『Abstract
Many studies in ecosystem ecology argue for strong control of
litter quality over nitrogen (N) cycling. We developed a model
for temperate grasslands to test the importance of litter quality
in decomposition for N and phosphorus (P) cycling based on the
following premises. First, terrestrial N and P cycling differ
fundamentally because NB is a structural component of the soil
organic matter (SOM), whereas P is not. Secondly, SOM has a much
lower C:N ratio than litter inputs. Thirdly, litter decomposition
follows an exponential decay with 20％ of the original litter mass
turning into SOM. Fourth, litter N concentration shows an exponential
increase during decomposition, whereas P does not change and is
released proportionally to the litter mass. Based on these premises
we constructed a model which shows that 0.75％ N is a critical
initial concentration at which concentration all N is immobilized
and no N is released from the litter. Thus at 0.75％ N of the litter
all net N mineralization is through SOM decomposition and not
through litter decomposition. Phosphorus, in contrast, is primarily
released in the early stages of litter decomposition. Empirical
tests of these model predictions support the applicability of
the model to temperate grassland ecosystems. This model predicts
that N mineralization from SOM is much more important than mineralization
from litter and that plant litter quality differences alone cannot
explain ecosystem N cycling patterns. Phosphorus, in contrast,
does cycle largely through litter decomposition, and plant litter
quality differences are he dominant factor in determining ecosystem
P cycling feedbacks.
Keywords: decomposition; immobilization; mineralization; nitrogen
cycling; phosphorus cycling; soil organic matter』
Introduction
Terrestrial nutrient cycling
N and P dynamics during litter decomposition: Empirical patterns
from two studies
A null model for decomposition
Model sensitivity simulations
The impact of litter quality; Model predictions
Differences in the efficiency by which litter is transformed
into soil organic matter
Differences in nitrogen and phosphorus concentration in soil
organic matter
Discussion
Acknowledgements
References