Trace Tracker —— For the Trails at Allegheny Portage Railroad National Historical Site

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ISBN: 9781334306082 出版年：2016 页码：35 Forgotten Books

A rotting stump is home to many small creatures who in turn hasten the process of decay. Decomposers such as earthworms feed on dead organic matter and break down the debris into substances te-usable by new plants. Nature's efficient and economical processes continuously recycle important nutrients and are self-sustaining. On the other hand, man-made Operations (such as this railroad) need continuous maintenance and a steady input of energy.