Tree species effects on soil C: Overview of Nordic studies and knowledge

Transcription

1 Tree species effects on soil C: Overview of Nordic studies and knowledge Nicholas Clarke, Norwegian Forest and Landscape Institute, with contributions from all partners

2 Much previous work has shown differences in C stocks and fluxes apparently related to tree species, so choice of tree species is among the management options for increasing forest carbon sequestration. What factors account for observed tree species effects?

3 SOC stocks Tönnersjöheden, Sweden (Hansson 2011)

4 Fredriksdal, Sweden (Oostra et al. 2006)

5 Results from two Danish studies: Ladegaard-Pedersen et al. (left) and Vesterdal and Raulund-Rasmussen (right). Forest floor and mineral soil at two sites (left) and forest floor at seven sites (right)

6 Results from a Danish study with a common garden design for the forest floor (left) and mineral soil (right) (Vesterdal et al. 2008)

7 Soil C content in afforestation chronosequences of oak and Norway spruce at Vestskoven, Denmark (Vesterdal et al. 2002)

8 Hallormsstadur, Iceland (Ritter 2007)

9 Total C stocks on Icelandic afforestation sites (Snorrason et al. 2002)

10 C sequestration on Icelandic afforestation sites (Snorrason et al. 2002)

11 ICEWOODS : Unpubl. Results Bjarni D. Sigurdsson Soil C increased: Sitka spruce > Lodgepole pine > Downy birch > Siberian larch C-stock in top 10 cm of soil increased significantly during the first years following afforestation. Average across all species: 1.34 t CO 2 / ha year The change in cm was not significant.

12 Hirkjølen, Norway (Clarke et al. 2005): seminatural Norway spruce and mountain birch Photo: Dan Aamlid

13 De Wit and Kvindesland (1999): Aspen/grey alder forest showed higher total C stocks compared to other forest types, possibly because of alder s N- fixing ability. Photo: John Y. Larsson

14 C input in litter Tönnersjöheden, Sweden (Hansson 2011)

15 Hansen et al. (2009): three Danish sites

16 Decomposition: results from a litterbag study in a Danish common garden experiment (Vesterdal et al. 2012)

17 Decomposition: litterbag experiment at Kangasvaara, Finland (Palviainen et al. 2004)

18 Decomposition of stumps in southern Finland (Palviainen et al. 2010)

19 Carbon losses: DOC Tönnersjöheden, Sweden (Fröberg et al. 2011): lower DOC concentrations under birch O horizon may be related to O horizon thickness

20 Hirkjølen, Norway (Clarke et al. 2005)

21 C mineralisation Tönnersjöheden, Sweden, and Kivalo, Finland (Hansson 2011). Higher mineralisation under spruce may be related to larger C pools rather than mineralisation rate alone

22 C mineralisation rate in laboratory experiments Tönnersjöheden, Sweden, and Kivalo, Finland (Hansson 2011)

23 C mineralisation rates in mineral soil (0-10 cm) under 10 tree species (Ladegaard-Pedersen et al. 2005)

24 Temperature-adjusted mean soil CO 2 effluxes for 10 tree species (Ladegaard-Pedersen et al. 2005)

25 Other factors affecting C stocks and fluxes Soil type Nitrogen Other nutrients Soil acidity Temperature Moisture Water fluxes Extreme weather events, e.g. storms Fire Ground vegetation Soil fungi Soil animals, e.g. earthworms Pathogens, e.g. bark beetles Grazers Forest management These factors will interact with tree species

26 Relationship between foliar litterfall C/N ratio and forest floor total C content in a Danish common garden experiment (Vesterdal et al. 2008)

27 Tönnersjöheden, Sweden (Hansson 2011)

28 Summary General tendency to higher SOC contents in the forest floor under conifers, possibly related to differences in decomposition Not always an effect of tree species on SOC for the soil as a whole Differences in litter quality appear to be important There are interactions between tree species and many other factors, so differences are site-specific

29 Although choice of tree species is clearly a management option for increasing carbon sequestration, other factors must also be considered, for example effects on biodiversity due to invasive tree species. Sitka spruce near Bergen, Norway (photo: Kjersti Holt Hanssen)

30 Thank you for your attention