Long-term environmental change and shifts in the aquatic plant community of Jones Creek,Thousand Islands National Park,Ontario, Canada based on plant macrofossil analysis

Plant macrofossils and pollen were analyzed from sediment cores to identify long-term changes in the aquatic plant community of Jones Creek, Thousand Islands National Park, Ontario, Canada. Six sediment cores were recovered from Jones Creek in February 2014. One complete core and five top/bottom samples were analyzed for plant macrofossil abundance and diversity. Sediment analysis and ²¹⁰Pb dating confirmed a productive wetland throughout the core, dating back beyond 1883 AD. Jones Creek is currently dominated by thick stands of cattails, particularly the hybrid white cattail (Typha x glauca Godr). The relative abundance of Typha pollen began to increase in the late nineteenth and early twentieth century, reaching a relative abundance of nearly 40% in the modern day surface sediment. Common macrofossils recovered from the sediment record included seeds of Carex, Schoenoplectus, Najas, and Eleocharis. There is evidence that community composition, as recorded by the macrofossil record, has shifted in Jones Creek in response to human activities. In particular there has been a reduction in sedge species between historical and present day conditions as the wetland shifted from a sedge dominated wet-meadow wetland to a cattail dominated system. The results of our study indicate that future restoration efforts should be directed towards reintroducing native sedge species that were present prior to major changes in land-use that occurred in the St. Lawrence region throughout the nineteenth and twentieth centuries.     

Access to reeds and mat making in the lower Volta basin of Ghana

This paper explores the origins of pressures on reeds and sedges used for mat making in the lower Volta basin of Ghana, and their impact on the socially embedded system which dictates access to reed fields. Data for the study were collected through field work employing participatory rural appraisal methods in 18 communities, involving 152 mat weavers. The findings showed that the mat‐weaving industry has contributed immensely in providing poor women a means of livelihood but reed marshes in the basin have reduced in recent years due to hydrological changes in the area caused by the damming of the Volta upstream. The decline in the availability of reed is exerting immense pressure on this once freely available resource, thus inducing landlords to impose a price on the rights of entry into marshlands by reed collectors. The imposition of these charges affected the very people that the mat‐weaving industry is targeted to help. The study recommends the local and central government to play a more active role and civil society groups to broaden the livelihood base of women living in this region.     

Accessibility to food retailers and socio‐economic deprivation in urban New Zealand

The spatial locations of food retailers are considered to be an influential aspect of population consumption patterns. Such contextual relationships are often related to socio‐economic deprivation, with disparities in accessibility having important implications. This study used Geographic Information Systems and an Enhanced Two‐Step Floating Catchment Area model of spatial accessibility to further understand such relationships within urban areas of New Zealand. Findings, while mixed, indicate that there is generally increased accessibility to all food retailers in highly deprived areas. Understanding these socio–spatial relationships in local environments has important implications for policy initiatives, health outcomes and sustainable development.     

Imaging mantle transition zone thickness with SdS-SS finite-frequency sensitivity kernels

We invert differential SdS-SS traveltime residuals measured from stacked waveforms and finite-frequency sensitivity kernels for topography on the 410- and 660-km discontinuities. This approach yields higher resolution images of transition zone thickness than previous stacking methods, which simply average/smooth over topographic features. Apparent structure measured using simple stacking is highly dependent upon the bin size of each stack. By inverting for discontinuity topography with a variety of bin sizes, we can more accurately calculate the true structure. The inverted transition zone model is similar to simple stack models with an average thickness of 242 km, but the lateral variations in thickness are larger in amplitude and smaller in scale. Fast seismic velocities in 3-D mantle models such as SB4L18 correlate with areas of thicker transition zone. The elongated curvilinear regions of thickened transition zone that occur near subduction zones are narrow and high amplitude, which suggests relatively little lateral spreading and warming of subducted lithosphere within the transition zone. The anomalously thin transition zone regions are laterally narrow, and not broadly continuous. If these variations in transition zone thickness are interpreted as thermal in nature, then this model suggests significant temperature variations on small lateral scales.     

Deciphering the Origin of Abiotic Organic Compounds on Earth: Review and Future Prospects

The geologic production of abiotic organic compounds has been the subject of increasing scientific attention due to their use in the global carbon flux balance, by chemosynthetic biological communities, and for energy resources. Extensive analysis of methane(CH₄) and other organics in diverse geologic settings, combined with thermodynamic modelings and laboratory simulations, have yielded insights into the distribution of specific abiotic organic molecules on Earth and the favorable c...     

Using fire regimes to delineate zones in a high-resolution lake sediment record from the western United States

Paleoenvironmental reconstructions are important for understanding the influence of long-term climate variability on ecosystems and landscape disturbance dynamics. In this paper we explore the linkages among past climate, vegetation, and fire regimes using a high-resolution pollen and charcoal reconstruction from Morris Pond located on the Markagunt Plateau in southwestern Utah, USA. A regime shift detection algorithm was applied to background charcoal accumulation to define where statistically significant shifts in fire regimes occurred. The early Holocene was characterized by greater amounts of summer precipitation and less winter precipitation than modern. Ample forest fuel and warm summer temperatures allowed for large fires to occur. The middle Holocene was a transitional period between vegetation conditions and fire disturbance. The late Holocene climate is characterized as cool and wet reflecting an increase in snow cover, which reduced opportunities for fire despite increased availability of fuels. Similarities between modern forest fuel availability and those of the early Holocene suggest that warmer summers projected for the 21st century may yield substantial increases in the recurrence and ecological impacts of fire when compared to the fire regime of the last millennium.     

Algorithms for GPS operation indoors and downtown

The proliferation of mobile devices and the emergence of wireless location-based services has generated consumer demand for availability of GPS in urban and indoor environments. This demand calls for enhanced GPS algorithms that accommodate high degrees of signal attenuation and multipath effects unique to the "urban channel." This paper overviews the market for location-based services and discusses algorithmic innovations that address challenges posed by urban environments. Electronic Publication     

Tracking a Governance Transition: Identifying and Measuring Indicators of Social Forestry on the Willamette National Forest

Abstract

National Forests in the United States have undergone a spatially and temporally uneven governance transition in response to social and economic pressures and contemporary policy changes, with many national forest units moving from a wholly government-led “dominant federal” model to a more collaborative “social forestry” model in which nonfederal actors have greater influence and authority. Here we report on an effort to develop a suite of indicators designed to capture some of the most tangible elements of a transition from dominant federal to social forestry modes of governance. We pilot test these data on the Willamette National Forest using data from a variety of sources internal and external to the USDA Forest Service. We assess the suitability of these indicators for tracking governance transitions and discuss their applicability to other national forest units nationwide.     

On amplitude information carried by the ambient seismic field

The use of the ambient seismic field (ASF) to extract Earth's response has received significant attention in the last several years. Multiple studies demonstrate the utility of the ASF for estimating high-resolution velocity models in various locations. In this paper, we discuss the amplitude information carried by the ASF. Amplitude information includes both amplification effects due to elastic structure, such as low velocity sedimentary basins, and attenuation effects in the crust and upper mantle or even in buildings. As has been suggested by other authors, amplitude measurements may be biased due to non-uniformities in ambient field excitation; however, we find very similar and stable results for different time intervals for both amplification and attenuation, suggesting that this bias may not be as large as feared. We conclude that valuable amplitude information can be recovered from the ASF through careful processing. Amplitude measurements may be particularly valuable due to the enhanced sensitivity of attenuation to fluids and/or temperature fluctuations.