College of Resources and Environment, Southwest University, Chongqing, 400715, China.
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China.
Environ Pollut. 2022 Jan 1;292(Pt B):118449. doi: 10.1016/j.envpol.2021.118449. Epub 2021 Nov 2.
Litterfall mercury (Hg) input has been regarded as the dominant Hg source in montane forest floor. To depict combining effects of vegetation, climate and topography on accumulation of Hg in montane forests, we comprehensively quantified litterfall Hg deposition and decomposition in a serial of subtropical forests along an elevation gradient on both leeward and windward slopes of Mt. Ailao, Southwest China. Results showed that the average litterfall Hg deposition increased from 12.0 ± 4.2 μg m yr in dry-hot valley shrub at 850-1000 m, 14.9 ± 6.8 μg m yr in mixed conifer-broadleaf forest at 1250-2400 m, to 23.1 ± 8.3 μg m yr in evergreen broadleaf forest at 2500-2650 m. Additionally, the windward slope forests had a significantly higher litterfall Hg depositions at the same altitude because the larger precipitation promoted the greater litterfall biomass production. The one-year litter Hg decomposition showed that the Hg mass of litter in dry-hot valley shrub decreased by 29%, while in mixed conifer-broadleaf and evergreen broadleaf forests increased by 22-48%. The dynamics of Hg in decomposing litter was controlled by the temperature mediated litter decomposition rate and the additional adsorption of environmental Hg during decomposition. Overall, our study highlights the litterfall mediated atmospheric mercury inputs and sequestration increase with the montane elevation, thus driving a Hg enhanced accumulation in the high montane forest.
凋落物汞（Hg）输入被认为是山地森林地表的主要 Hg 源。为了描述植被、气候和地形对山地森林 Hg 积累的综合影响，我们在中国西南哀牢山迎风坡和背风坡沿海拔梯度的一系列亚热带森林中综合量化了凋落物 Hg 沉降和分解。结果表明，平均凋落物 Hg 沉降从 850-1000 m 干热河谷灌丛的 12.0 ± 4.2 μg·m yr 增加到 1250-2400 m 的混交林和阔叶林的 14.9 ± 6.8 μg·m yr ，到 2500-2650 m 的常绿阔叶林增加到 23.1 ± 8.3 μg·m yr。此外，由于更大的降水量促进了更大的凋落物生物量产生，迎风坡森林在相同海拔高度具有显著更高的凋落物 Hg 沉降。一年的凋落物 Hg 分解表明，干热河谷灌丛凋落物中的 Hg 质量减少了 29%，而混交林和常绿阔叶林则增加了 22-48%。凋落物分解中 Hg 的动态受温度介导的凋落物分解率和分解过程中环境 Hg 的额外吸附控制。总的来说，我们的研究强调了凋落物介导的大气汞输入随着山地海拔的升高而增加，从而导致高山森林中 Hg 的积累增加。
