No abstract

SUMMARYDetailed mapping and recording have shown that many of the commonest bryophytes in Northumberland are totally absent from a large part of the Lower Tyne Valley. The affected area is centred on the coalfield where scattered colliery towns, burning pit heaps and the huge conurbation of Newcastle upon Tyne lie. Emphasis is laid on sulphur dioxide pollution being responsible. Two anomalous situations where sensitive species are found growing well inside their normal limit were investigated. It appears that shelter has a greatly modifying effect in reducing SO2 (but not smoke) levels and that a high pH influences the degree of ionization and rate of oxidation of SO3 " so as to favour survival. Protonemata appear to be more sensitive than mature gametophytes.Most bryophytes cannot exist when the average winter concentration of SO2 exceeds 50 /(g/ m^ or 0.01 ppm.

SUMMARYAfter comparing sixteen aspects of their biology it is clear that despite wide differences in botanical affinity bryophytes and lichens are outstandingly similar in their response to S02' This suggests that these lower plants can only colonize inhospitable habitats by adaptations which carry with them an inherent susceptibility to air pollution. Extensive laboratory and field work has emphasized the controlling influence of habitat on the survival of species. Among the strongest modifying influences are shelter, the pH and buffer capacity of the substratum and nutrient flushing. There is an apparent connection between survival and age of substratum. Water relations were found to have little effect. The extreme sensitivity of most epiphytes and the problems raised by resistant species are discussed.

No abstract

No abstract