Adapting forests to climate change: lessons learned from mixed forests

Transcription

1 Adapting forests to climate change: lessons learned from mixed forests th October, 2016 Prague, 5 Christian Ammer Christian Ammer Abteilung Waldbau und Waldökologie der gemäßigten Zonen

2 Conclusions first! 2/21

3 Conclusions Mixed stands are a reasonable option for adaptation of forests to climate change Mixed stands composed of species with different functional traits and different foraging strategies increase the likelihood of complementary effects because of reduced intraspecific competition pressure Aside from competition release facilitation plays an additional role Because the functional traits of the species involved are of crucial importance, species identity seems to be more important than species diversity Belowground resource availability seems to modify species specific responses to interspecific neighborhoods 22/24 3/21

4 Forest Adaptation Adaptive forest management aims at preserving and developing the functionality of forests as a prerequisite for ensuring the full range of potential future forest ecosystem services (Wagner 2004) Adaptation of forests to climate change implies strategies and measures which either improve the resistance or the resilience of existing or future forests (Joyce et al. 2009, Keskitalo 2011, Keenan 2015). Wagner (2004) Forst und Holz 59: Joyce et al. (2009) Environmental Management 44: Keskitalo (2011) Forests 2: Keenan (2015) Annals of Forest Science 72: /24 4/21

5 What I am going to talk about (1) What makes mixtures interesting for adaptation? (2) What was found? Some examples (3) Explanations and principles 5/21

6 (1) What makes mixtures interesting for adaptation? Intraspecific competition Facilitation Interspecific competition Facilitation 6/21

7 (1) What makes mixtures interesting for adaptation? Release from competition by: different strategies (e. g. rooting pattern) of water acquisition, different stomatal response to water shortage (demand), different rooting plasticity and belowground competiveness. Facilitation (indirect and direct) by: higher canopy throughfall changed throughfall distribution (e.g. stemflow) temporal dissimilarities of the species water use hydraulic lift by one species which may improve the water availability of another species Forrester (2015) Tree physiology 35: /21

8 (1) What makes mixtures interesting for adaptation? If resulting in higher restistance, recorvery, resilience against drought Irrespective of absolute consumption 8/21

9 (1) What makes mixtures interesting for adaptation? Basic hypothesis The more mixed stands are composed of species with contrasting functional traits the better they perform in periods of severe droughts. Redundancy in functional traits may even lead to more stressful conditions 9/21

10 (2) What was found? Grossiord et al. (2014) PNAS 111: No or positive mixing effects on drought tolerance Hemi-boreal, mountainous beech and Mediterranean forests may be composed of species with similar competitive strategies 10/21

11 Mean daily sap flux density (2) What was found? Grossiord et al. (2014) Forest Ecology and Management 318: Q. cerris Q. petraea No mixing effect on Q. petraea but negative effects on Q. cerris Higher foliar δ 13 C values for Q. cerris consistent with lower transpiration in mixture with Q. petraea June July August Sept 11/21

12 (2) What was found? Pretzsch et al. (2013) Plant Biology 15: Lloret et al. (2011) beech profits from the mixture but not at the expense of oak deep-rooting oak facilitates the much more shallow-rooting beech through hydraulic lift of water 12/21

13 (2) What was found? Metz et al. (2016) Global Change Biology 22: Beech surrounded by: Beech other hardwoods Norway spruce Scots pine 13/21

14 d 13 C d 13 C d 13 C d 13 C Pure beech d 13 C d 13 C Mixture beech/hardwoods Mixture beech/scots pine Mixture beech/spruce In both dry pointer years (1976 and 2003) beech in mixed stands experienced lower drought stress, indicated by lower δ 13 C values 19/33 14/21

15 Metz et al. (2016) Global Change Biol. 22: The beneficial effect of interspecific neighborhood on beech is closely related to competition. Release from competition rather than neighborhood diversity seems to increase tolerance to drought 15/21

16 Interestingly mixture does not change the inter-annual growth pattern of beech 16/21

17 but results in a constantly higher yield per day Prague /21 Abteilung Waldbau und Waldökologie der gemäßigten Zonen Pretzsch and Biber (2005) Forest Science 51:

18 (2) What was found? Lebourgeois et al. (2013) Forest Ecology and Management 303: Abteilung Waldbau und Waldökologie der gemäßigten Zonen radial growth variation (RGV%) negative value: current year ring is narrower than the previous one Negative values more frequent in dry environments in pure Abies alba stands Mixture with beech more beneficial than mixture with spruce Less clear picture on better sites Facilitative processes between A. alba and other species increase when resources are limited facilitative processes are expected to increase for species with different growth patterns and ecological demands

19 (3) Explanations and principles Evidence for the stress-gradient hypothesis: facilitation will increase, and competition decrease, with increasing ecological mostly edaphic constraints and hence harsher environmental conditions (Bertness and Callaway 1994) But the SGH may be refined according to Maestre et al. (2009) by taking the competitiveness of the species into account Bertness M, Callaway RM (1994) Trends in Ecology and Evolution 9: Maestre et al. (2009) Journal of Ecology 97: /21

20 (3) Explanations and principles Species A Stress tolerant, less competitive Stress tolerant, less competitive Competitive Species B Stress tolerant, less competitive Competitive Competitive 20/21

21 Depending on species and site the establishment of mixed stands seems to be a reasonable option to adapt forests to climate change. Beside controlling stand density species composition is one of the few management options for forest adaptation to climate change BUT: Adaptation measures alone will not prevent forests from detrimental impacts of climate change. There is an urgent need for combating the anthropogenic causes of climate change. Further reading: Ammer (2016) Progress in Botany, 78, DOI /124_2016_14 21/21

22 Thank you for listening Abteilung Waldbau und Waldökologie der gemäßigten Zonen

23 carbon isotope composition in C3 plant tissues reflect the ratio of intercellular to atmospheric CO 2 concentrations during the period when the carbon was fixed (discrimination against 13 C) water stress causes an increase of 13 C/ 12 C ratio 13 C / 12 C sample - 1 [ ] 13 C / 12 C standard d 13 C = ( ) x 1000 δ 13 C in plant material: typically around the higher δ 13 C the higher the 13 C concentration, recording higher drought stress Abteilung Waldbau und Waldökologie der gemäßigten Zonen

24 Finér et al. (2007) Plant Biosystems 141: /35 Abteilung Waldbau und Waldökologie der gemäßigten Zonen

25 Trait.Acer pseudoplatanus..fagus sylvatica..picea abies..pinus sylvestris. Fruit 2 type Leaf area Leaf area per leaf dry mass (specific leaf area, SLA) Leaf area per plant dry mass (leaf area ratio; LAR) Leaf carbon (C) content per leaf dry mass Leaf carbon/nitrogen (C/N) ratio Leaf distribution along the shoot axis (arrangement type) Leaf dry mass Leaf dry mass per leaf fresh mass (Leaf dry matter content, LDMC) Leaf dry mass per plant dry mass (leaf weight ratio, LWR) Leaf intercellular CO2 concentration Leaf isoprene emission category Leaf isoprene emission rate per leaf area Leaf isoprene emission rate per leaf dry mass Leaf lamina length Leaf lifespan (longevity) Leaf nitrogen (N) content per leaf area Leaf nitrogen (N) content per leaf dry mass Leaf nitrogen/phosphorus (N/P) ratio Leaf palatability Leaf phosphorus (P) content per leaf dry mass Leaf photosynthesis carboxylation capacity (Vcmax) per leaf area (Farquhar model) Leaf photosynthesis electron transport capacity (Jmax) per leaf area (Farquhar model) Leaf photosynthesis rate per leaf area Leaf photosynthesis rate per leaf dry mass Leaf thickness Leaf type Litter decomposition rate Litter nitrogen (N) content per litter dry mass Photosynthetic pathway Plant functional type Plant growth form Plant growth rate Plant height Plant lifespan (longevity) Plant light requirement Plant mycorrhizal type Plant relative growth rate (RGR) Plant shoot branching Plant tolerance to CaCO Plant tolerance to drought Plant tolerance to fire Plant tolerance to frost Plant tolerance to shade Plant tolerance to temperature Plant tolerance to waterlogging Plant woodiness Seed dry mass Seed germinability group Seed number per reproducton unit Stem conduit diameter (vessels, tracheids) Stem diameter Stem dry mass per stem fresh volume (stem specific density, SSD, wood density) Stem fraction of cell wall in collenchym Stomata conductance per leaf area Stomata density Leaf photosynthesis carboxylation capacity (Vcmax) per leaf dry mass (Farquhar model) Stem carbon (C) content per stem dry mass /35 Abteilung Waldbau und Waldökologie der gemäßigten Zonen

26 (1) Was ist das Problem von Wildverbiss? 6/35 Abteilung Waldbau und Waldökologie der gemäßigten Zonen

27 (1) Was ist das Problem von Wildverbiss? 6/35 Abteilung Waldbau und Waldökologie der gemäßigten Zonen