『Abstract
The biogeochemical stability of soil P is often assumed to be
related to its solubility but there are few tests of this assumption.
We determined differences in forms of soil P among stages of stand
development in a replicated (N = 3) age sequence of Nothofagus
stands developed after catastrophic disturbance by windthrow in
New Zealand. Seedling, sapling, pole, and mature stages used were
approximately 10, 25, 120 and >150 years old, respectively. We
hypothesized that insoluble soil P forms would not differ among
stages of stand development.
Organic forms of soil P depended significantly on stage of stand
development. Concentrations of labile (NaHCO3
extractable) and non-labile (NaOH extractable) organic P were
significantly greater in the mature stage than in sapling and
pole stages. The concentration of occluded organic P (NaOH extractable
following extraction with acid) was significantly lower in the
seedling and pole stages than in the other stages. The concentration
of inorganic P did not depend on stage of stand development except
in the case of mineral P (HCl extractable) where the seedling
stands had significantly lower concentrations of mineral P than
the other stages. This was probably due to different topographical
conditions for the seedling stands as compared to the other stands
which may have affected long term soil processes such as weathering
and leaching. The return of P in litterfall was similar among
stages. The storage of P in stemwood was low in the seedling and
sapling stages but high in the pole and mature stages whereas
the storage of P in coarse woody debris was high in the seedling
and sapling stages but low in the pole and mature stages. The
storage P in the forest floor was significantly higher in the
pole stage than in the other stages which all had similar amounts
of P in the forest floor. The differences in soil organic P forms
among stages of stand development could be explained by above
ground processes such as accumulation of P in stemwood and release
of P from the forest floor and decomposing CWD. Labile and non-labile
pools of soil organic P were correlated with the concentration
of organic C whereas occluded organic P was unrelated to organic
C. Our results suggest that neither labile, non-labile nor occluded
organic P is stable during stand development.
Keywords: Catastrophic disturbance; Coarse woody debris; Forest
floor; Hedley phosphorus fractionation; Stand development』
1. Introduction
2. Methods
2.1. Study site
2.2. P in stem wood and CWD
2.3. P in litterfall
2.4. C and P in forest floor and soil
2.5. Soil P fractions
2.6. Statistical analysis of data
3. Results
3.1. Total ecosystem P
3.2. P in stemwood and CWD
3.3. P in ltterfall
3.4. Total amount of P in the forest floor and soil
3.5. Soil P fractions
4. Discussion
4.1. The chronosequence assumption
4.2. Ecosystem processes and soil P
4.3. Transition between seedling stage and sapling stage
4.4. Transition between sapling and pole stages
4.5. Transition between pole and mature stages
4.6. Transition between mature stage and seedling stage
4.7. Variations in soil P forms and P availability during stand
development
5. Conclusion
Acknowledgements
References