Elm bark beetle in Holocene peat deposits and the northwest European elm decline

The elm decline of 5000 ¹⁴C yr ago has been the most widely discussed phenomenon in post‐glacial vegetation history. This pan‐European reduction of elm populations, echoed in the decimation of elmwoods in Europe during the twentieth century, has attracted a series of interrelated hypotheses involving climate change, human activity, disease and soil deterioration. The elm bark beetle (Scolytus scolytus L.) is an essential component of disease explanations. We present evidence for the presence of the beetle over a prolonged period (ca. 7950–4910 yr BP [8800–5660 cal. yr BP]) from a lowland raised mire deposit in northeast Scotland, with its final appearance at this site, and the first and only appearance in another mire of a single scolytid find, around the time of the elm decline. The subfossil S. scolytus finds are not only the first from Scotland, but they also represent the most comprehensive sequence of finds anywhere. Copyright © 2004 John Wiley & Sons, Ltd.     

China’s rural revitalization and development: Theory,technology and management

Journal of Geographical Sciences - The urban-rural transformation from dichotomy to integration is a gradual process. Like rural areas in many countries, Chinese rural society is experiencing a...     

贺兰山中元古代三个叠层石组合及其地层意义

贺兰山原划归蓟县系王全口群中、下部的碳酸盐岩中新建立了两个叠层石组合 ,即下部以 Colonnella sp.、Gaoyuzhuangia sp.、Conophyton garganicum、C.cf.cylindricum等锥叠层石和块茎状柱叠层石为代表的闵家沟组合 ,其属种和总体面貌与长城系高于庄叠层石组合较为相似 ;中部以 L ochmecolumella和 Pseudogymnosolen等微小类型叠层石为代表的冰沟叠层石组合 ,其特征与蓟县系雾迷山叠层石组合完全一致。同时通过对王全口组叠层石分子的全面分析 ,判定王全口叠层石组合的时代应是蓟县纪中、晚期 ,其底界不低于雾迷山组底部。据此 ,重新厘定了贺兰山地区中元古代地层划分。     

Famennian microbial reef facies, Napier and Oscar Ranges, Canning Basin, western Australia

Following the Frasnian–Famennian mass extinction, which eliminated most skeletal reef-building fauna, the early Famennian reefs of the Canning Basin were constructed primarily by reef-framework microbial communities. In the Napier and Oscar Ranges, the Famennian reef complexes had high-energy, reef-flat depositional environments on a reef-rimmed platform that transitioned into low-energy, deep-water reefs growing in excess of 50 m below sea level. High-energy, reef-flat depositional environments contain doming fenestral stromatolites that grade into porous thrombolites and are associated with coarse-grained sandstones and grainstones. The reef-margin subfacies contains mounds of microdigitate thrombolites, which are more delicate than the reef-flat thrombolites and locally contain abundant red algae, Girvanella, renalcids and sediment-filled tubes. Within the thrombolites, the red algae are in upright growth positions, suggesting that the thrombolites are largely composed of carbonate that precipitated in situ. Reefal-slope environments are dominated by Wetheredella and Rothpletzella with locally abundant Girvanella, renalcids and Uralinella. In reefal-slope strata, delicate fans and microdigitate stromatolites of Wetheredella and Rothpletzella are often oriented horizontal or diagonal to bedding and are interpreted as syndepositionally toppled over. Most mesoscale microbial community structures contain several species of microbial fossils, and no single microbial species appears to have controlled the morphology of the community structure. Therefore, the depositional environment must have determined the distribution and morphology of the stromatolites, thrombolites and other microbial community structures. The adaptability of microbial communities to various reef environments allowed them to fill ecological niches opportunistically after the Frasnian–Famennian mass extinction.     

Abiotic versus biotic controls on the development of the Fairmont Hot Springs carbonate deposit, British Columbia, Canada

The relict Fairmont Hot Springs deposit, formed largely of carbonates, covers an area of 0·5 km², and is up to 16 m thick. The triangle‐shaped discharge apron, which broadens down‐valley, is divided into a proximal part with beds dipping at <10° and a distal part with beds dipping at 10° to 15°. The deposit is formed of the: (1) Basal Macrophyte; (2) Lower Carbonate; (3) Middle Clastic; (4) Upper Carbonate; and (5) Upper Clastic Sequences. Two charcoal samples embedded in the Lower Carbonate Sequence yielded dates of 8690 ± 90 and 8270 ± 70 cal yr bp , indicating that much of the deposit formed post‐glacially during the Early to Mid‐Holocene. Deposit aggradation ceased in the Mid to Late Holocene when the Fairmont Creek valley was incised. The Lower and Upper Carbonate Sequences, which are the thickest sequences, are composed of nearly equal parts of travertine (abiotic) and tufa (biotic), with feather dendrite travertine, radiating dendrite travertine and stromatolite tufa dominating. Competition between calcite precipitation rates and biotic growth rates controlled the distribution of tufa and travertine across the discharge apron. Calcite and biotic growth rates were controlled largely by flow velocity across the apron which, in turn, was controlled by topography and regular fluctuations in spring water discharge volume. During times of high spring discharge, slow sheet flow over the proximal part of the apron promoted stromatolite growth, whereas fast, turbulent flow on the distal part of the apron induced rapid feather dendrite formation. During times of low spring discharge, quiescent, shallow evaporative pools, conducive to radiating dendrite formation, formed on the proximal part of the apron, whereas slow flow on the distal part promoted stromatolite growth. Facies with high calcite supersaturation experienced rapid abiotic dendrite growth that precluded most biotic growth.     

A method to predict the group fissuring and faulting caused by regional groundwater decline

Ground fissuring is a recurrent problem in many countries where water extraction surpasses the natural recharge of aquifers. Due to differential settlement, the soil layer undergoes deformation and cracks with serious consequences for civil infrastructure. Here, we propose an approximate analysis of the fissuring process that can be used to predict the location of cracks, which increasingly affect some middle- and large-sized cities in the world. For that purpose, the ground loss theory is applied to sediments overlying a sinusoidal-shaped graben. This analysis shows the existence of a tensile zone at the border of the graben with maximal values on its shoulder where tension cracks are more likely to appear. It also shows that soil deformation under differential settlement may evolve into ground faulting if water withdrawal continues. Finally, when a crack has completely developed, the tensile zone shifts towards the center of the graben, creating a new area for potential cracking and faulting.     

Influence of anthropogenic pressure and seasonal upwelling on coral reefs in Nha Trang Bay (Central Vietnam)

The growing coastal development, dredging and dumping activities, overfishing and expansion of marine cage culture in Nha Trang Bay (NTB) of Central Vietnam since the beginning of the 2000s have resulted in a dramatic decrease of live coral cover. Surveys conducted in April–May 2013 and the same period in 2014 revealed that with an increase in distance from the outer part of the bay towards the mainland, the rivers’ influxes and dredged areas, coral cover decreased from 75% to 0.6% and species richness from 63 to 5, while the abundance of macroalgae increased from 0% to 56%. These changes correlate with differences in the concentration of suspended sediments on the same gradient. The abundance of the crown‐of‐thorns starfish Acanthaster planci and of the echinoid Diadema setosum significantly increased between the first estimation in 1998 and the survey in 2014, from 0 to 1.7 individuals (ind.) per 100 m^?2 and from 50.8 to 94.5 ind. per 100 m^?2, respectively, contributing to coral loss and intensive bioerosion of the reef framework in the bay. The large sizes of adult colonies of tabulate Acropora on the remote stations with negligible sedimentation and eutrophication loads were inconsistent with the assumptions that temperature‐induced coral bleaching or cyclones could be the major impacts in Nha Trang Bay. Analysis of the 16‐year thermal history of the bay did not reveal any instances in which the coral thermal bleaching threshold had been exceeded up to the present study. Seasonal upwelling, which occurs annually in the vicinity of Central Vietnam, may contribute to mitigation of thermal anomalies within NTB and to the maintenance of healthy coral communities on the remote reefs with relatively low anthropogenic impact.     

Soil quality changes in land degradation as indicated by soil chemical, biochemical and microbiological properties in a karst area of southwest Guizhou, China

Not only the nutritional status and biological activity but also the soil ecological functioning or soil health has been impacted profoundly by land degradation in the karst area of southwest China where the karst ecosystems are generally considered as extremely vulnerable to land degradation under intensified land-use changes. The objectives of this study are to elucidate the changes in overall soil quality by a holistic approach of soil nutritional, biological activity, and soil health indicators in the karst area as impacted by intense cultivation and vegetation degradation. Topsoil samples were collected on selected eco-tesserae in a sequence of land degradation in a karst area of southwest Guizhou in 2004. The soil nutrient pools of organic carbon (C_org), extractable extracellular carbon (C_ext), total soil nitrogen (N_t), alkali-hydrolyzable nitrogen (N_ah), total phosphorus (P_t), available phosphorus (P_a) were analyzed by wet soil chemistry. The soil biological properties were studied by means of measurements of microbial biomass carbon (both by fumigation–extraction, FE-C_mic, and by calculation from substrate-incubation respiration, SIR-C_mic) of respiration [respiration without addition of substrates, basal respiration (BR), and potential respiration (PR) with substrate-incubation] and of soil enzyme activities (invertase, urease, and alkaline phosphatase). Soil health status was assessed by simple indices of C_mic/C_org and BR/C_mic in conjunction with bacterial community structures determined by polymerase chain reaction and denaturing gradient gel electrophoresis. While the nutritional pool parameters, such as C_org and C_ext, described basically the changes in soil life-supporting capacity with cultivation interference and vegetation declined, those parameters of biological activity such as FE-C_mic, SIR, and SIR-C_mic as well as bacterial community structures measured by molecular method evidenced well the changes in soil functioning for ecosystem health with the land degradation.     

海水温度对衰亡期浒苔释放生源硫影响的模拟研究

为研究浒苔释放生源硫的特征,本文对采集于黄海绿潮中期和末期的浒苔进行了实验室模拟培养,探讨了不同温度对衰亡期浒苔释放生源硫化物的影响。实验结果表明,在10~25℃温度范围内,温度升高能够加速浒苔的衰亡。二甲基硫（DMS）的平均释放速率范围为2.79~150.70 nmol/（L·g·d）,二甲基硫基丙酸内盐（DMSP）的平均释放速率范围为2.16~113.26 nmol/（L·g·d）。温度升高能够使DMS和DMSP的释放速率加快,释放量增加,DMS最大平均释放速率在25℃条件下比10℃条件下升高了约60%,培养液中DMS浓度升高了2~3倍。采集于绿潮末期的浒苔培养液中的DMS和DMSP和采集于绿潮中期的浒苔相比,浓度有所增加,采集于浒苔绿潮末期浒苔培养液中DMS的最高平均浓度为418.41 nmol/L,约为中期的4倍;DMSP的最高平均浓度为316.14 nmol/L,是中期的3倍。浒苔绿潮的爆发会对水体中的硫体系循环产生影响,进而影响该海域生态环境。