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Total Net Productivity and Turnover on an Energy Basis For Tallgrass Prairie
Author(s) -
Kucera C. L.,
Dahlman Roger C.,
Koelling Melvin R.
Publication year - 1967
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1936496
Subject(s) - standing crop , productivity , biomass (ecology) , environmental science , growing season , agronomy , litter , primary production , dry matter , dry weight , zoology , ecosystem , ecology , biology , economics , macroeconomics
The energy equivalent of total net productivity including foliage and roots on unburned prairie in 1962 was 4.351 X 10 6 cal/m 2 , representing 992 g of biomass. The root system provided slightly over 50% of the annual increment. For 1963 the total growth was 1,133 g/m 2 . The average energy for these years was equivalent to 1.21% of the incident radiation received during the growing season for the 400—700 μm portion of the light spectrum. The maximum energy budget including current increment, roots of previous years, and litter was equal to 2.6 turnovers. In years with favorable rainfall, fire approximately doubled the aboveground yield. During drought, productivity increases of fire plots over control plots were curtailed sharply. On a dry matter basis, the total aboveground biomass at the end of the growing season was approximately twice that of the standing crop. During the April—September period for 3 years of observation, the loss in dry weight of the aboveground material ranged from 57% to 65%. For the remiander of the year the decrease was 31—39%. These values indicate a fluctuating but generally balanced annual system of growth and decay. For aboveground biomass, the turnover estimate was 2 years, and for root biomass, 4 years. The decay time of a standing crop or root increment as determined from isolated litter samples and carbon—14—labeled roots in the field indicated that the annual turnover was comprised of a series of increments of different ages, decreasing in caloric content with time on a dry weight basis (uncorrected for ash). On an ash—free basis, litter 4 years old showed some increase in caloric content, suggesting changing composition of the residual fraction. The tallgrass prairie is seen as a relatively efficient ecosystem when compared to the worldwide terrestrial average. The stimulus of fire to dry matter production in the humid prairie indicates a more efficient use of solar energy; however, the long—term effects of sustained burning require observation.