Impacts of global climate change on terrestrial ecosystems are imperfectly constrained by ecosystem models and direct observations. Pervasive ecosystem transformations occurred in response to warming ...and associated climatic changes during the last glacial-to-interglacial transition, which was comparable in magnitude to warming projected for the next century under high-emission scenarios. We reviewed 594 published paleoecological records to examine compositional and structural changes in terrestrial vegetation since the last glacial period and to project the magnitudes of ecosystem transformations under alternative future emission scenarios. Our results indicate that terrestrial ecosystems are highly sensitive to temperature change and suggest that, without major reductions in greenhouse gas emissions to the atmosphere, terrestrial ecosystems worldwide are at risk of major transformation, with accompanying disruption of ecosystem services and impacts on biodiversity.
The natural distribution of Japanese cedar (Cryptomeria japonica) has been disturbed by human activities, owing mainly to its value as timber; thus, its position in the vegetation zone of Japan is ...not clear. Therefore, it is important to determine the history of C. japonica forests before human influence. We reviewed the transitions in distribution and abundance of C. japonica in the Japanese Archipelago since the last interglacial period by using published pollen data. During the last interglacial, temperate deciduous broadleaf forests developed on northeastern Honshu Island, whereas on southwestern Honshu Island C. japonica populations increased, accompanied by warm‐temperate evergreen broadleaf trees. During the first half of the last glacial period, C. japonica forests developed throughout the Japanese Archipelago except on Hokkaido. Thereafter, 60,000–30,000 years ago, C. japonica covered the area around Lake Biwa and the Izu Peninsula. During the Last Glacial Maximum, C. japonica was most abundant on the Izu Peninsula, and small refugial populations were located along the coast of the Sea of Japan from southwestern to northeastern Honshu, and along the Pacific coast of Shikoku Island. During the Middle Holocene, C. japonica populations increased rapidly in southwestern Honshu. Two thousand years ago, before the intensification of human activities, C. japonica was widespread in warm‐ to cool‐temperate zones on the Sea of Japan side of Honshu, the Izu Peninsula, the Pacific coast of Shikoku Island, and Yakushima Island. This evidence indicates that C. japonica is one of the major tree species in the Japanese vegetation zone.
Two thousand years ago, before the intensification of human activities, Cryptomeria japonica was widespread in warm‐ to cool‐temperate zones on the Sea of Japan side of Honshu, the Izu Peninsula, the Pacific coast of Shikoku Island, and Yakushima Island.
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.
The Neotoma Paleoecology Database is a community-curated data resource that supports interdisciplinary global change research by enabling broad-scale studies of taxon and community diversity, ...distributions, and dynamics during the large environmental changes of the past. By consolidating many kinds of data into a common repository, Neotoma lowers costs of paleodata management, makes paleoecological data openly available, and offers a high-quality, curated resource. Neotoma’s distributed scientific governance model is flexible and scalable, with many open pathways for participation by new members, data contributors, stewards, and research communities. The Neotoma data model supports, or can be extended to support, any kind of paleoecological or paleoenvironmental data from sedimentary archives. Data additions to Neotoma are growing and now include >3.8 million observations, >17,000 datasets, and >9200 sites. Dataset types currently include fossil pollen, vertebrates, diatoms, ostracodes, macroinvertebrates, plant macrofossils, insects, testate amoebae, geochronological data, and the recently added organic biomarkers, stable isotopes, and specimen-level data. Multiple avenues exist to obtain Neotoma data, including the Explorer map-based interface, an application programming interface, the neotoma R package, and digital object identifiers. As the volume and variety of scientific data grow, community-curated data resources such as Neotoma have become foundational infrastructure for big data science.
The objective of this study was to develop a deep learning-based tree species identification model using pollen grain images taken with a camera mounted on an optical microscope. From five focal ...points, we took photographs of pollen collected from tree species widely distributed in the Japanese archipelago, and we used these to produce pollen images. We used Caffe as the deep learning framework and AlexNet and GoogLeNet as the deep learning algorithms. We constructed four learning models that combined two learning patterns, one for focal point images with data augmentation, for which the training and test data were the same, and the other without data augmentation, for which they were not the same. The performance of the proposed model was evaluated according to the MCC and F score. The most accurate classification model was based on the GoogLeNet algorithm, with data augmentation after 200 epochs. Tree species identification accuracy varied depending on the focal point, even for the same pollen grain, and images focusing on the pollen surface tended to be more accurately classified than those focusing on the pollen outline and membrane structure. Castanea crenata, Fraxinus sieboldiana, and Quercus crispula pollen grains were classified with the highest accuracy, whereas Gamblea innovans, Carpinus tschonoskii, Cornus controversa, Fagus japonica, Quercus serrata, and Quercus sessilifolia showed the lowest classification accuracy. Future studies should consider application to fossil pollen in sediments and state-of-the-art deep learning algorithms.
This study examined the orbital-scale vegetation response to seasonal climate changes related to the East Asian monsoon and ocean currents during the last glacial–interglacial cycle based on a new ...continuous pollen record from Lake Biwa, western Japan. During MIS 6, 4, and 2, pinaceous conifer forests were present in both inland and Japan Sea coastal areas around Lake Biwa, influenced by cold and dry conditions in both summer and winter. In contrast, deciduous broadleaved forests and evergreen forests grew during interglacial periods in MIS 5e and 1 under relatively warm and humid conditions in summer, as well as in winter. Fagus crenata, a tree endemic to the Japanese archipelago, was especially widely distributed during MIS 5e due in part to winter snowfall caused by warm current inflows in the Sea of Japan. During MIS 5 and 3, temperate conifer trees were dominant. During periods of low summer insolation in MIS 5, the endemic tree Cryptomeria japonica became dominant in both inland and coastal areas of the region, likely as a result of high precipitation in early summer related to southward shifts of the summer monsoon front and moderate winter climate conditions. In contrast, Sciadopitys verticillata, which is also an endemic tree, had own habitat around inland areas of western Japan during the periods of high summer insolation in MIS 5. Climate fluctuations during the glacial–interglacial cycles created several ecological niches in time and space for each endemic tree in the Japanese archipelago.
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•Pollen records from Lake Biwa have recorded vegetation fluctuations since MIS 6.•Regional vegetation patterns based on long-core pollen records are shown.•Vegetation responses to changes in monsoons and ocean currents were determined.•Endemic trees had own habitats in glacial–interglacial climate oscillations.•Orbital-scale climate fluctuations created ecological niches in time and space.
Phytoliths and charcoal preserved in two soil sections in northern part of Aso Caldera, central Kyusyu, Japan revealed grassland and fire history since the late-glacial. The phytolith assemblages ...were divided into two significant zones, respectively. Phytolith assemblages show that the grassland vegetation, composed mainly of Sasa species, has continued since the late-glacial. The grassland compositions changed from Sasa type to Pleioblastus type around 7.5 cal ka. Charcoal records indicate that fire occurred at least in the early Holocene and continued to the present. Judging from the phytolith and charcoal records, the establishment of grassland may have been affected by not only climate changes and volcanic activities, but also fire since the early Holocene. Around the Aso Caldera, numerous prehistoric archaeological sites since the late-glacial have been discovered. Therefore, the occurrence of fire during the Holocene was possibly caused by human activities, and fire influenced the establishment of grassland. The results are important for understanding the relation between the fire and grassland vegetation in the regions where human activity has continued.
Climatically driven Late Pleistocene and Holocene vegetation changes were reconstructed based on pollen records from the sediments of Lake Kotokel and Cheremushka Bog, located on the eastern shore of ...Lake Baikal. The described paleoenvironmental record has higher resolution than records collected from Lake Baikal and unites individual events identified in prior studies of bottom and onshore cores. Remarkable shifts in landscapes and expansions of index plants are as follows. Forest tundra and/or forest steppe landscape with birch, spruce,
Artemisia, and Poaceae prevailed at ca. 50–25
14C kyr
BP. Tundra and/or steppe vegetation dominated by
Artemisia and Poaceae was typical for the Last Glacial Maximum. The expansion of shrub birch and willow occurred at ca. 15.5
14C kyr
BP. Two peaks of spruce expansion at ca. 47.5–42.4
14C kyr
BP (Karginian time) and at ca. 14.5–13
ka (Bølling-Allerød warm intervals) suggest that the condition were more humid than today. A slight increase in
Artemisia at ca. 11–10.5
14C kyr
BP (13–12
ka) was indicative of the Younger Dryas event. An expansion of birch forests with fir at ca. 12–6.4
ka suggests higher humidity. The currently dominant Scots and Siberian pine forests with birch expanded since 6.4
ka.
In the areas adjacent to Kyoto, an ancient capital of Japan, the regional vegetation is mostly secondary forest. In order to reconstruct the fire and vegetation history of the area and to estimate ...when and how the secondary forest was established, peat cores were obtained from a small basin in the western Tamba Highlands, 35-km northwest of Kyoto city. Pollen, plant macrofossil and charcoal records from the site indicate that the cool-temperate forest characterized by beech (Fagus crenata) with Japanese cedar (Cryptomeria japonica) developed in the middle Holocene (c. 4700–2400 cal BP). Forest fires were rare during this period. In the late Holocene, charcoal data indicate that at least two major fire events occurred. Following a fire c. 2500 cal BP, the vegetation changed from beech-dominated cool-temperate forest with Japanese cedar to a forest with less beech and increased pine. The next conspicuous fire took place at c. 900 cal BP, after which the vegetation shifted to a deciduous oak and pine-dominated forest, similar to the present vegetation around the site. The Gramineae pollen percentage was continuously high since the second fire event, suggesting that grassland was maintained. In the western Tamba Highlands, secondary forests were established during the eleventh century, but resource depletion was less serious and open secondary forest has been maintained by human activities.
Macroscopic charcoal and pollen in mire sediments from the Soni Plateau, Central Japan, were evaluated to clarify intentional fire history and relationship between vegetation transition and ...anthropogenic fire or climate change. The sediments deposited in recent centuries, when fire probably occurred every year, include a number density of macroscopic charcoal fragments exceeding 100 fragments/cm3. High charcoal abundances (>100 fragments/cm3) were also recognized in sediments deposited at ∼7000 cal BP and from 1500 cal BP to the present. Sediments deposited between 7000 and 1500 cal BP have a low abundance of charcoal fragments (<100 fragments/cm3, but mainly <20 fragments/cm3). These results, combined with the pollen record, indicate that during the period until 1500 cal BP (except for ∼7000 cal BP), forests of Abies, Quercus, and Fagus developed in a largely fire-free environment in and around the plateau. In this period vegetation transition was mainly influenced by climate change as follows; between 7500 and 6500 cal BP deciduous broadleaf forest grew under cool-temperate conditions; between 6500 and 5500 cal BP evergreen broadleaf forest were expanded under warming; between 5500 and 1500 cal BP evergreen broadleaf forest were developed probably under warm conditions with much precipitation. Frequent fires during a short period at ∼7000 cal BP, probably due to human activities, possibly resulted in disturbance of forest, although Castanea forest subsequently developed across the plateau following this fire-prone period. After ∼1500 cal BP (dated at least 1000 cal BP), periodic intentional fires resulted in the development and persistence of grassland dominated by Gramineae.
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