Monolith Method of Root-Sampling in Studies on Succession and Degeneration

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Abstract
Blocks of soil 2.5 ft. wide, 3 inches thick, and 3-6 ft. in depth were taken from the vertical walls of trenches by the new, monolith method of root study. The roots of Andropogon furcatus were very heavy in climax prairie on Wabash silt loam (91.1 g. per sample). They were uniformly distributed, decreased gradually in wt. with depth, and extended downward 6 ft. When Poa pratensis replaced A. furcatus after several yrs. of overgrazing, its root system was relatively light (55.6 g.), entirely confined to the surface 3 ft., and had 89.9% of its wt. in the surface foot of soil. Root distribution in bunch-grass prairie was remarkably uniform below a depth of 3 inches and not unlike that under sod-forming spp. Root wt. was only slightly concentrated beneath the bunches. This method revealed the presence of widely spreading roots of Panicum virgatum and A. furcatus 12-24 inches laterally below adjacent stands of Poa pratensis. Adaptation of roots of Agropyron smithii to soils with claypans illustrates 3 distinct environments underground. A granular A horizon of mellow, moist soil resulted in a well-branched, heavy, normal development of roots. In the claypan beneath, roots were fewer and branching was poor. In the mellow, moist soil below the claypan, root branching greatly increased and total wt. of roots was 1/3 greater.

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