Estimating fine-root production by tree species and understorey functional groups in two contrasting peatland forests

REGULAR ARTICLE Es ima ing ine- oo p oduc ion by ee species and unde s o ey unc ional g oups in wo con as ing pea land o es s Rabbil Bhuiyan &Ka i Minkkinen & Heljä-Sisko Helmisaa i &Paa o Ojanen & Timo Pen ilä &Raija Laiho Recei ed: 20 June 2016 /Accep ed: 22 Sep embe 2016 #The Au ho (s) 2016. This a icle is published wi h open access a Sp inge link.com Abs ac Backg ound and aims Es ima ion o oo -media ed ca bon luxes in o es ed pea lands is needed o unde s anding ecosys em unc ioning and suppo ing g eenhouse gas in en o ies. He e, we aim o de e mine he op imal me hodology o u ilizing ing ow h co es in es ima ing annual ine- oo p oduc ion (FRP) and i s e ical dis ibu ion in ees, sh ubs and he bs. Me hods We used 3-yea da a ob ained wi h modi ied ing ow h co e me hod and es ed wo calcula ion me hods: ‘ing ow h-di iding’and ‘ing ow h- sub ac ing’. Resul s The ing ow h-di iding me hod combined wi h a 2-yea incuba ion o ing ow h co es can be used o he ‘bes es ima e’o FRP. The FRP in he nu ien - ich en o es (561 g m −2 ) was mo e han wice ha in he nu ien -poo bog o es (244 g m −2 ). Mos FRP oc- cu ed in he op 20-cm laye (76–82 %). T ee FRP accoun ed o 71 % o o al FRP in he bog and 94 % in he en o es s, espec i ely, ollowing he abo e- g ound ege a ion pa e ns; howe e , in en o es he p opo ions o sp uce and bi ch in FRP we e highe han hei p opo ions in s and basal a ea. Conclusions Ou me hodology may be used o s udy pea land FRP pa e ns mo e widely and will educe he olume o labou -in ensi e wo k, bu will bene i om e i ica ion wi h o he me hods, as is he case in all in si u FRP s udies. Keywo ds Fine oo s .Fine- oo p oduc ion me hods . Ing ow hco e .Ing ow hco eincuba ion ime .Pea lands In oduc ion Fine oo s a e inhe en ly impo an belowg ound com- ponen s and media e signi ican ca bon (C) luxes in many ecosys em ypes. Globally, ine- oo p oduc ion (FRP) accoun s o up o 76 % o he C cycled annually h ough o es ecosys ems (Vog e al. 1996; Gowe e al. 1996; Jackson e al. 1997). In bo eal o es s, on a e age FRP accoun s o 73 % o he o al oo p oduc ion and 32 % o he o al o es p oduc ion (Ma schne and Rengel 2007). Fine oo s also media e C accumula ion as pea in many ypes o pea lands (Sjö s 1991;Saa inen 1996; Laiho e al. 2003). Gene ally, howe e , we know li le o ine- oo -media ed C luxes in pea lands, he C ho spo s o he plane , e en hough he e is indica ion ha hey may play a signi ican ole in he C budge (e.g. Mu phy and Moo e 2010), also ollowing land-use change (Finé and Laine 1998; Ojanen e al. 2014). Accu a e es ima ion o C luxes in pea lands unde land use, e.g. o es y, is especially needed o de eloping Plan Soil DOI 10.1007/s11104-016-3070-3 Responsible Edi o : Alexia S okes . Elec onic supplemen a y ma e ial The online e sion o his a icle (doi:10.1007/s11104-016-3070-3) con ains supplemen a y ma e ial, which is a ailable o au ho ized use s. R. Bhuiyan (*):K. Minkkinen :H.<S. Helmisaa i Depa men o Fo es Sciences, Uni e si y o Helsinki, P.O. Box 27, 00014 Helsinki, Finland e-mail: abbil.bhuiyan@helsinki. i P. Ojanen :T. Pen ilä :R. Laiho Na u al Resou ces Ins i u e Finland, 01370 Van aa, Finland eliable C budge s o suppo g eenhouse gas in en o ies (Ojanen e al. 2014). Es ima es o FRP a e especially needed o his pu pose. The FRP a e is dependen on se e al ac o s, such as plan species, oo biomass, mean annual soil empe a u e and annual p ecipi a ion (e.g. e iew by Yuan and Chen 2010 and Finé e al. 2011). The soil nu ien egime also in luences bo h ine- oo biomass (FRB) and FRP; how- e e , he di ec ions o he esponses ha e a ied among s udies in di e en ecosys ems (San an onio e al. 1977; Keyes and G ie 1981; Leibundgu 1981; Hend icks e al. 2006), and he measu es o soil nu ien s epo ed in indi idual s udies ha e no allowed o a sys ema ic syn hesis (Finé e al. 2011). Ye , in he Bo eal Zone, mos esul s sugges highe FRB o FRP a poo e si es (Helmisaa i e al. 2007; Yuan and Chen 2010; Leh onen e al. 2016). Fo pea lands, he sca ce obse a ions so a a ailable sugges a con as ing pa e n (Finé and Laine 1998,2000; Laiho e al. 2014). The nu ien egime o pea soils undamen ally di e s om ha o mine al soils: pea soils con ain clea ly mo e ni ogen (N) bu ewe mine al nu ien s (e.g, Table 6in Wes man and Laiho 2003). Thus, especially a he mos N- ich si es, he a ailabili y o N should be a ou able bu high FRP may be needed o sca enge mine al nu ien s. In addi ion o he nu ien egime, he mois u e and oxygen (O) con- en s as well as he physical p ope ies o pea gene ally di e om hose in mine al soil. Consequen ly, pa e ns o FRP di e ing om hose in mine al soils may be expec ed as well. I espec i e o he s udied ecosys ems, mos o he FRP da a a e conce ned wi h o al ine oo s wi hou dis inguishing be ween he unde s o ey ege a ion oo s and oo s o di e en ee species (Finé e al. 2011). This is mainly due o di icul ies in iden i ying ine oo s by species o unc ional g oups om soil samples: i is a duous and ime-consuming. Ye , he FRB o he unde s o ey ege a ion accoun s o one hi d o he o al FRB in bo eal o es s (Finé e al. 2011). In no he n Finland, unde s o ey ine oo s and hizomes (< 2 mm diame e ) accoun ed o up o 50 % o he s and o al FRB (Helmisaa i e al. 2007). In bo eal pea land o es s o a ying nu ien s a us, he FRP o ield-laye ege- a ion a ied om 24 % o 71 % o he o al FRP (Finé and Laine 1998). Rega ding he a ious species o unc- ional g oups, some s udies ha e been done in bo eal o es s. Fo example, a bo eal mine al soil si es Helmisaa i e al. (2007) s udied he FRB o all majo ee species (pine, sp uce, bi ch) and unde s o ey unc ional g oups (sh ubs, g asses and he bs) in ela ion o si e and s and cha ac e is ics. Kalliokoski e al. (2010) epo ed he belowg ound in e ac ions in mixed bo eal s ands o sil e bi ch Be ula pendula Ro h, No way sp uce Picea abies (L.) H. Ka s . and Sco s pine Pinus syl es is L. a di e en de elopmen al s ages and soil e ili ies in Finland. In bo eal pea lands, di e en coexis ing species may ha e a ying oo ing pa e ns and oo ing dep hs (Me sä ainio 1931;Ruseckas2000). To ou knowledge, such in e ac ions among he FRPs o species in pea lands a con as ing si es a e s ill unexplo ed. Se e al me hods a e a ailable o de e mining FRP, and no me hod is ideal o all si es o s udy pu poses (Vog e al. 1998; Milchunas 2009). Ing ow h co es a e oo - ee soil columns o de ined olume, su ounded by a mesh, allowing oo s o g ow in o hem o e a pe iod o ime (e.g. Vog and Pe sson 1991; Makkonen and Helmisaa i 1999; Os onen e al. 2005; B unne e al. 2013). Recen ly, we designed a modi ied ing ow h co e me hod o es ima ing he FRP in pea soils and p esen ed he i s -yea esul s o di e en si es (Laiho e al. 2014). Howe e , i s -yea ing ow h da a mainly cap u e he p oduc ion o new oo s o colonizing he co es and hus e lec he egene a i e po en ial o he oo sys em a he han he ac ual annual oo p oduc ion, especially in cold clima es wi h p ominen annual g ow h cycles (Cudlín and Chmelíko á 1999; Finé and Laine 2000). O he componen s o he p oduc ion o pe ennial oo sys ems, such as b anching and adial g ow h, eme ge only a e coloniza ion. He e, we p esen 3-yea da a ob ained wi h he modi ied ing ow h co e me hod aiming o 1) compa e ways o calcula ing he FRP om mul i-yea ing ow h biomass da a, 2) de e mine he op imal incuba ion ime o he ing ow h co es in pea land o es s when es ima - ing he annual FRP, 3) es ima e he annual FRP and 4) de e mine he e ical dis ibu ion o FRP o di e en ee species (Sco s pine, No way sp uce and downy bi ch Be ula pubescnes Eh h.), sh ubs and he bs in wo con- as ing pea land o es s: nu ien - ich en o es and nu ien -poo bog o es . We hypo hesized ha 1) nu ien - ich o es s would show highe FRP, due o he g ea e species ichness, highe abo e-g ound biomass and N:mine al-nu ien a ios han in nu ien -poo o es s. Based on p e ious s udies o oo sys ems (Me sä ainio 1931;Ruseckas 2000) we also expec ed ha 2) he FRP o a ious species and unc ional g oups would show di e en dep h dis ibu ions. Plan Soil Ma e ials and me hods S udy si es The s udy was ca ied ou a wo ypical o es y-d ained pea land o es si es o a ying nu ien s a us in sou h- e n Finland. The Kale ansuo si e (60°39’N, 24°22’E) in Loppi ep esen ed nu ien -poo condi ions, while Le osuo (60°39’N, 23°57’E) in Tammela was ep esen- a i e o mo e nu ien - ich condi ions. Kale ansuo was d ained in 1971 and Le osuo in 1969 and bo h si es we e also e ilized wi h a phospho us-po assium (PK) e ilize soon a e d ainage. A he Kale ansuo si e, he ecosys em CO 2 balance has been es ima ed wi h he eddy co a iance me hod (Lohila e al. 2011), and simila measu emen s ha e been ca ied ou a Le osuo since 2009. Mo eo e , se e al componen s o he C cycle ha e also been quan i ied in Kale ansuo (Bado ek e al. 2011;Ojanene al.2013) as well as in Le osuo (Koskinen e al. 2014). The nu ien -poo si e was o iginally an omb o ophic bog cha ac e ized by dwa -sh ubs and Sco s pine and classi ied as a dwa -sh ub pine bog (Laine and Vasande 1996). The bog was d ained wi h open di ches abou 1 m deep and a app oxima ely 40-m in e als. Hence o wa d, we shall call i a ‘d ained bog o es ’. A he ime o his s udy, he si e suppo ed a ee s and domina ed by Sco s pine wi h a sca e ed unde s o ey o downy bi ch and No way sp uce (Lohila e al. 2011). The unde s o ey mainly consis ed o o es and mi e dwa sh ubs (bilbe y Vaccinium my illus L.,cowbe y V. i is-idaea L.,bog bilbe y V. uliginosum L.,Lab ado - ea Ledum palus e L.), mixed wi h some ha e’s ailco ong ass(E iopho um agina um L.) and cloudbe y (Rubus chamaemo us L.). The bo om laye was domina ed by o es and bog- mosses such as ed-s emmed ea he -moss Pleu ozium sch ebe i (B id) Mi ., ugose o k-moss Dic anum polyse um Sw., ine bog-moss Sphagnum angus i olium (C.E.O. Jensen ex Russow) C.E.O. Jensen and Russow’sbog-mossS. ussowii Wa ns . The nu ien - ich si e, Le osuo, is loca ed abou 22 km wes o he nu ien -poo si e, Kale ansuo. The si e was o iginally a meso ophic en classi ied as an he b- ich all sedge bi ch-pine en (Laine and Vasande 1996), and we shall call i a ‘d ained en o es ’. The en si e was also d ained wi h open di ches o abou 40-m spacing. The s and mainly consis ed o Sco s pine wi h some co-dominan downy bi ch and No way sp uce ha o med a igo ous unde s o ey. The unde s o ey was mo e di e se bu less dense han in Kale ansuo. In addi ion o species ound in Kale ansuo, se e al he bs g ew in Le osuo, such as na ow buckle - e n D yop e is ca husiana (Vill.) H.P. Fuchs and chickweed-win e g een T ien alis eu opaea L. The de- ails o bo h s udy si es in e ms o soil bulk densi y, nu ien concen a ions and s and basal a ea o he ee species a e men ioned in Table 1. Ing ow h co e p epa a ion and ins alla ion The ing ow h co es we e p epa ed and ins alled as de- sc ibed by Laiho e al. (2014). The co es we e made o polyes e ab ic wi h mesh size app oxima ely 1-mm × 1-mm. The ini ial diame e o he illed co es was 3.2 cm. The e ec i e leng h o he co e was 50 cm wi h an addi ional ail ha emained un illed and abo e g ound, o acili a e loca ing he co es a e incuba ion. Two ypes o pea subs a e we e chosen o mimic he soil quali y o he ecipien si e as closely as possible. Fo he d ained bog o es , whe e he pea was mos ly o bog-moss (Sphagnum L.) o igin, non- e ilized ho icul- u al Sphagnum pea was used. The d ained en o es was cha ac e ized by sedge (Ca ex L.) pea , and hus sedge pea ha es ed o ene gy use was used o ha si e. The bulk densi y o pea in bo h si es was checked and he illing was planned o mimic ha in 10-cm sec ions. Fo he bog o es his was qui e success ul, while o he en o es he bulk densi y was somewha highe in he co es han in he si e (Laiho e al. 2014). In all, 60 ing ow h co es we e ins alled a each si e in wo di e en ansec s, 30 co es in each ansec , in g oups o h ee a 10 di e en poin s along he ansec s. Each ansec s e ched ac oss a s ip be ween wo di ches. The i s and las g oup we e ins alled se e al me es away om he di ch ma gins o a oid he une en di ch banks and he es a abou 4-m in e als. In he d ained bog o es , he co es we e ins alled in la e Oc obe 2009 and in he d ained en o es in ea ly May 2010, jus be o e he g owing season, because ea ly soil os p e en ed ins alla ion du ing he p eced- ing au umn. The i s se o co es was eco e ed a e one g owing season in No embe 2010, ollowed by he second and hi d eco e ies in No embe 2011 and 2012, espec i ely. Each yea , a single co e was eco - e ed om each o he 10 g oups along each ansec , esul ing in 20 co es pe si e pe yea . Du ing emo al o he co es, a long sha p kni e was used o gen ly cu Plan Soil a ound he co es o de ach any abo eg ound plan pa s a ached o o g owing h ough he co es and o cu he oo sys ems, o a oid pulling ou oo s om he co es. The loca ion o he soil su ace a he ime o eco e y was ma ked in he co es, when di e en om he ime o ins alla ion. A e emo al, he co es we e cu in o i e segmen s, based on he ma ks (10-cm in e als) made in each co e a p epa a ion, w apped in plas ic oil wi h hei incuba ion loca ion ma ked and ozen (−20 °C) un il u he ea men . Sepa a ion o ine oo s In he labo a o y, he ing ow h co es we e aken om he eeze and placed in a e ige a o o e nigh o de os . One o wo co es we e de os ed a a ime o a oid decomposi ion a e de os ing. Any abo e-g ound bio- mass ha was a ached o he co es was emo ed. The diame e o each segmen was measu ed om bo h ends, and he ac ual segmen leng h was eco ded (Table S1in Supplemen a y ma e ial). All he oo s ound ou wa d o a co e segmen we e cu along he ab ic su ace, and he oo s inside he co e we e sepa a ed, using a pai o weeze s, washed o emo e any pea emains and col- lec ed in a Pe i dish. The pea o each segmen was also collec ed o de e mina ion o bulk densi y. Li ing ine oo s we e sepa a ed and so ed om he second- and hi d-yea co es by ee species and unde s o ey unc ional g oups, while i s -yea ine oo s we e sepa a ed as o al oo s. Some dead oo s we e ound in he second-yea co es and we e pooled as ‘ o al dead oo s’. As we assumed and obse ed, he e we e mo e dead oo s in he hi d-yea co es; hey we e so ed by species and unc ional g oups. In he en o es , h ee hi d-yea co es ou o 20 we e no sepa a ed by ee species and unde s o ey unc ional g oups, bu a he pooled as o al oo s. Fu he mo e, all he oo s we e so ed in o h ee diame e classes: ≤1mm,1–3mmand 3–5 mm, since hese we e he mos commonly used diame e classes (Finé e al. 2011). The oo s we e kep a oom empe a u e o abou 24 h o e apo a e he wa e , hen o en-d ied o cons an mass a 30 °C and weighed o 1-mg p ecision. In mos cases, he leng h o he opmos segmen was less han 10 cm a e eco e y (Table S1in Supplemen a y ma e ial), ei he due o a change in he soil su ace, which may be qui e dynamic in pea lands, o pea sh inkage o bo h. The mean leng hs (± s anda d de ia ions) o he op 0–10-cm laye a e eco e y, in he bog o es we e 8.1(± 0.7), 7.9 (± 0.7) and 6.9 (± 0.8) cm o he i s , second and hi d yea , espec i ely, and he co esponding alues o he en o es we e 9.4 (± 1.1), 9.6 (± 0.4) and 9.1 (± 1.2) cm, espec i ely. The ac ual leng hs o he subsequen laye s we e gene ally close o he o iginal leng h (10 cm) in bo h he bog and en o es s. Based on his we co ec ed he biomass alues o hose opmos segmen s in which he majo i y o he oo s occu ed, o a oid unde es ima ion o bio- mass (n= 60 o 60 o Kale ansuo and 47 o 60 o Le osuo). This was done by calcula ing he biomass pe cen ime e o segmen and mul iplying he alue by 10 cm. This co ec ion e ec o he 0–10-cm laye inc eased he o al FRP by 7 % o he i s yea , 11 % o he second yea and 13 % o he hi d yea in he d ained bog o es . The co esponding igu es o he d ained en o es we e 8 %, 3 % and 10 %, espec i ely. Iden i ica ion o ine oo s The compa a i e iden i ica ion o ee species and unde s o ey unc ional g oups was done in ou s eps. Fi s , we dis inguished and sepa a ed he oo s o ees (Sco s pine, No way sp uce and downy bi ch), p ima ily based on he oo s ha ing ec omyco hizal ips, unlike he unde s o ey species ha hos e icoid myco hizae (in isible) (Tables 2and 3). Second, we iden i ied he Table 1 Cha ac e is ics o he s udy si es. Soil bulk densi y (BD; gcm −3 ), N, P and K concen a ions (mg g −1 ) and C: N a ios a e based on he 0–20-cm pea laye . The s and basal a ea is he sum o he ee s em c oss-sec ional a eas measu ed a 1.3 m, in m 2 ha −1 , sepa a ely o Sco s pine, downy bi ch and No way sp uce. O he da a as in Laiho e al. (2014); unde s o ey ege a ion co e age da a a e om he p esen s udy (de ails in he Resul s sec ion) Si e Type BD N P K C:N S and basal a ea Unde s o ey ege a ion % Pine Sp uce Bi ch Sh ubs He bs Kale ansuo Bog o es 0.093 14 0.56 0.31 36.0 17.6 < 0.1 0.7 29.1 < 0.5 Le osuo Fen o es 0.162 23 0.79 0.23 24.5 17.4 4.5 6.1 4 10.6 Plan Soil Sco s pine oo s, p ima ily by hei easily iden i ied dicho omously b anched myco hizae, and colou : Sco spinewasligh e incolou hanNo waysp uce. Nex , we sepa a ed he oo s o No way sp uce and downy bi ch by compa ing hei oo and ip mo phol- ogy, as shown in Table 2. Finally, he he b oo s, includ- ing g aminoids and o bs, we e sepa a ed om sh ubs mainly by hei yellowish, cu ly and long ine- oo s uc u e (Table 2). These c i e ia we e de eloped be o e oo so ing, using samples o known species om he s udy si es and based on p e ious wo k by ou eam (Helmisaa i and B unne 2006; Helmisaa i, H-S, pe - sonal communica ion). The dead oo s we e mainly sepa a ed based on col- ou , appea ance o he phloem (ou e laye o ba k), elas ici y o he issue and oughness (Pe sson 1983; Tu ekcioglu e al. 1999; Laiho and Finé 1996). These p ope ies we e checked unde a s e eomic oscope. When he oo s we e da k in colou , we sc a ched he ex e io co ex o look o he inne colou , and he oo s we e conside ed li ing when he inne colou was whi e, yellow o g ey and he issue was elas ic. In con as , he dead oo s we e mos ly b own, da k o black, b oke easily and we e in a ious s ages o decay (Table 3). A oo was conside ed dead when i showed he cha ac e - is ics desc ibed in Table 3along i s ull leng h. Pa ially dead oo s we e conside ed li ing. Howe e , when pos- sible, dead oo le s a ached o he li ing oo s we e sepa a ed wi h scisso s. Du ing sepa a ing and washing, some pa s o oo s bo h li ing and dead agmen ed in o small pieces ( agmen s less han 1 mm) and could no be collec ed. Backg ound da a Unde s o ey ege a ion analysis A ege a ion su ey was done a each ing ow h co e g oup (10 g oups pe ansec , wo ansec s pe si e) in ea ly Sep embe 2014. In he d ained bog o es , we used a 200-cm × 50-cm plo o co e he loca ions o he h ee ing ow h co es pe g oup, while in he d ained en o es a 100-cm × 100-cm plo was analysed. The pe cen age p ojec ion co e age o he unde s o ey plan species and moss species g oups was eco ded. The es ima ion was done on 20 plo s a each si e, using he co e age scale o <1, 1, 2, 5, 10, 15, 20, 30, …,100% o each species o species g oup. Table 2 Compa a i e c i e ia o mo phological a ibu es o iden i ying he ine oo s and hizomes o di e en species and unc ional g oups. The compa isons we e mos ly needed be ween sp uce and bi ch and be ween sh ubs and he bs C i e ia Sco s pine No way sp uce Downy bi ch Sh ubs He bs Colou Ligh e Reddish/da ke Yellowish Da ke han he bs Ligh e and yellow Myco hizal ip Dicho omously b anched S aigh , sho Cu ly/cu ed, long No ec omyco hizal ips No ec omyco hizal ips Fi mness o oo co ex Less i m and easily b oken while washingcompa ed obi ch Mo e i m S uc u e o hizome /s aigh ness Less s aigh S aigh compa ed o sp uce Plain, s aigh and sho No s aigh , a he cu ly and long Roo ips/co ex B anchy Less b anch, ips b oade Thickness Thicke Thinne Thinne ine oo s Plan Soil Wa e - able le el and soil empe a u e measu emen s The luc ua ions in oo biomass du ing he g owing seasons a e caused by se e al ac o s, including soil empe a u e (Ly and Ho man 1967;K ame and Kozlowski 1979) and he dep h o he wa e able (WT) le el (Heiku ainen 1955). To e alua e he FRP pa e ns in ela ion o he soil empe a u e p o ile and WT le el, we measu ed bo h a he si es. The WT le el was measu ed, using a T uT ack Da a Logge (h p:// www. u ack.com/w -h .php). The soil empe a u es a dep hs o 5, 10, 20 and 30 cm we e measu ed wi h P - 100 empe a u e p obes connec ed o a Noke al 680 logge (Noke al Oy, Nokia, Finland) and eco ded in a desk op compu e unning a Py hon sc ip . The WT le el du ing he g owing seasons (May– No embe ) o he second-yea s udy pe iod was abou 40 cm below he su ace in he d ained bog o es and 50 cm in he en o es (Fig. 1). A bo h si es he soil empe a u es peaked in July. The empe a u es de- c eased om he su ace o he deepe laye s du ing May–Augus , we e simila in Sep embe and in e sed in Oc obe –No embe (Fig. 1). Due o he dynamics, he mean soil empe a u es du ing he oo -g owing season we e a he simila in all he laye s and a bo h si es. The mean empe a u es a 5, 10, 20 and 30 cm below he su ace we e 10.9, 10.3, 10.2 and 9.7 °C, espec i ely, in he d ained bog o es and in he d ained en o es 10.2, 9.7, 9.3 and 8.8 °C, espec i ely. Calcula ion o ine- oo p oduc ion Con en ionally, when ing ow h co es wi h sho incu- ba ion imes (1 o < 2 y . ) a e used, FRP is es ima ed as he mass o he ine oo s ex ac ed om he ing ow h co e (Idol e al. 2000; Val e de-Ba an es e al. 2007; A agão e al. 2009;B assa de al.2011; Laiho e al. 2014). Bu using such sho incuba ion imes (< 2 y ) may esul in unde es ima ion (S eele e al. 1997; Vog e al. 1998; Finé and Laine 2000). The e o e, o ob ain a s eady-s a e FRP (S eele e al. 1997; Finé and Laine 2000; Lukac and Godbold 2001), mul iyea biomass da a a e needed, which is mo e complica ed because in ine- oo dynamics, he oo s g ow and die con inuously du ing he g owing seasons. P e iously, FRP based on Table 3 Compa a i e c i e ia o dis inguishing dead oo s om li ing oo s C i e ia Li ing oo s Dead oo s Colou o hizome Ligh colo : whi e, ligh b own, g ey, yellow; some imes da k i sube ized B own, da k o black Colo o oo ips Ligh ; b own, whi e Da k, black Ba k Mo e i m Los o losing ba k; sc a ch in he ba k (i ligh in colou hen li ing oo s) S i ness S i Ve y loose, b oken S uc u e o oo ips Swollen, in la ed and ound shape Sh ink, d ied and dis o ed Elas ici y o oo s Mo e elas ic, can bend easily F agile, can be b oken easily Fig. 1 Wa e - able (WT) le el in cm om he su ace (dashed line, scale on he igh ) and soil empe a u e (T) in °C a di e en dep hs om he su ace (solid lines, scale on he le ) in he (a) d ained bog o es and (b) d ained en o es du ing he second incuba ion yea (2011) Plan Soil mul iple pe iods/yea s o ing ow h biomass da a has been es ima ed by ei he 1) di iding he ine oo bio- mass by he incuba ion ime (Yuan and Chen 2012)o 2) sub ac ing he ine oo biomass o consecu i e incuba- ion imes (Finé and Laine 2000). He e, we epo he esul s o bo h me hods and e e o hem as 1) ing ow h- di iding (ID) and 2) ing ow h-sub ac ing (IS) me hods. The la e me hod esembles he decision-ma ix me hod by Fai ley and Alexande (1985), whe e hey epo ed o es ima e FRP by he di e ence in biomass o he incu- ba ion imes. So a , he e a e no s udies a ailable in which he esul s o he wo FRP es ima ion me hods, ID and IS me hods, ha e been compa ed, using se e al yea s o da a om di e en si es. We used he o al oo masses (including li ing and dead oo s) in bo h he ID and IS me hods. Since some o he dead oo s we e p obably decomposed (i.e. had los some mass) and some could p obably no longe be iden i ied, he oo p oduc ion could ha e been unde es ima ed. Thus, we added 30 % mass o he dead oo mass, which is he i s -yea mass loss a e s udied o a ange o pea land species in sou he n Finland (S ako á e al. 2012). Based on he dead ine- oo alues obse ed (p esen ed in he Resul s sec ion), we assumed ha mos dead oo s obse ed had been dead and decomposing o a maximum o 1 yea . S a is ical analysis To suppo he me hodological wo k, we i s used e- pea ed measu es analysis o a iance o e alua e he di e ences in o al FRB and o al dead- oo mass ob- se ed in he in-g ow h co es be ween he wo si es, wo ansec s o each si e and he h ee incuba ion imes. We conside ed he ansec and si e as be ween-subjec (g ouping) ac o s and incuba ion ime (yea s) as he wi hin-subjec ( epea ed) ac o . Nex , he di e ences in yea ly FRP es ima ed by ID and IS me hods based on di e en incuba ion imes we e es ed using a simple - es . He e, we sough o de e mine, which me hod and which incuba ion ime can be conside ed o esul in he ‘bes es ima e’ o desc ibe FRP. This es ima e should be as obus and esou ce-e icien as possible, ha is, i should luc ua e as li le as possible o e he yea s, and u ilize as sho an incuba ion ime as possible. When he ‘bes es ima es’o FRP we e chosen, we also used he epea ed measu es analysis o a iance o e alua ing he FRP pa e ns, conside ing si e and ansec as g oup- ing ac o s and dep h as he epea ed ac o . A his s age, he leng h o he incuba ion ime needed no o be conside ed, since i was ixed when choosing he ‘bes es ima es’. Du ing analysis, we ound conside able de- pa u e om sphe ici y in all cases ( a iances di e ed among dep hs). The e o e, we applied he G eenhouse- Geisse co ec ion alue in he in e p e a ion o he F- a ios, because he es ima e o sphe ici y (epsilon alue) was always smalle han 0.75. All hese analyses we e done, using IBM SPSS s a is ics 22 (IBM Co p., A monk, NY, USA). The ela ionship be ween FRP and unde s o ey ege a- ion composi ion was e alua ed, using p incipal compo- nen analysis (PCA) in Canoco 5. The o dina ion was based on he p ojec co e o he unde s o ey ege a ion species and moss g oups (Sphagnum mosses e sus o es mosses including Pleu ozium sch ebe i, gli e ing wood- moss Hylocomium splendens (Hedw.) Schimp. and Dic anum polyse um) eco ded o each ing ow h co e g oup. The co ela ions be ween he plan communi y composi ion, as desc ibed by p incipal componen s 1 and 2, and he FRP bes es ima es o each ee species and unde s o ey unc ional g oup we e es ima ed and p ojec ed on he o dina ion space as supplemen a y a iables. Resul s Fine- oo biomass and dead- oo mass The o al FRB obse ed in he co es inc eased signi i- can ly wi h incuba ion ime (1–3 y ) a bo h si es, as did he dead- oo mass om yea 2 o yea 3 (Tables 4and 5). The d ained en o es showed each yea signi ican - ly la ge biomass and dead- oo mass han did he d ained bog o es (Tables 4and 5). The dead oo s in he second yea accoun ed o only 2 % o he o al oo mass a bo h si es. The p opo ion o dead oo s in he hi d yea inc eased o 7 % in he d ained bog o es and 11 % in he d ained en o es . Bo h he FRB and dead- oo mass dec eased om he opmos 0–10-cm down o he 40–50-cm laye s a bo h si es (Table 5). Es ima ion o ine- oo p oduc ion The FRP es ima ed by he ID me hod showed simila alues o he second and hi d yea s a bo h si es. The es ima es we e 244 and 224 g m −2 o he second and hi d yea s in he d ained bog o es , and 561 and 552 g m −2 in he d ained en Plan Soil o es , espec i ely. In con as , he IS me hod esul ed in di e en alues o he second and hi d yea s (Fig. 2a, p < 0.001). The IS me hod es ima es showed o e all maximum alues o he second yea and mini- mum alues o he hi d yea , i.e. 370 and 184 g m −2 in he d ained bog o es and 906 and 535 g m −2 in he d ained en o es , espec i ely. The second-yea es i- ma ion by IS me hod was clea ly highe , due o he low biomass g ow h du ing he i s yea , whe eas ha o he hi d-yea es ima ion was simila o he es ima es o he ID me hod. To summa ize, he ID me hod esul ed in mo e obus es ima es and consequen ly, we conside ed ha i should be u ilized o he ‘bes es ima es’o FRP. Since he second- and hi d-yea ID es ima es we e simila , we conside ed ha wo-yea incuba ion ime is su icien and may be used o he ‘bes es ima es’in u u e s udies o sa e ime. Consequen ly, we hence o wa d examine he pa e ns in FRP using ID es ima es based on wo- yea da a as he ‘bes es ima es’. To al ine- oo p oduc ion The bes es ima e o FRP in he en o es , 561 g m −2 , was mo e han wice ha in he bog o es , 244 g m −2 , and he di e ence be ween he si es was signi ican (Table 6). Bo h bog and en o es s showed signi ican di e ences in he FRP alloca ion by dep h (Table 6, Fig. 3). Mos o he oo p oduc ion occu ed in he uppe 0–20-cm laye : 82 % and 76 % o he o al oo p oduc- ion a he bog and en si es espec i ely. The dep h and si e in e ac ion was also signi ican , indica ing di e ing FRP dep h p o iles o he si es (Table 6,Fig.3). Mos o heFRP(92%)was oundin he≤1-mm diame e class a bo h si es (Table 7). Howe e , in he d ained en o es he sh ub g oups showed ela i ely mo e FRP in he 1–3- mm diame e class, accoun ing o 25 % o he o al FRP. We obse ed negligible amoun s o FRP in he 3–5-mm diame e class (< 1 % o he o al FRP) and included his in he 1–3-mm diame e class. No sys ema ic pa e ns o FRP we e ound in ela ion o dis ance om he di ch in ei he he d ained en o d ained bog o es . Fine- oo p oduc ion by species and unc ional g oups Al hough he o al annual FRP was highe in he d ained en o es han he bog o es , he species- le el FRP showed di e ences ela ed o species composi ion (Fig. 3). The FRP o Sco s pine and he bs did no di e be ween he si es. The FRPs o sh ubs we e g ea e in he bog o es han in he en o es (Table 6,Fig.3), while he FRPs o No way sp uce and downy bi ch we e highe in he en han in he bog o es s. The FRPs o Sco s pine, No way sp uce and he sh ub unc ional g oups di e ed signi ican ly among he soil laye s a bo h si es. O all he species, only No way sp uce showed di e en dep h p o iles o he wo si es (Table 6, dep h-si e in e ac ion, p < 0.001). Downy bi ch demons a ed no signi ican di e ences in he FRP alloca ion by dep h a ei he si e, indica - ing cons an FRP along he soil p o ile (0–50-cm laye s). All o he he b FRP in he d ained en o es Table 4 P alues om epea ed measu es analysis o a iance o he e ec s o ansec (T), si e (S) and incuba ion ime (Y) on o al ine- oo biomass and dead- oo mass (g m −2 )ind ainedbogand en o es s, sepa a ely and combined (bo h si es). The P alues in bold we e s a is ically signi ican a an alpha le el o 0.05. Da a we e om ing ow h co es o h ee consecu i e yea s (wi hin- ac o Yea ) Be ween subjec s Wi hin subjec s Cha ac e is ics T S S*T Y Y*T Y*S Y*T*S To al biomass Bog 0.106 <0.001 0.646 Fen 0.416 <0.001 0.645 Bo h si es 0.199 <0.001 0.78 <0.001 0.745 0.001 0.56 To al dead- oo mass Bog 0.82 0.001 0.829 Fen 0.219 <0.001 0.262 Bo h si es 0.277 <0.001 0.212 <0.001 0.273 <0.001 0.31 Plan Soil Table 5 Mean ine- oo biomass and dead- oo mass, g m −2 ± s anda d e o , by dep h o o al oo mass and ha o each species (Sco s pine, No way sp uce, downy bi ch) and unc ional g oup (sh ub, he b) in ing ow h co es eco e ed a e i s (2010), second (2011) and hi d (2012) incuba ion yea s in d ained bog and en o es s. N = 20 o each incuba ion ime a bo h si es 2010 2011 2012 Dep h To al Li ing oo Dead oo Li ing oo Dead oo (cm) Pine Sp uce Bi ch Sh ubs He bs To al To al Pine Sp uce Bi ch Sh ubs He bs To al Pine Sp uce Bi ch Sh ubs He bs To al Bog o es 0–10 47.4 151.8 32.2 6.5 67.0 0.0 257.6 3.1 165.2 29.8 8.0 75.2 0.0 278.1 8.8 0.0 0.0 0.0 0.0 8.8 (±9.5) (±34.3) (±17.7) (±4.6) (±21.9) 0.0 (±37.2) (±1.7) (±30) (±16.7) (±5.8) (±17.1) 0.0 (±37) (±3.5) 0.0 0.0 0.0 0.0 (±3.5) 10–20 34.7 74.1 13.2 1.1 46.3 0.0 134.7 1.7 95.9 11.0 11.6 45.3 4.1 167.9 7.7 0.0 0.0 0.0 1.8 9.5 (±7.6) (±18.1) (±8.9) (±1.1) (±11.3) 0.0 (±24.1) (±0.9) (±17.7) (±8) (±6.8) (±11.8) (±4.1) (±25) (±2.2) 0.0 0.0 0.0 (±1.8) (±2.6) 20–30 14.4 12.1 3.2 4.2 16.9 0.0 36.5 0.8 41.9 5.3 6.1 27.3 4.1 84.8 8.6 0.0 0.0 0.0 2.7 11.3 (±4) (±3) (±1.6) (±3.8) (±5.7) 0.0 (±7.5) (±0.5) (±13.1) (±3.2) (±4.5) (±11.4) (±4.1) (±21.5) (±2.7) 0.0 0.0 0.0 (±2.7) (±4) 30–40 10.6 16.0 8.2 6.4 3.5 0.5 34.6 1.0 29.1 0.9 6.1 17.2 0.6 53.9 5.0 0.0 0.0 0.0 2.4 7.4 (±5.1) (±4.3) (±6.1) (±6.4) (±2.1) (±0.5) (±10.5) (±0.5) (±9) (±0.9) (±4.3) (±7.0) (±0.6) (±13) (±1.6) 0.0 0.0 0.0 (±2.1) (±2.6) 40–50 10.6 13.1 0.2 0.4 2.8 0.4 16.9 0.6 25.1 0.0 5.0 8.7 0.5 39.3 8.4 0.0 0.0 0.0 1.7 10.1 (±4.2) (±4.4) (±0.2) (±0.4) (±1.9) (±0.4) (±4.8) (±0.3) (±6) 0.0 (±3) (±3.0) (±0.5) (±7.9) (±2.3) 0.0 0.0 0.0 (±1.7) (±3.1) To al 117.8 267.2 57.0 18.7 136.4 0.9 480.3 7.2 357.2 47.0 36.8 173.7 9.3 624.0 38.6 0.0 0.0 0.0 8.5 47.1 (±19.3) (±46.8) (±23.1) (±14.8) (±30.1) (±0.6) (±52.7) (±1.8) (±49.5) (±26.2) (±20.7) (±37.9) (±9.3) (±67.7) (±7.4) 0.0 0.0 0.0 (±8.3) (±11) Fen o es 0–10 142.7 80.0 393.2 88.6 34.8 0.0 596.6 7.8 107.7 545.9 121.3 15.1 13.1 846.0 21.0 30.5 4.3 0.4 0.0 59.9 (±16.9) (±28.6) (±73.5) (±46.6) (±19.2) 0.0 (±68.5) (±2.5) (±44.9) (±110.9) (±42.3) (±8.1) (±11.5) (±114.6) (±13.8) (±13.1) (±2.2) (±0.4) 0.0 (±16.1) 10–20 38.2 50.5 129.8 55.5 5.7 0.3 241.9 2.6 40.1 197.1 89.8 6.9 0.4 331.2 9.5 23.0 5.3 3.3 0.0 41.5 (±6.8) (±18.5) (±41.8) (±17.8) (±2.7) (±0.3) (±48.6) (±1) (±23.6) (±49.5) (±31.8) (±5.1) (±0.4) (±55.5) (±3.8) (±7.8) (±2) (±3.1) 0.0 (±11.1) 20–30 17.2 29.5 104.5 18.7 10.9 1.3 165.0 4.0 36.9 93.4 65.7 0.3 0.0 203.8 4.1 17.3 5.2 0.0 0.1 25.1 (±4.5) (±14,1) (±36.6) (±7.8) (±9) (±1) (±37.1) (±1.3) (±19) (±36) (±27.6) (±0.3) 0.0 (±39.3) (±2) (±6.6) (±2.1) 0.0 (±0.1) (±6.3) 30–40 10.5 5.2 49.9 18.6 1.4 0.4 75.5 1.9 6.0 16.4 38.3 0.0 0.0 67.7 2.8 10.3 8.1 0.6 0.2 23.4 (±2.6) (±3.2) (±28.4) (±8.7) (±0.9) (±0.4) (±28.2) (±1) (±4.9) (±8) (±14.3) 0.0 0.0 (±14.9) (±1.1) (±5.3) (±3.5) (±0.6) (±0.2) (±6.6) 40–50 6.0 1.7 19.6 2.5 0.8 0.0 24.5 1.1 2.5 9.1 14.6 0.1 0.0 24.7 6.3 9.0 9.5 0.1 0.0 32.3 (±2.2) (±1.3) (±9.7) (±2) (±0.5) 0.0 (±9.6) (±0.8) (±1.7) (±4.8) (±5.6) (±0.1) 0.0 (±8,1) (±4.9) (±4.2) (±3.5) (±0.1) 0.0 (±9.1) To al 214.7 166.8 697.0 184.0 53.6 2.1 1103.5 17.5 193.2 861.8 329.7 22.4 13.5 1473.4 43.5 90.0 32.3 4.4 0.3 182.2 (±25) (±46.6) (±146.3) (±68.2) (±24.3) (±1.7) (±122.2) (±3.2) (±64.8) (±175.2) (±103.5) (±12.4) (±12) (±179.7) (±18.5) (±22.1) (±9.7) (±3.7) (±0.2) (±28.5) Plan Soil 2011), which may be e lec ed in he FRP as well. The ex ensi e No way sp uce FRP in he en o es may u he be explained by he s ong compe i i e po en ial o his species esul ing om i s highe shade ole ance (Kuusela 1990). The p esen s udy demons a ed highe sh ub FRP in he bog o es (68 g m −2 y . −1 ) han in he en o es (27 g m −2 y . −1 ), closely ollowing he di e ences in sh ub co e . In con as , Finé and Laine (2000)es ima - ed lowe sh ub FRP (17 g m −2 y . −1 ) in bog o es s han in en o es s (67–142 g m −2 y . −1 ), using ing ow h co es. Thei bog o es was o he same si e ype i.e. domina ed by dwa sh ubs, as ou s, while he nu ien s a us o hei en o es s was sligh ly lowe han ou s. Howe e , ou sh ub FRP is in acco dance wi h ha o Finé and Laine (1998) ield laye s, es ima ed by he sequen ial co ing me hod. This may indica e ha ou modi ied me hod indeed esul ed in ewe dis u bances and acili a ed mo e apid coloniza ion o sh ub ine oo s han did p e ious ing ow h co e me hods. The isual iden i ica ion o di e en ee species and unc ional g oups is labo ious and may in some cases be a bi a ywhenmany ee oo sg owin hesamelaye and appea simila in colou and s uc u e. This may lead o misiden i ica ion o some oo s among he a ious species. The sepa a ion o dead oo s om pea is an e en mo e subjec i e p ocedu e. This bias o sys ema ic e o in iden i ying he species and unc ional g oups could a ec he speci ic biomass, p oduc ion and u n- o e es ima es, and hese e o s a e o cou se ela i ely la ge in species wi h small oo biomasses. Howe e , he PCA suppo ed ou iden i ica ion, showing a logical associa ion o he FRP o he ee species and unde s o ey unc ional g oups wi h ha o he abo e g ound co e . Fine- oo p oduc ion and annual ca bon luxes Fine oo u no e (FRT), which desc ibes he a e o ine- oo li e inpu in o he soil, is c ucial o he below- g ound C budge as well as nu ien cycling. A ough es ima e o FRT may be calcula ed by di iding he FRB by he FRP. Based on he FRP esul s o his s udy, we ob ained h ee es ima es o he FRT, based on he maximum biomass = hi d-yea biomass (Gill and Jackson 2000), he mean biomass = mean o second- and hi d-yea biomasses (McClaughe y e al. 1982) and he independen biomass measu ed by Ojanen e al. (2013 and 2014) (Table 9). In case o he mean biomass, we used he mean o only second- and hi d- yea ing ow h biomass, because i s -yea FRBs we e unde es ima es, since i equi ed ime o he oo s o colonize new spaces in he soil (Finé and Laine 2000; He el and Leuschne 2002). Fo he bog o es , all he es ima es ag eed qui e well. In con as , o he en o es , he FRT es ima es using he maximum and mean biomasses o he ing ow h co e we e simila bu inconsis en wi h he FRT o he independen biomass. This is because he independen FRB was clea ly smalle han he FRB based on ou ing ow h co es. Howe e , he FRT using bo h he maximum and mean biomass alues somehow ag eed wi h s udies o mine al soils by Hansson e al. (2013) in a mixed coni e s and and Leppälammi-Kujansuu e al. (2014) in a sp uce- domina ed s and. The FRT es ima ed, using he biomass ound in he ing ow h co es, a he han using he inde- penden FRB, may in ac be mo e ealis ic, since bo h he FRP and FRB in he co es ep esen he same ine- oo sys em. In he su ounding soil, he FRB is cons ained by he whole oo sys em including he hicke oo s, and hus i is inhe en ly di e en om he FRB in he co es. Es ima ing he ine- oo media ed C lux o he soil is clea ly e y sensi i e o bo h he FRB and FRP es ima es used, and we conclude ha insu icien da a a e a ailable o eliably es ima ing his lux. O e all, i seems ha ob aining consis en es i- ma es is mo e challenging o nu ien - ich han nu ien -poo si es. Acknowledgmen s This esea ch was unded by he Maj and To Nessling ounda ion and he Finnish Fo es Resea ch Ins i u e (p ojec 3609). 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