ⴘⴝฦよ㐛⛤࡞╌┘ࡊࡒ᲻ᯐ⏍ឺ⣌࡞ࡻࡾᅰቫ᭯ᶭ∸ࡡ㞗✒ᶭ⬗フ౮
Soil Organic Matter Storage in Forest Ecosystemwith Reference to Decomposition Processes of Leavesኬᅧ஽ྒྷா㒌ኬᏕ⏍ឺᏕ◂✪ࢬࣤࢰ࣭ ෶ᩅ᤭Takashi OSONO
Associate Professor, Center for Ecological Research, Kyoto University◂✪ࡡኬさ᲻ᯐ⏍ឺ⣌ࡢኬẴ୯ࡡ CO2 ࢅකྙᠺ࡞ࡻࡽ᭯ᶭ∸࡞ንᥦࡊࠉᶖమࡷⴘⴝ࡝࡜ࡡ
᳔∸㐿మࠉᅰቫ᭯ᶭ∸࡛ࡊ࡙㞗✒ࡌࡾࡆ࡛࡞ࡻࡽࠉኬẴ୯ࡡ CO2 ๎΅࡞ᐞ୙ࡊ࡙࠷ࡾࠊࡊ࠾ࡊࠉᅰቫ࡞࠽ࡄࡾⴘⴝࡡฦよ㐛⛤࡞ࡗ࠷࡙ࡢ୘᪺Ⅴ࠿ኣࡂࠉ᲻ᯐ
ࡡ CO2 ๎΅ᶭ⬗ࢅフ౮ࡌࡾ୕࡚ࡡ୘☔ᏽさ⣪࡛࡝ࡖ࡙࠷ࡾࠊᮇ◂✪࡚ࡢல⇍ᖈᯐࢅᑊ㇗࡛ࡊ࡙ࠉⴘⴝࡡฦよ㐛⛤࡛ࠉࡐࡿ࡞࡛ࡵ࡝࠹᭯ᶭ∸ࡡ↋ᶭ໩㸝CO2 ࡫ࡡ㑇ඔ㸞࡛ᅰቫ᭯ᶭ∸ࡡ⏍ᠺ࡛ࢅᐁッⓏ࣬ᏽ㔖Ⓩ࡞᪺ࡼ࠾࡞ࡌࡾࠊࡆࡿࡼᐁ㥺ࢸ
࣭ࢰࢅฦよ࣓ࢸࣜ࡞ᙔ࡙ࡢࡴࡾࡆ࡛࡞ࡻࡽࠉ᲻ᯐ⏍ឺ⣌ࡡ CO2 ๎΅ᶭ⬗࡞ᯕࡒࡌᅰቫ᭯ᶭ∸ࡡᙲ๪ࢅᏽ㔖Ⓩ࡞᪺ࡼ࠾࡞ࡌࡾࠊ
Abstract
Forest ecosystems transform carbon dioxide in the atmosphere into organic matters andsequestrate them as trees, dead leaves, and soil organic matter. Forest ecosystems thus
can contribute to the reduction of carbon dioxide in the atmosphere. Much remains to be
unknown, however, regarding the decomposition and accumulation processes of deadleaves on the soil. This leads to an uncertainty in the evaluation of the role of forest
ecosystems in carbon sequestration. The present study examines decomposition processof dead leaves in a subtropical forest in southern Japan and demonstrates the evolutionof carbon dioxide and the formation of soil organic matter. Models are applied to theresults of this field experiment to estimate carbon sequestration in the soil and evaluate
the role of belowground part in the reduction of carbon dioxide in the atmosphere.

-1-㸦㸣◂✪┘Ⓩࡡ㞗✒㔖ࡢࠉⴘⴝࡡ౩⤝㔖࡛ฦよ⩽⏍ ᲻ᯐ⏍ឺ⣌ࡢኬẴ୯ࡡ CO2 ࢅකྙ∸ࡡ௥ㅨ࡞ࡻࡾ↋ᶭ໩㔖㸝CO2 Ⓠ⏍ᠺ࡞ࡻࡽ᭯ᶭ∸࡞ንᥦࡊࠉᶖమࠉⴘⴝ㔖㸞࡛ࡡࣁࣚࣤࢪ࡚Ửᏽࡈࡿࡾࠊࡆࡡ࡝࡜ࡡ᳔∸㐿మࠉ࠽ࡻࡦᅰቫ᭯ᶭ∸࡛

࠹ࡔฦよ࣬௥ㅨࡡࣈࣞࢬࢪࡷࡐࡡᚂ㏷ࡊ࡙㞗✒ࡌࡾࡆ࡛࡞ࡻࡽࠉኬẴ୯ࡡさᅄ࡞ࡗ࠷࡙ࡢ୘᪺Ⅴ࠿ኣ࠷ࠊ≁࡞⇍

CO2 ๎΅࡞ᐞ୙ࡊ࡙࠷ࡾࠊᆀ୕㒂࡚ࡡᖈ࣬ல⇍ᖈᆀᇡ࡚ࡢୌ⯙࡞ฦよ࠿㏷࠷ᶖమ࡞ࡻࡾ᭯ᶭ∸㞗✒ࡢࠉᶖᮄ⩄ⴘࡡࡆ࡛࠿▩ࡼࡿ࡙࠷ࡾ࠿ࠉฦよ㏷ᗐࡷฦ⌟Ꮛ㔖࡛⏍㛏㔖ࡡῼᏽ࡞ࡻࡽレࡊࡂよ࡞࡛ࡵ࡝࠹ⴘⴝࡡᾐ኶㔖ࠉ᭯ᶭ∸㞗᳠ゞࡈࡿ࡙࠷ࡾࠊࡐࡡୌ᪁࡚ࠉᆀୖ㒂✒ࣈࣞࢬࢪࠉ࠽ࡻࡦฦよࡡᚂ㏷さᅄ࡞࡞ࡗ࠷࡙ࡢࠉᅰቫ᭯ᶭ∸ࡡ⌟Ꮛ㔖ࠉ࠽ࡗ࠷࡙ࡡ◂✪ౚ࠿ᑛ࡝࠷ࠊᮇ◂✪࡚ࡢࠉࡻࡦᆀ୕㒂࠾ࡼࡡⴘⴝ౩⤝㔖࠿ࡂࡽᮇ㑝ࡡ༞こ㒂࡞న⨠ࡌࡾல⇍ᖈᯐࢅ࠾࠻ࡊῼᏽࡈࡿ࡙࠷ࡾࡵࡡࡡࠉⴘⴝࡡ◂✪ᑊ㇗࡛ࡊ࡙ࠉⴘⴝࡡฦよࣈࣞࢬࢪฦよ࣬ᾐ኶㔖࡞ࡗ࠷࡙ࡢῼᏽౚ࠿ᑛ࡝ࢅᐁッⓏ࡞᪺ࡼ࠾࡞ࡊࡒࠊ

ࡂࠉ᲻ᯐࡡ CO2 ๎΅ᶭ⬗ࢅフ౮ࡌࡾ୕࡚ࡡ୘☔ᏽさ⣪࡛࡝ࡖ࡙࠷ࡾࠊᮇ◂✪㸧㸣◂✪⤊㐛࡚ࡢࠉࡆࡡⴘⴝࡡฦよࡡ㐛⛤ࢅᐁッⓏ ࣛࢰ࣭ࣁࢴࢡἪ㸝ᅒ 1㸞ࢅ⏕࠷ࡒ㔕࡞᪺ࡼ࠾ࡊࠉ᲻ᯐ⏍ឺ⣌ࡡᅰቫ᭯ᶭ∸አ࡚ࡡⴘⴝࡡฦよᐁ㥺ࢅ 2008 ᖳ 4 ᭮㞗✒࡞ࡻࡾ CO2 ๎΅࣒࢜ࢼࢫ࣑ࡡフ࡞㛜ጙࡊࡒࠊㄢᰕᆀࡢἀ⦎ᮇᓞࡡ໪㒂౮⢥ᗐࡡྡྷ୕ࢅ┘ᣞࡌࡆ࡛ࢅ┘Ⓩ࡛

࡞న⨠ࡌࡾࠉ㏳⛘ࠔࡷࢆࡣࡾࠕ࡛ࡻࡣࡌࡾࠊࡿࡾல⇍ᖈᖏ⥫ᗀⴝᶖᯐ࡚࠵ࡾࠊᮞᩩ ᅰቫ࡞౩⤝ࡈࡿࡒⴘⴝࡢࠉⳞ㢦ࡷᅰ

࡛ࡊ࡙ 12 ⛸ࡡ᳔∸ⴝࢅ⏕࠷ࡒࠊ2009ቫິ∸࡛࠷ࡖࡒᅰቫ⏍∸࡞ࡻࡾᏽ╌ᖳ 3 ᭮ࡱ࡚ࡡ 1 ᖳ㛣࡞ࢂࡒࡽࠉ3 ࣧ᭮

࡛ฦよࢅུࡄࡾࠊᅰቫ⏍∸࡞ࡻࡽ௥ㅨ

࠽ࡀ࡞ 4 ᅂࠉⴘⴝࡡ㔔㔖ን໩ࢅㄢ࡬ࡒࠊ

ࡈࡿࡒⴘⴝ୯ࡡ᭯ᶭ∸ࡢ CO2 ࡛ࡊ࡙ኬẴ୯࡞㑇ඔࡈࡿࡾࠊⴘⴝࡡṟ῵ࡵ᭩
⤂Ⓩ࡞ࡢฦよࢅུࡄ࡙ CO2 ࡫࡛ን໩ࡌࡾ࠿ࠉୌ㒂ࡢᅰቫ᭯ᶭ∸࡛ࡊ࡙㛏᭿
Ⓩ࡞⁣⏻ࡌࡾࠊࡆࡡࡻ࠹࡞ⴘⴝࡡฦよࡡ㐛⛤ࡢࠉᅰቫ᭯ᶭ∸ࡡ㞗✒࡞ᐞ୙ࡌࡾࡡࡲ࡝ࡼࡍࠉᅰቫ࠾ࡼࡡ CO2 ᨲฝࢅࢤࣤࢹ࣭ࣞࣜࡊࠉᶖᮄࡡකྙᠺ࡞࡛ࡖ
࡙୘ྊḖࡡ✽⣪࡝࡜ࡡ㣬ฦ∸㈻ࢅ౩
⤝ࡌࡾᶭ⬗ࢅᢰࡖ࡙࠷ࡾࠊᅰቫ᭯ᶭ∸ᅒ 1㸯ࣛࢰ࣭ࣁࢴࢡฦよᐁ㥺㸣-2-㸨㸣◂✪ᠺᯕ࠷ࢅཬ᫆ࡊ࡙ࠉࣕࣇࢵࣁ࢞ࡡ 0.55㸤ᖳ ⴘⴝࡡฦよ㏷ᗐࡢ᳔∸⛸㛣࡚ኬࡀ࠾ࡼ࢓࣒࢜࢝ࢨ࣠ࡡ 2.56㸤ᖳࡱ࡚ࡡࡂ␏࡝ࡖࡒ㸝ᅒ㸧㸞ࠊฦよ 1 ᖳ┘ࡡⴘ⠂ᅑ࡞࠵ࡖࡒࠊ12 ᳔∸⛸ࡡฦよ㏷ᗐⴝࡡ㔔㔖ṟᏋ⋙㸝ิ᭿㔔㔖࡞ᑊࡌᏽᩐࡡᖲᆍࡢ 1.05㸤ᖳ࡚࠵ࡖࡒࠊࡆࡿ

ࡾ㸚㸞ࡢࠉ࢓࣒࢜࢝ࢨ࣠ࡡ 18㸚࠾ࡼ

ࡼࡡฦよ㏷ᗐᏽᩐ࠾ࡼịࡴࡒⴘⴝ㔔ࢰ࢕࣠ࣤࣀࣤࢿ࢞ࡡ 63㸚ࡱ᳔࡚∸⛸㔖ࡡ༖΅᭿ࡢࠉ0.3ࠤ1.3 ᖳࠉ12 ᳔∸⛸㛣࡚ኬࡀ࡝ᕣ࠿ヾࡴࡼࡿࡒࠊࡡ༖΅᭿ࡡᖲᆍࡢ 0.8 ᖳ࡛᥆ᏽࡈࡿࡒࠊ ࡆࡡ 1 ᖳ㛣࡞ࢂࡒࡾṟᏋ㔔㔖ࡡࢸ

 12 ᳔∸⛸ࡡⴘⴝࡡฦよ㏷ᗐᏽᩐ࡛ࠉ

࣭ࢰ࡞ᣞᩐ㛭ᩐ࣓ࢸࣜ㹐y=exp-kt㸰y ࡢⴘⴝࡡࡈࡱࡉࡱ࡝ᛮ㈻࡛ࡡ㛭㏻ᛮࢅ

㔔㔖ṟᏋ⋙ࠉt ࡢ᫤㛣㸝ᖳ㸞ࠉk ࡢฦよよᯊࡊࡒࠊࡐࡡ⤎ᯕࠉิ᭿ࣛࢡࢼ⃨ࣤ㏷ᗐᏽᩐ㸝㸤ᖳ㸞㹒ࢅᙔ࡙ࡢࡴࡾࡆ࡛

ᗐ࡛ฦよ㏷ᗐᏽᩐ࡛ࡡ࠵࠷ࡓ࡞᭯ណ

࡚ฦよ㏷ᗐࢅ᥆ᏽࡊࡒࠊ࣓ࢸࣜࢅᙔ࡙

࡝ㇿࡡ┞㛭㛭౿࠿ヾࡴࡼࡿࡒ㸝R=0.69ࠉ

ࡢࡴࡒ࡛ࡀࡡỬᏽ౿ᩐࡢ 0.87ࠤ0.99

n=12ࠉP<0.05㸞㸝ᅒ㸨㸞ࠊ㸝n=5㸞࡛࡝ࡖࡒࠊฦよ㏷ᗐᏽᩐࡢ᳔ ᮇㄢᰕᆀ࡚ࡢࠉᖳ㛣ࡡⴘⴝ౩⤝㔖࠿∸⛸㛣࡚ࡡⴘⴝࡡฦよࡊࡷࡌࡈࡡ㐢ࣉࢠࢰ࣭ࣜ࠵ࡒࡽ 5.1 ࢹ࡛ࣤ᥆ᏽࡈࡿ-3-ࡾⴘⴝ㔖ࡢ 2.7 ࢹ࡛ࣤ࡝ࡾࠊࡆࡿ࡞ࡻ
ࡽࠉ඙࡮࡜ࡡᖲᆍೋ࡞ᇱࡘࡂゝ⟤ೋ
3.1 ࢹࣤ࡞Ẓ࡬࡙⣑ 24㸚ࡡ CO2 ᤴฝ๎΅࠿ྊ⬗࡛࠷࠹ゝ⟤࡛࡝ࡾࠊ㸩㸣௑ᚃࡡㄚ㢗࡛Ⓠᒈ ௑ᅂࡢ 1 ᖳ㛣ࡡฦよࢸ࣭ࢰ࡞ᇱࡘ
ࡂ᥆ᏽࢅ⾔ࡖࡒࠊࡊ࠾ࡊฦよࡢ㛏᭿Ⓩ࡝ࣈࣞࢬࢪ࡚࠵ࡽࠉ1 ᖳ㛣ࡡ▯᭿Ⓩ࡝ࢸ࣭ࢰ࡞ᇱࡘࡂ᥆ᏽ࡚ࡢ୘☔ᐁᛮ࠿㧏࠷ࠊ≁࡞ல⇍ᖈᯐࡡⴘⴝฦよⳞ㢦ࡢᅰቫ᭯ᶭ∸ࢅὩⓆ࡞ฦよࡌࡾࡆ࡛࠿
ࢂ࠾ࡖ࡙࠷ࡾ㸝Osono et al. 2008㸞ࠊ௑ᚃࡵ⤽⤾ࡊ࡙ฦよᐁ㥺ࢅᐁ᪃ࡊࠉ㛏᭿࡙࠷ࡾࠊ௑ᅂᚋࡼࡿࡒฦよ㏷ᗐᏽᩐࡡ

Ⓩ࡝ࢸ࣭ࢰ࡞ᇱࡘ࠷࡙᲻ᯐᅰቫࡡᢰ

ᖲᆍೋࢅ⏕࠷࡙ゝ⟤ࡌࡾ࡛ࠉ1 ᖳ㛣࡚࠹ኬẴ୯ࡡ CO2 ๎΅࣒࢜ࢼࢫ࣑ࡡフิ᭿㔔㔖ࡡ 61㸚࡞࠵ࡒࡾ 3.1 ࢹࣤ࠿ฦ౮⢥ᗐࢅྡྷ୕ࡈࡎࡾᚪさ࠿࠵ࡾࠊ㣬ฦよ࡞ࡻࡽ኶ࢂࡿࠉ39㸚࡞࠵ࡒࡾ 2.0 ࢹ∸㈻ࡡᏽ㔖ฦᯊࢅ⾔࠷ࠉᅰቫ᭯ᶭ∸ࡡࣤ࠿ṟᏋࡌࡾࠊฦよ࡞ࡻࡽ኶ࢂࡿࡒⴘ

㞗✒㔖ࡡቌຊ࠿ⴘⴝ࠾ࡼࡡ㣬ฦᨲฝ

ⴝ୯ࡡ⅛⣪ࡢࠉࡐࡡኬ㒂ฦ࠿ኬẴ୯࡞࡞ཀྵ࡯ࡌᙫ㡢ࢅ᳠ゞࡌࡾᚪさ࠿࠵ࡾࠊCO2 ࡛ࡊ࡙ᤴฝࡈࡿࡾࠊฦよ㏷ᗐ࡛ิ ᮇ◂✪ࡢࠉࡆࡿࡱ࡚࠵ࡱࡽἸ┘ࡈࡿ᭿ࣛࢡࢼ⃨ࣤᗐ࡛ࡡ࠵࠷ࡓ࡞᭯ណ࡝ㇿࡡ┞㛭㛭౿࠿ヾࡴࡼࡿࡒࡆ࡛࠾ࡼࠉ
ࣛࢡࢼ⃨ࣤᗐࡡ㧏࠷᳔∸⛸ࠉ௑ᅂࡡᐁ

࡙ࡆ࡝࠾ࡖࡒᅰቫฦよ⣌࡞ࡻࡾ CO2๎΅࣒࢜ࢼࢫ࣑ࢅ᳠ゞࡊࡒ࣓ࢸࣜࢢ
࣭ࢪ࡛ࡊ࡙ࠉ௑ᚃࡈࡱࡉࡱ࡝᲻ᯐ⏍ឺ㥺ᑊ㇗᳔∸࡚࠷࠹࡛ࢰ࢕࣠ࣤࣀࣤࢿ

⣌ࡡᶭ⬗フ౮࡞㝷ࡊ࡙᭯⏕࡝ᡥἪࢅ࢞ࠉ࣏ࣛࣖࢗ࢞ࣖࢗࢵࠉࢰࣇࢿ࢞ࠉ࢕ᥞ౩ࡌࡾࡵࡡ࡛᭿ᙽ࡚ࡀࡾࠊ

ࢪࢿ࡛࢞࠷ࡖࡒᶖ⛸ࡡ┞ᑊ㔖࠿᲻ᯐහ࡚ቌຊࡌࡿࡣࠉᅰቫ࡞㞗✒ࡌࡾⴘⴝ

㸪㸣Ⓠ⾪ㄵᩝࣛࢪࢹ㸝༰ใ୯ࡵྱࡳ㸞㔖ࢅቌຊࡈࡎࠉฦよ࡞࡛ࡵ࡝࠹ CO2Osono, T., Ishii, Y., Hirose, D. (2008)ᤴฝࢅᢒโ࡚ࡀࡾྊ⬗ᛮ࠿࠵ࡾࠊౚ࠻

Fungal colonization and decompositionࡣࠉࢰ࢕࣠ࣤࣀࣤࢿ࢞㸝ࣛࢡࢼ⃨ࣤᗐ

of Castanopsis sieboldii leaves in a44.1㸚㸞࠿ᖳ㛣ⴘⴝ౩⤝㔖ࡡ 100㸚ࢅ

subtropical forest. Ecological Research༥ࡴࡾ࡛௫ᏽࡊࡒሔྙࠉ1 ᖳ㛣࡞ฦよ23: 909-917.

࡚ᾐ኶ࡌࡾⴘⴝ㔖ࡢ 2.4 ࢹࣤࠉṟᏋࡌ-4-