Bhuiyan, Rabbil

Laiho, Raija

Minkkinen, Kari

Jukuri

Unearthing fine root production by plantfunctional groups in drained peatlandsthrough in-growth coresIntroductionFine roots mediate significant carbon fluxes inboreal peatlands that are likely to be affectedsubstantially by land use and climate warming.Fine root production data by plant functionalgroups such as herbs, shrubs and trees are stilllargely missing. Recently, we introduced amodification to the ingrowth core method forpeatlands that reduces disturbance andfacilitates a high number of replicates (Laiho etal. 2014). Here, we examine the applicability ofthis method with three years’ data andestimate the production by different speciesand functional groups in two drained peatlandforest sites representing different nutrientstatus: rich and poor.ObjectivesThe study aims at determining- the optimal incubation time for the ingrowthcores,- how to calculate the production values frommultiple years’ biomass data, and- vertical distribution of fine root productionand the contributions of different plantfunctional types in two contrasting sites.MethodsCorer - 20 cores/yr/site Totalinstaller total 120 cores 600 sub-cores10 cm20 cm30 cm40 cm50 cmShrubs HerbsPinus Picea Betulasylvestris abies pubescensMethod1: dividing  masses by years of  incubationMethod2: subtracting masses of consecutive yearsFig 1: Mean fine root production (gm-2yr-1)estimated by method1 and method2Fig 2: Vertical distribution of  total fine rootproduction in both sites, based on the 2nd yearmethod1  estimates (’best estimate’)Table1:  Characteristics of the study sites.  Peatproperties are  avg.  for 0-20 cm and N, P, K  in mg g-1ResultsFigure 1• Method1 showed similar values for secondand third year that did not differsignificantly (P > 0.05) in either site; thus,two years’ incubation time is enough• Accounting for the decomposition of deadroots (assumption: 30 % mass loss duringone year following death) had only a smalleffect on production estimates.• In contrast, method2 results varied muchmore between years and may be consideredto indicate range of productionFigures 2 & 3• Higher production in the rich site across thewhole depth range studied.• Poor site showed relatively higher rootproduction (19%) deep down (30-50 cm)compared to rich site (10%).• Production was significantly different (P ˂0.001) between sites for all plant functionalgroups, except herbs and Scots pine.ConclusionsOur study suggests that the method1(dividing method) is more feasible thanmethod2 (subtracting method), and thatmerely second year sampling is enough forestimating fine root production, whichinevitably reduces study time.ReferencesLaiho R, Bhuiyan R, Strakova P et al. (2014) ModifiedIngrowth core method plus infrared calibration modelsfor estimating fine root production in peatlands. Plantand Soil 358: 311-327.Rabbil Bhuiyan1Kari Minkkinen1Raija Laiho21Department of Forest Sciences,University of Helsinki, Finland2Natural Resource Institute Finland(Luke)HELSINGIN YLIOPISTOHELSINGFORS UNIVERSITETUNIVERSITY OF HELSINKIMAATALOUS-METSÄTIETEELLINEN TIEDEKUNTAAGRIKULTUR-FORSTVETENSKAPLIGA FAKULTETENFACULTY OF AGRICULTURE AND FORESTRY020040060080010001200Method1 Method2 Method1 Method21st yr 2nd yr 3rd yr 3rd yr+decPoor site (Kalevansuo) Rich site (Lettosuo)Sites N P K C:N Basal area ,m2 ha-1Pine Birch SprucePoor site (bog) 14 0,56 0,31 36 17,6 0,7 ˂0,1Rich site (fen) 23 0,79 0,23 24,5 17,4 6,1 4,5Fig 3: Fine root production by species and functionalgroups, based on the 2nd year method1  estimatesPinus sylvestrisFine root production, gm-2yr-10 20 40 60 80Depth,cm 0-1010-2020-3030-4040-50 Picea abiesFine root production,  gm-2yr-10 50 100 150 200 250Betula pubescens0 10 20 30 40 50 60 70Depth,cm 0-1010-2020-3030-4040-50 Shrubs group0 10 20 30 40Herbs group0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4Depth,cm0-1010-2020-3030-4040-50Poor siteRich siteFine root production, gm-2yr-10 50 100 150 200 250 300 350Depth,cm0-1010-2020-3030-4040-50Poor siteRich siteContact: rabbil.bhuiyan@helsinki.fi

Unearthing fine root production by plant functional groups in drained peatlands through in-growth cores

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