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Climate-related factors (e.g. environmental energy, water availability and climatic seasonality/variability) and habitat heterogeneity have long been considered as the main drivers of species diversity on a broad spatial scale. However, it is controversial whether the above environmental factors can explain observed diversity patterns in varied communities such as invertebrate taxonomic group, especially mollusks. Moreover, there are until now few systematic assessments of the relative roles of different factors in determining the patterns of mollusk species diversity in monsoon-dominated regions. Here, we depict variations in terrestrial mollusk diversity based on a dataset comprising 282 assemblages collected from surface soils along an similar to 800-km climatic gradient from subtropical to warm temperate and mid-temperate regions in northern China. The results show that mollusk species diversity increases significantly from similar to 3-4 species to similar to 17-19 species when annual temperature and precipitation increase up to similar to 12 degrees C and similar to 700 mm, respectively; however, at or above these values the rate of increase is reduced. These indicate that the relationships between mollusk species diversity and climatic factors are nonlinear. Statistical analysis suggests that water availability (relative humidity) and temperature seasonality (January temperature and annual temperature range) dominate the observed pattern of mollusk species diversity. Moreover, habitat factors such as vegetation condition and soil types were also important in determining mollusk species diversity. They may be an indirect reflection of the effects of monsoonal water-energy dynamic on mollusk communities. Our results suggest that more attention should be paid to water availability and temperature seasonality in predicting future biodiversity changes, especially in the environmentally stressed northwestern part of the East Asian monsoon region. (C) 2019 Elsevier B.V. All rights reserved.

We show a superplastic diffusion bonding method to join metallic glasses (MGs) via high-speed heating at 2000 K/min taking a timescale of the order of microseconds to milliseconds at ambient pressure because the minimum viscosity of supercooled liquid drastically decreases as the heating rate increases. The results show strong metallic bonds are formed but the amorphous structure is still maintained. Finally, we establish a general equation containing the involved parameters for high-speed heating bonding. This method provides a new path to join MGs rapidly and benefits for improving the critical size of MGs.

The Peiligang culture is the earliest Neolithic culture in the middle Yellow River valley and represents the emergence of cereal farming in the region. Present records imply the concurrence of millet farming and mixed millet-rice farming in the Peiligang culture, but their spatial distribution pattern is still unknown, because of the there is a lack of comparative studies on crop remains from different sites. Here, we present the results of analyses of phytoliths and plant macroremains in archaeological sediments from four Peiligang culture sites, as well as an integration of crop records from nine other sites. These sites are classified into two types in terms of their geographical locations: those in alluvial plains and those in hilly lands. The results confirm the coexistence of millet and mixed farming in the Peiligang culture, rather than one or the other. Their spatial pattern involved millet farming in the hilly lands, with mixed farming done in the alluvial plains. Compared to the sites in the hilly lands, the sites in the alluvial plains have enough water sources and vast amounts of flat land, making it possible to cultivate rice and conduct mixed farming. In all Peiligang culture sites, regardless of any agricultural modes, common millet ( Panicum miliaceum ) was predominant among the crop assemblages. In the same climate background, the agricultural mode selection in different sites was mainly influenced by landform and hydrology. This spatial pattern of farming also reflects human adaptive subsistence practices, which respond to different natural circumstances.

In this paper, we report late Pleistocene to Holocene changes in the shell size and age structure of the gastropod, Opeas striatissimum, in two loess profiles in the Chinese Loess Plateau, spanning the past 27 ka. During the interval of ~17–8 ka, in response to climatic warming, we observed marked increases in shell dimensions and a more diverse age structure (age classes), as well as a ~20% increase in the number of adult individuals. Shell growth and enhanced survival from juvenile to adult, in turn, resulted in an increase in the population size, which reached a maximum during the interval ~8–3 ka, corresponding to the Holocene Climatic Optimum. We also observed an abrupt decrease in shell height and related significant decreases in the total number of individuals of Opeas striatissimum and adult individuals at the time of the Younger Dryas cold climatic event. We suggest that the observed morphologic and demographic changes observed for Opeas striatissimum reflect changes in the growing season, linked to changes in monsoon rainfall and climate stability, in response to climate fluctuations from the late Pleistocene to the Holocene. Our study provides a long-term perspective that helps refine mechanistic population models of invertebrates in the face of future climate change.

Although the summer monsoon is the dominant source of precipitation in the East Asian monsoon region (EAMR), there is long-standing uncertainty about the spatial and temporal variability of precipitation on the centennial time scale. In this study we analyzed two well-dated, high-resolution, published paleoclimatic records in order to determine the variability of precipitation in the EAMR during the Holocene. One record is a decadal-resolution pollen record from an annually-laminated Maar lake in Northeast (NE) China, and the other is a U Th dated, multi-decadal-resolution speleothem record from Central China. Advanced time-series analysis of the two records provides unambiguous evidence for asynchronous summer monsoon rainfall variability on centennial to millennial time scales in the EAMR. The pollen and speleothem records indicate long-term and ~ 500-yr quasi-periodic changes in humid/dry climatic shifts against the background of an insolation-forced climatic trend throughout the past 8580 years. Phases of wetter climate (during ~7000–5500 cal yr BP) and drier climate (during ~1400–300 cal yr BP) in NE China are closely related to different climatic phases in Central China. However, the ~500-yr cyclic rainfall changes in Central China lag those in NE China by several decades to almost two centuries. During the ~500-yr periodic changes in the monsoon, a climatic pattern encapsulated as “Northern drought, southern flooding” prevailed during an El Nino-like phase, whereas the opposite pattern “Southern drought, northern flooding” occurred during a La Nina-like phase. The asynchronous pattern of ~500-yr climatic cyclicity between the northern and southern EAMR may have been caused by the El Nino-Southern Oscillation, linked to low-latitude oceanic and atmospheric interactions.

The cascading impacts of climate-driven vegetation change on terrestrial invertebrates via trophic and habitat routes is a matter of outstanding concern. However, the combined responses of plant-animal associations in terrestrial ecosystems have seldom been reported on geological timescales, which raises the important questions of how frequently and to what extent such multi-trophic shifts in taxa have occurred during previous warming scenarios. Here we use a combination of mollusk, palynological, and climatic proxy evidence preserved within loess deposits in the southern Chinese Loess Plateau (CLP) to demonstrate how long-term changes in hydroclimatic dynamics during the past 26 kyr were reflected in the subsequent ecological changes. Specifically, there was a shift from a predominantly cold-tolerant mollusk fauna in a dry-steppe environment under cold-dry conditions during the last glacial, to a predominantly thermal-mesophilous fauna in a meadow-steppe environment under a warm temperate climate in the early-middle Holocene. Warmth-adapted mollusk species such as Opeas striatissimum and Punctum orphana were found to have been associated with several deciduous tree taxa (e.g., Corylus, Quercus, and Pterocarya) in both the Holocene record and in the modern ecosystem (based on surveys of 356 surface-soil plots). This suggests there is a clear ecological interdependency between specific vegetation types and mollusk assemblages. As such, the long-term vegetation-mollusk fossil records highlight the indirect impacts of climate change on terrestrial invertebrate turnover via plant-derived food structure and habitat routes, with major implications for understanding how these ecosystems are likely to respond to future climate changes.

Reconstructing and quantifying human impacts is an important step in understanding how, when, and to what extent humans have changed terrestrial ecosystems via agricultural land use during the Holocene. However, the use of soil-faunal indicators and an associated quantitative model of land use intensity to study anthropogenic disturbance is relatively poorly developed. In this study we collected 139 samples of soil-dwelling snails from urban land and human settlements, cultivated land, modified and natural vegetation mosaics, and natural habitats in northern China, in order to characterize the snail assemblages in human-modified habitats. The results show that cultivated land and planted forest are mainly dominated by snails of Cathaica fasiola, Bradybaena ravida, Vallonia tenera, etc., while natural habitats are characterized by an even distribution of members of the families, such as Ariophantidae, Cochlicopidae, Pupillidae, Subulinidae. Canonical correspondence analysis indicates that human activity (quantified by the human influence index, HII) is one of the most important factors shaping the composition of snail fauna in man-modified habitats. There is a significant relationship between modern snail data and HII, and the transfer function established by weighted-averaging partial least squares (WA-PLS) model for HII exhibits a good statistical performance. We then applied the calibration model to a fossil snail record spanning the last 12 kyr from the Chinese Loess Plateau (CLP). The reconstructed HII increases slightly at ∼5 ka and abruptly at ∼2 ka, coinciding with increases in the human population of the CLP, local cultural development, and human-induced changes in vegetation cover. Our quantitative reconstruction indicates that human activities, via agricultural activity, may have permanently altered natural ecosystems and the soil fauna for at least the last two millennia.

This paper is devoted to investigating the Mobius differential geometry of a new class of surfaces, named the surfaces with closed Mobius form. The main theorem shows that a surface with closed Mobius form can be determined by a smooth function satisfying a 5th order partial differential equation presented in this paper. As an application of the main theorem, the isothermic surfaces with closed Mobius form are classified.

article i nfo The East Asian monsoon probably existed as early as at the Palaeogene/Neogene boundary. However, its evolutionary process is still less well known owing mainly to the lack of long, continuous palaeoenviron- mental records. The recently reported Miocene (22-6.2 Ma) and late Miocene-Pliocene (7.1-3.5 Ma) loess- palaeosol sequences from the western Chinese Loess Plateau (CLP) provide new insights into the evolution of the monsoon system. However, reports on the bioclimatic indicators from these deposits and the subsequent reconstruction of the palaeomonsoon are rare. Here we present a Pliocene terrestrial mollusk record from the western CLP and discuss the possible impact of isolation gradients on the East Asian summer monsoon. Our results show that most peak values of the dominant thermo-humidiphilous mollusk taxa, Metodontia and Punctum, a proxy of the East Asian summer monsoon, approximately correspond to maxima of mean summer insolation gradient between middle and low latitudes as well as some maximum values of the 35°N insolation, suggesting a possible causal link between the summer monsoon and the insolation parameters. The major frequencies from spectrum analysis of the sum of the two warmth- and moisture-loving taxa through the loess-palaeosol succession match those obtained from the mean summer insolation-gradient variations between middle and low latitudes over this geological period, providing further evidence for such a causal relationship. Mean summer insolation gradient between middle and low latitudes could influence atmospheric circulation (in the present condition the East Asian summer monsoon). Any elevated mean summer insolation gradients between middle and low latitudes would have intensified the East Asian summer monsoon and the flux of moisture and heat over the oceans to the interior region including the CLP, creating favorable conditions for the expansion of the mollusk fauna. As such, the mollusk record from the loess-palaeosol deposits in the western CLP provides evidence for insolation-gradient impacts on the development of the East Asian monsoon system in the Pliocene.

article i nfo More and more evidence indicates that the onset of the East Asian (EA) monsoon can be traced back to the Oligocene-Miocene boundary (at about 23 Ma). However, the process of its evolution is still less well-known until now. Here we investigate its late Neogene evolution by analyzing a terrestrial mollusk sequence, from the Chinese Loess Plateau (CLP), covering the period between 7.1 and 3.5 Ma. Considering the modern ecological requirements of these organisms, we were able to define two groups of cold-aridiphilous (CA) and thermo-humidiphilous (TH) species, representing the EA winter and summer monsoon variations, respectively, as previously defined in the Quaternary glacial-interglacial cycles. Variations in these two groups indicate two different monsoon dominated periods during 7.1-3.5 Ma. First, between 7.1 and 5.5 Ma, the EA winter monsoon, with a 100-kyr periodicity, was dominant. Second, between 5.1 and 4 Ma, the EA summer monsoon dominated, with a 41-kyr periodicity. Furthermore, our mollusk record yields valuable evidence for a late Miocene-Pliocene transition of about 400 kyr from winter monsoon dominated towards summer monsoon dominated, associated with a periodicity transition from weak 100 kyr to 41 kyr. The strengthened winter monsoon interval, with a 100-kyr periodicity, is coeval with orbital-scale global ice- volume changes, in conjunction with the uplift of the Tibetan Plateau which probably reinforced the winter monsoon sub-regime. Conversely, closures of the Panama and Indonesian seaways, associated with changes in obliquity between 5.1 and 4 Ma, are probably major forcing factors for the observed dominant summer monsoon with 41-kyr frequency, favoring heat and moisture transports between low and high latitudes to allow TH mollusks to grow and develop in the CLP.

A new molluscan fossil record from the late Miocene–Pliocene Xifeng Red Clay sequence in the central Loess Plateau, northern China, reveals the process of ecological environmental changes during ∼ 6.2–2.4 Ma. Three marked ecological shifts in mollusk assemblages occurred at about 5.4, 4.5, and 3.4 Ma, which reflect changes in the East Asian monsoon circulation. A predominantly cold-aridiphilous group reveals an extremely cold dry climate due to strengthened East Asian winter monsoon during ∼ 6.2–5.4 Ma. A predominantly thermo-humidiphilous group from ∼ 5.4–4.5 Ma indicates a strengthening of the East Asia summer monsoon circulation. The marked occurrence of meso-xerophilous taxa during ∼ 4.5–3.4 Ma implies mild climatic conditions. From 3.4 Ma, the cold-aridiphilious species again became dominant in the fossil assemblages, indicating that the winter monsoon was gradually intensifying towards the Quaternary glaciations. Climate changes in this region were characterized by stepwise cooling from 5.4 to 2.4 Ma with a 1 Ma rhythmicity. The cooling trend is in good agreement with the general global cooling trend during this period, as documented by marine δ18O records. The formation and development of the Northern Hemisphere ice sheets during the late Pliocene accelerated the climate deterioration towards the Quaternary glaciations. The history of environmental changes revealed by the Red Clay molluscan fossils is coupled in phase with the process of Tibetan Plateau uplift, which may be the major cause and forcing mechanism of late Miocene–Pliocene environmental changes in the Loess Plateau.