﻿PLANTS 
  OF 
  CHINA 
  — 
  WALKER 
  349 
  

  

  TIBET 
  

  

  Besides 
  the 
  floristic 
  provinces 
  already 
  discussed 
  as 
  extending 
  into 
  

   Tibet, 
  namely, 
  the 
  arid 
  valleys 
  of 
  the 
  great 
  rivers 
  draining 
  south- 
  

   eastern 
  Tibet, 
  the 
  high 
  mountain 
  vegetation 
  of 
  the 
  Tibet-China 
  bor- 
  

   derland, 
  and 
  the 
  grasslands, 
  Tibet 
  has 
  two 
  other 
  areas. 
  These 
  are 
  

  

  (1) 
  the 
  northern 
  and 
  northeastern 
  parts, 
  called 
  by 
  F. 
  Kingdon 
  Ward 
  2 
  

   the 
  Chang 
  Tang 
  or 
  Great 
  Plain, 
  including 
  the 
  Tsaidam 
  in 
  Tsinghai 
  

   Province, 
  the 
  whole 
  draining 
  entirely 
  into 
  salt 
  lakes 
  and 
  swamps, 
  and 
  

  

  (2) 
  the 
  outer 
  plateau 
  part 
  north 
  of 
  the 
  Himalaya 
  Mountains 
  drained 
  

   by 
  five 
  great 
  rivers, 
  the 
  Indus, 
  Tsang 
  Po, 
  Salween, 
  Mekong, 
  and 
  

   Yangtze. 
  The 
  divide 
  between 
  these 
  areas 
  is 
  generally 
  low 
  and 
  rather 
  

   imperceptible. 
  

  

  The 
  Great 
  Plain 
  and 
  Tsaidam 
  on 
  the 
  north 
  at 
  an 
  altitude 
  of 
  over 
  

   8,000 
  feet 
  have 
  a 
  rainfall 
  ranging 
  from 
  almost 
  nothing 
  at 
  all 
  to 
  only 
  

   10 
  inches 
  per 
  year. 
  The 
  flora, 
  according 
  to 
  "Ward, 
  is 
  extremely 
  

   meager 
  and 
  consists 
  of 
  about 
  53 
  species 
  of 
  plants, 
  with 
  only 
  3 
  woody 
  

   genera 
  and 
  no 
  endemics, 
  nearly 
  all 
  being 
  central 
  Asiatics. 
  A 
  richer 
  

   vegetation 
  could 
  not 
  exist 
  in 
  such 
  an 
  extremely 
  dry 
  and 
  severe 
  climate. 
  

  

  The 
  outer 
  plateau 
  toward 
  the 
  south 
  has 
  a 
  better 
  climate, 
  with 
  rain- 
  

   fall 
  ranging 
  from 
  10 
  to 
  20 
  inches 
  per 
  year. 
  Its 
  altitude 
  of 
  around 
  

   12,000 
  feet, 
  with 
  its 
  exposure 
  to 
  the 
  cold 
  winds 
  of 
  the 
  north, 
  permits 
  

   only 
  a 
  limited 
  and 
  rather 
  xerophytic 
  flora 
  to 
  develop. 
  However, 
  there 
  

   is 
  sufficient 
  moisture 
  and 
  protection, 
  at 
  least 
  in 
  the 
  river 
  valleys, 
  for 
  

   the 
  development 
  of 
  an 
  alpine 
  and 
  semidesert 
  flora, 
  the 
  dominant 
  woody 
  

   plants 
  being 
  willows, 
  poplars, 
  junipers, 
  and 
  certain 
  elms. 
  At 
  the 
  

   head 
  of 
  the 
  gorge 
  country 
  toward 
  the 
  east 
  are 
  found 
  some 
  forests. 
  In 
  

   the 
  gravel 
  portion 
  of 
  this 
  plateau, 
  in 
  the 
  vicinity 
  of 
  Lhassa, 
  Ward 
  

   reports 
  that 
  541 
  species 
  of 
  plants 
  are 
  known. 
  It 
  is 
  in 
  this 
  part 
  of 
  

   Tibet 
  that 
  the 
  bulk 
  of 
  the 
  population 
  is 
  found. 
  

  

  THE 
  ECONOMIC 
  BOTANY 
  OF 
  CHINA 
  

   CONCERNING 
  DEFORESTATION 
  

  

  The 
  most 
  outstanding 
  economic 
  problem 
  of 
  China 
  is 
  raising 
  food 
  

   for 
  her 
  more 
  than 
  400 
  million 
  people. 
  So 
  intense 
  has 
  become 
  the 
  

   struggle 
  for 
  food 
  in 
  China 
  that 
  little 
  energy 
  has 
  been 
  left 
  for 
  the 
  

   consideration 
  of 
  other 
  problems. 
  The 
  need 
  for 
  more 
  and 
  more 
  food 
  

   has 
  been 
  met 
  by 
  increasing 
  the 
  amount 
  of 
  food 
  grown 
  on 
  an 
  acre 
  of 
  

   land 
  and 
  by 
  increasing 
  the 
  acreage. 
  This 
  has 
  been 
  accompanied 
  by 
  a 
  

   steady 
  increase 
  in 
  the 
  human 
  labor 
  expended 
  and 
  in 
  the 
  taking 
  of 
  

   land 
  away 
  from 
  other 
  uses, 
  notably 
  the 
  taking 
  of 
  forested 
  land. 
  In 
  

   the 
  wake 
  of 
  these 
  changes 
  have 
  come 
  numerous 
  other 
  problems 
  which 
  

  

  * 
  See 
  his 
  A 
  sketch 
  of 
  the 
  geography 
  and 
  botany 
  of 
  Tibet 
  • 
  • 
  *, 
  Joum. 
  Linnean 
  Soc, 
  

   Botany, 
  vol. 
  50, 
  pp. 
  239-265, 
  illustr., 
  1935. 
  

  

  