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Table 1 from:


Jackson, R. D., and Paine, L. K. 2006. Revisiting Robel’s visual obstruction method for estimation of standing crop in grasslands. Online. Forage and Grazinglands doi:10.1094/FG-2006-1213-01-RS.



Table 1A. Summary of studies comparing Robel pole readings to harvested biomass estimates.

Author(s) Publication Year Location Vegetation type Best r2 value Size of clipped area, quadrat (m2) Dimensions of quadrat (cm)
Robel et al. 1970 Kansas Native range       0.97          0.1 20 x 50
Ackerman et al. 1999 Oklahoma Seeded Old World bluestem       0.6          0.1 20 x 50
Benkobi et al. 2000 Nebraska Native range       0.88          0.25 Circular
Ganguli et al. 2000 Texas Native range       0.87          0.1 Not given
Harmoney et al. 1997 Iowa Seeded warm & cool season grasses       0.63          0.21 Not given
Vermeire & Gillen 2001 Oklahoma Native range       0.95          0.1 20 x 50
Vermeire et al. 2000 Texas Native range       0.93          0.1 20 x 50
Volesky et al. 1999 Nebraska Native range       0.41          0.25 25 x 100


Table 1B. Summary of studies comparing Robel pole readings to harvested biomass estimates.

Author(s) Proximity of quadrat & Robel pole Robel readings / sample site Calculation
 of means		 Alternative
calculation of means		 Observ. /experi-mental unit Total # of transects Total observ.
Robel et al. Quadrat directly in front of pole 1 Pooled across transect       10 30 300
Ackerman et al. Quadrat directly in front of pole 1 Pooled across transect        5 12 60
Benkobi et al. Pole in center of quadrat 1 Pooled across transect       20 174 3480
Ganguli et al. Quadrat directly in front of pole 1 Pooled across transect Regressed against individual plot values 20 25 500
Harmoney et al. Pole in center of quadrat 4 Regressed against individual plot Regressed against individual plot means 26.5 8 212
Vermeire & Gillen Quadrat directly in front of pole 1 Pooled across transect      20 48 960
Vermeire et al. Quadrat directly in front of pole 1 Pooled across transect       20 44 880
Volesky et al. Pole in center of quadrat 2 or 4 Regressed against individual
plot (2 observ.)		 Regressed against individual plot means (4 observ.) 4 63 252

Abbreviations: calc. = calculations; observ. = observations.




© 2006 Plant Management Network.