Fine root turnover continuously contributes to the pool of dead soil organic matter in temperate forest ecosystems. In general, these processes are reported as estimates of fine root survivorship, which differ widely among fine root orders and tree species. Over a three-year period, we tracked fine root persistence visible from trenched minirhizotron tubes, where all roots visible had been severed from the tree, among nine temperate tree species in a 33-year-old common garden planting near Siemianice, Poland. Vital staining was used to determine duration of severed fine roots until death while root diameter was used to categorize root orders into lower, 1st and 2nd and higher, 3rd and 4th order fine roots.
Results/Conclusions
Across species, fine root death occurred within 5 months after roots were severed. From the time of fine root death, root persistence (roots remaining visible) was in general shorter for 1st and 2nd order roots than higher order roots among species, except for two conifers. For Abies alba and Picea abies, root persistence was shorter for higher order roots than lower, 1st and 2nd order roots. After two and a half years, 60-80% of dead fine roots disappeared from view, which suggests nearly total decomposition of the visually tracked, dead fine roots. Only fine roots of Pinus sylvestris had a substantial fraction that remained visible after 2.5 years, with up to 60% persisting by the end of the study in both fine root categories. Variation of fine root persistence among species did not show a relationship to traits such as N:C ratio, median root lifespan or leaf litter decomposition constants, indicating controls over fine root decomposition are independent from many other plant traits.
