Tree diversity - forest resistance relationships

Tree diversity - forest resistance relationships Herve Jactel, Johanna Boberg, Damien Bonal, Bastien Castagneyrol, Barry Gardiner, José-Ramon Gonzalez, Julia Koricheva, Nicolas Meurisse, Eckehard Brockerhoff To cite this version: Herve Jactel, Johanna Boberg, Damien Bonal, Bastien Castagneyrol, Barry Gardiner, et al.. Tree diversity - forest resistance relationships. EuMIXFOR Final Conference, Oct 2016, Prague, Czech Republic. 30 p. ฀hal-02795518฀ HAL Id: hal-02795518 https://hal.inrae.fr/hal-02795518 Submitted on 5 Jun 2020 HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Tree diversity - forest resistance relationships http://www.waldwissen.net Hervé Jactel, Johanna Boberg , Damien Bonal, Bastien Castagneyrol, Barry Gardiner, José-Ramon Gonzalez, Julia Koricheva, Nicolas Meurisse, Eckehard Brockerhoff An urgent need for more productive planted forests 1. to meet the social demand for wood products including energy wood 2. to contribute to climate change mitigation through carbon sequestration 3. to alleviate the logging pressure on natural forests and preserve biodiversity Mixed forests are likely more productive But are mixed forests more prone to damage ? 1. Rising threats due to climate change ↗ temperatures trigger pest outbreaks and range expansion Mountain pine beetle 2011 2006 1979 Pine processionary moth But are mixed forests more prone to damage ? 1. Rising threats due to climate change ↗ droughts increase the risk of forest fires ↗ droughts increase tree susceptibility to infection But are mixed forests more prone to damage ? 1. Rising threats due to climate change ↗ wind damage But are mixed forests more prone to damage ? 2. Rising threats due to global change Number new specie ecies / year ↗ globalization results in more biological invasions Exotic arthropods Dryocosmus kuriphilus Origine: China But are mixed forests more prone to damage ? Diversity – resistance relationships in grasslands Resistance of mixed forests to 7 natural disturbances 1. 2. 3. 4. 5. 6. 7. Drought Fire Windstorm Mammal herbivores Pest insects Fungal pathogens Invasive species William M. Ciesla, Forest Health Management International, Bugwood.org 1. Patterns of response to tree diversity 2. Underlying ecological mechanisms http://www.redbubble.com/people/bberwyn Concept of Associational Resistance AR = greater resistance of plants against herbivores when surrounded by heterospecific neighbors as compared to plants growing among conspecifics The opposite pattern is associational susceptibility (AS) Associational resistance = emergent property of assemblages of different tree (plant) species resulting in lesser damage by natural disturbances at the stand level 1. Associational resistance to drought http://dnr.wi.gov/ Idiosyncratic responses Limiting factors (temperature, fertility) Water Use Efficiency = Productivity / Transpiration 2. Associational resistance to fires Light Severe http://www.sierraforestlegacy.org Several cases of AR Mainly in boreal forests 3. Associational resistance to windstorms Consistent AR http://iireporter.com 4. Associational resistance to mammal herbivores Contrasting effects on mammal herbivores 5. Associational resistance to pest insects 119 case studies, 33 tree species 200% 36 % less damage in mixed forests (80% cases) 150% 100% 50% 0% -50% -100% -150% Significant AR -31% 6. Associational resistance to fungal pathogens Overall better resistance of mixed forests to root rot fungi Resistance or neutral effects for foliar pathogens Mean % defoliation ion per plot 7. Associational resistance to invasive species Theoretical Rarely studied Tree species richness Associational resistance in mixed forests: common features 1. Direction and magnitude of AR depend on spatial extent and/or selectivity of natural disturbances Associational resistance in mixed forests: common features 1. Direction and magnitude of AR depend on spatial extent and/or selectivity of natural disturbances - 42% - 15% 0% Castagneyrol et al. 2014 Associational resistance in mixed forests: common features 2. Forest composition more important than tree species richness % pets damage reduction on conifer conifer broadl. broadl. broadl. conifer conifer broadl. 0% -10% -20% – 27% – 45% -30% -40% -50% -60% Jactel & Brockerhoff 2007 Mechanisms underlying diversity – resistance relationships 0. The insurance hypothesis Being composed of several species with different functional traits, mixed forests have a higher likelihood of containing resistant trees, thus providing more opportunities to maintain a forest cover and sustain basic ecosystem functions on the long term = risk spreading Mechanisms underlying diversity – resistance relationships 1. Complementarity of resistance traits - Root depth / drought - Bark anatomy, branching pattern / fire - Crown architecture / wind - Leaf quality / herbivores - Niche occupancy / invasive species Mechanisms underlying diversity – resistance relationships 2. Depletion of resources to feed or fuel - lower amount of resources to fuel fire or contribute to windthrow - lower amount of resource to feed mammals or insect herbivores Mechanisms underlying diversity – resistance relationships 2. Disruption / diversion of host finding Tree mortality due to A. ostoyae oyae in mixed stands - increasing spacing between target trees Gerlach et al. 1997 Mechanisms underlying diversity – resistance relationships 3. Disruption / diversion of host finding - physical protection by neighbors - diversion (decoy) processes Saplings planted under Eglantine Browsing frequency Spruce - Fir Beech - Maple Mechanisms underlying diversity – resistance relationships 4. Reinforced biotic interactions: symbiosis, predation - decomposers and mycorrhiza (drought, wind) - natural enemies (pest insects, pathogens) Neodiprion sertifer 100% Scots pine 50% Scots pine – 50% Birch Mechanisms underlying diversity – resistance relationships Mechanisms underlying diversity – resistance relationships Elementary resource Conclusions • Mixed forests : associational resistance > susceptibility • Tree composition > species richness • 3 biodiversity dimensions: “resource” heterogeneity, amount, connectivity • 4 main processes involved: complementarity, depletion, disruption, biotic interactions • Tradeoffs for resistance to different disturbances? • Compromises with mixed forest productivity Composition Spatial pattern Thank you for your attention http://mixedwoodecozone.weebly.com/natural-vegetation.html