[Relationship between soil organic phosphorus forms in larch plantations and tree growth]

Using the organic phosphorus fractionation system suggested by Bowman and Cole, this paper studied the dynamics of labile, moderately labile, moderately resistant, and highly resistant organic phosphorus in rhizosphere and non-rhizosphere soil at different development stages of larch, and their relationships with soil available phosphorus and tree growth yield. The results showed that the main components of soil organic phosphorus in larch plantation were moderately labile and moderately resistant organic phosphorus, amounted to 77.07%-86.68% of the total organic phosphorus. The labile and moderately labile organic phosphorus in rhizosphere soil were the main sources of soil available phosphorus at different development stages of larch. The contents of total organic phosphorus, labile organic phosphorus, moderately resistant organic phosphorus and highly resistant organic phosphorus in rhizosphere soil decreased with stand ages from young stand to near mature stand, but increased from near mature stand to mature stand. No apparent change of the moderately labile organic phosphorus content was found over stand ages in rhizosphere soil. The contents of various organic phosphorus forms presented a fluctuating increasing tendency in non-rhizosphere soil as stand ages increased. There was a close relationship between the increments of periodic average diameter at breast height and periodic average height and the contents of soil labile organic phosphorus and available phosphorus.