Estimation of release efficiencies of leaf litter C, N, and P
We calculated the percentage of release relative to the total content of
an element in the leaf litter as the release efficiency:
\(V_{E,i}=\frac{D_{E,i}}{E}\) (1),
Where DE ,i is the
concentration of dissolved element E (DOC, TDN, or TDP) at dayi and E is the elemental concentration (C, N, or P,
respectively) of the leaf litter added into the bottle. E was
calculated as follows:
\(E=\frac{\mathrm{Litter\ weight\ (mg)\times Litter\ }E\mathrm{\ mass\ (\mu g/mg)}}{0.8\mathrm{(liter)}}\)(2).
We determined the maximal release efficiency
(V max) and half saturation time (k ) of an
element E by fitting the release efficiencyVE,i and sampling day t to the
Michaelis−Menten equation as follows:
\(V_{E,i}=V_{\mathrm{\max}E}\frac{t}{k+t}\) (3).
The fitting was performed by non-linear least-squared regression using
the nls function in the statistical package of R ver. 4.2.2 (R
Core Team, 2022). The coefficient of determination
(r 2) was estimated through correlation
coefficient analysis between the observedVE ,i and estimatedVE ,i from Equation 3.
We further calculated the maximal total release amount (TRA ) of
dissolved element E for the 28-day experiment usingV maxE and E mass in leaf litter:
\(\text{TRA}_{E}=V_{\mathrm{\max}E}\times\mathrm{\text{Litter\ }}E\mathrm{\ mass\ (\mu g/mg)}\)(4).
If V maxE from the Michaelis−Menten fitting
was higher than 100%, we used the maximal release efficiency actually
observed during the experiment (Max-VE ) instead
for further analyses. To compare the C:P and N:P ratios of leaf litter
and leachate, we also estimated the DOC:TDP, DOC:TDN and TDN:TDP ratios
of TRA , i.e., TRA C:P,TRA C:N and TRA N:P.
respectively.