The results of five provenance trials of silver birch ( Betula pendula Roth.) in Scotland are described. These comprise: (1) two trials laid out in the 1970s and 1980s comparing improved Finnish stock with unimproved Scottish material, and (2) three recently established provenance trails of Scottish seed sources for which 1–2 year results are available. Use of planting stock of Scandinavian origin is not advisable in Scotland, or probably elsewhere in the UK, as it has poor survival and grows slowly (i.e. volume growth at years 16–22 is only 7–26 per cent of the Scottish controls). It is particularly prone to climatic damage due to late spring frosts. Recently established trials of seed sources from Scotland and Northern England showed significant variation among Scottish populations in growth and dates of flushing and senescence. Variation in 1-year height growth between the fastest and slowest growing provenances was about 30 per cent. Some geographic patterns of variation in early height growth and flushing were apparent among different seed sources at year 1, but equally there was considerable variation among sources which could not be simply attributed to location. A preliminary study of isozyme variation suggests that: populations are unlikely to have passed through severe population bottlenecks; that there is no consistent evidence for inbreeding within the populations; extensive gene exchange occurs between populations by pollen and/or seed flow; and there is no evidence for more than one postglacial origin for the nine populations tested. There is a need for more information on provenance performance among indigenous populations of birch in order to give useful guidance to nurseries, foresters and policy makers.
描述了在苏格兰进行的五个
银桦(Betula pendula Roth.)源试验的结果。这些试验包括: (1) 在1970年代和1980年代进行的两项试验,比较了改良芬兰种源和未改良的苏格兰材料,(2) 最近建立的三个苏格兰种子源的试验,提供了1至2年的结果。 不建议在苏格兰使用斯堪的纳维亚起源的种植材料,或者在英国的其他地方,因为其存活率较低且生长缓慢(即在第16至22年间的体积生长仅为苏格兰对照组的7-26%)。它特别容易受到由于晚春霜冻造成的气候损害。最近建立的来自苏格兰和英北的种子源试验显示,苏格兰种群在生长、萌发和衰退日期上存在显著差异。最快和最慢生长的种源在1年时的高度生长差异约为30%。在第1年,不同种子源在早期高度生长和萌发方面表现出一些地理模式的差异,但同样也存在可观的变化,这无法简单归因于位置。对同工酶变异的初步研究表明:种群不太可能经历严重的人口瓶颈;种群内没有一致的近交证据;通过花粉和/或种子流动,种群间发生广泛的
基因交流;对于测试的九个种群,没有证据表明存在多个冰后起源。需要获得更多关于本地桦树种群的来源表现的信息,以便为苗圃、林业人员和政策制定者提供有用的指导。