Appendix 2 Vegetation and grazing Surveys of

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were sampled where grazing had ceased in 2000 (grazed). Data on plant species were taken in Spring 2005. Further results and methods used are described in ...
Appendix  2   Vegetation  and  grazing   Surveys  of  species  richness  of  flowering  and  non-­‐flowering  plants  and  cover  were   made  during  2005  in  all  the  same  habitats  sampled  for  bees  in  2001  (riparian,  mesquite,   grassland  and  scrub)  except  the  field  (Minckley  2012).  For  background,  the  results  of   that  study  are  summarized  here  (see  Table  below).  The  2005  study  found  habitats  varied   2-­‐fold  in  plant  species  richness  with  fewer  species  in  the  mesquite  and  riparian  habitats   than  in  the  grassland  and  scrub  habitats.  The  effect  of  grazing  on  the  plant  community   was  evident  despite  the  considerable  time  since  grazing  had  stopped  (4  and  26  years  in   Mexico  and  in  the  United  States,  respectively).  The  riparian  and  mesquite  habitats  had   significantly  more  plant  species  in  the  grazed  area  than  they  did  in  the  ungrazed  areas,   in  contrast  to  grassland  and  scrub  habitats  where  plant  species  richness  did  not  change   (Table  S1).  Plant  diversity  was  lowest  in  the  ungrazed  riparian  habitat  where  shading   from  the  dense  cottonwood  (Populus  fremontii)  canopy  deterred  establishment  of   subshrubs  and  herbaceous  vegetation.  Grazing  resulted  in  higher  plant  species  richness   in  riparian  habitats  because  the  diminished  tree  recruitment  allowed  for  greater  light   penetration  and  enabled  short-­‐statured  plant  species  to  establish.  Although  the  same   number  of  species  were  in  grazed  and  ungrazed  areas  of  the  grassland  and  scrub   habitats,  it  is  not  clear  if  this  indicates  the  areas  were  not  grazed  intensively  enough  to   have  an  impact  to  if  successional  changes  in  these  water-­‐limited  plant  communities   were  slower  than  what  could  be  detected  in  the  22  year  differences  of  the  grazed  and   ungrazed  areas  (Minckley  2012).         Table  S1.  Average  number  (+  standard  deviation)  of  plant  species  in  plots  from  four   habitats  in  the  San  Bernardino  Valley,  Arizona,  USA  and  Sonora,  Mexico.  In  each  habitat,   four  plots  were  sampled  where  grazing  had  ceased  in  1979  (ungrazed)  and  four  plots   were  sampled  where  grazing  had  ceased  in  2000  (grazed).  Data  on  plant  species  were   taken  in  Spring  2005.  Further  results  and  methods  used  are  described  in  Minckley  (2012).       HABITAT   GRAZING   NUMBER       HISTORY   of  SPECIES   _________________________________     Mesquite   Ungrazed   9.75  +  2.17     Mesquite   Grazed   14.25  +  2.06     Grass   Ungrazed   20.25  +  5.68     Grass   Grazed   24.25  +  2.63   Riparian   Ungrazed   12.25  +  2.75     Riparian   Grazed   25.0  +  4.69     Scrub   Ungrazed   18.63  +  5.32     Scrub   Grazed   20.13  +  6.83      

Minckley,  R.L.  (2012)  Trajectory  and  rate  of  desert  vegetation  response  following  cattle   removal.  Gottfried,  G.  J.,  Ffolliott,  P.  F.,  Gebow,  B.S.,  &  Eskew,  L.G.,  compilers.   2012.  Merging  science  and  management  in  a  rapidly  changing  world:   biodiversity  and  management  of  the  Madrean  Archipelago  III.  2012  May  1-­‐5,   Tucson,  AZ.  Proceedings  RMRS-­‐P-­‐67.  Fort  Collins,  CO:  U.S.  Department  of   Agriculture,  Forest  Service,  Rocky  Mountain  Research  Station.