Unitd Stats Dpartmnt of Agricultur Forst Srvic Pacific Southwst Rsarch Station Rsarch Papr PNW-RP-584 Novmbr 2009 Estimating Abovground Tr Biomass on Forst Land in th Pacific Northwst: A Comparison of Approachs Xiaoping Zhou and Mils A. Hmstrom
Th Forst Srvic of th U.S. Dpartmnt of Agricultur is ddicatd to th principl of multipl us managmnt of th Nation s forst rsourcs for sustaind yilds of wood, watr, forag, wildlif, and rcration. Through forstry rsarch, coopration with th Stats and privat forst ownrs, and managmnt of th National Forsts and National Grasslands, it strivs as dirctd by Congrss to provid incrasingly gratr srvic to a growing Nation. Th U.S. Dpartmnt of Agricultur (USDA) prohibits discrimination in all its programs and activitis on th basis of rac, color, national origin, ag, disability, and whr applicabl, sx, marital status, familial status, parntal status, rligion, sxual orintation, gntic information, political blifs, rprisal, or bcaus all or part of an individual s incom is drivd from any public assistanc program. (Not all prohibitd bass apply to all programs.) Prsons with disabilitis who rquir altrnativ mans for communication of program information (Braill, larg print, audiotap, tc.) should contact USDA s TARGET Cntr at (202) 720-2600 (voic and TDD). To fil a complaint of discrimination, writ USDA, Dirctor, Offic of Civil Rights, 1400 Indpndnc Avnu, SW, Washington, DC 20250-9410 or call (800) 795-3272 (voic) or (202) 720-6382 (TDD). USDA is an qual opportunity providr and mployr. Authors Xiaoping Zhou is a forstr and Mils A. Hmstrom is a rsarch cologist, Forstry Scincs Laboratory, P.O. Box 3890, Portland, OR 97208-3890.
Abstract Zhou, Xiaoping; Hmstrom, Mils A. 2009. Estimating abovground tr biomass on forst land in th Pacific Northwst: a comparison of approachs. Rs. Pap. PNW-RP-584. Portland, OR: U.S. Dpartmnt of Agricultur, Forst Srvic, Pacific Northwst Rsarch Station. 18 p. Liv tr biomass stimats ar ssntial for carbon accounting, bionrgy fasibility studis, and othr analyss. Svral modls ar currntly usd for stimating tr biomass. Each of ths incorporats diffrnt calculation mthods that may significantly impact th stimats of total abovground tr biomass, mrchantabl biomass, and carbon pools. Consquntly, carbon markts, bionrgy projcts, and similar fforts may b affctd. In addition to diffrncs in allomtric quations, th various mthods ar most suitabl for particular gographic scals of analysis. W xamin thr approachs that might b usd for midscal analyss (.g., 25,000 to svral million acrs) and compar th rgional modls with quations dvlopd by Jnkins t al. and with th componnt ratio mthod (CRM). Ths thr mthods produc rlativly similar stimats of total abovground biomass for softwood spcis in Orgon, but substantially diffrnt stimats for th proportion of total biomass that is mrchantabl. For th major softwood spcis in Orgon, th total abovground biomass using th CRM is 3 prcnt lowr than stimats with rgional quations, and th Jnkins modls produc stimats that ar 17 prcnt highr. Howvr, on avrag, th proportion of softwood mrchantabl biomass computd with CRM is about 83 prcnt of th total abovground biomass with littl variation from spcis to spcis, whras rgional modls stimat that 72 prcnt is mrchantabl, and th Jnkins quations stimat that 78 prcnt is mrchantabl. Kywords: Biomass quations, Jnkins quations, componnt ratio mthod, forst invntory.
Estimating Abovground Tr Biomass on Forst Land in th Pacific Northwst: A Comparison of Approachs Introduction Rasonabl mthods for stimating tr biomass and carbon stocks 1 on forst land ar incrasingly important givn concrns of global climat chang, incrasing intrst in bionrgy projcts, and carbon squstration protocols for th voluntary and rgulatd markts. During th last two dcads, scintists in th U.S. Dpartmnt of Agricultur, Forst Srvic hav put considrabl ffort into dvloping modls for stimating tr biomass and carbon stock ovr aras as larg as th ntir Unitd Stats. Howvr, applying thos broad-scal modls to rgional or fin-scal analyss can b challnging. For xampl, broad-scal stimats of mrchantabl tr biomass basd on lumping many spcis may diffr considrably from stimats mad with mor rgionally rprsntativ modls, and th potntial succss of a bionrgy projct might hing on ths diffrncs. Thrfor, undrstanding th potntial altrnativ approachs for stimating forst biomass is vry important for local analyss of biomass supply and forst carbon accounting. W rviw som of th currnt mthods of calculating abovground liv tr biomass that might b usd in th Pacific Northwst and compar th diffrncs whn thy ar applid to Forst Invntory and Analysis (FIA) tr data in Orgon. Th thr most common softwood tr spcis wr analyzd: Douglas-fir (Psudotsuga mnzisii (Mirb.) Franco), wstrn hmlock (Tsuga htrophylla (Raf.) Sarg.), and pondrosa pin (Pinus pondrosa C. Lawson). Currnt Tr Biomass Calculation Mthods Applid on Forst Land in Unitd Stats Various tr biomass calculation mthods ar applid on forst lands in th Unitd Stats dpnding on scal of analysis, nd for dtail, usr group intrst, and purpos. Th USDA Forst Srvic has usd th Jnkins quation systm (Jnkins t al. 2003, 2004) in rcnt yars to assss national-scal biomass and for forst carbon stimats usd in official grnhous gas invntoris of th Unitd Stats (US EPA 2008). Th Jnkins modl was originally dsignd for national-scal biomass stimation, but th diffrncs in quation forms and spcis groupings may caus diffrncs at fin scals dpnding on tr siz and forst spcis composition (Jnkins t al. 2003). Rgional modls ar usually tr spcis-spcific basd on various local tr studis, and rsult in diffrnt biomass stimation modls for 1 In gnral, w calculat biomass to stimat carbon stock (C) and carbon dioxid ( CO2 ) mission quivalnt: 1 unit of biomass = 0.5 unit carbon stord, and 1 unit carbon stord = 3.67 units CO 2 mission quivalnt. 1
RESEARCH PAPER PNW-RP-584 diffrnt FIA rgions. 2 But th rgional modls lack consistnt mthodology and componnt dfinitions, which maks thm difficult to us for national stimats. National consistncy has bcom a prim concrn within FIA (Hansn 2002). Thrfor, th national forst rsourcs rport for th Rsourcs Planning Act has usd th componnt ratio mthod (CRM) to stimat tr biomass for consistncy across rgions, and th CRM approach will b applid to FIA tr data for futur biomass rporting (Hath t al. 2008). Th objctiv of CRM is to gt national biomass and carbon stimats that ar consistnt with FIA tr volum stimats (Hath t al. 2008). Howvr, ths mthods produc gnralizd biomass stimats whn compard to mor local and dtaild allomtric quations. Usrs should undrstand th diffrncs btwn stimats mad with broad-scal mthods and quations compard to rgional rprsntativ quations and choos mthods appropriat to thir qustions and scal of us. Liv tr biomass is gnrally dividd into fiv major componnts, including mrchantabl stm biomass (also calld bol biomass including both bark and wood), stump biomass, foliag biomass, branchs/top biomass, and root biomass. W focus on abovground liv tr biomass stimation including stump, stm, branch, and top. Th Rgional Approach Th rgional volum and biomass modls wr dvlopd spcifically for rgional tr spcis (Waddll and Hisrot 2005). In gnral, ths quations wr from publishd paprs drivd from local tr studis and ar dirct functions of tr diamtr or both diamtr and hight. Diffrnt rgions oftn pick diffrnt functions such as logarithmic vs. linar or quadratic forms to fit local tr spcis. Th FIA Program in th Pacific Northwst Rsarch Station uss sparat sts of quations for bol, branch, and bark biomass. Tr bol biomass is scald dirctly from volum stimats via spcis-spcific wood dnsity factors (USDA FS 1999). For xampl, th suit of quations for lodgpol pin in th Pacific Northwst rgion is: CVTS = 10-2.615591 + 1.847504 log(dbh) + 1.085772 log(ht) (Brackt 1977) BOLE = (CVTS W d ) BRK = 3.2 + 9.1 dbh cm 100 2 HT m (Standish 1985) 2 Th Forst Invntory and Analysis (FIA) Program in th USA has four rgional programs basd on gographical locations: Northrn, Southrn, Rocky Mountain, and Pacific Northwst. 2
Estimating Abovground Tr Biomass on Forst Land in th Pacific Northwst: A Comparison of Approachs BCH = 7.8 + 12.3 dbh cm 100 2 HT m (Standish 1985) BT = BOLE + BRK + BCH whr CVTS = total stm volum from ground to tip (cubic ft), W d = wood dnsity (kg/ft 3 ), 3 BOLE = bol biomass (kg), BRK = bark biomass (kg), BCH = branch biomass (kg), BT = total abovground biomass without foliag (kg) dbh = diamtr at brast hight (in) HT = total hight from ground to th tip (ft) dbh cm = diamtr at brast hight (cm) HT m = total hight from ground to th tip (m) log is th logarithmic function with bas 10. Each tr spcis is associatd with a st of local volum and biomass quations. Although th particular form of th quations may diffr, th biomass calculation of major abovground biomass componnts is similar to that for lodgpol pin spcis. Rgional quations produc biomass stimats spcific to ach spcis and sparatd into major abovground componnts. Thy ar usful for popl intrstd in dtaild rgional stimats and small to midscal studis. Although major tr spcis hav sparat quations by rgion or subrgion, many minor spcis hav no spcis-spcific quations. In such cass, analysts commonly substitut th quations for spcis judgd to hav similar growth forms. In addition, rgional quations may apply only to crtain diamtr rangs, so mor than on bol quation may b ndd for whol-tr stimats for a givn spcis. Consquntly, th stimation using rgional quations is oftn fraught with idiosyncrasis and th nd to rach ad hoc dcisions on quation slction. Thus, thr ar concrns about th consistncy of stimats among rgions, vn among trs of a givn spcis. Th Jnkins Modl Th Jnkins modl (Jnkins t al. 2003, 2004) was dsignd for national-lvl biomass stimation. It uss a st of quations for total abovground biomass basd on tr diamtr. Th componnts of tr biomass for mrchantabl stm wood, stm bark, foliag, and blowground (coars root) biomass ar calculatd 3 This mix of units allows convrsion from volum in cubic ft to mass in kilograms. 3
RESEARCH PAPER PNW-RP-584 as proportions of total abovground biomass. Branch and stump biomass ar calculatd as a rsidual aftr subtracting stm and foliag biomass from total abovground biomass. Th Jnkins mthod was dvlopd by rfitting th data prdictd from various quations found in th litratur for diffrnt tr spcis that catgorizd into th sam spcis group. For xampl, thr ar about 38 tr spcis in th pin spcis group, including pondrosa pin from th Wst, loblolly pin (Pinus tada L.) from th South, and jack pin (Pinus banksiana Lamb.) from th East. Forty-thr publishd quations for spcis in this group wr usd to produc th projction data that wr rfit into on quation for abovground biomass with diamtr as th only indpndnt variabl. Th gnral form of th Jnkins t al. (2003) quations is: B m = (b 0 + b 1 ln(dbh cm )) whr B m = total abovground biomass (kg) for trs largr than 2.5 cm (1 in) in dbh, dbh cm = diamtr in cntimtr (cm) at brast hight, and b 0, b 1 = cofficints. Thr ar 10 abovground biomass quations associatd with 10 tr spcis groups for th Unitd Stats, including 4 hardwood spcis groups, 5 softwood spcis groups, and 1 woodland group. Th cofficints associatd with ach spcis group ar listd in tabl 1. Bcaus thr wr too fw componnt-spcific quations to us th projction data approach for ach biomass componnt (.g., bol, bark, and branchs) in ach of th abov dfind 10 spcis groups, componnt quations wr first poold into hardwood and softwood groups (Jnkins t al. 2003), and projction data wr fit to a simpl quation for ach componnt for ach of ths two gnralizd spcis groups. This rsultd in two sts of quations for stimating fractions (xprssd as ratio) of foliag, stm bark, stm wood, and coars roots in th form (Jnkins t al. 2003): a 0 Ratio i a1 dbhcm whr Ratio i = ratio of i th componnt (foliag, coars roots, stm bark, or stm wood) to total abovground biomass for trs largr than 2.5 cm (1 in) dbh, dbh cm = diamtr (cm) at brast hight, and a 0, a 1 = rgrssion cofficints. 4
Estimating Abovground Tr Biomass on Forst Land in th Pacific Northwst: A Comparison of Approachs Tabl 1 Paramtrs for stimating total abovground biomass for all hardwood and softwood spcis in th Unitd Stats Spcis groups b 0 b 1 Hardwood: Aspn/cottonwood/willow -2.2094 2.3867 Soft mapl/birch -1.9123 2.3651 Mixd hardwood -2.4800 2.4835 Hard mapl/oak/hickory/bch -2.0127 2.4342 Softwood: Cdar/larch -2.0336 2.2592 Douglas-fir -2.2304 2.4435 Tru fir/hmlock -2.5384 2.4814 Pin -2.5356 2.4349 Spruc -2.0773 2.3323 Woodland -0.7152 1.7029 Not: S Spcis List for scintific nams. Sourc: Jnkins t al. 2003 B m = (b 0 + b 1 ln(dbh cm )) whr B m = total abovground biomass (kg) for trs largr than 2.5 cm (1 in) dbh, dbh cm = diamtr (cm) at brast hight, and b 0, b 1 = cofficints. Th paramtrs for th componnt ratios wr stimatd analogously to how cofficints for total abovground biomass wr stimatd (tabl 2). Thr ar two major concrns about th Jnkins modl whn it is usd for finr scal analyss. First, th broad tr spcis groups may lad to biasd biomass stimats for a spcific tr spcis in a rgion whn using th nationally avragd quation. For xampl, about 100 hardwood tr spcis from th East to th Wst ar groupd into on hardwood group. Scond, th quation only has diamtr as an xplanatory variabl, and this fails to account for variation in stm tapr. Ths concrns may caus difficultis if th Jnkins mthods ar usd for midscal analyss. For xampl, bcaus pondrosa pin in th Pacific Northwst is in th sam group as loblolly pin from th South, th Jnkins quations would prdict th sam biomass for a pondrosa pin and loblolly pin tr with a common diamtr vn though thy hav significantly diffrnt stm forms and consquntly quit diffrnt actual biomass for a givn diamtr. Although th Jnkins quations ar simpl and consistnt in format across th Nation, thy may not b sufficintly accurat for mid- to fin-scal analyss. 5
RESEARCH PAPER PNW-RP-584 Tabl 2 Paramtrs for stimating componnt ratios of total abovground biomass for hardwood and softwood spcis in th Unitd Stats Spcis groups a 0 a 1 Hardwood: Foliag -4.0813 5.8816 Coars roots -1.6911 0.8160 Stm bark -2.0129-1.6805 Stm wood -0.3065-5.4240 Softwood: Foliag -2.9584 4.4766 Coars roots -1.5619 0.6614 Stm bark -2.0980-1.1432 Stm wood -0.3737-1.8055 Sourc: Jnkins t al. 2003. a a 1 0 dbhcm Ratio i whr Ratio i = ratio of i th componnt (foliag, coars roots, stm bark or stm wood) to total abovground biomass for trs largr than 2.5 cm (1 in) dbh, dbh cm = diamtr (cm) at brast hight, and a 0, a 1 = rgrssion cofficints. Th Componnt Ratio Mthod Th componnt ratio mthod for stimating abovground liv tr biomass has bn proposd rcntly for consistnt national projction of tr biomass basd on th FIA volum stimats. Dtaild calculation and xampls ar dscribd in Hath t al. (2008). Thr ar four major stps for th currnt CRM calculation for trs largr than 12.5 cm (5 in) dbh: 1. Calculat bas componnts using Jnkins t al. mthods (app. tabl 4) for total abovground biomass, foliag, stm bark, and stm wood. Th stump biomass is calculatd using Rail s approach (1982). Th branch and top biomass ar calculatd by subtracting stm, stump, and foliag biomass from total abovground biomass. 2. Rcast Jnkins t al. componnt biomass from stp on as th ratio of Jnkins bol biomass for trs largr than or qual to 12.5 cm (5 in) (app. tabl 5, fig. 3). In this stp, th proposd CRM will calculat th ratio of ach componnt rlativ to mrchantabl stm (bark and wood) drivd from Jnkins quations shown in stp on: 6
Estimating Abovground Tr Biomass on Forst Land in th Pacific Northwst: A Comparison of Approachs Stump ratio: STPROP = STP/MST Foliag ratio: FLPROP = FOL/MST Branch/top ratio: BTPROP = BRT/MST Root ratio: RTPROP = RTS/MST whr: MST is mrchantabl stm biomass basd on Jnkins (kg), STP is stump biomass with bark basd on Rail (kg), FOL is foliag biomass basd on Jnkins (kg), BRT is branchs/top biomass by subtraction basd on Jnkins t al. (kg), and RTS is root biomass basd on Jnkins (kg). 3. Calculat componnt biomass for FIA-masurd trs using FIA bol biomass multiplid by th ratios from stp two for trs gratr than or qual to 12.5 cm (5 in) in diamtr. Th volum of sound wood 4 in th cntral stm (sound cubic-foot volum) for th masurd FIA trs is usd to stimat th mrchantabl stm woody biomass and thn th componnt biomass. Th componnts ar calculatd as follows: Mrchantabl stm woody biomass (biomass of th bol): MSBIOFIA = VOLCFSND R bark SpG bark 62.4 + VOLCFSND SpG wood 62.4 Stump biomass: STPBIOFIA = STPROP MSBIOFIA Foliag biomass: FOLBIOFIA = FLPROP MSBIOFIA Branchs/top biomass: TOPBIOFIA = BTPROP MSBIOFIA Root biomass: RTSBIOFIA = RTPROP MSBIOFIA whr: VOLCFSND is th volum of sound wood in cubic ft in FIA, R bark is th bark ratio on th bol for givn spcis group (10 Jnkins spcis groups), SpG bark is spcific gravity of bark for a givn spcis, SpG wood is spcific gravity of wood for a givn spcis, and 62.4 = th pur watr wight (lb/ft 3 ). 4. Finally, th total abovground dry biomass xcluding foliag for trs with dbh largr than or qual to 5 in using CRM is stimatd as: DRYBIOT_CRM = MSBIOFIA + STPBIOFIA + TOPBIOFIA 4 Th sound cubic-foot volum is th volum of a sampl tr 5.0 in diamtr or largr from a 1-ft stump to a minimum 4-in top diamtr outsid of bark (dob) or to whr th cntral stm braks into limbs all of which ar lss than 4.0 in dob. 7
RESEARCH PAPER PNW-RP-584 Although this hybrid modl appars promising in concpt as currntly usd, its limitations rsmbl thos of th Jnkins mthod whn usd for mid- and fin-scal analysis. In larg part, this is bcaus th mthod uss only th two sts of cofficints from th Jnkins mthod for componnt ratios. For xampl, th foliag componnt ratios will b th sam for all spcis within softwood or hardwood groups for a givn dbh. Thr ar 10 stump ratio quations and 10 branch/top ratio quations corrsponding to 10 Jnkins spcis groups for total abovground biomass. Howvr, th sum of th stump ratio and branch/top ratio collaps to two gnric softwood and hardwood groups (appndix). Th mrchantabl biomass ratio calculatd with CRM will also b th sam for all softwoods and all hardwoods vn though thy ar basd on th sound volums from individually masurd trs (s appndix for calculation dtails). Comparison of Biomass Estimats Using Masurd Tr Data Ovr 50 tr spcis contribut to total biomass and sound wood volum on FIA plots in Orgon. Douglas-fir, pondrosa pin, and wstrn hmlock ar th most abundant of thos spcis. Douglas-fir contributs about 51 prcnt of total abovground biomass of trs largr than 12.5 cm (5 in) dbh on forst land in Orgon, and wstrn hmlock and pondrosa pin contribut around 8 prcnt ach. Hardwoods contribut a rlativly minor amount to abovground liv tr biomass statwid; mor than 90 prcnt is from softwood spcis. Th diffrncs among biomass stimats using rgional, Jnkins, and CRM mthods bcom obvious whn all thr ar usd to stimat total liv tr abovground biomass and mrchantabl biomass of softwoods in Orgon (fig. 1, tabl 3). Total abovground biomass using CRM is about 3 prcnt lowr than stimats with rgional quations, whras th stimats using Jnkins mthods ar 17 prcnt highr than stimats using rgional quations. Th mrchantabl biomass from softwoods diffrs considrably using ths thr mthods. Rgional quations suggst that mrchantabl softwood biomass is about 72 prcnt of total liv tr abovground biomass (rang 65 to 76 prcnt). Th CRM approach prdicts that about 83 prcnt of th total abovground biomass is mrchantabl (81 to 83 prcnt rang). Estimats from Jnkins quations ar also considrably highr than thos from rgional quations, producing about 78 prcnt of total abovground biomass in mrchantabl biomass (rang 76 to 78 prcnt). 8
Estimating Abovground Tr Biomass on Forst Land in th Pacific Northwst: A Comparison of Approachs 100 Mrchantabl biomass (prcnt) 90 80 70 60 50 40 30 20 10 Rgional Douglas-fir CRM softwoods Rgional wstrn hmlock Jnkins softwoods Rgional pondrosa 0 5 to 7 7 to 9 9 to 11 11 to 13 13 to 15 15 to 17 17 to 19 19 to 21 21 to 29 29 plus Diamtr group (inchs) Figur 1 Mrchantabl biomass as a prcntag of total abovground biomass without foliag in Orgon. CRM = componnt ratio mthod. Tabl 3 Abovground biomass for trs at last 5 inchs dbh on forst land in Orgon by major spcis Rgional Jnkins CRM Mrch to total Spcis Total Mrch Total Mrch Total Mrch Rgional Jnkins CRM - - - - - - - - - - - - - - Million tons - - - - - - - - - - - - - - - - - - - Prcnt - - - - - Douglas-fir 899 684 1,094 858 888 738 76 78 83 Pondrosa pin 153 104 190 148 148 122 68 78 83 Wstrn hmlock 145 98 130 101 135 112 67 78 83 Whit fir 74 43 81 63 62 52 58 78 83 Grand fir 52 37 70 54 54 44 72 78 83 Mountain hmlock 50 35 62 48 48 40 70 78 83 Lodgpol pin 44 31 50 38 47 38 70 76 81 Othr softwood 203 132 216 168 183 150 65 78 82 Total softwood 1,620 1,164 1,893 1,478 1,565 1,296 72 78 83 Not: CRM = Componnt Ratio Mthod, mrch = mrchantabl. Th ratio of mrchantabl to total abovground biomass incrass with diamtr for all thr mthods. Th ratios from CRM and Jnkins quations follow th sam trajctory with littl variation by softwood spcis trs across diamtr classs (fig. 1). In fact, th componnt ratios ar th sam within th group containing all softwood spcis and within th group containing all hardwood spcis for a givn diamtr using th CRM approach (appndix). Convrsly, th ratio changs significantly among spcis across diamtr groups with rgional quations. 9
RESEARCH PAPER PNW-RP-584 Although th CRM stimats show th proportion of mrchantabl biomass to b th sam for all th softwood spcis of a givn diamtr, stimats from rgional quations indicat that mrchantabl biomass diffrs not only by spcis but also by subrgion (fig. 2). For Douglas-fir, th proportion of mrchantabl biomass to total abovground biomass in ast-sid Orgon is lowr than th proportion in wst-sid Orgon bcaus th tr forms and stm tapr in ths two subrgions ar quit diffrnt. Mrchantabl biomass (prcnt) 100 90 80 70 60 50 40 30 20 10 0 5 to 7 7 to 9 9 to 11 11 to 13 13 to 15 Rgional quations, wstrn Orgon CRM Orgon Rgional quations, astrn Orgon Jnkins Orgon 15 to 17 17 to 19 19 to 21 21 to 29 29 plus Diamtr group (inchs) Figur 2 Mrchantabl biomass as a prcntag of total abovground biomass without foliag for Douglas-fir, by subrgion. CRM = componnt ratio mthod. Mrchantabl biomass with CRM is drivd from local mrchantabl volum. Consquntly, on would xpct th stimats of mrchantabl biomass to b similar or at last to paralll th trnds with diamtr, but thy do not. Two major sourcs might contribut to th diffrncs: (1) CRM uss uniform componnt ratios for softwood and hardwood dvlopd from th Jnkins mthod ovr broad spcis groups and (2) 10 bark ratios ar usd in CRM for spcis across th Unitd Stats, potntially lading to biass whn applid to spcis in a smallr ara. Discussion and Conclusion Biomass stimats ar critical for many landscap analysis qustions, including carbon stock accounting and valuating biomass potntially availabl to bionrgy projcts. Th thr mthods rviwd in this papr wr dvlopd for particular purposs and ar applicabl to diffrnt analysis scals. Th Jnkins and th 10
Estimating Abovground Tr Biomass on Forst Land in th Pacific Northwst: A Comparison of Approachs componnt ratio mthods wr targtd at broad-scal analyss across collctions of stats or th ntir Unitd Stats. At thos scals, dtaild information about diffrncs among tr spcis and across smallr gographic aras may not b ncssary for assssmnts of sufficint accuracy to addrss issus. In addition, th many quations usd to calculat biomass locally ar inconsistnt, vn for th sam spcis, across largr aras. Unfortunatly, ths broad-scal mthods may b usd mor gnrally to comput biomass at a varity of scals and may, at last in our xampl, produc biomass stimats that ar significantly diffrnt from local stimats at last for som diamtr classs. W found, in fact, that both th Jnkins and CRM mthods stimat highr mrchantabl biomass, spcially in smallr diamtr classs, compard to stimats mad with rgionally drivd quations. Jnkins and CRM stimat about 11 to 13 prcnt mor mrchantabl volum for softwood biomass in Orgon than th rgional quations. This diffrnc may or may not b significant at th national scal, and to dtrmin this would likly rquir a comprhnsiv comparison using hundrds of rgional quations. Howvr, th diffrncs at local scal, for xampl as whn analyzing th carbon dynamics of a proposd managmnt rgim on an ownrship or watrshd, or assssing a bionrgy projct whr profit margins ar slim, could profoundly affct outcoms. W found that th Jnkins mthods stimatd about 17 prcnt mor liv tr abovground softwood biomass and carbon stock in Orgon compard to that using rgional quations, whras CRM stimats wr about 3 prcnt lowr than rgional stimats. It is unclar to what xtnt carbon flux assssd as stock chang would b biasd by th us of CRM. Although it may b tru that thr is inconsistncy of quation forms and componnt dfinitions among rgions, th rgional modls us th rsults of local spcis studis and publishd quations, which will b mor suitabl for analyss of mid- and fin-scal landscaps. Although th Jnkins quations ar vry simpl and asy to us, th rsults may b mislading whn applid at fin scals. Th CRM is a promising approach and may allviat consistncy problms associatd with rgional quations whil providing rfinmnt to th gnralizd Jnkins approach. Howvr, th currnt CRM procss uss homognous ratios for all softwoods and all hardwoods vn though thy us th locally stimatd volums. Givn th highly variabl form and tapr of diffrnt tr spcis, this simplification ovrstimats biomass for som spcis and undrstimats for othrs. Additional work to includ mor spcis and rgional variability might considrably improv CRM rsults and could provid rasonabl national-scal stimats whil maintaining simplicity and consistncy. In addition, analyss of biomass and carbon at th mid and fin scals (25,000 to svral million acrs) might bttr us locally drivd biomass quations, 11
RESEARCH PAPER PNW-RP-584 spcially if th rsults will b usd to valuat bionrgy projcts or carbon markts whr diffrncs of a fw prcntag points could b important. Acknowldgmnts This work was supportd by funding from th USDA Forst Srvic, Pacific Northwst Rsarch Station. Mtric Equivalnts Whn you know Multiply by: To gt: Acrs (ac) 0.405 Hctars (ha) Ft (ft) 0.305 Mtrs (m) Cubic ft (ft 3 ) 0.0283 Cubic mtrs (m 3 ) Inchs (in) 2.54 Cntimtrs (cm) Pounds (lb) 0.454 Kilograms (kg) Tons 0.907 Mtric tonns Pounds pr cubic foot (lb/ft 3 ) 16.02 Kilograms pr cubic mtr (kg/m 3 ) Spcis List Common nam Scintific nam Aspn Populus grandidntata Michx Bch Fagus L. Birch Btula L. Cdar Chamacyparis Spach Cottonwood Populus L. Douglas-fir Psudotsuga mnzisii (Mirb.) Franco Grand fir Abis grandis (Douglas x D. Don) Lindl. Hickory Carya Nutt. Jack pin Pinus banksiana Lamb. Larch Larix Mill. Loblolly pin Pinus tada L. Lodgpol pin Pinus contorta Douglas x Loudn Mapl Acr L. Mountain hmlock Tsuga mrtnsiana (Bong.) Carrièr Oak Qurcus L. Pondrosa pin Pinus pondrosa C. Lawson Spruc Pica A. Ditr. Tru fir Abis Mill. Wstrn hmlock Tsuga htrophylla (Raf.) Sarg. Whit fir Abis concolor (Gord. & Glnd.) Lindl. x Hildbr. Willow Salix bicolor Fr. 12
Estimating Abovground Tr Biomass on Forst Land in th Pacific Northwst: A Comparison of Approachs Rfrncs Bracktt, M. 1977. Nots on TARIF tr-volum computation. DNR Rp. 24. Olympia, WA: Washington Dpartmnt of Natural Rsourcs. 132 p. Hansn, M. 2002. Volum and biomass stimation in FIA: national consistncy vs. rgional accuracy. In: McRobrts, R.E.; Rams, G.A.; Van Dusn, P.C.; Mosr, J.W., ds. Procdings of th third annual Forst Invntory and Analysis symposium. Gn. Tch. Rp. NC-230. St. Paul, MN: U.S. Dpartmnt of Agricultur, Forst Srvic, North Cntral Rsarch Station: 109 120. Hath, L.S.; Hansn, M.H.; Smith, J.E.; Smith, W.B.; Mils, P.D. 2008. Invstigation into calculating tr biomass and carbon in th FIADB using a biomass xpansion factor approach, In: McWilliams, W.; Moisn, G.; Czaplwski, R., comps. 2008 Forst Invntory and Analysis (FIA) symposium. Proc. RMRS-P-56CD. Fort Collins, CO: U.S. Dpartmnt of Agricultur, Forst Srvic, Rocky Mountain Rsarch Station. [CD ROM]. Jnkins, J.C.; Chojnacky, D.C.; Hath, L.S.; Birdsy, R.A. 2003. National-scal biomass stimators for Unitd Stats tr spcis. Forst Scinc. 49: 12 35. Jnkins, J.C.; Chojnacky, D.C.; Hath, L.S.; Birdsy, R.A. 2004. A comprhnsiv databas of biomass rgrssions for North Amrican tr spcis. Gn. Tch. Rp. NE-319. Nwtown Squar, PA: U.S. Dpartmnt of Agricultur, Forst Srvic, Northastrn Rsarch Station. 45 p. [CD-ROM]. Rail, G.K. 1982. Estimating stump volum. Rs. Pap. NC-224. St. Paul, MN: U.S. Dpartmnt of Agricultur, Forst Srvic, North Cntral Forst Exprimnt Station. 4 p. Standish, J.T.; Manning, G.H.; Dmarschalk, J.P. 1985. Dvlopmnt of biomass quations for British Columbia tr spcis. Information Rport BC-X-264. Canadian Forst Srvic, Pacific Forst Rsourc Cntr. 47 p. Summrfild, E.R. 1980. Volum quations for astrn Washington. Washington Dpartmnt of Natural Rsourcs. Mmo. 3 p. On fil with: Forst Invntory and Analysis Program, Pacific Northwst Rsarch Station, 620 SW Main St., Suit 400, Portland, OR 97205. U.S. Dpartmnt of Agricultur, Forst Srvic [USDA FS]. 1999. Wood handbook wood as an nginring matrial. Gn. Tch. Rp. FPL-GTR-113. Madison, WI: Forst Product Laboratory. 463 p 13
RESEARCH PAPER PNW-RP-584 U.S. Environmntal Protction Agncy [US EPA]. 2008. Invntory of U.S. grnhous gas missions and sinks: 1990 2006. EPA 430-R-08-005. Washington, DC: U.S. Environmntal Protction Agncy, Offic of Atmosphric Program. http://www.pa.gov/climatchang/missions/ downloads/08_cr.pdf (April 2009). Waddll K.L.; Hisrot, B. 2005. Th PNW FIA intgratd databas usr guid and documntation: vrsion 2.0. Intrnal publication. On fil with: Forst Invntory and Analysis Program, Pacific Northwst Rsarch Station, 620 SW Main St., Suit 400, Portland, OR 97205. http://www.fs.fd.us/pnw/ fia/publications/data/data.shtml. (April 2009). 14
Estimating Abovground Tr Biomass on Forst Land in th Pacific Northwst: A Comparison of Approachs Appndix: Th Math Puzzl of th Currnt Proposd Componnt Ratio Mthod (CRM) Th componnt ratios ar th ky for th succss of th proposd componnt ratio mthod (CRM). Th currnt mthod for calculating componnt ratios has som limitations. Excpt for th stump, th componnt ratios of liv tr biomass ar basd on th total abovground tr biomass (TAB) calculatd from Jnkins t al. (2003, 2004) (tabl 4), and ths ratios ar thn applid to mrchantabl stm biomass (MST), which is a subst of th total abovground biomass (tabl 5). Th Jnkins quation for total abovground biomass can b xprssd as: TAB = (b 0 + b 1 ln(dbh)) = b 0dbh b 1 (1) Tabl 4 Equations usd in componnt ratio mthod stp on (biomass in kilograms) Parts Explanation Equations Equation form TAB = Total abovground biomass 10 quations TAB = (b 0 + b 1 ln(dbh)) (mrchantabl stm + top/limbs + stump + foliag) MST = Mrchantabl stm biomass (Jnkins 2 quations MST = [ (b mb0 + b mb1 /dbh + (b mw0 + b mw1 /dbh) ] TAB stm bark ratio TAB + Jnkins stm wood ratio TAB) STP = Stump biomass with bark basd 10 quations STP = b st1 dia 2 [(1 R b ) SG w + R b SG b ] 62.4/2.2 on Rail FOL = Foliag biomass (foliag ratio TAB) 2 quations FOL = [ (b f0 + b f 1 /dbh) ] TAB RTS = Root biomass (root ratio TAB) 2 quations RTS = [ (b r0 + b r1 /dbh) ] TAB BRT = Branchs/top biomass By subtraction BRT = TAB MST STP FOL (TAB MST STP FOL) Not: [b 0 and b 1 ] ar cofficints for stimating abovground biomass (Jnkins) listd in tabl 1. [b mb0, b mb1 ; b mw0, b mw1 ] ar cofficints for stimating biomass of bark and wood (Jnkins) listd in tabl 2 as a 0 and a 1. [b f0 and b f1 ] ar cofficints for stimating foilag biomass (Jnkins) listd in tabl 2 as a 0 and a 1. [b r0 and b r1 ] ar cofficints for stimating root biomass (Jnkins) listd in tabl 2 as a 0 and a 1. dbh is diamtr at brast hight in cntimtrs. [b st1 ] is volum cofficint of stump (Rail). R b is stump bark ratio to total stump volum. dia is diamtr at brast hight in inchs, dia = dbh/2.54. SG is spcific gravity (w = wood, b = bark). 62.4 = wight of watr pr cubic foot (lb/ft 3 ). 15
RESEARCH PAPER PNW-RP-584 Tabl 5 Componnt ratios (stp two) Ratio Explanation Expandd xprssion STPROP Stump ratio = STP/MST STPROP STP ( ( bmb0 bmb1 / dbh) -b0 -b1 dbh ) ( bmw0 bmw1/ dbh) FLPROP Foliag ratio = FOL/MST FLPROP ( bmb0 bmb1 / dbh) ( bf 0 bf1 / dbh) ( bmw0 bmw1/ dbh) BTPROP Branch/top ratio = BRT/MST BTPROP 1 STP ( -b0 ( bmb0 bmb1/ dbh ) dbh -b1 ( bf0 bf1 / dbh ) ( bmw0 bmw1 / dbh ) ) 1 RTPROP Root ratio = RTS/MST RTPROP ( bmb0 bmb1/ dbh) ( br0 br1 / dbh) + ( bmw0 bmw1 / dbh) Not: MST is mrchantabl stm biomass from Jnkins (2003, 2004). STP is stump biomass with bark basd on Rail (1982) (dtail s tabl 4). FOL is foliag biomass. BRT is branchs and top biomass. RTS is root biomass. Dbh is diamtr at brast hight in cntimtrs. Foliag biomass and mrchantabl stm biomass us only two sts of cofficints in th Jnkins stimation, on for softwood and on for hardwood spcis. Consquntly, thr ar only two quations for th foliag componnt ratio of foliag biomass to mrchantabl stm biomass (tabl 5). That is, th sam foliag componnt ratio is applid across all softwood spcis if th trs hav th sam diamtr. Th sam is tru for th hardwood spcis. Stump ratio and branch/top ratio ach hav 10 quations corrsponding to 10 Jnkins spcis groups for total abovground biomass (tabl 5). Howvr, th sum of th stump ratio and branch/top ratio (STPROP + BTPROP) will collaps to two groups of softwood and hardwood basd on th formulas in tabl 5. As a rsult, th proportion of mrchantabl biomass to total abovground biomass ithr including or xcluding foliag with CRM will b th sam for all softwoods and th sam for all hardwoods. It is provd in th following sction. Th total abovground biomass xcluding foliag with currnt CRM approach is: DRYBIOT_CRM = MSBIOFIA + STPBIOFIA + TOPBIOFIA (2) whr MSBIOFIA is mrchantabl stm woody biomass (biomass of th bol) from FIA, STPBIOFIA is stump biomass, and TOPBIOFIA is branchs and top biomass. 16