MORPHOLOGICAL DYNAMICS AND SEEDLING RECRUITMENT IN YOUNG SWARDS OF 3 CONTRASTING CULTIVARS OF WHITE CLOVER (TRIFOLIUM-REPENS) UNDER CONTINUOUS STOCKING WITH SHEEP

Although there has been some recent interest in the morphology of indi vidual white clover plants within established mixed swards under sheep grazing, there is little information available on the morphological c hanges taking place during the critical first 3 years of sward develop ment. Undamaged white clover plants were sampled from an experiment at Plas Gogerddan, Ceredigion, comparing three contrasting white clover cultivars, sown with a common companion ryegrass cultivar, under conti nuous stocking with sheep. Turves (250 x 250 mm), from which individua l plants were carefully extracted, were taken every month during 1990- 91 (year 2 and 3 after sowing). Each plant was described in detail by assessing a range of morphological characters. Information was also ga thered from each quadrat on the degree of flowering and seedling recru itment. There were clear seasonal variations in plant size and complex ity with an increase in the number of simple, unbranched plants over t he winter/spring period, which became the dominant plant type by June. During the later part of each year, the reverse was true. Characters associated with plant size also decreased over the winter period, foll owed by recovery during the ensuing summer. However the recovery was n ot complete and there was a strong general trend towards an increased proportion of less complex plants of reduced size over the 2 years. As plant size fell, plant number increased and morphological differences between cultivars diminished. By autumn of the second year (third yea r after sowing) the mean plant size reached a critical level with furt her stolen loss resulting in large scale plant death. Over the 2-month period August-October 1991, plant number fell by 60% and resulted in a reduction in stolen abundance of 76%; a true clover crash. The seedl ing data also suggest that under these conditions seedling recruitment can be up to one twentieth of that expected from a conventional sowin g and can play a substantial role in the regeneration of the sward.