科研之友
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摘要
Forest management requires a profound understanding of how tree species affect C and N cycles in ecosystems. The large C and N stocks in forest soils complicate research on the effects of tree species on C and N pools. In-situ C-13 and N-15 labeling in undisturbed, natural forests enable not only tracing of C and N fluxes, but also reveal insight into the interactions at the plant-soil-atmosphere interface. In-situ dual C-13 and N-15 pulse labeling of 20 beeches (Fagus sylvatica L.) and 20 ashes (Fraxinus excelsior L.) allowed tracing the fate of assimilated C and N in trees and soils in an unmanaged forest system in the Hainich National Park (Germany). Leaf, stem, root, and soil samples as well as microbial biomass were analyzed to quantify the allocation of 13C and N-15 for 60 d after labeling and along spatial gradients in the soil with increasing distance from the stem. For trees of similar heights (approximate to 4 m), beech (20%) assimilated twice as much as ash (9%) of the applied (CO2)-C-13, but beech and ash incorporated similar N-15 amounts (45%) into leaves. The photosynthates were transported belowground through the phloem more rapidly in beech than in ash. Ash preferentially accumulated N-15 and C-13 in the roots. In contrast, beech released more of this initially assimilated C-13 (2.0% relative C-13 allocation) and N-15 (0.1% relative N-15 allocation) via rhizodeposition into the soil than ash (0.2% relative C-13, 0.04% relative N-15 allocation), which was also subsequently recovered in microbial biomass. These results on C and N partitioning contribute to an improved understanding of the effects of European beech and ash on the C and N cycles in deciduous broad-leaved forest. Differences in C and N allocation patterns between ash and beech are one mechanism of niche differentiation in forests containing both species.
- 出版日期2016-6
