Comparison of Four Methods of Grassland Productivity Assessment Based on Festuca pallescens Phytomass Data

DEFOSSE, GUILLERMO E.; BERTILLER, M. B.

JOURNAL OF RANGE MANAGEMENT

American Society for Range Management

Año: 1991 vol. 44 p. 199 - 203

0022-409X

The relative utility of 4 methods for grasslands above-ground net primary productivity (ANPP) assessment were evaluated. These methods, applied to a set of phytomass and litter data collected at about bimonthly intervals for 2 years in a Festuca pallescens (St. Yves) Parodi grassland steppe of southwestern Chubut, Argentina, were: (1) summation of positive increments of green (live) biomass between harvests, (2) summation of positive increments of total phytomass between haNeStS, (3) summation Of pOSitiVC increments of green biomass between harvests plus correction factors which accounted for the concomitant increases in dry, old dead, and litter, respectively, and (4) mdhemrtical model of simultaneous differential equations which fitted the values of phytomass data obtained in the field. Method 1 gave consistently (p10.05) the lowest ANPP values in both years. Productivity values obtained with methods 2,3, and 4 were highly correlated and did not differ significantly (~60.05) with each other. Their estimates varied from 94.8 to 105.3 g of dry matter per mz for the first year and from 73.0 to 149.4 g of dry matter per m* for the second year. These values are within the range of productivity given for other climatologically and physiognomically similar semiarid grasslands of North Amer-ica. Each method except 1 provided reliable estimations of ANPP for the grassland studied. Methods 2,3, and 4 can also be used to assess ANPP in any other grassland with similar characteristics. Each one, however, might have particular applications according to the specific objectives pursued.