The bringing together of seed sources from different geographic areas in properly designed field experiments (provenance trials) makes possible a range of investigations of the environmental relationships of silver birch. These can encompass molecular studies of, say, cpDNA, allowing inferences of the post-glacial history of the species or estimation of the physiological responses to variable climatic stimuli.
The simplest studies of phenological differences in leaf flushing and senescence have, in the case of silver birch, been the subject of a series of student dissertations. Comparative assessments of leaf size across contrasting British sites are being analysed at present, while a basic study of winter desiccation of shoots induced by shoot embolisms has been published. Recent investigations have attempted to assess the development of stem form among provenances across contrasting experimental sites and this work can be extended now with the collection of clonal ‘plus tree’ material.
An earlier study of pollen dispersal within a polyhouse seed orchard, using the Great Glen population, demonstrated satisfactory levels of cross-pollination of clones. A programme of relatively simple progeny trials for the seed produced by these breeding populations is envisaged to demonstrate their potential superiority to current commercial seedlots and allow them to attain ‘tested’ status. As more information becomes available from trials of this kind and from the provenance experiments, it will be possible to re-define the ‘regional’ breeding population and seed collection zone boundaries, for which there is as yet slight scientific evidence.