Carbon stores in tree & understorey roots - relationships to site, stand and climate factors Helmisaari, H-S., Derome, J., Kukkola, M. & Nöjd, P.

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1 Carbon stores in tree & understorey roots - relationships to site, stand and climate factors Helmisaari, H-S., Derome, J., Kukkola, M. & Nöjd, P.

2 Carbon stores and fluxes in forest ecosystems Deposition Net Primary Production Above-ground biomass Trees, understorey Harvesting Through fall Litter Harvesting residue Below-ground biomass Soil organic matter Soil respiration Leaching

3 Importance of below-ground carbon Detailed understanding of below-ground carbon pools and fluxes needed to reliably estimate carbon budgets Below-ground processes: regulate storage of large quantities of carbon potentially very sensitive to direct and indirect effects of elevated CO 2, temperature and water availability ~33% global annual NPP used for production of fine roots (Jackson et al. 1997) There has been very little data available about fine root contribution to carbon budgets

4 Aims 1) to describe the variation of Norway spruce and Scots pine fine root and understorey below-ground biomass and their carbon pools 2) to assess relationships between fine root biomass and site, stand and climate factors

5 Quantification of carbon stores Stand level measurements Relationships to site/stand/climate National Forest Inventory data Regional/national estimates

6 Fine roots (Ø < 2 mm) 80 % of tree fine roots Ø < 1mm mostly mycorrhizal dynamic but also long-living 1 mm Image size 1 x 1.3 cm Photos: mycorrhizal fine root minirhizotrone images from Kivalo Scots pine (upper) and silver birch (lower) stands, Project 3324/Helmisaari

7 Coarse roots Ø > 2 mm Photo: Laitakari (1927)

8 Network of fine root research sites Kevo Sevettijärvi 25 stands, field research during Pallasjärvi Sodankylä Kemijärvi Kivalo Oulanka Scots pine Norway spruce Ylikiiminki Birch Pyhäntä Uusikaarlepyy Lieksa Närpiö Parkano Ilomantsi Vilppula Jämijärvi Punkaharju Juupajoki Ikaalinen Sahalahti Harjavalta Heinola Kokemäki Jokioinen Evo Lapinjärvi Tammela Miehikkälä Ruotsinkylä Virolahti Solböle soil cores for biomass ingrowth cores and minirhizotrone measurements for dynamics in selected stands

9 RESULTS Variation of fine root biomass and carbon

10 Can we estimate the average fine root biomass using site & stand factors? Fine root biomass, kg/ha and Latitude R 2 = 0.75 Temperature sum R 2 = 0.73 Regressions better on tree than stand level Fine root biomass, kg/tree and Needles, kg/tree R 2 = Basal area, m 2 /tree R 2 =

11 Fine roots and rhizomes Understorey roots an important soil carbon pool in the north Biomass C, kg/ha Production C, kg/ha/year 0.6 Grasses Dwarf Shrubs shrubs Pine *Scots pine stand at Kivalo, northern Finland Numbers= turnover rates (annual biomass production/biomass)

12 Root carbon, kg C ha -1 Living roots South North Spruce stands Pine stands Dead roots (recently dead, still detectable as roots) Spruce stands Pine stands * Root Ø < 5 mm

13 Soil and root carbon in different layers C, g/dm 3 C, g/dm Soil C25 C50 C75 6 Roots Depth, cm Depth, cm Soil data: Tamminen & Starr (2006) Humus layer and four depths in mineral soil * Root carbon: living & dead roots Ø< 5 mm (16 stands)

14 Roots account up to 50 % of humus layer carbon in northern Finland C, kg/ha Roots (d< 5 mm) Soil North, Kivalo South, Tammela Root carbon: living & dead roots Ø< 5 mm Norway spruce stands

15 Digital photo image of humus layer- Scots pine stand at Kivalo Image size 1 x 1,3 cm Project 3324/Helmisaari 1 mm

16 Seasonal variation in fine root biomass 0 May August October 2000 Fine roots, g/m *Norway spruce stand at Sahalahti, southern Finland Organic layer and 0-10 & cm mineral soil layers

17 Annual variation in fine root biomass production Production, g/m 2 /year C-1998 C-1999 C-2000 C Mean drought * Norway spruce stand at Sahalahti, southern Finland Variation in measured tree fine root turnover rates

18 Large variation in turnover rates Global change models have yet to incorporate the variability in root turnover rates (Matamala et al. 2003)

19 Conclusions Total fine root biomass is larger in northern Finland because of larger proportion of understorey (mostly dwarf shrubs) roots Roots account for a large part of humus layer carbon There is large seasonal and annual variation of fine root turnover rate (variation in fine root production and mortality) The magnitude of fine root litter production equals aboveground litter production Fine roots decompose slower than needles

20 Conclusions By using our results, robust estimations of average fine root biomass can be made from stand and site data For detailed understanding of fine root carbon dynamics in varying climate and on different sites, ecosystem level field research is continuously needed Roots, mycorrhizas and their external mycelia in carbon dynamics in forest soil International conference at Rovaniemi

21 Thank you!