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Relative weakness in sensitivity and contribution integration, especially lack of specific indicators at spatial and temporal scales, may hinder the formation of systematic knowledge for climate change impact on vegetation activity. Considering the interannual variability and periods difference, we investigated the ecosystem sensitivity to hydrothermal conditions and the contribution of individual climatic factors to vegetation activity on spatiotemporal scales during the period of 1980s–2013 in China. We ran simulations of the Common Land Model (CoLM) to obtain the photosynthetic rate, and used the satellite-derived Normalized Difference Vegetation Index (NDVI), to which we applied a temporal sensitivity analysis, the slope change ratio of accumulative quantity (SCRAQ), and geographical detectors. We show that the discrepancy between warming and precipitation variation contributed to vegetation activity was more notable than the ecosystem sensitivity to hydrothermal conditions, regardless of which temporal and spatial scale was considered. The sensitivity of vegetation activity to hydrothermal variation in most parts of northeastern and western China was higher than elsewhere, and the contribution of warming to vegetation dynamics was relatively high in the Inner Mongolian Plateau and Tibetan Plateau (>60%), where the contribution of warming to the vegetation distribution was also greater than elsewhere in China. Conversely, the contribution of precipitation variation to vegetation dynamics was comparatively greater in northwestern China and subtropical and tropical regions (>55%). The spatiotemporal contribution of precipitation variation to vegetation activity differed between regions, especially on the Tibetan Plateau and in subtropical and tropical regions. Moreover, both the temporal and spatial sensitivities to climate change were weak in the subtropical and tropical regions, where the contribution of climatic factors to vegetation distribution was also small. Overall, temperature sensitivity and its contribution to vegetation activity were positively associated in most regions. However, the regions where precipitation contributed substantially to vegetation activity were not necessarily also highly sensitive to changes in precipitation within the range of variation explored.

Well-preserved beetle elytra from the fossil and subfossil record are used by palaeoclimatologists to estimate past temperatures. Beetle-derived estimates of temperature across the Pliocene Arctic are consistently lower than those derived from other palaeoclimate proxies. Here we test if that pattern is attributable to either the modern dataset or specific mutual climatic range method (MCRM). We used a global dataset of observations (Global Biodiversity Information Facility) for modern beetles as opposed to a North American regional dataset, and a consistent MCRM for comparison to vegetation-derived estimates, termed CRACLE (Climate Reconstruction Analysis using Coexistence Likelihood Estimation), rather than different MCRM methods for each analysis. Beetle-derived estimates from one site, Beaver Pond, are consistently much lower than the vegetation-derived estimates, stable isotope results from flora and fauna, and summer temperatures from bacterial tetraethers. The reanalysis of beetle data produced a small reduction in proxy estimate mismatch overall. We found good agreement among proxy estimates of maximum temperature of the warmest month for two of the three sites in the Canadian Arctic, but increasingly poorer agreement for warmest quarter, coldest quarter and minimum temperature of the coldest month. This pattern may be due to beetles' avoidance mechanisms and a climate space different from modern calibration sets during the Pliocene. Beetle derived temperature estimates, especially cold season, should be interpreted with caution when reconstructing palaeoclimates.

Arctic warming is expected to accelerate northward migration of the boreal zone, altering the boreal wildfire regime, with changes in fire frequency, intensity, size, and fire season length. The closest analogue to these future high latitude climate conditions occurred during the Pliocene Epoch (2.58–5.33 Ma). Palaeoenvironmental reconstructions at four Pliocene-aged sites across the Canadian Arctic Archipelago reveal that boreal forest occurred at the southern-most site on Banks Island (74.30°N), while open forest or tundra-forest ecosystems existed further north, characterized by species tolerant of low to moderate fire intensity. The climate that supported these ecosystems was much warmer and wetter than the current climate of the Canadian Arctic Archipelago. Charcoal was discovered in samples across all sites, suggesting that wildfire was ubiquitous within these ecosystems and climate regimes. The reflectance of the charcoal is consistent with crowning fire or a mixed fire regime on Banks Island and a surface fire regime on Meighen and Ellesmere islands. Boreal forest in southern Ontario, Canada, and open taiga are potential analogues for southern and northern Pliocene Arctic ecosystems , respectively.

Proxy reconstructions of the mid-Piacenzian warm period (mPWP, between 3.264 and 3.025 Ma) suggest terrestrial temperatures were much warmer in the northern high latitudes (55°–90°N, referred to as NHL) than present-day. Climate models participating in the Pliocene Model Intercomparison Project Phase 1 (PlioMIP1) tend to underestimate this warmth. For instance, the underestimate is ∼10 °C on average across NHL and up to 17 °C in the Canadian Arctic region in the Community Climate System Model version 4 (CCSM4). Here, we explore potential mPWP climate forcings that might contribute to this mPWP mismatch. We carry out seven experiments to assess terrestrial temperature responses to Pliocene Arctic gateway closure, variations in CO 2 level, and orbital forcing at millennial time scale. To better compare the full range of simulated terrestrial temperatures with sparse proxy data, we introduce a pattern recognition technique that simplifies the model surface temperatures to a few representative patterns that can be validate with the limited terrestrial proxy data. The pattern recognition technique reveals two prominent features of simulated Pliocene surface temperature responses. First, distinctive patterns of amplified warming occur in the NHL, which can be explained by lowered surface elevation of Greenland, pattern and amount of Arctic sea ice loss, and changing strength of Atlantic meridional overturning circulation. Second, patterns of surface temperature response are similar among experiments with different forcing mechanisms. This similarity is due to strong feedbacks from responses in surface albedo and troposphere water vapor content to sea ice changes, which overwhelm distinctions in forcings from changes in insolation, CO 2 forcing, and Arctic gateway closure. By comparing CCSM4 simulations with proxy records, we demonstrate that both model and proxy records show similar patterns of mPWP NHL terrestrial warmth, but the model underestimates the magnitude. High insolation, greater CO 2 forcing, and Arctic gateways closure each contributes to reduce the underestimate by enhancing the Arctic warmth of 1–2 °C. These results highlight the importance of considering proxy NHL warmth in the context of Pliocene Arctic gateway changes, and variations in insolation and CO 2 forcing.

The mid-Pliocene is a valuable time interval for understanding the mechanisms that determine equilibrium climate at current CO2 concentrations. One intriguing, but not fully understood, feature of the early to mid-Pliocene climate is the amplified arctic temperature response. Current models underestimate the degree of warming in the Pliocene Arctic and validation of proposed feedbacks is limited by scarce terrestrial records of climate and environment, as well as discrepancies in current CO2 proxy reconstructions. Here we reconstruct the CO2 and summer temperature from a re-dated 3.9 +1.5/−0.5 Ma sub-fossil fen-peat deposit on west-central Ellesmere Island, Canada, and investigate fire as a potential feedback to Arctic amplification of warming during the mid-Pliocene. Average CO2 was determined using isotope ratios of mosses to be 440 ± 50 ppm. The estimate for average mean summer temperature is 15.4 ± 0.8 °C using specific bacterial membrane lipids, i.e. branched glycerol dialkyl glycerol tetraethers. Macro-charcoal was present in all samples from this Pliocene section with notably higher charcoal concentration in the upper part of the sequence. This change in charcoal was synchronous with a change in vegetation that saw fire promoting taxa increase in abundance. Paleovegetation reconstructions are consistent with warm summer temperatures, relatively low summer precipitation and an incidence of fire comparable to fire adapted boreal forests of North America, or potentially central Siberia. To our knowledge, this study represents the furthest northern evidence of fire during the Pliocene and highlights the important role of forest fire in the ecology and climatic processes of the Pliocene High Arctic. The results provide evidence that terrestrial fossil localities in the Pliocene High Arctic were probably formed during warm intervals that coincided with relatively high CO2 concentrations that supported productive biotic communities. This study indicates that interactions between paleovegetation and paleoclimate were mediated by fire in the High Arctic during the Pliocene, even though CO2 concentrations were only ~ 30 ppm higher than modern.

Although the mid- to Late Cretaceous is regarded as a global warm period, increasingly a more complex picture of warming and cooling is emerging. New techniques allow more precise dating of terrestrial localities, opening opportunities for using climate proxy approaches on terrestrial fauna and flora to better capture the complexity of Cretaceous climate. Here an attempt is made to understand the seasonality and inter-annual variability of two newly dated localities from the upper preserved portion (Cenomanian–Turonian) of the Winton Formation, Australia. Primarily quantitative approaches to palaeodendrology are used. The results suggest both seasonality and high variability in climate conditions that affect growth between years, including evidence for floods. The longest series (QM F44338) suggests oscillatory patterns of good and poor growth in a 15 year alternating cycle similar to the contemporary Pacific Decadal Oscillation, although other potential explanations should be considered and tested.

A recurring goal in ecological and paleoclimatic studies is to either forecast how ecosystems will respond to future climate or hindcast climate from past ecosystem assemblages. The Pliocene is a useful deep-time laboratory for understanding an equilibrium climate state under modern atmospheric CO2, and has been a focus for climate modelers. Accurate estimates of proxy data-model mismatch are hindered by the scarcity of well-constrained observations from well-dated sites in the High Arctic. Using a recently developed community-based approach (Climate Reconstruction Analysis using Coexistence Likelihood Estimation: CRACLE) compared with an established method (The Coexistence Approach: CA), and applied to extraordinary, permafrost-driven preservation of floras, we explore the climate and community assemblages at five Pliocene sites in the Canadian Arctic Archipelago. The results suggest that climatic differences at this scale do not simply correlate to differences in community assemblage between sites. The threshold temperature for tree line is one important component, but other factors in the environment (e.g., soil characteristics) may drive dissimilarity of communities where the taxa could share the same climate space. Estimates from CRACLE agree with previous estimates where available, and generally fall within the ranges of CA. Mean annual temperatures were ~22°C hotter (ranging from 0.8 to 6.2°C by species across sites) and mean annual precipitation ~500 mm wetter (ranging from 530 to 860 mm by species across sites) during the Early to “mid”-Pliocene (~3.6 Ma) when compared with modern climate station data in the Canadian Arctic Archipelago. Comparison of estimates for three levels of taxonomic input suggest judicious interpretation is needed when generic level identifications are used, especially in the Polar Regions. The results herein are a reminder of the large impact of non-climatic abiotic and biotic factors to be accounted for when predicting future ranges of communities under different climate conditions from the present, and when hindcasting climate from past ecosystem assemblages.

Leaf floras in fluvial-lacustrine sediments of the Upper Cretaceous (Cenomanian-Turonian) portion of the Winton Formation suggest a community with co-dominance of angiosperms, conifers, ginkgo and other seed plants. To date wood floras associated with the Winton Formation have not been examined in detail. Winton Formation wood has been presumed to comprise araucarian, podocarp and taxodiaceous components, but this has been based largely on the identification of other plant macro and microfossils. Here we describe a new species of podocarp fossil wood from the genus Protophyllodadoxylon based on eleven specimens of silicified wood found as surface material at two broadly coeval sites in the Cenomanian-Turonian portion of the Winton Formation: QM L311 and Bladensburg National Park. The new species is characterised by the presence of araucaroid tracheid pitting and phyllodadoid oopores, the absence of oculipores, and the paired arrangement of the oopores within the crossfields. The recognition of Protophyllocladoxylon in the Winton Formation supports previous palynological frequency counts that suggest a dominance of podocarp conifers. (C) 2014 Elsevier B.V. All rights reserved.

Fletcher, T.L. & Salisbury, S.W., XX.XX. 2014. Probable oribatid mite (Acari: Oribatida) tunnels and faecal pellets in silicified conifer wood from the Upper Cretaceous (Cenomanian–Turonian) portion of the Winton Formation, central-western Queensland, Australia. Alcheringa 38, 541–545. ISSN 0311-5518.Tunnels and faecal pellets likely made by oribatid mites have been found in silicified conifer wood from the Upper Cretaceous (Cenomanian–Turonian) portion of the Winton Formation, central-western Queensland, Australia. Although this is the first identified and described record of oribatid mites in the Mesozoic of Australia, other published, but unassigned material may also be referable to Oribatida. Current understanding of the climatic significance of mite distribution is limited, but the presence of oribatids and absence of xylophagus insects in the upper portion of the Winton Formation are consistent with indications that the environment in which this unit was deposited was relatively warm and wet for its...

This study reports two multi-century regional reconstructions of annual precipitation based on Pinus ponderosa and P. edulis from four sites in central northern Arizona. It compares standard regional and time-nested methods to generate reconstructions from 1581–2016 C.E. and 1529–2016 C.E., respectively. The strongest climate relationship is a positive correlation between total ring width and 12-month total precipitation ending in July of the growth year. The chronologies account for 50% of the variance of observed annual precipitation in the regional model and 59%, 60%, and 47% and 35% in the nested models. The two reconstructions are highly correlated (Pearson's correlation r > 0.97, p < 0.001) demonstrating that the reconstructions are highly similar over the period common to both reconstructions, with the nested-models’ advantage of extending the range of the reconstruction. The precipitation reconstructions are significantly correlated (r = 0.66, p < 0.001) with the North American Drought Atlas (NADA).

Psephophorus polygonusMeyer, 1847, the first fossil leatherback turtle to be named, was described on the basis of shell ossicles from the middle Miocene (MN6–7/8?) of Slovakia. The whereabouts of this material is uncertain but a slab on display at the Naturhistorisches Museum Wien is considered the neotype. We rediscovered further type locality ossicles in four European institutions, re-evaluated their gross morphology and described for the first time their microstructure by comparing them withDermochelys coriacea, the only living dermochelyid turtle. The gross morphology is congruent with that already described forP. polygonus, but with two significant exceptions: the ridged ossicles ofP. polygonusmay have a distinctly concave ventral surface as well as a tectiform shape in cross-section. They do not develop the external keel typical of many ossicles ofD. coriacea. Both ridged and non-ridged ossicles ofP. polygonusare characterized by compact diploe structures with an internal cortex consisting of a coarse fibrous meshwork, whereas the proportionately thinner ossicles ofD. coriaceatend to lose the internal cortex, and thus their diploe, during ontogeny. The ossicles of bothP. polygonusandD. coriaceadiffer from those of other lineages of amniotes whose carapace is composed of polygonal ossicles or platelets, in having growth centres situated at the plate centres just interior to the external bone surface and not within the cancellous core or closer to the internal compact layer. The new diagnosis ofP. polygonusallows us to preliminarily re-evaluate the taxonomy of some of thePsephophorus-like species. Despite some macro- and micromorphological differences, it seems likely thatPsephophoruswas as cosmopolitan as extantDermochelysand had a broadly similar ecology, with a possible difference concerning the dive depth.

Pterosaur fossils from Australia are rare. All the specimens that have been described previously are Cretaceous in age, with the majority deriving from the Aptian–Albian shallow marine succession within the Eromanga Basin of western Queensland. The Queensland specimens have tentatively been referred to the pterodactyloid clades Pteranodontidae, Ornithocheiridae, and Archaeopterodactyloidea (cf. Ctenochasmatoidea), each in varying taxonomic guises. Due to their fragmentary nature, more specific referrals of these specimens have not been possible. As such, the overall composition and more precise relationships of Australia's Cretaceous pterosaur fauna have remained enigmatic. Since 1987, a number of new pterosaur specimens have been found in the shallow marine late Albian rocks of the Eromanga Basin of western Queensland. Four of these specimens are described herein: a partial mandible, a metacarpal IV, a wing phalanx, and a humerus. The mandible is assigned to Ornithocheiridae, gen. et sp. indet.,...

The Winton Formation is increasingly recognised as an important source of information about the Cretaceous of Australia, and, more broadly, the palaeobiogeographic history of eastern Gondwana. With more precise dating and stratigraphic controls starting to provide temporal context to the geological and palaeontological understanding of this formation, it is timely to reassess the palaeoenvironment in which it was deposited. This new understanding helps to further differentiate the upper, most-studied portion of the formation (Cenomanian–Turonian) from the lower portions (Albian–Cenomanian), allowing a coherent picture of the ecosystem to emerge. Temperatures during the deposition of the Upper Cretaceous portion of the Winton Formation were warm, with high, seasonal rainfall, but not as extreme as the modern monsoon. The landscape was heterogeneous, a freshwater alluvial plain bestrode by low energy, meandering rivers, minor lakes and mires. Infrequent, scouring flood events were part of a multi-year cycle of drier and wetter years. The heavily vegetated flood plains supported abundant large herbivores. This was the final infilling of the great Eromanga Basin.

This short summary presents selected results of an ongoing investigation into the feedbacks that contribute to amplified Arctic warming. The consequences of warming for Arctic biodiversity and landscape response to global warmth are currently being interpreted. Arctic North American records of large-scale landscape and paleoenvironmental change during the Pliocene are exquisitely preserved and locked in permafrost, providing an opportunity for paleoenvironmental and faunal reconstruction with unprecedented quality and resolution. During a period of mean global temperatures only ~2.5°C above modern, the Pliocene molecular, isotopic, tree-ring, paleofaunal, and paleofloral records indicate that the high Arctic mean annual temperature was 11°C–19°C above modern values, pointing to a much shallower latitudinal temperature gradient than exists today. It appears that the intense Neogene warming caused thawing and weathering to liberate sediment and create a continuous and thick (>2.5 km in places) clastic wedge from at least Banks Island to Meighen Island to form a coastal plain that provided a highway for camels and other mammals to migrate and evolve in the high Arctic. In this summary we highlight the opportunities that exist for research on these and related topics with the PoLAR-FIT community.RÉSUMÉCe bref résumé présente les résultats choisis d'une enquête en cours sur les déclencheurs qui contribuent à l’amplification du réchauffement de l'Arctique. Les conséquences du réchauffement sur la biodiversité arctique et de la réponse du paysage au réchauffement climatique sont en cours d’être interprété. Des dossiers nord-américains de paysage à grande échelle et le changement paléoenvironnementales durant le Pliocène sont exceptionnellement préservés et scellées dans un état de congélation qui fournissant une occasion pour la reconstruction paléoenvironnementale et faunistique avec une qualité et une résolution sans précédent. Pendent une période de réchauffement global seulement ~2,5°C au-dessus de moderne les dossiers, moléculaire, isotopique, annaux de croissance, paléofaunistique et paléovégétation indiquent que l'Arctique a connu une augmentation de la température annuelle moyenne de 11°C–19°C au-dessus de moderne, en montrant un inferieur gradient de température latitudinal qu'aujourd'hui. Il semble que le réchauffement intense pendent le Néogène a provoqué la décongélation et erosion pour libérer les sédiments et créer une plaine côtière continuel et épaisse (> 2,5 km dans lieux) qui a fourni une route pour les chameaux et autres mammifères pour migrer et évoluer dans l’Haut-Arctique. Dans ce résumé, nous soulignons les opportunités qui existent pour la recherche sur ces sujets et les sujets connexes avec la communauté PoLAR-FIT.

Although there is a broad knowledge of Cretaceous climate on a global scale, quantitative climate estimates for terrestrial localities are limited. One source of terrestrial palaeoproxies is foliar physiognomy. The use of foliar physiognomy to explore Cretaceous assemblages has been limited, and some of its potential sources of error have not been fully explored. Although museum collections house a wealth of material, collection bias toward particular taxa or preservation qualities of specimens further magnifies existing taphonomic bias to cold temperatures. As a result, specific collection for foliar physiognomy can be necessary. Here, we conduct three foliar physiognomic analyses on the early Late Cretaceous Lark Quarry flora and assess the results in the context of other proxies from the same formation. Our results suggest that the climate at the Cenomanian–Turonian boundary in central western Queensland was warm and had high precipitation (leaf-area analysis: 1321 mm + 413 mm – 315 mm mean annual precipitation; leaf-margin analysis: 16.4°C mean annual temperature, 5.3°C binomial sample error; climate leaf-analysis multivariate program: 16 ± 2°C for mean annual temperature, 9-month growth season, 1073 ± 483 mm growth-season precipitation). Our analysis also gave higher mean annual temperature estimates than did a previous analysis by climate leaf-analysis multivariate program, based on museum collections for the Winton Formation.