Suchergebnisse

Abstract
Buffel grass (Cenchrus ciliaris) is a perennial tussock grass native to parts of Africa and southern Asia but is now distributed throughout much of mainland Australia. Corresponding with its presence in Australia has been an alteration of fire regimes and soil nutrients, and a reduction in floral diversity. We investigated whether buffel grass supported a less diverse community of thrips (order Thysanoptera) compared to the native grasses Cymbopogon ambiguus and Themeda triandra growing in Alice Springs, central Australia. The survey data showed that abundance was highest on buffel grass; however, the thrips community was almost entirely dominated by one species. The thrips communities on the native grasses were similar and markedly more diverse than that on buffel grass, both in terms of species richness and functional feeding groups. Flower feeders constituted the greatest proportion of thrips on all three grasses, but the native grasses also supported leaf feeders and predators. The results indicate that thrips are sensitive to vegetation change, and we suggest that active removal of buffel grass and replacement with local native grasses would help reverse the loss of biodiversity and normal ecological function in urban areas like Alice Springs. We also suggest that the order Thysanoptera is under-utilised in biodiversity research.

Low-income families often live in low-upward-mobility neighborhoods. We study why by using a randomized trial with housing voucher recipients that provided information, financial support, and customized search assistance to move to high-opportunity neighborhoods. The treatment increased the fraction moving to high-upward-mobility areas from 15 to 53 percent. A second trial reveals this treatment effect is driven primarily by customized search assistance. Qualitative interviews show that the intervention relaxed bandwidth constraints and addressed family-specific needs. Our findings imply many low-income families do not have strong preferences to stay in low-opportunity areas and that barriers in housing search significantly increase residential segregation by income. (JEL D83, G51, R21, R23, R31, R38)