﻿30 
  Gleason: 
  Some 
  applications 
  of 
  the 
  quadrat 
  method 
  

  

  discrepancy 
  between 
  actual 
  and 
  theoretical 
  number 
  should 
  be, 
  

   and 
  is, 
  greatest 
  in 
  species 
  of 
  high 
  frequency, 
  FI 
  95 
  or 
  more. 
  

   It 
  IS 
  not 
  possible 
  to 
  draw 
  any 
  accurate 
  conclusions 
  as 
  to 
  the 
  relation 
  

   between 
  theoretical 
  and 
  actual 
  number 
  of 
  individuals, 
  but 
  in 
  

   general, 
  the 
  theoretical 
  number 
  is 
  one 
  fifth 
  to 
  two 
  thirds 
  as 
  large 
  

   as 
  the 
  actual, 
  and 
  results 
  any 
  more 
  accurate 
  than 
  this 
  are 
  prob- 
  

   ably 
  of 
  httle 
  or 
  no 
  value 
  In 
  ecological 
  description. 
  

  

  The 
  determination 
  of 
  the 
  proper 
  size 
  of 
  the 
  major 
  quadrat 
  

   involves 
  reducing 
  the 
  original 
  series 
  of 
  quadrats 
  to 
  a 
  smaller 
  num- 
  

   ber 
  of 
  larger 
  quadrats, 
  thereby 
  increasing 
  the 
  frequency 
  index 
  of 
  

  

  selected 
  species 
  to 
  99 
  or 
  more. 
  With 
  FI 
  99 
  or 
  more 
  for 
  all 
  the 
  

   important 
  species, 
  it 
  may 
  be 
  assumed 
  that 
  this 
  quadrat 
  is 
  large 
  

   enough 
  to 
  serve 
  as 
  a 
  fair 
  sample 
  of 
  the 
  association. 
  

  

  ( 
  I 
  j 
  = 
  FI, 
  substitute 
  for 
  g 
  

  

  the 
  number 
  of 
  quadrats 
  actually 
  counted, 
  use 
  for 
  FI 
  the 
  index 
  of 
  

   the 
  least 
  common 
  one 
  of 
  the 
  important 
  species, 
  and 
  solve 
  for 
  n. 
  

   Substitute 
  again 
  the 
  determined 
  value 
  for 
  n 
  and 
  99 
  for 
  the 
  original 
  

  

  FI 
  and 
  solve 
  for 
  g. 
  The 
  equation 
  is 
  i 
  - 
  - 
  = 
  '^.^ 
  (presuming 
  

  

  100 
  quadrats 
  were 
  counted), 
  from 
  which 
  q 
  may 
  be 
  easily 
  determined. 
  

  

  For 
  example, 
  in 
  a 
  certain 
  association, 
  it 
  Is 
  desired 
  to 
  determine 
  a 
  

  

  major 
  quadrat 
  which 
  will 
  probably 
  contain 
  all 
  the 
  species 
  with 
  

   rl 
  60 
  or 
  more. 
  

  

  100/ 
  

  

  ^ 
  -^ 
  I 
  I 
  - 
  T- 
  - 
  60: 
  

  

  w 
  = 
  90 
  

  

  I 
  80i^ 
  

  

  I 
  - 
  - 
  = 
  V.oi 
  : 
  2 
  = 
  20 
  (fractions 
  omitted) 
  

  

  That 
  Is. 
  the 
  original 
  100 
  quadrats 
  redivided 
  into 
  20 
  larger 
  

   quadrats 
  should 
  show 
  Fl 
  99 
  or 
  100 
  for 
  all 
  species 
  which 
  originally 
  

   had 
  FI 
  60 
  or 
  more; 
  or 
  the 
  major 
  quadrat 
  should 
  be 
  five 
  times 
  as 
  

   large 
  as 
  the 
  original. 
  The 
  error 
  concerned 
  in 
  computing 
  the 
  value 
  

   of 
  n 
  due 
  to 
  imperfect 
  distribution 
  of 
  the 
  species, 
  does 
  not 
  affect 
  

   th.s 
  last 
  equation, 
  and 
  experience 
  has 
  shown 
  that 
  it 
  gives 
  surprls- 
  

   ingly 
  good 
  results. 
  On 
  the 
  average, 
  four 
  major 
  quadrats 
  out 
  of 
  

   five, 
  the 
  ocation 
  of 
  which 
  is 
  chosen 
  at 
  random, 
  present 
  all 
  the 
  

  

  species 
  

  

  