Studies in the Autecology of Juncus Squarrosus L

Abstract

Studies in the autecology of Juncus squarrosus L. have been made over a three-year period, mainly in the area of high-level moorland at the head of Teesdale in the north Pennines. The morphology and anatomy of the plant are described, and an account is given of the form of the communities. Annual increments in rhizome growth of 0.5 to 2.0 cm. were recorded. About 20 sites were examined phytosociologically, Five noda were distinguished, namely the peaty gley, the podsol, the species-poor gley, the species-rich gley and the flushed-peat noda. The reproductive capacity was measured at 12 of these sites. IV here Juncus is dominant up to 8,000 seeds can be produced per square metre. Production is lower on well-drained soils, the number of florets per inflorescence being less, and when a smaller proportion of florets ripen to form capsules. In average years 50% of the florets ripen at heights up to 1800 ft. (550 m.). Larvae of the moth Goleophora alticolella eat the seeds at the lower levels, and changes in its population size have been followed. Seed viability is usually high, but experiments showed that germination requires light at the normal field temperatures. Seedling establishment was found to be uncommon, though large numbers of dormant viable seeds are present in the soil. Various observations are described which provide information on the ecology of Juncus squarrosus. Sheep grazing is held responsible for its present widespread occurrence, and a slow spread will continue in certain of the better grasslands if the grazing pressure is maintained. But this cannot be considered a serious threat to the value of the uplands as the plant has some nutritional value, and most stands contain a considerable proportion of grass. Callunetum, the climax vegetation, is of less value agronomically in the area studied.