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The Influence of Chronic Gamma Irradiation on Production and Decay of Litter and Humus in an Oak‐Pine Forest
Author(s) -
Woodwell G. M.,
Marples T. G.
Publication year - 1968
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1934112
Subject(s) - litter , humus , standing crop , plant litter , organic matter , environmental science , zoology , biology , agronomy , soil water , ecology , nutrient , biomass (ecology)
The irradiated forest at Brookhaven National Laboratory was used to examine the flux of organic matter through the organic horizon of soil. Production of litter along the gradient of intensity of radiation proved an excellent criterion of radiosensitivity. The standing crop of organic matter in soil was about 6,300 g (dry weight)/m 2 . Of this about 4,700 g was humus and 1,600 g litter. Annual input of litter averaged 342 g; of roots, about 311 g. The rate of decay of all organic matter in the surface soil was 10—12%/year. The litter layer decayed more rapidly at about 16%/year, the humus more slowly at about 8.4%/year. Decay of litter of white oak in the first year on the ground was 58%, that of scarlet oak, 67%. Irradiation at 600—700 R/day consistently increased the rate of decay of litter. Studies of the radiosensitivity of the principal species of trees and shrubs showed: (1) a lag of 1 year in the initial effects of irradiation behind the exposure causing them; (2) a regular increase after the first year in total cumulative exposure causing 50% reduction in the production of foliage; and (3) shifts in the relative sensitivities of species with time: the scarlet oak, initially more sensitive than the white oak, recovered in 3 years to be more resistant than white oak, and the sensitivities of white oak and pitch pine appear to converge at about 30 years.