Distribution characteristics of mercury concentration and estimation of mercury pools in different age groups of Larix gmelinii forests of Daxing'an Mountain

Forests are important sinks of atmospheric mercury. Quantifying mercury pools in forest ecosystem tissues are essential for understanding the global mercury cycle. To reveal the characteristics of Hg concentration and Hg pool distribution in natural forests at different ages, samples from the vegetation layer, organic horizons, coarse wood debris, and mineral soil layers were collected in young forest, middle forest, near-mature forest, and mature forest of Larix gmelinii forests at the Daxing'an Mountain. The results showed that there were differences in the absorption and accumulation of Hg by different tree species and tissues. In Larix gmelinii, the concentration of Hg followed the order of bark > branch > leaf > root > core, whereas in Betula platyphylla, the order was bark > leaf > branch > root > core. The mercury concentration in the organic horizons increased gradually with the decomposition process. There were no obvious regular patterns in the mercury concentrations of each tissue in different age groups Larix gmelinii forests. Furthermore, total biomass mercury pools (overstory, shrub layer, herb layer, moss layer, and coarse woody debris (CWD)) in the young, middle, near-mature, and mature forests of Larix gmelinii forests at Daxing'an Mountain were estimated to be 99.0 mu g m-2,207 mu g m-2, 207 mu g m(-2) and 194 mu g m(-2), respectively. On ecosystem scale, total mercury pools were 16.9 mg m(-2) (young), 27.5 mg m(-2) (middle), 17.0 mg m(-2) (near-mature), and 11.8 mg m(-2)(mature). The mineral soil mercury pool accounts for 94.0%-98.1% of the total ecosystem mercury pool, and its mercury pool proportion gradually decreased with the increase in forest age. These obtained results are quite valuable for further assessing the role of forest ecosystems in the atmospheric mercury cycle and estimating potential mercury emissions from biomass burning during forest wildfires.

Automated summary

Forests play a significant role in storing atmospheric mercury, and understanding the mercury pools in forest ecosystems is essential for understanding the global mercury cycle. This study investigated the characteristics of Hg concentration and distribution in forests of different ages in the Daxing'an Mountain, revealing differences in Hg absorption and accumulation among different tree species and tissues. The results are valuable for assessing the role of forest ecosystems in the atmospheric mercury cycle and estimating potential mercury emissions from biomass burning during forest wildfires.