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在美国南方松林的经营管理中,高产的种子园是营林部门极其重要的组成部分,因此,森林经营者最为关心的是影响种子园母树生长的因子。 1981年以来,佛罗里达州北部几个种子园中,出现了不明原因的松树枯死现象:外观正常,树势壮旺,生长快,显得健康的母树很快就枯死。这些树都是美国的乡土树种[沙松(Pinus clausa)和湿地松(P.elliottii)]。它们生长在自然分布区内的适生林地,没有其它疫病和营林方面的问题(如根病、树干溃疡、树瘿、肥害等),这些母树根系很发达,也没有嫁接不适等迹象。
In the management of pine forests in the southern United States, high-yielding seed orchards are an extremely important part of the forest management sector. Therefore, the most concern for forest managers is the factors that affect the growth of the seed trees in the seed orchard. Since 1981, several seed orchards in the northern part of Florida have witnessed an unidentified death of pine trees: normal appearance, vigorous growth, rapid growth and healthy maternal trees soon die. The trees are native to the United States (Pinus clausa and P.elliottii). They grow in well-established areas in natural habitats and are free of other epidemics and silviculture problems (eg, root disease, tree ulcer, tree stumps, fertilizer damage, etc.), which are well-developed and have no signs of grafting discomfort.