Key Laboratory of Soil Ecology and Health in Universities of Yunnan Province, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650500, PR China.
Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences (CAS), Wuhan 430074, PR China.
Environ Pollut. 2022 Jan 15;293:118599. doi: 10.1016/j.envpol.2021.118599. Epub 2021 Nov 27.
Human activities such as dams disturb the structure and function of wetlands, triggering large soil CO and CH emissions. However, controls over field CO and CH emissions and their carbon isotopic signatures in reservoir wetlands are not yet fully understood. We investigated in situ CO and CH emissions, the δC values of CO and CH, and associated environments in the saturated and drained states under four elevations (i.e., the water column, <147 m, permanent inundation area without plants; the low, 145-160 m, frequently flooded area with revegetation; the high, 160-175 m, rarely flooded area with revegetation; and the upland area as the control, >175 m, nonflooded area with original plants) in the Three Gorges Reservoir area. The CO emissions was significantly higher in high elevation, and they also significantly differed between the saturated and drained states. In contrast, the CH emissions on average (41.97 μg CH m h) were higher at high elevations than at low elevations (22.73 μg CH m h) during the whole observation period. CH emissions decreased by 90% at low elevations and increased by 153% at high elevations from the saturated to drained states. The δC of CH was more enriched at high elevations than in the low and upland areas, with a more depleted level under the saturated state than under the drained state. We found that soil CO and CH emissions were closely related to soil substrate quality (e.g., C: N ratio) and enzyme activities, whereas the δC values of CO and CH were primarily associated with root respiration and methanogenic bacteria, respectively. Specifically, the effects of the saturated and drained states on soil CO and CH emissions were stronger than the effect of reservoir elevation, thereby providing an important basis for assessing carbon neutrality in response to anthropogenic activities.
人类活动，如修建水坝，会扰乱湿地的结构和功能，引发大量土壤 CO 和 CH 排放。然而，水库湿地中田间 CO 和 CH 排放及其碳同位素特征的控制仍未完全了解。我们在三峡库区四个海拔高度（即水柱、<147 m、无植物的永久性淹没区；低海拔、145-160 m、常淹且有植被的区域；高海拔、160-175 m、偶淹且有植被的区域；以及作为对照的高地，>175 m、无植物的非淹没区）下，调查了原位 CO 和 CH 排放、CO 和 CH 的 δC 值以及饱和和排水状态下的相关环境。在高海拔地区，CO 排放显著较高，且在饱和和排水状态之间也有显著差异。相比之下，在整个观测期间，CH 排放的平均值（41.97μg CH m h）在高海拔地区高于低海拔地区（22.73μg CH m h）。在低海拔地区，从饱和到排水状态，CH 排放减少了 90%，而在高海拔地区则增加了 153%。CH 的 δC 在高海拔地区比在低海拔和高地地区更丰富，而在排水状态下比在饱和状态下更贫化。我们发现，土壤 CO 和 CH 排放与土壤基质质量（如 C:N 比）和酶活性密切相关，而 CO 和 CH 的 δC 值主要与根呼吸和产甲烷菌有关。具体来说，饱和和排水状态对土壤 CO 和 CH 排放的影响强于水库海拔的影响，从而为评估人为活动引起的碳中和提供了重要依据。
