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The capacitance at the feedpoint of a base-driven monopole installed with its base just above the surface of the earth depends on its length, and its diameter.
The real value of the resistance present in the system connection to r-f ground is not a factor in this.
However Part 15 AM systems using a long, radiating path to a functional r-f ground (something buried in the earth, typically) will have increased capacitance due to the longer, radiating conductor(s) added to the 3-m whip.
This change may affect the ability to set the reactance of the loading coil as needed to achieve system resonance.