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New Zealand Plants and their Story

Evolution of Meadows

Evolution of Meadows.

A very common feature of many parts of New Zealand, especially in the mountainous regions, is a broad, shingly river-bed, bounded on either side by high terraces, or sometimes filling up a narrow valley. The water of these rivers is not usually confined to one channel, but meanders in several narrow streams over the wide stony bed, which in consequence is in places quite dry, and ready for plant-colonists. These are not slow to avail themselves of the chance to "take up land," and engage the wind or the birds to convey them to their new holdings, while some even travel by water.

Amongst the earliest settlers are the willow-herbs (Epilobium), thanks to their light seeds furnished each with a tuft of hairs. Various species of Raoulia come in a similar manner, and large, round, mosslike cushions or patches of silver and green result (Raoulia australis, R. tenuicaulis, R. Haastii). Lichens cover the stones with curious markings, and mosses spring up between them. As these earlier plants decay, humus is added to the silty, sandy soil, and various drought-resisting shrubs (Discaria toumatou, Cassinia fulvida, species of Carmichaelia) put in an appearance, together with grass-tussocks. Such shrubs may remain quite isolated, and the tussock become dominant, in which case the shelter will favour the settlement of many small herbaceous plants, including grasses, and a meadow will result. Or, on the other hand, some condition may favour arborescent growth — a natural shrubbery of veronicas, coprosmas, and other shrubs with wiry branches may appear, to be replaced finally by a beech forest. Meadows formed in this manner may be seen in process of evolution in many places, and it was in this way that the great river-made plains, equally with the "fans" of débris at the outlet of creeks, have been colonised by their plant inhabitants. When the forest on a hillside has been burnt, if there are frequent winds, trees cannot be reinstated, and meadow will result. Such fires have been frequent even in the pre-European days. Grasses, especially drought-resisting species, will have a much better chance of growth than trees after a fire, and a meadow will in an astonishingly short time replace the forest. This replacement is page 87quite assured, when in the case of an upland, beech, forest (Nothofagus cliffortioides) the dry leafy floor has been burnt to the soil beneath and, the tree-seeds destroyed, Bearing these facts in mind, and recognising the rain-forest climate of New Zealand, mentioned in Chapter III, it is not impossible that much of the Dominion now treeless, such as Central Otago, was long ago occupied by more or less extensive forests.*

* This remark has no bearing on the question of very ancient totara forests, whose presence is suggested, as Mr. R. Speight has shown, by the abundance of totara logs in Central Otago and certain river-valleys of the Canterbury mountain-region.