Shawn Bowers 2008 tree plot soil nitrogen treatment Shawn Bowers public read er-2008-ex3-data.txt 2008 ER Example 3 Data er-2008-ex3-data.txt 1 column , trns trns Transect id Number assigned to transects. trmt trmt Water treatment depth. hi Hi water level lo Lo water level soil soil Soil type. s Spodosol h Histosol pH pH Soil acidity dimensionless real tree tree Tree id Number assigned to trees. spp spp Species name. piru Picea rubens abba Abies balsamea dbh dbh Tree diameter at breast height centimeter real