The Influence of Stand Density on Mortality in California s Forests

Transcription

1 The Influence of Stand Density on Mortality in California s Forests An Analysis of Inventory Data Michael Landram Regional Silviculturist, USDA Forest Service, R-5

2 Contributors and Collaborators Ralph Warbington and The Crew at the Remote Sensing Lab FS Research, FIA Staff Julie Lydick, Health Protection Staff Paul Dunham, FHP, Portland Debbie Beardsley, FIA Contractor David Larsen, U. of Missouri FHP Zone Entomologists/Pathologists Duane Nelson and Joe Sherlock

3 Disclaimer This is work in progress. It needs error checking, validation, and peer review. If I don t ask you to use it with caution at your own risk, SHAME ON ME! If you use it at your own risk without considering this disclaimer, SHAME ON YOU!

4 This is density colorized image

5 This is mortality

6 This is one result Questions?

7 In Conclusion This Analysis Suggests Maximum Stand Density Index (Max SDI) depends on sample size used to derive it. Max SDI truly is independent of site quality variables. Mortality is positively correlated with SDI.

8 In Conclusion This Analysis Suggests Mortality/SDI are correlated along a linear gradient. There are no threshold points where mortality dramatically increases. Thinning to a residual density of SDI 200 is not a bad practice in any conifer type on any site if you want to keep the probability of mortality around 20%.

9 Characteristics of the Inventory Grid of cluster plot samples on all ownerships in the State. Data collected mostly in 1990 s. Inventoried dead trees were recently dead (last 5 to 10 years) at time of sample. The scale of sample used in this analysis is the sample point scale, rather than the traditional cluster plot scale over 23,000 points of data.

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11 Variation Between Sample Points

12 Characteristics of the Inventory In general (some variation in design), the 23,000 points were sampled as nested plots Trees < 5 dbh were sampled on 1/100 th acre plots. Trees >5 dbh were sampled on variable radius plots using various basal area factor prisms/angle gauges.

13 Characteristics of the Inventory The inventory reflects genetic and environmental conditions in the forests at time of sampling, including Natural disturbances in place at the time. Harvests that had taken place. Climate patterns in place at the time.

14 Most of California is in a 6 Year Drought

15 So given those characteristics and caveats. What can we learn from the inventory we have?

16 Potential Measures of Density Canopy cover (hard to measure) Trees per acre (says nothing about size) Basal area (cross sectional area) Stand Density Index (we ll use this one; better measure of competition)

17 Stand Density Index Formula SDI = Trees per acre* ( Diameter /10)

18 SDI graphed on regular scale 80 Pure (80%+ by BA) Ponderosa Pine 2,011 sample points Mean Diameter Trees Per Acre

19 Logarithmic scale Logarithmic Scale 100 Mean Diameter Trees Per Acre

20 Scatter Diagram of Pure Ponderosa Points Pure (80%+ by BA) ponderosa pine 2,011 sample points Mean Diameter Trees Per Acre

21 Definition of Maximum Stand Density Index (Max SDI) For this presentation, Max SDI is defined as the 99 th percentile for a given data set

22 Does Max SDI vary by species? YES

23 Caliornia red fir vs. Douglas-fir vs. California black oak 3 Species highest 100 sample points each 100 RED - CALIFORNIA RED FIR GREEN - DOUGLAS-FIR BLACK - CALIFORNIA BLACK OAK Mean Diameter Trees Per Acre

24 Max SDI Lines 3 Species highest 100 sample points each RED - CALIFORNIA RED FIR GREEN - DOUGLAS-FIR BLACK - CALIFORNIA BLACK OAK Mean Diameter Trees Per Acre

25 Max SDI depends on sample size used to derive it. This Analysis Sample Point Scale My Previous Work at Cluster Plot Scale Douglas-fir CA red fir white fir

26 Max SDI s Suggested by this Analysis Species Max SDI N white fir 900 1,635 Douglas-fir ponderosa pine Jeffrey pine California red fir incense cedar canyon live oak CA black oak lodgepole pine sugar pine ,109 2,011 1,

27 Is Max SDI truly independent of site quality variables? YES

28 MAX SDI is independent of Site Class 100 Pure (80%+ by BA) Ponderosa Pine Scale of Individual Sample Point (vs. Stand or Cluster Plot) Max SDI 650 Green - Higher Site Class Red - Lower Site Class Mean Diameter Trees Per Acre Lower Site Classes tend to reach maximum density at smaller diameters.

29 MAX SDI is independent of Annual Precip. 100 Pure (80%+ by BA) Ponderosa Pine Scale of Individual Sample Point (vs. Stand or Cluster Plot) Max SDI 650 Green - Annual Precip > 40" Red - Annual Precip < 40" Mean Diameter Trees Per Acre Lower Precipitation Zones tend to reach maximum density at smaller diameters.

30 MAX SDI in independent of Aspect 100 Pure (80%+ by BA) Ponderosa Pine Scale of Individual Sample Point (vs. Stand or Cluster Plot) Max SDI 650 Mean Diameter 10 Green - North and East Aspects ( degrees) Red - South and West Aspects ( degrees) Black - Flat Trees Per Acre Hotter aspects tend to reach maximum density at smaller diameters.

31 MAX SDI in independent of Latitude 100 Pure (80%+ by BA) Ponderosa Pine Scale of Individual Sample Point (vs. Stand or Cluster Plot) Max SDI 650 Mean Diameter 10 Green - Northern National Forests (Plumas north) Red - Southern National Forests (Tahoe south) Black - State, Private, other Federal Trees Per Acre Lower latitudes tend to reach maximum density at smaller diameters.

32 Mortality is Positively Correlated with SDI Probability of Mortality 80% 70% 60% red fir type Frequency (Probabillity) of Mortality 50% 40% 30% 20% 10% 0% Running Average SDI

33 No threshold points where mortality dramatically increases. Mortality/SDI are correlated along a linear gradient. Probability of Mortality 80% 70% red fir type Frequency (Probabillity) of Mortality 60% 50% 40% 30% 20% Linear (red fir type) 10% 0% Running Average SDI

34 Thinning to a residual density of SDI 200 is not a bad practice in any conifer type on any site if you want to keep the probability of mortality around 20%.

35 Red Fir Type (CalVeg) 100 SDI 200 Red Fir Type (CalVeg = RF) 1,625 sample points GREEN X - points without mortality RED BOX - points with mortality Mean Diameter Trees Per Acre

36 Mixed Conifer - Fir Type (CalVeg) 100 Mixed Conifer - Fir Type (CalVeg = MF) 2,865 sample points SDI 200 GREEN X - points without mortality RED BOX - points with mortality Mean Diameter Trees Per Acre

37 Eastside Pine Type (CalVeg) 100 Eastside Pine Type (CalVeg = EP) 1,738 sample points SDI 200 GREEN X - points without mortality RED BOX - points with mortality Mean Diameter Trees Per Acre

38 So by eyeball. SDI 200 looks pretty good. but what is the probability of mortality associated with SDI 200?

39 Let s add forest types, starting with RF Probability of Mortality 80% 70% 60% red fir type Frequency (Probabillity) of Mortality 50% 40% 30% 20% 10% 0% Running Average SDI

40 Add White Fir Probability of Mortality 80% 70% red fir type Frequency (Probabillity) of Mortality 60% 50% 40% 30% 20% white fir type 10% 0% Running Average SDI

41 Add Mixed Conifer - Fir Probability of Mortality 80% 70% red fir type Frequency (Probabillity) of Mortality 60% 50% 40% 30% 20% white fir type mixed conifer fir type 10% 0% Running Average SDI

42 Add Mixed Conifer - Pine Probability of Mortality 80% red fir type 70% white fir type Frequency (Probabillity) of Mortality 60% 50% 40% 30% 20% mixed conifer fir type mixed conifer pine 10% 0% Running Average SDI

43 Add Douglas-fir Probability of Mortality 80% red fir type 70% white fir type Frequency (Probabillity) of Mortality 60% 50% 40% 30% 20% mixed conifer fir type mixed conifer pine type Douglas-fir type 10% 0% Running Average SDI

44 Add Eastside Pine Probability of Mortality 80% 70% red fir type white fir type Frequency (Probabillity) of Mortality 60% 50% 40% 30% 20% mixed conifer fir type mixed conifer pine type Douglas-fir type eastside pine type 10% 0% Running Average SDI

45 Given all the noise in the data, types are pretty similar so lump them into a composite graph.

46 SDI 200 results in 20% probability of mortality Probability of Mortality 80% 70% y = x R 2 = % Frequency (Probabillity) of Mortality 50% 40% 30% 20% 10% 0% Running Average SDI

47 In Conclusion This Analysis Suggests Maximum Stand Density Index (Max SDI) depends on sample size used to derive it. Max SDI truly is independent of site quality variables. Mortality is positively correlated with SDI.

48 In Conclusion This Analysis Suggests Mortality/SDI are correlated along a linear gradient. There are no threshold points where mortality dramatically increases. Thinning to a residual density of SDI 200 is not a bad practice in any conifer type on any site if you want to keep the probability of mortality around 20%.

49 Once again.. don t try this at home without some due diligence.

50 Questions?