摘要:密叶红豆杉（Taxus fuana）为我国I级保护野生植物，由于其对生长环境要求严苛，在全球范围内少有分布。依据对西藏自治区日喀则市吉隆县区域密叶红豆杉自然分布的调查，对其群落组成、结构特征和种群竞争等进行了研究。通过计算各植物的重要值（P_i），并根据重要值进行了聚类分析，将研究地区划分为铁杉（Tsuga chinensis）+密叶红豆杉群落（C1）、高山栎（Quercus semicarpifolia）+密叶红豆杉+朴树（Celtis sinensis）+华榛（Corylus chinensis）群落（C2）、密叶红豆杉+刺叶高山栎（Quercus spinosa ）群落（C3）、铁杉+密叶红豆杉+华榛群落（C4），群落中密叶红豆杉多为散生，4种群落分布于吉隆县的热玛村、郎久村和吉普村。通过对各个群落中所有树种树高（H，Hight）胸径（DBH，Diameter at Breast Height）的整理，得出：四种群落的垂直结构明显，铁杉最高，平均树高可达25 m，密叶红豆杉与其他乔木较矮，处于亚优层，平均树高约为7 m；除C3群落乔木层比例为17.8%外，其他群落乔木层比例皆大于50%；四种群落中密叶红豆杉更新层比例均为0，缺乏小径级个体；密叶红豆杉的立木结构在不同群落中表现不同，C1、C2群落径级分布较好，C3群落多为中小径级，而C4群落则出现了严重的断代问题。垂直结构和立木结构都说明密叶红豆杉存在严重的更新不足问题。通过对所有物种丰富度指数、多样性指数、均匀度指数的计算，得出群落间物种多样性和丰富度较好，但均匀性较差。研究地区的密叶红豆杉分布稀疏，平均每100 m²密叶红豆杉仅有1.34株，由于分布稀疏，密叶红豆杉的种间竞争大于种内竞争，其主要竞争压力来自于铁杉和高山栎。这一系列问题必将导致密叶红豆杉的种群衰退，因此，其更新和保护问题，应该受到密切的关注。



Abstract:Taxus fuana is a national Category Ⅰ protective species in China, which is seldom distributed in other regions of the world due to its strict requirements for the growing environment. In this research, the natural distribution, the community composition, structural characteristics, and species competition of T. fuana in Jilong were investigated. The cluster analysis results according to the important value (P_i), showed that T. fuana mainly formed four community types, including the community of Tsuga chinensis + T. fuana (C1), Quercus semicarpifolia + T. fuana + Celtis sinensis + Corylus chinensis (C2), T. fuana + Quercus spinosa (C3), and Tsuga chinensis + T. fuana + Corylus chinensis (C4), which were mostly scattered in Rema village, Langjiu village, and Jipu village of Jilong town. By sorting out the data of all kinds of trees' height (H) and diameter at breast height (DBH), the vertical structure of the four communities was obvious. Tsuga chinensis was the highest with the average height of 25 meters, while T. fuana and other trees were lower with the average height of 7 meters. The arborous layerproportion of all communities were greater than 50% except that the proportion of C3 community was 17.8%. The proportion of regeneration layer of T. fuana in the four communities was zero, so there were serious regeneration problems. The tree structures of T. fuana were different in different communities. The diameter-level distribution of C1 and C2 communities were relatively good, C3 communities were mostly middle or small grade, while C4 communities had serious dating problems. The vertical structure and tree structure indicated that T. fuana had serious insufficient regeneration problem. The index showed that the species diversity and richness were better, but the evenness was worse. T. fauna in the study area was sparsely distributed, with only 1.34 plant per 100 m² on average. Because of the sparse distribution, the inter-species competition of T. fuana was greater than the intra-species competition, and the main competitive pressure was from Tsuga chinensis and Quercus semicarpifolia. A series of problems of T. fuana might result in the declination of this species, therefore, the regeneration and competition of T. fuana must be concerned.





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