deposition and bog development of the Davidsmosse bog in south-western Sweden. Analyses of the 5400-year record (458 cm) included radiocarbon dating, bulk density, ash content, chemical and mineralogical composition and carbon stable isotopes, subsequently explored using principal component analysis. Fourteen dust events (DEs) were recorded (cal BP) in the peat sequence: 3580–3490; 3280; 3140; 3010–2840; 2740; 2610; 2480; 2340; 2240–2130; 1690; 1240; 960, 890–760, and 620–360. The majority of the DEs were coupled to increases in peat accumulation rates and increased nutrient content (N, P and K) suggesting that the DEs contributed with nutrients to the bog ecosystem, promoting increased accumulation. We also analyzed the chemical and mineral composition of potential mineral source deposits (separated into 6 grain-size fractions) from sites within a 4 km radius as well as aeolian dunes closer to the coast (25 km). The composition deposited on the present-day bog surface indicates that the bulk of the contemporary minerals have a local origin (<1.5 km), but the DEs may be of a more distant origin. The results also indicate that quartz and plagioclase feldspar content consistently increase with increasing grain-size, both in the source samples as well as in the peat sequence, and that the Si/Al ratio can be used to infer grain size changes in the peat. Two longer phases saw numerous DEs, between 2800 and 2130 cal BP and a stepwise increase from 960 towards 360 cal BP. The episodic character of the events, together with the inferred coarse grain size, suggest that the particles were deposited by (winter) storms. Future studies should include grain size analysis as well as a more in-depth comparison with regional paleo dust and storm records to increase knowledge on both transport processes (creep, saltation, suspension) and the climate processes driving late Holocene dust and storm events in Scandinavia.

Natural and manmade (137Cs) radioisotopes in Holocene sequence of the Sherstobitovsky raised bog in the Barabinsk forest-steppe (West Siberia)

The specific activities of natural (7Be, 210Pb) and manmade (137Cs) radioisotopes in a suspended matter of snow water have been determined and the density of their fallouts on the surface of the Sherstobitovsky and Ubinsky raised bogs in the Barabinsk forest-steppe has been assessed at the points of snow sampling during the winter period. It has been established that the main concentrator of the 7Be radioisotope is a fine fraction of suspended matter (colloidal particles <0.45 μm in size and dissolved component). For 210Pb, it is a coarse-grain fraction (dust particles >3 μm in size). The first data on the distribution of natural (238U, 210Pb, 226Ra, and 40K) and manmade (137Cs) radioisotopes have been obtained for raised bogs in the forest-steppe zone of Western Siberia. Migration of 137Cs deep down the peat deposit is largely governed by the magnitude of peat water level fluctuations during both the seasonal and long-term cycles and is closely related to the surface microrelief of the bog surface. Moreover, 137Cs, being the geochemical analogue of the biophilic 40K, is absorbed by plant roots from underlying peat horizons and transferred to the upper horizons during the dry seasons. An additional contribution to the high activity of 137Cs in the upper horizons is probably conditioned by its deposition on the surface of the Sherstobitovsky peat bog during its atmospheric transport as a result of peat and forest fires.

Mercury in the sediments of selected peatlands in Małopolska region

The mercury content in peat layers of seven peat bogs in the Małopolska region (Wolbrom in the Kraków-Częstochowa Upland and Otrębowskie Brzegi, Puścizna Wysoka, Puścizna Mała, Przybojec, Puścizna Długopole and Bór na Czerwonem in the Orawa-Nowy Targ Basin) was determined to a depth of 100 cm at a resolution of 1–2 cm. Geochemical background and level of anthropogenic mercury enrichment were determined for each peat bog. To establish the interdependence between mercury concentration, mineral matter content and selected metals, geochemical diagrams and models of the system were drawn up representing the correlational relationships between the selected geochemical variables for three of the peat bogs in the Orawa--Nowy Targ Basin (Otrębowskie Brzegi, Przybojec and Bór na Czerwonem). It was found that, comparing against other European raised bogs, the range of mercury concentrations in the peat layer down to 50 cm in the peatlands of Małopolska is similar to those in Norway, Sweden, Denmark and Spain, and decidedly lower than in the peatlands in Scotland, Belgium and Czechia. Furthermore, the sites in the Orawa-Nowy Targ Basin were clearly lower, the lower the altitude of the peat bog surface, which is probably associated with local topoclimatic conditions.

Social Context of Late Medieval and Early Modern Deforestation Periods in the Apuseni Mountains (Romania) based on an Integrated Evaluation of Historical and Paleobotanical Records

ABSTRACT Coeval changes in the reconstructed bog surface wetness and the pollen record of a peat sequence extracted from an ombrothropic bog (Calul de Piatră, 1630 m, Apuseni Mountains) allowed the natural and anthropogenic environmental changes over the past 1500 years to be assessed. The assessment of the social and economic context was also possible due to the exceptionally detailed documentary evidence of the investigated region. Four major deforestation periods in the past 1500 years were identified. Significant phases of deforestation coincided with particular social and political changes: (1) between AD 810 and 850, with the collapse of the Avar Khaganate and the expansion of the Bulgarian Empire in the southern areas of the Carpathian Basin; (2) between AD 1060 and 1170, with the establishment of the Kingdom of Hungary (AD 1000) and the foundation of royal, territorial administrative (county) and ecclesiastical centres of the feudal state; (3) in the sixteenth century (AD 1500–1570); and (4) after AD 1700, with population growth and economic development. Our results suggest that the observed deforestation and the consequent spread of subalpine farming were not necessarily related to the warmer or drier climatic periods, but to socioeconomic changes in nearby communities.

ПРИРОДНЫЕ РАДИОИЗОТОПЫ И 137CS В РАЗРЕЗЕ ШЕРСТОБИТОВСКОГО ВЕРХОВОГО БОЛОТА БАРАБИНСКОЙ ЛЕСОСТЕПИ (ЗАПАДНАЯ СИБИРЬ)

Specific activities of natural (7Be, 210Pb) and technogenic (137Cs) radioisotopes in the suspended matter of snow melted water have been determined and the density of their fallout on the surface of the Sherstobitovo and Ubinskoye peat bogs of the Baraba forest-steppe at the points of snow flow in winter period is estimated. It has been established that the main concentrator of the 7Be radioisotope is a finely dispersed fraction of suspended matter (&lt;0.45 μm), consisting of colloids and dissolved component, 210Pbatm is a coarse-grained fraction (&gt; 3 μm), consisting of dust particles. On the example of vertical profile of the Sherstobitovo peat bog, the first data on the distribution of natural (238U, 210Pb, 226Ra, 40K) and technogenic (137Cs) isotopes were obtained for peat bogs of forest –steppe zone of the Western Siberia. Both 226Ra and 238U show the same pattern of vertical distribution that is also usual for 137Cs and 40K. The increase of activity of these radionuclides is observed in the horizon of 6-12 cm as well as in the lower section part (25-35 cm). According to our assumption it is due to the same processes. Migration of 37Cs deep into peat accumulation is significantly determined by moor water fluctuations in the seasonal and long-term cycle, and it is closely related to the microrelief of bog surface. Besides, 137Cs, being a geochemical analogue of the 40K biophile, is pulled up from the underlying peat horizons by plant roots during the dry season. An additional contribution to the high activity of 137Cs in upper horizons is probably due to the input of 137Cs to the surface of the Sherstobitovo peat bog as a result of peat and forest fires.

Consistency of the Iksinskoe bog dynamics with extreme Holocene climate events

This research is devoted to the response of the southern taiga oligotrophic Iksinskoe bog to extreme Holocene climatic events. Based on data of preliminary geological exploration and 14 C-dated cores-analogues of this bog, a spatio-temporal model of paludification and vegetation succession from 11 paleosurface chrono-slices is created. It has been shown that the global dry cooling events of about 8200, 5900, 4900, and 2800 cal yr BP influenced the bog dynamics. Their direct impact is through the formation of a long-term thawing seasonal frost and permafrost water pressure as well as palsa. Their indirect impact is through a permafrost degradation and a subsequent warming. The cooling of 2800 cal yr BP had the maximum effect due to a drying and cryogenic peat accumulation stopping over a large area of the bog. During the subsequent warming of 2450 and 1900 cal yr BP there was a significant increase in the water content of the bog surface, and a phased oligotrophization of paleophytocenoses took place. The direct and indirect impacts of extremely dry Holocene cooling caused active paludificating, catastrophic changes in the paleophytocenoses, high water content of the surface, and reduced the depth of peat deposits of the Iksinskoe bog.

Seasonal patterns of greenhouse gas emissions from a forest‐to‐bog restored site in northern Scotland: Influence of microtopography and vegetation on carbon dioxide and methane dynamics

AbstractNorthern peatlands play an important role in the regulation of the atmospheric greenhouse gas (GHG) balance, functioning as a net carbon sink with low rates of organic decomposition. However, perturbations such as drainage increase peat oxidation, which may lead to enhanced gaseous release of carbon. For this reason, the number of restoration projects that aim to rewet blanket bogs has increased in the last few years, but there is still a lack of understanding of the impact of restoration on emissions of greenhouse gases, such as methane, particularly in sites restored from forestry. In this paper, we investigate the seasonal greenhouse gas dynamics in a forest‐to‐bog restoration site in Scotland. We analyse the effects of restoration on both carbon dioxide and methane fluxes, and investigate which site factors (microtopography, vegetation type, soil moisture and temperature) drive the processes of gaseous exchange between the bog surface and the atmosphere. Our results show that the original surface is near greenhouse gase equilibrium at −0.28 gCO2eq m2·day−1 and that microtopographic features act as a net greenhouse gas sink (ridges = −0.94 gCO2eq m2·day−1 and furrows = −0.86 gCO2eq m2·day−1), whereas the bog pool is a net source of greenhouse gases (0.98 gCO2eq m2·day−1). We found different vegetation species play a key role in greenhouse gas flux dynamics, especially in forestry‐derived microtopographical features, and their presence and influence on greenhouse gas dynamics should be accounted for to provide a more comprehensive understanding of emissions associated with restoration management practices.Highlights GHG (CO2 and CH4) dynamics in a boreal peatland restored from forestry are mainly affected by microtopography and vegetation. Forestry‐derived microforms (ridges and furrows) are better GHG sinks than pools (GHG emitters) and original surfaces (near GHG equilibrium). The presence of Trichophorum cespitosum leads to higher CH4 emissions. Restoration practices like terraforming may create a short‐term pulse net GHG emission due to an increase of both CH4 and CO2 fluxes.

Vegetation changes and plant wax biomarkers from an ombrotrophic bog define hydroclimate trends and human-environment interactions during the Holocene in northern Norway

Holocene climate records from northern Europe improve our understanding of important North Atlantic ocean and atmospheric circulation systems to long-term insolation-driven changes, as well as more rapid forcing and feedback mechanisms. Here we assess Holocene climate and environmental changes in northern Norway based on the analysis of pollen, non-pollen palynomorphs, plant macrofossils, and plant wax biomarkers from a high latitude ombrotrophic bog. We define the extent and thickness of Hollabåttjønnen Bog (0.16 km2), which is located 10 km north of Tromsø. Several cores were analyzed, including a 5.16-m core that spans the last 9.5 cal ka BP. Vegetation changes from several sites were reconstructed and the distribution and hydrogen isotopic composition (δD) of n-alkanes (C21–C33) were analyzed. Our data show several distinct climate intervals that primarily indicate changes in bog surface moisture. In the early Holocene (c. 9.5–7.7 cal ka BP), wetter conditions are defined by the presence of wetland sedges and grasses, higher concentrations of mid-chain length n-alkanes, and a similarity in δD values among homologs. A dry mid-Holocene (c. 7.7–3.8 cal ka BP) is inferred from the presence of a heath shrubland, low peat accumulations rates, and significant differences between δD values of mid- and long-chain length n-alkanes. The late Holocene (c. 3.8 cal ka BP-present) is marked by the onset of wetter conditions, lateral bog expansion, and an increase in sedges and grasses. The Hollabåttjønnen Bog record is also significant because its margins were an important location for human settlement. We correlate early Holocene environmental conditions with changes in Stone Age structures recently excavated, and we identify the occurrence of coprophilous fungi, such as Sporormiella and Sordaria, likely associated with reindeer grazing activity beginning c. 1 cal ka BP. This site therefore provides important regional paleoclimate information as well as context for evaluating local prehistoric human-environment interactions.

High-resolution patterns of palaeoenvironmental changes during the Little Ice Age and the Medieval Climate Anomaly in the northwestern Iberian Peninsula

A high resolution core (9.7 ​yr ​cm−1) from the Chao de Veiga Mol raised bog (NW Iberian Peninsula) was analyzed to identify plant macrofossils, estimate peat humification and calculate hydroclimatic indices based on current bog species, with the overall aim of determining the climate conditions associated with evolution of the bog during the Medieval Climate Anomaly and the Little Ice Age. These proxies, together with historical and climate data, proved to be good indicators of the changes in bog surface wetness. Analysisof the core led to identification of 9 different periods: two corresponding to the so-called Medieval Climate Anomaly (930 to 1345 AD, 1075–665 calibrated years before present [cal. yr BP]); four corresponding to the Little Ice Age (1345 to 1905 AD; 665–105 ​cal ​yr BP); and three corresponding to the last century (1905 to 2000 AD). The findings revealed a generally dry climate that lasted until the 14th century, followed by a transition to a long period with a more humid, but characteristically very variable climate, which ended at the beginning of the 20th century and was followed by a rapid transition to more humid conditions and finally, a change to drier conditions.The Medieval Climate Anomaly was indicated by the abundance of dry-adapted mosses (Leucobryum glaucum, Hypnum cupressiforme) and characterized by warm dry conditions and high levels of peat humification, with alternating wet phases. The LIA period was dated by a large abundance of Sphagnum species (an indicator of wetness) and a gradual increase in the humification index. However, four different climate phases were differentiated in this period.High-resolution reconstruction of the evolution of the CVM bog and the multiproxy approach have together enabled a more detailed identification of climatic variations in this area, which are generally consistent with the global models, as well as better definition of the elusive climatic oscillations in the last millennium and confirmation of the importance of local modulation of global models.The study provides new information and a detailed chronology of climatic events that will help to refine local modulation of the climate evolution model in the still quite unexplored region of the NW Iberian Peninsula, a key area for understanding the paleoclimatic dynamics in SW Europe.

Long Term Interferometric Temporal Coherence and DInSAR Phase in Northern Peatlands

Peatlands of northern temperate and cold climates are significant pools of stored carbon. Understanding seasonal dynamics of peatland surface height and volume, often referred to as mire breathing or oscillation, is the key to improve spatial models of material flow and gas exchange. The monitoring of this type of dynamics over large areas is only feasible by remote sensing instruments. The objective of this study is to examine the applicability of Sentinel-1 synthetic aperture radar interferometry (InSAR) to characterize seasonal dynamics of peatland surface height and water table (WT) over open raised bog areas in Endla mire complex in central Estonia, characteristic for northern temperate bogs. Our results show that InSAR temporal coherence, sufficient for differential InSAR (DInSAR), is preserved in the open bog over more than six months of temporal baseline. Moreover, the coherence which is lost in a dry summer, make a recovery in autumn correlate with WT dynamics. The relationship between the coherence from a single master image and the corresponding WT difference is described by the second degree polynomial regression model (Root Mean Squared Error RMSE = 0.041 for coherence magnitude). It is also demonstrated that DInSAR phase is connected to bog surface dynamics and reveals differences between bogs and for ecotopes within a bog. These findings suggest that InSAR long term temporal coherence could be used to describe seasonal bog WT dynamics and differentiate between mire types and ecotopes within a bog. Moreover, DInSAR analysis has the potential to characterize seasonal mire surface oscillation which may be important for assessing the capacity of water storage or restoration success in northern temperate bogs.

Bog Microtopography and the Climatic Sensitivity of Testate Amoeba Communities: Implications for Transfer Function-Based Paleo-Water Table Reconstructions.

Although the use of sub-fossil testate amoebae as a proxy for raised bog hydrology in Holocene paleoecological studies is well-established, some detailed aspects of species-environment relationships remain under-researched. One such issue is the effect of bog surface microtopography on the climatic sensitivity of testate amoeba communities. Although it has been suggested that some microforms-especially hummocks-may be less sensitive to climatic forcing than others, this has rarely been objectively tested. To investigate this, subfossil testate amoebae assemblages have been examined in a series of shallow cores collected along a hummock-lawn-hollow transect from a bog in central Ireland and the resulting reconstructed water table records, dated using 210Pb, have been compared with instrumental weather data. Testate amoebae communities in the hollow microform were found to be significantly less diverse than those in the hummock and lawn, and both the hummock and lawn showed statistically significant correlations with instrumental temperature and precipitation data. Therefore, whilst the suggestion that paleoecological investigations should target intermediate bog microforms remains sound, the notion that hummock-based testate amoebae hydrological data are climatically-insensitive is challenged.

On the brink of Armageddon? Climate change, the archaeological record and human activity across the Bronze Age–Iron Age transition in Ireland

Palaeoclimatic proxies from records in northwest Europe evidence a climatic deterioration, known as the ‘2.8 ka Event’, which broadly coincided with the transition from Later Bronze Age to Iron Age in Ireland. This Bronze Age-Iron Age transition in Ireland has been invoked in various hypotheses concerning the relationship between environmental and cultural change. This paper offers a brief review of contrasting archaeological interpretations of the transition, outlines the gaps and uncertainties in current knowledge and highlights the role of climate change in some of these uncertainties. This is followed by a discussion of palaeoclimate records from peatlands, and in particular the utility of bog surface wetness records (BSW) to identify geographically and chronologically coherent periods of Holocene climate change, including the period around 750 BC (2.8 ka), which is apparent in both UK and Irish records. Whilst BSW records provide evidence of relative shifts from wet/cold to warm/dry conditions, quantitative indices of temperature and precipitation cannot be derived from these data. Recent work discounting a link between a demographic ‘collapse’ and climate change is considered, as is the importance of local-scale records for understanding the archaeology of peatlands. The role of ‘bog burst’ events (catastrophic hydrological failures of the physical integrity of peatland) in driving palaeohydrological changes in certain Irish peatlands is outlined. Whilst ‘bog bursts’ might confound the extraction of regional climatic meaning, they provide important contextual evidence for human activity and the associated archaeological record. Although there are some coherent patterns in palynological records, others demonstrate spatial and chronological differences in vegetation change and human impact across the Late Bronze Age to Iron Age, but the implications for changes in the distribution of human populations are unclear. The paper concludes with a consideration of the importance of robust chronologies for integrating archaeological, palaeoenvironmental and palaeoclimatological data to investigate potential links between climate and cultural change. The importance of different analytical, spatial and chronological scales to investigate the complex and recursive nature of the relationship between human activity and climatic change is discussed.

On the brink of Armageddon? Climate change, the archaeological record and human activity across the Bronze Age–Iron Age transition in Ireland

Palaeoclimatic proxies from records in northwest Europe evidence a climatic deterioration, known as the ‘2.8 ka Event’, which broadly coincided with the transition from Later Bronze Age to Iron Age in Ireland. This Bronze Age-Iron Age transition in Ireland has been invoked in various hypotheses concerning the relationship between environmental and cultural change. This paper offers a brief review of contrasting archaeological interpretations of the transition, outlines the gaps and uncertainties in current knowledge and highlights the role of climate change in some of these uncertainties. This is followed by a discussion of palaeoclimate records from peatlands, and in particular the utility of bog surface wetness records (BSW) to identify geographically and chronologically coherent periods of Holocene climate change, including the period around 750 BC (2.8 ka), which is apparent in both UK and Irish records. Whilst BSW records provide evidence of relative shifts from wet/cold to warm/dry conditions, quantitative indices of temperature and precipitation cannot be derived from these data. Recent work discounting a link between a demographic ‘collapse’ and climate change is considered, as is the importance of local-scale records for understanding the archaeology of peatlands. The role of ‘bog burst’ events (catastrophic hydrological failures of the physical integrity of peatland) in driving palaeohydrological changes in certain Irish peatlands is outlined. Whilst ‘bog bursts’ might confound the extraction of regional climatic meaning, they provide important contextual evidence for human activity and the associated archaeological record. Although there are some coherent patterns in palynological records, others demonstrate spatial and chronological differences in vegetation change and human impact across the Late Bronze Age to Iron Age, but the implications for changes in the distribution of human populations are unclear. The paper concludes with a consideration of the importance of robust chronologies for integrating archaeological, palaeoenvironmental and palaeoclimatological data to investigate potential links between climate and cultural change. The importance of different analytical, spatial and chronological scales to investigate the complex and recursive nature of the relationship between human activity and climatic change is discussed.

Peat humification records from Restionaceae bogs in northern New Zealand as potential indicators of Holocene precipitation, seasonality, and ENSO

In comparison with temperature reconstructions, New Zealand proxy records for paleo-precipitation are rare, despite the importance of precipitation in contemporary climate variability and for projected climate impacts. In this study, records of mid-late Holocene palaeomoisture variation were derived for two hydrologically separate ombrotrophic Restionaceae bogs in northern New Zealand, based on peat humification analysis. At each site, three cores were analysed for peat humification, facilitating both intra- and inter-site comparisons. Age models for the six sequences were developed using radiocarbon dating and tephrochronology. Twelve tephras (including six cryptotephras) were recognised, four of which were used to precisely link the two sites and to define start and end points for the records at 7027 ± 170 (Tuhua tephra) and 1718 ± 10 cal yr BP (Taupo tephra) (2σ-age ranges), respectively. We find individual differences between the six peat humification records at short-term timescales that are presumably due to local site factors, in particular changing vegetation and microtopography, or to changes in the composition of the material analysed. Stronger longer-term coherence is observed between all six records but is attributed to slow anaerobic decay over time because the implied trend towards wetter summers in the late Holocene cannot be corroborated by independent climate proxies. Despite these confounding factors, centennial scale shifts in bog surface wetness are a pervasive feature of all six records with varying degrees of overlap in time that show strong correspondence with El Niño-Southern Oscillation reconstructions from the eastern equatorial Pacific. These results indicate the potential for peat humification records from New Zealand's ombrotrophic bogs to elucidate past climate variability and also demonstrate the importance of developing multiple well-dated profiles from more than one site.