Publication Date:
2013-01-22
Description:
Measurement of tree root systems by conventional methods is a Herculean task. The electrical capacitance method offers a rapid and non-destructive alternative, but it has largely been restricted to herbaceous species. The Dalton Model has been the main concept for understanding equivalent root circuitry; it proposed that roots were cylindrical capacitors with epidermis and xylem being the external and internal electrodes. Capacitance ( C ) therefore varied in proportion to root surface area ( A ), mass ( M ), length ( L ) and relative permittivity of the plant tissue r . We used the capacitance method on forest and plantation trees (13 to circa 100 y.o.) in situ to test hypotheses derived from implicit assumptions about tree-root–soil circuitry. We concluded: C was not confounded by intermingled root systems; C was strongly related to diameter at breast height (DBH); C was less strongly related to DBH for multiple species at the same site; and C was a poor indicator of DBH, M and L across species, ages and sites. We proposed that r was proportional to root tissue density and fitted a model with P 〈 0.05 and R 2 = 0.70 when the three immature (13 y.o.) trees were excluded. There was no significant difference ( P = 0.28) between the parameters of the tree model (excluding the immature trees) and one of the same form fitted to data from bean ( Vicia faba L.; R 2 = 0.55). Together, the data sets suggested ( R 2 = 0.94; n = 26) that there may exist a general relationship of this form applied over two orders of magnitude of L .
Print ISSN:
0829-318X
Electronic ISSN:
1758-4469
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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