﻿Pinyon-Juniper 
  Volume 
  

   Equations 
  for 
  the 
  Central 
  

   Rocky 
  Mountain 
  States 
  

  

  David 
  C. 
  Chojnacky 
  

  

  INTRODUCTION 
  

  

  Piny 
  on- 
  juniper 
  woodlands 
  have 
  a 
  rich 
  history 
  of 
  use. 
  

   Native 
  Americans 
  in 
  the 
  West 
  depended 
  on 
  the 
  trees 
  for 
  

   fuel 
  wood 
  and 
  food. 
  In 
  the 
  late 
  1800's 
  settlers 
  cut 
  an 
  un- 
  

   documented 
  amount 
  of 
  pinyon 
  (pinon) 
  and 
  juniper 
  trees 
  

   for 
  lumber, 
  mine 
  props, 
  fuel 
  wood, 
  charcoal, 
  fenceposts, 
  

   and 
  other 
  products 
  for 
  mining 
  and 
  ranching 
  enterprises. 
  

   However, 
  during 
  the 
  past 
  40 
  to 
  50 
  years, 
  the 
  vast 
  acre- 
  

   ages 
  of 
  pinyon-juniper 
  (P-J) 
  woodlands 
  were 
  virtually 
  

   ignored 
  as 
  a 
  source 
  of 
  wood. 
  In 
  many 
  areas, 
  P-J 
  removal 
  

   by 
  chaining 
  was 
  the 
  accepted 
  management 
  practice 
  for 
  

   improving 
  the 
  land's 
  grazing 
  potential. 
  

  

  Today, 
  P-J 
  woodlands 
  again 
  are 
  being 
  eyed 
  as 
  a 
  val- 
  

   uable 
  resource 
  for 
  fuel 
  wood 
  and 
  other 
  uses. 
  Increased 
  

   energy 
  demands 
  and 
  new 
  requirements 
  for 
  sound 
  ecologi- 
  

   cal 
  land 
  management 
  are 
  creating 
  new 
  pressures 
  and 
  

   opportunities 
  on 
  approximately 
  48 
  million 
  acres 
  of 
  P-J 
  

   woodlands 
  in 
  the 
  Western 
  United 
  States. 
  

  

  This 
  concern 
  prompted 
  a 
  joint 
  effort 
  by 
  the 
  U.S. 
  

   Department 
  of 
  Agriculture's 
  Forest 
  Service 
  (Forest 
  Sur- 
  

   vey), 
  the 
  Department 
  of 
  the 
  Interior's 
  Bureau 
  of 
  Land 
  

   Management 
  and 
  Bureau 
  of 
  Indian 
  Affairs, 
  and 
  several 
  

   State 
  forestry 
  departments 
  to 
  inventory 
  P-J 
  woodlands 
  

   in 
  Nevada, 
  Idaho, 
  Utah, 
  Colorado, 
  South 
  Dakota, 
  and 
  

   Wyoming. 
  Data 
  provided 
  by 
  this 
  joint 
  inventory 
  were 
  

   the 
  basis 
  for 
  the 
  study 
  described 
  in 
  this 
  paper. 
  This 
  

   study's 
  purpose 
  was 
  to 
  develop 
  individual 
  tree 
  cubic 
  foot 
  

   volume 
  equations 
  for 
  pinyon, 
  juniper, 
  and 
  other 
  wood- 
  

   land 
  tree 
  species 
  sampled 
  by 
  these 
  inventories. 
  

  

  REVIEW 
  OF 
  PAST 
  WORK 
  

  

  Constructing 
  volume 
  equations 
  for 
  pinyon 
  and 
  juniper 
  

   trees 
  presents 
  unique 
  problems. 
  Unlike 
  most 
  conifers, 
  

   excessive 
  branching 
  and 
  multiple 
  basal 
  stems 
  appear 
  to 
  

   be 
  normal 
  growth 
  patterns 
  for 
  P-J. 
  Researchers 
  have 
  

   tried 
  a 
  variety 
  of 
  measurements 
  to 
  describe 
  P-J 
  trees' 
  

   bushy 
  character, 
  usually 
  including 
  crown 
  and 
  stem 
  vari- 
  

   ables 
  in 
  their 
  volume 
  equations 
  in 
  addition 
  to 
  conven- 
  

   tional 
  variables 
  of 
  diameter 
  and 
  height. 
  

  

  Howell 
  (1940) 
  and 
  Reveal 
  (1944) 
  conducted 
  some 
  of 
  the 
  

   first 
  P-J 
  volume 
  studies 
  in 
  Arizona, 
  New 
  Mexico, 
  and 
  

   Nevada 
  (summarized 
  by 
  Barger 
  and 
  FfoUiott 
  in 
  1972). 
  

   This 
  work 
  became 
  P-J 
  volume 
  inventory 
  standards 
  used 
  

   in 
  Soil 
  Conservation 
  Service 
  handbooks. 
  These 
  volume 
  

   tables 
  required 
  measurement 
  of 
  diameter 
  at 
  breast 
  

   height 
  (d.b.h.), 
  crown 
  diameter, 
  diameter 
  of 
  the 
  tallest 
  

   stem 
  at 
  1 
  foot, 
  and 
  the 
  amount 
  of 
  4-foot 
  wood 
  segments 
  

   at 
  least 
  2 
  inches 
  in 
  diameter. 
  

  

  Mason 
  and 
  Hutchings 
  (1967) 
  offered 
  tree 
  foliage 
  yield 
  

   models 
  based 
  on 
  crown 
  dimensions 
  for 
  juniper 
  in 
  Utah. 
  

   Storey 
  (1969) 
  constructed 
  equations 
  for 
  predicting 
  P-J 
  

   biomass 
  in 
  southern 
  California 
  from 
  measurements 
  of 
  

   crown 
  dimensions, 
  total 
  height, 
  and 
  basal 
  diameter 
  at 
  

   1 
  foot 
  above 
  ground 
  line. 
  Estola 
  (1979) 
  developed 
  P-J 
  

   volume 
  equations 
  for 
  southern 
  Colorado 
  and 
  northern 
  

   New 
  Mexico 
  using 
  diameter 
  at 
  1 
  foot 
  above 
  ground 
  line, 
  

   crown 
  diameter, 
  and 
  total 
  height 
  as 
  predictor 
  variables. 
  

   Also, 
  in 
  northern 
  New 
  Mexico, 
  Clendenen 
  (1979) 
  devel- 
  

   oped 
  P-J 
  volume 
  equations 
  using 
  diameter 
  at 
  the 
  root 
  

   collEir 
  (DRC), 
  total 
  height, 
  and 
  number 
  of 
  stems 
  3 
  inches 
  

   in 
  diameter 
  within 
  1 
  foot 
  above 
  ground 
  line. 
  Gholz 
  (1980) 
  

   reported 
  volume 
  and 
  biomass 
  equations 
  for 
  juniper 
  in 
  

   western 
  Oregon 
  using 
  only 
  basal 
  circumference 
  of 
  the 
  

   stem 
  as 
  a 
  predictor 
  variable. 
  

  

  Tausch 
  (1980) 
  studied 
  allometric 
  relationships 
  between 
  

   plant 
  parts 
  for 
  P-J 
  in 
  southwestern 
  Utah. 
  He 
  did 
  not 
  

   provide 
  volume 
  equations 
  but 
  gave 
  biological 
  reasons 
  for 
  

   expecting 
  P-J 
  volume 
  to 
  be 
  proportional 
  to 
  a 
  function 
  of 
  

   DRC. 
  He 
  suggested 
  the 
  proportionality 
  constant 
  

   between 
  volume 
  and 
  DRC 
  would 
  change 
  with 
  site 
  qual- 
  

   ity. 
  Miller 
  and 
  others 
  (1981) 
  and 
  Meeuwig 
  and 
  Budy 
  

   (1981) 
  presented 
  two 
  ways 
  for 
  estimating 
  P-J 
  biomass 
  

   for 
  the 
  same 
  areas 
  in 
  Nevada. 
  Their 
  equations 
  required 
  

   measurement 
  of 
  crown 
  diameter, 
  d.b.h., 
  number 
  of 
  stems 
  

   greater 
  than 
  3 
  inches, 
  and 
  diameter 
  at 
  1 
  foot 
  above 
  

   ground 
  line. 
  

  

  Weaver 
  and 
  Lund 
  (1982) 
  examined 
  diameter-weight 
  

   relationships 
  for 
  juniper 
  in 
  eastern 
  Montana. 
  Their 
  

   results 
  undermined 
  Tausch 
  's 
  site-quality 
  hypothesis 
  by 
  

   finding 
  the 
  same 
  proportionality 
  constant 
  between 
  tree 
  

   weight 
  and 
  DRC 
  on 
  three 
  different 
  sites. 
  Chittester 
  and 
  

   MacLean 
  (1984) 
  built 
  an 
  equation 
  for 
  estimating 
  volume 
  

   from 
  d.b.h. 
  and 
  height 
  for 
  juniper 
  in 
  Oregon 
  and 
  

   California. 
  

  

  Ambrosia 
  and 
  others 
  (1983) 
  used 
  pinyon 
  and 
  juniper 
  

   volume 
  equations 
  in 
  a 
  Nevada 
  Landsat 
  study. 
  Although 
  

   they 
  gave 
  no 
  reference 
  source, 
  these 
  equations 
  were 
  iden- 
  

   tical 
  to 
  preUminary 
  equations 
  developed 
  by 
  Chojnacky 
  

   (1981) 
  for 
  interim 
  use 
  in 
  Nevada 
  prior 
  to 
  this 
  publica- 
  

   tion. 
  These 
  equations 
  required 
  DRC 
  and 
  total 
  height 
  

   measurements 
  and 
  were 
  based 
  on 
  data 
  described 
  by 
  

   Born 
  and 
  Chojnacky 
  (in 
  preparation). 
  

  

  Past 
  work 
  can 
  be 
  summarized 
  by 
  observing 
  that 
  

   everyone 
  has 
  measured 
  pinyon 
  and 
  juniper 
  differently. 
  

   Only 
  Tausch 
  and 
  Weaver 
  gave 
  biological 
  reasoning 
  for 
  

   their 
  work. 
  The 
  rest 
  cited 
  statistics 
  associated 
  with 
  

   regression 
  modeling 
  as 
  justification 
  for 
  their 
  particular 
  

  

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