Interception of rainfall by the crown of a fruit-tree-香川大学学術情報リポジトリ

20フ Volフ，Nd2（1956）

1NTERCEPTiON OF RA‡NFALI，

BY、THE CROWN OF A FRU王■T−TREE

Hachiro KIRA（LaboIatOry Of AgIicult11ralEngineeIing） （Received OctoberユD，1955”Accepted October26，ユ955h）

The authoris golng tO descIibe the outline of hisIeSearChes，パTo what extent hasthecrownofafruit・ tree the capadity ofinterception storageincaseof rainandthee董fect onthe soilconse王Vation？＝・With

thisobjectinview，heinvestigated conceIning the crown of an apple・tIee at HiIOSakiCollege，AomoriP工e fecture，fromMaytoNovember，1953，叩dof a，peaCh−tree，a g工aPe−tree，a pine−treeetC“，atKagawaAgri・ culturalCollege，KagawaPrefectuIe，from August to・November，1954

工ntheres？arChestheauthorputthenetinterceptionstorage（0＝eSidualinterception storage）andthe evaporationloss under receptionin the category of theinterceptionstoIage（Ortheinterceptionbythecrow王1 0fa tree）；and putthe totalof theinterception stoIage and the trunk nowinthe available rain董allinteI ceptionHealso definedthe amount which diIeCtly drop＄On the ground under the crowno董the tIee but Of the transitoryinterception storage as the dropplng q11antity on the ground

The autho工prOCeeded on his observation andinvestigation under岳uch classiacation and the resultis

summarized as follows：

（l）Whenthe釦stdropsofrainin any storm strike theleaveiofthecIOWnOf afmit−tree，they are almost completelyIetained as droplets or as a thin alm over the surface o董theleaves・Only a small

poItionoftheIainreachesapoint onthe ground befo貰eal1theleaves overheadhaveretainedtheirmaximum amountof stoIedwater：Prob啓blyacqnsideIableportionof the water which spatters e畠rthwaIds as the drops disintegrates upo平impactandis evapor・atedbeforeitreachesthegI・Oundbecauseofthe extr・emely

smal1size of the resulting particles，When aleaf has acquiredits maximuminterception storage，Water

added overit ca11SeS drops from thelower edgeIn the absence ofwind，eaCh of these dIOPS gIOWSin

size，and when gravity oveIbalances surface・tenSion forces，the drops fal1to theground oェ to alowe工1eaf （Fig√√ユ）”Usually，h。WeVer，drops。rejarredfreefromtheleafbywindoIbyimpact、Ofrさinbeforethe

gravitationalforce exceeds surface tension

Fig，1Balanc寧SOfraindropsontheresultant Afterthecrownsoffruit■・treeSareCOmplete王ysatur■ated， Slopelof foliage thenetinterceptionwouldbezero，WeIeit not董0王theiact

thatevendur・ingrainthereisconsiderable evaporationfrom the enormous wet surface of the foliage

Thus，afterinterception storage has been負11ed，the amount of wateI■reaChing the soilsuIface阜S equalto the rainfall excepting the evaporation from the crown of a fruit・・tree小Atthecessationofrain，the crownofa fruit−tree StillretainstheinterceptionstoIage．，Thiswateriseventua11y returned dir’eCtly to the atmosphere thzIOugh evapoIation

（2）The relations among theleaf−area Of an appie tree（A），the maxjmum netinterception storagebyleaves （Si）and the size of water drops fal1ing fromleaves （D），Which heinvestigatedin hislaboratory concerning the physicalaspects of theinteIICeption of rainfa軋 are expressed by the followlng r’egresSiorlline equations re弓 pectively； pVgsin￠ニ27Tγ■T（1ヰCOS〝）

V：VOlume of raindrops

弓￠：inclinationanglefoliageofsurface rr：Semi・diameterofraindrops lⅣheIe β：COntaCt angle

p：PPeCi負c gravity of raindrops

209 Tech，BulllKagawa AgrCo11 CoI王・elation coe魚cieIlt r＝二0．957榊★ 工ニ09フ4冊書 r＝＝ト0．840ヰ鶉 Empirical foImula Si＝−0．083ヰ・0」019A Siニ＝−0．04ユ十0．017A D＝2．．5−0‖∝氾A n a h ia k裏 山Ral

Ja

1昔 16 15 1隻 13 1，2 11 AveIageleaf・area：39．4cmf！ Averagemaxnetinterceptionstorage‥01667g Average max”netinterception stoIage

pertlnitleaf・area：0・O16g／Cm望 ︵空亡二資儀︻ぶ払20︸￠ぎ竜8ぷヨ︸苫・誓言

0

ト

ヾい・ 1 ♂． ♪ ∩、 9 r O

￣モ斉／′

8 7 6 5 J 3 0 0 0 0 0 0

／二＝

二 ∴享＝ 00／00

。1＿＿＿と二

0 10 A ・． ／二 ． カ 30 40 50 60 70 80 鋤 Leaf−areain（Cm2） ぜ 敷浪紘など′即発磯野奄攣翫 Fig2 Relationbetweenleaf，aI■e，aandmax”三netintercepti？nStOrage芸byleaves（India） 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3

11・1 11 1L l O〇 O q O〇q

︵如︶∽ぎ票−倉亀巴○︶∽已○忠心Uトβ霊︸賀・誓苫 0 10 20 30 40 50 60 baf−aI■ea（Cm2） 70 桝） gO Fig3 Pelationbctween】eaf”areaandmaxnCtinterceptionstoragebYユeaves（Ra11s）

Vd．7，No小2（ユ956）

血e

A：∴1e旛・ateA，Cm2

Si：’maXimum net、inteI〇eption storag畠byleaves，g． D：・Semi・diameter of water’drops′fa11ing fromleaves，mm． 鶉≠‥ Signi負cant at thelevelP＝01rOl， ★舶＝ p＝0（刀l

A verydominantlinearcozTelation exists among themin which thelarger becomes（A），the：∴laz・gef grown（Si），butonthecontrary（D）＜become small畠rby2l∼2．5mminradius（Fig。2，Fig．3）。

（3）Asforr．aindrop岳inandoutofthecrownofan apple”tree，Smaller rainこdrbps，andlarger ones OCCurredmorefrequently、てheraindrops within the tree crown were aboutl・5∼2O times aslarge as thenaturalonesinthemeandiameterofraindrops（Fig。4，Fig，S） July7，1953 Rainfal1intensity：0．6mm／hr 1い〓‖り

・．．

故∴のむ叫呂賀b巴h NaturalIain・drops （median of、semi・diameter：05Smrri） ／ ← l ／ （median of semi−diameter：10フmm） ノ′‡・⊥し l l UlO2u3り4し〉506t）7080910＝121314ヱ51617J8・・川2り212223242526 ＝・ Semi・diameter of rain・drops，mm FiglS Frequencycurveforrain・dropsinandoutofthecrownofanapple−tree（Janathan）

TecbBuilL．XagAwaAgr‖．Cbll 21c）

（4）Astheinterceptionduetothecrownoiafruit−tree WaSlquitedi鮎rentby theinfluence of such factors as rainfall，rainfal1intensity，CQntinuityofrainfal1，densit≠、Of atree−CrOWn，Windvelocity，humidity， etc，the author found that there existed a′pOSitive、COrrelation of a greater、dominanceamong suchitems as rainfall（P），dropping amount on匝eどr■Ound（Pg）and available」rainfal1二interception（Pi），Which are ex・ pr牟SSedわy，thefollowlng regエeSSionline equation：

CoIlelatlOn COe侃clent I＝0836半片チ Ⅰ±0846糊簿 EmplricalfoImula AppleこtIee Pg芯一MO6フ9十0824P Pト＝ 0．フ24−卜0169P Peach・tfee 壬）iこ＝ 0プ55十0．164ンP Grape−tree Pi＝＝lh212＋0147P

Pine−tIee Pi＝ 1468十Oh240P

工￡0．フ69チ袷管

Ⅰニ0けフフ○キ嬉婦

Ⅰ＝0，9ユ4桐ヰ

P：rainね11，mm

Where［Pg：droppmg amount on the gIOund，mm 、Pi：aVailable rainfal1inteICeption，mm

Andit wasacknowledgedthat（Pg）aswellas（Pi）hadatendencytoinc】・eaSe，aCCOrdingaS（P）increased

（5）Tnthe crownof an apple・tlee，adeciduous tree，a mOnthly changeis申Cknowledgedconceming the interceptionofrainfa11duetoitss讐S9nalg亨PWthduringitsieaf・COVerlng Peri6d General1y叩eaking the monthlymeanavailableinterceptioncoe魚cient（Ri）changedinth云shapeofth占normaldi；tribhtion curve type during seven months董rom May，Which are theleムf・・grOhTlng・peIiod

︵2∈︶ 釦．轡血川 コd召還J hヨ苫○苫 血 皿 80 60 亜 00 5 6 7 8 9 Months（1取3） 10 11

Fig6 Montllly meallaVailableinte：CCption by apple・tree（Janathan）in per・CenじOf rain falling in the QPen during fIOm May to Novembe：■，1953

VDIJフ，ノNo2（1956） 2．11 The∴竺ゝ滋i血印加伽seseven㌧叩Onths†aS Showhin、August∴（Ri）during’the aboveperiodieaChed

such percentages as40∼フ0‖（t wasinterpreted that the densityVariationrof tIletree・ICrOWn・piayed’aninl

portantpartin bringing about the above phenomena；the density variation was caused bys11Chnaturaland

arti丘cialfactors as spIeading，grOWth and defoliation o董1eaves formlng thecrowns offIuit・・tIeeS；and paper bags，grOWthoffruits，thhnng，

（6）Theauthorobtain由the加1よi∂n扇品eh＼rainfall（P）and，avdilable・rainfallinterceptioncoemcient

（Ri＝芋×100） iIlthe crown of an apple・・tree by regardingit as a regre＄Sionlin．e and curve from which a

Very dominant secondary correlation was found a′s a reSult of analysing varianceAnd a moreIeliable theoreticalvalueis shown by the followlng regreSSion curVe equation whichis piotted as aparaboliccurve OftheノSO・Cal1もdinveItedJ・・typ？

Ri去アブ由レ薄051P＋・00フ9f，皇

王町this七as畠thed輌l昏・C6r‡elationcoefncientwi11beexpIeSSedby（R）＝＝＝Ⅶ−0：フ505醐inwhichthein王iuences dge to軸Chfact6rs∴；as工二ainf批rainfal1rintensity；continuity of rainfall／density of左crown，wind velocity， etC・；¶瑚l嫉included：Lltlmay be sdidin the simple coITelationbetweentheIainfallandinterceptionthat

the available rainfallintelCePtion due to the crowns of apple・treeS duringtheirleafcoveringperiod料illhave aninclination of gradualdecrease by the secondaryIelation，aCCOrding as rainfa11increasesin caselight I■ains continuelor噌eI（Figフ）

竣工青菜蛮ぢじ宍−盲器Jβu二l司†已竃レむtq遥吋A可

Fig・フ Relation betweenrainfal1andavailable rainfallintercei）tion by apple−tree（Janathan） in percent of rain fal1ingin the open

（7）Tliemeanavailablerainfal1interceptioncoe侃cient（Ri）wasaSfollowsinthesecascs：

（Riり mean） （Ri。meanS）

Apple・tree 56l3％ Grape−tree 33．1％

Peach・tree 322％ Pine・tree 53”9％

（8）There occurr■ed a variation duetotheseasonalgrowingphase for the rainfailintcI・Ception storage CapaCity ofthe crowns of fmit・・tleeS，and the average capacity of which was generally estimated at over O、8mm（apple−t工ee，peaCh−tree），l12mm（g工ape−tIee），l5mm（pine・tree）results outlined aboveThey

Tech．B山L払gawaA宮f・．ゝeOil． 212

weIeObtaiend封omthe small＄ample chiefly based onawedklainfal1durlngaShoItperiod，andwould not be applicableto cases of strong zalnialls

果樹冠に よ る 降雨遮断 護 良 八 郎 果鰍詞の土壌保全に関する研究の一山郎として 栄樹冠がいなかる程度に降雨を速断保留し土壌保金効果を示すも ものであるかについて，1953勾5月∼11月にかけ背森県弘前大学において朽イた林檎樹冠，およぴ1954年8月∼11 月にかけ香川県香川由利大学において行った桃，葡萄および松樹冠筆による降雨速断調査結果の概要をま−とめたも のである この場令開墾後果樹冠による降雨遮断効果は，木懇森林に劣らざるものが認められるが，将来傾斜地果 樹猷おける土盛保全対策のカ全を期すためには，所謂限界伎蝕期において，果樹冠外裸地も敷革被襟作物等地被 物による徹底したCOVeIが望まれる