Ezylman is correct. Pines do acidify soils more so than most other types of trees. However, all decaying tree leaves acidify the soil to a degree. They could have an impact on pond ph if large amounts of leaves/needles go into the pond. However, this will likely be pretty negligible depending on the amount of flow through your pond has, the ph of water entering your pond, etc. Typically, it's a non-issue for most. There are others here who could describe this much better than I.
Pines make a good windbreak, in part, because they tend to have a dense foliage from top to bottom as well as the fact that they choke off many competing trees, shrubs and weeds due to the fallen needles (an acidic mulch). Additionally, the lack of light penetration beneath them prevents other competing plants from getting much of a foot hold. This is also the reason it is VERY difficult to grow any kind of quality turf beneath them. The floor of a natural pine forest is basically just fallen needles and not much more. They often tend to be very homogeneous stands.
