## 3 Results
### Fine-Root Lifespan and Turnover Rate  
Estimations of the fine-root lifespan, the turnover rate, and their confidence intervals are reported in Table 3, while a comparison of the statistical significance among the Kaplan-Meier survival curves is reported in Table 4. The estimations on the median lifespan and the turnover rate in the fine-roots per species ranged from 440 days and 0.83 year\({}^{-1}\) in birch to 470 days and 0.78 year\({}^{-1}\) in beech, respectively (Table 3). The Kaplan-Meier survival curves of the fine-roots also differed significantly among the species (Table 4). However, within one species, there were also significant differences in the estimations of the median lifespan and the turnover rate between roots with a different diameter class or season of birth. For example, for oak, estimations for the median lifespan and the turnover rate per root diameter class ranged from 241 days and 1.51 year\({}^{-1}\) for the fine-roots below 0.5 mm to 526 days and 0.69 year\({}^{-1}\) for the fine-roots above 2 mm, respectively. Likewise, estimations of the median lifespan and root turnover rate per season of root birth in birch ranged from 379 days and 0.96 year\({}^{-1}\) for the fine-roots born in autumn to 626 days and 0.58 year\({}^{-1}\) for the fine-roots born in winter (Table 3). For beech and oak, the variability in the fine-root lifespan across diameter classes was larger than the variability in the fine-root lifespan across the season of root birth. For birch, the trends were opposite. Figure 5: The bud burst (**A**), chlorophyll content index (CCI; **B**), and distribution of the phenological transition dates (a proxy for the onset of senescence; **C**) of the mature _Fagus sylvatica_ (\(n_{\rm KS}=4\); \(n_{\rm PB}=4\)), _Quercus roburt_ (\(n=4\)), and _Betula pendula_ (\(n=4\)) trees at the Klein Schietveld and Park of Brasschaat. Dots and error bars represent the mean bud burst phase and CCI with standard errors, respectively. The purple and yellow colors represent the sampling years 2019 and 2020, respectively. The four bottom plots show the relative ecological timing of the mean bud burst and the mean phenological transition date per site and species. Days were counted from the first of January 2019. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & & \multicolumn{6}{c}{**Survival Curve Per Species (with Root Diameter < 2 mm)**} \\ \hline
**Species** & **n** & **Events** & \multicolumn{2}{c}{**Mean Lifespan**} & \multicolumn{2}{c}{**Median Lifespan**} & \multicolumn{2}{c}{**Root Turnover Rate**} \\  & & & **(Days)** & \multicolumn{2}{c}{**(Days)**} & \multicolumn{2}{c}{**(Year\({}^{-1}\))**} \\ \hline  & & & **Mean** & **Mean** & **Mean** & **Lower** & **Upper** & **Rate** & **Lower** & **Upper** \\  & & & **Mean** & **SE** & **Median** & **(Days)** & **(Days)** & **(Year\({}^{-1}\))** & \\ \hline _Fagus sylvatica_ & 4272 & 4165 & 412 & 3 & 470 & 463 & 470 & 0.78 & 0.79 & 0.78 \\ _Quercus robur_ & 2511 & 2434 & 442 & 4 & 460 & 447 & 468 & 0.79 & 0.82 & 0.78 \\ _Betula pendula_ & 6529 & 6228 & 426 & 3 & 440 & 408 & 470 & 0.83 & 0.89 & 0.78 \\ \hline \multicolumn{10}{c}{**Survival Curve for _Fagus sylvatica_ Per Root Diameter Class**} \\ \hline
**Root Diameter Class** & **n** & **Events** & \multicolumn{2}{c}{**Mean Lifespan**} & \multicolumn{2}{c}{**Median lifespan**} & \multicolumn{2}{c}{**Root turnover rate**} \\  & & & **(Days)** & \multicolumn{2}{c}{**(Days)**} & \multicolumn{2}{c}{**(Year\({}^{-1}\))**} \\ \hline  & & & **Mean** & **Mean** & **Lower** & **Upper** & **Rate** & **Lower** & **Upper** \\  & & & **Mean** & **SE** & **Median** & **(Days)** & **(Days)** & **(Year\({}^{-1}\))** & \\ \hline \multicolumn{10}{c}{**Survival Curve for _Quercus robur_ Per Root Diameter Class**} \\ \end{tabular}
\end{table} 
Table 3: Estimations of the mean and median fine-root lifespan (days) and fine-root turnover rate (year\({}^{-1}\)) using Kaplan-Meier survival analyses.