Fire, fragmentation, and windstorms: A recipe for tropical forest degradation

Widespread degradation of tropical forests is caused by a variety of disturbances that interact in ways that are not well understood. To explore potential synergies between edge effects, fire and windstorm damage as causes of Amazonian forest degradation, we quantified vegetation responses to a 30-min, high-intensity windstorm that in 2012, swept through a large-scale fire experiment that borders an agricultural field. Our pre- and postwindstorm measurements include tree mortality rates and modes of death, above-ground biomass, and airborne LiDAR-based estimates of tree heights and canopy disturbance (i.e., number and size of gaps). The experimental area in the southeastern Amazonia includes three 50-ha plots established in 2004 that were unburned (Control), burned annually (B1yr), or burned at 3-year intervals (B3yr). The windstorm caused greater damage to trees (>10 cm DBH) in the burned plots (B1yr: 13 ± 9% of 785 trees; B3yr: 17 ± 13% of 433) than in the Control plot (8 ± 4% of 2,300; ± CI). It substantially reduced vegetation height by 14% in B1yr, 20% in B3yr and 12% in the Control plots, while it reduced above-ground biomass by 18% of 77.7 Mg/ha (B1yr), 31% of 56.6 (B3yr), and 15% of 120 (Control). Tree damage was greatest near the agricultural field edge in all three plots, especially among large trees and in B3yr. Trunk snapping (70%) and uprooting (20%) were the most common modes of tree damage and mortality, with the height of trunk failure on the burned plots often corresponding with the height of historical fire scars. Of the windstorm-damaged trees, 80% (B1yr), 90% (B3yr), and 57% (Control) were dead 4 years later. Trees that had crown damage experienced the least mortality (22%–60%), followed by those that were snapped (55%–94%) and uprooted (88%–94%). Synthesis. We demonstrate the synergistic effects of three kinds of disturbances on a tropical forest. Our results show that the effects of windstorms are exacerbated by prior degradation by fire and fragmentation. We highlight that understorey fires can produce long-lasting effects on tropical forests not only by directly killing trees but also by increasing tree vulnerability to wind damage due to fire scars and a more open canopy. © 2018 The Authors. Journal of Ecology © 2018 British Ecological Societ

A Cable Laid Is a Cable Played : On the Hibernation Logic behind Urban Infrastructure Mines

Our societies are reliant on metals to such an extent that the total amounts of some of them in the built environment are comparable in size to the remaining amounts in known mountain ores. Because of concerns about mineral scarcity, the United Nations has assessed alternative sources for metal extraction and targeted urban areas in general and infrastructure systems in particular, since these are large, spatially concentrated and rich in metals. Referring to the possibility of recovering these metal stocks, infrastructure systems constitute what material flow researchers has conceptually termed “urban mines.” While most urban infrastructure is in use, significant amounts of cables and pipes have been disconnected and remain in their subsurface locations; they are “hibernating.” In this article, we analyze the occurrence of such hibernation in the Swedish city of Norrköping's urban infrastructure mine where, we know from a previous study, that every fourth kilo of infrastructure is discarded. Our applied perspective is different from the logic of system expansion as a way to meet increased demand often found in the field of infrastructure studies since we are interested in how systems are disconnected and left behind. This enables us to offer a refined understanding of the concepts of infrastructure “decline” and infrastructure “cold spots.” We argue that to prevent the increase of dormant infrastructures and to engage in the urban mining of already dormant infrastructures, we must develop a sensibility to the materiality of derelict infrastructure components and the underlying causes for why they form different kinds of spatial patterns