This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. USDA F o r e s t Service G e n e r a l Technical Report INT- 16 September 1974 HANDBOOK FOR INVENTORYING DOWNED WOODY MATERIAL James K. Brown INTERMOUNTAIN FOREST AND RANGE EXPERIMENT STATION F o r e s t Service U. S. Department of Agriculture Ogden, Utah 84401 Roger R. Bay, D i r e c t o r THE AUTHOR JAMES K. BROWN received his bachelor's degree from the University of Minnesota in 1960, his master's from Yale University in 1961, and his Ph. D. from the University of Michigan in 1968, all in forestry. From 1961 to 1965 he did research on field measurement of fuel properties and fire-danger rating systems while with the Lake States Forest Experiment Station. In 1965 he transferred to the Northern Forest Fire Laboratory, Missoula, Montana, where he i s responsible for research on the physical properties and inventory of fuel. CONTENTS Page ........................... NUMBER AND SIZE O F SAMPLING PLANES . . . . . . . . . . . 3 ........................ 4 INTRODUCTION FIELD PROCEDURES 1 ..................... 4 Sample Point P r o c e d u r e s . . . . . . . . . . . . . . . . . . . . 4 Tally Rules . . . . . . . . . . . . . . . . . . . . . . . . . 9 Heavy Slash Options . . . . . . . . . . . . . . . . . . . . 11 Utilization Options . . . . . . . . . . . . . . . . . . . . . 12 F i e l d Equipment . . . . . . . . . . . . . . . . . . . . . . . . 12 CALCULATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 FURTHER APPLICATIONS . . . . . . . . . . . . . . . . . . . . . 19 LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . 20 APPENDIX1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Sampling Intensities . . . . . . . . . . . . . . . . . . . . . . 21 Number and Size of Sampling P l a n e s . . . . . . . . . . . . . 21 Sampling P r e c i s i o n f o r Depth M e a s u r e m e n t s . . . . . . . . . 22 APPENDIX I1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Specific G r a v i t i e s of Sound M a t e r i a l . . . . . . . . . . . . . 23 APPENDIX I11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Calculating Needle Quantities . . . . . . . . . . . . . . . . . 24 Locating Sample Points To facilitate debris management, procedures for inventorying downed woody material a r e presented. Instructions show how to estimate weights and volumes of downed woody material, fuel depth, and duff depth. Using the planar intersect technique, downed material is inventoried by 0- to 0.25-inch, 0.25- to 1-inch, and 1- to 3-inch diameter classes; and by 1-inch classes for sound and rotten pieces over 3 inches. The method is rapid and easy to use and can be applied to naturally fallen debris and to slash. The method involves counting downed woody pieces that intersect vertical sampling planes and measuring the diameters of pieces larger than 3 inches in diameter. The piece counts and diameters permit calculation of tons per acre. OXFORD: 431 KEYWORDS: fire causes (forest), fuel inventory, forest fuels, debris, planar intersect method, sampling methods. T h i s Handbook t e l l s how t o i n v e n t o r y weights, volumes, and depths o f downed woody m a t e r i a l . Downed woody m a t e r i a l i s t h e dead t w i g s , branches, stems, and b o l e s o f t r e e s and brush t h a t have f a l l e n and l i e on o r above t h e ground. T h i s m a t e r i a l i s u s u a l l y c a l l e d s l a s h o r logging d e b r i s i f man c r e a t e s it by c u t t i n g ; it i s c a l l e d f u e l , n a t u r a l d e b r i s , o r d e t r i t u s i f it accumulates w i t h o u t c u t t i n g . Inventorying downed woody m a t e r i a l can h e l p land managers p r a c t i c e f u e l management, p l a n f o r p r e s c r i b e d f i r e , and e s t i m a t e u t i l i z a t i o n p o t e n t i a l . For example, u n d e s i r a b l e f u e l h a z a r d s can b e i d e n t i f i e d and p l a n s made f o r h a z a r d r e d u c t i o n . F i r e behavior i n w i l d e r n e s s a r e a s can be p r e d i c t e d t o a i d i n implementing l e t - b u r n f i r e p o l i c i e s . The volume of downed f i b e r can be e s t i m a t e d t o p l a n f o r s a l e s , removal, and u t i l i z a t i o n . Managers can communicate i n e x a c t terms about t h e i r d e b r i s problems. The i n v e n t o r y can be done t o provide a l l o r any p a r t o f t h e following i n f o r m a t i o n : 1. Weights and volumes p e r a c r e of downed woody m a t e r i a l f b r a. Diameter s i z e c l a s s e s of 0 t o 0.25, 0.25 t o 1, and 1 t o 3 i n c h e s ; and b. Diameters of 3 i n c h e s and l a r g e r f o r sound and r o t t e n c o n d i t i o n s . 2. Average diameter o f d e b r i s l a r g e r t h a n 3 i n c h e s . 3. Depth o f f u e l and f o r e s t f l o o r d u f f . This Handbook a p p l i e s most a c c u r a t e l y i n t h e western United S t a t e s because it c o n t a i n s average p a r t i c l e d i a m e t e r s f o r western c o n i f e r s ; however, t h e procedures a r e a p p r o p r i a t e f o r f o r e s t s everywhere. The i n v e n t o r y procedures a r e r a p i d and easy t o u s e . For average amounts o f downed d e b r i s , about 5 t o 6 minutes p e r sample p o i n t a r e r e q u i r e d f o r t h e measurements. More time i s u s u a l l y s p e n t i n t r a v e l i n g and l o c a t i n g sample p o i n t s t h a n i n making t h e measurements. I f o n l y downed woody m a t e r i a l i s i n v e n t o r i e d , a two-man crew can complete 20 t o 40 p l o t s a day, depending on how much debris is present. The i n v e n t o r y o f volumes and weights i s based on t h e p l a n a r i n t e r s e c t technique (Brown 1971; Brown and Roussopoulos 1974), which h a s t h e same t h e o r e t i c a l b a s i s a s t h e l i n e i n t e r s e c t t e c h n i q u e (Van Wagner 1968) The p l a n a r i n t e r s e c t technique i n v o l v e s c o u n t i n g i n t e r s e c t i o n s o f woody p i e c e s with v e r t i c a l sampling p l a n e s t h a t resemble g u i l l o t i n e s dropped through t h e downed d e b r i s . Volume i s e s t i m a t e d ; t h e n weight i s c a l c u l a t e d from volume by applying e s t i m a t e s o f s p e c i f i c g r a v i t y of woody m a t e r i a l . The p l a n a r i n t e r s e c t technique i s n o n d e s t r u c t i v e and avoids t h e timeconsuming, c o s t l y , and o f t e n i m p r a c t i c a l t a s k of c o l l e c t i n g and weighing l a r g e quant i t i e s of forest debris. . Woody p i e c e s l e s s t h a n 3 i n c h e s i n diameter a r e t a l l i e d by s i z e c l a s s e s . P i e c e s 3 i n c h e s and l a r g e r a r e r e c o r d e d by t h e i r d i a m e t e r s . S i z e c l a s s e s o f 0 t o 0.25, 0 . 2 5 t o 1, and 1 t o 3 i n c h e s were chosen f o r t a l l y i n g i n t e r s e c t i o n s because: 1. The c l a s s i n t e r v a l s p r o v i d e t h e most r e s o l u t i o n f o r f i n e f u e l s and a r e small enough t o permit p r e c i s e e s t i m a t e s o f volume. 2 . They correspond, i n i n c r e a s i n g s i z e , t o I - , lo-, and 100-hour average moisture t i m e l a g c l a s s e s f o r many woody m a t e r i a l s (Fosberg 1970) [These a r e s t a n d a r d moisture t i m e l a g s used i n t h e National Fire-Danger Rating System (Deeming and o t h e r s 1972) ] . . I n v e n t o r y chosen a r e a s a s f o l l o w s : 1. Decide on l e n g t h o f sampling p l a n e s and number of sample p o i n t s . 2. Complete t h e f i e l d w o r k . 3. C a l c u l a t e weight o r volume, s i z e , and depth of d e b r i s . NUMBER AND SIZE OF SAMPLING PLANES Choose sampling p l a n e l e n g t h s from t h e f o l l o w i n g t a b u l a t i o n : Diameter o f debris Downed material Nons l a s h ( n a t u r a l l y f a l l e n m a t e r i a l ) Discontinuous l i g h t s l a s h Continuous heavy s l a s h ' 6 6 3 10-12 10-12 6 35-50 35-50 -15-25 For any a r e a where e s t i m a t e s a r e d e s i r e d , 15 t o 20 sample p o i n t s should b e l o c a t e d u s i n g t h e sampling p l a n e l e n g t h s shown i n t h e t a b u l a t i o n . This sampling i n t e n s i t y w i l l o f t e n y i e l d e s t i m a t e s h a v i n g s t a n d a r d e r r o r s w i t h i n 20 p e r c e n t o f t h e mean e s t i m a t e s . Areas l a r g e r t h a n approximately 50 a c r e s t h a t c o n t a i n a high d i v e r s i t y i n amount and d i s t r i b u t i o n o f downed m a t e r i a l should be sampled w i t h more t h a n 20 p o i n t s . I f m a t e r i a l l a r g e r t h a n 3 i n c h e s i n diameter i s s c a n t y o r unevenly d i s t r i b u t e d , t h e l o n g e r sampling p l a n e s i n t h e t a b u l a t i o n should b e used. The amount and d i s t r i b u t i o n of downed woody m a t e r i a l vary g r e a t l y among and w i t h i n s t a n d s . Thus, t h e s e sampling recommendat i o n s should b e c o n s i d e r e d approximate because a g r e a t e r o r fewer number of p l o t s may be r e q u i r e d t o f u r n i s h adequate p r e c i s i o n f o r any given a r e a . Sampling i n t e n s i t i e s a r e d i s c u s s e d f u r t h e r i n Appendix I . Locating Sample Points Locate p l o t s s y s t e m a t i c a l l y ; two methods a r e : 1 . Locate p l o t s a t a f i x e d i n t e r v a l along t r a n s e c t s t h a t l a c e r e g u l a r l y a c r o s s a sample a r e a (uniform sampling g r i d ) . For example, on a sample a r e a , mark o f f p a r a l l e l t r a n s e c t s t h a t a r e 5 t o 10 c h a i n s a p a r t . Then along t h e t r a n s e c t s l o c a t e p l o t s a t 2- t o 5-chain i n t e r v a l s . Locate p l o t s a t a f i x e d i n t e r v a l along a t r a n s e c t t h a t r u n s d i a g o n a l l y 2. through t h e sample a r e a . To minimize b i a s , have t h e t r a n s e c t c r o s s obvious changes i n f u e l s . Before e n t e r i n g t h e sample a r e a , determine a t r a n s e c t azimuth and d i s t a n c e between p l o t s . Sample Point Procedures Step 1: Mark the sampling point with a c h a i n i n g p i n (No. 9 w i r e o r s i m i l a r i t e m ) . Avoid d i s t u r b i n g m a t e r i a l around t h e p o i n t . Accurate e s t i m a t e s r e q u i r e measurements o f u n d i s t u r b e d m a t e r i a l . I f s t a n d i n g t r e e measurements (d. b .h . and h e i g h t ) a r e a p a r t of t h e i n v e n t o r y , measure downed m a t e r i a l f i r s t . Step 2: Determine d i r e c t i o n o f sampling plane by t o s s i n g a d i e t o i n d i c a t e one o f s i x 30" a n g l e s between 0" and 150" ( f i g . 1 ) . The 0" heading i s t h e t r a n s e c t d i r e c t i o n . Turn a f i x e d d i r e c t i o n , such a s clockwise, t o p o s i t i o n t h e sampling p l a n e . A s an a l t e r n a t i v e f o r i n d i c a t i n g d i r e c t i o n of t h e sampling p l a n e , u s e t h e p o s i t i o n o f t h e second hand on a watch a t a given i n s t a n t . To avoid b i a s i n placement of t h e sampling p l a n e , do n o t look a t t h e f u e l o r ground while t u r n i n g t h e i n t e r v a l . Figure I . --Locating sampling plane b y using die t o pick one of s i x directions. Step 3: Denote position of the sampling plane by running a t a p e o r s t r i n g out from t h e sampling p o i n t paralleZ t o the ground i n t h e d i r e c t i o n determined i n S t e p 2 ( f i g . 2 ) . Extend t h e t a p e t o t h e l e n g t h o f t h e l o n g e s t sampling p l a n e . A f i b e r g l a s s rod o r 1/2-inch aluminum t u b e p l a c e d along t h e s t r i n g beginning a t t h e sampling p o i n t f a c i l i t a t e s counting p i e c e s l e s s t h a n 1 inch i n diameter. The rod should b e 6 f e e t long, t h e l e n g t h o f sampling p l a n e f o r small p a r t i c l e s . The t a p e and rod f i x t h e p o s i t i o n of v e r t i c a l sampling p l a n e s . / Grid Line or Transect \ 30° For \ \ each dot on die \ -1-3 \ in Tally 1L 3+ in Tally d Figure 2. --Top view of smnplirzg plane and location of fuel depth measurements. 5 Step 4: Step 5 : Measure or estimate slope by s i g h t i n g along t h e sampling p l a n e from t h e sample p o i n t u s i n g an Abney l e v e l o r s i m i l a r d e v i c e . Ample p r e c i s i o n i s t h e n e a r e s t 10 p e r c e n t , which can be coded u s i n g one d i g i t (10 p e r c e n t = 1, 90 p e r c e n t = 9 , e t c . ) . Tally the number of particles t h a t i n t e r s e c t t h e sampling p l a n e by t h e following s i z e c l a s s e s : 0 t o 0.24 i n c h (0 t o 0.6 cm) 0.25 t o 0.99 i n c h (0.6 t o 2.5 cm) 1 . 0 t o 2.99 i n c h e s ( 2 . 5 t o 7.6 cm) The i n t e r s e c t i o n s can be counted one s i z e c l a s s a t a time o r "dot t a l l i e d , " which t a k e s s l i g h t l y l o n g e r t h a n counting ( s e e sample d a t a form, page 1 4 ) . The a c t u a l diameter o f t h e p a r t i c l e a t t h e p o i n t o f i n t e r s e c t i o n determines i t s s i z e c l a s s . A go-no-go gage w i t h openings 0.25 i n c h , 1 i n c h , and 3 i n c h e s works w e l l f o r s e p a r a t i n g b o r d e r l i n e p a r t i c l e s i n t o s i z e c l a s s e s and f o r t r a i n i n g t h e eye t o r e c o g n i z e s i z e c l a s s e s ( f i g . 3 ) . The v e r t i c a l p l a n e i s a p l o t . Consequently, i n counting p a r t i c l e i n t e r s e c t i o n s , it i s v e r y important t o v i s u a l i z e t h e p l a n e p a s s i n g through one edge o f t h e p l o t rod and t e r m i n a t i n g along an imaginary f i x e d l i n e on t h e ground. Once visualized on the ground, the posit<on of the line should not be changed while counting particles ( f i g . 4 ) . See t a l l y r u l e s f o r q u a l i f y i n g particles. Figure 3. --Dimnet& the intersected i s checked with no-go gage. The rod marks the sa pling plane. Figure 4. --The sampling plane i s exactly defined b y one edge of the plot rod. @ Intersections Step 6 : Take three measurements of dead fuel depth. Record depth a s t h e v e r t i c a l d i s t a n c e from t h e bottom o f t h e l i t t e r l a y e r t o t h e h i g h e s t i n t e r s e c t e d dead p a r t i c l e f o r each o f t h r e e a d j a c e n t 1-foot-wide v e r t i c a l p a r t i t i o n s o f t h e sampling p l a n e ( f i g . 5 ) . L i t t e r i s t h e s u r f a c e l a y e r o f t h e f o r e s t f l o o r and c o n s i s t s o f f r e s h l y f a l l e n l e a v e s , n e e d l e s , t w i g s , b a r k , and f r u i t s . Begin t h e v e r t i c a l p a r t i t i o n s a t t h e sample p o i n t . Record t o t h e n e a r e s t whole i n c h . 1 -Foot Fuel / 0 Sample Point / 9 Figure 5. --Cross sect i o n of a fuel bed. Depth i s measured along the arrows i n each l - f o o t wide partition. 0 0 -Wide Vertical Partitions Depth should b e measured from o n l y t h o s e p a r t i c l e s i n c l u d e d i n t h e i n v e n t o r y f o r loading. For example, p a r t i c l e s a c c e p t a b l e f o r measurement by t h e p l a n a r i n t e r s e c t technique a r e a l s o a c c e p t a b l e f o r determining depth. I f o t h e r t e c h n i q u e s a r e used t o e s t i m a t e weight p e r a c r e o f g r a s s and f o r b s , t h i s v e g e t a t i o n would a l s o q u a l i f y f o r determining depth. Stev 7 : Measure v e r t i c a l depth o f d u f f t o t h e n e a r e s t 0 . 1 inch u s i n g a r u l e r along t h e sampling p l a n e a t two p o i n t s : (1) 1 f o o t from t h e p l o t c e n t e r ; and ( 2 ) a f i x e d d i s t a n c e of 3 t o 5 f e e t from t h e f i r s t measurement. Duff i s t h e f e r m e n t a t i o n and humus l a y e r s of t h e f o r e s t f l o o r . I t does n o t i n c l u d e t h e f r e s h l y c a s t m a t e r i a l i n t h e l i t t e r l a y e r . The t o p o f t h e d u f f i s where n e e d l e s , l e a v e s , and o t h e r c a s t o f f v e g e t a t i v e m a t e r i a l have n o t i c e a b l y begun t o decompose. I n d i v i d u a l p a r t i c l e s u s u a l l y w i l l be bound by f u n g a l mycelium. When moss i s p r e s e n t , t h e t o p o f t h e d u f f i s j u s t below t h e green p o r t i o n o f t h e moss. The bottom of t h e d u f f i s mineral s o i l . C a r e f u l l y expose a p r o f i l e o f t h e f o r e s t f l o o r f o r t h e measurement. A k n i f e o r h a t c h e t h e l p s b u t i s n o t e s s e n t i a l . Avoid compacting o r loosening t h e d u f f where t h e depth i s measured. When stumps, l o g s , and t r e e s occur a t t h e p o i n t of measurement, o f f s e t 1 f o o t p e r p e n d i c u l a r t o t h e r i g h t s i d e of t h e sampling p l a n e . Measure through r o t t e n logs whose c e n t r a l a x i s is i n t h e d u f f l a y e r ( f i g . 6) . Yes= center of log is duff layer or below. No= center of log is above duff layer. Figure 6.--Duff depth i s measured through a r o t t e n Zog when i t s centraZ a x i s Zies i n or b e l m the d u f f . Step 8: Measure or estimate the d i m e t e r s o f a l l p i e c e s 3 i n c h e s i n diameter and l a r g e r t h a t i n t e r s e c t t h e sampling p l a n e . Measure t h e diameters a t t h e p o i n t o f i n t e r s e c t i o n t o t h e n e a r e s t whole i n c h . Record d i a m e t e r s s e p a r a t e l y f o r r o t t e n and n o n r o t t e n p i e c e s . Consider p i e c e s r o t t e n when t h e p i e c e a t t h e i n t e r s e c t i o n i s obviously punky o r can be e a s i l y kicked a p a r t . A r u l e r l a i d p e r p e n d i c u l a r l y a c r o s s a l a r g e p i e c e of f u e l works s a t i s f a c t o r i l y f o r measuring diameter. Be s u r e t o avoid p a r a l l a x i n r e a d i n g t h e r u l e r . C a l i p e r s a l s o work w e l l f o r measuring d i a m e t e r . A diameter t a p e , however, i s u n s a t i s f a c t o r y f o r p i e c e s i n c o n t a c t w i t h t h e ground. Use a s many c o n s e c u t i v e l i n e s on t h e d a t a form ( s e e page 14) a s n e c e s s a r y t o r e c o r d diameters. Step 9 : For the entire s q l e area, record the pcedominate species o f t h e 0- t o 1-inch-diameter branchwood. An average diameter f o r t h e 0- t o 0.25-inch, and 0.25- t o 1-inch s i z e c l a s s e s w i l l be s e l e c t e d from t h i s information. I f s e v e r a l s p e c i e s comprise t h e downed d e b r i s , e s t i m a t e t h e p r o p o r t i o n o f t h e two o r t h r e e most common s p e c i e s . Base t h i s e s t i m a t e on a g e n e r a l impression o f what e x i s t s on t h e sample a r e a and r e c o r d a s p e r c e n t a g e s o f t o t a l 0- t o 1-inch branchwood. O r , f o r a s l i g h t r e d u c t i o n i n accuracy, omit t h i s s t e p and i n t h e c a l c u l a t i o n s u s e an average diameter f o r a composite o f s p e c i e s (page 16) T m L Y RULES The f o l l o w i n g r u l e s apply t o downed woody p i e c e s o f a l l d i a m e t e r s : 1. P a r t i c l e s q u a l i f y i n g f o r t a l l y i n c l u d e domed, dead woody m a t e r i a l ( t w i g s , stems, branches, and bolewood) from t r e e s and s h r u b s . Dead branches a t t a c h e d t o b o l e s o f s t a n d i n g t r e e s a r e omitted because t h e y a r e n o t downed v e g e t a t i o n . Consider a p a r t i c l e downed when it has f a l l e n t o t h e ground o r i s s e v e r e d from i t s o r i g i n a l s o u r c e of growth. Cones, b a r k f l a k e s , n e e d l e s , l e a v e s , g r a s s , and f o r b s a r e n o t counted. Dead woody stems and branches s t i l l attached t o standing brush and trees are not counted. 2 . Twigs o r branches l y i n g i n t h e l i t t e r l a y e r and abdve a r e counted. However, t h e y a r e n o t counted when t h e i n t e r s e c t i o n between t h e c e n t r a l a x i s o f t h e p a r t i c l e and t h e sampling p l a n e l i e s i n t h e duff ( f o r e s t f l o o r below the l i t t e r ) (fig. 7). Does Not Qualify Figure 7.--Regardless o f s i z e , pieces are t a l l i e d only when i n t e r section l i e s i n and above the l i t t e r ( r i g h t of arrow). 9 3. I f t h e sampling plane i n t e r s e c t s t h e end o f a p i e c e , t a l l y only i f t h e c e n t r a l a x i s i s c r o s s e d ( f i g . 8 ) . I f t h e plane e x a c t l y i n t e r s e c t s t h e c e n t r a l a x i s , t a l l y every o t h e r such p i e c e . 0 YES # NO Sampling Planes F i p r e 8.--An i n t e r s e c t i o n a t the end of a brnnch or log must include the central axis t o be t a l l i e d . 4 . Don1t t a l l y any p a r t i c l e having a c e n t r a l a x i s t h a t coincides p e r f e c t l y with t h e sampling plane. (This should r a r e l y happen.) 5. I f t h e sampling plane i n t e r s e c t s a curved p i e c e more than once, t a l l y each i n t e r s e c t i o n ( f i g . 9 ) . Figure 9.--Count both intersections for a curved piece. 6. T a l l y wood s l i v e r s and chunks l e f t a f t e r logging. V i s u a l l y mold t h e s e p i e c e s i n t o c y l i n d e r s f o r determining s i z e c l a s s o r recording diameters. 7. T a l l y uprooted stumps and r o o t s n o t encased i n d i r t . For t a l l y i n g , c o n s i d e r uprooted stumps a s t r e e b o l e s o r i n d i v i d u a l r o o t s , depending on where t h e sampling planes i n t e r s e c t t h e stumps. Do n o t t a l l y undisturbed stumps . 8. For r o t t e n logs t h a t have f a l l e n a p a r t , v i s u a l l y c o n s t r u c t a c y l i n d e r c o n t a i n i n g t h e r o t t e n m a t e r i a l and e s t i m a t e i t s diameter. The c y l i n d e r w i l l probably be s m a l l e r i n diameter t h a n t h e o r i g i n a l log. 9. Be s u r e t o look up from t h e ground when sampling because downed m a t e r i a l can b e . t a l l i e d up t o any h e i g h t . A p r a c t i c a l upper c u t o f f is about 6 f e e t . However, i n deep s l a s h it may b e necessary t o t a l l y above 6 f e e t . When s t a n d i n g t r e e s a r e i n v e n t o r i e d along with downed m a t e r i a l , i t i s necessary t o f i x a limit above t h e ground f o r sampling downed m a t e r i a l . An upper l i m i t h e l p s d e f i n e a owned t r e e s o t h a t inventory of s t a n d i n g and downed m a t e r i a l s w i l l not overlap.- 13 HEAVY SLASH OPTIOIVS 1. A y a r d s t i c k a t t a c h e d t o a J a c o b ' s s t a f f i s u s e f u l f o r marking t h e sampling E r e c t t h e Jacob Is s t a f f plane and speeds t h e counting of small p a r t i c l e s ( f i g . 10) a t t h e sample p o i n t . Aline t h e y a r d s t i c k with t h e d i r e c t i o n o f t h e sample plane and l e v e l i t u s i n g an a t t a c h e d bubble l e v e l . . :gure 10. --A yardstick or meter s t i c k attached t o a Jacob ' s s t a f f defines the sampling plane i n heavy slash. 2 . I n a r e a s with c o n s i d e r a b l e s l a s h , sampling e f f i c i e n c y i s improved by o c u l a r l y e s t i m a t i n g t h e number o f 0- t o 0.25-inch i n t e r s e c t i o n s and a c t u a l l y counting t h e number o f i n t e r s e c t i o n s a t a subsample of p o i n t s . The o c u l a r - e s t i m a t e s a r e a d j u s t e d using t h e r a t i o o f o c u l a r e s t i m a t e s - t o - a c t u a l counts. This method, i n c o r p o r a t i n g 3P sampling, i s described i n d e t a i l by Beaufait and o t h e r s (1974). ~ / 1 nt h e USDA Forest S e r v i c e Northern Region, a r u l e has been e s t a b l i s h e d t h a t a stem is "downed" and thus q u a l i f i e s f o r t a l l y i n g when t h e i n t e r s e c t i o n o f t h e sampling plane and c e n t r a l a x i s is 6 f e e t o r l e s s from t h e ground. I f t h e midpoint o f t h e b o l e i s more than 6 f e e t above ground f o r t r e e s encountered i n f i x e d and v a r i a b l e r a d i u s p l o t s , they a r e i n v e n t o r i e d a s "standing. l 1 For each sampling plane, e s t i m a t e t h e p r o p o r t i o n o f 0- t o 1-inch-diameter 3. branchwood t o t h e n e a r e s t 10 p e r c e n t f o r t h e t h r e e most common s p e c i e s . UTILIZATION OPTIONS For p i e c e s over 3 inches i n diameter, t h e following a d d i t i o n a l measurements can be useful f o r describing u t i l i z a t i o n potential : 1. 2. 3. 4. Species Length o f p i e c e Diameter a t l a r g e end Degree o f checking, r o t , and o t h e r d e f e c t s t h a t apply t o t h e e n t i r e p i e c e . - Item Field Equipment Hand compass Gaming d i e 50-foot t a p e o r s t r i n g and one chaining p i n P l o t rod Go-No-Go gage ( f i g . 11) 1-foot r u l e r o r s t e e l pocket t a p e Hypsometer with p e r c e n t s c a l e Sample forms For s l a s h : Jacob I s s t a f f with a t t a c h e d yard o r meter s t i c k and l e v e l Use Transect and p l o t l a y o u t . Random o r i e n t a t i o n o f sampling p l a n e s . Delineate t h e sampling p l a n e s . Delineate sampling p l a n e s and i f c a l i b r a t e d , measure f u e l depth. Determine s i z e c l a s s o f b o r d e r l i n e particles. Measure duff depth and diameters o f p i e c e s over 3 i n c h e s . Fuel depth could b e measured with s t e e l pocket tape. Slope measurement. Record d a t a . Delineate sampling plane f o r counting small p a r t i c l e s . Figure 11 .--A Go-No-Go gage ean be cut from 1/26 or 1/8-inch sheet aluminum. Cut the notches s l i g h t Zy t i g h t and fiZe smooth t o f i n a l dimensions. CALCULATIONS and a r e a l s o easy u s i n g a The c a l c u l a t i o n s can be r e a d i l y processed by computer:/ Sample c a l c u l a t i o n s a r e shown i n f i g u r e s 12 and 13. For a given desk c a l c u l a t o r s t a n d o r sample a r e a , f i l l i n t h e computation summary s h e e t a s follows: . 1. C a l c u l a t e t h e average s l o p e c o r r e c t i o n f a c t o r (c) u s i n g s l o p e c o r r e c t i o n f a c t o r s f o r each sampling p l a n e . Look up t h e c o r r e c t i o n f a c t o r s i n t a b l e 1 o r compute them by: No s l o p e c o r r e c t i o n i s needed f o r samples taken u s i n g t h e J a c o b ' s s t a f f . Table 1. --Slope correction factors for converting weight/acre on a slope basis t o a horizontal basis : S1ope Correction factor Percent c 0 10 20 30 40 50 1.00 1.00 1.02 1.04 1.08 1.12 : Slope Percent 60 70 80 90 100 110 Correction factor c 1.17 1.22 1.28 1.35 1.41 1.49 - :/card punching i n s t r u c t i o n s and a FORTRAN program f o r computing t h e i n v e n t o r y r e s u l t s a r e a v a i l a b l e upon r e q u e s t from t h e Northern F o r e s t F i r e Laboratory, Drawer G , Missoula, Montana 59801. DOWNED FUEL INVENTORY L I;Y)WST I BLOCK COMPlUT!m SUL3COMPN<rIMT;S\Tr ASPECT STAND ELEVATION COVER TYPE SIZE CLASS ( I n . ) HABITAT TYPE - 3+ I 10 .35 FUEL DEPTH 3+ DI- DUFF DFSTH INTERSECTS I 1 - 3 I 6 LENGTH OF SAMPLING PLANE ( ~ t . 1 : r NO. OF 1 0 - 1 : w -* 0 Z rl d = I M 3 i @ r-t E l m r - N 0 p a 3 a , 3 mQm CG 3 4 ? 13 I I/ 1/17 , I : , I I 4 I 1 I I I ,2 5 I ,g 1 2 10 I ,!? I 1'7 I L /I@ 13 12 1 5 i 4 U 3 2l 2 i 2 a e Q 215 / , O I 1 I I I I l o 13 I I I I I I 1 I I I 1 I I I I I I I I 1 I I I I 1 I I I I I 1 1 I I 1 I I 1 I I I I I I I I 1 8 I I 1 I i I 1 I I I I I I I I I 1 I I I I I I i 1 I I I I I I 1 I 1 I I 1 I I I I 4 I : I I 1 I , , I I 1 I I I I I 1 I I 1 I 1 i I I i I I I 1 I I I I 1 I I I I I I 4 1 I i I 1 I I 1 I I I I I 4 t I I 1 I I t I ' 4 1 I 1 I I I I I 1 I I 1 1 I I I 1 I I I I I I I I 1 I I I I I I I I I I I I I I 1 1 I I L 1 1 I I I I I I 1 I 1 I L 1 I I I 1 1 I I I I I I 1 1 I 1 1 . I I I I I I I I I I 1 I I I I I I L I I 1 I I I I 1 I I I I 1 I 1 I I I 1 I I I I I 1 I I 1 I I 1 I I I I I I I I I 1 Figure 12. --Sample data f o m . 14 1 I I I I I , I DOWNED WOODY FOREST : MATERIAL COMPUTATION COMPAR'MENT: SUMMARY STAND : Formulas t o compute tons/acre: (A) 0- t o 3-inch m a t e r i a l : (B) 3+-inch m a t e r i a l Size class Constant = . 11.64 X n X d2 X s X a X c Na ,11.64X~d~XsXaXc NJI Tons/ acre I 1d2 f o r 3+ 3+ Sound 3/7 3+ Rotten 76 3 Sum o f 3+-inch diameters sound : Rotten : 3+ Sound & Rotten = IV + V = Total = I + I1 + 111 + VI = Number of pieces Average diameter 3-3 L 8. 25 in. 37 2 18.5 i n . Sum o f duff depths : : 3- Number observations : 9 Average duff depths : . / in. Sum of f u e l depths : Number observations : in. Figure 13. --Computation summary sheet. Average f u e l depths : 45) -4 6 .7 in. in. The input values are from figure 12. 15 2 . T o t a l t h e number o f i n t e r s e c t i o n s [n) o v e r a l l sample p o i n t s f o r each of t h e 0- t o 0.25-inch, 0.25- t o 1 - i n c h , and 1- t o 3-inch s i z e classes.?/ 3. From t a b l e 2, e n t e r t h e a p p r o p r i a t e squared average d i a m e t e r s (d2) f o r each s i z e c l a s s on t h e computation s h e e t . I f s p e c i e s composition -has been determined, c a l c u l a t e an average d2 a s : Where P1, P2, and P3 a r e p e r c e n t a g e s f o r composition o f t h e s p e c i e s recorded i n Step 9 (page 9) * I f s e v e r a l s p e c i e s a r e p r e s e n t and t h e i r composition unknown, t h e composite d2 v a l u e s can b e used a s approximate averages. Table 2 . - -Squared average-quadratic-mean d i a m e t e r s f o r nons Zash and s l a s h ground f u e l s Size class (inches) Nons l a s h . : Cover t y p e y Slash Average d2 speciesl/ : Average d2 Inches 0 - 0.25 - 0.25 1 - 3 1 -Tnches2 PP LP S, DF, AF, C L Composite 0.0342 .0201 ,0122 .0149 .0151 PP, LP L DF, GF, C , S ~om~osite~l 0 .0248 .0149 ,0122 .0151 LP S, DF, AF, C L , PP Composite ,344 .304 .238 .2 89 PP, C DF, GF, LP, L , S Composit e .317 .278 .2 89 PP, AF S, DF, C , LP L Composite 3.12 2.87 2.17 2.76 LP DF, PP, GF L , c, s Composite 3.50 2.83 2.30 2.76 v ~ ~ = ~ o n d e r poi n s ea (Pinus ponderosa) ; LP=lodgepole p i n e (Pinus contorts) ; S=Engelmann s p r u c e ( P i c e a enge Zmannii) ; DF=Douglas - f i r {Pseudotsuga m e n z i e s i i ) ; L=west e r n 1a r c h I L m i x o c c i d e n t a Z i s ) ; GF=grand f i r (Abies g r a n d i s ) ; C=west e r n r e d c e d a r (Thuja p l i c a t a ) ; AF=subalpine f i r (Abies Z a s i o c a r ~ a ) 21~11composite v a l u e s a r e averages of nonslash and s l a s h f u e l s with each cover t y p e and s 2 e c i e s weighted e q u a l l y . L . 3/For c a l c u l a t i n g s t a n d a r d e r r o r s o f t h e e s t i m a t e , t h e number o f i n t e r s e c t i o n s (step-2) and t h e sum o f squared diameters (Step 7) must be recorded f o r each p l o t . 16 4 . Determine s p e c i f i c g r a v i t y ( s ) o f m a t e r i a l s from known s o u r c e s o r from l a b o r a t o r y s t u d i e s . Approximate s p e c i f i c g r a v i t i e s f o r c o n i f e r s a r e : Diameter c l a s s (inches) : 0-0.25 Specific gravity : 0.48 0.25-1 1-3 3+Sound 3+Rotten 0.48 0.40 0.40 0.30 Decay and v a r i a b i l i t y i n d e n s i t y make t h i s v a r i a b l e d i f f i c u l t t o handle w i t h accuracy. More a c c u r a t e e s t i m a t e s f o r l a r g e sound m a t e r i a l can be o b t a i n e d by u s i n g s p e c i f i c g r a v i t i e s from t h e USDA F o r e s t S e r v i c e (1955) Wood Handbook. S p e c i a l s t u d i e s , as shown i n Appendix 11, a r e needed t o improve accuracy f o r t h e o t h e r p a r t i c l e c a t e g o r i e s . 5. For s l a s h , determine t h e n o n h o r i z o n t a l angle c o r r e c t i o n f a c t o r s (a) from t a b l e 3 . For nonslash f u e l s , u s e t h e following c o r r e c t i o n f a c t o r s based on a composite o f western s p e c i e s : 0 t o 3 inches: 1.13 3+ i n c h e s : 1.00 The c o r r e c t i o n f a c t o r a d j u s t s weight e s t i m a t e s f o r t h e f a c t t h a t a l l p a r t i c l e s do n o t l i e h o r i z o n t a l l y a s assumed i n t h e p l a n a r i n t e r s e c t t h e o r y . Table 3. --Average secant o f nonhorizontal p a r t i c l e angles for eorreeting orientation bias for s lash Size class : speciesL/ (inches) 0 t o 0.25 PP Others 0.25 t o 1 PP Others Fresh slash Average : 1 (a) -yearand : olderslash PP Others A l l (an assumption) 1.00 1.00 l/~~=~onderp o isnae ; Others=based on d a t a f o r Douglas- f i r , lodgepole p i n e , Engelmann s p r u c e , western r e d c e d a r , western l a r c h , and grand f i r . 6 . C a l c u l a t e t h e t o t a l l e n g t h of samplin2 l i n e (NR) f o r each s i z e c l a s s : NR = number of sample p o i n t s m u l t i p l i e d by l e n g t h of sampling p l a n e ( f e e t ) . 7. For m a t e r i a l 3 i n c h e s and l a r g e r , s q u a r e t h e diameter o f each i n t e r s e c t e d p i e c e and sum t h e squared v a l u e s (zd2) f o r a l l p i e c e s i n t h e sampled area..?./ Compute L'd2 s e p a r a t e l y f o r sound and r o t t e n c a t e g o r i e s . To o b t a i n weights o r volumes f o r c e r t a i n d i a m e t e r ranges ( 3 t o 9 i n c h e s , f o r example) , compute 1d2 f o r t h e s p e c i f i e d range. 8. C a l c u l a t e t h e sum of d i a m e t e r s f o r a l l i n t e r s e c t e d p i e c e s 3 i n c h e s and l a r g e r ( c a l c u l a t e sound and r o t t e n m a t e r i a l s s e p a r a t e l y ) . 9. C a l c u l a t e t h e sum of a l l measurements f o r d u f f d e p t h . 1 0 . C a l c u l a t e t o n s / a c r e , u s i n g formulas on t h e computation s h e e t ( f i g . 13) d e s i r e d , c a l c u l a t e volumes : Cubic f e e t p e r a c r e = 11. If grzvity 32.05 x t o n s Specific e r acre C a l c u l a t e average d i a m e t e r s o f i n t e r s e c t e d p i e c e s 3 inches and 1-arger. 12. C a l c u l a t e average f u e l depth and duff depth a s t h e sum o f t h e depths d i v i d e d by t h e number o f measurements. 13. Appendix I11 shows how t o c a l c u l a t e n e e d l e q u a n t i t i e s i n s l a s h . When i n v e n t o r y i n g l a r g e a r e a s t h a t hold many s p e c i e s i t i s p r a c t i c a l t o use composite v a l u e s and approximations f o r d i a m e t e r s , s p e c i f i c g r a v i t i e s , and n o n h o r i z o n t a l c o r r e c t i o n s . For example, a t i m b e r management and downed-debris i n v e n t o r y i n t h e Northern Region of t h e USDA F o r e s t S e r v i c e u t i l i z e s composite average d i a m e t e r s , comp o s i t e average n o n h o r i z o n t a l c o r r e c t i o n f a c t o r s , and b e s t approximations f o r s p e c i f i c gravities. For t h e Northern Region i n v e n t o r y , t h e formulas i n f i g u r e 13 s i m p l i f y t o : 1. 0- t o 0.25-inch s i z e c l a s s : w = 0.09533 nc/NR 2. 0.25- t o 1-inch s i z e c l a s s : w = 1.825 nc/NR 3. 1- t o 3-inch s i z e c l a s s : w = 14.52 nc/NR 4. 3+-inch sound : w = 4.656 cd2c/N!L 5. 3+-inch r o t t e n : w = 3.492 1d2c/N!L where : w = weight, t o n s / a c r e . - he formulas i n c o r p o r a t e an i n s i g n i f i c a n t b i a s because n , z d 2 , and c a r e t o t a l e d s e p a r a t e l y . Summing n x c o r ~d~ x c o v e r a l l p l o t s would e l i m i n a t e t h e b i a s e s ; howe v e r , t h i s i s u n n e c e s s a r i l y troublesome. FURTHER APPLICATIONS I f only d e b r i s l a r g e r than 3 o r 4 inches i n diameter i s t o b e i n v e n t o r i e d , t h e l i n e i n t e r s e c t technique d e s c r i b e d by Howard and Ward (1972) and Bailey (1969) might be more a p p r o p r i a t e than t h e p l a n a r i n t e r s e c t method, e s p e c i a l l y i n logging s l a s h . The l i n e i n t e r s e c t method employs a few long sampling planes; t h e p l a n a r i n t e r s e c t method employs many small sampling p l a n e s . I f d e b r i s both g r e a t e r t h a n and l e s s t h a n 3 o r 4 inches i n diameter must be i n v e n t o r i e d , t h e p l a n a r i n t e r s e c t technique i s more e f f i c i e n t . The p l a n a r i n t e r s e c t technique can a l s o be coordinated with o t h e r measurements o f v e g e t a t i o n taken on p l o t s ( f o r example, an inventory of timber volume) . The procedures i n t h i s Handbook can be a p p l i e d t o downed d e b r i s i n a r e a s o t h e r than t h e western United S t a t e s by assuming o r measuring average diameters f o r t h e t h r e e s i z e c l a s s e s of p a r t i c l e s . Average diameters have been determined f o r r e d p i n e (Pinus r e s i n o s a ) , jack p i n e (Pinus banksiana) , and oak (Quercus spp. ) (Brown and A convenient method f o r e s t i m a t i n g s l a s h weights o f s e v e r a l Lake Roussopoulos 1974) S t a t e s t r e e s p e c i e s has been r e p o r t e d by Roussopoulos and Johnson (1973). . If f i r e behavior i s t o b e mathematically modeled using models such a s Rothermells (l972), weights of o t h e r f i n e f u e l s such as needle l i t t e r , dead g r a s s , and dead f o r b s a l s o should b e determined by sampling o r by e x t r a p o l a t i n g from e x i s t i n g information. Sampling f o r q u a n t i t i e s o f g r a s s , f o r b s , and l i t t e r r e q u i r e s methods o t h e r than t h e p l a n a r i n t e r s e c t technique (USDA F o r e s t S e r v i c e 1959; Brown 1966; Hutchings and Schmautz 1969). Because p r a c t i c a l methods o f inventory have been lacking i n t h e p a s t , accumulat i o n s o f downed f u e l and d e b r i s have been described i n vague terms such a s " l i g h t , " "medium,11 and llheavy.ll Using t h e simple f i e l d procedures i n t h i s Handbook, weight and volume of downed woody m a t e r i a l can be i n v e n t o r i e d t o provide an o b j e c t i v e b a s i s f o r managing d e b r i s . LITERATURE CITED B a i l e y , G . R. 1969. An e v a l u a t i o n o f t h e l i n e - i n t e r s e c t method of a s s e s s i n g logging r e s i d u e . Can. Dep. F i s h . 6 For., For. Prod. Lab. I n f . Rep. VP-X-23, 41 p. B e a u f a i t , William R . , Michael A . Marsden, and Rodney A . Norm 1974. I n v e n t o r y o f s l a s h f u e l s u s i n g 3P subsampling. USDA For. S e r v . Gen. Tech. Rep. INT-13, 17 p . , i l l u s . Brown, J . K . 1966. F o r e s t f l o o r f u e l s i n r e d and jack p i n e s t a n d s . USDA For. S e r v . Res. Note NC-9, 3 p. Brown, James K . 1971. A p l a n a r i n t e r s e c t method f o r sampling f u e l volume and s u r f a c e a r e a . For. S c i . 17(1) :96-102, i l l u s . Brown, James K . 1972. F i e l d t e s t o f a r a t e - o f - f i r e - s p r e a d model i n s l a s h f u e l s . USDA For. S e r v . Res. Pap. INT-116, 24 p . , i l l u s . Brown, James K . , and P e t e r J . Roussopoulos E l i m i n a t i n g b i a s e s i n t h e p l a n a r i n t e r s e c t method f o r sampling small f u e l volumes. For. S c i . ( I n p r e s s . ) Deeming, John E . , James W . L a n c a s t e r , Michael A. Fosberg, R . William Furman, and Mark J . Schroeder 1972. N a t i o n a l f i r e - d a n g e r r a t i n g system. USDA For. Serv. Res. Pap. RM-84, 165 p . Fahnestock, G. R. 1960. Logging s l a s h f l a m m a b i l i t y . USDA For. Serv. Res. Pap. INT-58, 67 p . , i l l u s . Fosberg, Michael A. 1970. Drying r a t e s o f heartwood below f i b e r s a t u r a t i o n . For. S c i . 16 (1) : 57-63, i l l u s . Howard, James O., and F r a n k l i n R. Ward 1972. Measurement o f logging r e s i d u e - - a l t e r n a t i v e a p p l i c a t i o n s of t h e l i n e i n t e r s e c t method. USDA For. Serv. Res. Note PNW-183, 8 p. Hutchings , S. S , and J E Schmautz 1969. A f i e l d t e s t o f t h e r e l a t i v e - w e i g h t - e s t i m a t e method f o r determining herbage p r o d u c t i o n . J . Range Manage. 22:408-411. Roussopoulos, P . J . , and V. J . Johnson 1973. E s t i m a t i n g s l a s h f u e l loading f o r s e v e r a l Lake S t a t e s t r e e s p e c i e s . USDA For. Serv. Res. Pap. NC-88, 8 p. Rothermel, R. C . 1972. A mathematical model f o r p r e d i c t i n g f i r e s p r e a d i n w i l d l a n d f u e l s . USDA For. Serv. Res. Pap. INT-115, 40 p . , i l l u s . Van Wagner, C . E . 1968. The l i n e i n t e r s e c t method i n f o r e s t f u e l sampling. For. S c i . 1 4 ( 1 ) : 20-26, i l l u s . USDA F o r e s t S e r v i c e 1955. Wood Handbook No. 72, 528 p . For. Prod. Lab., Madison, Wis. USDA F o r e s t S e r v i c e 1959. Techniques and methods o f measuring u n d e r s t o r y v e g e t a t i o n . Southern and S o u t h e a s t For. Exp. S t n . Symp. P r o c . , 174 p. . \ . . APPENDIX I Sampling Intensities NUMBER AND S I Z E OF SAMPLING FLANES Sampling p r e c i s i o n can be c o n t r o l l e d by a l t e r i n g t h e number of p l o t s and l e n g t h o f sampling p l a n e s . As a g e n e r a l r u l e , t h e more downed m a t e r i a l on an a r e a , t h e fewer t h e number and s h o r t e r t h e l e n g t h o f sampling p l a n e s r e q u i r e d t o achieve a given l e v e l o f p r e c i s i o n . F i g u r e 1 4 , based on average sampling v a r i a t i o n f o r number of i n t e r s e c t i o n s o f 0- t o 1-inch and 1- t o 3-inch p a r t i c l e s , can h e l p i n choosing number o f p l o t s and l e n g t h o f sampling p l a n e s . The d a t a f o r f i g u r e 14 a r e from many s t a n d s o f v a r y i n g composition and downed d e b r i s accumulations i n n o r t h e r n Idaho and western Montana. Curves f o r a l l m a t e r i a l under 3 inches i n diameter would f a l l between t h o s e f o r t h e 0- t o 1-inch and 1- t o 3:inch c l a s s e s . P e r c e n t e r r o r s o f 20 p e r c e n t o r l e s s a r e probably adequate l e v e l s o f p r e c i s i o n f o r a s s e s s i n g most f u e l problems. P e r c e n t e r r o r i s t h e s t a n d a r d e r r o r of t h e e s t i m a t e d i v i d e d by t h e mean e s t i m a t e and expressed as a p e r c e n t a g e . More p r e c i s i o n , such a s p e r c e n t e r r o r s o f 10 t o 15 p e r c e n t , may be d e s i r a b l e f o r e v a l u a t i n g u t i l i z a t i o n potent i a l o f downed woody m a t e r i a l . P r e c i s i o n i s maximized u s i n g a d i f f e r e n t l e n g t h o f sampling c l a s s . However, c o n s i d e r i n g b o t h f i e l d e f f o r t and p r e c i s i o n , it u s e t h e same plane l e n g t h f o r sampling t h e 0- t o 0.25- and 0.25The f o l l o w i n g s u g g e s t i o n s w i l l h e l p determine t h e most e f f i c i e n t sampling p l a n e s f o r a given a r e a : p l a n e f o r each s i z e i s more e f f i c i e n t t o t o 1-inch c l a s s e s . number and l e n g t h o f 1. Record d a t a from about 20 sampling p l a n e s i n an a r e a and c a l c u l a t e t h e v a r i a t i o n f o r guiding f u r t h e r sampling. 10 20 30 40 50 60 70 80 90 100 110 Number of sample points Figure 14.--Percent errors for number of particle intersections along 6- and 22-foot-length sampZing planes related t o number o f sample points for quant i t i e s of l i g h t slash and nonslash. Percent error i s 2OOX (standard error of the estimate divided by the mean estimate). 2. For m a t e r i a l l a r g e r t h a n 3 i n c h e s i n d i a m e t e r , t h e sampling p l a n e should b e long en ough s o t h a t on t h e average a t l e a s t one i n t e r s e c t i o n occurs w i t h t h r e e - f o u r t h s o r more of t h e p l a n e s . A l a r g e sampling v a r i a n c e r e s u l t s when many zeros a r e recorded f o r i n t e r s e c t i o n s . I n a r e a s where v e r y l i t t l e downed m a t e r i a l e x i s t s , sampling p l a n e s should a c t u a l l y b e one t o s e v e r a l hundred f e e t long t o p r o v i d e r e s p e c t a b l e p r e c i s i o n . Where many sampling p l a n e s have z e r o e n t r i e s , o t h e r methods such a s measurement of l e n g t h and d i a m e t e r o f a l l downed p i e c e s may be t h e most e f f i c i e n t method of i n v e n t o r y . 3 . The number and l e n g t h o f sampling p l a n e s should be chosen s o t h a t f o r a p i e c e s i z e of i n t e r e s t , such a s m a t e r i a l over 3 inches i n diameter, a t l e a s t 35 t o 50 i n t e r s e c t i o n s occur o v e r an e n t i r e sampled a r e a . SAMPLING PRECISION FOR DEPTH MEASUREMENTS To achieve p e r c e n t e r r o r s of 15 and 20 p e r c e n t u s i n g two-stage sampling, t h e most e f f i c i e n t number o f secondary sampling u n i t s appears t o be t h r e e f o r f u e l depth and two f o r d u f f depth ( f i g . 1 5 ) . The d a t a f o r f i g u r e 15 r e p r e s e n t average v a r i a t i o n from sampling a wide v a r i e t y o f f o r e s t and downed f u e l c o n d i t i o n s i n n o r t h e r n Idaho and w e s t e r n Montana. S e v e r a l thousand measurements were t a k e n u s i n g two secondary sample p o i n t s f o r d u f f depth and t h r e e secondary sample p o i n t s f o r f u e l d e p t h . Vegetation q u a l i f y i n g f o r f u e l depth measurements i n c l u d e d a l l dead downed woody m a t e r i a l and dead b r u s h , g r a s s , and f o r b s The d a t a were s u b j e c t e d t o a n a l y s i s o f v a r i a n c e f o r two-stage sampling. . The number of sample p l o t s r e q u i r e d t o a t t a i n a given l e v e l of p r e c i s i o n v a r i e s c o n s i d e r a b l y among d i f f e r e n t a r e a s . For choosing sampling i n t e n s i t i e s f o r s p e c i f i c a r e a s t h e number of primary sample p o i n t s i n f i g u r e 15 could b e a d j u s t e d up o r down c o n s i d e r a b l y , depending on homogeneity o f t h e dead v e g e t a t i o n s t r a t a . S Dead fuel depth f Duff depth Number of secondary sample points Figure 15.--Number of primary and secondary points needed t o achieve percent errors o f 15 and 20 percent for fuel depth and duff depth. APPENDIX II Specific Gravities of Sound Material The s p e c i f i c g r a v i t i e s i n t a b l e 4 a r e based on ovendry weight and a i r d r y volume and can be used f o r c a l c u l a t i o n o f loadings. Table 4 . - - S p e c i f i c gravity of uoody twigs and branehes w i t h bark attached Diameter s i z e c l a s s (cm) Species 110 - 1 :. 1 - 10 o - i 1 1- 3 j 213 - 5 Ponderosa p i n e Douglas-fir Western l a r c h Lodgepole p i n e Engelmann s p r u c e Subalpine f i r Western redcedar 1' William R . B e a u f a i t and Charles E . Hardy. F i r e q u a n t i f i c a t i o n f o r s i l v i c u l t u r a l use. USDA For. S e r v . , I n t e r m t , For. 6 Range Exp. S t n . (In p r e p a r a t i o n . ) 1 Brown (1972). APPENDIX Ill Calculating Needle Quantities Weight o f n e e d l e s can b e determined by m u l t i p l y i n g r a t i o s of needle-to-branchwood weights ( t a b l e 5) times e s t i m a t e d branchwood weight. The e s t i m a t e s i n t a b l e 5 a r e f o r branches having a l l n e e d l e s a t t a c h e d . The d a t a a r e based on e s t i m a t e s o f n e e d l e s and branchwood from t o t a l l i v i n g crowns f o r t r e e s between 2 and 30 i n c h e s d . b . h . Tab l e 5. --Foliage- to-branchwood r a t i o s b a s e d on o v e n d q weight Species : Diameter of branches 0- t o 0.25-inch ; 0- t o 1-inch No. t r e e s sampled Western l a r c h Ponderosa p i n e Western w h i t e p i n e Douglas-fir Western hemlock Engelmann s p r u c e Western r e d c e d a r Lodgepole Grand f i r y - p - /' - - Data by Fahnestock (1960). QGPO 19794W1201475 Headquarters for the Intermountain Forest and Range Experiment Station a r e i n Ogden, Utah. Field Research Work Units a r e maintained in: Boise, Idaho Bozeman, Montana (in cooperation with Montana State University) Logan, Utah (in cooperation with Utah State University) Missoula, Montana (in cooperation with University of Montana) Moscow, Idaho (in cooperation with the University of Idaho) Provo, Utah (in cooperation with Brigham Young University) Reno, Nevada (in cooperation with the University of Nevada)