Incidental Aquaculture in California's Rice Paddies: Red Swamp Crawfish

Introduction of the red swamp crawfish, Procambarus clarkii, into California and its diffusion throughout northern California's rice paddies created the conditions for an incidental aquaculture economy in a landscape devoted to irrigated grain production. For more than three decades, fishermen have harvested this prolific invader and sold their catch to Europe and the Gulf Coast. Since 2004, the diffusion of Vietnamese‐American seafood restaurants to California and nationally has created additional markets for red swamp crawfish.     

Book Review

Electronic Surveying and Navigation by Simon H. Laurila (New York: John Wiley &; Sons, 1976), 545 pages, hardcover, $25.00.     

Suburban gentrification? Examining the geographies of New Urbanism in Atlanta’s inner suburbs

Since the 1990s, Atlanta’s inner suburbs have experienced rising rates of poverty alongside growing racial/ethnic diversity. ? Meanwhile, on the built landscape, high-end (re)development projects incorporating New Urbanist features such as pedestrian accessibility, compact densities, and mixed land uses have become increasingly common. Although practitioners suggest that these developments promote social inclusivity and enhanced “livability,” individual cases suggest that some New Urbanist projects may be gentrifying underserved communities of color. This paper tests the extent of this concern by examining Atlanta's inner-suburban geographies of New Urbanism using a logit model. Results indicate that neighborhoods with older housing stock, more renters, lower incomes, lower rents relative to home prices, and higher Latino populations in close proximity to inner-suburban downtowns are most likely to be targeted for New Urbanist (re)development. Thus, despite the optimistic language, New Urbanism in this region appears to be serving as the inner-suburban face of gentrification.?     

TOPOCLIMATIC CONTROLS IN AN ALPINE FELLFIELD AND THEIR ECOLOGICAL SIGNIFICANCE

The interaction of topography and ambient atmospheric conditions and their combined effect on surface climate are studied in the alpine fellfield on Niwot Ridge, Colorado Front Range. Insolation, net shortwave and all-wave radiation, surface and air temperatures, ground heat flux, wind speed, and evapotranspiration are analyzed in order to characterize moisture and energy exchanges. The spatial pattern of daily energy and moisture fluxes is influenced more by cloud cover than topographic position. The daily radiation load is usually highest on east-facing slopes because clear mornings are commonly followed by cumulus development during midday and early afternoon. In the dominant westerly wind regime, wind speeds on east-facing slopes are lower than elsewhere. Strong insolation produces high rates of evapotranspiration from the thin, sandy/gravelly fellfield soil when moisture is abundant. After a few consecutive precipitation-free days, large radiation loads produce high surface temperatures, especially on east-facing slopes where wind speed and thus the sensible heat flux are small. During the 1985 summer drought period, the impact of hot, dry weather on plant water stress was most pronounced on east-facing slopes. The well-defined distribution of Dryas octopetala on Niwot Ridge, near the southern extent of its circumpolar range, is an example of the control of topoclimate over plant distribution owing to water stress during periods of drought The absence of Dryas from south-facing slopes does not correspond well with present topoclimatic patterns. The present distribution of Dryas may be a consequence of topoclimatic patterns throughout the middle of the last millennium when the summer climate in the Colorado Front Range was hotter and drier than today. Summer droughts then were probably more prolonged, and a combination of clearer days, lower wind speeds, or an increased frequency of northerly wind would have created more intense water stress on south-facing than east-facing slopes. [Key words: Topoclimate, alpine tundra, Dryas octopetala, energy balance.]     

Transience of channel head locations following disturbance

We used annual re‐surveys of two populations of channel heads affected by a severe wildfire in 2012 to monitor changes in channel head location with time following disturbance. Relative to channel heads in surrounding unburned areas, the median contributing drainage area of burned channel heads decreased by two orders of magnitude immediately after the fire, but then returned to values comparable to unburned areas within four years. We distinguish three types of channel heads. Permanent channel heads, which constitute 4% of the total population, occur in well‐developed swales in association with stable features such as bedrock outcrops: these channel heads appear to have been unaffected by the fire. Persistent channel heads, which are 40% of the total population, also occur within hillslope concavities, but the exact location of the channel head moves upslope and downslope through time in response to varying inputs of water and sediment. Transient channel heads form on straight and convex slopes immediately following disturbance, but disappear as regrowth of ground cover limits overland flow and sediment movement. The majority of the position changes for persistent and transient channel heads occurred abruptly when viewed as annual time steps. Copyright © 2017 John Wiley & Sons, Ltd.     

Exploring Landcare Effectiveness Using Organisational Theory

Landcare is an important example of the potential of state-sponsored participation to establish viable local organisations and contribute to rural development. In this paper, the authors discuss their research using organisational theory to explore Landcare effectiveness. Data were obtained from a mailed survey to Landcare groups in the state of Victoria during 1998. Levels of group activity were used as a surrogate measure of group effectiveness. Groups were ranked according to their level of activity to assess the impact of factors likely to affect group performance, the efficacy of program logic, and the extent groups were contributing to program goals. Survey data suggested key aspects of Landcare Program logic were sound. Examination of the membership and activity profiles of groups suggested 90 per cent of the respondent groups were making a worthwhile contribution to program goals. This research also confirmed the importance of factors identified by others as significant influences on organisational effectiveness: the importance of having clear goals, objectives and plans; resource availability; facilitation by an outside agency; access to a funded group co-ordinator; and communication between stakeholders. Unfortunately, there are critical, ongoing management issues surrounding many of these topics.     

Effects of hydrothermal alteration on Pb in the active PACMANUS hydrothermal field, ODP Leg 193, Manus Basin, Papua New Guinea: A LA-ICP-MS study

The conventional model of leaching volcanic rocks as a source of metals in a seafloor hydrothermal systems has been tested by examining the behavior of Pb and other trace elements during hydrothermal alteration. ODP Leg 193 drill sites 1188 (Snowcap) and 1189 (Roman Ruins) on Pual Ridge in the eastern Manus Basin offshore eastern Papua New Guinea provide a unique three-dimensional window into an active back-arc hydrothermal system. We investigate by means of a LA-ICP-MS microbeam technique the capacity of Pb to be leached from a host volcanic rock exposed to various types and intensities of alteration. Our results are in general agreement with previous studies that utilized bulk analytical techniques but provide a more detailed explanation of the processes.Fresh representative dacitic lavas from the Pual Ridge have an average whole rock Pb content of 5.2 ppm, an average interstitial glass Pb content of 5.6 ppm and an average plagioclase Pb content of 1.0 ppm. Altered matrix samples have highly variable Pb values ranging from 0 to 52.4 ppm. High Pb values in altered samples are associated with a low temperature chlorite and clay mineral assemblage, in some cases overprinted by a high temperature (up to 350 °C) silica-rich “bleaching” alteration. Only the most highly altered matrix samples have REE patterns that differ from the fresh Pual Ridge dacite. This may represent either different lava histories or alteration characteristics that have affected normally immobile REEs. Altered samples with the highest Pb values have similar REE patterns to those of the local unaltered lavas. They are compositionally similar to typical Pual Ridge dacites indicating a genetic relationship between the main regional volcanic suite and the subseafloor hydrothermally altered, Pb-enriched material.Relative loss/gain for Pb between the analyzed altered samples and a calculated precursor show a maximum relative gain of 901%. Samples with relative Pb gain from both drill sites are associated with lower temperature alteration mineral assemblages characterized by pervasive chloritization. The related lower temperature (220-250 °C) neutral to slightly acidic fluids have been ascribed by others to return circulation of hydrothermal fluids that did not interact with seawater. Because altered samples have a higher Pb content than the fresh precursor, leaching of fresh volcanic rocks cannot be the source of Pb in the hydrothermal systems.     

Reactive trace element enrichment in a highly modified, tidally inundated acid sulfate soil wetland: East Trinity, Australia

This study examines the abundance of trace elements in surface sediments of a former acid sulfate soil (ASS) wetland subjected to marine tidal inundation. Sediment properties of this highly modified study site are compared with those of an adjacent unmodified, intertidal mangrove forest. Whilst some trace elements (Al, Cd, Mn, Ni and Zn) were clearly depleted due to mobilisation and leaching in the previous oxic-acidic phase, other trace elements (As and Cr) displayed significant enrichment in the tidally inundated ASS. Many trace elements were strongly associated with the reactive Fe and acid volatile sulfide (AVS) fractions, suggesting that trace elements may be adsorbed to abundant reactive Fe phases or sequestered as sulfide minerals. These findings provide an important understanding of the fate and mobility of reactive iron, AVS and trace elements during tidal remediation of a formerly acidified Great Barrier Reef (GBR) catchment.     

The geological history of insect-related plant damage

Biological damage to plants is commonly found from the Devonian but occurs most commonly from the Cretaceous. Damage inflicted on plants whilst they were alive may trigger a pathological response involving the growth of abnormal tissues. Much of the damage is caused by arthropods, particularly insects. Whilst some damage is non-taxon specific, such as simple feeding traces, other damage, such as leaf mines, galls or bark boring, may reveal the co-evolution of host specific taxa and the timing of such interactions. Damaged plants, particularly from the Cretaceous and Tertiary are described and illustrated. The geological history of the evolution of insect-related plant damage is briefly reviewed. Increased variety in the pathological response of plants is seen from the Cretaceous with the evolution of the angiosperms and diversification of numerous insect groups.