A student group is involved in a restoration study of a nearby disturbed area. They decide to collect six soil samples and analyze them for carbon (C) and nitrogen (N). Two of the samples are found to be very high in C and N, but the other four samples are low in both. The students also notice that the color of the two soil samples that are high in C and N is very dark. Requried:
What is the most likely explanation of the data?