Root dynamics of a shortgrass ecosystem
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Date
1971
Authors
Bartos, Dale L., author
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Abstract
Seasonal dynamics of roots of a shortgrass system were determined by samples collected at two week intervals for two growing seasons (1969-1970) with a fall and winter sampling period in between. Soil cores were taken to a depth of either 10 cm or 80 cm; the deep cores were used to determine the entire profile distributions of roots. The cores were washed free of soil particles and then the root mass was dried, weighed, ashed and reweighed. All values were expressed on an ash-free basis. Sixty percent of the root weight was in the 0-10 cm segment and 75% was found in the upper 20 cm of the soil profile. The upper 10 cm increment had significant variations between dates, but the lower levels remained quite constant. Four grazing treatments (none, light, moderate, heavy) were used to determine if grazing had an effect on the root mass. No significant differences were found among the four treatments. The usual concept of substrate storage in roots and subsequent utilization was not supported by the data. Losses of root weights did not coincide with periods of leaf initiation. An alternative model was developed which better represented the fluctuations found during the 1969 growing period. This model reflects a hypothesis of root decomposition and growth which is a new approach to understanding root dynamics. The mathematical model consists of two logistic equations added together. The resultant equation was fitted to the original data via a direct search curve fitting program. Two curves were separated from the main equation with the declining curve representing decomposition and the rising curve growth. Various constants were added to the equation to limit the indicated amount of decomposition. The various curves presented all have merit, however, more work needs to be done to determine what actually occurs in nature.
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Subject
Roots (Botany)
Grasses
Ecology