環境情報としての樹木年輪の定量解析(II)

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丸谷らは，樹木の偏心生長をベクトルを用いた指標で表現し，その時系例パターンを分析することを提案した．本論では，この方法によって急傾斜他のヒノキと緩傾斜地のモミの生長パターンを分析し，環境条件との関係を考察した．指標は，毎年の4方向生長量a，b，c，dを断面高1．3mと0．3mとで計測し，式（1）生長量w，（2）偏心量l，（3）偏心方向d（4）歪率pdによって計算した．その結果，急傾斜他のヒノキについて，次のことが明らかになった．偏心量と歪率とは，匍行斜面上のヒノキではほぼ一定であるが，洗滌斜面上のヒノキでは15年前に急激に増加している．これは，崖錐堆積物の移動に起因するものと推定された．また，偏心方向は，41～48年の周期性が高い．緩傾斜地のモミについて，次のことが明らかになった．生長量と偏心量とは，40年前から健全木では増加しているのに対し，被圧木では減少している．また，偏心方向は，被圧木では，10～15年間隔で変化している．Marutani et al. proposed a method of analysis for time series patterns by representing the eccentric growth with vector. In this paper, relations between patterns and environment of trees are considered. Figure 1 shows the measurement of vector a, b, c, d of annual rings. All mesurements were made at 0.3 m and 1.3 m height of trees. And we calcurated indicators w (width), l (length), d (direction), pd (percentage of distortion) with vector as follows. w=1/4･(|a|+|b|+|c|+|d|) (1) l=|sl=la+b+c+dl (2) d=sinθ=(|b|-|d|)/1 (3) pd={4･|a+b+c+d|}/{|a|+|b|+|c|+|d|} (4) (W=Σw, L=Σ1, Pd=Σpd) The results for Hinoki trees are shown in Figure 4. Indicator W and L of No. 4 on convex slope increase gradually, and indicator d shows high auto-correlation in cycle of 41～48 years. Indicator W of No. 2 on concave slope increases gradually, and indicator L and Pd begin to increasing since 15 years ago. The results for Momi trees are shown in Figure 5. Indicator W of No. 1 increases for early 20 years. Indicator W of No. 3 begins to increasing gradually since 20 years ago, and indicator d shows the alternation at interval of 10～15 years. The stem transformation is caused by the light environment and the physiographical environment. Relations between these environments and indicators is shown in Table 2. The above results may be explained as followes. In steep slope No. 4 tree is directry fixed on the base rock because of poor soil on convex slope. But No. 2 tree is not fixed because of wealthy talus on concave slope, and stem has inclined caused by talus slip 15 years ago. In loose slope, No. 1 tree has been a stable and equilibristic growth. But No.3 tree has been suppressing by upper crowns, changing the eccentric direction every 10～15 years.
九州大学の論文

環境情報としての樹木年輪の定量解析(II)

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