Reconstruction Of Past Vegetation Research Articles

Revealing the palaeoecology of silent taxa: selecting proxy species from associations in modern vegetation data

AbstractAimSpecies severely under‐represented in fossil pollen records leave gaps in interpretations and reconstructions of past vegetation. These ‘silent taxa’ leave little or no trace due to low pollen production, dispersal, preservation and taxonomic resolution. An approach for including them is through associating them with other species with reliable pollen representation. Here, we demonstrate a method for selecting such a proxy species for the Holocene using modern vegetation data.LocationNew Zealand.TaxonBeilschmiedia tawa (A.Cunn.) Benth. & Hook. F. ex Kirk (Lauraceae).MethodsWe used vegetation plot data to perform a pairwise co‐occurrence analysis of the New Zealand indigenous forest metacommunity to identify species with a strong positive association with Beilschmiedia tawa (tawa), a common tree severely under‐recorded in the pollen record. For those species, we then modelled their realised climatic niches to identify species with high niche overlap. We discuss how well those species could be interpreted from the Holocene fossil pollen record based on the representation of their pollen taxa.ResultsKnightia excelsa (rewarewa; Proteaceae) is a potential proxy for B. tawa in Holocene fossil pollen records, and other, range‐limited species may provide community‐specific proxies. We show combining resampling with sub‐sampling is a robust method for reducing the high false positive rate associated with large co‐occurrence analyses (1000+ sites) by limiting the sample size to 100 sites.Main ConclusionsWe show that the palaeoecology of silent taxa can be studied via proxy species, allowing their past distributions to be better understood. We highlight the importance of modelling many aspects of the realised niche to understand the usefulness and limitations of the silent–proxy association. Future research should focus on testing the underlying assumptions of the silent–proxy relationship so that models built on modern data can confidently be applied to palaeoecological data.

Modern pollen assemblages from the hinterland of the Tibetan Plateau and their significance for reconstructions of past vegetation

We conducted a detailed field vegetation investigation combined with the collection of surface soil samples for pollen analysis in the alpine meadow and steppe vegetation zones (30 sites in each zone) in the hinterland of the Tibetan Plateau. Our objectives were to determine the source area of exotic pollen, the relationship between pollen percentages and the cover of the major plant taxa, and the characteristics of the pollen assemblages from surface soils and lake sediments and their vegetation significance. Our principal findings are: (i) the two vegetation zones are herbaceous although arboreal pollen types are present in the related pollen assemblages (2 and 16.8% in the alpine meadow and steppe zones, respectively); (ii) arboreal pollen is assumed to be transported mainly by the Indian monsoon from the forests of the southern Himalayan foothills or river valleys – the spatial distribution of the percentages and concentrations of arboreal pollen in the study sites shows that pollen concentrations have the strongest correlation with the Indian monsoon's variations; (iii) there are regional differences in (a) the relationship between pollen percentages and the cover of the main plant taxa and (b) the indicator plant taxa representative of pollen assemblages and vegetation types zones – the regional vegetation of the study region and pollen productivity variations between plant taxa are likely to be the main causes behind these differences; and (iv) the pollen assemblages from surface soils and lake sediments have similar characteristics and correspond well to the regional vegetation of the alpine meadow zone. In the alpine steppe zone, the pollen assemblages from surface soils and lake sediments are quite different, caused mainly by the over‐representation of Artemisia. Our study supplies a detailed description of pollen–vegetation relationships on the hinterland of the Tibetan Plateau and provides scientific references for interpreting stratigraphic pollen assemblages and reconstructing regional vegetation.

Late Holocene riparian vegetation dynamics, environmental changes, and human impact in the Harapan forest of Sumatra, Indonesia

Riparian wetland ecosystems provide important ecological services but are also vulnerable to climate change and human activities. To understand the influence of natural factors (e.g. climate change, flooding, drought) and human activities (e.g. agriculture) as well as to support management strategies, reconstructions of past vegetation and environmental changes are needed. To achieve this, we conducted a multi-proxy paleoecological analysis, including pollen and spores, macro-charcoal and radiocarbon dating, on a sediment core taken from a riparian area in the Harapan forest of Sumatra. Three distinct periods were identified: i) AD 1100 – 1400: Upland and swamp forest with riparian and herbaceous vegetation, possibly part of a riparian buffer zone (e.g. riverbank), was present in the study area under a stronger dry season regime; ii) AD 1400 – 1870: freshwater swamps expanded to the study site; iii) later, from AD 1870 to present, upland forests dominated in the study area with a strong dry season. The presence of cereal cultivation from AD 1300 – 1450, and oil palm (Elaeis guineensis) since the mid-19th century AD indicates the presence of small-scale agriculture in the study area. This study of riparian vegetation dynamics and environmental changes in the Harapan forest of Sumatra shows the development from a riparian forest to a freshwater swamp and upland forest under the impact of climate change and human activities.

Spatially explicit, quantitative reconstruction of past vegetation based on pollen or charcoal data as a tool for autecology of trees

ContextThe determination of autecological preferences based on long-term vegetation dynamics is hampered by the lack of realistic estimates for past occurrence and abundance patterns. Palaeoecological record has still rather character of points than spatially continuous maps.ObjectivesTo infer long-term autecological preferences of trees from reconstructed vegetation. Compare reconstructions based on pollen and charcoals.MethodsWe employed to the regional training set of 58 sites the Extended Downscaling Approach (EDA) using nine topographic factors clustered in 8 habitat classes, data on pollen productivity estimates, fossil pollen, charcoal sequences from soil and archaeological contexts. Based on abundances and habitat preferences from the last 9 millennia, we calculated the autecological preferences of tree taxa, using multivariate statistics.ResultsThe significant spatiotemporal patterns between soil-charcoal and pollen-based EDA validated the reconstruction, the use of both records in the EDA, and the EDA model. One of the topographic indices—vertical distance to channel network—evidenced the following: the closest taxon to the groundwater is Picea; Abies, Betula, Pinus and Quercus have intermediate distances; Fagus grows far from the channel network and Corylus even further.ConclusionsThe EDA model linked past forest composition to realistic topography. Such a spatially explicit reconstruction produced by our new algorithm allows inferring the relationship between past plant communities and environmental variables. The long-term preferences of tree species to habitat characteristics match their current autecological demands. This might be a breakthrough in quantitative plant paleoecology.

Spatially explicit, quantitative reconstruction of past vegetation based on pollen or charcoal data as a tool for autecology of trees

Spatially explicit, quantitative reconstruction of past vegetation based on pollen or charcoal data as a tool for autecology of trees

Climate and fire drivers of forest composition and openness in the Changbai Mountains since the Late Glacial

Ongoing climate changes have a direct impact on forest growth; they also affect natural fire regimes, with further implications for forest composition. Understanding of how these will affect forests on decadal-to-centennial timescales is limited. Here we use reconstructions of past vegetation, fire regimes and climate during the Holocene to examine the relative importance of changes in climate and fire regimes for the abundance of key tree species in northeastern China. We reconstructed vegetation changes and fire regimes based on pollen and charcoal records from Gushantun peatland. We then used generalized linear modelling to investigate the impact of reconstructed changes in summer temperature, annual precipitation, background levels of fire, fire frequency and fire magnitude to identify the drivers of decadal-to-centennial changes in forest openness and composition. Changes in climate and fire regimes have independent impacts on the abundance of the key tree taxa. Climate variables are generally more important than fire variables in determining the abundance of individual taxa. Precipitation is the only determinant of forest openness, but summer temperature is more important than precipitation for individual tree taxa with warmer summers causing a decrease in cold-tolerant conifers and an increase in warmth-demanding broadleaved trees. Both background level and fire frequency have negative relationships with the abundance of most tree taxa; only Pinus increases as fire frequency increases. The magnitude of individual fires does not have a significant impact on species abundance on this timescale. Both climate and fire regime characteristics must be considered to understand changes in forest composition on the decadal-to-centennial timescale. There are differences, both in sign and magnitude, in the response of individual tree species to individual drivers.

Modern pollen–vegetation relationships along an altitudinal transect in the Western Higher Himalaya, India: Palaeoclimatic and anthropogenic implications

Palynology is one of the most reliable tools for the reconstruction of past vegetation and climate and modern pollen analogues are important for the calibration of fossil pollen assemblages. The present study analyses the pollen–vegetation relationships along a steep altitudinal gradient (2700–3680 m), in the western Higher Himalayan region. On the basis of altitude, three vegetation zones were demarcated: Zone I (2700–3100 m) is composed of mixed-temperate forest vegetation, dominated by Quercus semecarpifolia and Rhododendron arboreum; Zone II (3100–3250 m) is marked by sub-alpine forest vegetation, characterised by R. campanulatum and R. barbatum, along with Abies spectabilis and Q. semecarpifolia; Zone III (3250–3680 m) is above the tree-line (3250 m) and represented by alpine-scrub and meadows. Thirty-five surface soil samples (twenty, seven and eight from each zone, respectively) were analysed along the altitudinal transect to decode the representation of the extant vegetation in the pollen-rain. The pollen–vegetation relationship is non-linear due to the over-representation of extra-local Pinus pollen in each zone. Nonetheless, the modern pollen assemblages show a general correlation with the local broad-leaved taxa and the herbaceous elements; with the exception of Rhododendron pollen, which is under-represented. Among the non-pollen palynomorphs (NPPs), the presence of coprophilous fungal spores is compatible with the grazing activities in the area. Multivariate statistical analyses performed on the surface pollen data indicate that the dataset can efficiently distinguish the different vegetation zones across the altitudinal gradient. This work provides the modern analogues for pollen-based palaeoclimatic reconstructions for the Western-Higher Himalayan region, and would also help to decipher the inception and intensification of anthropogenic activities in the region.

A modern pollen data set for the forest–meadow–steppe ecotone from the Tibetan Plateau and its potential use in past vegetation reconstruction

The relationship between modern pollen and vegetation provides the basis for the interpretation of stratigraphic pollen assemblages and the quantitative reconstruction of past vegetation. We selected 168 topsoil samples from four different vegetation types on the south‐eastern Tibetan Plateau to explore the relationships between pollen assemblages, vegetation and climate. The results reveal that pollen assemblages discriminate the vegetation types well; the subalpine coniferous and evergreen broad‐leaved forest is characterized by a high proportion of arboreal taxa (e.g. Pinus, Picea, Betula); the alpine shrub and meadow and alpine steppe vegetation types are dominated by Cyperaceae, followed by Artemisia and Brassicaceae; and the alpine steppe‐shrub is characterized by a high percentage of Artemisia, with Cyperaceae, Asteraceae and Brassicaceae as common taxa. Redundancy analysis shows that mean temperature of the coldest month (Mtco) is the main climatic factor that influences pollen distribution. Pollen diversity indices (including richness and evenness) gradually decrease from SE to NW. The random forest classification has good performance in distinguishing vegetation types. Our study supplies a comparatively detailed description of the relationship between the pollen assemblage and vegetation in the forest–meadow–steppe ecotone on the south‐eastern Tibetan Plateau. In addition, the random forest model has potential application for reconstructing the past vegetation type of the fossil pollen spectra on the south‐eastern Tibetan Plateau.

Estimation of pollen productivity and dispersal: How pollen assemblages in small lakes represent vegetation

AbstractQuantitative understanding of vegetation dynamics over timespans beyond a century remains limited. In this regard, the pollen‐based reconstruction of past vegetation enables unique research opportunities by quantifying changes in plant community compositions during hundreds to thousands of years. Critically, the methodological basis for most reconstruction approaches rests upon estimates of pollen productivity and dispersal. Previous studies, however, have reached contrasting conclusions concerning these estimates, which may be perceived to challenge the applicability and reliability of pollen‐based reconstruction. Here we show that conflicting estimates of pollen production and dispersal are, at least in part, artifacts of fixed assumptions of pollen dispersal and insufficient spatial resolution of vegetation data surrounding the pollen‐collecting lake. We implemented a Bayesian statistical model that related pollen assemblages in surface sediments of 33 small lakes (<2 ha) in the northeastern United States, with surrounding vegetation ranging from 101 to >105 m from the lake margin. Our analysis revealed three key insights. First, pollen productivity is largely conserved within taxa and across forest types. Second, when local (within a 1‐km radius) vegetation abundances are not considered, pollen‐source areas may be overestimated for some common taxa (Cupressaceae, Pinus, Quercus, and Tsuga). Third, pollen dispersal mechanisms may differ between local and regional scales; this is missed by pollen‐dispersal models used in previous studies. These findings highlight the complex interactions between vegetation heterogeneity on the landscape and pollen dispersal. We suggest that, when estimating pollen productivity and dispersal, both detailed local and extended regional vegetation must be taken into account. Also, both deductive (mechanistic models) and inductive (statistical models) approaches are needed to better understand the emergent properties of pollen dispersal in heterogeneous landscapes.

Influence of plant coverage and environmental variables on pollen productivities: evidence from northern China

Pollen productivity is a critical parameter in the interpretation of pollen-vegetation relationships, and in the quantitative reconstructions of past vegetation from fossil pollen records. One-year monitoring records were collected for 143 pollen traps in various parts of northern China, together with modern vegetation data. Absolute Pollen Productivity Estimates (APPE) were calculated for 11 taxa using the ratio of pollen influx to plant coverage at each applicable sampling site, in which the plants of the target taxon were present. Relative Pollen Productivity Estimates (RPPE) were calculated for the 11 taxa (taking Poaceae as the reference taxon) at those sites in which each taxon occurred together with Poaceae. Artemisia and Chenopodiaceae were found to have the highest RPPEs and the largest RPPEs ranges, while Pinus and Quercus also had higher RPPEs than Poaceae; Abies, Betula, Larix, Picea and Cyperaceae had relatively low RPPEs. Variations in RPPE between different areas may be explained by variations in climatic conditions, plant coverage and land use practices which might influence plant growing situation. Marked effect that variations in pollen productivity can have on vegetation reconstructions was demonstrated by applying these distinct RPPEs to reconstructions of Holocene vegetation in the Lake Daihai area (northern China), such as a large range of RPPE produces a large range of plant coverage. Variations in RPPEs within a single taxon, related to vegetation coverage and climatic conditions, therefore need to be considered in future vegetation reconstructions.

Potential in paleoclimate reconstruction of modern pollen assemblages from natural and human-induced vegetation along the Heilongjiang River basin, NE China

The relationships among modern pollen, vegetation, climate and human activities can help improving the reliability of reconstruction of past vegetation, regional climate and human activities based on fossil pollen records. We used a dataset of 114 surface soil pollen samples from natural vegetation (wetlands, forests and grasslands) and human-induced vegetation (farmlands and residences) along the Heilongjiang River basin in northeast China to explore the relationships among modern pollen, vegetation, climate and human activities. The results indicated that surface pollen assemblages differentiated modern vegetation well in natural and human-induced vegetation types. The wetlands were mainly composed of Cyperaceae, along with Artemisia, weeds Poaceae (<35 μm) and Sanguisorba. The forests were predominated by Pinus and Betula. Artemisia, weeds Poaceae (<35 μm) and Chenopodiaceae were the most important pollen taxa in grasslands. The farmlands were characterized by Artemisia, Aster, Chenopodiaceae, cereal Poaceae (>35 μm) and Taraxacum. The pollen assemblages of residences were composed of weeds Poaceae (<35 μm), Chenopodiaceae and Salix. Ordination analyses based on main pollen taxa and climatic variables were used to determine the relationships between pollen and climate, suggesting the surface pollen assemblages were primarily influenced by the mean annual temperature (Tann) in northeast China. The statistical performance of transfer function between pollen and Tann were well indicating the modern pollen assemblages could be reliably used in paleoclimate reconstruction in our study area. Furthermore, human-induced vegetation had high frequencies of human-companion pollen taxa, such as Chenopodiaceae, Aster, Taraxacum and cereal Poaceae (>35 μm). Pollen concentrations of human-induced vegetation were lower than natural vegetation types, which could be used as an indicator of human influence intensity.

Reply to Theuerkauf and Couwenberg (2020) comment on: “Pollen-based reconstruction of Holocene land-cover in mountain regions: Evaluation of the Landscape Reconstruction Algorithm in the Vicdessos valley, northern Pyrenees, France”

Comments on Marquer et al. (2020) by Theuerkauf and Couwenberg (2020) revisit two issues important for pollen-based reconstruction of past vegetation with the Landscape Reconstruction Algorithm (LRA;Sugita, 2007a,2007b) and related models: the selection of pollen dispersal model and the appropriate use of pollen productivity estimates. We are aware of those issues, and our paper addresses those questions and advises for caution and necessary future steps to improve model-based reconstruction of vegetation in mountain environments and elsewhere. This reply restates briefly some of the important take-home messages fromour study and presents our suggestion and proposal in response toTheuerkauf and Couwenberg’s comments.

Representation of modern pollen assemblage to vertical variations of vegetation and climate in the Yadong area, eastern Himalaya

The presence of arboreal pollen grains in pollen assemblages collected from alpine meadow and steppe sites in the central Tibetan Plateau affects the reliability of pollen-based investigations of past vegetation and climate conditions, but their origin remains uncertain. In this study, we present a 39-sample modern pollen dataset from the Yadong area on the southern slope of the Himalayas and investigate the relationships between pollen assemblages and the vertical variations in vegetation and climate and the upward transport of arboreal pollen. Our results reveal that surface soil pollen assemblages were influenced heavily by local vegetation components; however, their variations along the elevation gradient generally reflect vertical variations in vegetation and climate. For instance, arboreal pollen abundances were high at low-elevation sites, whereas herbaceous pollen abundances were high at cold and dry sites. Arboreal pollen grains (dominantly Pinus, Betula and Picea) can be transported by wind to unforested areas, and the southern slope of the Himalayas is likely a source of the arboreal pollen grains in alpine meadows and alpine steppes in the central Tibetan Plateau. Thus the arboreal pollen grains should be treated with caution in the reconstructions of past vegetation and climate in the central Tibetan Plateau.

Palaeovegetational evolution of the Çankırı-Çorum Basin during the Mio-Pliocene (Central Anatolia) based on the IPR analysis method

Reconstruction of past vegetation and climates in the Cankiri-Corum Basin, one of the largest basins of Central Anatolia, is important for understanding the regional palaeovegetation. In this study, the palaeovegetational and palaeoclimatic proxies of the basin within the late middle Miocene and early Pleistocene interval are presented using the Integrated Plant Record (IPR) vegetation analysis and the coexistence approach (CA). The IPR analysis allows the reconstruction of six types of zonal vegetation: broad-leaved deciduous forests (BLDF), mixed mesophytic forests (MMF), broad-leaved evergreen forests (BLEF), xeric open woodlands and xeric grasslands or steppes, all identified from the microfloras of Cankiri-Corum Basin. During the late middle Miocene, warm temperate and humid climatic conditions prevailed and the palaeovegetation in the Cankiri-Corum Basin was represented by BLEF and an ecotone between MMF and BLEF. The cooling from the late middle Miocene to early late Miocene had begun as well, as low precipitation periods in the climatic conditions during the same time interval were recorded in the basin. Presumably, the proportion of broad-leaved deciduous elements remained balanced because the palaeotopography did not change significantly during the late Miocene in the Cankiri-Corum Basin. The recorded cooling could be related to a global climatic change from the middle to late Miocene. During the Tortonian to Messinian transition, the palaeovegetation type was represented by BLDF and suggests a continuous cooling trend in the basin. The palaeovegetation types of the late late Miocene comprise MMF in the northern part of the Cankiri-Corum Basin and xeric grassland or steppe in the southern part of the basin. Warm and dry climatic conditions were recorded from the Tortonian to the Messinian; these warm conditions during the Messinian could be correlated to the Messinian salinity crisis. According to the IPR analysis results, the northern part of the Cankiri-Corum Basin palaeotopography seems to be higher in altitude than the southern part. Palaeovegetation types in the latest late Miocene and early Pliocene were characterised by MMF and an ecotone between BLDF and MMF in the northern part of the Cankiri-Corum Basin and open woodland vegetation in the southern part of the basin. The percentage of the broad-leaved deciduous component from the latest late Miocene and early Pliocene decreases in the Cankiri-Corum Basin, which could be related to beginning uplift starting changes in the palaeotopography. In the early Pliocene, this uplift was continued in the basin.

Vegetation changes in the Hotyn Upland over the last 2000 years (based on pollen data)

Pollen study of two soil sections, located in two different relief positions (the gully bottom at Sadgora 1 and the upper part of a slope at Ridkivtsi I) enables us to show vegetational and climatic changes in the Bukovyna area (the Chernivtsi region) during the last 2000 years (the end of the Early Subatlantic, the Middle and Late Subatlantic). The reconstructions of past vegetation are based on the analyses of pollen surface samples, taken from the soils of different ecotops in the sites’ vicinity. The reconstructed short-period phases of environmental change correspond well with those established in other areas. These are the end of the “Roman warm period” (before the 14C date of 1.74 ka BP), with the humid climate; the relatively dry “Dark Ages cool period” (before the 14C date of 1.19 ka BP); the wet “Medieval warm period”; the cool “Little Ice Age” (with its wetter beginning and drier ending) and the modern warm phase (the last 150 years).Centennial environmental changes − the cooling within the Medieval Warming (XI cent.) and the warming within the “Little Ice Age” (XV cent.) – have been detected. Human impact on the vegetation can be demonstrated – forest clearance (with the presence of particles of microscopic charcoal and pollen of pyrophitic plants), the introduction of thermophilous walnut during warm periods, and the appearance of pasture lands in the place of former fern patches and woods during the “Little Ice Age”, and the last warm phase (with the presence of pollen of pastoral synanthropic plants). In the last 2000 years, broad-leaved woodland, dominated by hornbeam, grew extensively near Sadgora and Ridkivtsi only during the “Medieval Warm Period”.

Intermittent development of forest corridors in northeastern Brazil during the last deglaciation: Climatic and ecologic evidence

The semi-arid northeastern (NE) Brazil vegetation is largely dominated by Caatinga, one of the largest and richest dry forests in the world. Caatinga is a strategic biome, since it has borders with Cerrado, Atlantic forests and the Amazon, acting as a potential corridor (or barrier) for biotic interchange between these regions during evolutionary times. Therefore, accurate reconstructions of past vegetation, ecological and hydrological changes in this area are critical to understanding the dynamics of biome boundaries that may play an important role in dispersal and diversification mechanisms and, more specifically, the link between the long-term climate variability and tropical biodiversity. Here, we present high-resolution palynological and elemental data from marine core GeoB16205-4 retrieved off the Parnaíba River mouth (NE Brazil) mainly covering the Younger Dryas (YD). We show that the YD interval was predominantly wet in NE Brazil, yet it was not homogenous and two distinct phases could be distinguished. A marked intensification of wet conditions between ∼12.3 and 11.6 cal kyr BP was recorded by the expansion of tropical rainforest and tree ferns. These results are in agreement with the transient TraCE-21k coupled climate model simulation. We infer that the second pluvial phase of the YD is related to a weak AMOC due to meltwater pulses in the North Atlantic, which forces a southward shift of the Intertropical Convergence Zone and its associated rainfall. Our records provide new evidence on the establishment of an “eastern forest corridor” in the nowadays semi-arid Caatinga allowing for past biotic interchanges of plant species.

Plant DNA metabarcoding of lake sediments: How does it represent the contemporary vegetation.

Metabarcoding of lake sediments have been shown to reveal current and past biodiversity, but little is known about the degree to which taxa growing in the vegetation are represented in environmental DNA (eDNA) records. We analysed composition of lake and catchment vegetation and vascular plant eDNA at 11 lakes in northern Norway. Out of 489 records of taxa growing within 2 m from the lake shore, 17–49% (mean 31%) of the identifiable taxa recorded were detected with eDNA. Of the 217 eDNA records of 47 plant taxa in the 11 lakes, 73% and 12% matched taxa recorded in vegetation surveys within 2 m and up to about 50 m away from the lakeshore, respectively, whereas 16% were not recorded in the vegetation surveys of the same lake. The latter include taxa likely overlooked in the vegetation surveys or growing outside the survey area. The percentages detected were 61, 47, 25, and 15 for dominant, common, scattered, and rare taxa, respectively. Similar numbers for aquatic plants were 88, 88, 33 and 62%, respectively. Detection rate and taxonomic resolution varied among plant families and functional groups with good detection of e.g. Ericaceae, Roseaceae, deciduous trees, ferns, club mosses and aquatics. The representation of terrestrial taxa in eDNA depends on both their distance from the sampling site and their abundance and is sufficient for recording vegetation types. For aquatic vegetation, eDNA may be comparable with, or even superior to, in-lake vegetation surveys and may therefore be used as an tool for biomonitoring. For reconstruction of terrestrial vegetation, technical improvements and more intensive sampling is needed to detect a higher proportion of rare taxa although DNA of some taxa may never reach the lake sediments due to taphonomical constrains. Nevertheless, eDNA performs similar to conventional methods of pollen and macrofossil analyses and may therefore be an important tool for reconstruction of past vegetation.

Using springbok (Antidorcas) dietary proxies to reconstruct inferred palaeovegetational changes over 2 million years in Southern Africa

The reconstruction of past vegetation and climatic conditions of the Cradle of Humankind, Gauteng Province, South Africa, has been approached using various proxies (such as micromammals, speleothems, faunal and floral presence and stable carbon isotopes). Elisabeth Vrba's seminal studies (1974; 1975) on the fossil record of this region indicated dramatic faunal turnover based on species extinction and speciation data. This turnover was thought to have been driven by increasing aridity and spreading grasslands. These reconstructions however, are continuously being refined and adapted in light of advancing techniques (such as dental microwear textural analysis) and terrestrial proxies, such as speleothems.However, more recent studies show varying proportions from wooded towards more grassland-dominated habitats, with the most common reconstruction being the heterogeneous ‘mosaic’ habitat. Here we re-evaluate the findings of a transition from woodland to grassland conditions in the fossil record from Member 4 Sterkfontein to Member 5 Sterkfontein and the deposits of Swartkrans. To approach the palaeovegetation changes through time via a different angle, we focus on the diet of the springbok (genus Antidorcas), represented throughout this temporal period from geological members dating from 2.8–0.8 Ma. We use detailed dietary methods (dental linear measurements, mesowear, microwear, and stable carbon isotope analysis) to explore past changes in diets of springbok that can be used to indicate the prevailing vegetation conditions. Our results presented here broadly agree with previous palaeoenvironmental reconstructions, in indicating increased grassland post ca 1.7 Ma, with some suggestion of more heterogeneous habitats for Swartkrans Member 2 (ca 1.65–1.07 Ma). We find that there is support for the implementation of a multi-disciplinary approach to produce more accurate and robust reconstructions of past diets and by extension, of palaeovegetation conditions, if the selected herbivore species is a mixed-feeder, like the springbok.

The roots of pollen analysis: the road to Lennart von Post

In 2016 the 100th birthday of palynology was celebrated: Lennart von Post introduced the scientific discipline in 1916 at lectures in Oslo and Stockholm. However, von Post was not the first to study pollen, and research dates back to the works of Nehemiah Grew and Marcello Malpighi in the late 17th century. Afterwards studies focussed mainly on the role of pollen for plant reproduction, and on pollen morphology. The first scientist who observed fossil pollen was Heinrich Goppert in 1836. However, it was not until the 1890s and 1900s that the study of pollen became a regular component in the reconstruction of past vegetation. Lennart von Post subsequently developed theoretical and practical concepts and methods of pollen analysis, and raised palynology from its infancy into the mature scientific discipline that flourished greatly during the century that followed.

Phytoliths as indicators of Quaternary vegetation at the Paleolithic site of Attirampakkam, India

The paleoecological context of hominin occupation in South Asia during the early and middle Pleistocene is virtually unknown. Attirampakkam, India, is an archeological site of global importance, with an early Acheulian occupation (age bracket of ~1.07–1.77Ma) succeeded by Middle Paleolithic levels. Here we report on the recovery of phytoliths from artifact-bearing Quaternary deposits in excavated trenches. We focus on the reconstruction of past vegetation during hominin occupation of the site. The present study provides information on hominin microenvironments and local habitats in South Asia, situating them in a more tangible ecological context than so far achieved. Results show that this region was arid during the earlier stages of the early Pleistocene, and was occupied by hominins living in a landscape locally lacking woody plants. Herbaceous vegetation was dominated by C4 Chloridoid grasses. In the later phase of the early Pleistocene, the landscape was wooded and dominated by C4 Panicoid grasses, with a significant reduction of C4 Chloridoid grasses indicating a shift from a drier to a relatively more humid climate. A diverse husk and leaf phytolith assemblage of wild Oryza spp. (rice) occurring as natural annual or perennial components of the vegetation in the area, other herbaceous plants such as Cyperaceae (sedges), and the continuous presence of blackened phytoliths, suggest the establishment a grassland landscape with enclaves of wetland habitat affected by seasonal flooding and frequent fires. The transition from the early to the middle Pleistocene was marked by a moderately humid climate, with a shift toward aridity during the late Pleistocene, during which we note an environment dominated by C4 Chloridoid grasses, by a sharp reduction of C4 Panicoid grasses, and by a rise in woody taxa. During the middle to late Pleistocene, Middle Paleolithic populations would have witnessed water bodies near the site, as reflected by the presence of plants adapted to swampier conditions such as Cyperaceae and Oryza spp. The archeological record terminates in Layer 1, when human occupation decreased drastically, possibly because of increased aridity and/or greater environmental variability. The phytolith fingerprint at ATM sheds light on the co-occurrence of, vegetation, fire and early prehistoric land occupation. An important aspect is the evidence of Oryza spp., suggesting that wild rice occurred in the environment frequented by these early hominins.