Paleoecological Reconstructions Research Articles

Paleoenvironments reconstructed from the analyses of loess sequences on Susak Island, Adriatic Sea

Susak Island is the outermost member of the archipelago of the Kvarner Bay, North Adriatic Sea, Croatia. Its long-term landscape evolution is defined by tectonic movements. Most characteristic are partly exhumed landforms of an ancient terrane (scarps, uplifted limestone cliffs) in a still active neotectonic environment, but the most appropriate tools for the reconstruction of Quaternary paleoenvironments are loess and loess-like deposits. The Quaternary sequence is up to almost 100 m thickness locally and intensively studied by numerous disciplines (from structural geology to geochemistry and geomorphology) today. The special location of the island makes it a key area of research into the evolution of the broader environment, including the Po Plain as well as other Italian source areas of wind-borne and redeposited dust. The loess mantle was also of great importance for a paleoecological reconstruction of floral and faunal evolution, on which efforts of nature conservation are founded.

Taphonomy of bird (Aves) remains at Laili Cave, Timor-Leste, and implications for human-bird interactions during the Pleistocene

The significance of the role of birds in hominin evolution in Island Southeast Asia is not clear. Few avian vertebrate deposits have been recovered from archaeological or fossil sites in the region, and their association with either hominin or natural deposition in caves and rock shelters complicates their usefulness in hominin behavioural and palaeoecological reconstructions. In this paper, we assess the taphonomic history of the Pleistocene avian vertebrate remains recovered from Laili Cave, Timor-Leste, dated to between ca. 44.6 to 11.2 ka and in association with abundant lithic material. We use avian taxonomic composition, skeletal element abundance, and bone surface modification data to determine the agent of avian skeletal deposition. Our analyses indicate that the small grassland and woodland birds (quail, buttonquail, song birds), which dominate the assemblage, were deposited by avian predators (probably barn owls) throughout the sequence. Humans possibly hunted the small quantity of larger birds (imperial pigeon, duck). The bird remains suggest that grasslands, woodland savannahs, wetlands, and forest environments were present locally during the Pleistocene.

The role of fires in the Holocene landscape dynamics of the southeastern part of Meshchera Lowlands

The reconstructions of landscape dynamics and fire regimes in the southeastern part of Meshchera Lowlands in the Holocene are presented. Based on study of the fire layers in peat deposits of bogs, as well as botanical and palynological analyses of peat and morphological analysis of soils, it was established that the long-period dynamics for landscapes of the territory during the Middle and Late Holocene was determined primarily by shifts in fire regimes. Since 8000 cal. yr. BP, periods with high fire frequency (from 15–20 to 120 years) alternated with intervals when the fire frequency varied from 500–600 to 1800 years. The paleoecological reconstructions showed that increased fire activity was also recorded prior to human settlement in the southeastern part of the Meshchera Lowlands, when the action of the anthropogenic factor was the lowest.

The effectiveness of isometric contractions combined with eccentric – concentric training and simple lumbopelvic control exercises on pain and disability in chronic patellar tendinopathy: A case report

Paleoecological reconstructions of past climate are often based on a single taxonomic group with a consistent presence. Less is known about the relationship between multi-taxon community-wide change and climate variability. Here we reconstruct paleoecological change in a Late Quaternary (16.1–3.4 ka) sediment core from the California margin (418 m below sea level) of Santa Barbara Basin (SBB), USA, using Mollusca (Animalia) and Foraminifera (Rhizaria) microfossils. Building upon previous investigations, we use multivariate ordination and cluster analyses to interpret community-scale changes in these distinctly different taxonomic groups across discrete climate episodes. The strongest differences between seafloor biological communities occurred between glacial (prior to Termination IA, 14.7 ka) and interglacial climate episodes. Holocene communities were well partitioned, indicating that sub-millennial oceanographic variability was recorded by these microfossils. We document strong evidence of chemosynthetic trophic webs and sulfidic environments (from gastropod Alia permodesta and bivalve Lucinoma aequizonata), which characterized restricted intervals previously interpreted as well oxygenated (such as the Pre-Bølling Warming). Mollusc records indicate first-order trophic energetic shifts between detrital and chemosynthetically-fixed carbon. Molluscs associated with widely different physiological preferences occur here within single, decadal intervals of sediment, and as such mollusc assemblages may reflect significant inter-decadal oceanographic variability. Foraminifera assemblages provide exceptional records of the sequential, chronological progression of the deglacial climatic and oceanographic events, whereas mollusc assemblages reflect non-chronological similarities in reoccurring communities. Foraminifera taxa that drive community similarity here are also independently recognized as marker species for seafloor hypoxia regimes, which provides support for the idea that oxygenation change is a principal driver of seafloor environmental variability.

Dental microwear textural analysis as an analytical tool to depict individual traits and reconstruct the diet of a primate.

Dental microwear is a promising tool to reconstruct animals' diet because it reflects the interplay between the enamel surface and the food items recently consumed. This study examines the sources of inter-individual variations in dietary habits in a free-ranging population of mandrills (Mandrillus sphinx) using a combination of feeding monitoring and in vivo dental microwear textural analysis (DMTA). We investigated the impact of seasonality and individual traits on four DMTA parameters. In parallel, we further studied the influence of the physical properties of the food items consumed on these four parameters, using three proxies (mechanical properties, estimates of phytolith and external grit contents). We found that seasonality, age, and sex all impact DMTA parameters but those results differ depending on the facet analyzed (crushing vs. shearing facets). Three DMTA parameters (anisotropy, complexity, and heterogeneity of complexity) appear sensitive to seasonal variations and anisotropy also differs between the sexes while textural fill volume tends to vary with age. Moreover, the physical properties of the food items consumed vary seasonally and also differ depending on individual sex and age. Considering the interplay between the tested variables and both dental microwear and diet, we reaffirm that food physical properties play a major role in microwear variations. These results suggest that DMTA parameters may provide valuable hints for paleoecological reconstruction using fragmentary fossil dental remains.

Ecomorphological characterization of murines and non-arvicoline cricetids (Rodentia) from south-western Europe since the latest Middle Miocene to the Mio-Pliocene boundary (MN 7/8-MN13).

Rodents are the most speciose group of mammals and display a great ecological diversity. Despite the greater amount of ecomorphological information compiled for extant rodent species, studies usually lack of morphological data on dentition, which has led to difficulty in directly utilizing existing ecomorphological data of extant rodents for paleoecological reconstruction because teeth are the most common or often the only micromammal fossils. Here, we infer the environmental ranges of extinct rodent genera by extracting habitat information from extant relatives and linking it to extinct taxa based on the phenogram of the cluster analysis, in which variables are derived from the principal component analysis on outline shape of the upper first molars. This phenotypic “bracketing” approach is particularly useful in the study of the fossil record of small mammals, which is mostly represented by isolated teeth. As a case study, we utilize extinct genera of murines and non-arvicoline cricetids, ranging from the Iberoccitanian latest middle Miocene to the Mio-Pliocene boundary, and compare our results thoroughly with previous paleoecological reconstructions inferred by different methods. The resultant phenogram shows a predominance of ubiquitous genera among the Miocene taxa, and the presence of a few forest specialists in the two rodent groups (Murinae and Cricetidae), along with the absence of open environment specialists in either group of rodents. This appears to be related to the absence of enduring grassland biomes in the Iberian Peninsula during the late Miocene. High consistency between our result and previous studies suggests that this phenotypic “bracketing” approach is a very useful tool.

Cytotoxic activity of “Daniellia oliveri” extract in human colon cancer cell lines

Sediment cores obtained from two deep (>15 m) glacial lakes were analyzed in context of terrestrial vegetation development and in-lake processes from the Retezat Mountains (Southern Carpathians, Romania). Only the Holocene parts were chosen for study for testing what is the connection between geochemical changes and biotas around and in the lakes. The lakes are situated at slightly different altitudes on the northern (Lake Gales, 1990 m a.s.l.) and southern slope (Lake Bucura, 2040 m a.s.l.), respectively. Changes in geochemical composition were relatively low amplitude during the studied period (10,300–1790 and 10,300–695 cal yr BP) in both lakes, but the applicability of enrichment factor (EF) for geochemical elements and diatom ecological traits (guilds) in paleoecological reconstruction were demonstrated in this paper. The main changes have been observed at ca. 10,670–9000, 6500 and 3100 cal yr BP in geochemistry, vegetation and siliceous algal assemblages. Catchment soil stabilization was apparent from ∼9000 cal yr BP onwards, in-lake and terrestrial productivity was the highest between 9000 and 6500 cal yr BP and human impact became the dominant driver in both terrestrial vegetation and sediment geochemical changes and in-lake processes over the last ∼3400 years in both lakes. The geochemical record displayed frequent erosional events within the Holocene. The strongest soil erosions clustered around 6500–7400 and 3200-900 cal yr BP.

Paleolimnological studies in Russian northern Eurasia: A review

This article presents a review of the current data on the level of paleolimnological knowledge about lakes in the Russian part of the northern Eurasia. The results of investigation of the northwestern European part of Russia as the best paleolimnologically studied sector of the Russian north is presented in detail. The conditions of lacustrine sedimentation at the boundary between the Late Pleistocene and Holocene and the role of different external factors in formation of their chemical composition, including active volcanic activity and possible large meteorite impacts, are also discussed. The results of major paleoclimatic and paleoecological reconstructions in northern Siberia are presented. Particular attention is given to the databases of abiotic and biotic parameters of lake ecosystems as an important basis for quantitative reconstructions of climatic and ecological changes in the Late Pleistocene and Holocene. Keywords: paleolimnology, lakes, bottom sediments, northern

Lost in dating – Problems with the absolute chronologies and sedimentation rates of Late Glacial and Early Holocene oxbow lake deposits in Central Europe

Abstract This article presents potential errors related to the construction of absolute chronologies for Late Glacial and Early Holocene sediments accumulated in oxbow lakes in Central Europe and their influence on palaeoecological reconstruction. Our study is based on two sediment cores: (i) from the San River (Stubno-Naklo site in south-eastern Poland; S-N) and (ii) from the Dniester River (Luka site in western Ukraine) valleys. Accelerator mass spectrometry (AMS) 14C dating was performed on terrestrial plant macrofossils from each site to produce Bayesian age–depth models and to calculate sedimentation rates (SRs). The SR in both sites was characterised by high variability reflecting the developmental stage of oxbow lake. The highest SR values (1.18–1.23 cm yr-1) were identified at the S-N site at the beginning of the Holocene (ca. 11,550–11,470 cal. BP) and related to enhanced overbank deposition. The lowest SR values (0.01–0.02 cm yr-1) were identified in the transitional layer between the Younger Dryas and the Preboreal chronozone (ca. 11,810–11,160 cal. BP) in the Luka profile; this may have been related to the sedimentary gap(s) caused by falls in the water table and/or temporary desiccation of the water body. Moreover, our study revealed the presence of three distinctly aged AMS 14C dates in the Younger Dryas section of the Luka profile. These radiocarbon inversions were completely undetected by pollen analysis, which indicated the domination of Pinus and Betula without any significant fluctuations throughout the entire subsection. The presence of such ‘cryptic’ insertions of older material could lead to erroneous palaeoenvironmental reconstruction. Similarly the S-N site revealed anomalously ‘aged’ dates which were also difficult to detect by pollen analysis.

PALEOSOLS AND ICHNOFOSSILS OF THE UPPER PENNSYLVANIAN–LOWER PERMIAN MONONGAHELA AND DUNKARD GROUPS (OHIO, USA): A MULTI-PROXY APPROACH TO UNRAVELING COMPLEX VARIABILITY IN ANCIENT TERRESTRIAL LANDSCAPES

The upper Monongahela and lower Dunkard groups of southeastern Ohio include abundant paleosols containing ichnofossils as well as vertebrate, invertebrate, and plant body fossils. These paleosols formed on diverse Late Pennsylvanian to Early Permian landscapes in an alluvial setting. This study investigated small-scale lateral and vertical variability of the paleosols that formed at the distal edge of the Dunkard Basin. Three detailed, 32-m thick stratigraphic sections across a 70 m outcrop were measured in eastern Athens County, Ohio. Seven pedotypes representing soil formation in nine subenvironments were identified through bulk geochemical, clay mineralogical, and petrographic analyses as well as a detailed study of the ichnofossils, body fossils, and macromorphological paleosol properties. Ichnofossils were abundant and included rhizoliths, actively to passively filled burrows, and coprolites. These ichnofossils were produced by various plants, larval and adult arthropods, and micro- to macro-vertebrates. Body fossils within the paleosols included micro- and macro bone fragments and teeth, compression plant fossils, ostracodes, and gastropods. Vertical transitions among the subenvironments were due to both fluvial channel migration and climatic changes. Precipitation was seasonally distributed with a range of mean annual precipitation (MAP) from 300–1000 mm/yr through the section. This study demonstrates that by investigating the small-scale lateral and vertical variations in paleosols, finer resolution paleoclimatic, paleoenvironmental, and paleoecological reconstructions are possible.

Short-term response of testate amoebae to wildfire

Many peatlands are exposed to intermittent burning but the implications of this burning for microbial communities have been little-studied. Here we consider the impacts of burning on the dominant protists of peatland ecosystems, the testate amoebae. To do this we used a ‘natural experiment’, a peatland exposed to wildfire where fire-fighting activity left a combination of unburned and heavily burned areas in close proximity. We assessed the change in testate amoebae three days after the end of the fire. We find that burning led to a large change in taxon composition, primarily noted by a shift from taxa with tests constructed of idiosomes to those constructed of xenosomes. The most likely explanation for this change is the direct destruction of mostly idiosome tests by extreme heat. Although we did not differentiate live individuals from empty tests it is probable that the fire led to a significant change in the testate amoeba community. This change may have interesting implications for the structure of microbial food webs, for biogenic silica cycling and for palaeoecological reconstruction in burned peatlands. This is clearly a topic which deserves more research attention.

Environmental history and vegetation dynamics in response to climate variations and human pressure during the Holocene in Bassa Nera, Central Pyrenees

With the aims of investigating the causes of environmental changes in high mountain ecosystems during the Holocene in relation to climate forcings and identifying thresholds for vegetation community shifts, we performed a multi-proxy palaeoecological reconstruction based on two sediment cores from Bassa Nera, a lentic system located close to the montane–subalpine ecotone in the Central Pyrenees. Using pollen, plant macroremains, charcoal, chemical elements and loss-on-ignition at centennial to decadal resolution, we reconstructed the vegetation and lacustrine dynamics during the last 10,000years. A montane pollen ratio was used as a palaeoecological indicator to track altitudinal shifts in high mountain vegetation, which was compared to the ice-rafted debris index (IRD) as a proxy for summarizing the climatic influence of the North Atlantic Circulation. Our results show upward shifts of deciduous forest and its presence in Bassa Nera from the onset of the Holocene until 4200calyrBP, when it was replaced by coniferous taxa. The montane ratio showed a link between vegetation and North Atlantic influence, while changes in Sphagnum macroremains and aquatic taxa allowed description of local ontogenic changes from the initial pond to the present peatland. The loss-on-ignition record showed some flood events at Bassa Nera between 4500 and 3900calyrBP. The studied proxies allowed inferences concerning anthropic pressure in the catchment through grazing activities by 7300calyrBP and the appearance of cereal agriculture around 5190calyrBP. The highest human pressure occurred in the late Bronze Age, Roman Period and Middle Ages.

Mesowear study of ungulates from the early Pleistocene site of ‘Ubeidiya (Israel) and the implications for early Homo dispersal from Africa

An ongoing question in Anthropology and Archaeology focuses on the role of climate change in human evolution and particularly in the dispersal of hominins out of Africa. One of the main hypothesis posits that early Pleistocene sites were open grassland habitats and that early Homo differentially inhabited such environments. Testing the environmental hypothesis requires robust paleoecological reconstructions of early Pleistocene ‘Out of Africa' sites. The early Pleistocene site of ‘Ubeidiya, central Jordan Valley, Israel, provides an excellent case study to test hypotheses regarding the role of climate in the dispersal of early Homo from Africa to Eurasia.Mesowear is a paleo-dietary proxy that measures facet development on selenodont ungulate molars. We analyzed the mesowear of five ‘Ubeidiya ungulate taxa averaged over all strata, then we analyzed the two ungulate taxa that had a large enough sample size for diachronic analysis: Equus tabeti and Dama sp. In both analyses, we used mesowear scores to predict percent grass in diet and precipitation in the habitat across a suite of modern taxa. We then use a phylogenetic generalized least squares (PGLS) framework to estimate these variables from the mesowear scores of the fossil taxa in ‘Ubeidiya. Phylogenetically-informed discriminant analysis (pFDA) was utilized to test the dietary categorical group identities of fossil specimens.Results suggests that percent graze in diet was lower in fossil taxa than in their modern counterparts while average precipitation was higher in the early Pleistocene than in the modern day locality of ‘Ubeidiya suggesting that overall ‘Ubeidiya was more humid with a close woodland forest that today.Results do not support the notion that ‘Ubeidiya was an open grassland habitat during the early Pleistocene and hominins did not preferentially occupy such environments. Thus it the adaptability of Homo to novel habitats out of Africa lend support to the climate variability hypothesis.

Effects of the Hekla 4 tephra on vegetation in Northwest Iceland

Vegetation plays a key role in preventing the remobilisation of tephra and aeolian activity following tephra fall. Recent volcanic eruptions in Iceland have highlighted the consequences of tephra fall for ecosystems and human health. Improved understanding of the mechanisms behind ecosystem recovery following tephra fall is particularly important for Iceland. Today ~42% of the country is classified as desert and unvegetated and sparsely vegetated areas are unable to trap tephra fall and prevent subsequent wind erosion. This paper presents palaeoenvironmental reconstructions before and after the Hekla 4 tephra from two lakes in Northwest Iceland, from within a woodland in the lowland, and in open woodland under stress at the highland margin. The c. 4,200 cal bp. Hekla 4 tephra is one of the most extensive Icelandic Holocene tephra layers and the eruption produced an estimated ~9 km3 of tephra. The palaeoecological reconstructions provide an insight into the responses of two relatively stable ecosystems to thick tephra deposits during a period of cooling climate. The understory vegetation in the lowland woodland was buried by the tephra, however Betula pubescens trees were not severely affected and the woodland recovered relatively quickly. In contrast, open woodland at the highland margin that was already at its ecological limit, shifted to dwarf shrub heath, a more resilient vegetation community in response to the tephra fall and cooling climate.

Isotaphonomy in concept and practice: an exploration of vertebrate microfossil bonebeds in the Upper Cretaceous (Campanian) Judith River Formation, north-central Montana

AbstractVertebrate microfossil bonebeds (VMBs)—localized concentrations of small resilient vertebrate hard parts—are commonly studied to recover otherwise rarely found small-bodied taxa, and to document relative taxonomic abundance and species richness in ancient vertebrate communities. Analyses of taphonomic comparability among VMBs have often found significant differences in size and shape distributions, and thus considered them to be non-isotaphonomic. Such outcomes of “strict” statistical tests of isotaphonomy suggest discouraging limits on the potential for broad, comparative paleoecological reconstruction using VMBs. Yet it is not surprising that sensitive statistical tests highlight variations among VMB sites, especially given the general lack of clarity with regard to the definition of “strict” isotaphonomic comparability. We rigorously sampled and compared six VMB localities representing two distinct paleoenvironments (channel and pond/lake) of the Upper Cretaceous Judith River Formation to evaluate biases related to sampling strategies and depositional context. Few defining distinctions in bioclast size and shape are evident in surface collections, and most site-to-site comparisons of sieved collections are indistinguishable (p≤0.003). These results provide a strong case for taphonomic equivalence among the majority of Judith River VMBs, and bode well for future studies of paleoecology, particularly in relation to investigations of faunal membership and community structure in Late Cretaceous wetland ecosystems. The taphonomic comparability of pond/lake and channel-hosted VMBs in the Judith River Formation is also consistent with a formative model that contends that channel-hosted VMBs were reworked from pre-existing pond/lake assemblages, and thus share taphonomic history.

Exploring the diversity and ecology of testate amoebae in West Siberian peatlands

Testate amoebae are valued for their functional significance and application as indicators of environmental conditions, particularly in peatland ecosystems. Research on testate amoebae has increased dramatically in recent years but there are still large parts of the world which have seen very little research. Here we consider testate amoeba communities of the West Siberian Lowland, the world’s largest peatland region and therefore one of the largest potential habitats for testate amoebae. Extensive sampling identified 89 taxa and showed that testate amoeba communities are structured by their physical and biological environment. We identified significant relationships between amoeba communities and both moisture content and vegetation composition. Despite the assemblages containing many widely-distributed species, some taxa considered typical of peatlands (e.g. Archerella flavum and Hyalosphenia papilio) were comparatively rare or absent, paralleling findings further south in Asia. We suggest that testate amoebae in this region deserve further study and may have useful applications in palaeoecological reconstruction and as bioindicators of the impacts of oil and gas extraction.

Notes to the use of Aulacoseira taxa in the palaeoecological reconstruction of the Bohemian Forest lakes

Notes to the use of Aulacoseira taxa in the palaeoecological reconstruction of the Bohemian Forest lakes

Subfossil Cladocera as a powerful tool for paleoecological reconstruction

Subfossil Cladocera (Crustacea, Branchiopoda) represent one of the most valuable biological proxies preserved in lake sediments that can be studied for reconstruction purposes. They are widespread in both the pelagic and littoral zones of lakes of different geographical distribution, altitude and typology, where they often represent the dominant component of zooplankton in terms of biomass. The chitinous parts of their body are well preserved in lake sediments, and the taphonomic taxonomy is well established, thanks to the numerous studies that followed the first pioneer works by Frey (1960).

An alternative approach to transfer functions? Testing the performance of a functional trait-based model for testate amoebae

Transfer functions are now widely available to infer past environmental conditions from biotic assemblages. Existing transfer functions are based on species assemblages but an alternative is to characterize assemblages based on functional traits, characteristics of the organism which determine its fitness and performance. Here, we test the potential of trait-based transfer functions using testate amoeba functional traits to reconstruct peatland water-table depths.A total of seven functional traits with linkages to peat moisture content were identified and quantified as community weighted-means for each of 43 taxa in a training set from Tierra del Fuego, South America. Transfer functions based on (multiple) linear regression and partial least-squares were produced, validated using cross-validation and an independent test set, and applied to three core records. Trait-based models performed remarkably well. Model performance based on cross-validation and an independent test set was only marginally weaker than for models based on species and reconstructed down-core trends were extremely similar. Trait-based models offer considerable potential for paleoecological reconstruction particularly in no-analogue situations, where no species transfer function is available and for inexperienced analysts. The approach deserves further validation and testing for both testate amoebae and other groups of microfossils.

A new hesperornithiform (Aves) specimen from the Late Cretaceous Canadian High Arctic with comments on high-latitude hesperornithiform diet

Here we describe a new hesperornithiform specimen from the Upper Cretaceous Kanguk Formation of Devon Island, Nunavut, Canada. This specimen (NUVF 286) is referred to cf. Hesperornis sp. based on size and shape of femora and teeth preserved with other skeletal elements. Previous osteohistologic analyses indicate a subadult ontogenetic stage at the time of death. This new cf. Hesperornis specimen includes the first teeth associated with a high-latitude hesperornithiform, allowing for comments on the trophic behavior of these birds. Paleoecological reconstructions based on current knowledge of polar assemblages and comparisons to modern birds suggest that high-latitude hesperornithiform birds may have had more varied diets than previously assumed.