Question
It is my understanding that the fallen needles (leaves) of a pine tree are in the pH range of 6.2 and the leaves from Oaks in the range of 4.3.  how is it that the soil under pines is more acidic than under Oaks?  Is it a chemical reaction of the breakdown of the needles that causes the pH to be lower while the Oak leaves do not decompose as readily and become widely dispersed with little affect on the soil immediately under the Oaks?  Where am I going wrong here?

Answer
Hi Michael, It's not as simple as it sounds.  The pH of the foliage is dependant on the pH of the soil and the type of plant.  Generally though, the more acidic the soil, the more acidic the foliage. Oaks have adapted to excel in different soils than pines but both will survive in less than optimum pH and soil type.  The truth is, decomposed pine needles or leaves have virtually no effect on the soil's pH.  Jim