Human disturbance is one of the essential driving forces of landscape evolution. The quantitative evaluation of the spatial and temporal characteristics of landscape evolution and its relationship ...with human disturbance are of great significance to regional ecological protection and management and are crucial for achieving coordinated socioeconomic development and ecological–environmental protection. In this study, we took the coastal wetlands in northern Jiangsu province, China, as the research area, and proposed a quantitative evaluation method for directional landscape evolution. On this basis, the spatiotemporal characteristics of the landscape evolution from 1980 to 2020 and the relationship with human disturbance were quantitatively evaluated by combining a human disturbance index and statistical methods. The results showed that: (1) The area of the natural wetlands decreased significantly over the past 40 years, while the areas of artificial wetlands and non-wetlands increased significantly. (2) The landscape evolution process was dominated by the degradation process. The main types of degradation were natural wetland conversion to artificial wetland and non-wetland areas and Spartina alterniflora invasion. The restoration type was mainly restoration among artificial and natural wetlands. (3) The degradation of wetland landscapes demonstrated a southward shift trend and the spatial consistency with the change of the human disturbance index was high (the correlation coefficient was 0.89). (4) The human disturbance index was significantly and positively correlated with the rate of degradation, with a correlation coefficient of 0.43, and was not significantly and positively correlated with the restoration rate, with a correlation coefficient of 0.14. The findings in this paper provide additional information and theoretical guidance for the control of coastal wetland development and utilization, as well as for achieving coordinated wetland resource development together with utilization and ecological protection in the coastal wetlands of Jiangsu province, China.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Mg/Ca ratio in stalagmites primarily serves as an indicator of past hydrological conditions rather than temperature variations. Here, we present an Mg/Ca ratio record in a stalagmite from northern ...China, spanning ice age termination II. A unique finding is that Mg/Ca ratio shows a moderately strong positive correlation with cave air temperature obtained from clumped isotopes data in the same stalagmite. The stable hydrogeochemistry of source water and high temperature sensitivity of Mg partition coefficient plausibly explain this temperature dependence. Furthermore, we establish an Mg/Ca‐temperature calibration for stalagmites from mid‐latitudes, encompassing a temperature range between ∼2 and ∼15°C, where Mg/Ca = 14.221 × e0.073×T (R2 = 0.40). Applying this function to Mg/Ca ratio from similar stalagmites could tentatively provide a quantitative regional temperature record over millennial and centennial timescales. This research highlights Mg/Ca ratio in stalagmites as a potential palaeo‐temperature proxy and introduces, for the first time, a tentative Mg/Ca‐temperature calibration function for speleothems.
Plain Language Summary
Stalagmite is one type of speleothems that grow from the floor of caves. The geochemical indexes within stalagmites, such as Mg/Ca ratio, can help us to understand the past climate changes. Here, we conducted a study on a stalagmite from northern China during ice age termination II. Traditionally, Mg/Ca ratios in stalagmites have been used to investigate past hydrological conditions. However, we found that Mg/Ca ratio matches the cave air temperature obtained from clumped isotopes data within the same stalagmite. This correlation was explained by the stable chemistry of the source water and the sensitivity of Mg partition coefficient to temperature. We also developed a tentative formula to calculate past temperature from Mg/Ca ratio in similar speleothems.
Key Points
A Chinese stalagmite at termination II shows moderately strong positive correlation between Mg/Ca ratio and clumped isotopes‐temperature
Stable drip water hydrogeochemistry and high temperature sensitivity of Mg partition coefficient may explain this temperature dependence
We tentatively establish, for the first time, an Mg/Ca‐temperature calibration function for speleothems
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Objective To study the age-specific distribution of antimüllerian hormone (AMH) and describe the association of AMH with androgenic and metabolic profiles at different ages. Design Cross-sectional ...study. Setting University hospital. Patient(s) A total of 6,763 Chinese women from birth to menopause. Intervention(s) None. Main Outcome Measure(s) Anthropometric parameters (height, weight, and blood pressure), and levels of AMH and testosterone, glucose metabolism, and lipid profiles. Result(s) According to the level of AMH, four age phases were established: childhood (0–10 years), adolescence (11–18 years), reproductive age (19–50 years), and advanced age (≥51 years). During childhood and adolescence, AMH levels increased, reaching a peak at 18 years. A decline occurred thereafter during the reproductive-age period until the age of 50 years, and it remained at a low level above 0 onward. We found that AMH was negatively correlated with testosterone in childhood ( r = −0.25), but was positively correlated with testosterone and the free androgen index in adolescence ( r = 0.30; r = 0.26, respectively) as well as during the reproductive phases ( r = 0.28; r = 0.31, respectively). No correlation was observed between AMH and body mass index, fasting blood glucose, fasting insulin, the homeostasis model assessment, total cholesterol, triglycerides, low-density lipoprotein, or high-density lipoprotein at any phase. Conclusion(s) From birth to 18 years, AMH increases, then it declines thereafter, indicating changes of ovarian maintenance. A positive relationship between androgenic profiles and AMH during adolescence and reproductive years implies a synchronism between androgens and ovarian reserve.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Macroaggregates are the main contributors to SOC mineralization.•The cumulative mineralization in the erosional area was lower than in the depositional area.•The breakdown of soil aggregates during ...transport accelerates SOC mineralization.
Water erosion exerts a profound, but uncertain effect on the terrestrial carbon cycle. Therefore, the soil erosion intensity is uncertain in different terrains. Previous studies have focused on the slope and intensity of soil erosion, while ignored the special terrain such as gully created by erosion. To advance the understanding of the mineralization dynamics of soil organic carbon (SOC) from the micro perspective, the relationship between soil erosion and carbon source and sink is expected to be further improved. In this study, we explored the impact of water erosion on SOC mineralization in the areas of gully erosion in Qingyuan mountain, Jiangxi, China by combining the 137Cs technique and laboratory incubation experiment, calculated the first-order kinetic model parameters of the SOC mineralization of bulk soil and aggregates in the area of gully erosion, and estimated the correlation between the factors that may affect SOC mineralization. The results showed that (1) the mineralization rates of SOC in the bulk soil and aggregates showed fluctuations and reached a peak, and finally became stable. The soil erosion intensity was significantly positively correlated (p < 0.05) with the cumulative mineralization of SOC. (2) The cumulative mineralization in the depositional area (489.67 mg kg−1) was higher than that in the erosional area (402.69 mg kg−1). (3) Soil macroaggregates were the main contributors to SOC mineralization (63.56%–92.28%), and the soil macroaggregate organic carbon mineralization dynamics was more sensitive to soil erosion. Additionally, significant effects (p < 0.05) of soil mechanical composition, capillary pores, saturated water content, and contents of carbon and nitrogen on SOC mineralization were observed. Erosion increased the risk of SOC loss by mineralization of SOC, especially in macroaggregates. The deposition process caused the enrichment and burial of SOC, and the background level of SOC and the content of macroaggregates in the depositional area were higher than those in the erosional area. The results showed that soil erosion increased the risk of SOC loss by mineralization of SOC based on laboratory simulation. The present study aiming at examining the effect of gully erosion on the mineralization and sequestration of SOC provides important insights into balancing the global carbon budget.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Knowledge of ecophysiological characteristics of different land snail species is crucial for defining climatic significance of snail faunal assemblages. However, little work has been done in this ...aspect, hindering our obtaining unambiguous paleoclimatic information using these proxy indicators. Here we document for the first time the different ecophysiological characteristics of Cathaica sp. and Bradybaena sp. land snails using the stable isotopes and clumped isotope (Δ47) of the shell carbonates. The Δ47‐derived temperatures for both species revealed a robust correlation with environmental temperatures. Moreover, the temperatures for Cathaica sp. are 3–5°C higher than those for Bradybaena sp. land snails, indicating different ecophysiological adaptations or growing seasons of the two species. Specifically, Cathaica sp. snails prefer living in a warm‐humid summer, whereas Bradybaena sp. snails are active in the relatively cool‐arid spring and/or autumn. The result testifies to the Δ47 in snail shell carbonates as a promising paleothermometer in monsoonal region and presents new insight into paleoclimatic explanation of these land snail species. This finding highlights the importance of climatic seasonality in the changes of the faunal assemblages of land snails.
Key Points:
Clumped isotopes of snail shells are a season‐specific geothermometer in monsoonal region
Cathaica sp. snails had calcification temperatures 3–5°C higher than Bradybaena sp. snails
Climatic seasonality determined the faunal assemblages of land snails in north China
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Termination II (T‐II) is a natural reference for evaluating the potential effect of substantial ice sheets melting on monsoon and temperature changes caused by global warming. However, the phase ...relationship of East Asian summer monsoon (EASM) and temperature during T‐II remains enigmatic due to the lack of paleotemperature proxies. Here, we provide high‐resolution mean annual atmospheric temperature (MAAT) estimates during T‐II in northern China using speleothem clumped isotopes. Compared with present, the maximum MAAT at the last interglacial was 1.8 ± 1.5°C higher, and the minimum MAAT at the penultimate glaciation was 6.8 ± 1.3°C lower. EASM and temperature decoupled during the first 2100 years of the record and coupled onwards. This variable phase relationship is plausibly modified by the strength of the cold anomaly in North Atlantic triggered by collapse of ice sheets. When the cold anomaly exceeds a boundary condition, it could not only weaken EASM but also lower temperature.
Plain Language Summary
Ice Age Termination II (T‐II) represents the transition from the penultimate glaciation (PG) to the last interglacial (LIG). It is a natural reference for evaluating the potential effect of substantial ice sheets melting caused by global warming on monsoon and temperature changes. Speleothem oxygen and clumped isotopes are monsoon and temperature proxies, respectively. We reconstructed the evolution of monsoon and temperature during T‐II using theses proxies from a northern Chinese stalagmite. We found that, it was ∼2°C warmer at the LIG and ∼7°C colder at the PG than present in East Asia. Interestingly, East Asian monsoon and temperature decoupled initially and coupled onwards during T‐II, which is plausibly ascribed to the modulation of extreme cooling triggered by collapse of great ice sheets and resultant large freshwater flux during deglacial.
Key Points
Mean annual atmospheric temperature estimates during Termination II (T‐II) in northern China using speleothem clumped isotopes
Compared with present, it was ∼2°C warmer at the last interglacial and ∼7°C colder at the penultimate glaciation
Variable phase relation of East Asian monsoon and temperature at T‐II is due to the modulation of the cold anomaly in North Atlantic
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Black carbon (BC) content in a sediment core from Daihai Lake, Inner Mongolia, was analyzed to reconstruct a high-resolution history of fires occurring in northern China during the Holocene and to ...examine the impacts of natural changes and human activities on the fire regime. The black carbon mass sedimentation rate (BCMSR) was disintegrated into two components: the background BCMSR and the BCMSR peak, with the BCMSR peak representing the frequency of fire episodes. Both the background BCMSR and the magnitude of the BCMSR peak display a close relation with the percentage of tree pollen from the same sediment core, suggesting that regional vegetation type would be a factor controlling the intensity of fires. The inferred fire-episode frequency for the Holocene exhibits two phases of obvious increases, i.e., the first increase from <5 to ∼10 episodes/1000 yrs occurring at 8200 cal. yrs BP when the vegetation of the lake basin shifted from grasses to forests and the climate changed from warm/dry to warm/humid condition, and the further increase to a maximum frequency of 13 episodes/1000 yrs occurring at 2800 cal. yrs BP when herbs and shrubs replaced the forests in the lake basin and the climate became cool/dry. Both increases in the fire frequency contradict the previous interpretation that fires occurred frequently in the monsoon region of northern China when steppe developed under the cold/dry climate. We thus suggest that human activities would be responsible for the increased frequencies of fires in the Daihai Lake region in terms that the appearance of early agriculture and the expansion of human land use were considered to take place in northern China at ca 8000 and 3000 cal. yrs BP, respectively.
► Black carbon record reveals a detailed Holocene fire history in Daihai Lake region. ► Fire frequency was initially low and then largely increased during middle Holocene. ► Fire regimes during the early Holocene were mainly controlled by fuel and climate. ► Fire became more frequent since the middle Holocene due to human fire use. ► Two phases of increase in fire frequency shows an important role of human in fires.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Land snail Δ47-derived temperature correlates well with growing season temperature.•Clumped temperatures of Cathaica are about 3 °C higher than those of Bradybaena.•A species-specific Δ47 transfer ...function is needed to reconstruct paleotemperature.•Body water δ18O of Bradybaena shows a robust correlation with rainfall δ18O in northern China.
Land snail fossils are abundantly distributed in geological deposits and their isotopic compositions provide a means to determine paleoclimatic changes. With the development of the clumped isotopes (Δ47) geothermometer, many efforts have been made in recent years to study clumped isotopes in land snail shell carbonate. Although there have been several recent attempts, there is, as yet, no empirical calibration function to convert land snail Δ47 to environmental temperature. Here, we systematically analyzed clumped isotopes (Δ47) of two common land snail species (Bradybaena and Cathaica) from China. Results showed that temperatures calculated using the Δ47 (T47) of both species did not correlate with the mean annual temperatures (MAT) at the study sites. However, the T47-MAT offset is negatively correlated to MAT, suggesting that land snails tend to add shell during the warmer months at colder sites or modulate their body temperature differently in colder regions. Meanwhile, clumped temperatures of Cathaica are 3.4 ± 1.5 °C higher than those of Bradybaena at 18 sites, indicating that a species-specific transfer function is needed to reconstruct paleotemperature using land snail clumped isotopes. After determining the proper duration of the growing season for land snails at different locations, we developed a Δ47-growth season temperature (GST) transfer function for the two species. The calibration function for Bradybaena land snails is expressed by a linear regression between 1/T2 and absolute Δ47 (R2 = 0.94): Δ47 = (0.0513 ± 0.0036) × 106/T2 + (0.0930 ± 0.0413), where Δ47 is expressed in ‰ and T in K. The calibration function for Cathaica is as follows (R2 = 0.80): Δ47 = (0.055 ± 0.011) × 106/T2 + (0.035 ± 0.129). The function for Cathaica was successfully applied to reconstruct mean summer (June-July-August) temperatures during the Last Glacial Maximum and modern times on the central Chinese Loess Plateau, based on Δ47 data of Cathaica sp. provided by Eagle et al (2013a). This testifies to the validity of the aforementioned constructed transfer function. In addition, the calculated δ18O of body water (δ18OBW) for Bradybaena showed a robust correlation with the δ18O of rainfall (δ18Op), particularly in northern China, which points to the potential to trace hydrological changes in the region. In contrast, Cathaica δ18OBW did not show a straightforward relation to δ18Op. This inter-species complexity warrants further study.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Constructing a new ecological stability index based on optimal equilibrium state.•Developing a systematic evaluation system for the impact of tidal flat reclamation.•Scientifically ...screened the current ecological stability of Jiangsu coastal wetlands.•Analyzing the impact and cumulative effect of reclamation on ecological stability.•Nature reserve has a positive effect on strengthening regional ecosystem stability.
Tidal flats have great potential to expand human living space and provide abundant resources. However, large-scale reclamation and development activities have had profound impacts on regional ecosystems, and it is important to grasp the comprehensive characteristics of the effects from a macro perspective. We selected the coastal area Jiangsu, China, as a typical area, and investigated the impact of reclamation on the coastal wetland system from the perspective of ecosystem services stability. The optimal equilibrium state was used as a benchmark and a stability deviation index (SDI) of ecosystem services was constructed by clarifying the connotation of stability. The stable state and evolution characteristics of ecosystems in different areas (coastal administrative areas, tidal flat areas, and Yancheng National Nature Reserve (YNNR)) were screened and evaluated. Based on the SDI, an overall ecological impact assessment system was developed, and the impact of tidal flat reclamation on ecological stability and its cumulative effects were quantified. The results showed that in the past 40 years, the overall ecological stability of Jiangsu coastal area was “Basically Stable (II)”, while that of the YNNR was “Weakly Stable (III)”. The impact of reclamation on the ecosystem stability of the coastal tidal flat area was significant, with a contribution rate of 73.5 %, and the threshold of stability transition in this area was reached when the reclamation amount was 1251.33 km2. The extent to which reclamation explained the stability variation in the core zone, buffer zone, and experimental zone of YNNR gradually decreased, indicating that the impact of reclamation was greater when strong protection measures were in place. The southern region will reach the maximum threshold of the cumulative effect of instability in 2072. This study provides ideas for the analysis of the comprehensive impact of reclamation on coastal wetland ecosystems, and can provide guidance for the efficient utilization and protection of tidal flats.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We measured the carbon isotope ratio of black carbon (BC) from the Daihai Lake sediment core (DH99a) in north-central China with an objective to examine the effectiveness and sensitivity of the δ13C ...values of BC (δ13CBC) as a potential indicator of terrestrial environmental changes. We first performed a statistical study on the available data regarding carbon isotope fractionation (CIF) during the conversion of C3 and C4 vegetation to BC and observed that the mean CIF for BC produced from C3 plants is −0.3‰, whereas that for BC from C4 plants is −1.7‰. This result provides a solid reference for reconstructing vegetation and environmental changes using the δ13CBC values. The δ13CBC record in the DH99a sediment core spanning the last ca 10,000years displayed large variations from −23.7‰ to −29.2‰, which suggests that C3 plants dominantly occupied the Daihai Lake region during the Holocene. The most negative δ13CBC peaks coincided with high values of tree percentages and grain sizes, which occurred under relatively wetter climatic conditions during the middle Holocene (ca 6500–3200cal.yrBP) and an interval between 1700 and 1350cal.yrBP. In contrast, the least negative δ13CBC values corresponded to low values of tree percentages and grain sizes during relatively drier phases of the early and late Holocene. The generally negative correlation of the δ13CBC values with the tree percentages and grain sizes was thought to reflect a negative correlation of the δ13CBC values with the monsoon precipitation. This correlation is consistent with the response of carbon isotope in modern C3 plants to precipitation in north China. Therefore, we developed a computational model to reconstruct the changes in annual precipitation over the Daihai Lake region using the δ13CBC values. The results indicated that the annual precipitation was highly variable, ranging from 170mm lower to 310mm higher than that at present during the middle Holocene, whereas the annual precipitation was generally ~70mm lower than that at present during the early and late Holocene. The general features of the inferred precipitation changes using the δ13CBC values are generally consistent with those reconstructed using pollen data of the same sediment core. Meanwhile, the δ13CBC values tend to register some extreme variations of monsoon precipitation, which were not reflected in the pollen assemblages. We conclude that the δ13CBC values in the Daihai Lake sediments may serve as a sensitive and reliable proxy for monitoring monsoon precipitation.
•BC carbon isotope reveals C3-dominated vegetation during Holocene in Daihai.•δ13C values of BC negatively correlate with tree percentages and grain sizes.•BC carbon isotope can serve as a reliable proxy of monsoon precipitation.•Inferred rainfall was highly variable during the middle Holocene.•Inferred rainfall was 70mm lower than that at present during the early and late Holocene.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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