J. Jpn. Soc. Soil Phys.
౔৕ͷ෺ཧੑ

No. 124, p.17 ∼ 24 (2013)ଟप೾਺ి࣓୳ࠪ๏ʹΑΔ৿ྛͷ؅ཧ͕౔৕‫ʹڥ؀‬༩͑ΔӨ‫ڹ‬ධՁ‫ٶ‬ຊचະ 1 · ઒‫ ͔Ͳ·ݪ‬2 · ৿ɹ໵ੇࢤ 1 · फଜ޿ত 2 · Ҫख३Ұ࿠ 3 ·ߴ‫ڮ‬ֆཬಸ 2 · ถɹ߁ॆ 2 · ຤‫ܧ‬ɹ३ 1

Evaluation of management practices in forest soil environments using a multi-frequency
electromagnetic sounding system
Tamami MIYAMOTO 1 , Madoka KAWAHARA2 , Yasushi MORI1 , Hiroaki SOMURA2 , Jun’ichiro IDE3 ,Erina TAKAHASHI2 , Yasumichi YONE2 , and Atsushi SUETSUGU1

Abstract: A multi-frequency electromagnetic sounding
system (MFEM) enables non-destructive and instantaneous measurements of soil electrical conductivity (EC)proﬁles. Because agricultural and forest lands are possible sources of pollutant loads transported to aquatic environments, we applied MFEM to develop a procedure for
conducting efﬁcient soil environmental surveys for evaluation of management practices on forested lands. We investigated two types of forested sites: thinning sites (TS)and delayed thinning sites (DTS). The MFEM-EC data collected from surface soils were well correlated with the EC
data collected by a conventional sensor. MFEM-EC mapping revealed higher EC values in surface soils of DTS.
Delayed thinning had reduced understory vegetation andhydraulic conductivity of surface soils. Therefore, lowplant uptake and shallow inﬁltration of soluble salts would
have allowed them to remain in the surface soils of DTS.
Forest sites that had been fertilized as farmlands could also
be distinguished with an MFEM system. The proposed
MFEM system would be a useful tool for screening surveys of forested sites prior to detailed analysis of a wider
area.
Key Words : multi-frequency electromagnetic sounding,electrical conductivity, inﬁltration, soil environment

1. ͸͡Ίʹ
ۙ೥ɼ೔ຊͰ͸೶ߞ࡞ͷਰୀͱ஍ҬॅຽͷߴྸԽ͕ਐ
ߦ͓ͯ͠ΓɼͦΕʹͱ΋ͳ͍ɼ؅ཧ์‫͞غ‬ΕΔ೶ྛ஍͕૿͑࢝Ί͍ͯΔʢ೶ྛਫ࢈ল, 2012; େ‫ݪ‬, 2007ʣɽਫా΍ാ஍͕์ஔ͞ΕΔͱɼू໿త೶‫ʹۀ‬Αͬͯ౔৕தʹ஝ੵͨ͠ංྉ੒෼͕࡞෇͚ʹར༻͞Εͳ͍··ɼ‫ڧ‬Ӎͱͱ΋
1 Graduate School of Environmental and Life Science, Okayama Uni-

versity, 3-1-1 Tsushimanaka, Okayama 700-8530, Japan. Corresponding
authorɿ৿ɹ໵ੇࢤɼԬࢁେֶେֶӃ‫ڥ؀‬ੜ໋Պֶ‫ڀݚ‬Պ
2 Graduate School of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan.
3 Joensuu Research Unit, Finnish Forest Research Institute, P.O. Box 68,
80101 Joensuu, Finland.
2012 ೥ 8 ݄ 29 ೔डߘɹ 2013 ೥ 4 ݄ 5 ೔डཧʹՏ઒ʹྲྀग़͢ΔՄೳੑ͕͋Δɽ·ͨɼะ৔͔ΒӫཆԘΛ‫ؚ‬Ή౔͕࠭ྲྀ๢͢Δ՝୊͕ใࠂ͞Ε͓ͯΓɼ೶ྛ஍؅
ཧͷ͋Γํ͕ٞ࿦͞Ε͍ͯΔʢେᖒΒ, 2004a, 2004bʣɽ৿ྛʹ͓͍ͯ͸ɼੲ͸ఆ‫ظ‬తʹߦΘΕ͍ͯͨؒെʹ஗ΕͳͲ͕‫ݟ‬ΒΕΔΑ͏ʹͳΓɼྛচ΁ͷޫͷःஅ͔ΒԼ૚২ੜ͕ශऑԽ͍ͯ͠Δྫ͕ใࠂ͞Ε͍ͯΔʢਗ਼໺, 1988;
Ըా, 2008; ‫ٴ‬઒, 1977; ౬઒Β, 1995ʣɽ౔஍ͷར༻ঢ়‫ʹگ‬Ө‫͞ڹ‬ΕΔ໘‫ݯ‬ෛՙʹ͍ͭͯ͸ɼ͜
Ε·ͰྲྀҬͷਫ‫ڥ؀‬Λத৺ʹௐࠪ͞Ε͖ͯͨʢࠃ౔ަ௨
লՏ઒‫ہ‬, 2006ʣɽྲྀҬશମͷௐࠪʹ͓͍ͯ͸ɼՏ઒ਫΛ࠾औ · ෼ੳ͢Δ͜ͱʹΑͬͯɼՏ઒ͷԚ୙ෛՙྔΛ‫ܭ‬ଌ͠ɼԚ୙ෛՙ‫ݯ‬Λਪఆ͢Δ͜ͱ͕ଟ͘ߦΘΕ͓ͯΓɼେ͖ͳ੒ՌΛಘ͍ͯΔʢ෢ా, 2002; ҏ౻Β, 2004ʣɽ͔͠͠ɼՏ઒ਫΛத৺ͱ͢Δਫ‫ڥ؀‬ͷσʔλ͸໘‫ݯ‬ෛՙൃੜͷ݁ՌͰ͋ΔͨΊɼ৿ྛ΍ాാ͔ΒͷൃੜͷաఔΛߟ࡯
͢Δ͜ͱ͸೉͍͠ɽ·ͨɼਫ͕ଘࡏ͢Δ৔ॴͰͳ͚Ε͹ࢼྉͷ࠾औࣗମ͕Ͱ͖ͳ͍ɽͦͷͨΊɼສวͳ͘ྲྀҬશମΛௐࠪ͢Δ͜ͱ͸ࠔ೉Ͱ͋Δɽ
Ԛ୙ෛՙൃੜͷաఔΛௐ΂Δํ๏ͱͯ͠ɼҰൠతʹ͸౔৕ௐ͕ࠪߦΘΕ͍ͯΔʢ࢙Β, 2002ʣɽ͔͠͠ɼ೶ྛ
஍Ͱͷ౔৕ௐࠪ͸ௐࠪൣғ͕޿ҬͰ͋ΔͨΊɼେมͳ࿑ྗͱ͕࣌ؒඞཁͰ͋Δɽ·ͨɼ౔৕ௐࠪͰΞΫηεͰ͖Δͷ͸஍ද͔Β͍͍ͤͥ਺े cm ·ͰͰ͋Δʢ৿Β,
2010aʣɽ͞Βʹɼࢲ༗஍ͷะ৔Λ۷Δ౔৕ௐࠪʹ͸஍‫ݖ‬ऀͷཧղ͕ಘʹ͍͘৔߹΋͋Γɼଟ఺ͰͷௐࠪΛ࣮‫Ͱݱ‬͖ͳ͍͜ͱ͕͋Δɽ
ͦ͜Ͱɼ໘‫ݯ‬ෛՙͷ‫͋Ͱݯ‬Δ౔৕‫ڥ؀‬ͷௐࠪΛɼଟप೾਺ి࣓୳ࠪ๏ʢMcNeil, 1980; Ward and Hohmann,

1987ʣΛ༻͍ͯɼ޿ൣғΛޮ཰త͔ͭ୹࣌ؒʹߦ͏͜ͱΛߟ͑ͨɽ͜ͷ୳ࠪ๏Ͱ͸ɼҟͳΔෳ਺ͷप೾਺͝ͱʹి‫఻ؾ‬ಋ౓ͱଳ࣓཰ʢWon et al., 1996; ޫാΒ, 2005ʣ͕ಘΒΕɼ͜ΕΒͷ஍൫தͷ৘ใ͸ɼ஍໘ʹ;ΕΔ͜ͱͳ
͘ඇഁյతʹಘΔ͜ͱ͕Ͱ͖Δɽ͞Βʹɼ͜ΕΒͷ਺஋͸ඵ୯ҐͰಘΒΕΔͨΊਝ଎ʹ౔৕ · ஍൫‫ڥ؀‬Λௐࠪ͢
Δ͜ͱ͕ՄೳͰ͋ΔʢHuang and Won, 2000ʣɽൺ఍߅๏

౔৕ͷ෺ཧੑɹୈ 124 ߸ɹ (2013)18

Ͱ͸౸ୡਂ౓ΛಘΔͨΊʹ޿͍ి‫͕཭ڑؒۃ‬ඞཁͰ͋ΔมԽΛௐ΂Δ͜ͱ͕Ͱ͖ΔɽҰൠʹɼप೾਺ͱਂ౓ͷؔ

ʢKeller and Frischknecht, 1966ʣ͕ɼଟप೾਺ి࣓୳ࠪ๏

܎͸ɼप೾਺͕ߴ͍ి࣓೾͸ઙ૚෦෼ͷ஍൫ঢ়‫گ‬ΛɼपͰ͸प೾਺Λม͑Δ͜ͱͰඞཁͳ౸ୡਂ౓ͷ৘ใ͕ಘΒ೾਺͕௿͍ి࣓೾͸ਂ૚෦෼ͷ஍൫ͷঢ়‫گ‬Λ൓ө͢Δɽ

ΕΔͨΊɼগਓ਺Ͱௐ͕࣮ࠪࢪͰ͖Δɽ·ͨి࣓೾Λ৵ͨͩ͠஍࣭ͷӨ‫ڹ‬΋ಉ࣌ʹ൓ө͞ΕΔ͜ͱͱɼ఍߅஋͕

ೖͤͨ͞஍఺Ͱಉ࣌ʹσʔλΛऔಘ͍ͯ͠ΔͨΊɼϙΠେ͖͍৔߹ʹ͸஋ͷมԽΛͱΒ͑ʹ͍ͨ͘Ί஫ҙ͕ඞཁϯτຖʹશͯͷσʔλ͕୯ಠͰಘΒΕɼൺ఍߅τϞάϥͰ͋ΔɽϑΟʔͷΑ͏ͳ‫ٯ‬ղੳΛඞཁͱ͠ͳ͍ɽ
ͳҧ͍Λநग़͢ΔͨΊʹి‫఻ؾ‬ಋ౓໿ 100 mS m−1 ͷมௐࠪʹ͸ଟप೾਺ి࣓୳ࠪ๏ʢMcNeil, 1980; Ward andHohmann, 1987ʣΛ༻͍ͨɽ͜Ε͸ి‫཭ڑؒۃ‬ΛมԽ͞
ͤΔ୅ΘΓʹɼ1 ඵҎ಺ʹ࠷େ 5 ͭͷप೾਺Λ஍໘ʹ৵ԽΛ୳ࠪ͢Δ࣮‫͕ݧ‬ʢޫാΒ, 2005ʣ
ɼ·ͨւ‫؛‬ฏ໺Ͱ͸ɼ

ೖͤ͞Δɽप೾਺ຖʹి࣓೾ͷ౸ୡਂ౓͕ҟͳΔͨΊɼԘਫͱਅਫͱ͍ͬͨՄ༹ੑԘྨͷೱ౓ͷେ͖ͳҧ͍Λ‫ݕ‬ͦͷ஍൫͔ΒͷԠ౴Ͱ͋Δి‫఻ؾ‬ಋ౓Λ΋ͬͯଟਂ౓ͷ

ग़͢ΔͨΊʹి‫఻ؾ‬ಋ౓໿ 1000 mS m−1 ͷมԽʹ͍ͭ౔৕ · ஍൫‫ڥ؀‬Λߟ࡯͢Δ΋ͷͰ͋ΔʢHuang and Won,ͯ୳͕ࠪʢMitsuhata et al., 2006ʣߦΘΕ͍ͯΔɽຊ‫ڀݚ‬

2000; ޫാΒ, 2005ʣɽͳ͓ɼ‫ܭ‬ଌͰ͸ಉ࣌ʹଳ࣓཰͕ಘ

Ͱର৅ͱ͢Δ೶஍΍৿ྛ͸ి‫఻ؾ‬ಋ౓͕਺े mS m−1 ҎΒΕΔ͕ຊ‫Ͱڀݚ‬͸࢖༻͍ͯ͠ͳ͍ɽ

͜Ε·Ͱʹɼਓ޻஍൫಺΁ͷ࿙ਫͱ͍͏ਫ෼ྔͷେ͖ԼͰɼ͜Ε·Ͱใࠂ͞Ε͖ͯͨ‫ݱ‬৔ΑΓ఻ಋ౓͕௿͘ɼ

ి‫ؒۃ‬Λม͑ΔखؒΛऔΒͣʹɼ୹࣌ؒͰଟਂ౓ͷ৘ͦͷਫ෼ͷมಈ෯΋খ͍͞ɽ·ͨɼ஍ֶ࣭෼໺ͰѻΘΕใΛಘΔ͜ͱ͕Ͱ͖ΔͨΊɼՄൖੑͱਝ଎ੑʹ༏Εɼ໘

Δ਺े͔Βඦ m ͱ͍͏ΦʔμʔΑΓ΋ 1 m ະຬͷද૚ੵతʹେ͖ͳ޿͕ΓΛ࣋ͭ৔ॴͷௐࠪʹ͸దͨ͠૷ஔ

ͷ౔৕ʹ஫໨͢Δඞཁ͕͋ΔɽฏҪΒʢ2008ʣ͸ɼ૷ஔ

Ͱ͋Δͱ͍͑Δʢޫാ, 2006; ৿Β, 2010bʣɽຊ‫༻Ͱڀݚ‬ͷ࠷ߴप೾਺Ͱ͋Δ 48 kHz ʹ஫໨͢ΔͱɼਫాͰ͸ਫ෼ͷมಈ͕‫͖Ͱ࡯؍‬ɼ·ͨാ஍΍ՌथԂͰ͸ࢪංͷӨ‫ڹ‬͍ͨଟप೾਺ి࣓୳ࠪ‫ػ‬͸ɼถࠃ Geophex ࣾͷ GEM-2
broadband EMI sensor Ͱ͋Δɽ͜ͷγεςϜ͸ɼখ͞ͳͱ‫ݟ‬ΒΕΔి‫఻ؾ‬ಋ౓ͷߴ͍෦෼͕ද૚෇ۙʹ‫͞࡯؍‬Εૹ৴ίΠϧͱड৴ίΠϧΛ༻͍ͯɼి‫఻ؾ‬ಋ౓ͱଳ࣓཰

Δ͜ͱΛใࠂ͍ͯ͠Δɽ·ͨɼ৿Βʢ2010aʣ͸ɼද૚෦‫ܭ‬ଌΛՄೳʹ͍ͯ͠Δɽͭ·Γɼૹ৴ϧʔϓ͔Βมಈ࣓෼ͷి‫఻ؾ‬ಋ౓ͱۙ͘ΛྲྀΕΔഉਫ΍ૃਫͷి‫఻ؾ‬ಋ౓քΛൃੜͤ͞Δͱɼ౔৕ · ஍൫தʹϨϯπͷ๏ଇʹΑΓʹߴ͍૬͕ؔ͋Δ͜ͱΛใࠂ͍ͯ͠Δɽ஍࣭ௐࠪͳͲʹ‫ൃ͕ྗిى‬ੜ͠ɼ౔৕ͷൺ఍߅ʹԠͯ͡༠ಋిྲྀʢӔి࢖ΘΕΔి࣓୳ࠪͰ͸ຊདྷϘʔϦϯάͳͲʹΑΔਂ͞ํ

ྲྀʣ͕ൃੜ͢Δɽ ͦͯ͠ɼͦͷ༠ಋిྲྀʹΑͬͯ৽ͨʹ޲ͷσʔλͷ‫͕͍ͳ͔͕ͤܽূݕ‬ɼࢲ༗஍Ͱ͋Δ೶ྛ஍

ੜ͡Δೋ࣓࣍৔ Hs ͱҰ࣓࣍৔ Hp Λड৴ϧʔϓʹͯ஍දͰ͸ඇৗʹ೉͍͠ɽͱ͜Ζ͕ᕲᕱ΍ࢪංͱ͍ͬͨ೶ྛ஍

͔Βͷηϯαʔߴ͞ h Ͱ‫؍‬ଌ͠ɼ‫ط‬஌Ͱ͋ΔҰ࣓࣍৔ Hp

ʹ͓͚Δਓؒ‫׆‬ಈͷӨ‫ڹ‬͸ൺֱతઙ͍ͱ͜Ζʹ‫͞࡯؍‬ΕΛ஍൫΁ͷೖྗ৴߸ͱ͠ɼೋ࣓࣍৔ Hs Λड৴৴߸ͱ͠

Δ͜ͱ͕໌Β͔ʹͳ͖ͬͯͨɽैͬͯɼ౔৕‫ڥ؀‬ௐࠪʹͯ‫؍‬ଌ͢Δɽͦͷ͔ࠩΒ౔৕ · ஍൫தͷൺ఍߅஋ͷ‫਺ٯ‬‫ݶ‬ఆ͢Ε͹ɼઙ͍૚ʹ஫໨͢Δ‫ݶ‬Γʹ͓͍ͯ͸‫͕ূݕ‬ൺ

Ͱ͋Δి‫఻ؾ‬ಋ౓͓Αͼଳ࣓཰Λଌఆ͢Δ୳ࠪ๏Ͱ͋Δ

ֱత༰қʹͳΓɼి࣓୳ࠪʹΑΔ౔৕‫ڥ؀‬ௐࠪͷՄೳੑ

ʢFig. 1ʣɽ͜ͷଌఆγεςϜ͸ɼҰൠతʹϧʔϓ · ϧʔϓΛ֦͛ΒΕΔɽ๏ʢWon et al., 1996; Mitsuhata et al., 2006ʣͱ‫ݺ‬͹ΕΔຊ‫Ͱڀݚ‬͸ɼ೔ຊͷ໘ੵͷେ෦෼Λ઎ΊɼྲྀҬʹ͓͚୳ࠪ๏Λར༻͍ͯ͠Δɽૹ৴ · ड৴ϧʔϓͷִؒ͸ 1.66

Δ্ྲྀ෦Λ‫ܗ‬੒͢Δ৿ྛʹண໨ͨ͠ɽલड़ͨ͠Α͏ʹɼ‫ڥ؀‬ͷಛ௃ΛޮՌతʹநग़͠ɼߟ࡯Ͱ͖Ε͹େม༗ޮͰ

m ͰɼಉҰͷ൘ʹ‫ݻ‬ఆ͞Ε͓ͯΓɼ330 Hz ∼ 47970 Hzͷ࠷େ 15 ͷप೾਺ͷૹड৴͕ՄೳͰ͋ΔɽҰൠతʹɼ3∼ 5 ͭͷप೾਺Λ༻͍ͯଌఆ͢Δɽલड़ͷΑ͏ʹɼप೾͋Δɽ·ͨɼࢲ༗஍͕େଟ਺Λ઎ΊΔ౔஍ͰεΫϦʔχ਺ͱਂ౓ͷؔ܎͸ɼप೾਺͕ߴ͍ి࣓೾͸ઙ૚෦෼ͷ஍ϯάతʹඇ઀৮Ͱௐ͕ࠪͰ͖Ε͹ɼͦͷ‫ޙ‬ͷৄࡉௐࠪͷ൫ঢ়‫گ‬Λɼप೾਺͕௿͍ి࣓೾͸ਂ૚෦෼ͷ஍൫ͷঢ়‫گ‬ޮ཰্͕͕ΔɽΛ൓ө͢ΔʢWon et al., 1996; Huang, 2005ʣɽຊ‫Ͱڀݚ‬౔࠭ͷྲྀ๢΍Լ૚২ੜͷශऑԽ͕ใࠂ͞Ε͓ͯΓɼ౔৕ຊ‫ڀݚ‬ͷ໨త͸ɼؒെ஗Εͷ‫ݟ‬ΒΕΔ৿ྛʹ͓͍ͯɼʢ1ʣଟप೾਺ి࣓୳ࠪ‫ػ‬Λ༻͍ͯɼ౔৕‫ڥ؀‬ͷಛ௃நग़ΛࢼΈɼʢ2ʣ౔৕ͷಛੑΛࣔ͢ଞͷσʔλ͔Β‫ݪ‬ҼΛ୳Γɼʢ3ʣ৿ྛͷ؅ཧ͕౔৕‫ʹڥ؀‬༩͑ΔӨ‫ڹ‬ΛධՁ͢Δ
͜ͱͰ͋Δɽ

2. ి࣓୳ࠪͷଌఆ‫ݪ‬ཧEM ୳ࠪͱ͸ɼElectro-Magnetic-methodsʢి࣓๏ʣͱ
‫ݺ‬͹ΕΔి࣓୳ࠪͷҰछͰɼ஍தʹ͓͚Δ༠ಋి࣓৔ͷԠ౴͔Βɼ஍൫ͷൺ఍߅஋ͷ‫͋Ͱ਺ٯ‬Δ఻ಋ཰ʢconductivityʣ͓Αͼଳ࣓཰ʢmagnetic susceptibilityʣΛଌఆ͢Δ
ํ๏Ͱ͋ΔɽEM ୳ࠪ͸ɼి࣓೾΍प೾਺ͷҧ͍ʹΑͬͯ৵ೖਂ౓͕ҟͳΔ͜ͱΛར༻͠ɼਂ౓ํ޲ͷ఻ಋ཰ͷ

Fig. 1 ଟप೾਺ి࣓୳ࠪ๏ͷଌఆ‫ݪ‬ཧɽ
Theory for multi-frequency electromagnetic sounding method.

࿦จɿଟप೾਺ి࣓୳ࠪ๏ʹΑΔ৿ྛͷ؅ཧ͕౔৕‫ʹڥ؀‬༩͑ΔӨ‫ڹ‬ධՁ

19

bridge, UKʣΛ౥ࡌ͠ɼҐஔ৘ใͱซͤͯσʔλΛऔಘͨ͠ɽຊ‫Ͱڀݚ‬͸ɼਫฏͰͷ఻ಋ౓෼෍ʹซͤͯɼฏҪΒʢ2008ʣͷΑ͏ʹ֤αΠτͷԖ௚அ໘ͷ఻ಋ౓෼෍΋ߟ࡯ର৅ͱ͢ΔͨΊɼۣ‫ܗ‬ঢ়ʹௐࠪαΠτΛઃఆ͠ɼ2ɼ3

m ִؒͰ͍ͭ͘΋ฏߦઢΛඳ͘Α͏ʹา͖ͳ͕Β‫ܭ‬ଌΛߦͬͨɽͳ͓ɼຊ࿦จͰ͸ɼ஍൫΍౔৕ͷ‫ݻ‬ӷ‫ؾ‬૬૯ମͷి‫఻ؾ‬ಋ౓ʢbulk ECʣ·ͨ͸‫͚͔ݟ‬ͷి‫఻ؾ‬ಋ౓Λ‫ܭ‬ଌ͍ͯ͠Δɽऔಘͨ͠σʔλ͸ CSV ϑΝΠϧͱͯ͠ఏ‫͞ڙ‬ΕΔͨΊɼUSB γϦΞϧέʔϒϧΛ௨ͯ͡ύιίϯʹऔΓࠐΈɼσʔλΛม‫ޙͨ͠׵‬ɼάϥϑσβΠϯιϑ
τʢSurfer8, Golden software, USAʣͰ‫͚͔ݟ‬ͷి‫఻ؾ‬ಋ౓ͷ౳ೱ౓ઢਤΛ࡞੒͠ɼ؅ཧঢ়ଶ͕౔৕‫ʹڥ؀‬༩͑ΔӨ‫ڹ‬ΛධՁͨ͠ɽ͞Βʹɼ౔৕ηϯαʔʢHydra Probe II,
Fig. 2 ௐࠪ஍ɿౡࠜ‫ݝ‬Ӆ‫܊ذ‬Ӆ‫ذ‬ͷౡɽ
Location of investigated sites: Oki-island in Shimane, Japan.

͸ɼௐࠪର৅ͱ͢Δਂ͞͸͓Αͦ 0.5 ∼ 10 m Ͱ͋Δ͜ͱΑΓɼి࣓୳ࠪʹ͓͚Δ୳ࠪਂ౓Ͱ͋Δදൽਂ౓ʢSpies,

1989ʣΛߟྀͯ͠ɼௐࠪप೾਺Λ 47970 Hzɼ24510 Hzɼ
7950 Hzɼ3870 Hzɼ2310 Hz ʹઃఆͨ͠ɽ

3. ௐࠪ஍ͷ֓ཁ͓Αͼ࣮‫ํݧ‬๏
3.1 ‫ݱ‬஍֓‫ͱگ‬ௐࠪ஍ͷબఆ

Stevens Water Monitoring Systems, Portland, OR, USAʣΛ༻͍ͯి‫఻ؾ‬ಋ౓ͱ౔৕Թ౓ͷଌఆ΋ߦͬͨɽ౔৕ηϯαʔʹΑΔి‫఻ؾ‬ಋ౓‫ܭ‬ଌͱ౔৕Թ౓‫ܭ‬ଌ͸֤αΠτ಺ͷ 3 ஍఺Ͱߦ͍ɼฏ‫ۉ‬஋Λऔͬͨɽ

3.3 ౔৕୸ૉྔ‫ܭ‬ଌɼಁਫੑࢼ‫ݧ‬·ͨɼ֤αΠτʹ͓͍ͯ 3 ஍఺ͷ 10, 30, 50 cm ͷਂ͔͞Β౔৕࠾औΛߦ͍ɼ࠾औͨ͠౔৕ͷશ୸ૉྔΛ C·N
ίʔμʢMACRO CORDER JM1000CN, δΣΠ · αΠΤϯε · ϥϘ, ‫౎ژ‬ʣΛ༻͍ͯௐ΂ͨɽ‫ݱ‬஍Ͱ͸֤αΠτʹ͓͍ͯ 3 ஍఺͔Β 100 ml ίΞαௐࠪ͸ౡࠜ‫ݝ‬Ӆ‫܊ذ‬Ӆ‫ذ‬ͷౡொʢFig. 2ʣͰߦͬͨɽӅϯϓϥʔΛ࢖ͬͯ౔৕࠾औ΋ߦ͍ɼมਫҐ๏ʹΑͬͯද‫ذ‬ͷౡ͸๺౦෦ʹҐஔ͢ΔӅ‫ذ‬ยຑ‫ͱྨؠ‬੢෦Λ޿͘෴૚౔৕ͷಁਫੑΛௐ΂ɼؒെʹΑΔਫ΍༹࣭ͳͲͷԼํ͏Ӆ‫ذ‬ΞϧΧϦՐࢁ‫ྨؠ‬Λ୅දͱ͠ɼͦͷؒʹ͸৽ୈࡾਁಁ΁ͷӨ‫ڹ‬Λߟ࡯ͨ͠ɽͳ͓ɼಁਫੑࢼ‫ࢼݧ‬ྉΛ࠾औ‫ل‬૚͕޿͘෼෍͓ͯ͠ΓʢখྛΒ, 2002ʣɼ஍൫తʹ੬ऑ

ͨ͠ 2009 ೥͸αΠτ 1 ͱ 0 ʹ౸ୡͰ͖ͳ͔ͬͨͨΊɼͳ৔ॴ͕͍͔ͭ͋͘ΔʢଜాΒ, 1997ʣɽ‫ݝ‬ͷ஍‫׈‬Γ஍ଳಁਫੑʹ͍ͭͯ͸ 1ɼ0 Λআ͍ͯߟ࡯ͨ͠ɽ

ͱͯ͠΋ొ࿥͞Ε͍ͯΔ஍ҬͰ͸ɼ๞࿨ଳͷਫΛൈͨ͘

4. ݁Ռͱߟ࡯

Ίͷࢪઃ͕ຒઃ͞Ε͍ͯͨɽ͜ͷௐࠪ஍͸ 2007 ೥ 8 ݄

31 ೔ʹ‫ه‬࿥తͳ߽Ӎͱͳͬͨ஍ҬͰ͋Δʢ‫ؾ‬৅ி, 2007;଍ཱΒ, 2009ʣɽͦͷࡍʹେ‫ن‬໛ͳ౔࠭ࡂ֐͕ൃੜͨͨ͠
Ίɼౡͷ໘ੵͷ 8 ׂΛ͠ΊΔ৿ྛͷঢ়ଶͱͦͷ౔৕‫ڥ؀‬ʹ͍ͭͯɼ‫ݱ‬৔ௐࠪΛߦ͏͜ͱͱͳͬͨɽ࠷ॳʹ‫ݱ‬৔ௐࠪΛߦͬͨ 2008 ೥ʹ͸·ͩ‫ݱ‬৔Ͱͷ෮‫ߦ͕ۀ࡞چ‬ΘΕ͍ͯͨɽ2009 ೥ʹྲྀҬ಺ͷ৿ྛΛ౿ࠪ͠ɼ৿ྛ؅ཧɼ౔
৕‫ڥ؀‬ɼ஍‫ܗ‬৘ใʹରͯ͠ 15 ఺ͷௐࠪର৅஍Λબఆͨ͠ɽ͍ͭͰ 2009 ೥ 9 ݄ɼ2010 ೥ 8 ݄ʹɼؒെͷ࣮ࢪͷఔ౓ͷҧ͍ͰௐࠪαΠτΛબఆ͠ɼαΠτφϯόʔ 1ɼ

6ɼ7ɼ8ɼ10ɼ11ɼ12ɼ13ɼ0 ͷ 9 ஍఺Λର৅ͱͨ͠౔৕

4.1 ‫ݱ‬஍֓‫گ‬‫ݱ‬஍ௐࠪͱฉ͖औΓʹΑͬͯαΠτ 1ɼ8ɼ12ɼ13ɼ0
͸ 10 ೥Ҏ಺ʹؒെ͕ߦΘΕͨαΠτͰ͋Γɼ6ɼ7ɼ10ɼ

11 ͸ 10 ೥Ҏ্ؒെ͕ߦΘΕ͍ͯͳ͍αΠτͰ͋Δ͜ͱ͕Θ͔ͬͨʢTable 1ʣɽؒെͷҧ͍ʹΑΔ৿ྛͷ֎‫؍‬ͷྫΛ Fig. 3 ʹࣔͨ͠ɽௐࠪαΠτͷ஍఺͕ಛఆ͞ΕΔ͜ͱ͸஍‫ऀݖ‬ͷཧղ͕ಘΒΕͳ͍৔߹͕͋ΔͷͰɼશͯͷ஍఺ʹ͍ͭͯͷҐஔ৘ใ΍ࣸਅ౳ͷ‫ࡌܝ‬͸ׂѪͨ͠ɽؒെͷߦΘΕ͍ͯΔαΠτͰ͸ɼྛচʹे෼ͳޫ͕ಧ

ௐࠪΛߦ͍ɼ೶ྛ஍ͷ؅ཧ͕౔৕‫ʹڥ؀‬༩͑ΔӨ‫ͭʹڹ‬ͨ͘ΊԼ૚২ੜ͕‫͞࡯؍‬ΕΔ͕ɼؒെ஗Ε͕‫ݟ‬ΒΕΔͱ

͍ͯධՁͨ͠ɽ౔৕͸ࡉཻ‫׊‬৭৿ྛ౔Ͱ͋Δɽ·ͨɼथྛচ͕ඇৗʹ҉͘ͳΓɼԼ૚২ੜ͕ශऑͰ͋Δ͜ͱ͕Θछ͸εΪͰ͋Δɽͳ͓ɼαΠτφϯόʔ͕ෆ࿈ଓͰ͋Δ

͔Δɽͳ͓ɼΧϝϥࡱӨͷࡍʹ͸ɼߜΓʹ͍ͭͯࣗಈͰ

͕ɼ৿ྛ؅ཧ͓Αͼ஍‫ܗ‬৘ใͷௐࠪαΠτφϯόʔͱͷͳ͘ϚχϡΞϧઃఆΛߦ͍ɼਓؒͷ໨ࢹʹ͍ۙࣸਅͱͳ

੔߹ੑΛऔΔͨΊɼຊ࿦จ಺Ͱͷ൪߸ͷ෇͚ସ͑͸ͯ͠ΔΑ͏ʹͨ͠ɽ͕ͨͬͯ͠ɼྛচͷ໌Δ͞͸໨ࢹʹ͍͍ۙͳ͍ɽ·ͨɼ‫ݱ‬஍͸ඇৗʹ܏͕ࣼ‫ॴ͍͠ݥ‬΋ଟ͍ͨΊɼࡱӨ݁Ռͱͳ͍ͬͯΔɽ஍‫ऀݖ‬ͷಉҙͷൣғͱ߹Θͤͯɼ߹ཧతʹௐ͕ࠪߦ͑Δ
৔ॴͱͯ͠αΠτΛબఆͨ͠ɽ

3.2 ଟप೾਺ి࣓୳ࠪ๏Λ༻͍ͨి࣓୳ࠪ
प೾਺ి࣓୳ࠪ๏Λ༻͍ͨి‫఻ؾ‬ಋ౓ͷଌఆ͸ɼౡ಺ͷ 9 αΠτʢFig. 2ʣʹ͓͍ͯߦͬͨɽి࣓୳ࠪ‫ʹػ‬͸ GPSʢBR-355, SiRFstar III, GlobalSat, CSR plc., Cam-αΠτ 7ɼ8 ͸ྡ઀͢Δ৿ྛͰ͕͋ͬͨ 7 ͕ඇৗʹ҉
͘ɼ8 ͸ൺֱత໌Δ͘ɼྛচͷ໌Δ͞ʹҧ͍͕͋ͬͨɽαΠτ 10ɼ11 ͸ฉ͖औΓʹΑͬͯલྺ͕೶஍Ͱ͋Δ͜ͱ͕Θ͔͓ͬͯΓɼதͰ΋ 11 ͸ஈʑാঢ়ͷ‫͍ͯͬ࢒͕ܗ‬ͨɽ·ͨɼαΠτ 12ɼ13 ͸ࢁ௖ʹ͍ۙॴͰɼαΠτ 12
Ͱ͸ 3 ࢒ 2 െʢ3 ྻ࢒ͯ͠ɼ2 ྻؒെ͢Δʣͱ͍͏ྻঢ়ؒ

౔৕ͷ෺ཧੑɹୈ 124 ߸ɹ (2013)20

Table 1 ௐࠪαΠτͷ֓‫؍‬.
General characteristics of the survey sites.
ௐࠪαΠτ௚ۙͷؒെ೥*Լ૚২ੜ**

܏ࣼʢ౓ʣ

0
1
6
7
8
10
11
12
13

2008
2009
> 10
> 10
1999
> 10
> 10
2007
2008

Ԣ੝

19
8
18
39
34
21
21
13
18

༗Γ
‫ر‬গ
ແ͠
༗Γ
ແ͠
‫ر‬গ
Ԣ੝
Ԣ੝

฼ࡐ***
ϛάϚλΠτ࣭ยຑ‫ؠ‬᛽ɼటɼ‫ؚ‬᛽ట‫ͼٴ‬Րࢁփ᛽‫ؠ࠭ؠ‬ట‫ޓؠ‬૚҆ࢁ‫ؠ༹ؠ‬҆ࢁ‫ؠ༹ؠ‬᛽ɼటɼ‫ؚ‬᛽ట‫ͼٴ‬Րࢁփ‫ݰ‬෢‫ؠ༹ؠ‬᛽ɼటɼ‫ؚ‬᛽ట‫ͼٴ‬Րࢁփ᛽ɼటɼ‫ؚ‬᛽ట‫ͼٴ‬Րࢁփ∗ : >10 ͸ؒെ೥͸ಛఆग़དྷͳ͍͕ɼ10 ೥Ҏ্ؒെ͞Ε͍ͯͳ͍΋ͷɽ∗∗ : Ԣ੝ > ༗Γ > ‫ر‬গ > ແ͠ɼͷॱʹগͳ͘ͳΔɽ∗∗∗ : ࢁ಺Βʢ2009ʣΑΓെ͕ߦΘΕͨ੻͕‫͞࡯؍‬ΕͨɽαΠτ 12ɼ13ɼ0 ʹ͍ͭͰ޿ൣғͷ༷ࢠΛ୳ࠪͰ͖Δɽैདྷ‫ܕ‬ηϯαʔͰ͸ؕΓͯ͸ɼྛচ͕ඇৗʹ໌Δ͍ͷ͕ಛ௃Ͱ͋ͬͨɽͳ͓ɼα͕ͪͳۭؒมಈΛͱΒ͑Δ͜ͱ͕Ͱ͖ΔͨΊɼ஋ͷ‫ূݕ‬Πτ 1 ʹ͍ͭͯ͸ؒെ༗Γͷଆʹ෼ྨ͞Ε͍ͯΔ͕ɼؒ

ʹ஫ҙ͢Δඞཁ͕͋Δ͕ɼଟ఺‫ܭ‬ଌͱ͍͏఺Ͱ͸ɼΉ͠െ͔Βؒ΋ͳ͍͜ͱΛ෇‫͓ͯ͘͠ه‬ɽ

Ζ༗རͱ൑அ͞Εͨɽ

4.2 ଟप೾਺ి࣓୳ࠪ
ଟप೾਺ి࣓୳ࠪ‫ػ‬Λ༻͍ͯɼ1ɼ6ɼ7ɼ8ɼ10ɼ11ɼ12ɼ

13ɼ0 ͷ 9 αΠτʹ͓͍ͯి‫఻ؾ‬ಋ౓Λଌఆͨ͠ɽ࠷ॳ
ʹɼ5 ͭͷप೾਺Ͱଌఆͨ͠ి‫఻ؾ‬ಋ౓ͷ஋ΛɼฏҪΒ
ʢ2008ʣʹैͬͯɼϥΠϯʹରͯ͠Ԗ௚ʹ࿈ͶͨԖ௚෼෍
ਤΛ࡞੒͠ɼαΠτ 6 ͱ 13 ͷྫΛ Fig. 4 ʹࣔͨ͠ɽਤ
Λ‫ݟ‬ΔͱɼԼ૚ʹൺ΂ͯද૚ͷํ͕ి‫఻ؾ‬ಋ౓͕ߴ͍͜ͱ͕෼͔Δɽ߱Ӎͷ౸ୡɼਁಁ · ৠൃɼམ༿ɼ෼ղͳͲΛߟ͑Ε͹ɼද૚ͷํ͕࠷΋มԽʹ෋Έɼ౔৕‫ڥ؀‬ͷҧ͍͸ද૚ۙ͘ʹಛ௃తʹදΕΔͱղऍͰ͖ΔɽFig. 4 Λؒെͷ͋Δͳ͠ͷҧ͍͔Βൺֱ͢Δͱɼؒെ஗Εͷ‫ݟ‬ΒΕߴ͍͜ͱ͕Θ͔Δɽͦ͜Ͱ஍໘ʹ΋ͬͱ΋͍ۙσʔλͱߟ͑ΒΕͨ 47970 Hz ͷ఻ಋ౓෼෍ʹ͍ͭͯɼैདྷ‫౔ܕ‬৕ηϯαʔͰ஋ͷ‫ূݕ‬Λߦͬͨɽ·ͣɼ47970 Hz Ͱଌఆͨ͠ి‫఻ؾ‬ಋ౓ͷ݁ՌΛαΠτຖʹฏ‫ۉ‬Խ͠ɼԹ౓ิਖ਼
ʢ‫ج‬४Թ౓ 25 ˆʣΛߦ͍ɼͦͷ݁ՌΛैདྷ‫ܕ‬ͷ౔৕ηϯαʔͱൺֱ͠ɼFig. 5 ʹࣔͨ͠ɽͦͷ݁Ռɼ47970 Hz ͷ

Fig. 3 ௐࠪ஍ʹ͓͚Δ౔৕‫ڥ؀‬ͷ֎‫؍‬ɽࠨ:ؒെ͞ΕͨαΠτʢNo. 0ʣɽӈ:ؒെ஗ΕͷαΠτʢNo. 7ʣɽ
Appearance of soil environment. Left: The thinning site (No. 0).
Right: The delayed thinning site (No. 7).
Frequency (Hz)Δํ͕ɼؒെ͕͞ΕͨํΑΓද૚ʹ͓͚Δి‫఻ؾ‬ಋ౓͕㻠

479700
-5
24510
-10
7950
-15
3870
-20
2310
㻟

㻞

㻝

㻜

㻜

प೾਺ʹΑΔి࣓୳ࠪͷి‫఻ؾ‬ಋ౓ͱ౔৕ηϯαʔͷిΒΕͨɽैͬͯ 0.5 ∼ 1 m ͷి‫఻ؾ‬ಋ౓Λ‫ܭ‬ଌ͍ͯ͠Δͱߟ͑ΒΕΔి࣓୳ࠪͷ஋͸ද૚౔৕ͷ‫ܭ‬ଌΛ͢Δ౔৕ηϯαʔͷ஋ʹ͍ۙͱ‫ͤͳݟ‬ΔͱΘ͔ͬͨɽి࣓୳ࠪ͸ඇ઀৮Ͱ͋Δ͕ɼैདྷͷ౔৕ਫ෼ · Ԙ෼ηϯαʔͱۙࣅͨ͠஋Λࣔ͢͜ͱ͔ΒɼຊαΠτʹ͓͍ͯ͸ද૚౔৕‫؀‬‫ڥ‬ͷ‫ܭ‬ଌʹ༻͍ͯࠩ͠ࢧ͑ͳ͍ͱߟ͑ΒΕͨɽͳ͓ɼ͜
Ε͸ฏҪΒʢ2008ʣͱಉ༷ͷ݁ՌͰ͋Δ͕ɼ஍Լߏ଄΍

Frequency (Hz)‫఻ؾ‬ಋ౓ͷؒʹ͸ܾఆ܎਺͕ 0.891 ͱ‫͍ڧ‬ਖ਼ͷ૬͕ؔΈ



60

80

100

120

(m)

6


㻞



㻝

㻜
㻜

㻞

20

40 (m)



ΔՄೳੑ͕͋Γɼ֤αΠτʹ͓͚Δ‫ূݕ‬Λৗʹߦ͏ඞཁ͍͍ͤͥ‫ܭ‬ଌ͕਺఺ʹ‫ݶ‬ΒΕΔ͕ɼి࣓୳ࠪͰ͸ඇ઀৮

40

㻟



ද૚౔৕‫ڥ؀‬ͷௐࠪΛߟ͑ͨͱ͖ɼ౔৕ηϯαʔͰ͸

20

㻠

479700
-5
24510
-10
7950
-15
3870
-20
2310

஍࣭ߏ଄ʹࠨӈ͞ΕΔΑ͏ͳαΠτͰ͸͜ͷؔ܎่͕Ε
͕͋Δɽ

㻞



0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 (mS m-1)

Fig. 4 ؒെͷҧ͍ʹΑΔ‫͚͔ݟ‬ͷి‫఻ؾ‬ಋ౓ͷԖ௚෼෍ͷҧ
͍ɽNo. 13 ؒെ͞Εͨ౔஍ɼNo.6 ؒെ஗Ε͕‫ݟ‬ΒΕΔ౔஍ɽ
Vertical proﬁles of electric conductivity differed by thinning. No.
13 The thinning site, No. 6 The delayed thinning site.

࿦จɿଟप೾਺ి࣓୳ࠪ๏ʹΑΔ৿ྛͷ؅ཧ͕౔৕‫ʹڥ؀‬༩͑ΔӨ‫ڹ‬ධՁ

21

ͷ 6ɼ10ɼ11 ͱൺֱ͢Δͱి‫఻ؾ‬ಋ౓͕ߴ͍ന͍෦෼͕
͋·Γ‫ݟ‬ΒΕͳ͍͜ͱ͕Θ͔ΔɽFig. 6 ͱ 7 ͷൺֱʹΑΓɼؒെͷߦΘΕ͍ͯΔαΠτͷํ͕ɼؒെ͕஗Ε͍ͯΔαΠτΑΓ΋ද૚౔৕ͷి‫఻ؾ‬ಋ౓͕௿͍܏޲͕‫͍ڧ‬͜ͱ͕෼͔ͬͨɽ
͞Βʹɼ‫ࡏݱ‬͸৿ྛͱͯ͠ར༻͞Ε͍ͯΔαΠτͰ΋ɼա‫ʹڈ‬೶஍ͱͯ͠ར༻͞Ε͍ͯͨαΠτ 10ɼ11 Ͱ͸ɼి‫఻ؾ‬ಋ౓͕ߴ͘ͳΔ܏޲͕͋Γɼ10 ͸εέʔϧΛม͑ͳ͚Ε͹ͳΒͳ͍΄Ͳߴ͍఻ಋ౓Λࣔͨ͠ɽա‫ڈ‬ͷࢪංͷӨ‫͕ڹ‬ଓ͘‫͍ͯͭʹؒظ‬͸໌Β͔Ͱͳ͍͕ɼ‫ࡏݱ‬ͷ؅ཧঢ়ଶҎ֎ʹ΋ա‫ڈ‬ͷར༻ཤྺ͕౔৕‫ʹڥ؀‬Ө‫͍ͯ͠ڹ‬Δ
͜ͱ͕ਪଌ͞ΕΔɽͳ͓ɼαΠτ 7 ͸ࣼ໘͕ 39 ౓ͱඇৗʹ‫͋Ͱٸ‬Γɼ౿ࠪͷࡍʹද౔͕΅Ζ΅Ζͱ่Εམͪͯ͘Δ΄Ͳ΋Ζ͍ಛ௃
Fig. 5͕͋ͬͨͨΊɼଞͷαΠτͷΑ͏ͳಛ௃͕දΕʹ͔ͬ͘ి࣓୳ࠪͱ౔৕ηϯαʔͷ‫͚͔ݟ‬ͷి‫఻ؾ‬ಋ౓ͷൺֱɽ

Relationship between electromagnetic sounding EC and soil sensor EC.

ͨՄೳੑ͕͋Δɽ

4.3 ౔৕ͷಁਫੑද૚౔৕ͷ๞࿨ಁਫ܎਺Λ 3 ൓෮Ͱ‫ܭ‬ଌ͠ɼͦͷ஋Λൺֱ͢ΔͱʢFig. 8ʣɼαΠτ 6ɼ8ɼ10ɼ11 ͸ಁਫੑ͕ൺֱత௿͘ɼ7ɼ12ɼ13 ͸ߴΊͰ͋Δ͜ͱ͕Θ͔ͬͨɽ
6ɼ10ɼ11 ʹؒെ஗Ε͕‫ݟ‬ΒΕɼ12ɼ13 ͸ 10 ೥Ҏ಺ʹؒെ͕͞Ε͍ͯΔ͜ͱΛߟ͑Δͱɼઌͷ౔஍؅ཧͷঢ়‫گ‬͸ಁਫੑͷҧ͍ʹ΋දΕ͍ͯΔͱਪ࡯͞Εͨɽͦ͜Ͱؒ

Fig. 6 ؒെͷߦΘΕ͍ͯΔαΠτͷ‫͚͔ݟ‬ͷి‫఻ؾ‬ಋ౓ͷਫฏ෼෍ʢप೾਺ 47973 Hzʣɽ
Horizontal distribution of electrical conductivity data at the thinning sites (Frequency 47970 Hz).

͍࣍Ͱɼ47970 Hz ͷप೾਺͔ΒಘΒΕͨ఻ಋ౓ʹ͍ͭͯɼਫฏ෼෍ਤΛ࡞੒ͨ͠ɽؒെ؅ཧͱؒെ஗Ε΍ɼԼ૚২ੜͷ༗ແʹ͍ͭͯ໌Β͔ͳҧ͍͕͋ͬͨͨΊɼਤͰ
͸ 10 ೥Ҏ಺ʹؒെ͞ΕͨαΠτʢؒെ͋ΓʣʢFig. 6ʣɼ

10 ೥Ҏ಺ʹແؒെͷαΠτʢؒെ஗Εʣ
ʢFig. 7ʣͱ෼͚
ͯදࣔͨ͠ɽ৭͕ബ͍΄Ͳ఻ಋ౓͕ߴ͘ɼ৭͕ೱ͍΄Ͳ఻ಋ౓͸௿͍ਤΛ࡞੒͍ͯ͠Δɽશମతʹి‫఻ؾ‬ಋ౓͕ߴ͍αΠτ͸ 6ɼ10ɼ11 Ͱ͋Γɼి‫఻ؾ‬ಋ౓͕௿͍αΠτ͸ 1ɼ7ɼ8ɼ12ɼ13ɼ0 Ͱ͋ΔɽؒെͷߦΘΕ͍ͯΔ
αΠτʢFig. 6ʣͷதͰ͸ɼαΠτ 12ɼ13 ͸গ͠ి‫఻ؾ‬ಋ౓͕ߴΊͰ͋Δ͕ɼؒെͷ஗Ε͍ͯΔαΠτʢFig. 7ʣ

Fig. 7 ؒെͷ஗Ε͍ͯΔαΠτͷ‫͚͔ݟ‬ͷి‫఻ؾ‬ಋ౓ͷਫฏ෼෍ʢप೾਺ 47973 HzʣɽNo. 10 ͷ EC ͸ผεέʔϧͰදࣔɽ
Horizontal distribution of electrical conductivity data at the delayed thinning sites (Frequency 47970 Hz). EC scale was separately added to No. 10.

22౔৕ͷ෺ཧੑɹୈ 124 ߸ɹ (2013)ͨɽ7ɼ8 Λআ͘ͱؒെ؅ཧ · ؒെ஗ΕʹΑΔ྆ऀͷಁਫੑ͸‫ ཰ݥة‬1 % ͰҟͳΔͱ‫͑ݴ‬Δ͜ͱ͕Θ͔͕ͬͨɼ7ɼ

8 ͷಁਫੑ͸ɼؒെ؅ཧͰখ͘͞ɼؒെ஗ΕͰେ͖͘‫ٯ‬ͷ܏޲Λࣔͨͨ͠ΊɼௐࠪαΠτશମͱͯ͠ಁਫੑ͕༗
ҙʹҟͳΔͱ͸‫͔ͨͬͳ͑ݴ‬ɽ7ɼ8 ͸ྡ઀͢Δ৿ྛͰ͋Δ͕ɼଞͷαΠτʹൺ΂ͯࣼ໘͕ 7 ͸ 39 ౓ɼ8 ͸ 34 ౓ͱඇৗʹ‫͋Ͱٸ‬Γɼલड़ͷΑ͏ʹද౔͕ඇৗʹ΋Ζ͔ͬͨͨΊɼଞͷαΠτͷΑ͏ͳಛ௃͕දΕʹ͔ͬͨ͘Մೳੑ͕͋Δɽ

4.4 ౔৕ͷશ୸ૉྔ
Fig. 9 ʹ֤αΠτͷ 10ɼ30ɼ50 cm ͷਂ͔͞Β࠾औͨ͠౔৕ͷશ୸ૉྔʢTotal Carbon, TCʣΛࣔͨ͠ɽ͍ͣΕͷαΠτʹ͓͍ͯ΋શ୸ૉྔ͸࠷ද૚ͷ 10 cm ͕࠷΋ଟ
Fig. 8 αΠτຖͷฏ‫ۉ‬ಁਫ܎਺ɽ
Average hydraulic conductivity at each site.

͘ɼଓ͍ͯ 30 cmɼ50 cm ͷॱʹগͳ͘ͳ͍ͬͯͨɽ·ͨɼؒെͷߦΘΕ͍ͯΔαΠτ 12ɼ13 Ͱ͸ɼ֤ਂ͞ͱ
΋ʹશ୸ૉྔ͕ଞͷαΠτΑΓ໌Β͔ʹଟ͘ɼਂ͍ॴ·Ͱ༗‫ػ‬෺͕ଘࡏ͢Δ܏޲͕ೝΊΒΕͨɽͨͩ͠ɼ1ɼ8 ͸ؒെ஗Ε͕‫ݟ‬ΒΕΔαΠτͱ͋·Γ༗‫ػ‬෺ྔ͕มΘΒͳ
͍ɽ1 ͸ؒെ͕े෼Ͱͳ͘ɼؒെ‫ޙ‬΋ྛ෼͕աີͰ͋Δ
͜ͱɼ8 ͸ߦΘΕͨؒെͷ࣌‫ ͕ظ‬10 ೥લͰɼ࣍ͷؒെ࣌‫ظ‬Λܴ͍͑ͯΔαΠτͰ͋Δ͜ͱ͕Θ͔͍ͬͯΔʢߴ‫ڮ‬Β, 2012ʣɽ1 ͸ؒെ͔Βؒ΋ͳ͍͜ͱ΋͋Γɼಉؒ͡െ
Ͱ΋ 12ɼ13ɼ0 ͷΑ͏ʹྛচ͕໌Δ͘ͳΔ΄ͲͷؒെΛߦΘͳ͍ͱɼ͓ͦΒͦ͘Εʹͱ΋ͳ͏২ੜͷճ෮ͱɼଓ
͘༗‫ػ‬෺ͷ஝ੵͷཤྺ͕࢒Γʹ͍͘ͱߟ͑ΒΕͨɽଞͷؒെ஗Ε͕‫ݟ‬ΒΕΔͱ͜Ζ͸༗‫ػ‬෺͕গͳ͍܏޲͕‫ݟ‬ΒΕͨɽ߱ӍʹΑΔਫͷҠಈ΍༗‫ػ‬෺·ͨඍࡉ౔৕ཻࢠͷӡൖͷ݁ՌͰ͸ɼࢁ௖ʹ͍ۙॴ΄Ͳ༗‫ػ‬෺૚͸Ԗ௚ํ޲ʹബ

Fig. 9 ਂ͞ຖͷશ୸ૉྔʢTCʣɽ
Vertical proﬁles of total carbon contents.

͘ͳΓ΍͍͢ͱਪఆ͞Ε͕ͨɼαΠτ 12ɼ13 ͷΑ͏ʹࢁ௖ʹ͍ۙαΠτͰ΋Ԗ௚ํ޲΁ͷ༗‫ػ‬෺ͷ஝ੵ͕‫ݟ‬ΒΕɼؒെͳͲͷਓҝతҡ࣋؅ཧͷӨ‫͕݁ڹ‬ՌʹදΕͨͱߟ͑ΒΕͨɽҰํɼؒെͷ஗Ε͍ͯΔαΠτͰ͸ɼԖ௚ํ޲΁ͷ༗‫ػ‬෺ྔͷ஝ੵ͕গͳ͍܏޲͕͋Δ͜ͱ͕෼͔ͬͨʢFig. 9ʣɽલड़ͷΑ͏ʹαΠτ 7ɼ8 ͸ඇৗʹ‫ٸ‬ࣼ໘Ͱ͋ͬͨͨΊɼؒെͷ༗ແʹؔΘΒͣ༗‫ػ‬෺͕஝ੵ͞Εʹ͘͘ͳ͍ͬͯͨ΋ͷͱਪ࡯͞Εͨɽͳ͓ɼ͜͜ͰαΠτຖʹਂ͞ 10ɼ30ɼ50 cm ͔Β࠾औͨ͠౔৕ͷશ୸ૉྔͱͦͷαΠτʹ͓͚Δి࣓୳ࠪͷి‫఻ؾ‬ಋ౓ͷ૬ؔΛ‫ࠪ͠ݕ‬ɼFig. 10 ʹࣔͨ͠ɽਤΑΓ૬ؔ͸ೝΊΒΕͣɼి࣓୳ࠪ͸༗‫ػ‬෺ͷӨ‫ڹ‬Λड͚͍ͯͳ͍
͜ͱ͕෼͔Δɽ

4.5 ද૚౔৕‫ͱڥ؀‬ਫ‫΁ڥ؀‬ͷӨ‫ڹ‬͜͜Ͱઌͷ఻ಋ౓ͷ஋ͷେখʹ͍ͭͯ‫͑ߟͰ఺࣌ݱ‬ΒΕΔ͜ͱΛ੔ཧͯ͠Έͨɽؒെͷ஗Ε͍ͯΔαΠτʢFig. 7ʣͰ͸ɼFig. 3 ʹ΋ࣔͨ͠௨Γྛ಺͕҉͘ɼԼ૚
Fig. 10 ి࣓୳ࠪͷి‫఻ؾ‬ಋ౓ͱ༗‫ػ‬෺ྔͷൺֱɽ
Relationship between electromagnetic sounding EC and total carbon contents.

২ੜ͕͋·Γ‫ݟ‬ΒΕͳ͔ͬͨɽਓ޻ྛ͔Βͷམ༿ʹ͍ͭͯ͸ؒെ؅ཧ · ؒെ஗Ε྆ऀಉ౳ͱߟ͑ɼ༗‫ػ‬෺͕෼ղ͞ΕΔաఔͰੜ͡ΔՄ༹ੑԘྨʹ͍ͭͯߟ͑ΔɽҢ౓‫ܦ‬െ؅ཧ͕ߦΘΕ͍ͯΔαΠτͱؒെ஗Ε͕‫ݟ‬ΒΕΔαΠ

౓͕มΘΒͣɼԹ౓‫͔ͱ͍͕ۙ͜ڥ؀‬Β༗‫ػ‬෺෼ղͷఔ౓͕ಉ͡Ͱ͋ΔͱԾఆ͢Ε͹ɼԼ૚২ੜͷଟ͍ؒെ؅ཧ

τ͸ಁਫੑ͕ҟͳΔͱ͍͏ԾઆΛཱͯͯɼt ‫ݕ‬ఆΛߦ͕ͬߦΘΕ͍ͯΔํ͕ӫཆԘͱͯ͠ͷྔ͸ଟ͘ͳΔ͸ͣͰ࿦จɿଟप೾਺ి࣓୳ࠪ๏ʹΑΔ৿ྛͷ؅ཧ͕౔৕‫ʹڥ؀‬༩͑ΔӨ‫ڹ‬ධՁ

23

͋Δɽ͔͠͠ͳ͕Βɼ࣮ࡍ͸‫ٯ‬ͷ܏޲Ͱ͋ͬͨɽؒെ஗

෼͔ͬͨɽ·ͨɼి࣓୳ࠪͷ࠷ද૚ͷి‫఻ؾ‬ಋ౓ͱ౔৕

Εͷ৿ྛ౔৕Ͱ఻ಋ౓੒෼͕େ͖͘ͳΔ܏޲͕͋Δͱ͢EC ηϯαʔʹΑΔैདྷ๏ͷి‫఻ؾ‬ಋ౓ʹ͸ߴ͍૬͕ؔ

ΔͱͦͷଟՉʹӨ‫ڹ‬Λ‫͍ͯ͠΅ٴ‬Δͷ͸২෺ͷ੒௕ʹΑೝΊΒΕͨͨΊɼද૚ͷ౔৕‫ܭڥ؀‬ଌͷଥ౰ੑ͕֬ೝ͞

ΔӫཆԘͷফඅͱߟ͑Ε͹͜ͷໃ६ʹҰఆͷߟ࡯Λ༩͑Εͨɽୠ͠ɼి‫఻ؾ‬ಋ౓ͷෆ‫ۉ‬ҰੑΛ༩͑Δଞͷཁૉ͕

Δ͜ͱ͕Ͱ͖Δɽ͋Δͱ͖ʹ͸͜ͷ‫ݶ‬ΓͰ͸ͳ͘ɼৗʹ‫ূݕ‬Λߦ͏͜ͱ͕

ࠓճͷௐࠪ஍͸ɼ؅ཧͷૈ์ԽʹΑͬͯ৿ྛʹ͓͚Δ

ඞཁͰ͋Δɽ

ؒെ஗Ε͕‫ݟ‬ΒΕɼԼྲྀҬʹ༩͑ΔӨ‫ݒ͕ڹ‬೦͞Εͨͱ

ʢ2ʣௐࠪ஍ʹ͸ɼؒെͷߦΘΕ͍ͯΔαΠτͱؒെ

͜ΖͰ͋ΔɽҼՌؔ܎ͱͦͷൃੜͷॱং·Ͱ͸‫͖Ͱٴݴ‬ͷ஗Ε͍ͯΔαΠτ͕ଘࡏ͠ɼؒെ͕஗Ε͍ͯΔαΠͳ͍͕ɼ͜Ε·Ͱͷௐࠪ݁ՌΛ૯ཡ͢Δͱɼؒെͷ༗ແɼτͷํ͕ද૚౔৕ͷి‫఻ؾ‬ಋ౓͕ൺֱతߴ͍͜ͱ͕෼

Լ૚২ੜͷൟໜɼԼํਁಁͷଅਐͱ༗‫ػ‬෺ͷ஝ੵ͕Ұఆ͔ͬͨɽͷ܏޲Λ࣋ͬͯൃੜ͍ͯ͠ΔͱਪଌͰ͖Δɽͭ·Γɼؒʢ3ʣશ୸ૉྔͷଌఆ݁Ռ͔Βɼؒെͷ஗Ε͍ͯΔαΠെɼ২ੜͷൟ৩ɼԼํਁಁͷଅਐ͕͋Ε͹ɼՄ༹ੑԘྨ

τͰ͸ɼ༗‫ػ‬෺͕ઙ͍ͱ͜Ζ͚ͩʹ‫͞࡯؍‬Εɼଞํɼؒ

͕౔৕ද૚ʹूੵ͢Δ͜ͱ͸ͳ͘ɼগͳ͘ͱ΋ 50 cm ఔെͷߦΘΕ͍ͯΔαΠτͰ͸ 50 cm ͷਂ͞Ͱ΋ൺֱతଟ౓·Ͱे෼ͳྔͷ༗‫ػ‬෺͕‫͞࡯؍‬ΕΔͱղऍͰ͖Δɽ‫ٯ‬͘ͷ༗‫ػ‬෺͕‫͞࡯؍‬Εͨɽ͜Ε͸Լ૚২ੜͷྔͱਁಁੑ

ʹؒെ஗Εɼශऑͳޫ‫ڥ؀‬ɼශऑͳ২ੜɼͦͯ͠ಁਫੑ

ͷળ͠ѱ͔͠Βઆ໌͕ՄೳͰ͋ͬͨɽ

ෆྑ͕ൃੜ͢Ε͹ɼ༗‫ػ‬෺͕ද૚ʹ͔͠‫͞࡯؍‬ΕͣɼՄؒെͷߦΘΕ͍ͯͳ͍৿ྛͰ͸ɼԼ૚২ੜ͕͋·Γ‫ݟ‬༹ੑԘྨ͕ද૚ʹूੵ͠΍͘͢ͳΔͱղऍͰ͖Δɽ͔͠ΒΕͣɼਓ޻ྛͷམ༿ · མࢬʹͱ΋ͳ͏༗‫ػ‬෺෼ղͷա͠ͳ͕Β܏ࣼͷେ͖ͳࣼ໘Ͱ͸ಁਫੑʹ‫ٯ‬స܏޲͕͋ͬఔͰੜͣΔՄ༹ੑԘྨ͕࢒ଘ͢Δͱਪଌ͢Δͱɼ݁࿦ͷͨΓɼ఻ಋ౓੒෼ͷଟՉʹ͍ͭͯ͸ɼͦͷ‫ݪ‬Ҽʹ͍ͭͯ

ʢ2ʣͰߴ͍ి‫఻ؾ‬ಋ౓͕‫؍‬ଌ͞Εͨ͜ͱʹҰఆͷղऍΛਪఆͷҬΛग़ͳ͍෦෼͕͋Γɼ͞ΒͳΔௐࠪͱ‫͕ূݕ‬ඞ

༩͑Δ͜ͱ͕Ͱ͖ͨɽ

ཁͱߟ͍͑ͯΔɽ

ʢ4ʣ‫ࡏݱ‬͸৿ྛͱͯ͠ར༻͞Ε͍ͯΔαΠτͰ΋ɼաؒെͱԼ૚২ੜʹ͍ͭͯ͸͜Ε·Ͱ΋‫͞ٴݴ‬Ε͖ͯͨ‫ʹڈ‬೶஍ͱͯ͠ར༻͞Ε͍ͯͨ৔ॴͰ͸ɼి‫఻ؾ‬ಋ౓͕͕ɼͦΕ͕౔৕‫͢΅ٴʹڥ؀‬Ө‫ڹ‬Λి࣓୳ࠪʹΑͬͯɼ

ߴ͘ͳΔ܏޲͕͋Γɼ‫ࡏݱ‬ͷ؅ཧҎ֎ʹ΋ա‫ڈ‬ͷར༻ཤԖ௚ϓϩϑΝΠϧ·ͨฏ໘ਤͱͯ͠ಛ௃͚ͮΔ͜ͱ͕Ͱྺ͕౔৕‫ʹڥ؀‬Ө‫͍ͯ͠ڹ‬Δ͜ͱ͕෼͔ͬͨɽ

͖ͨɽ఻ಋ౓੒෼͕Մ༹ੑԘྨͷ஝ੵ͔Β΋ͨΒ͞Εͨʢ5ʣଟप೾਺ి࣓୳ࠪ‫ػ‬Λ༻͍Δ͜ͱʹΑͬͯɼ౔஍

΋ͷͰ͋Ε͹ɼԼྲྀଆ΁ͷա৒‫څڙ‬Λ๷͙໨త͔Βɼؒ؅ཧ΍ར༻ཤྺΛి‫఻ؾ‬ಋ౓ͷҧ͍ͱͯ͠໘తʹධՁ͢െͱͦΕʹଓ͘Լํ২ੜͷൟໜ͕͓ͦΒ͘ޮՌతͳରॲ

ΔՄೳੑΛࣔ͢͜ͱ͕Ͱ͖ͨɽి࣓୳ࠪ͸ඇ઀৮Ͱ୹࣌

๏Ͱ͋ΔͱਪଌͰ͖Δ͠ɼಁਫੑͷվળͱ༗‫ػ‬෺ྔͷ஝ؒʹ޿ൣғͷ౔৕ௐ͕ࠪՄೳͰ͋Γɼৄࡉௐࠪͷલͷεੵ͔Β΋ؒെͷޮՌ͸େ͖͍ͱਪଌ͞ΕͨɽΫϦʔχϯάʹ໾ཱͭͱߟ͑ΒΕͨɽैདྷ‫౔ܕ‬৕ηϯαʔͱ૬ؔͷ͋Δσʔλ͕ಘΒΕͨ͜ँࣙͱ͔Βɼి࣓୳ࠪ͸ௐࠪख๏ͱͯ͠͸ଥ౰Ͱ͋Δͱ൑அͨ͠ɽ‫ैʹٯ‬དྷ‫౔ܕ‬৕ηϯαʔ͸஍໘ʹϓϩʔϒΛૠೖ͢Δ࿑ྗɼͦΕΛ‫܁‬Γฦ͠ߦ͏͕࣌ؒඞཁͰ͋Δ͜ͱ͔
Βɼి࣓୳ࠪͷํ͕ޮՌతͳௐ͕ࠪߦ͑Δͱ൑அͨ͠ɽ
ͳ͓ɼࠓճ͸౔৕ද૚ʹ౔஍ར༻ͷಛ௃͕‫ݟ‬ΒΕͨ͜ͱ͔Β஍ද༻ͷैདྷ‫ܕ‬ηϯαʔͰͦͷଥ౰ੑ͕ධՁͰ͖ɼ
ޮՌతͳௐ͕ࠪߦ͕͑ͨɼ͜ΕΑΓਂ͍෦Ґͷߟ࡯͕ඞཁͳ৔߹ʹ͸ɼి࣓୳ࠪͷσʔλʹ͍ͭͯಉ༷ͳ‫͕ূݕ‬
ඞཁͰ͋Δ͜ͱΛ෇‫͓ͯ͘͠ه‬ɽՃ͑ͯɼి࣓୳ࠪ͸஍໘ʹඇ઀৮Ͱਝ଎ʹௐ͕ࠪͰ͖ɼ

‫ݱ‬஍ͷௐࠪͰ͸ɼౡࠜ‫౔ݝ‬஍վྑ࿈߹ͷલ઒ࢯͷҊ಺ͷ΋ͱɼӅ‫ذ‬ͷౡͷํʑʹଟେͳ‫ͱྗڠ‬ཧղΛࣀΓɼ͜Εʹਂ͘‫͢ँײ‬Δɽ·ͨɼௐࠪʹ‫ͯ͘͠ྗڠ‬Εֶͨੜͨͪʹ΋‫͢ँײ‬Δɽͳ͓ɼຊ‫ڀݚ‬ͷҰ෦͸ɼ೔ຊֶज़ৼ‫ڵ‬ձʮ࠷ઌ୺ · ࣍ੈ୅‫ڀݚ‬։ൃࢧԉϓϩάϥϜʯɼౡࠜ‫౔ݝ‬஍վྑࣄ‫ஂۀ‬ମ࿈߹ձ‫ڞ‬ಉ‫ڀݚ‬අɼౡࠜେֶॏ఺‫ڀݚ‬ϓϩδΣΫτͷิॿΛड͚ͯߦΘΕͨɽซͤͯ‫͢ँײ‬Δ࣍ୈͰ͋ΔɽҾ༻จ‫ݙ‬

·ͨɼ౔஍ͷ᎟ཚ͕࠷খ‫͋Ͱݶ‬ΔͨΊɼ஍‫ऀݖ‬ͷཧղΛಘͳ͕Βௐ͕ࠪՄೳͰ͋ͬͨɽ೶ྛ஍ͷௐࠪͰ͸ɼӦྛɼӦ೶ऀͷརӹΛଛͳΘͳ͍Α͏ʹɼཱ޵Λ۷Δલʹௐࠪର৅஍Λߜ͓ͬͯ͘͜ͱ͕ॏཁͰ͋Δɽ౔஍ͷ᎟ཚΛͱ΋ͳ͏ৄࡉௐࠪͷલͷεΫϦʔχϯάͱͯ͠ి࣓୳ࠪ͸େ͖ͳޮՌΛൃ‫͢ش‬Δͱߟ͑ΒΕͨɽ

5. ݁࿦ຊ࿦จͰಘΒΕͨ݁ՌΛ੔ཧ͢ΔͱɼҎԼͷΑ͏ʹͳͬͨɽʢ1ʣి࣓୳ࠪͷ݁ՌΛԖ௚ϓϩϑΝΠϧͰදࣔ͢Δ
ͱɼ౔৕‫ڥ؀‬ͷҧ͍͸ද૚ۙ͘ʹಛ௃తʹ‫ݱ‬ΕΔ͜ͱ͕

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ཁࢫ೶ྛ஍͸ྲྀҬ໘ੵͷதͰେ͖ͳׂ߹Λ઎Ίɼ޿େͳ౔৕‫ڥ؀‬ΛޮՌతʹௐࠪͰ͖Ε͹ͦͷޮՌ͸ඇৗʹେ͖͍ɽຊ‫Ͱڀݚ‬͸ɼଟप೾਺ి࣓୳ࠪ‫ػ‬Λ༻͍ͯ౔৕ͷి‫఻ؾ‬ಋ౓Λଌఆ͠ɼ৿ྛͷ؅ཧ͕౔৕‫ڥ؀‬ʹ༩͑ΔӨ‫ڹ‬Λௐ΂ͨɽి࣓୳ࠪͷ݁ՌΛԖ௚ϓϩϑΝΠϧͰදࣔ͢Δͱɼ౔৕‫ڥ؀‬ͷҧ͍͸ද૚ۙ͘ʹಛ௃తʹ‫ݱ‬Ε͓ͯΓɼؒെ͕஗Ε͍ͯΔ৿ྛͰ͸ද૚౔৕ͷి‫఻ؾ‬ಋ౓͕ߴ͘ͳΔ݁Ռ͕ಘΒΕͨɽಉαΠτͰ͸౔৕ͷಁਫੑ͕௿͍܏޲͕͋Γɼ༗‫ػ‬෺΋ઙ෦ͷΈʹ‫ݟ‬ΒΕΔ͜ͱ͔Βɼਁಁੑͷѱ͕͞ද૚΁ͷ෺࣭ͷूதΛଅ͍ͯ͠Δͱਪଌ͞Εͨɽ·ͨ೶஍ͱͯ͠ͷཤྺͷ͋Δ৿ྛͰ͸ɼද૚౔৕ͷి‫఻ؾ‬ಋ౓͕ߴ͘ͳΔ܏޲͕͋Γɼա‫ڈ‬ͷར༻ཤྺ͕౔৕‫ʹڥ؀‬Ө‫͍ͨͯ͠ڹ‬ɽଟप೾਺ి࣓୳ࠪ๏͸ඇ઀৮Ͱ୹࣌ؒʹ޿ൣғͷ౔৕ௐ͕ࠪՄೳͰ͋ΓɼৄࡉௐࠪͷલͷεΫϦʔχϯάʹ໾ཱͭͱߟ͑ΒΕͨɽΩʔϫʔυɿి࣓୳ࠪɼి‫఻ؾ‬ಋ౓ɼԼํਁಁɼ౔৕‫ڥ؀‬