Answer
a) Please see the image.
b) It has little effect for young forests since the atmospheric contribution is large compared with moss input until about 120 years of age. After that, the contribution is very large, tripling or quadrupling the atmospheric input after several centuries.
Work Step by Step
For the graph, simply plot as directed and estimate a best fit dashed line through the points. For b), simply compare the atmospheric input of 1.0 kg/ha/yr with the data in the table and describe the relative magnitude of inputs from atmosphere and moss.