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    小兴安岭凉水典型阔叶红松林林冠干扰特征分析

    Characteristics of canopy disturbance for a typical broadleaf-Korean pine mixed forest in Xiaoxing'an Mountains, Liangshui, northeastern China.

    • 摘要: 依托小兴安岭凉水阔叶红松林动态监测样地, 运用样方法和树木年代学方法, 调查了样地中6hm2典型阔叶红松林内扩展林窗(≥50m2)特征, 分析了小兴安岭典型阔叶红松林林冠干扰特征及形成原因。结果表明: 林窗平均密度为7.67个/hm2, 平均产生速率为0.08个/(hm2·a), 干扰频率为0.42%/a, 干扰周转期约240年。林窗形成树种主要是红松(50.22%)、臭冷杉(9.78%)、枫桦(7.78%)以及腐烂程度较严重而无法判别的树种(10.44%), 死亡方式主要为干基折断(54.9%)。林窗由多种死亡方式共同形成, 3种以上形成方式占70.83%。每个林窗形成木平均为9.38 株, 且腐烂等级较高。小径级木是林窗形成的受害者, 而不是贡献者; 针叶树对林窗形成的贡献远大于阔叶树。林窗边缘木平均胸径为46.68cm, 平均树高23.6m, 以红松为主(63.08%)。边缘木中臭冷杉生长最快, 红皮云杉和色木槭生长最慢。不同等级林窗内形成木和边缘木的种类和组成相似, 林窗形成木界定标准对判定林窗形成方式影响很大。综合多种方法调查大、中型林窗及大径级形成木, 可提高林窗干扰历史重建及成因判定的准确性。此外, 利用分层解析法可将发生过2次或多次干扰的大、中型林窗形成与发展过程动态解析, 这对理解林窗干扰动态及森林群落演替至关重要。

       

      Abstract: To analyze the characteristics and formation causes of expanded gaps due to canopy disturbance in a broadleaf-Korean pine (Pinus koraiensis) mixed forest in Xiaoxing'an Mountains, Liangshui, northeastern China, we investigated all expanded gaps (≥50m2) in a 6ha permanent plot by using the quadrat survey and dendrochronology methods. Results showed that the expanded gaps, with a speed of 0.08ha per year, occurred by an average density of 7.67 gaps per hectare. The frequency and return period of canopy disturbance was 0.42% per year and 240 years, respectively. The main formative tree species of forest gaps were P. koraiensis (50.2%), A. nephrolepis (9.78%), Betula costata (7.78%) and other trees (10.44%) which cannot be identified to species level due to serious decay. Death modes of trees for a gap were mainly breakage at trunk base (BB, 54.89%). Forest gaps were formed mainly by more than three ways of tree death, which accounted for 70.83% of all gaps. The average number of gap makers in a gap was 9.38 individuals, and most of them were in a higher decay level. Small-diameter fallen trees were often the victims rather than makers of gap formation, and the contribution of conifers to a gap formation was much greater than broadleaf trees. The average diameter at breast height in a gap border was 46.68cm (range 11.4-126.5cm) and height of trees 23.6m (range 5.6-42.9m), and the major tree species was Pinus koraiensis (63.08%). Abies nephrolepis grew fastest among all tree species in gap borders, while Picea koraiensis and Acer mono grew slowest. The species and compositions of gap makers and border trees were similar in gaps of different sizes, but the definition standard of gap makers has significant influences on the causes of gap formation. The accuracy of reconstruction of disturbance history and determination of formation causes can be greatly improved by surveying large and medium-sized gaps as well as large diameter makers using several comprehensive methods. In addition, the development and formation process of large and medium-sized gaps in which two or more disturbances occurred can be clarified, which is crucial for understanding the dynamics of canopy disturbance and succession of forest communities.

       

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