Meteorological Conditions of Mangosteen Orchard in West Java, Indonesia and Seasonal Changes in C-N Ratio of Their Leaves as Affected by Sector (Position in Canopy) and Tree Age

Productivity and quality of mangosteen fruit is markedly affected by tree age and sector (position in canopy). The objective of this study was to make clear seasonal changes in meteorological conditions of mangosteen orchard, and C-N ratio of leaves in relation to tree age and sector. The experiment was conducted using mangosteen trees grown in commercial orchard in Bogor, Indonesia during May to October 2010. Mangosteen trees of 3 different ages, young (20-year-old), middle (35-year-old), and old (50-year-old), each of five trees, were selected for study, and the canopy of each tree was divided into 9 sectors based on height (bottom, middle, top) and width (inner, center, outer). The light intensity on sunny days was higher in Sector 9, it was 8.1, 7.5, and 7.7 μmol・M(−2)・s(−1) in young, middle-aged and old trees, respectively, whereas in Sector 1 it was low, resulting 0.5, 0.4, and 0.5 μmol・M(−2)・s(−1) in young, middle-aged and old trees, respectively. Regardless of tree age, light intensity in outer position in canopy was higher than in the inner, and also it was higher in taller than in lower positions in canopy. In 2010, the phenological aspects of mangosteen orchard markedly changed because of irregular rainfall. In spite of tree age, SPAD value of leaves in upper parts such as Sectors 5-9 was high comparing with lower ones such as Sectors 1-4. In young trees, carbohydrate content of leaves was higher in top positions such as Sectors 7-9 than in bottom ones such as Sectors 1-3, whereas in middle-aged and old trees, no significant difference of carbohydrate content was observed among sectors. Regardless of month and tree age measured, nitrogen content of leaves was higher in lower positions in canopy such as Sectors 1-4 than in upper ones such as Sectors 5-9. Consequently, the C-N ratio of leaves was higher in the upper part of canopy compared to the lower. Based on the results, the relationships between meteorological status and C-N ratio of leaves and fruit productivity and quality of mangosteen are discussed in relation to position in canopy and tree age.

マンゴスチンの果実生産性や果実品質が樹冠部位や樹齢によって異なる点について，インドネシア西ジャワの商業的マンゴスチン園で照度と降雨量を調査するとともに，20，35および50年生樹を５個体ずつ選び，各個体樹冠の高さと幅から9つのセクター（樹冠部位）に分け，葉の葉色値（SPAD値），クロロフィル含量，炭水化物含量，窒素含量およびC-N率を比較した．晴天日の照度は，樹齢による差は小さくセクター9（各樹齢7.5～8.1μmol・M(-2)・S(-1)）が最も高く，一方セクター1（各樹齢0.4～0.5μmol・M(-2)・S(-1)）で最も低かった．樹冠外部の照度はいずれの樹齢も樹冠内部よりも高く，またセクター1，2，3のような下部よりも7，8，9のような上部で高かった．調査を行った2010年は雨季の開始が例年よりも2～3か月早く，このため樹体の生育相が例年とは大きく異なった．葉色値は樹齢に関係なくセクター1～4のような下部の葉よりもセクター5～9のような上部の葉で高かった．葉の炭水化物含量は，20年生樹ではセクター1～3の下部よりも7～9の上部で高かったが，35年生と50年生樹ではそれぞれ50.7～53.0%と51.3～52.6%で大差なかった．一方，葉の窒素含量は樹齢や測定時期に関係なくセクター5～9の上部よりもセクター1～4の下部で高かった．このため，葉のC-N率は樹冠の下部よりも上部で高かった．この結果をもとにマンゴスチンの果実生産性と品質および樹冠部位と樹齢との関係を考察した．

原著論文 (Original paper)