Effects of Typical Broad-leaved and Coniferous Forests on Water Quality
in the Qinling Mountains, China
Abstract
Forests in the Qinling Mountains are an important source of fresh water
for 34.68 million people in China. However, heavy metal pollution and
acid rain have recently become common in this region. Forests can
improve water quality; however, a large amount of the Qinling Mountains
is covered by poor quality vegetation. This study investigated the
effects of Quercus aliena var . Acuteserrata (Qa),
Pinus tabulaeformis (Pt), Pinus armandii (Pa), and mixed
broad-leaved (Mb) tree stands on water quality in this region. The
results showed that the four stands increased the pH of slightly acidic
rainfall; this effect was more pronounced in broad-leaved stands than in
coniferous stands. As rainfall was converted to interflow, which is the
most important type of runoff in natural forest, the average SO
4 2- concentrations in broad-leaved
stands were higher in soil horizon A and lower in soil horizon B
compared to coniferous stands. As rainfall passed through the trees,
average NO 3 - concentrations
increased whereas NH 4 + decreased.
Compared to coniferous stands, NO 3 -
and NH 4 + concentrations in soil
horizon A interflow were higher in broad-leaved stands whereas NH
4 + concentrations were lower in soil
horizon B. Average Cd and Pb concentrations decreased remarkably as
rainfall flowed through the stands. Broad-leaved stands led to greater
Cd reduction than coniferous stands. Furthermore, the Mb stand led to
the greatest reduction in Pb concentration. These results will be useful
for selecting the most appropriate tree species for afforestation in
[water-source](app:ds:forest%20for%20water%20resource%20conservation)
regions and in similar areas experiencing air pollution, specifically
heavy metal pollution.