Factors Limiting Plant Growth on High-Level Blanket Peat III. An Analysis of Growth of Molinia Caerulea (L.) Moench. in the Second Year

Abstract

caerulea and Dactylis glomerata on peat. Two different climatic environments were employed in an attempt to separate the relative effects of mineral nutrition and climate. The Moor House National Nature Reserve (1850 ft, 564 m O.D.) is the main centre of study; growth there, onhigh-level blanket peat, was compared with growth of material from the same stock at sea level on a raised bog type of peat at Deer Dike Moss in north Lancashire. Results, already reported, of the first year's growth of Molinia showed no significant effects of treatment with nitrogen and phosphate, either singly or in combination although there were marked differences of yield between the two places. In Dactylis at Moor House there was a significant increase in dry weight with nitrogen but not with phosphate and there was no interaction in the combined treatment. At Deer Dike Moss there was no growth response to nitrogen but phosphate promoted extra growth and the combined treatment gave a strong positive interaction. The choice of Molinia in this experiment was mainly because of the robust nature of this species in which new growth is more easily distinguished and separated than in many other moorland species. This paper is concerned with the analysis of the continued growth of Molinia only, in the second year. From the general observation it was not considered possible to obtain a satisfactory measure of the growth pattern from seed or from cuttings in the first year after planting on the nearly undisturbed peat at Moor House. Growth from seed in one season is inadequate for measurement, while cuttings may give unreliable results during the first year. It is for these reasons that analysis on the growth of Molinia has been continued into the second season. Dactylis was found less suitable for study in the second year partly by reason of its diffuse growth habit and partly because of wide variability in yield. The climate at Moor House is severe and is generally similar to that found in southern Iceland (Manley 1936). On the other hand at Deer Dike Moss the climate is subject to the relatively mild maritime conditions of Morecambe Bay. From the climatological data available it is clear that the mean annual temperature relationship between Moor House and Deer Dike Moss is similar to that given by Pearsall (1950) between a hypothetical station at 2000 ft (610 m) O.D. in north Britain and Fort William, Inverness-shire at 27 ft (8 m) O.D.