Water sources of urban trees in the Los Angeles metropolitan area

In semi-arid cities, urban trees are often irrigated, but may also utilize natural water sources such as groundwater. Consequently, the sources of water for urban tree transpiration may be uncertain, complicating efforts to efficiently manage water resources. We used a novel approach based on stable isotopes to determine tree water sources in the Los Angeles basin, where we hypothesized that trees would rely on irrigation water in the soil rather than develop deep roots to tap into groundwater. We evaluated the oxygen (δ¹⁸O) and hydrogen (δD) isotope ratios of xylem water, irrigation water, soil water, and groundwater in a study of temporal patterns in water sources at two urban sites, and a study of spatial patterns at nine urban sites and one “natural” riparian forest. Contrary to our hypothesis, we found that despite frequent irrigation, some trees tap into groundwater, although in most species this was a small water source. Some trees appeared to be using very shallow soil water at <30 cm depth, suggesting that these mature urban trees were quite shallowly rooted. In the natural site, trees appeared to be using urban runoff in addition to shallow soil water. We were able to identify tree uptake of precipitation at only 3 sites. The results show that some irrigated trees utilize groundwater and do not rely solely on irrigation water, which may make them able to withstand drought and/or water conservation measures. However, some irrigated trees may develop very shallow root systems, which may make them more susceptible.     

Monstrosities and moral publics

Interdisciplinary scholarship on neoliberal urban governmentality has been attentive to the knowledges and techniques of government currently emerging at the interface of local state politics and invested claims of voluntary private actors such as corporate partners and philanthropic agencies. This article draws attention to the workings of the aesthetic as an epistemological grounding for the rationalization of urban rule. Specifically, I explore a Toronto, Canada-based philanthropic agency’s reliance on a mise-en-scene of urban terror to animate its own self-validated knowledges about targeted inner-suburban subjects and spaces. In their circulation and demand for public address, the agency’s graphic public service announcements, launched in 2007, herald what I argue is a moralized set of knowledges about municipal renewal that has its own normative orientations grounded in a neoliberal political rationality, and tangentially, in racialized security imperatives. I detail various dimensions of the social life of a video associated with this public service campaign targeting ‘youth at risk’, considering the ethical, political and economic valences it was expected to convey; its semiotic exchange with other images and representations of disenfranchised spaces, subjects and communities; and the publics it attempted to interpellate. Importantly, given the agency’s current standing as a prominent player in Canadian urban policy arenas, I pay analytical attention to the visual campaign as a site for the production of knowledges about proper urban citizenship and social governance, and as such, a strategic-orienting device for urban policy interventions and directives.     

THE UNCERTAIN FUTURE OF IDEOLOGY: Rereading Marx

Throughout its history, "ideology" (the concept and theory) served as social science's foil, an opposing standard against which it defined its own knowledge-as-truth. As social science since mid-century has undergone changes in its idea of itself and its methods of inquiry, the theory of ideology has served as register, visably recording these changes. Works by the structuralists and poststructuralists, especially Althusser and Foucault, forced upon social theorists a profound rethinking of power and its operations and moved "ideology" away from the theory of false consciousness towards a view of ideology as cultural practice. For some, ideology theory is obsolete (due to its classical roots as "false consciousness") or redundant (due to its links to "culture"). Despite the merits of these arguments, a provisional argument on behalf of ideology theory is offered.

Marxism, after drawing us to it as the moon draws the tides, after transforming all our ideas, after liquidating the categories of our bourgeois thought, abruptly left us stranded.

—Jean-Paul Sartre     

Resumenes

Spanish translations by Elena Immamb?cous.     

Understanding preferences for tree attributes: the relative effects of socio-economic and local environmental factors

Urban plant biodiversity is influenced by both the physical environment and attitudes and preferences of urban residents for specific plant types. Urban residents are assumed to be disconnected from their immediate environment, and cultural and societal factors have been emphasized over environmental factors in studies of landscaping choices. However, we postulate that local climatic and environmental factors can also affect preferences for plant attributes. Therefore, spatial and temporal patterns in urban tree biodiversity may be driven not only by the direct effect of environmental variables on plant function, but also by the effect of environmental variables on attitudes toward trees and associated choices about which types of trees to plant. Here, we tested the relative effects of socio-economic and local environmental factors on preferences toward tree attributes in five counties in southern California in and surrounding Los Angeles, based on 1,029 household surveys. We found that local environmental factors have as strong an effect on preferences for tree attributes as socio-economic factors. Specifically, people located in hotter climates (average maximum temperature 25.1 °C) were more likely to value shade trees than those located in cooler regions (23.1 °C). Additionally, people located in desert areas were less likely to consider trees to be important in their city compared with people located in naturally forested areas. Overall, our research demonstrates the inherent connections between local environmental factors and perceptions of nature, even in large modern cities. Accounting for these factors can contribute to the growing interest in understanding patterns of urban biodiversity.     

Personal Letters, Oral Testimony and Scottish Migration to New Zealand in the 1950s: The Case of Lorna Carter

By blending emigrant letters and oral testimony and illuminating the benefits and drawbacks associated with each source, as revealed in this case study of a Scottish female migrant, this article contributes to the methodology of the use of personal testimony within migration studies. It shows that though there can be some discrepancies between contemporary documentation and later memory, interviews with migrants are particularly useful when they can flesh out areas of interest not contained in contemporary documents. This article therefore argues for greater integration of oral and written testimony in order to capture fully the rich and nuanced personal experience of migration from the perspective of its participants.     

Desired family size and its determinants among urban Nigerian women: A two-stage analysis

This paper proposes and carries out a two-stage analysis of the determinants of desired family size, using data gathered from a sample of women in the city of Ilorin, Nigeria. The analysis first focuses on differences between women who report numerical family size desires and those who report nonnumerical desires. Findings suggest that there are important differences between these two groups, but there is little variation in the actual number reported by those expressing numerical desires. Implications of these findings for survey design are discussed. In particular, the practice of forcing numerical responses by instructing interviewers to probe when women report nonnumerical desires is questioned.