Silviculture and Management of Complex Forests

Transcription

1 Silviculture and Management of Complex Forests Dave Coates Research Silviculturist British Columbia Forest Service, Smithers, BC

2 Significant Contributions Klaus Puettmann Oregon State University, Corvallis, Oregon Christian Messier Université du Québec à Montréal, Montréal, Québec Phil Burton Canadian Forest Service, Prince George, BC Many others. SORTIE and SORTIE-ND trials and tribulations working with a simulation model

3 Ecosystems Complex systems Economies Relationships are non-linear Relationships contain feedback loops Are open Have a memory change over time, prior state may affect current Boundaries are difficult to determine May be nested components of a complex system may be themselves a complex system Modularity and heterogeneity emerge and play crucial roles in mediating robustness/resilience Produce emergent phenomena i.e., unpredictable things can and will happen Climate Transportation Networks

4 More on Complexity How complexity arises from local interactions is a major area of current ecological research the biodiversity-function debate is part of this Complexity in ecological systems the interplay among processes at diverse scales of space, time and complexity (S.A. Levin 2005) The concept of scale is critical in complex systems different components and structures are evident only at different spatial and temporal resolutions

5 A Little More on Complexity (Simon Levin 2005 BioScience,, ) 1079) The big question How are ecosystems and the biosphere organized? It is the domain of science to explain how such complexity can arise from local interactions, and research into complex adaptive systems is one of the most exciting and active areas of research.

6 Forestry and Silviculture Philosophically based on developments in central Europe about 140 yrs ago Forestry is struggling to adapt to changing knowledge to meet public perceptions and demands

7 Silviculture Focus is on tree or tree-related related issues: reproduction methods genetics growth and yield prediction development of planting, tending and harvesting techniques

8 Dominant Research Approach Use of frequentist statistics (Fisher) and designed experiments (e.g., randomized block design) Agricultural model of research few treatment factors limited set of treatment levels uniform sample plots plot designs that average across variation control of stochastic factors null hypothesis testing Effective when management objectives are clear and single-issue issue focused (optimize growth and volume)

9 Implications for Forest Management Ingrained belief in a best treatment site preparation method, species, stock type, planting density, vegetation control, thinning regime Applying this best treatment at the stand-scale scale is good management These values have driven silviculture

10 Stand Scale Management An emphasis on reducing natural bounds of variation Limited set of practices employed Practices designed to promote uniform conditions Stand averages are the measure of success Need for accurate growth prediction has promoted uniformity

11 Implications of Adopting the Agricultural Model Emphasis on reducing natural bounds of variation in stand-level responses Silviculture foresters find it difficult to embrace and manage for complexity

12 Patch Clearcutting - Interior BC

13

14 Pine Plantation - Burns Lake, BC

15 Traditional Uneven-aged Management Complexity? Promotes uniform stands in a different way Still relies on stand averages The normal forest in a single stand

16 Traditional Silviculture Promotes Uniformity Traditional silvicultural systems (clearcut, shelterwood,, seed-tree, group and single-tree selection) do not acknowledge complexity. Result in structurally simple forests in space and time. This can have serious implications for ecosystem resilience and productivity.

17 Fennoscandian Silviculture last 100 yrs Intensive plantation silviculture control of species composition, stocking density, age class structure. Minimal losses to natural disturbance agents. Rigorous elimination of dead and dying trees.

18

19

20 Implications Success for wood production. High cost to indigenous biological diversity species threatened in Sweden. Organisms associated with dead wood especially susceptible.

21 Is Silviculture Stuck in a Rut? (Do we need to change?) Emphasis on limited set of tree species Data collected from uniform stands Plot averages rule Models capable of predicting only a limited set of treatment options The past is the future

22 The Risk of Simplicity Spruce leader weevil in the Kitimat Valley Porcupine damage in coastal plantations Tomentosus root rot and spruce Low density pine plantations and rusts Root collar weevil in pine after MPB kills adjacent plantations Are our most intensively managed pine stands getting hit harder by the beetle? Dothistroma needle blight in the interior cedar-hemlock zone

23 Developments in Last 15 Years Movement Away From Traditional Clearcutting Patch or variable retention to meet habitat and ecological objectives (5-20% retention) Slightly more complex stand structures Mixed-species plantations more common, but pine dominated stands usually planted back to pine

24 What is Retention? Prescribes what is to be left behind A means to retain important mature forest characteristics or structure Not selection cutting one entry, objective is complex structure Not a traditional silvicultural system

25 Retention Debate Strongly influenced by coastal thinking to the determent of practice in the interior other parts of Canada or boreal Europe more relevant Interior foresters tend to focus on importance of retention for habitat and non-timber values Strong thread on processes in complexity literature nutrient cycling, insect and pathogen dynamics Complex forests have greater ecosystem resilience less risk of damage to trees

26 Basic Complex Silviculture Develop approaches that preserve important forest structure in space and time safely. Strive for minimal impacts on allowable cut and operational complexity/cost. Be flexible and innovative. Results in complexity of species/structures in space and time.

27

28

29

30

31 Silviculture and Complexity Fine-scale spatial interactions regulate the demography of component tree species Spatial distribution of trees regulate variation in ecosystem properties Increased recognition that variable structure is desirable within stands Silviculture needs to evolve into management of critical neighbourhood processes Need to think in terms of gradients and trade- offs, not a best treatment

32 Plug for New Methods for Analysis of Field Data Various statistical techniques can be applied, for example model selection: analysis based on maximum likelihood methods and information theory provides required flexibility for prediction of important processes functional forms motivated by hypotheses about underlying mechanisms quantify factor of interest in terms of spatial distribution of neighbouring trees, resource availability and environmental conditions Suggested reading: Johnson and Omland 2004 TRENDS in Ecology & Evolution

33 Pros and Cons of Model Selection Classic null hypothesis testing replaced by model selection and comparison Forces researcher to focus clearly on underlying models being compared and statistical properties of data Has few of the restrictive assumptions required of parametric statistics Results are conditioned by scope of models under consideration Effectiveness of approach depends on insight of investigator and collection of appropriate data

34 Stands are Multiple Neighbourhoods Spatial and environmental heterogeneity exists within stands highly desirable from an ecosystem perspective Spatial scale of effective neighbourhood varies with property or process light environment tree recruitment, growth, mortality below ground processes

35 Road Map - Managing For Complexity Acknowledge variability within and among stands determine proper spatial scale for important processes and functions Loose Loose belief in a best treatment Eliminate Eliminate stand average focus

36 Road Map - Managing For Complexity Define desired future conditions at multiple scales and dimensions legacies natural disturbance biodiversity/habitat growth and yield Acknowledge risk and uncertainties promote resiliency manage expectations

37 Road Map - Managing For Complexity Adopt Adopt new statistical techniques and link empirical studies to modeling capture important demographic processes space matters in forests, especially complex forests Quantify responses across gradients and as gradients change explicitly consider trade-offs variability is a fact of life; seek biologically realistic incorporation of error terms and uncertainty into predictions

38 One Last Plug Forestry has been grounded in an agricultural model that believes in a single best treatment simple structured plantations with assumption of increased yields compared to unmanaged stands high risk Need to think in terms of gradients and trade-offs, not a best treatment Mixed species silviculture to reduce risk strive for complex spatial and temporal structure intimately mixed plantations of multiple species promote natural regeneration of all native species