Geoscience Reference
In-Depth Information
Growth with precision
. Will forests grow faster when levels of atmospheric carbon dioxide rise?
If they do, they might temporarily slow the rate of climate change by absorbing more carbon
dioxide from the atmosphere. Researchers in the Alps are studying how increased atmospheric
carbon dioxide is affecting trees near the
treeline
. The precision screw in the photo measures the
tree's growth. Launched in 2001, the experiment has yet to record any increase in growth; experts
believe another—as yet unexplained—factor is limiting the trees' growth
earthworms. Like earthworms,
enchytraeids
also dig tunnels in the soil, though
they frequent the uppermost soil layer and do not mix the earth in the same way as
earthworms. If you cut a cube of peat and add a few
enchytraeids
to it, the soil will
look like Swiss cheese after a few days.
British scientists conducted an experiment in which they heated the soil surface to
a temperature of 3° higher than normal. This resulted in the water in nearby streams
turning brown because
enchytraeids
, the predominant form of animal life, tunnelled
deeper underground when the hotter soil dried out. This led to increased soil aera-
tion, accelerating the rate of decomposition and in turn leading some of the organic
matter to become water-soluble and to seep with the water through the soil and into
the streams. Episodes of brown water discolouration have increased both in the UK
and Sweden in recent years, perhaps due to behavioural changes in
enchytraeids
.
There are other potential explanations, too. Massive increases in sulphur emissions
from industry in the twentieth century saw atmospheric sulphur react with raindrops
to form sulphuric acid, which fell to the ground as acid rain. Acidification made the
water in rivers and streams clearer because the substances that made the water murky
precipitated when the pH fell. A reduction in acidification in recent decades has seen
surface water regain its brownish tinge.
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