Silviculture in a Changing World: Reflections From Recent Disturbances in British Columbia, Canada

Transcription

1 Silviculture in a Changing World: Reflections From Recent Disturbances in British Columbia, Canada Dave Coates Research Silviculturist British Columbia Forest Service Smithers, BC Canada dave.coates@gov.bc.ca 1

2 Smithers British Columbi a Vancouver

3 Forests of British Columbia Insect/disease disturbances in BC appear to be following some of the more dire projections of the influence of climate change on forest dynamics Mountain pine beetle (MPB, Dendroctonus ponderosae) Dothistroma needle blight (Dothistroma septosporum) Hard pine rusts All are native pests on native host species

4 Mountain Pine Beetle Infestation of >175,000 km 2 of conifer forest in British Columbia Dendroctonus ponderosae Has released ~270 MtC (Kurz et al Nature 452: )

5 Affected area about 1/2 size of Norway Forests Especially but also economies and communities Global change with numerous direct and indirect impacts Increased variability Uncertainty is the rule rather than the exception Foresters must strive to maintain open as many options as possible Since 1910: Management emphasis on resilience, Average adaptability winter temp and increase productivity of ºC Area of mature lodgepole pine (>80 yr) has tripled

6 Operable Land Base is 22 million hectares 9.5 million ha attacked by MPB 5.6 million ha >70% pine About 726 million cubic metres of pine killed Photo Alex Woods

7 Which stands should be priority for salvage? Is salvage and plant always a good strategy? Should reforestation strategies be the same as the past? What happens to the unsalvaged stands? Do strategic directions matter? Photo Alex Woods

8 Stocking highly variable: thousand ha very poorly stocked 2-3 million ha marginal stocking Yield implications, employment, community stability, government revenue?

9 The MPB epidemic is the most significant forest management challenge BC has ever faced Have salvaged logged <1 million ha

10 Strategies to Sustain the Forest Economy Salvage logging for < 15 years Plantations may be ready in years Big problems from years In many stands, saplings of interior spruce and subalpine fir survive as advance regeneration. Could these produce new spruce/fir stands that would fill the gap?

11 Merchantable volume (m 3 ha -1 ) stems 1360 stems 3300 stems 1200 (Bl) 1200 Sx plantation Year

12 The Feisty Fungus: Dothistroma Needle Blight Epidemic and Climate Change

13 Foliar Disease Fungi May be some of the more responsive forest disease organisms to climate change Ability to sporulate and infect strongly tied to temperature and precipitation Dothistroma needle blight (Dothistroma septosporum) is a major pest of pines gained prominence as pest of Pinus radiata plantations in southern hemisphere

14 Severely damaged lodgepole pine plantation

15 Dothistroma & Mean Summer Precipitation Smithers 37,000 ha infected M S P 15 Woods et al 2005

16 1. Strong evidence of a climate change/pathogen linkage. 2. Spread has been favoured by widespread plantations of host tree. 3. Type of climate change observed would be typically viewed as favourable for the host tree. 4. Illustrates the unpredictable nature of the influence of climate change on forest ecosystems. See for details: Woods, Coates & Hamann Is an unprecedented Dothistroma Needle blight epidemic related to climate change? BioScience 55(9):

17 Smithers

18 Foliar diseases are not the only forest pathogens that are increasing in both prevalence and significance in Central BC Hard pine rusts are too, including: Western gall rust (Endocronartium harknessii) Comandra blister rust (Cronartium comandrae), and Stalactiform blister rust (Cronartium coleosporoides) Photo: E. Havard 18

19 Percent Morice TSA, combined mean rust incidence by stand and percent of stands with >20% incidence in 1996 (n=66), 1999 (n=98) and 2008 (n=82) 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% Combined Rust Incidence % stands > 20% 7.1% 7.6% 7.1% 6.2% 41.5% 18.6%

20 What has been Learned? Climate change can reduce natural checks and balances can make trees more vulnerable to insect/pathogen disturbances previously limited by unfavourable climate Prior management can make things worse Dothistroma, MPB, rusts Many of our yr old plantations are not performing as expected all sorts of potentially climate related stuff Strategic responses do matter (MPB) Lodgepole pine has become a major restoration liability all over the place what might be next?

21 We Need to Think Differently The notions of homogeneity and stability as a basis for management presents many risks that should no longer be ignored. Forests are composed of many parts and processes that interact with each other and with the external environment over multiple spatial and temporal scales. These interactions can be circular, non-linear or exhibit threshold behaviour Forests can and will self-organize. Dynamic change and not stable equilibria are the rule. Changes will be neither completely random nor entirely deterministic. 21

22 Moving Forward Viewing forests as complex systems is the logical next step in our changing view of forest dynamics and the evolution of silvicultural practices. Adaptability and self-organization are good concepts for managing forests as complex systems we want our managed stands to adapt or self-organize after unexpected disturbances or changes and to continue to provide desired goods and services. Adaptability and self-organization can be general criteria for evaluating the success of policy goals and silvicultural practices See for details: Puettmann, Coates & Messier A Critique of Silviculture: Managing for Complexity. Island Press, Washington DC.. 22

23 Important Consideration Biological systems with their ability to adapt, selforganize, and change over time are different from physical and chemical systems Biological systems show ecological features Diversity Cross-scale interactions Memory Environmental variability These issues challenge classical complex systems science and are not yet fully resolved in ecology and silviculture See Anand et al. 2010, Diversity, 2: for a more in depth discussion 23

24 New Realities An era of new climates Unexpected disturbances Changing abiotic conditions Multiple threats to productivity Economic and social change how to value forests? We must start incorporating aspects of variability and uncertainty into decisions We should consider developing novel ecosystems

25 Forest Management Must Change More is required than simply choosing or modifying traditional tools or choosing different silvicultural systems. Will require new: Viewpoints (need to think differently) Decision criteria (different temporal and spatial scales) Practices (designed to influence adaptive capacity over the long-term, e.g., functional traits, diversity, interactions) Models (uncertainty, non-linear responses) Silvicultural practices must increase ecosystem adaptability and promote desirable outcomes 25

26 Go to Pretty Places

27 My Experiences Ecological classification program - wow, learned so much, still effects my thinking Clearcuts about 10 years, all about plantation management Retention issues - more to forest ecology/management than planting trees Stand dynamics - out of clearcuts into the forest = partial cutting, species interactions, complex stands Mountain pine beetle depression, new insights, how to strategically manage, still big issues Forests as complex systems perplexing, mind bending, tremendous potential to improve practice