Pine needles are commonly applied as a mulch around the dripline of acid-loving ornamentals such as azaleas, rhododendrons, hollies etc. Decomposition is relatively slow compared to hardwood mulches but will definitely alter soil pH over the long term. Ever watch the Masters Golf tournament? Notice the 8-10' azaleas surrounding many of the greens. All are mulched in with pine needles ( a little known fact, they also ice down the azaleas so they will be at peak bloom for the tv cameras if they have an unusually warm spring.) Yes, a soil test is mandatory for pH and other critical soil information but I would be willing to bet the farm that any area with mature, established pine trees will be on the low side of the pH scale. Find another site or amend the soil with a quick-acting product such as Solucal...not lime.