Coronal magnetic structure at a solar sector boundary

The persistent large-scale coronal magnetic structure associated with a sector boundary appears to consist of a magnetic arcade loop structure extending from one solar polar region to the other in approximately the north-south direction. This structure was inferred from computed coronal magnetic field maps for days on which a stable magnetic sector boundary was near central meridian, based on an interplanetary sector boundary observed to recur during much of 1968 and 1969.     

Long-Term Trends in Submersed Aquatic Vegetation (SAV) in Chesapeake Bay, USA, Related to Water Quality

Chesapeake Bay supports a diverse assemblage of marine and freshwater species of submersed aquatic vegetation (SAV) whose broad distributions are generally constrained by salinity. An annual aerial SAV monitoring program and a bi-monthly to monthly water quality monitoring program have been conducted throughout Chesapeake Bay since 1984. We performed an analysis of SAV abundance and up to 22 environmental variables potentially influencing SAV growth and abundance (1984–2006). Historically, SAV abundance has changed dramatically in Chesapeake Bay, and since 1984, when SAV abundance was at historic low levels, SAV has exhibited complex changes including long-term (decadal) increases and decreases, as well as some large, single-year changes. Chesapeake Bay SAV was grouped into three broad-scale community-types based on salinity regime, each with their own distinct group of species, and detailed analyses were conducted on these three community-types as well as on seven distinct case-study areas spanning the three salinity regimes. Different trends in SAV abundance were evident in the different salinity regimes. SAV abundance has (a) continually increased in the low-salinity region; (b) increased initially in the medium-salinity region, followed by fluctuating abundances; and (c) increased initially in the high-salinity region, followed by a subsequent decline. In all areas, consistent negative correlations between measures of SAV abundance and nitrogen loads or concentrations suggest that meadows are responsive to changes in inputs of nitrogen. For smaller case-study areas, different trends in SAV abundance were also noted including correlations to water clarity in high-salinity case-study areas, but nitrogen was highly correlated in all areas. Current maximum SAV coverage for almost all areas remain below restoration targets, indicating that SAV abundance and associated ecosystem services are currently limited by continued poor water quality, and specifically high nutrient concentrations, within Chesapeake Bay. The nutrient reductions noted in some tributaries, which were highly correlated to increases in SAV abundance, suggest management activities have already contributed to SAV increases in some areas, but the strong negative correlation throughout the Chesapeake Bay between nitrogen and SAV abundance also suggests that further nutrient reductions will be necessary for SAV to attain or exceed restoration targets throughout the bay.     

Optically stimulated luminescence dating of late Holocene raised strandplain sequences adjacent to Lakes Michigan and Superior, Upper Peninsula, Michigan, USA

This study evaluates the accuracy of optically stimulated luminescence to date well-preserved strandline sequences at Manistique/Thompson bay (Lake Michigan), and Tahquamenon and Grand Traverse Bays (Lake Superior) that span the past ∼4500 yr. The single aliquot regeneration (SAR) method is applied to produce absolute ages for littoral and eolian sediments. SAR ages are compared against AMS and conventional ¹⁴C ages on swale organics. Modern littoral and eolian sediments yield SAR ages <100 yr indicating near, if not complete, solar resetting of luminescence prior to deposition. Beach ridges that yield SAR ages <2000 yr show general agreement with corresponding ¹⁴C ages on swale organics. Significant variability in ¹⁴C ages >2000 cal yr B.P. complicates comparison to SAR ages at all sites. However, a SAR age of 4280 ± 390 yr (UIC913) on ridge77 at Tahquamenon Bay is consistent with regional regression from the high lake level of the Nipissing II phase ca. 4500 cal yr B.P. SAR ages indicate a decrease in ridge formation rate after ∼1500 yr ago, likely reflecting separation of Lake Superior from lakes Huron and Michigan. This study shows that SAR is a credible alternative to ¹⁴C methods for dating littoral and eolian landforms in Great Lakes and other coastal strandplains where ¹⁴C methods prove problematic.     

Interplanetary sector structure, 1962–1966

Some properties of the interplanetary magnetic field observed by IMP-3 in the latter half of 1965 are discussed with relation to previous satellite observations of the interplanetary field. The sector property remains a prominent feature of the observations, with the average field direction at the Archimedes spiral angle. The sector pattern has a 27-day recurrence period from 1962 to 1964, and during the year 1964 the pattern appears to be quasi-stable. In 1965 the recurrence period is about 28 days, and the evolution of the pattern is more rapid, with new sectors appearing and expanding.     

An observational search for large-scale organization of five-minute oscillations on the Sun

The large-scale solar velocity field has been measured over an aperture of radius 0.8 R on 121 days between April and September, 1976. Measurements are made in the line Fei 5123.730 Å, employing a velocity subtraction technique similar to that of Severny et al. (1976). Comparisons of the amplitude and frequency of the five-minute resonant oscillation with the geomagnetic C9 index and magnetic sector boundaries show no evidence of any relationship between the oscillations and coronal holes or sector structure.     

Land Use and Salinity Drive Changes in SAV Abundance and Community Composition

Conserving and restoring submerged aquatic vegetation (SAV) are key management goals for estuaries worldwide because SAV integrates many aspects of water quality and provides a wide range of ecosystem services. Management strategies are typically focused on aggregated abundance of several SAV species, because species cannot be easily distinguished in remotely sensed data. Human land use and shoreline alteration have been shown to negatively impact SAV abundance, but the effects have varied with study, spatial scale, and location. The differences in reported effects may be partly due to the focus on abundance, which overlooks within-community and among-community dynamics that generate total SAV abundance. We analyzed long-term SAV aerial survey data (1984–2009) and ground observations of community composition (1984–2012) in subestuaries of Chesapeake Bay to integrate variations in abundance with differences in community composition. We identified five communities (mixed freshwater, milfoil-Zannichellia, mixed mesohaline, Zannichellia, and Ruppia-Zostera). Temporal variations in SAV abundance were more strongly related to community identity than to terrestrial stressors, and responses to stressors differed among communities and among species. In one fifth of the subestuaries, the community identity changed during the study, and the probability of such a change was positively related to the prevalence of riprapped shoreline in the subestuary. Mixed freshwater communities had the highest rates of recovery, and this may have been driven by Hydrilla verticillata, which was the single best predictor of SAV recovery rate. Additional species-specific and community-specific research will likely yield better understanding of the factors affecting community identity and SAV abundance, more accurate predictive models, and more effective management strategies.     

Fluvial sediment supply and pioneer woody seedlings as a control on bar‐surface topography

Plants influence river channel topography, but our understanding of the interaction among plants, flow, and sediment is limited, especially when sediment supply is variable. Using laboratory experiments in a recirculating flume with live seedlings in a mobile sand bed, we demonstrate how varying the balance between sediment supply and transport capacity shifts the relationship between plants and bar‐surface topography. Each experimental trial contrasted two sediment conditions, in which initially supply was maintained in equilibrium with transport via sediment recirculation, followed by sediment deficit, in which transport capacity exceeded supply, which was set to zero. For both sediment balances, the topographic response was sensitive to plant size, with larger plants inducing greater aggradation relative to a baseline condition. During sediment equilibrium, the positive relationship between plant size and topographic change also depended on species morphology (multi‐stemmed shrubs versus single‐stemmed plants). Plant morphology effects disappeared when the sediment balance shifted to a deficit, but the presence of plants had a greater impact on the magnitude of change compared to the topographic response under sediment equilibrium. Our results suggest that the interactions among sediment supply, plants, and topography may be strongest on rivers with a balance in sediment supply and transport capacity. Because of the large variability in fluvial sediment supply resulting from natural and anthropogenic influences, these interactions will differ spatially (e.g. longitudinally through a watershed) and at different temporal scales, from single flood events to longer time periods. Copyright © 2016 John Wiley & Sons, Ltd.     

Stakeholder objective preferences in Australian Commonwealth managed fisheries

Fisheries management is increasingly involving a wide range of stakeholders in the decision making process. However, in most fisheries, the set of management objectives are poorly defined, and the implicit importance placed on these objectives may vary considerably both between and within different stakeholder groups. This may lead to conflicts within management advisory groups where members from different stakeholder groups view potential management outcomes substantially differently, and inconsistencies in decision making when changes in stakeholder representation take place. In this paper, the institutional structure of fisheries management in Australia and the roles the different organisations play in shaping fisheries management plans are detailed. An explicit hierarchy of management objectives is developed in collaboration with key managers and policy makers. A large survey of stakeholders involved in Australian Commonwealth fisheries management was undertaken to determine stakeholder preferences relating to these objectives. The results highlight the differences in perspectives regarding the relative importance of the multiple objectives of fisheries management. While on average stakeholder preferences generally correspond with their expected preference set, the results also indicate that there is generally low coherence within stakeholder groups.     

Studies of a regulated dryland river: surface–groundwater interactions

Unlike rivers in humid regions, dryland rivers typically exhibit reduced flow in the downstream direction as a result of transmission losses, which include seepage of streamflow into the aquifer, evaporation, and transpiration. However, much remains to be learned about the nature of the exchange between surface water and groundwater in these landscapes, especially in terms of spatial and temporal variability. Our study focused on streambank seepage and groundwater flow in the alluvial aquifer, specifically on answering questions such as: Is there seasonal variability in seepage losses? Is seepage permanently lost? Can losses be reduced by killing riparian vegetation? To better understand the magnitude, variability, and fate of streambank seepage, we assessed river stages, groundwater hydraulic gradients, and groundwater flow paths at two sites along a reach of the Pecos River, a dryland perennial river in West Texas. We found that along this reach the river was losing water to the aquifer even under low‐flow conditions; but seepage was controlled by a number of different mechanisms. Seepage increased not only during high‐flow events but also when the groundwater level was declining owing to long periods of no irrigation release. Tamarix (saltcedar) control did not affect hydraulic gradients nor reduce streambank seepage and given that this reach of the Pecos River is a losing one, streamflow will not be enhanced by controlling saltcedar. These findings can be used to improve basic conceptual models of dryland river systems and to predict hydrologic responses to changes in the timing and magnitude of streamflows and to riparian vegetation management. Copyright © 2012 John Wiley & Sons, Ltd.     

Savage Jaguars,King Cats,and Ghostly Tigres: Affective Logics and Predatory Natures in Twentieth-Century American Nature Writing

The emerging subfield of historical animal geography provides an opportunity to trace the origins and evolutions of how affective logics framing the conservation of an animal species are co-constituted through embodied interaction between humans and nonhumans, revealing the dynamic ways in which charismatic species are imagined into and out of positions of priority within conservation agendas. This article takes an interest in the shifting perception of predatory species in the environmental conservation movement in the United States, looking to the appearance of jaguars (Panthera onca) in the work of prominent U.S. nature writers Theodore Roosevelt, Ernest Thompson Seton, and Aldo Leopold in the early- to mid-twentieth century. These human–jaguar entanglements reveal a period marked by dynamic changes in the ways in which interspecies encounters were constituted in place; a layering on of affective logics that reveal the complicated origins, practices, and potentialities at the outset of the modern conservation movement. The resulting narratives and images of predatory nature were taken up into dynamic assemblages of jaguar-ness, influencing the formation of new logics that framed public perceptions of predatory natures and provoking a reconsideration of long-held attitudes and policies toward these species.