報告書番号

U97069

タイトル（和文）

降雨による樹冠からの塩基流亡のモデル化－苗木個体レベルにおける塩基流亡モデルの構築と変動要因の解明－

タイトル（英文）

MODELING OF BASIC CATIONS DISSOLUTION AND LEACHING FROM TREE CROWN BY PRECIPITATION -MODELING AND VARIABLE FACTOR CLARIFICATION OF BASIC CATIONS DISSOLUTION AND LEACHING IN SINGLE TREE SEEDLING-

概要 （図表や脚注は「報告書全文」に掲載しております）

降雨による樹冠からの塩基流亡をモデル化するために，ポット栽培した苗木（ブナ，ウラジロモミ，シラカンバ，スギ）を対象にして人工雨を暴露し，モデルの検証と塩基流亡の変動要因について検討した。その結果，モデルに降雨■断の概念を組み込むことにより，モデルと人工雨による塩基流亡速度の間に良い一致が認められた。また，本モデルでは，塩基流亡の個体間差や樹種間差を，葉面積，葉内元素含有量，降雨■断量の差異で表現することができた。さらに，人工雨のＨ＋濃度の上昇や大気中ＳＯ２濃度の上昇にともない塩基流亡量が増加することが明らかになった。以上の結果から，個体レベルにおいて，樹冠は，（１）塩基収支の媒体である雨水の挙動，（２）塩基供給，（３）酸性雨やＳＯ２等の酸性沈着物の中和を律速する場として，森林の塩基収支に影響をおよぼすことが明らかになった。

概要 （英文）

IT IS NECESSARY TO CLARIFY THE ROLE OF THE FOREST CANOPY IN CATCHING VARIOUS ELEMENTS IN THE ATMOSPHERE AND INPUT TO THE FOREST FLOOR BY PRECIPITATION TO ESTIMATE ELEMENT CYCLING IN A FOREST. IN THE CASE OF BASIC CATIONS (BC),SOMETIMES,THE BC AMOUNTS SUPPLIED TO THE SOIL FROM THE CANOPY BY RAIN ARE FOUR TIMES THE AMOUNTS SUPPLIED FROM LITTER,SO THE ROLE OF THE CANOPY IN BC FLUX MUST BE SOLVED TO EVALUATE BC CYCLING. A BASIC MODEL TO EXTIMATE THE DISSOLUTION ND LEACHING (WASH-OFF) OF BC FROM THE CROWN OF ONE TREE WAS CONSTRUCTED AND VERIFIED USING EXPOSURE EXPERIMENTS WITH SIMULATED RAIN. WE INVESTIGATED THE BC WASH-OFF RATE FROM THE CROWN OF AN INDIVIDUAL POTTED TREE TO VERIFY THE MODEL AND CLARIFY THE VARIABLES IN CROWN BC FLUX. THE MAIN RESULTS ARE SUMMARIZED BELOW. (1) BASIC MODEL THE BASIC MODEL WAS BASED ON THE FOLLOWING HYPOTHESES:(1) BC WASH-OFF WOULD BE CONSTRUCTED OF DISSOLUTION OF BC DEPOSITED ON THE LEAF SURFACES AND LEACHING OF BC IN TREE TISSURES,(2) THE AMOUNTS OF BC WASH-OFF WOULD INCREASE WITH INCREASING LEAF AREA AND BC CONTENTS IN THE TREE. (2) VERIFICATION OF MODEL THE MODEL TO ESTIMATE TEMPORAL CHANGE IN BC WASH-OFF RATE WAS VERIFIED BY MEASUREMENTS IN A SIMULATED RAIN EXPOSURE EXPERIMENT USING FAGUS CRENATA,ABIES HOMOLEPIS,BETULA PLATYPHYLLA,AND CRYPTOMERIA JAPONICA. THE MODEL GAVE GOOD AGREEMENT WITH THE EXPERIMENTAL OBSERVATIONS,IF THE INTERCEPTIONRATE OF PRECIPITATION BY THE LEAVES OF THE CROWN IS INCLUDED. INDIVIDUAL OR INTERSPECIFIC DIFFERECES IN BC WASH-OFF RATE WARE EXPRESSED BY DIFFERENCES IN LEAF AREA,BC CONTENT IN TISSUES,AND PRECIPITATION INTERCEPTION RATE. (3) VARIABLE FACTORS OF BC WASH-OFF 1.BC WASH-OFF PER UNIT LEAF AREA INCREASED WITH RISING H+ CONCENTRATION IN THE SIMULATED RAIN. 2.INCREASING ATOMOSPHERIC SO2 CONCENTRATION IN THE RANGE FROM 0 TO 20 PPB,WHICH DID NOT INDUCE LEAF VISIBLE INJURIES,INCREASED SO42- AND BC WASH-OFF. THE RELATIONSHIP BETWEEN BC WASH-OFF AND SO2 CONCENTRATION SUGGESTS NEUTRALIZATION OF SO42- BY BC AT T

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