How ambient temperature rise affects mercury dynamics and its pools in secondary forests

Area of Science:

• Environmental Science
• Ecosystem Dynamics
• Biogeochemistry

Background:

• Secondary forests are crucial for atmospheric mercury (Hg) deposition, primarily accumulating in soils.
• Global forest cover is increasingly dominated by secondary forests, making them vulnerable to temperature shifts.
• The effects of rising temperatures on mercury dynamics in these sensitive ecosystems are not well understood.

Purpose of the Study:

• To quantify mercury inputs, outputs, and mass balances in two Chinese secondary forests with differing ambient temperatures.
• To investigate the impact of elevated temperatures on mercury methylation, export, and deposition within forest ecosystems.

Main Methods:

• Field measurements of mercury deposition and emission.
• Analysis of litterfall biomass and soil mercury accumulation over 34 years.
• Comparison of mercury dynamics between two secondary forests experiencing different temperature regimes.

Main Results:

• A ~1.0°C temperature increase advanced leaf germination and extended the growing season, leading to higher litterfall biomass and a thicker litter layer.
• Elevated temperatures enhanced mercury methylation and methylmercury export, increasing potential exposure risks.
• Higher temperatures resulted in increased soil mercury emissions and significant mercury deposition via litterfall, leading to net annual mercury accumulation in topsoil.

Conclusions:

• A ~1.0°C temperature rise can increase the role of secondary forests as atmospheric mercury sinks by 45.10%.
• Climate warming significantly influences mercury cycling and accumulation in forest soils.
• Further research is crucial to understand the implications of climate change on mercury dynamics in forest ecosystems.