Vegetation Reconstruction Research Articles

Late Pleistocene-Holocene vegetation and climate variability of the western Himalaya, India

• Pollen, δ 13 C and TOC data revealed vegetation and climatic changes of western Himalaya during the last 15 ka. • Expansion of arboreals between 12.7 and 9.2 ka suggests a warm and humid environment . • A warm and humid climate from 7.8 to 5.2 ka represents the Holocene Climate Optima. • Vegetation expansion (decline) with enhanced (weaker) monsoon periods implies vegetation sensitivity to insolation driven ISM. Multiproxy analyses of sediment samples from a 2.7 m trench from western Himalaya have helped in the reconstruction of vegetation and climatic changes during the last ∼ 15.2 ka. The data revealed that between 15.2 and 12.7 ka, the region supported alpine–scrubs and trees interspersed with meadows in a cool and moderately humid climate. The lowest d 13 C values and coarse-grained sediment texture indicate improved hydroclimatic conditions. The expansion of arboreals between 12.7 and 9.2 ka also suggests a warm and humid climate. Despite this, slightly higher d 13 C values reflect decreasing hydrological conditions. Reduced arboreals and increased d 13 C values imply a cold and dry climate between ca. 9.2 and 7.8 ka. The proliferation of arboreals supports a warm and humid climate from 7.8 to 5.2 ka, representing the Holocene Climate Optima. However, between 5.2 and 3.7 ka, a decrease in arboreals with associated d 13 C values suggest climate deterioration. Based on changes in arboreals and non–arboreals, the Late Holocene phases advocate for warm and wet (ca. 3.7–2.3 ka), cool and dry (ca. 2.3–1.7 ka), and warm and wet (1.5–0.75 ka) climatic conditions, respectively. Since 0.75 ka, a modest increase in arboreals, TOC, and a decrease in d 13 C values, implying that hydroclimatic conditions have improved. These findings are broadly consistent with previous Himalayan palaeoclimatic reconstructions; nevertheless, the absence of any major shift in vegetation during the younger Dryas is surprising.

Impacts of plant and soil stoichiometry on species diversity in a desert ecosystem.

Plant and soil stoichiometric ratios can be used to explain changes in the structural and functional characteristics of plant communities. Exploring the relationships between the stoichiometric ratios and plant diversity is helpful to further elucidate the effects of soil and nutrient constraints on community vegetation. However, such studies remain poorly understood in desert ecosystems. In this study, we analysed the effects of soil moisture and salt content on soil and leaf stoichiometry, species diversity and their relationships in the desert ecosystem of the Ebinur Lake basin. The results showed that: (i) Compared with the low soil moisture and salinity (SW2) environment, the soil and leaf C, N, P contents and soil stoichiometric ratios were larger in the high soil moisture and salinity (SW1) environment, and the leaf stoichiometric ratios were smaller. (ii) In SW1 environment, species diversity was negatively correlated with soil C:N and C:P, but weakly correlated with soil stoichiometric ratios in SW2 environment. In addition, the relationships between it and leaf stoichiometric ratios were reversed in different moisture and salinity environments. (iii) Structural equation modelling showed that leaf C:P, C:N and soil C:P had strong effects on species diversity. This research aims to provide a scientific reference for maintaining plant diversity, vegetation reconstruction and ecosystem restoration in desert areas, and enrich the ecological stoichiometric theory of desert ecosystems.

Land Use Affects Soil Water Balance and Soil Desiccation within the Soil Profile: Evidence from the Western Loess Plateau Case

This study evaluated the properties of soil water dynamics and desiccation to a depth of 500 cm and tested the idea that land use affects soil drying in deep profiles. Four land use types were chosen: farmland, artificial forest and grassland, and abandoned land. Soil water content was most outstanding under long-term wheat fields, but average soil water content under artificial vegetation of Caragana korshinskii Kom. and alfalfa dropped to 6–8% within the 160–500 cm soil profile, very near to the 7.0% wilting point. Long-term continuous maize cultivation in a fully mulched ridge–furrow system significantly depleted soil water and resulted in a dried soil layer with a thickness of 240 cm. Short-term or long-term land abandonment enhanced soil reservoir and reduced soil water storage deficit degree compared to long-term maize and artificial vegetation. Soil water storage in the 160–500 cm soil profile was depleted by 240 and 464 mm under long-term maize and Caragana korshinskii Kom., respectively, by 267, 319, 381, and 463 mm under 5-, 10-, 20-, and 30-year alfalfa, and by −58, 278, 234, and 93 mm under 5-, 10-, 20-, and 30-year abandonment land, respectively, compared to long-term wheat. Based on the analysis of long-term experimental results, this study shows that the phenomenon of soil drying caused by long-term intensive maize production cannot be ignored in semi-arid areas and that natural re-vegetation under long-term abandonment, rather than artificial vegetation, may be the best type of vegetation reconstruction for this region based on soil water balances.

Multi‐proxy reconstruction of the Holocene vegetation and land use dynamics in the Julian Alps, north‐west Slovenia

AbstractSmall mountain lakes are natural archives for understanding long‐term natural and anthropogenic impact on the environment. This study focused on long‐term (last ca. 13 000 years) vegetation changes and sedimentary processes in the catchment area of Lake Planina pri jezeru (1430 m a.s.l.) by using mineralogical, geochemical and palynological methods. Palynological results suggest that regional vegetation between 12 900 and 11 700 cal a bp was a herbaceous–forest tundra (Pinus, Artemisia, Poaceae). Climate warming at the beginning of the Holocene (ca. 11 700 cal a bp) caused the transition from a wetland (Cyperaceae) to an eutrophic lake with alternating anoxic (pyrite) and oxic conditions (gypsum). In addition, the surrounding area became forested (Picea, Larix, Ulmus). Fagus expanded at 10 200 cal a bp and Abies at 8200 cal a bp. Between 7500 and 4300 cal a bp, human impact on the environment was barely noticeable and mostly limited to grazing. During 4300–430 cal a bp human impact became more evident and gradually increased. The greatest influence was observed from 430 cal a bp onwards, when excessive exploitation of the surrounding area (logging and grazing) severely eutrophicated the lake.

Monsoonal climate of East Asia in Eocene times inferred from an analysis of plant functional types

The spatio-temporal vegetation patterns of East Asia in the Eocene remain uncertain. In this present paper, we conduct numerical analyses of plant functional types (PFTs) for 80 Eocene floras, subdivided into three-time intervals: the early, middle, and late Eocene. Based on PFT diversity spectra, five groups are identified from cluster analysis and interpreted in terms of vegetation type. These PFT-based vegetation reconstructions suggest a northwestward retreat of dry shrub or open woodland from early to late Eocene times, coupled with the expansion of humid broadleaved forest from the southeast. This hydrological distribution is consistent with mammal distribution, lithological indicators and geochemical proxies. An overall vegetation pattern of largely east-west differentiation is detected and we note that no unequivocal tropical vegetation is observed in low-latitudes during the Eocene. Our results indicate that a monsoonal climate shaped the Eocene spatio-temporal evolution of vegetation in East Asia along with the global cooling, and rain-shadow effects by the central and southwestern China highland, as well as basin extensions in the Pacific coast in the east.

A new method based on surface-sample pollen data for reconstructing palaeovegetation patterns.

AimBiomisation has been the most widely used technique to reconstruct past regional vegetation patterns because it does not require an extensive modern pollen dataset. However, it has well‐known limitations including its dependence on expert judgement for the assignment of pollen taxa to plant functional types (PFTs) and PFTs to biomes. Here we present a new method that combines the strengths of biomisation with those of the alternative dissimilarity‐based techniques.LocationThe Eastern Mediterranean‐Black Sea Caspian Corridor (EMBSeCBIO).TaxonPlantsMethodsModern pollen samples, assigned to biomes based on potential natural vegetation data, are used to characterize the within‐biome means and standard deviations of the abundances of each taxon. These values are used to calculate a dissimilarity index between any pollen sample and every biome, and thus assign the sample to the most likely biome. We calculate a threshold value for each modern biome; fossil samples with scores below the threshold for all modern biomes are thus identified as non‐analogue vegetation. We applied the new method to the EMBSeCBIO region to compare its performance with existing reconstructions.ResultsThe method captured changes in the importance of individual taxa along environmental gradients. The balanced accuracy obtained for the EMBSeCBIO region using the new method was better than obtained using biomisation (77% vs. 65%). When the method was applied to high‐resolution fossil records, 70% of the entities showed more temporally stable biome assignments than obtained using biomisation. The technique also identified likely non‐analogue assemblages in a synthetic modern dataset and in fossil records.Main conclusionsThe new method yields more accurate and stable reconstructions of vegetation than biomisation. It requires an extensive modern pollen dataset, but is conceptually simple, and avoids subjective choices about taxon allocations to PFTs and PFTs to biomes.

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.

3D Assessment of Vine Training Systems Derived from Ground-Based RGB-D Imagery

In the field of computer vision, 3D reconstruction of crops plays a crucially important role in agriculture. On-ground assessment of geometrical features of vineyards is of vital importance to generate valuable information that enables producers to take the optimum actions in terms of agricultural management. A training system of vines (Vitis vinifera L.), which involves pruning and a trellis system, results in a particular vine architecture, which is vital throughout the phenological stages. Pruning is required to maintain the vine’s health and to keep its productivity under control. The creation of 3D models of vineshoots is of crucial importance for management planning. Volume and structural information can improve pruning systems, which can increase crop yield and improve crop management. In this experiment, an RGB-D camera system, namely Kinect v2, was used to reconstruct 3D vine models, which were used to determine shoot volume on eight differentiated vineyard training systems: Lyre, GDC (Geneva Double Curtain), Y-Trellis, Pergola, Single Curtain, Smart Dyson, VSP (Vertical Shoot Positioned), and the head-trained Gobelet. The results were compared with dry biomass ground truth-values. Dense point clouds had a substantial impact on the connection between the actual biomass measurements in four of the training systems (Pergola, Curtain, Smart Dyson and VSP). For the comparison of actual dry biomass and RGB-D volume and its associated 3D points, strong linear fits were obtained. Significant coefficients of determination (R2 = 0.72 to R2 = 0.88) were observed according to the number of points connected to each training system separately, and the results revealed good correlations with actual biomass and volume values. When comparing RGB-D volume to weight, Pearson’s correlation coefficient increased to 0.92. The results reveal that the RGB-D approach is also suitable for shoot reconstruction. The research proved how an inexpensive optical sensor can be employed for rapid and reproducible 3D reconstruction of vine vegetation that can improve cultural practices such as pruning, canopy management and harvest.

Estimation of absolute pollen productivity based on the flower counting approach: A review

Pollen productivity estimate (PPE) is one of the parameters necessary for pollen-based quantitative reconstruction of vegetation in the past. This paper summarizes and reviews the absolute PPEs (aPPEs) that were obtained with the area-based flower counting approach since the 1970s. The data for 23 species of trees are available from Japan and for 22 species of Poaceae from Japan, Spain, and Morocco. The aPPE values vary from 1 to 60 [1012 grains·ha−1·year−1], and are comparable to those previously reported in Europe and using different methods and approaches. The mean aPPEs of temperate conifers, such as Sciadopitysverticillata, Cryptomeria japonica, and Chamaecyparis obtusa, are as high as those of some of the common broadleaved trees, Castanea mollissima, Castanopsis cuspidata, and Alnus spp. The mean aPPEs of Abies firma, Fagus crenata, and Betula platyphylla are low, and those of Pinus densiflora, Quercus spp., Juglans ailanthifolia, Carpinus tchonoskii, Aesculus turbinata, and Poaceae spp. are intermediate. The relative PPE (rPPE) values of the arboreal taxa (relative to Poaceae), calculated using the aPPEs presented here, are smaller than those obtained in Western Europe and China based on the Extended R-value model approach. Differences in the sampling and analytical methods, as well as the interregional differences in Poaceae pollen productivity, might have contributed to the discrepancies observed. Although further studies are necessary, the flower counting approach is practical and informative for species-specific estimates of absolute pollen productivity and provides critical parameters for quantitatively reconstructing past vegetation in absolute units using the rates of pollen accumulation in sediments.

Holocene vegetation reconstruction in the forest–steppe of Mongolia based on leaf waxes and macro-charcoals in soils

Abstract. Vegetation and climate reconstruction in the forest–steppe of Mongolia is still challenging regarding the pattern of forest and grassland distribution during the Holocene. Different sediments containing paleosols and humic layers provide geomorphological archives for landscape development in Mongolia. n-Alkane and macro-charcoal ratios represent specific indicators to distinguish the share between grasses and trees. In a preliminary study, we investigated the applicability of these two paleo-proxies from soils for vegetation reconstruction comparing different relief positions and site conditions in the northern Khangai Mountains of Mongolia. n-Alkanes that are deposited from leaf waxes in the soil have the potential to indicate vegetation composition on a local scale. Depending on site-specific environmental conditions, n-alkanes are subjected to different degrees of microbiological decomposition, which is more intensive in soils of dry steppe than of forests. Mongolian forests are often underlain by permafrost that may reduce microbiological activity. In steppe soils, the decomposition of n-alkanes increases the quantity of mid-chain n-alkanes that adulterate the biomarker proxy signal to indicate more forest share. Macro-charcoals in soils have a site-specific component, but additional eolian input of macro-charcoals from long-distance transport can provide a distinct proportion in sediments. Thus, eolian influx of wood-derived macro-charcoal can dominate the proxy signal at sites where trees were few or had never existed. Radiometric dating of several paleosols and humic layers has shown that both proxies coincide as evidence for high grassland-to-forest ratios during the Early Holocene. By contrast, the proxy signals diverge for the Late Holocene. For this period, n-alkanes generally indicate more grassland, whereas macro-charcoals show increased wood-derived proportions. We imply that this difference is caused by increased forest fires and simultaneously spreading steppe area. A main portion of leaf waxes and charcoal particles in soils directly derive from the covering and nearby vegetation, whereas large lakes and glacier may receive these biomarkers from a larger catchment area. Thus, we conclude that soil archives provide proxies on a more local and site-specific scale than other archives do. Although the temporal resolution of soil archives is lower than for the other ones, biomarker proxies for paleosols and humic layer can be related to periods of distinct geomorphological processes. Further investigations comparing the multi-proxy data of different geomorphological archives are necessary to improve the paleo-ecological reconstruction for landscape development in Mongolia.

Past vegetation reconstruction maps and paleoclimatic variability inferred by pollen records in southern Patagonia Argentina since the Late Glacial-Holocene transition

Palaeoecological reconstructions document past vegetation distribution with estimates of the communities boundaries shifts. This work presents a compilation of palaeoecological studies from southern Patagonia Argentina as a contribution to a better understanding of the composition and distribution of Andean and extra-Andean plant communities. Paleoenvironmental reconstructions are based on pollen sequences from different types of deposits located in the forest, forest-steppe ecotone and steppes between 46° and 51°S. The comprehension of modern pollen and its relation with the actual vegetation is a critical component of palaeoecological research. Models of the current relationship pollen-vegetation-climate were applied to interpret these sequences. Their integration made it possible to reconstruct the spatio-temporal patterns of vegetation and past climatic changes since the Late Glacial-Holocene transition. Four areas were selected to map past vegetation communities; three lake basins: Pueyrredón, San Martín and Argentino, and the Deseado Massif. The local conditions given by the geomorphology of each site were also taken into account. The vegetation reconstruction during the Pleistocene-Holocene transition came from records located in the Deseado Massif only, and indicated steppes, without modern analogues, linked to arid and cold conditions. During the Holocene, plant communities were sensitive to moisture conditions related to westerly winds or Atlantic-derived precipitation events. Taxa related to the anthropogenic impact of the past centuries were found at all sites, both in Andean and extra-Andean Patagonia.

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.

Ecological Restoration and Carbon Sequestration Regulation of Mining Areas-A Case Study of Huangshi City.

As an important carbon sink indicator, the vegetation net primary productivity (NPP) is key and helpful for understanding regional carbon sequestration and storage of mining areas. Systematic analysis of NPP of the ecological reconstruction process in mining areas can effectively contribute to local governments and related departments for making ecological decisions under the “double carbon goals” (“peak of carbon release” and “carbon neutrality”) and help to promote regional sustainable development. In this study, we used the CASA model to systematically assess the temporal and spatial evolution characteristics of NPP of Huangshi City from 1990 to 2018. Meanwhile, various scenarios were set up to study the effects of climate factors, landscape pattern evolution, and ecological restoration on regional carbon storage. Our results documented that (1) NPP of the study area an increasing trend from 1990–2018 shows and exhibits significant spatial heterogeneity; (2) the significant increase of NPP was mainly in the restored mining areas, indicating that the ecological restoration of mining areas can effectively improve the regional carbon sequestration capacity; (3) from 1990 to 2018, climate change released 0.136 TgC, while landscape pattern change contributed to carbon storage with 0.266 TgC; and (4) the restoration and reconstruction of vegetation in the mining areas is an important way to achieve carbon neutrality of Huangshi City in the future, and the changes of NPP varied among different ecological restoration modes.

Quantitative vegetation reconstruction in the Central North China Plain of the last 3000 years based on the REVEALS model

The North China Plain is a region where the natural vegetation was increasingly influenced by human activities from ∼3000 cal yr B.P. (Zhang et al., 2017; Peng, 2019). We used pollen, charcoal and sediments from the Dacaozhuang Holocene profile in Ningjinpo, central North China Plain, in combination estimates of relative pollen productivity, to quantitatively reconstruct vegetation changes over the last 3000 years using the REVEALS model. Our aims were to study the combined effects of climate change and human activities on the zonal vegetation. The principal findings are as follows. 1) During 3000–2600 cal yr B.P., the study area was strongly influenced by the Yellow River, leading to a complex pollen source area, which is inappropriate for REVEALS models. Since 2600 cal yr B.P., the sediments were mainly supplied by rivers originating in the Taihang Mountains, and the reconstructed tree coverage was generally less than 20%, while that of herbaceous plants such as Artemisia, Poaceae and Asteraceae was more than 50%. This indicates that the study area was predominantly grassland with trees sparsely distributed in the mountains. 2) Crop plants (Poaceae≥35 μm, and Fagopyrum), and the occurrence of synanthropic plants like Brassicaceae and Urtica/Humulus, together with a high sedimentary content of coarse charcoal particles (>100 μm), indicate substantial disturbance of the natural vegetation by human activities from 2600 cal yr B.P. 3) During the Medieval Warm Period (1300–600 cal yr B.P.), the concentration of charcoal and the proportion of synanthropic plants were relatively high, indicating strong human activity. Nevertheless, the proportion of trees, dominated by Pinus and Quercus, was substantially higher (increasing to more than 19%) compared with the previous interval, indicating an increase in forest vegetation and thus a strong climatic influence on the vegetation. 4) During the periods of the Ming and Qing Dynasties (after 500 cal yr B.P.), the concentration of charcoal and crop plants reached a maximum and the tree coverage decreased substantially (to 4.8%), indicating the highest level of human influence on the vegetation. The shift to a cool and dry climate may also have contributed to the reduction of trees within the landscape.

Modern pollen-vegetation relationship from the Rourkela (Sundargarh District), Odisha, India: a preliminary study and a comparative account

Vegetation reconstruction from fossil pollen records depends on an adequate understanding of the relationship between modern pollen-rain and the extant vegetation. Modern pollen assemblages, that reflect the extant vegetation of an area, have been documented through the palynological analysis of 30 modern moss cushions from Rourkela, Sundargarh District (Odisha State), India. The study demonstrated the dominance of non-arboreal pollen taxa (NAPs; herbs) over the arboreal pollen taxa (APs; trees and shrubs). Tree pollen taxa, among the APs, contributed with an average sum of 23% of the total pollen sum, whereas shrubby taxa have an average pollen sum of 17%. Among the herbs (NAPs), Poaceae is the dominating herbaceous taxon in the total pollen-rain, whereas Cerealia and other cultural pollen taxa are the other prominent herbaceous taxa of the pollen-rain, besides Asteroideae. The overall pollen assemblages suggest an open nature of the forest around the study area. Insights into pollen source, representation (production and dispersal), transport and preservation of certain taxa around the study area have been also provided. Comparison of the pollen assemblages in present study with the pollen assemblages from other areas (especially from central India) has been also been made in order to have a broad overview of such study around the study area. The present study could improve our understanding of the modern pollen-rain/vegetation relationship and further aid in calibration and interpretation of the fossil pollen records.

Late Pleistocene–Holocene environmental and cultural changes in Primorye, southern Russian Far East: A review

This article presents an analytical review of the available palaeoenvironmental and archaeological records from the southern part (ca. 42°18′–45°30′N) of Primorye spanning the last ca. 21,000 years. The outlined climate and environmental history of the coastal and continental zones of southern Primorye, based mainly on vegetation reconstructions derived from the study of fossil pollen from sedimentary deposits from various archives, is compared with the archaeological cultural sequence of the region. This shows synchronicity between several phases of climate change and cultural transition, migration and changes in population numbers and/or subsistence strategies. The pronounced warming trend during the Early Holocene (Preboreal and Boreal stages) is associated with increasing numbers of long-term camp sites of the Late Palaeolithic hunter-gatherers and a growing importance of aquatic food resources. The Holocene maximum temperature and moisture conditions during the Atlantic stage were paralleled by the emergence and flourishing of the Neolithic Rudnaya, Vetka and Boisman cultures (ca. 7.7–5.5 14C ka BP/8.5–6.2 cal ka BP). The latter was a specialised maritime forager culture distributed along the Sea of Japan coast, which likely reflects climate conditions and sea water temperatures that promoted a broad spectrum of marine food resources. Towards the end of the Atlantic stage, sea levels decreased and transformed the coastal landscape of southern Primorye, which probably contributed to the decline of the Boisman culture. At the same time, the climate started to become cooler, which is likely related to the eastward migration of Zaisanovskaya culture groups from more continental (cooler) regions to milder southern Primorye. Continuous cooling during the Subboreal was accompanied by further immigrations of Zaisanovskaya people and an increase in millet cultivation, which probably occurred in the region between ca. 4.6–4.1 14C ka BP/5.3–4.6 cal ka BP. With the emergence of the Palaeometal Epoch cultures (ca. 3.6 14C ka BP/4.0 cal ka BP), food production diversified (growing number of cultivated crops, animal husbandry) and intensified, which probably decreased the people's dependence on climatic conditions unfavourable for food procurement. However, the maximum flourishing (ca. 2.8–2.6 14C ka BP/2.9–2.6 cal ka BP) of the Palaeometal Epoch Yankovskaya culture, represented by a maximum number of documented settlement sites in Primorye's prehistoric sequence, was likely related to a coeval short phase of climate amelioration with higher air and sea water temperatures and an increased sea level, which promoted agriculture and a higher productivity of coastal waters.

Simulated grazing and nitrogen addition facilitate spatial expansion of Leymus chinensis clones into saline‐alkali soil patches: Implications for Songnen grassland restoration in northeast China

AbstractThe spatial expansion characteristic of most clonal plant species makes them produce large networks by elongating rhizomes/stolons, and occupy more physical space; thus it could contribute to restoring patchy degraded grasslands. Grazing and fertilization may affect the expansion of clonal plants, and thus can affect the vegetation recovery of degraded grassland. However, these have never been tested under field conditions. A field study was conducted from 2014 to 2019 to evaluate the effects of simulated moderate grazing (SG) and nitrogen (N) addition on spatial expansion of Leymus chinensis, a widespread clonal plant species in the eastern part of the Eurasian steppe. Results showed that SG and N addition increased the number of L. chinensis ramets (small but intact modules units of this plants and with its own roots) growing in saline‐alkali soil patches; moreover, SG increased the total rhizome length and bud density of these ramets across the years by 59% and 52%, and N addition increased them by 88% and 98%, respectively. SG and N addition also increased the community biomass of the saline‐alkali soil patches by 27% and 74%, respectively. Under SG conditions, more biomass of L. chinensis was allocated to belowground organs, and to ramets growing in saline‐alkali soil patches. The findings demonstrated that both SG and N addition improved the spatial expansion of L. chinensis from favourable patches into saline‐alkali soil patches, thereby potential ramet recruitment and vegetation reconstruction. Moderate grazing management or fertilization could improve the restoration of patchy degraded grasslands by affecting the spatial expansion of clonal plants.

The Effect of Robinia pseudoacacia Plantation on Soil Desiccation across Different Precipitation Zones of the Loess Plateau, China

Ecological restoration has increased vegetation cover and reduced soil erosion, but it has also resulted in decreased soil-moisture content (SMC) and increased soil desiccation, which has ultimately led to a weakening of the “soil reservoir” function and a decline in the growth of plantations. Thus, soil desiccation has been a serious threat to the sustainable utilization of soil water resources and vegetation rehabilitation. In this study, the soil moisture of a Robinia pseudoacacia forest as well as its corresponding soil desiccation to a depth of 500 cm were measured across three different precipitation zones (400–450, 500–550 and 550–600 mm) along a north–south transect on the Loess Plateau. The results showed that the soil-moisture environment and soil desiccation status generally improved with the increasing precipitation gradient, while soil-moisture over-consumption significantly declined (p < 0.05). However, due to the elder forest-stand age and severe growth recession, the soil desiccation of R. pseudoacacia in the northern part was less than that in central zones. As the forest-stand age increased, SMC of R. pseudoacacia increased firstly and then decreased, and both soil-moisture consumption and the average soil desiccation rate peaked in the RP-5a, showing no significant consistence with forest-stand age. Therefore, understanding the soil-moisture status of forestland may better provide scientific basis for native vegetation restoration and reconstruction in water-limited regions.

The variability of Amazonian palm phytoliths

The Arecaceae (palm) family is one of the most common and economically important plant groups in Amazonia, and play large roles in ecosystem functioning and carbon dynamics. The modern dominance of palms may be a result of environmental gradients, past climate variability and legacies of past human activities. To understand the roles people and environment have played in shaping the abundance and widespread occurrence of Amazonian palm species, past vegetation reconstructions using palaeoecological proxies that can identify palm species or genera are needed. Phytoliths are siliceous microfossils abundantly produced in palms and are used to reconstruct past vegetation composition. The aim of this paper was to assess the variability of Amazonian palm phytolith morphotypes and to determine which morphological characteristics can be used to increase the taxonomic resolution of palm identifications. Phytolith size, sphericity, spinule traits and number of (surficial) projections were measured for 24 Amazonian palm species. Differences were compared using PCA and ANOVA or Tukey tests, followed by Kruskal-Wallis or Dunn tests. Results show potential for phytoliths of Aiphanes aculeata, Attalea maripa, Bactris simplicifrons, Dictyocaryum fuscum, Euterpe precatoria, Iriartea deltoidea, Oenocarpus bacaba, Socratea exorrhiza and the genera Geonoma, Bactris, Euterpe and Oenocarpus to be identified based on their size, shape or number of projections. This will allow future phytolith analyses to reconstruct past palm abundances with an increased taxonomic resolution. We have formulated our findings into a ‘quick guide’ to identify palm phytoliths and test hypotheses regarding the drivers of modern palm distributions and abundances.