VARIATION IN DEMOGRAPHY OF JUVENILE TSUGA-HETEROPHYLLA ACROSS THE SUBSTRATUM MOSAIC
VARIATION IN DEMOGRAPHY OF JUVENILE TSUGA-HETEROPHYLLA ACROSS THE SUBSTRATUM MOSAIC
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DOI：
10.2307/2260007
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发表时间：
1984-01-01
影响因子：
5.5
通讯作者：
MACK, RN
中科院分区：
文献类型：
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作者：
CHRISTY, EJ;MACK, RN
在美国俄勒冈州中部喀斯喀特山脉西坡不同基质上对异叶瓢虫幼虫的招募和存活进行了研究。虽然种子主要在10月至3月期间下降，但在连续32个月中，除了6个月外，其他所有月份都有种子。几乎所有的幼体都生长在腐烂的原木上，即使倒下的木材可能只覆盖森林地面的10-30%。所有基质上的吸收情况每年都有很大的变化，正如在种子产量最多的针叶树中所预期的那样。即使在同一根基质上，1日历年中不同月份出苗的群体存活率曲线也有很大差异。幼鱼在出现后的头两年死亡率比随后几年高得多。微型啮齿动物可能是造成种子和幼苗死亡的主要原因。木本生根基质的腐烂程度对羽化率没有影响，但在心材腐烂的木本上，羽化幼体的存活时间最长。幼树种群的年龄级结构是每个衰变级中被砍伐木材覆盖的森林地面比例的函数。
Recruitment and survival of juvenile T. heterophylla were followed on different substrata on the west slope of the Cascade Range, central Oregon, USA. While seeds fell mainly from Oct.-March, some were shed in all but 6 of 32 consecutive months. Almost all juveniles occurred on decaying logs even though fallen timber may cover only 10-30% of the forest floor. Recruitment on all substrata varied widely from year to year, as expected in a conifer with mast years of seed production. Cohorts emergent in different months during 1 calendar year often showed greatly different survivorship curves even on the same rooting substratum. Mortality was much higher for juveniles during the first 2 yr after emergence than in subsequent years. Microtine rodents probably account for most seed and seedling deaths. The extent of decay of woody rooting-substrata does not influence percentage emergence, although survival of juveniles was most prolonged on Pseudotsuga menziesii logs with rotten heartwood. The age-class structures of juvenile populations were functions of the fraction of the forest floor covered by fallen wood in each decay class.