. Elemente der Ökologie. Ökologie. Sekundäre Folge 437 komplett aus dem Boden zurückgewonnen und die geräumten Gebiete waren an Kulturen bepflanzt oder als Weiden genutzt. Anfang kurz nach 1830 die Open- reiche Ländereien im Westen, den Bau von Eisenbahnen und das Wachstum der industriellen Zentren, brachte den Exodus der Betriebsinhaber von den felsigen Hängen von New England, die so schwer zu arbeiten. Die verlassenen Felder wurden von einer dicken sod von Gras bedeckt. In diesem Rasen die Samen von white pine Bäume aus dem benachbarten Waldgebiete geblasen, ein günstiges Umfeld für die Keimung gefunden, aber o

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. Elements of ecology. Ecology. Secondary Succession 437 completely recovered from the soil, and the cleared areas were planted to crops or used as pastures. Beginning shortly after 1830 the open- ing of rich farmlands in the west, the building of railroads, and the growth of industrial centers, brought about the exodus of the farmer from the rocky hillsides of New England that were so difficult to work. The abandoned fields were covered by a thick sod of grass. In this turf the seeds of white pine trees blown from neighboring forested areas found a favorable environment for germination, but other forest trees were not able to establish themselves effectively in the aban- doned fields. The result was that the white pines grew into a dense, uniform stand, and eventually produced a forest in which all the dominant trees were of this species. A few hardwood saplings later became established as an understory throughout the pine forest, but their further growth was suppressed by the pines. In the course of fifty years or so, the pines had grown to a size that made a valuable timber harvest possible. Great areas were lumbered off; in regions where lumbering was not carried out the even-aged trees grew old and finally fell. In both situations the trees which then grew into dominant position were not white pines but were hardwood trees that had existed in subordinate position almost un- noticed in the pine forest. Pines will not sprout from stumps, and, being an intolerant species, the pine seedlings are unable to develop in the shade of the mature trees (Fig. 12.5). The root sprouts and. Fig. 12.5. View of the forest floor in a stand of mature white pines in southern New Hampshire, showing the aljsence of pine seedlings but the presence of beech and maple saphngs.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the origin

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• bookcentury1900
• bookpublishernewyorkwiley
• booksubjectecology