Does Thinning Young Stands Make Sense?

Transcription

1 Juvenile Spacing, Stand Volume, Piece Size & Value: Ken Mitchell & Jim Goudie, Research Branch, B.C. Ministry of Forests Speaker Notes - October 1, 21 We d like to talk about Juvenile Spacing (JS) and its impact on stand volume, piece size, products and value in the context of Growth and Yield (G&Y) at the stand level. Juvenile Spacing, Stand Volume, Piece Size & Value: Presented to the Forest Division Management Team by Ken Mitchell & Jim Goudie, Research Branch, B.C. Ministry of Forests October 1, 21 Last May, the Portland Chapter of the SAF invited us to address the question: Does Thinning Young Stands Make Sense? as part of a panel of experts. About 2 members attended. We learned that silviculturists in Washington and Oregon are enthusiastic about JS. But the panel of G&Y analysts and economists concluded that JS does not make sense at the stand level in terms of extra volume, bigger piece size or financial return. Does Thinning Young Stands Make Sense? Sponsored by:» Portland Chapter of the Society of American Foresters» OSU Extension Service» Western Forestry and Conservation Association» World Forestry Center We left the workshop confident that our BC data, analyses and conclusions are valid. We d like to share this information with you in the context of.. decision support for silvicultural treatments JS in particular. We rely on long-term remeasurement data for spaced and untreated field plots - and we have the best data available. But data are just numbers until they have been analyzed and interpreted correctly. And we have accurate G&Y models that have been validated against data. But our data are limited by historical circumstances and can not cover the potential range of applications. Consequently, we use validated models to fill gaps in our data. Decision Support APPLICATIONS Evaluation of silvicultural treatments Timber supply projections DATA & TOOLS Virtually all G&Y data from BC and elsewhere Advanced analytical & interpretation techniques Sophisticated models that conform to the data LIMITATIONS Field data do not cover the range of applications Analysts use models to fill gaps in our data 1

2 BACKGROUND So why were silviculturists in BC so enthusiastic about spacing in the 7 s? Spacing was practiced in other countries - but often for reasons that don t apply to BC. And spaced stands are appealing. Ever notice that leave trees in spaced stands appear to be bigger and healthier once they are no longer obscured by small trees. And foresters anticipated improved financial return because they expected greater volume but there were no data available to support this claims. And larger piece size a reasonable expectation. And there were very attractive incentives in the form of Section 88 and ACE. Here s the optimistic picture that emerged in the 7 and continued until JS was believed to increase volume 1 and improve financial return 2 at no cost to industry because of Section 88 funding. 3 The extra volume from JS supported accelerated harvesting and higher AACs due to the Allowable Cut Effect incentive. 4 And larger piece size implied lower processing costs, 5 and more valuable products 6 or shorter rotations 7 to achieve the same product. (+) (-) Why the enthusiasm for spacing in the 7 s? Practiced in other countries Spaced stands are appealing Improved financial return expected because of: Improved 2 financial return 3 - Sec ACE greater volume larger piece size attractive incentives (Section 88, ACE) 4 1 Greater standing volume /ha Shorter rotations Valuable 6 products Less 5 processing $Return Volume Piece Size Quality? Other? By 1987, the situation had changed. Our research showed that spacing: provides no extra volume. 1 lengthens rotations. 7 8 And the incentives for industry had largely disappeared. That is, No Section 88 3 because JS costs were transferred to industry. No ACE 4 because there is no extra volume. Consequently, it became unprofitable for industry to space. 2 5 Since then, spacing has been driven by statutory requirements. (+) (-) Valuable products 4 Less processing $Return Volume Piece Size Quality? Other? Reduced Longer investment return5 rotations8 2

3 By 2, we learned that JS produces lumber of lower strength for many species 9 and larger knots. And other specialists learned that JS may exacerbate losses 1 caused by some insects and diseases. However, job creation motivated much of the interest in spacing in the 9s 11 (+) 2 Valuable products Less processing Job creation 11 (-) $Return Volume Piece Size Quality Other Reduced investment return Longer rotations Degraded wood properties & product value 9 Pest 1 damage And the issues are still changing. In the past year, we ve learned that JS does not produce more value 6 as you ll see later. And engineered wood products and substitutes are expected to offset some of the benefits of piece size. 1 And finally, priorities are shifting from employment 11 to investment return. 5 Reduced logging and milling costs 5 remain as the main benefit of spacing but even their importance is being questioned in stands of lodgepole because of advances in logging and milling technology. (+) 5 (-) 21 Less 5 processing $Return Volume Piece Size Quality Risk Reduced investment return 6 Longer rotations Degraded wood properties & product value 11 Pest damage Competing products 1 ANALYICAL TECHNIQUES Now I d like to introduce you to some analytical techniques both good and bad. Average diameter has fueled support for JS for decades because it has been equated to larger piece size, lower processing costs, more valuable products and shorter rotations. ANALYTICAL TECHNIQUES Good and bad! 3

4 Here s an example used for training one that we ve tried to discourage. It s based on output from TIPSY a G&Y product developed by our group. It claims we can harvest approximately 1 years sooner with spacing than without if we harvest when these stands of pine achieve an average diameter of 25 cm. And we agree but we don t believe that average DBH is a useful harvest criterion. Notice that spacing looks very good in this example. But not when we look at what else TIPSY tells us about this scenario. Harvest when average DBH reaches 25 cm Why Space? (lodgepole pine) harvest approximately 1 years sooner with spacing than without. TIPSY 3.b Here s how JS affected the number of live trees. We see that it removed 36 stems at age 2 leaving 1 trees. TIPSY 3.b JS Harvest Now look at the development of average diameter. Spacing followed by harvesting at a target diameter of 25 cm appears to reduce the harvest age by 1 or more years without reducing average diameter. But TIPSY will later show that both stands are of equal value if harvested at age 1. TIPSY 3.b 4

5 Here s the no. of trees by diameter class in the unspaced and spaced stands at age 1. You can see there are just over trees in the 15- cm diameter class ( cm DBH) in the untreated stand, and 1 in the thinned stand. The removal of the smallest trees at age 2 has elevated the average DBH from 18 to 25 cm by age 1. By spacing, we ve traded many 1 to 2 cm trees for a few 3 to 35 cm trees. Look at the unspaced stand that regenerated with trees and notice that it has many large trees (25 cm+) - but not quite as many as the spaced stand. The myth that dense regeneration only produces pecker poles at harvest is not true! TIPSY 3.b 18 cm 25 cm Average 1 yrs Here s the corresponding merchantable volume in each diameter class. Now look at the difference in volume between the spaced and unspaced stand. We ve traded 115 m 3 of small wood for 86 m 3 of larger material. These stands also have 191 m 3 in common across the range of diameters. 7 Difference in Merch Vol 1 yrs 115 m m yrs Now convert this volume into lumber & chips, and value Diameter Class (cm - 5) Here s the distribution of lumber by dimensions at age 1 - plus chips. Look at the relative volume in thousands of board feet (mbf) of each dimension. The spaced stand has 3 extra board feet (.3 mbf), but is short 5 bone dry units of chips. If we apply the lumber and chip values in row 2 to the volumes we see a net loss of $43. Yield of spaced and unspaced lodgepole pine at age 1 Dimension 2 x 4 2 x 6 2 x 8 2 x 1 Lumber Chips Price $387/mbf /bdu Volume Spaced Unspaced Difference.3-5 Value ($) Spaced Unspaced Difference $12 -$5 Net diff -$43 An investment in spacing of $ gives us a net loss of about $4-1 years later! 5

6 Here s a similar example for a stand of coastal hemlock growing on site 24. Harvest when average DBH reaches 4 cm (western hemlock) harvest approximately years sooner with spacing than without. TIPSY 3.b And here are the results of our analyses. An investment in spacing of about $1 gives us a negligible return 1 years later. These examples looked great in terms of average DBH but not when expressed as products or value. The use of average diameter was evaluated and rejected by the Chief Forester s Stand Density Management Working Group. Consequently, it was not incorporated into the 1999 Guidelines for Developing Stand Density Management Regimes. Those who use average DBH to promote spacing run the risk of making very poor investment decisions. RESULTS Now Jim will demonstrate this analytical approach using representative data from our field experiments. The two trials we are presenting today, these Schenstrom plots and later a juvenile spacing trial from Washington State, represent the two thinning trials that cover a typical rotation in the Pacific Northwest. We use such data for long-term validation of our prediction systems - and our models perform well in comparison to the data. In 1929, J.R. Schenstrom established five large plots on Cowichan Lake Research Station to compare, in the classic European tradition of multiple entries, the development of thinned and unthinned stands. Multiple thinnings were believed to be most productive over a rotation, albeit quite expensive to implement. These plots were thinned 8-1 times, between 1929 and 197. They have been measured 16 times over 7 years and are still being measured today. When we compare the thinned plot to the unthinned plots, it turns out that the advantage is minimal. Now look at these stands in 1994 Yield of spaced and unspaced hemlock at age 1 Dimension 2 x 4 2 x 6 2 x 8 2 x 1 Lumber Chips Price $417/mbf /bdu Volume Spaced Unspaced Difference Value ($) Spaced Unspaced Difference $1 33 -$76 Net diff $57 Schenstrom crown thinning plots before and after treatment (Age 19) Unthinned (25, stems/ha) Thinned (5, stems/ha) 6

7 after they have both grown in height from 12 to over m to form some very nice stands. Schenstrom plots May 21, 1994 (Age 83) Unthinned (692 stems/ha live) Thinned (199 stems/ha live) Here is the trends of number of live trees over time. Note the high establishment densities (~2,/ha). Let s focus on the lower part of the curve from ages 3 to 88. Schenstrom plot thinning experiment for Douglasfir at Cowichan Lake Research Station Number of live stems (/ha) Crown thinnings Low thinnings Age We see the multiple thinnings and high rates of natural mortality in the control plot more clearly. Note that the thinned plots now have about 2-3 stems/ha and the control plot about 6. Schenstrom plot thinning experiment for Douglasfir at Cowichan Lake Research Station Number of live stems (/ha) Thinnings Crown thinnings Low thinnings Age Natural mortality 7

8 Here is the most misleading statistic in forestry, average DBH. At age 88, the thinned plots have 22 to 59 percent higher average DBH than the control. When this statistic is presented, most foresters believe that all trees are that much bigger and thinning is the reason. However, there are other factors which we will discuss. Quadratic mean DBH(cm) Average DBH at age 88 years (Percent greater than control) +22% +35% Light low Heavy low Heavy crown Treatment +44% +59% The trend of mean DBH over age shows that much of the increase was due to the so-called chainsaw effect whereby average DBH is elevated simply because small trees are removed. This may impact rotation length if stands are harvested at a prescribed target diameter. Quadratic mean DBH(cm) Schenstrom plots Crown thinnings Low thinnings Chainsaw effect Age For example, a 4-cm target reduces the rotation length by about 2 to 3 years. In isolation, this may lead to irrational activities whereby you remove small trees, elevate mean diameter, instantly achieve your target and immediately harvest! In our view, it is much better to look at the number of stems by diameter class. We will compare the control plot with one of the better performing thinned plots (light crown) in terms of number of trees, and later volume by diameter class Quadratic mean DBH(cm) Schenstrom plots Crown thinnings Low thinnings Target diameter Chainsaw effect Age 32 years Light crown 8

9 This graph shows the current number of stems by DBH class. The control has 1 stems/ha in the 25- cm class and 19/ha in the 65-cm class. Whereas the thinned plot has1 stems/ha, and 23/ha in the same classes. Note that the control plot has large trees - a message not carried by mean diameter. The only classes not in common are the 7-85 cm classes. What is really important is the difference between treated and control. That is, No. stems/ha 1 1 Current diameter distribution 1/ha 19/ha /ha DBH class (cm) 23/ha..by thinning, we trade 429 small trees for 32 large ones, or, Difference in number of trees 1 No. stems/ha trees/ha 32 trees/ha DBH class (cm)...about 6m 3 of small trees for about 2m 3 in large trees. Difference in volume Is it worth it? To help answer this, let s return to the tree DBH distribution No. volume/ha stems/ha m 3 /ha 429 trees/ha 211 m 3 /ha 32 trees/ha DBH class (cm) 9

10 We have the software to buck each tree into logs. The next slide shows the number of 5-m logs by small end diameter. Notice how the lower tails of the plots shown here begin to fill in, when we look at the distribution of logs No. stems/ha 1 1 Distribution of number of trees Trees DBH class (cm) the thinned plot shows the greatest gain. This happens because some of the trees from thinned plots are small, and have taper ( i.e. small top logs). Now look at the difference in log volume. We convert No. logs/ha stems/ha Distribution of logs Trees Logs DBH class (cm) 57.5 Log DIB class (cm) about 56 m 3 /ha in small logs to 1 in larger ones. Note there is also 63 m 3 /ha in common between these two treatments. Log distribution difference Are the treatments worth it? We need to look a little further. We also have the software to saw these logs into... volume/ha m 3 /ha m 3 /ha Log DIB class (cm) 1

11 .. lumber. The control plot has the most 2X4s, 6s and 8s, in part due to more live trees. It also has almost as many board feet in 2X1s because it has some big trees. In fact it has... Lumber volume (bd.ft./ha) 1 1 Lumber distributions 2X4 2X6 2X8 2X1 Lumber size (in.)..18 mbf more 2X4s to 2X8s and only 4 mbf less 2X1s. Difference in current lumber distributions This is at 88 years. How about earlier ages? 1 Lumber volume (bd.ft./ha) 1 18mbf/ha 4mbf/ha 2X4 2X6 2X8 2X1 Lumber size (in.) Here we see the difference distribution at ages 88, 7, 6, and 4 years. Difference in lumber distributions at various ages Note that the picture doesn t change much across ages. If we assign 1996 dollar values to these distributions, we see that Lumber volume (bd.ft./ha) Total age Total age 4 2X4 2X6 2X8 2X1 Lumber size (in.) 11

12 the differences in value plateau at about $48,/ha at 7 years - in favour of the control. A reasonable harvest age is probably between 6 and 7 years. Note that this is not an economic or financial analysis because I omitted: treatment and harvesting costs, values for other products (e.g. pulp), wood quality, discounting, values from thinnings - although we have that information available. Thinning volumes weren t included because it isn t profitable to repetitively thin in BC as Europeans have done in the past. The thinned boards are worth about $32, spread over stand ages 2-55 years. I hope that specialists in Economics and Trade Branch will complete a financial analysis of this and other trials. These predictions only suggest that thinning on this site is not likely to create more lumber value. The next slides provide more insight. Lumber value ($Can/ha) Difference in lumber value at various ages (control-light crown thinning) (no discounting) Total age on site 38 The untreated plot gives more 2X4s, 6s and 8s (all about equal value per mbf) after the stands reach about 35 years of age. The higher-valued 2X1s were Lumber yields (2X4-2X8) for Schenstrom plots Lumber volume (bd.ft/ha) Crown thinnings Low thinnings Age Light crown 12

13 never very far behind and have recently caught up. Predicted lumber yields (2X1) for Schenstrom plots Now let s discuss the long-term trial from Southwest Washington State that focuses on juvenile spacing. Lumber volume (bd.ft/ha) Crown thinnings Low thinnings Age Light crown Researchers spaced one of two large plots at age 9. The control plot in green began with about 11 stems/ha. Note again the heavy natural mortality over the 6 years of plot history. The thinned plot (pink) was reduced from 6 to 16 stems/ha and now has about the same number of stems alive as the control. Number of live stems (/ha) Thinning experiment for Douglas-fir at Martha Creek, SW Washington State 1 1 (~16 stems/ha) Thinned Age Here we see that average DBH diverges from age 2 to 4 - in part due to a chainsaw effect - but later converges as small trees in the control plot die of natural mortality. We will now skip directly to lumber Quadratic mean DBH(cm) Thinning experiment for Douglas-fir at Martha Creek, SW Washington State Thinned Age 13

14 ... where we see that the volume for the control and thinned plot are very similar - but the thinned plot has slightly more volume Lumber distributions Lumber volume (bd.ft./ha) Thinned 2X4 2X6 2X8 2X1 Lumber size (in.) in the smallest lumber sizes. To be precise, the extra lumber volume is only 11 mbf/ha. The 2X1 volume is almost identical. The next logical step would be to perform an economic analysis. I should point out that like most of our data, these are well-protected research plots that have incurred few pests or damaging events (snow, ice, wind, sunscald etc.). In addition, the leave trees were selected with great attention to tree vigour and spacing. It is not unreasonable to expect that operational thinning would be less precise and less responsive in most cases. Lumber volume (bd.ft./ha) Difference in lumber distributions 11 mbf/ha more in thinned plot 2X4 2X6 2X8 2X1 Lumber size (in.) Thinned In summary, we have consistently summarised all the available thinning data in western Canada and the Pacific Northwest from various sources Government (BCMoF, AFS, Forestry Canada, USFS, WSDNR) Universities (UBC, UW, UI) Companies (e.g. Weyerhaeuser, WFP, Rayonier) Co-operatives Literature We also have 4 additional thinning studies from other countries (New Zealand, France, Sweden, UK). When summarised consistently, and analysed and interpreted by growth and yield specialists, the results are fairly clear - thinning is relatively neutral in terms of value. But there are holes in the data that our validated models can help fill. Please contact us if further information is desired. Conclusion about the data We have consistently summarised all the available thinning data in western Canada and the Pacific Northwest from: Government (BCMoF, AFS, Forestry Canada, USFS, WSDNR) Universities (UBC, UW, UI) Companies (e.g. Weyerhaeuser, WFP, Rayonier) Co-operatives Literature We also have additional thinning studies from other countries (New Zealand, France, Sweden, UK), that adds up to about 4 thinning studies in total, domestic and foreign When summarised consistently, and analysed and interpreted by growth and yield specialists, the results are fairly clear - but there are holes that our validated models can help fill. Please contact us if further information is desired. 14

15 EXCEPTIONS We don t want to give the impression that stands never benefit from spacing. For example, we have ample evidence that spacing is imperative at an early age in dense fire-origin stands of lodgepole pine to avoid repression. However, research in progress will likely show that JS is not needed in dense stands of logging origin because trees regenerate over a period of about 15 years. Exceptions Some stands can benefit from spacing based on other research: Dense fire-origin stands of lodgepole pine Douglas-fir on dry coastal sites And I m sure you re aware of other reasons for spacing that go beyond G&Y at the stand level. Here are a few. Yield effects at the forest-level Employment, biodiversity, tree stability, stand health & risk (pests) Relationship to other treatments (e.g., fertilization & pruning) Maximum density Issues not Addressed Yield effects at the forest-level Employment, biodiversity, tree stability, stand health & risk (pests) Relationship to other treatments (e.g., fertilization & pruning) Maximum density WHAT OTHERS TELL US What are others telling us about juvenile spacing? Here s an example of what we heard from analysts at the workshop in Portland. "PCT and early thinning are usually not good financial investments. Even with very aggressive price premiums, most thinning of planted stand densities does not make economic sense." "PCT and early thinning are usually not good financial investments. Even with very aggressive price premiums, most thinning of planted stand densities does not make economic sense." Greg Johnson, Forest Research Coordinator Willamette Industries, Inc. 15

16 But everyone didn t agree. One silviculturist who attended the meeting commented. I will continue to support thinnings combined with a pruning program and longer rotations. I refuse to believe that large diameter, high quality logs are going to be a problem to sell. I will continue to support thinnings combined with a pruning program and longer rotations. I refuse to believe that large diameter, high quality logs are going to be a problem to sell." To which Greg Johnson replied: You are not alone in your willingness to pay more for high quality, large boards, however, the market has not agreed with you. You are not alone in your willingness to pay more for high quality, large boards, however, the market has not agreed with you." Greg Johnson, Forest Research Coordinator Willamette Industries, Inc. Here are some thoughts about net present value (NPV) from a BC analyst who didn t attend the meeting. JS is high cost, entails long carrying periods, and is high risk JS reduced NPVs with NPVs declining rapidly as site index moved below 3m Value comes from differentiating the products not the resource... It takes too long to differentiate the resource once you know what the market wants. JS is high cost, entails long carrying periods, and is high risk JS reduced NPVs with NPVs declining rapidly as site index moved below 3m Value comes from differentiating the products not the resource... It takes too long to differentiate the resource once you know what the market wants Reid Carter, Paper & Forest Products Analyst, National Bank Financial 16

17 And here s some interesting news from New Zealand. Bill Dyck recently confirmed that Carter Holt Harvey, one of two largest forest companies in NZ, is moving away from spacing. They used to plant 1 sph and thin twice to 3 with a pruning at 6 m. Now they now plant 555 trees/ha with no follow up silviculture planned. Management strategy of Carter Holt Harvey Old: plant 1 sph and thin twice to 3 with pruning at 6 m. New: plant 555. (3 x 6 m. espacement) Bill Dyck Science and technology broker, Cambridge, New Zealand RECOMMENDATIONS Because of the growing concern about investment return - we recommend that Economics and Trade Branch be invited to evaluate the economics of JS within the context of the goals of the new government. Secondly, we recommend the ministry support & implement the process documented in the 1999 Guidelines for Developing Stand Density Management Regimes. These Guidelines were expected to move management away from administrative standards in favor of G&Y and economic considerations developed by Research Branch, Economics & Trade Branch, and others. If this issue is not resolved, we recommend that the ministry sponsor a panel of external experts to review the future of juvenile spacing in BC. RECOMMENDATIONS Request that Economics and Trade Branch evaluate the economics of JS within the context of the goals of the new government Support & implement the process developed in the 1999 Guidelines for Developing Stand Density Management Regimes. Create an panel of experts to review juvenile spacing THANK YOU 17