A Holocene record of climate change,fire ecology and human activity from montane Flat Top Bog,Maui

A sediment core from a high-elevation bog on Maui in the Hawaiian Islands contains evidence for drier conditions between 9.4–5.8 kyr BP, followed by a wetter interval between 5.8–2.2 kyr BP, and a variable late Holocene. These precipitation changes may be a reflection of vertical displacements of the upper boundary of the mid-Pacific Trade Wind Inversion (TWI) cloud layer. Fires, probably volcanically ignited, occurred in the forests prior to human arrival. Polynesian activity in this high-elevation, remote site was apparently limited, with no pollen, charcoal, or sedimentological evidence for local anthropogenic disturbance. After European contact, grass fires increased and introduced plant species invaded the site. Values for Cd, Cu, Pb, and Zn in sediments throughout the Holocene indicate low trace-metal deposition from atmospheric particulates at the site, even in the twentieth century.This paper is one of a series of papers guest edited by Dr. Mark Brenner on tropical paleolimnology     

Geochemical processes in a Mediterranean Lake: a high-resolution study of the last 4,000 years in Zoñar Lake,southern Spain

High-resolution geochemical analysis of a 6-m-long sediment core from Zoñar Lake, southern Spain, provides a detailed characterization of major changes in lake and watershed processes during the last 4,000 years. Geochemical variables were used as paleolimnological indicators and complement Zoñar Lakes’s paleoenvironmental reconstruction based on sedimentological and biological proxies, which define periods of increasing allochthonous input to the lake and periods of dominant autochthonous sedimentation. Chemical ratios identify periods of endogenic carbonate formation (higher Ca/Al, Sr/Al and Ba/Al ratios), evaporite precipitation (higher S/Al, Sr/Al ratios), and anoxic conditions (higher Mo/Al, U/Th ratios and Eu anomaly). Higher productivity is marked by elevated organic carbon content and carbonate precipitation (Mg/Ca). Hydrological reconstruction for Zoñar Lake was based on sedimentological, mineralogical and biological proxies, and shows that lower lake levels are characterized by Sr-rich sediments (a brackish lake with aragonite) and S-rich sediments (a saline lake with gypsum), while higher lake levels are characterized by sediments enriched in elements associated with alumino-silicates (Al, K, Ti, Fe, trace and rare earth elements), reflecting fresher conditions. Geochemical indicators also mark periods of higher detrital input to the lake related to human activity in the watershed: (1) during the Iberian Roman Humid Period (650 BC–AD 300), around the onset of the Little Ice Age (AD 1400), during the relatively drier Post-Roman and Middle Ages (AD 800–1400), and over the last 50 years, due to mechanized farming practices. Heavy metal enrichment in the sediments (Cu and Ni) suggests intensification of human activities during the Iberian Roman Period, and the use of fertilizers during the last 50 years.     

A Long-Term Decrease of the Mid-Size Segmentation Lengths Observed in the He <Emphasis Type="SmallCaps">ii</Emphasis> (30.4 nm) Solar EUV Emission

Power spectra of segmentation-cell length (a dominant length scale of EUV emission in the transition region) from full-disk He?ii extreme ultraviolet (EUV) images observed by the Extreme ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO) and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) during periods of quiet-Sun conditions for a time interval from 1996 to 2015 were analyzed. The spatial power as a function of the spatial frequency from about 0.04 to 0.27 (EIT) or up to 0.48 (AIA) Mm^?1 depends on the distribution of the observed segmentation-cell dimensions – a structure of the solar EUV network. The temporal variations of the spatial power reported by Didkovsky and Gurman (Solar Phys. 289, 153, 2014) were suggested as decreases at the mid-spatial frequencies for the compared spectra when the power curves at the highest spatial frequencies of 0.5 pix^?1 were adjusted to match each other. This approach has been extended in this work to compare spectral ratios at high spatial frequencies expressed in the solar spatial frequency units of Mm^?1. A model of EIT and AIA spatial responses allowed us to directly compare spatial spectral ratios at high spatial frequencies for five years of joint operation of EIT and AIA, from 2010 to 2015. Based on this approach, we represent these ratio changes as a long-term network transformation that may be interpreted as a continuous dissipation of mid-size network structures to the smaller-size structures in the transition region. In contrast to expected cycling of the segmentation-cell dimension structures and associated spatial power in the spectra with the solar cycle, the spectra demonstrate a significant and steady change of the EUV network. The temporal trend across these structural spectra is not critically sensitive to any long-term instrumental changes, e.g. degradation of sensitivity, but to the change of the segmentation-cell dimensions of the EUV network structure.     

Comparison of the spatio-temporal dynamics of vegetation between the Changbai Mountains of eastern Eurasia and the Appalachian Mountains of eastern North America

The Changbai Mountains and the Appalachian Mountains have similar spatial contexts. The elevation, latitude, and moisture gradients of both mountain ranges offer regional insight for investigating the vegetation dynamics in eastern Eurasia and eastern North America. We determined and compared the spatial patterns and temporal trends in the normalized difference vegetation index (NDVI) in the Changbai Mountains and the Appalachian Mountains using time series data from the Global Inventory Modeling and Mapping Studies 3rd generation dataset from 1982 to 2013. The spatial pattern of NDVI in the Changbai Mountains exhibited fragmentation, whereas NDVI in the Appalachian Mountains decreased from south to north. The vegetation dynamics in the Changbai Mountains had an insignificant trend at the regional scale, whereas the dynamics in the Appalachian Mountains had a significant increasing trend. NDVI increased in 55% of the area of the Changbai Mountains and in 95% of the area of the Appalachian Mountains. The peak NDVI occurred one month later in the Changbai Mountains than in the Appalachian Mountains. The results revealed a significant increase in NDVI in autumn in both mountain ranges. The climatic trend in the Changbai Mountains included warming and decreased precipitation, and whereas that in the Appalachian Mountains included significant warming and increased precipitation. Positive and negative correlations existed between NDVI and temperature and precipitation, respectively, in both mountain ranges. Particularly, the spring temperature and NDVI exhibited a significant positive correlation in both mountain ranges. The results of this study suggest that human actives caused the differences in the spatial patterns of NDVI and that various characteristics of climate change and intensity of human actives dominated the differences in the NDVI trends between the Changbai Mountains and the Appalachian Mountains. Additionally, the vegetation dynamics of both mountain ranges were not identical to those in previous broader-scale studies.     

Distribution of the indigenous microorganisms and mechanisms of their orientational activation in Daqing Oilfield

The distribution of indigenous microorganisms was surveyed in Block 1 of Daqing Oilfield. Based on this survey, the indigenous microorganisms in the formation water were activated with different activator systems at the simulated stratum ecological environment. The changes of the number of bacteria of various physiological groups were determined during the process of activation. Also changes of pH value and composition of gas productions were analyzed at the end of culturing. The results showed that the selected block formation water contained a great number of saprophytic bacteria, hydrocarbon-oxidizing bacteria, fermentative bacteria, methane-producing bacteria and sulfate-reducing bacteria. Under the conditions that the growth of sulfate-reducing bacteria was controlled the block had the potential to enhance oil recovery by activating beneficial bacteria. The growth of sulfate-reducing bacteria can be inhibited through the activation of nitrate-reducing bacteria. The number of nitrate-reducing bacteria reached 10⁶–10⁷ cells/mL, but sulfate-reducing bacteria reached only 0–45 cells/mL in A system. Methane-producing bacteria can be activated by C, D activators. The relative content of biological methane in the light hydrocarbon gas reached 80% in C, D systems. B activator was conducive to the propagation of acid-producing bacteria, so that the pH value of the culture medium decreased from 7.5 to around 5.0. Hydrocarbon-oxidizing bacteria can be activated by various activator systems. There was low molecular light hydrocarbon in gas production according to the analysis of gas chromatograph. According to the content of methane and the number of methane-producing bacteria, methane only can be generated through activating methane-producing bacteria. By choosing different activator systems, various populations of indigenous microorganisms can be activated accordingly.     

Recent Trends in Geography Education in Louisiana

Geography at elementary and middle schools in Louisiana, USA., remains a social studies strand along with civics, economics, and history, with no state-required geography course at any level. But because schools may require more geography than the state standard, this research examines the extent to which K–12 students are exposed to geography in Louisiana, using an electronic survey and an interview with state department of education officials. Results suggest that geography remains underemphasized, but the 2011 implementation of new social studies standards, the Advanced Placement Human Geography course, and other initiatives offer promise for more geographically literate Louisiana citizens.     

Climatic and geographic factors affect ecosystem multifunctionality through biodiversity in the Tibetan alpine grasslands

Ecosystem multifunctionality(EMF), the simultaneous provision of multiple ecosystem functions, is often affected by biodiversity and environmental factors. We know little about how the interactions between biodiversity and environmental factors affect EMF. In this case study, a structural equation model was used to clarify climatic and geographic pathways that affect EMF by varying biodiversity in the Tibetan alpine grasslands. In addition to services related to carbon, nitrogen, and water cycling, forage supply, which is related to plantproductivity and palatability, was included in the EMF index. The results showed that 72% of the variation in EMF could be explained by biodiversity and other environmental factors. The ratio of palatable richness to all species richness explained 8.3% of the EMF variation. We found that air temperature, elevation, and latitude all affected EMF, but in different ways. Air temperature and elevation impacted the aboveground parts of the ecosystem, which included plant height, aboveground biomass, richness of palatable species, and ratio of palatable richness to all species richness. Latitude affected EMF by varying both aboveground and belowground parts of the ecosystem, which included palatable speciesrichness and belowground biomass. Our results indicated that there are still uncertainties in the biodiversity–EMF relationships related to the variable components of EMF, and climatic and geographic factors. Clarification of pathways that affect EMF using structural equation modeling techniques could elucidate the mechanisms by which environmental changes affect EMF.     

Structure of the inhomogeneities of the fields of temperature,wind, and humidity in the tropical tropopause layer and lower stratosphere over West Africa (Burkina Faso, 2006)

Data are presented on some structure parameters of mesoscale turbulence mechanisms playing a significant role in the troposphere-stratosphere exchange in the tropical tropopause layer and in the lower stratosphere. The data are obtained in the framework of the international aircraft AMMA experiment in Burkina Faso (West Africa) in August 2006.     

Partial derivatives of surface wave phase velocities for flat anisotropic models

Summary. Surface wave behaviour in flat anisotropic structures is first illustrated by performing an exact computation on a simple two-layer model. The variational procedure of Smith & Dahlen is then used to compute the partial derivatives of surface wave phase velocities with respect to the elastic parameters in more realistic earth models. Linear relationships between the partial derivatives for a general anisotropic structure and those for a transversely isotropic structure are derived. When considering waves propagating in a fixed direction, there are only four independent derivatives for Rayleigh waves, and two for Love waves. To avoid the lack of resolution in an inverse method, we propose to use physically constrained models. These results are illustrated by using a model with hexagonal symmetry and a symmetry axis oriented either vertically or horizontally. Quasi-Love- and quasi-Rayleigh-wave partial derivatives are computed for both axis orientations. Modes up to the second overtone and periods ranging between 45 and 130 s have been considered. Finally, anomalies of phase velocity are computed in an oceanic model made of 1/6 oriented olivine crystals with horizontal or vertical preferred orientations of the a -axis.