A Method For Determining Stand Relative Density And Using The Information To Prescribe A Thinning For Even-aged Northern Hardwoods In New York State

Transcription

1 A Method For Determining Stand Relative Density And Using The Information To Prescribe A Thinning For Even-aged Northern Hardwoods In New York State Ralph D. Nyland Distinguished Service Professor Emeritus Silviculture Department of Forest and Natural Resources Management Based On A Methodology Described in: Marquis, D.A., R.L. Ernst, and S.L. Stout Prescribing silvicultural treatments in hardwood stands of the Alleghenies. US For. Serv. Gen. Tech. Rpt. NE-96. Nyland

2 Roach and Gingrich developed the first stocking guide as an aid in planning thinning... FOR OAK STANDS for oak community types in the central states Roach and Gingrich

3 But Roach later tried it with Allegheny hardwoods with poor results After Roach

4 Until he accounted for species composition separating CAPS (bc, wa, and tulip-poplar) OTHERS (all other species) demonstrating that species composition made a difference 4

5 With a separate line for each species group each A line to represent a different proportion of basal area in CAPs Roach

6 And then adding a family of B lines... B... one for each species group (set at 60% of each A line)... and this worked well in most cases 6

7 But experience suggested that this guide needed enhancement particularly to account for stands with lots of red maple So Stout asked... WHAT IF I add additional species groups? 7

8 She approached it using the Tree-Area Ratio (TAR) TREE-AREA RATIO (TAR) - a mathematical device for apportioning ground area by size of stem diameter - where the area of the a stand is expressed as a function of D & D 2 - (TAR) of all trees present =

9 RELATIVE DENSITY = (TAR) - expressed in CENTACRES - the TAR S for different species can be compared to determine how to best account for species composition when assessing competition in and and among forest stands -TAR values differ between CAPS and two other species groups 9

10 Stand relative density = (Tree relative density) Tree relative density = ƒ (Tree diameter and species) Stout and Nyland

11 So three groups... CAPS bc, wa, & tulip HM-BE hm, be, stm, oaks except ro OTHER all other species 11

12 This defines the contribution of individual trees to stand relative density... by species... the hm-be group... the red maple group... the CAPS Stout and Nyland e.g., for 16-inch tree 12

13 Stout later showed that the number, shape, and position of the lines depends upon the species mix and regional conditions... Stout

14 Generally, the NY relative density factors work best for stands with 40% 50% of basal area in black cherry and white ash in these cases use WKSHTNY for stands with more BC & WA, use the PA relative density factors and use WKSHTPA 14

15 But Stout 1990 only two species groups works better for even-aged northern hardwoods in New York 15

16 Using NY stand data and with simple tests showing the difference in calculated relative density using PA and NY factors 16

17 So complicated... Tim Davis 2001 So how to use it in practical application 17

18 Try this field sheet... RD factors included (Pennsylvania) Marquis et al

19 Quality considered... Acceptable Growing Stock 19

20 Poor trees, too... Unacceptable Growing Stock Marquis

21 This example defines UGS as follows Unacceptable Growing Stock (UGS) ( what Nyland uses) -- a fruiting body on the main stem* -- holes in the main stem -- 25% of major branches dead or dying in the upper crown *Also signs of beech bark disease 21

22 UGS These criteria identify high risk trees that likely will die or deteriorate within a year period making them candidates for salvage 22

23 And species group Marquis et al

24 Three groups for northern hardwoods... CAPS BC, WA, Tulip HM-BE HM, BE, STM, oaks except RO OTHER all other species BC black cherry WA white ash Tulip tulip-poplar HM sugar maple BE American beech STM striped maple RO red oak 24

25 Also by diameter class within each grouping Marquis et al

26 Commonly used diameter classes SAP inches dbh POLE inches dbh SST -- LST inches dbh 17.6 inches dbh* * Some people separate MST and LST. We will not. 26

27 Commonly used diameter classes SAP inches dbh POLE inches dbh SST -- LST inches dbh 17.6 inches dbh* * Some people separate MST and LST. We will not. 27

28 This approach includes all trees 1.0 inches and larger that makes the assessment more objective that shows us the entire stand structure that better depicts species stratification in a stand 1.0 inches and larger 28

29 As an example: Develop thinning prescriptions for HBG-97 using relative density measures to control the intensity of a crown thinning 29

30 Stand USING THIS WORK SHEET

31 But note that it uses the NY RD factors with NO difference between CAPS and RM group

32 You need point sample information about a stand to determine stand relative density by convention we install at least 15 point samples in an even-aged stand using a BAF-10 prism and laid out at random or along a randomly placed grid of points 32

33 So let s use this stand to illustrate the process North Heiberg Forest Stand 97 Grid points at 2- x 2-chain intervals Dashed lines show boundaries of study plots to receive specified treatments. 33

34 providing a data set that looks like this With 18 sample points 34

35 For clarity presented here in a printed format 35

36 So lets figure out how to do the calculations and develop a prescription for crown thinning 36

37 this instruction sheet shows how to do the calculations using a pocket calculator 37

38 FIRST determine the BA conversion factor BA Convert = (BAF factor / # point samples) = 10 / 18 = [Carry this to 3 places] 38

39 Now the BA per diameter class BA/ac = (Trees sampled * BA Conversion factor) So for the Small Sawtimber (SST) in CAPs 14 trees * = 7.78 [Carry this and subsequent calculations to 2 places] 39

40 and done for all cells on the sheet done for all cells by row and column 40

41 then sum the totals from each segment to determine overall stand conditions 41

42 Next determine the average diameters D = average for all size classes DM = average for trees 6 inches dbh using the separate diameter calculation worksheet 42

43 using this worksheet 43

44 first writing in the basal area by size class 44

45 then making these calculations for D DIA BA FOR FOR CLASS CLASS = Di * BAi = = = = = a weighted average across all diameter classes using BA/size class as the weighting factor TOTAL / D >=6" / DM 45

46 and those for DM DIA BA FOR FOR CLASS CLASS = Di * BAi = = = = = done using only poles and larger TOTAL / D >=6" / DM 46

47 That example developed a prescription using data summarized by broad size classes and calculated by hand 47

48 But to speed the process use WKSHTNY to get an answer quickly and accurately from field data sheet as follows 48

49 After studying the instructions pages, open the FIELD DATA page HBG 97 Heiberg Forest June 1997 and enter stand identification information Class 49

50 HBG 97 Heiberg Forest June 1997 also the number of point samples 67 for this new example Class 50

51 Then enter the prism BASAL AREA FACTOR HBG 97 Heiberg Forest June Don t forget to enter this Class 51

52 HBG 97 (67 sample points) Then go to the SUM page entering the field tally data in the yellow columns 52

53 Automatically giving you a summary output Class 53

54 To calculate D and DM DIA BA FOR FOR CLASS CLASS = Di * BAi = = = = = PUSH buttons on the D / DM page TOTAL / D >=6" / DM 54

55 HBG pt samples the results 55

56 This stand has 136 ft 2 /ac of basal area a DM of 13.2 inches a relative density of 96% 64% relative density of AGS 56

57 shown in the box at the bottom of the SUM page 57

58 Now let s use these findings to prescribe a thinning taking out 35% of the relative density but not reducing the stand below 60% Note: if taking 35% reduces RD below 60%, adjust the intensity to leave 60% 58

59 You should find these values on the MARKING page calculated automatically by WKSHTNY 59

60 As a next step, determine what to cut from trees of different sizes to do a crown thinning that generally means taking 1/3 of the cut from trees > D or DM and 2/3 of the cut from trees < D or DM representing a crown thinning Luckily, Marquis et al. (1984) used research data and experience to translate that into a DISTRIBUTION OF CUT chart 60

61 It presents a suggestion for what they call a COMMERCIAL and a COMBINED thinning the former does thinning only among trees 6 inches dbh both versions of Crown thinning numbers indicate the % of cut RD to take out of each size class based on the stand DM or D 61

62 rounding dbh to the nearest inch 62

63 but WKSHTNY automnatically enters a trial distribution of cut from that table with this result 63

64 Then as a trial run it calculates the amount to remove from each diameter class 64

65 Col 2 = the proportion of total cut to take from each diameter class Total cut / dia class = RD in class * Total RD to remove = * 0.68 =

66 BUT does that approach make sense for this stand will it satisfy the objectives Given an objective that thinning should reduce UGS of sawtimber size to salvage the volume in them at least to the degree feasible 66

67 Note that unthinned stands at high latitudes often have appreciable numbers of trees affected by ice, snow, and wind with some trees of all size classes having past injuries and other defects that make them UGS Unacceptable Growing Stock (UGS) ( what Nyland uses) -- a fruiting body on the main stem* -- holes in the main stem -- 25% of major branches dead or dying in the upper crown *Also signs of beech bark disease 67

68 Given that objective would the trial prescription would look at the original UGS to this column many would not come out 68

69 To confirm this subtract the original UGS from the trial cut Col 3 Col 6 a NEGATIVE value means some UGS will still remain 69

70 But remember the objective reduce UGS in sawtimber classes to the degree possible the first trial cut would leave UGS of SST sizes so you must adjust the cut to remove all the UGS of SST 70

71 So adjust the cut to remove UGS of ST sizes to satisfy the objectives 71

72 As a practical matter try starting this process by removing UGS from LST, then go to MST, and then to SST that seems to work best 72

73 but DO NOT drop RD below the target level nor below 60% 73

74 Finally WKSHTNY determines the proportion to cut from each diameter class 74

75 % to cut = : = 0.42 or 42% 75

76 2/5 translated into 2/5 for practical application 76

77 The end point of the analysis AGS & UGS TOTAL STAND SAPS POLES SSAW MSAW LSAW COL MARK NONE 3/5 2/5 1/5 1/3 1/4 1/3 1/4 1/

78 To get a picture of the effect in more tangible terms look at the original basal area 78

79 and see what proportion of basal area to cut Cut BA = Original BA * % RD to cut = * 0.42 = ft 2 /ac 79

80 and check the expected residual basal area in a size class Residual BA = Original BA - Cut BA = = ~ 26 ft 2 /ac 80

81 And for the stand as a whole... and what we LEAVE 81

82 And for the stand as a whole... and this volume 82

83 THE RESIDUAL STAND (Ft 2 /ac) SAPS 2 POLES 26 SST 46 MST 10 LST 3 TOTAL 88 And what would we cut DIA CUT CLASS BA/AC SAP -- POLE 19 SST 20 MST 6 LST 3 ALL 48 83

84 But if you have point sample data with records for individual trees 84

85 Past it into the FIELD DATA page like this 85

86 Leaving this column blank WKSHTNY will calculate it automatically 86

87 Then push the butt9ns on the AGS UGS page 87

88 Then on the SORT page 88

89 Then on the D DM page 89

90 That automatically calculates values for the SUM page 90

91 WKSHY TNY also generates stand table data in a more traditional form so see if it makes sense on the SORT page 91

92 Then follow the steps shown previously for developing the prescription 92

93 And as my mother-in-law s friend commonly said when all else fails, read the instructions again And enjoy 93

94 Background reading: Chapter 17, in Nyland, R.D Silviculture: Concepts and Applications. Waveland Press. Long Grove, IL. Sources cited: Marquis, D.A., R.L. Ernst, and S.L. Stout Prescribing silvicultural treatments in hardwood stands of the Alleghenies. US For. Serv. Gen. Tech. Rpt. NE-96. Roach, B.A A stocking guide for Allegheny hardwoods and its use in controlling intermediate cuttings. US For. Serv. Res. Pap. NE-373. Roach, B.A., and S.F. Gingrich Even-aged silvicutlure for upland central hardwoods. US Dept. Agric., Agric Handbk. No Stout, S.L., and R.D. Nyland Role of species composition in relative density measurement in Allegheny hardwoods. Can. J. For. Res. 16: Stout, S.L Progress Report For Relative Density In Northern Hardwoods Throughout The Northeast. US For. Serv. For. Sci. Lab, Warren, PA. 94