報告書番号

U01007

タイトル（和文）

樹木模擬群落における降雨時の塩基流亡特性の解明とモデル化

タイトル（英文）

Characteristics and modeling of basic cations dissolution and leaching by precipitation in experimental tree communities

概要 （図表や脚注は「報告書全文」に掲載しております）

樹木群落の塩基流亡特性を明らかにするとともに，既開発の樹木個体の塩基流亡モデルを群落に適用できるように改良するために，ブナの模擬群落を用いて，自然降雨時の塩基（K, Ca, Mg）流亡量と樹冠における雨水の分配との関係を解析した。その結果，樹冠投影面積，葉面積，植被率が大きいほど塩基流亡量が大きくなる傾向が認められた。さらに，個体の樹冠が隣接木と重なっている部分が多くなるに従い，樹冠雨に対して樹幹流による塩基流亡量の割合が大きくなる傾向が認められた。また，個体塩基流亡モデルの樹冠構造を単層から３層に変更し，①樹冠投影面の重なりの面積の増加にともない樹幹流への雨水の分配率が直線的に増加する，②樹冠が重なる部分では隣接木毎の葉面積の割合に比例して雨水が分配される，とする関係を組み込むことで，模擬群落における塩基流亡量の計算値と実測値がよく一致した。

概要 （英文）

In order to clarify dissolution and leaching of basic cations (K, Ca, Mg) from the crown by precipitation (wash-off) in tree community and to apply the basic cations wash-off model for single tree (to estimate the wash-off rate of basic cations) to tree community, the patterns in wash-off of the basic cations were examined by observations at experimental tree communities (Fagus crenata). (1) Characteristics of basic cations washed-off Observation results in the experimental tree communities showed that 1)the amount of basic cations washed-off by throughfall and stemflow increased with increasing of the crown projection area, leaf area and vegetation cover， 2) the amount of stemflow water volume and ratio of basic cations washed-off by stemflow to throughfall increased with increasing overlapped parts of the each tree crown.(2) Estimation of basic cations washed-off by model The crown structure in basic cations wash-off model for tree community is 3-layer to express the overlapped part of the crown. A single tree model was modified to estimate the experimental tree communities in based on the following hypothesis, 1) the distribution ratio of rain water to stemflow increases linearly with increasing of the overlapped part of crown projection area, 2) rain water distributes to each tree crown in proportion to the leaf area in overlapped crown parts. The model estimation of basic cations washed-off showed good coincidence with the observations in the experimental tree communities.

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