Density Management in Pacific Northwest forests

Transcription

1 Density Management in Pacific Northwest forests

2 Should I thin? Is there an immediate cash flow or timber supply need? Do current and anticipated future stands meet management objectives (economic, wildlife, fire behavior, ecosystem services,... )? Current stand and implications for future dynamics Current dynamics (e.g., growth rate, mortality, value accretion) and implications for future stand Projected future stand Landscape/ownership-level goals Do individual-tree dimensions (e.g., crown and H:D ratios) and stand-level attributes (e.g., relative density) maintain future silvicultural options?

3 Should I thin? Could thinning be at least a partial solution? No Yes Logging damage Soil compaction Invasive species Are risks of possible adverse effects acceptable? No Yes Consider other options (e.g., regenerate, let grow, etc.) Consider thinning

4 Thinning Decision Points Intensity of thinning Residual density relative to initial density Reduction in SDI, SDIrel, RD, volume, basal area, tpa Type of thinning From below Proportional From above; crown thinning Selection thinning Free thinning Tree selection criteria Size Spatial position Species Form/defect

5 Thinning Decision Points Initial Stand SDI, SDI REL Crown ratio, H/D bf/ac size class dist n species composition How much? Residual stand density How to thin? What size classes? Thinning type d/d Target Stand SDI, SDI REL Crown ratio, H/D bf/ac size class dist n species composition What species? Residual composition Residual stand SDI, SDI REL bf/ac size class dist n species composition

6 Thinning to meet immediate cash flow need Determine revenue/ac or volume/ac objective If objective stated as revenue/ac then Estimate Average hauling costs per MBF Average logging costs per MBF Average mill price per MBF Compute implied revenue per MBF Revenue/MBF = mill price logging costs hauling costs Estimate MBF/ac required for revenue/ac target Thinning MBF/ac = [target revenue/ac] / [revenue per MBF] Choose thinning specifications Estimate size class distribution of removed trees and/or logs Estimate number and average dbh of removed trees Estimate thinning intensity Current and residual relative density, SDI rel or RD rel

7 Thinning to meet immediate cash flow need Reconsider revenue or volume objective if Reduction from current SDI rel would exceed 20% or Residual SDI rel would drop below 25% Verify costs and revenues for thinning specifications If necessary, adjust logging costs per MBF, based on size class distribution of removed trees If necessary, adjust delivered log price per MBF, based on size class distribution of removed trees If necessary, re-estimate MBF/ac required to meet revenue or volume target Reconsider revenue objective, volume objective, or type of thinning if Reduction from initial SDI rel would exceed 20% or Residual SDI rel would drop below 25%

8 Maximum SDI ~ % SDI rel ~ % SDI rel ~ % reduction in SDI rel

9 Thinning to meet immediate cash flow need Compute current volume, SDI and SDI rel Stand data Current SDI REL < 40%? NO YES Thinning not recommended Cash flow or timber volume objectives Estimate target volume to be removed Logging costs Hauling costs Log prices

10 Thinning to meet immediate cash flow need Estimate number and mean dbh of thinned trees Estimate residual SDI and residual SDI rel Residual SDI REL > 25%? NO Reconsider revenue or volume objective

11 Thinning to meet immediate cash flow need Residual SDI REL > 25%? Adjust objectives or thinning specifications YES NO Reduction in SDI REL 20%? YES Compute net revenue from specified thinning Cash flow target achievable? NO YES Reconsider revenue or volume objective Thin according to specifications

12 Thinning to meet immediate cash flow need Estimate target volume to be removed Estimate number and mean dbh of thinned trees Cash flow or timber volume objectives Logging costs Hauling costs Log prices Estimate residual SDI and residual SDI rel Adjust objectives or thinning specifications Residual SDI REL > 25%? NO Reconsider revenue or volume objective YES NO Reduction in SDI REL 20%? YES Compute net revenue from specified thinning Cash flow target achievable? NO YES Reconsider revenue or volume objective Thin according to specifications

13 Thinning to achieve target stand or sequence of target stands Definition of target stand structure Economic value Cash flow Optimal net present value (NPV) Desired tree size or log size distribution Costs and revenues Volume per ac Average log size Log prices Harvesting and hauling costs Multi-stand harvest schedule

14 Thinning to achieve target stand or sequence of target stands Definition of target stand structure (cont d) Wildlife habitat Late seral structure (size, density, spatial distribution) Vertical complexity (vertical spatial distribution) Horizontal structure (stand density, spatial variability) Overstory-understory links (production, species composition) Aesthetics Potential fire behavior Crown and canopy bulk density Tree/crown spacing Height to crown base Litterfall regime

15 Thinning to achieve target stand or sequence of target stands Definition of target stand structure (cont d) Hydrologic properties (interception, throughfall, stem flow, evapotranspiration) Canopy cover Leaf area index Crown mass and surface area Multi-objectives Stand silvicultural regime or Forest harvest schedule

16 Thinning to achieve target stand or sequence of target stands Assessment of current stand structure Stand density (SDI, SDI rel, RD, RD rel, basal area, tpa) Crown ratio Height:dbh ratio (inches:inches, ft:ft, cm:cm, m:m) Degree of differentiation Diameter distribution Height distribution/vertical stratification Species composition Relative abundance Vertical differentiation (stratification) by species Horizontal differentiation by species Assessment of current stand dynamics Net and gross growth (basal area, volume) Mortality rate Differentiation

17 Thinning to achieve target stand structure Residual stand Target stand Current stand Residual stand Target stand Residual stand Target stand Structure Log distribution Value Habitat

18 Alternative developmental pathways for managed stand NOW Stand age FUTURE

19 Alternative developmental pathways for managed stand TARGET CURRENT

20 Alternative developmental pathways for managed stand NO THINNING

21 Alternative developmental pathways for managed stand Possible routes to target stand Need to thin by start of 4 th growth period Can t get to target stand

22 Alternative developmental pathways for managed stand NO THINNING Need to thin by start of 2nd growth period TARGET

23 Assessing current stand dynamics as diagnostic criteria for thinning Stand data Compute growth components Gross growth Net growth Mortality

24 Assessing current stand dynamics as diagnostic criteria for thinning Net PAI < 800 bf/ac/yr? NO Mortality > 2% of gross PAI? NO Thinning not urgently needed YES YES Gross growth < 800 bf/ac/yr? NO Thin to recover mortality YES Thinning probably not a solution Parameters based on target stand structure: - Net growth expectation (800 bf/ac/yr) - Acceptable mortality rate (2%)

25 Thinning to maintain future options Stand data Compute diagnostic criteria SDI SDI REL Crown ratio H/D bf/ac

26 Thinning to maintain future options SDI REL > 65%? YES YES CR>25%? >20 yrs to end or of rotation? H/D<90? YES >5 MBF/ac if thin from below to 55% SDI rel? YES Thin from below to SDI rel =55% NO NO NO NO No thinning No thinning No thinning SDI REL > 55%? >15 yrs to end of rotation? YES CR>35%? or H/D<70? YES >5 MBF/ac if thin from below to 35% SDI rel? YES Thin from below or proportional to SDI rel =35% NO NO NO NO No thinning No thinning No thinning

27 Thinning to maintain future options YES SDI REL > 45%? Structural objective requires lower SDI rel? NO YES CR>35% or H/D<70? NO YES >5 MBF/ac if thin from below to 30% SDI rel? NO YES Thin from below or proportional to SDI rel =30% NO No thinning No thinning No thinning SDI REL > 35%? Structural objective requires lower SDI rel? YES CR>35% or H/D<70? YES >5 MBF/ac if thin from below to 25% SDI rel? YES Thin from below or proportional to SDI rel =25% NO Thinning not recommended NO No thinning NO No thinning NO No thinning

28 Thinning to meet complex objective Primary structural/aesthetic objective is to grow late seral structure out to 100 years. What general thinning strategy would provide the greatest economic return?

29 Management objective to grow late seral structure to 100 yrs Douglas-fir Levels-of-growing-stock Study Hoskins installation Established in 1963 in naturally regenerated stand 13 years breast height age, 20 yrs total age Site index 134 ft at 50 yrs

30 Trends in SDI over time on Hoskins LOGS plots: Eight different thinning regimes + unthinned control Marshall and Curtis 2002

31 Hoskins control plot in 1963, 80 crop trees per ac

32 Thinned plot 1969, control plot in background

33 Thinned plot 1969

34 Light thinning

35 Heavy thinning

36 1976 Heavy 1976thinning 1976 Light thinning

37 Simulate stand dynamics to age 100 Start with 1979 data from Treatment 5 36 years total age SDI 275, 53% of maximum (520) 193 tpa, 164 ft 2 /ac, 5344 ft 3 /ac 20.1 MBF/ac Top height 89 ft Mean crown ratio 40% Mean H/D 85 (59-133)

38 Initial diameter distribution Trees/ac TPA Dbh class midpoint (inches) DBH class midpoint (inches)

39 Trends in SDI over time on Hoskins LOGS plots: Eight different thinning regimes + unthinned control Marshall and Curtis 2002

40 Should I thin? Is there an immediate cash flow or timber supply need? Do current and anticipated future stands meet management objectives (economic, wildlife, fire behavior, ecosystem services,... )? Current stand and implications for future dynamics Current dynamics (e.g., growth rate, mortality, value accretion) and implications for future stand Projected future stand Landscape/ownership-level goals Do individual-tree dimensions (e.g., crown and H:D ratios) and stand-level attributes (e.g., relative density) maintain future silvicultural options?

41 Should I thin? Could thinning be at least a partial solution? No Yes Logging damage Soil compaction Invasive species Are risks of possible adverse effects acceptable? No Yes Consider other options (e.g., regenerate, let grow, etc.) Consider thinning

42 Three thinning regimes 1 Control: No thinning 2 One thinning: Proportional thinning to relative SDI of 35% at year 36 3 Three thinnings: Proportional thinning relative SDI of 35% at years 36, 56, and 76

43 What will thinning buy us? 1 Maintain tree/stand vigor to later ages 2 Acclerate growth of residual trees and approach to late seral structure 3 Provide some earlier cash return to improve net present value

44 Approaches? 1 Optimization if we can quantify the objective (objective function) and specify constraints (structural objectives) 2 Prescribe, simulate, assess; prescribe, simulate, assess. 3 Simulate a set of alternative regimes, then assess by diagnostic criteria

45 Three thinning regimes Stand Density Index No thinning 1 thinning 3 thinnings Stand age (yrs)

46 30 Control thinnings 1 thinning no thinning Trees/ac Dbh class midpoint (inches) Three thinnings

47 Simulate stand dynamics to age 100 Attribute Unthinned 3 thinnings SDI TPA Basal area Crown ratio H 40 Dq H 40 /Dq 434 (83%) % (42%) %

48 Scribner volume (bf) 140, , ,000 80,000 60,000 40,000 No thinning 1 thinning 3 thinnings 20, Stand age (yrs)

49 140, ,000 No thinning Standing Standing +mortality Scribner volume (bf) 100,000 80,000 60,000 40,000 20, Stand age (yrs)

50 Scribner volume (bf) 140, , ,000 80,000 60,000 40,000 One thinning Standing Standing+cut Standing+cut+mortality 20, Stand age (yrs)

51 Scribner volume (bf) 140, , ,000 80,000 60,000 40,000 Unthinned vs. one thinning Unthinned standing volume Thinned standing volume Thinned standing + cut volume 20, Stand age (yrs)

52 Scribner volume (bf) 140, , ,000 80,000 60,000 40,000 Standing live volume No thinning 1 thinning 3 thinnings 20, Stand age (yrs)

53 Control thinnings 1 thinning no thinning Trees/ac Dbh class midpoint (inches) Three thinnings

54 350 Logs/ac no thinning 1 thinning 3 thinnings Control Scaling diameter class midpoint (inches) Three thinnings

55 Thinning costs and revenues Net present value of three stand density regimes Interest rate 0.06 Cost/revenue Year Log price ($/MBF) Clearcut logging cost, cable ($/MBF) Thinning logging cost, cable ($/MBF) Clearcut logging cost, ground ($/MBF) Thinning logging cost, ground ($/MBF) Hauling cost ($/MBF)

56 Fixed logging costs and log prices

57 Fixed logging costs and increasing log prices

58 Declining logging costs / increasing log prices

59 Earlier Hoskins LOGS plots Start with 1966 data from Treatment 5 23 years total age SDI 186, 36% of maximum (520) 365 tpa, 86 ft 2 /ac, 1468 ft 3 /ac 1.5 MBF/ac Top height 49 ft Mean crown ratio 76% Mean H/D 80 (54-80)

60 Thinning to meet complex objective Primary objective is to maximize revenue from growing timber. What is the optimal thinning regime, or should you thin at all?

61 Initial diameter distribution Trees/ac TPA Dbh class midpoint (inches) DBH class midpoint (inches)

62 Maximum SDI ~ % SDI rel ~ % SDI rel ~ yrs in yrs in 1966

63 No thinning after calibration thinning in No thinning after thinning 3 thinnings No thinning after 1966 Stand Density Index Stand age (yrs)

64 No thinning after calibration thinning in ,000 Scribner volume (bf) 120, ,000 80,000 60,000 40,000 No thinning after thinning 3 thinnings No thinning after , Stand age (yrs)

65 Thinning to meet complex objective What approach would you use to identify the optimal thinning regime, or for deciding whether thinning pays?

66 Thinning to meet complex objective Assume you have YOUR optimal thinning regime identified. Would you monitor stand development? If so, what would your monitoring plan look like?

67 Stand density and fuel accumulation Could you design a stand density regime to control fuel accumulation? To what degree does stand density regime control fuel accumulation?

68 Stand density and fuel accumulation Ponderosa pine spacing trials Lookout Mountain 6-, 12-, and 18-ft initial spacings Start with plantation at 13 years total age Simulate stand development for 100 years

69 Average diameter of dead branches (cm) Three initial spacings Dead branch diameter (cm) ft 12-ft 18-ft Stand age (years)

70 Branch mortality (number/ha/yr) Three initial spacings Periodic annual branch mortality (no ha -1 yr -1 ) ft 12-ft 18-ft Lookout Mountain Stand age (years)

71 Branch mortality (necromass/ha/yr) Three initial spacings Periodic annual branch mortality (kg ha -1 yr -1 ) ft 12-ft 18-ft Stand age (years)

72 Site effects on branch mortality (necromass/ha/yr) Periodic annual branch mortality (kg ha -1 yr -1 ) ft 12-ft 18-ft Lookout Mountain Pringle Butte Site index 55 vs. 85 at 50 yrs Stand age (years)

73 Black Rock Plot 31 Crop tree thinning Stand history Naturally regenerated after logging near turn of the century 48 years total age in 1957 Thinned in 1957 from 294 to 51 trees/ac Underplanted in 1959 with western hemlock at 6-ft spacing

74 Black Rock Plot 31 Crop tree thinning Initial stand attributes 48 years total age in 1957 SDI 389, 75% of maximum (520) 294 tpa, 229 ft2/ac, 10,346 ft3/ac 39.2 MBF/ac

75 Black Rock Thinning Trials Black Rock thinning plots (rep 2), heavy thinning medium thinning light thinning control Tpa cont rol heavy t hinning Dbh class midpoint (in)

76 Black Rock Thinning Trials Black Rock thinning plots (rep 2), crop52 crop42 control Tpa Dbh midpoint (in) crop52

77 Black Rock Thinning Trials Black Rock thinning plots (rep 2), Tpa 35 Tpa or basal area (ft 2 /ac) Basal area Dq Dq (in) control light medium heavy crop Treatment

78 Black Rock Thinning Trials Black Rock thinning plots (rep 2), net PAI for Cubic Scribner PAI as % of control ft3/ac/ bf/ac/ yr yr control light medium heavy crop Treatment -41

79 Black Rock Thinning Trials Black Rock thinning plots (rep 2), mortality thinned standing Cubic volume (ft 3 /ac) control light medium heavy crop Treatment

80 Black Rock Thinning Trials Black Rock thinning plots (rep 2), crop tree control Tpa Dbh midpoint (in) crop tree

81 Black Rock Thinning Trials Overstory SDI 274 (53% of 520) Understory SDI 35 (4% of 850)

82 Tree growth Carrying capacity Microclimate Physiology Summary Understory response to thinning Thinning Understory vegetation is happy to use resources that are not captured by trees!

83 Crop tree thinning & hemlock understory, 1985

84 Black Rock Thinning Trials 1985 Crop tree thinning Hemlock understory

85 Black Rock Thinning Trials