The effects of understory vegetation on P availability in Pinus radiata forest stands: A review

In many second-rotation Pinus radiata forest plantations, there has been a steady trend towards wider tree spacing and an increased rate of application of P fertiliser. Under these regimes, the potential for understory growth is expected to increase through increased light and greater nutrient resources. Therefore, understory vegetation could become a more significant component of P cycling in P. radiata forests than under closely-spaced stands. Studies have shown that growth rates and survival of trees is reduced in the presence of understory vegetation due to the competition of understory vegetation with trees. Other studies have suggested that understory vegetation might have beneficial effects on nutrient cycling and conservation within forest stands. This review discusses the significance of understory vegetation in radiata pine forest stands, especially their role in enhancing or reducing P availability to forest trees.