Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences (CAS), Wuhan 430074, PR China; Graduate University of Chinese Academy of Sciences, Beijing 100049, China.
School of Resources and Environmental Science, Huazhong Agriculture University, Wuhan 430074, PR China.
Sci Total Environ. 2020 Jul 1;724:138302. doi: 10.1016/j.scitotenv.2020.138302. Epub 2020 Mar 30.
Large water conservancy project can strongly alter the plant community composition, however, how these changes can potentially affect ecosystem carbon (C) and nitrogen (N) dynamics is not fully understood. Here, we investigated natural C and N abundance of C and C plants and soil in different fractions [labile C (LC) and N (LN), recalcitrant C (RC) and N (RN)]from 6 sites with two elevations (flooding zone, 145-175 m, area with revegetation due to flooding, N = 6); and unflooding zone, >175 m with original plant as a control, N = 3) in riparian zones of the Three Gorges Reservoir, China. The dominant species were the C plants in the upstream including Changshou (CS), Fuling (FL) and Zhongxian (ZX) and the C plants in the downstream in unflooding zone including Wanzhou (WZ) Badong (BD), and Zigui (ZG). C plant in flooding zone was significant decreased by mean 25% compared with unflooding zone in the upstream but significantly increased the by mean 59% in the downstream. The C isotopic differences between soil and plant (ΔδC) was lower than zero in both flooding and unflooding in the upstream, but was only lower than zero in flooding zone in the downstream. The proportion of C-derived C in soil organic carbon pool (average 74.64%) was lower for the flooding zone compared to the unflooding zone (average 87.26%) in most sites, while the proportion of C-derived C in LC (average 44.38%) was decreased in the flooding zone compared to the unflooding zone (69.52%) in the downstream. Additionally, the δN values of soil were higher than plant community in most sites, and were strongly associated with soil C and N pool content, as well as soil pH. Overall, our results revealed that soil C accumulation was primarily determined by C plant in situ and new C input by existing dominant C plant, whereas soil N dynamics was predictably dependent on soil relative C and N availability in response to flooding at regional scale.
大型水利工程会强烈改变植物群落组成，但这些变化如何潜在地影响生态系统的碳（C）和氮（N）动态还不完全清楚。在这里，我们调查了来自中国三峡水库河岸带的 6 个地点（有两个海拔高度：淹没区，145-175 m，因洪水而重新造林的区域，N=6；未淹没区，>175 m，原始植物作为对照，N=3）不同分馏物（易分解的 C（LC）和 N（LN）、难分解的 C（RC）和 N（RN））中 C 和 C 植物以及土壤的自然 C 和 N 丰度。优势物种是上游的 C 植物，包括长寿（CS）、涪陵（FL）和忠县（ZX），以及下游未淹没区的 C 植物，包括万州（WZ）、巴东（BD）和秭归（ZG）。与上游未淹没区相比，淹没区的 C 植物平均减少了 25%，但下游的 C 植物平均增加了 59%。上游淹没区和未淹没区土壤与植物之间的 C 同位素差异（ΔδC）均低于零，但下游淹没区仅低于零。在大多数地点，土壤有机碳库中来源于 C 的 C 比例（平均 74.64%）低于淹没区（平均 87.26%），而 LC 中来源于 C 的 C 比例（平均 44.38%）则低于未淹没区（下游 69.52%）。此外，在大多数地点，土壤的 δN 值高于植物群落，并且与土壤 C 和 N 库含量以及土壤 pH 值密切相关。总体而言，我们的结果表明，土壤 C 积累主要取决于原地的 C 植物和现有优势 C 植物的新 C 输入，而土壤 N 动态则可预测地依赖于洪水作用下的土壤相对 C 和 N 有效性。
