What is local? An introduction to genetics and plant selection in the urban context

Journal Article

Justification

The urban landscape comprises myriad isolated green spaces inhabited by an assortment of vegetation types. To many city dwellers, these green spaces interrupt the monotony of concrete and steel and foster deep social attachment between city dwellers and nature. To a conservationist, these vegetation islands provide unique opportunities to restore ecological function to degraded areas by revegetating them with native plants. However, the restoration ecologist faces many challenges unique to the urban landscape. A significant investment in site preparation may be needed to offset the impacts of abiotic factors including compacted soil, drought, and air pollution. Seedlings that survive to maturity are not guaranteed immunity from these abiotic stresses, as is evident in the tree dieback and declines that plague many city landscapes. Abiotic factors are rarely the sole causal agent of urban tree declines since the presence of a multitude of other factors, such as insects and disease, are associated with symptoms of this decline. For example, drought in combination with insect defoliation predisposed black oak (Quercus velutina ) to decline, while defoliation and several pathogens were causal agents in the decline of English oak (Quercus robur ). The impacts of biotic factors on plant health may be heightened or lessened in urban areas depending on the ecology of he insect or disease. In these examples, black oaks in urban areas were more susceptible to damage from gall wasps than trees surrounded by contiguous forest. In contrast, the pathogens inciting decline in Quercus robur are less problematic in urban settings where soil disturbance prevent Armillaria fungus from spreading great distances.