Although forests account for only 27% of the total land area, they store approximately 80% of the aboveground carbon (C) and 40% of soil C globally. However, there is currently little information regarding the input and distribution of photoassimilates of trees in plant–soil systems. To quantify the belowground C input and allocation to plant–soil pools, we pulse labeled 5-year-old pioneer (Populus davidiana) and climax (Quercus wutaishanica) species with ¹³CO₂ under field conditions. The ¹³C allocation dynamics were traced in the leaves, branches, roots, and soil microorganisms, rhizosphere and bulk soil under Populus davidiana and Quercus wutaishanica over 21 days. ¹³C recovery (% of assimilated ¹³C) in the leaves of Populus davidiana and Quercus wutaishanica decreased from nearly 90% at 6 h after labeling to 40% and 45% at 21 days, respectively. Continuous assimilate allocation from above- to belowground increased ¹³C recovery in roots from 0.4% at 6 h after labeling to 9.5% in Populus davidiana and from 1.5% to 15% in Quercus wutaishanica at 21 days after labeling. The recently assimilated C was detected in the soil immediately after labeling. The ¹³C amounts in the bulk and rhizosphere soil of the climax species Quercus wutaishanica was two-fold greater than that under the pioneer species Populus davidiana. The total belowground net C input (including that in roots) by Populus davidiana and Quercus wutaishanica was 109 and 283 g C m⁻² yr⁻¹ (top 20 cm of soil), respectively, including rhizodeposition of 4.2 and 28 g C m⁻² yr⁻¹. Consequently, the belowground C allocation and soil C sequestration increase from pioneer to climax tree species.

尽管森林仅占陆地总面积的 27%，但它们在全球储存了大约 80% 的地上碳 (C) 和 40% 的土壤碳。然而，目前关于植物-土壤系统中树木光同化物的输入和分布的信息很少。为了量化地下 C 输入和植物-土壤池的分配，我们在田间条件下用¹³ CO ₂脉冲标记 5 岁的先锋 ( Populus davidiana ) 和高潮 ( Quercus wutaishanica ) 物种。的^13代C分布动力学的叶，枝，根，及土壤中的微生物被追踪，根际和下本体土壤山杨和辽东栎超过 21 天。¹³ Ç恢复（同化的％¹³中的叶C）山杨和辽东栎从接近90％第21天减少在6小时标记后到40％和45％ ，分别。从地上到地下的连续同化物分配使根的¹³ C 回收率从标记后 6 小时的 0.4% 增加到标记后 21 天的杨树的9.5%和五台山栎的1.5% 到 15% 。标记后立即在土壤中检测到最近同化的 C。的¹³ Ç量在高潮物种的体积和根际土壤辽东栎比先锋物种Populus davidiana大两倍。Populus davidiana和Quercus wutaishanica 的地下净 C 输入总量（包括根部）分别为 109 和 283 g C m ^-2 yr ^-1（土壤表层 20 cm），包括 4.2 和 28 g C m ^{- 的}根际沉积²年^-1。因此，地下碳分配和土壤碳固存从先锋树种到高潮树种增加。