Regional nutrient decrease drove redox stabilisation and metazoan diversification in the late Ediacaran Nama Group, Namibia

The late Ediacaran witnessed an increase in metazoan diversity and ecological complexity, marking the inception of the Cambrian Explosion. To constrain the drivers of this diversification, we combine redox and nutrient data for two shelf transects, with an inventory of biotic diversity and distribution from the Nama Group, Namibia (similar to 550 to similar to 538 Million years ago; Ma). Unstable marine redox conditions characterised all water depths in inner to outer ramp settings from similar to 550 to 547Ma, when the first skeletal metazoans appeared. However, a marked deepening of the redoxcline and a reduced frequency of anoxic incursions onto the inner to mid-ramp is recorded from similar to 547Ma onwards, with full ventilation of the outer ramp by similar to 542Ma. Phosphorus speciation data show that, whilst anoxic ferruginous conditions were initially conducive to the drawdown of bioavailable phosphorus, they also permitted a limited degree of phosphorus recycling back to the water column. A long-term decrease in nutrient delivery from continental weathering, coupled with a possible decrease in upwelling, led to the gradual ventilation of the Nama Group basins. This, in turn, further decreased anoxic recycling of bioavailable phosphorus to the water column, promoting the development of stable oxic conditions and the radiation of new mobile taxa.Peer reviewe

Adapting agricultural water use to climate change in a post-Soviet context: challenges and opportunities in southeast Kazakhstan

The convergence of climate change and post-Soviet socio-economic and institutional transformations has been underexplored so far, as have the consequences of such convergence on crop agriculture in Central Asia. This paper provides a place-based analysis of constraints and opportunities for adaptation to climate change, with a specific focus on water use, in two districts in southeast Kazakhstan. Data were collected by 2 multi-stakeholder participatory workshops, 21 semi-structured in-depth interviews, and secondary statistical data. The present-day agricultural system is characterised by enduring Soviet-era management structures, but without state inputs that previously sustained agricultural productivity. Low margins of profitability on many privatised farms mean that attempts to implement integrated water management have produced water users associations unable to maintain and upgrade a deteriorating irrigation infrastructure. Although actors engage in tactical adaptation measures, necessary structural adaptation of the irrigation system remains difficult without significant public or private investments. Market-based water management models have been translated ambiguously to this region, which fails to encourage efficient water use and hinders adaptation to water stress. In addition, a mutual interdependence of informal networks and formal institutions characterises both state governance and everyday life in Kazakhstan. Such interdependence simultaneously facilitates operational and tactical adaptation, but hinders structural adaptation, as informal networks exist as a parallel system that achieves substantive outcomes while perpetuating the inertia and incapacity of the state bureaucracy. This article has relevance for critical understanding of integrated water management in practice and adaptation to climate change in post-Soviet institutional settings more broadly

In market, mansion or mountain: Representations of disability in reading for the young in rural and urban contexts, 1850-1950

The Rousseauvian view of the countryside as a place of healing, both physical and psychological, has remained extraordinarily pervasive until the present day. This essay explores the changing representation of disability in rural and urban contexts in selected popular texts for the young in Europe, the USA and Australia, between 1850 and 1950, the ‘age of great cities’. Whilst also examining small towns, most earlier texts reiterate the concept of the city as physically damaging and the countryside as a place where miraculous cures might occur. This essay maps a shift from a representation of the countryside as a place for cure, to acknowledgement of the health benefits of cities, in terms of technical expertise and other facilities. From the late nineteenth century, these texts acknowledge the potential dangers of rural environments, but continue to reflect belief in the psychological benefits of the countryside into the 1950s

Studying the Stress Redistribution around the Longwall Mining Panel Using Passive Seismic Velocity Tomography and Geostatistical Estimation

Generally, knowledge of stress redistribution around the longwall panel causes a better understanding of the mechanisms that lead to ground failure, especially to rock bursts. In this paper, passive seismic velocity tomography is used to demonstrate the state of stress around the longwall mining panel. The mining-induced microseismic events were recorded by mounting an array of receivers on the surface, above the active panel. To determine the location of seismic events and execute the process of tomography, double difference method is employed as a local earthquake tomography. Since passive sources are used, the ray coverage is insufficient to achieve the quality images required. The wave velocity is assumed to be the regionalized variable and it is therefore estimated in a denser network, by using geostatistical estimation method. Subsequently, the three dimensional images of wave velocity are created and are sliced into the coal seam. These images clearly illustrate the stressed zones that they are appropriately in compliance with the theoretical models. Such compliance is particularly apparent in the front abutment pressure and the side abutment pressure near the tailgate entry. Movements of the stressed zones along the advancing face are also evident. The research conclusion proves that the combined method, based on double-difference tomography and geostatistical estimation, can potentially be used to monitor stress changes around the longwall mining panel continuously. Such observation could lead to substantial improvement in both productivity and safety of mining operations