Fine root dynamics in broad-leaved deciduous forest stands differing in tree species diversity. Catharina Meinen

Transcription

1 Fine root dynamics in broad-leaved deciduous forest stands differing in tree species diversity Catharina Meinen

2 Umbrella Project The role of biodiversity for biogeochemical cycles and biotic interactions in temperate deciduous forests

3 Project B2 Fine root dynamics

4 Background Biodiversity Grassland above-ground: - Biomass - Productivity - Resilience Complementary resource use Tilman et al Below-ground processes in forests?

5 Subprojects Below-ground processes 1. Biomass and morphology 2. Productivity and resilience in pure and mixed forest stands

6 Study site Hainich national park Diversity level 1 Fagus Diversity level 2 Fagus Fraxinus & Tilia M.Daenner Diversity level 3 Fagus, Fraxinus, Tilia, Acer & Carpinus

7 Fine roots < 2 mm in diameter Nutrient and water Mycorrhizae Fagus sylvatica

8 Tree species identification Fig. 4: Fagus sylvatica 1mm

9 Tree species identification Fig. 1: Acer pseudoplatanus 1mm

10 Tree species identification Fig. 2: Fraxinus excelsior 1mm

11 1. Fine root mass

12 Hypotheses (i) Stand fine root biomass increases with increasing tree species diversity (ii) Fine roots of tree saplings contribute significantly to total fine root biomass in stands with abundant offspring

13 Methods Fine root inventory 12 plots 40 cm soil depth Bio- and necromass, according to species Fine roots of tree saplings Fagus s., Fraxinus e. & Acer pseudoplatanus Heigt classes: >1-20 cm >20-40 cm >40-60 cm >60 cm

14 Fine root mass Fine root biomass (g m -2 ) a a a DL 1 DL 2 DL 3 a Fine root necromass (g m -2 ) a a a DL 1 DL 2 DL 3 b (cm) > 40 Tree species diversity

15 Fine root mass Fine root biomass (g m -2 ) a a a DL 1 DL 2 DL 3 a Fine root necromass (g m -2 ) a a a DL 1 DL 2 DL 3 b (cm) > 40 Tree species diversity

16 Fine root biomass Contribution of species to total fine root biomass (%) 0 DL 1 DL 2 DL 3 Acer Fagus Fraxinus Carpinus Tilia Others

17 Biomass - basal area Contribution of species (%) fine root biomass basal area DL 1 DL 2 DL 3 Acer Fagus Fraxinus Carpinus Tilia "others"

18 Biomass - basal area Contribution of species (%) fine root biomass basal area DL 1 DL 2 DL 3 Acer Fagus Fraxinus Carpinus Tilia "others"

19 Biomass - basal area Contribution of species (%) fine root biomass basal area DL 1 DL 2 DL 3 Acer Fagus Fraxinus Carpinus Tilia "others"

20 Fine root biomass of saplings Fine root biomass (g) of tree sapling 3,0 2,5 2,0 1,5 1,0 0,5 y = a + bx r 2 = 0.60 Fraxinus Acer p < r 2 = 0.61 p < Fagus r 2 = 0.49 p < , Tree height (cm)

21 Fine root biomass of saplings Fine root biomass (g) of tree sapling 3,0 2,5 2,0 1,5 1,0 0,5 y = a + bx r 2 = 0.60 Fraxinus Acer p < r 2 = 0.61 p < Fagus r 2 = 0.49 p < , Tree height (cm)

22 Fine root biomass of saplings Species / Diversity levels Fagus sylvatica Fraxinus excelsior Acer spec. Tilia spec. Fine root biomass of tree saplings (g m -2 ) DL 1 DL 2 DL ± 0.1 a A 0.4 ± 0.2 a A 0.1 ± 0.03 a A 0.3 ± 0.2 a A 0.6 ± 0.2 a A 0.7 ± 0.4 ab A 0.5 ± 0.1 a A 1.2 ± 0.7 a A 1.1 ± 0.4 b A ± 0.1 a - Stand total 1.0 ± 0.5α 2.3 ± 1.1α 1.9 ± 0.4α

23 Summary (i) Stand fine root biomass increases with increasing tree species diversity X ca. 450 g m -2 of tree fine root biomass in pure and mixed forest stands

24 Summary (ii) Fine roots of tree saplings contribute significantly to total fine root biomass in stands with abundant offspring X Only minor fine root contribution of tree saplings to total fine root biomass

25 2. Fine root productivity and resilience after disturbance

26 Hypotheses (i) Productivity of the fine root system increases with increasing tree species diversity (ii) Resilience* of the fine root system increases with increasing tree species diversity * Ability of a system to recover after disturbance and restore the initial state

27 Methods Sequential coring 4 dates 3 plots Productivity DL 1a DL 2c DL 3a Ingrowth cores 12 plots (360 cores) 24 month Productivity Resilience after disturbance DL 1 DL 2 DL 3

28 Annual fine root production Annual fine root production (g m -2 yr -1 ) Diversity level Depth (cm) Fagus sylvatica Fraxinus excelsior Tilia sp. Acer sp. Carpinus betulus Other species Herbs Stand total DL 1a DL 2c DL 3a

29 Annual fine root production Annual fine root production (g m -2 yr -1 ) Diversity level Depth (cm) Fagus sylvatica Fraxinus excelsior Tilia sp. Acer sp. Carpinus betulus Other species Herbs Stand total DL 1a DL 2c DL 3a

30 Fine root growth into ingrowth cores 200 b ab a A Tree fine root -2-1 growth (g m yr ) Carpinus Acer sp. Tilia sp. Fraxinus Fagus DL 1 DL 2 DL 3

31 Fine root recovery rate Fine root recovery rate (yr -1 ) Diversity level Depth (cm) Fagus sylvatica Fraxinus excelsior Tilia sp. Acer sp. Carpinus betulus Stand total DL ± 0.03 a 0.26 B ± 0.03 DL ± 0.17 a α 0.37 ± 0.07 a α 0.16 ± 0.08 a α 0.18 ± 0.07 a α 0.34 AB ± 0.07 DL ± 0.54 a α 0.35 ± 0.06 a α 0.63 ± 0.10 b α 0.48 ± 0.18 a α 0.64 ± 0.10 α 0.51 A ± 0.07

32 Fine root recovery rate Fine root recovery rate (yr -1 ) Diversity level Depth (cm) Fagus sylvatica Fraxinus excelsior Tilia sp. Acer sp. Carpinus betulus Stand total DL ± 0.03 a 0.26 B ± 0.03 DL ± 0.17 a α 0.37 ± 0.07 a α 0.16 ± 0.08 a α 0.18 ± 0.07 a α 0.34 AB ± 0.07 DL ± 0.54 a α 0.35 ± 0.06 a α 0.63 ± 0.10 b α 0.48 ± 0.18 a α 0.64 ± 0.10 α 0.51 A ± 0.07

33 Summary (i) Productivity of the fine root system increases with increasing tree species diversity Fine root productivity increased from the pure to the mixed stands (sequential coring and ingrowth core approach)

34 Summary (ii) Resilience of the fine root system increases with increasing tree species diversity Resilience after disturbance increased from the pure to the mixed stands Fine root recovery was twice as fast in the mixed stands compared to the pure stands

35 Synopsis Influence of tree species diversity on below-ground processes

36 Synopsis Biomass No overyielding in the mixed stands 430 to 480 g m -2 Fine root distribution No vertical fine root segregation Strong fine root overlap High inter-competition processes No benefit of niche differentiation Nutrient availability Bulk density Clay No spatial niche differentiation No additional soil volume

37 Synopsis Resilience Fine roots recovered twice as fast in the mixed stands - Insurance hypothesis: mixtures recover more rapidly - Biodiversity effect? Soil ph & base saturation Fine root productivity Trend: productivity increased with increasing tree species diversity (sequential coring and ingrowth cores) Minirhizotron data Further investigation

38 Thank you Special thanks to: Prof. Christoph Leuschner Dietrich Hertel all participants of the Graduiertenkolleg and the Hainich National Park