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The NeighborWoods Coordinator then visits the project site by bicycle to spot - <br /> check for accuracy, and to examine the project area's soils before species <br /> recommendations can be made. <br /> SOIL TYPES <br /> Species recommendations are based not only on the amount of space available <br /> above - ground, but also on the kind of soil found on a particular site. It is <br /> therefore important that a someone who is familiar with the limitations of <br /> different soil types examine the project area before any recommendations are <br /> made. <br /> It is useless to attempt to grow a tree native to well- drained, upland areas <br /> in the poorly- drained lowland soils of some neighborhoods. Such trees may <br /> survive for a few years, but they will almost certainly fail to thrive. When <br /> we fail to match the tree species with the type of soil it will grow in, our <br /> community eventually loses not only the tree, but also the time it took for <br /> the tree to die and to be removed, when a better - suited tree could have by <br /> that time been growing vigorously and already providing the many benefits <br /> healthy trees provide for us. <br /> Eugene's many different soil types fall into three major classes: <br /> Class I: Deep, well- drained, fertile soils in the vicinity of the <br /> Willamette River <br /> Class II: Shallow soils with fair drainage on hillsides <br /> Class III: Heavy, very poorly drained clay soils in the vicinity of <br /> Amazon Creek and on the toe - slopes of hills. <br /> Virtually any tree that is hardy in the southern Willamette Valley (several <br /> hundred different species) can be grown on Class I soils. Fewer than half <br /> that many tree species grow well on Class II soils because of the relatively <br /> shallow soils which dry out in summer (unless irrigated). And on Class III <br /> soils, only a couple dozen species grow well due to the poor aeration of these <br /> heavy soils, the high winter water table, and the rock -hard nature of the soil <br /> during the summer drought. <br /> SPECIES SELECTION <br /> Like any forest, the health of our urban forest depends on the presence of a <br /> variety of tree species and tree ages. The greater the variety, the more <br /> resiliency that forest will have in the event of any environmental change <br /> (e.g., drought, insects, construction activity). <br /> Certain tree species (such as red maple, sweetgum, and northern red oak) have <br /> been greatly overplanted in our area in the last fifteen years. The principal <br /> reasons for overplanting these species are their ready availability in <br /> nurseries, their ability to grow almost anywhere, and their showy fall <br /> foliage. And because they have been overplanted, they are consequently well - <br /> known to most people, so the cycle continues because most people naturally <br /> 5 <br />