tdgeek:

 

     As pine trees mature, they shed needles that lie like an acidic carpet around their trunks. A myth exists that this gradually causes the soil to become acidic, killing nearby plants. In fact, however, pine tree needles barely affect the soil pH even when worked into the soil for that purpose.

 

Young pines in NZ are good at out competing others, but as they age the rest of the forest floor will repopulate... Its mainly the lack of light that slows things down, but eventually (50+ years) natives will recolonise a pine plantation....