Geoscience Reference
In-Depth Information
nevertheless contain a variety of useful tree species, some providing firewood and
others fruit and a source of traditional medicines. Formerly, the native forest was
denser than the pine plantations and the understorey helped to stabilise the soil and
protect against erosion. Most of the tree species are suitable for pollarding. When
used for this purpose rather than for timber, they provide permanent stability to the
soil. Some trees can be successfully pollarded for a hundred years, and expanding
this practice in Nepal would substantially reduce erosion and landslides.
Development Aid Meets with Mixed Success
Development aid projects often fail because donors work exclusively through con-
tacts at government level rather than focusing directly on local communities. Yet
some reforestation projects have been successful in the Himalayas in recent years.
Nepal's forests are state-owned but responsibility for their management is some-
times entrusted to local villages, resulting in better husbandry and the planting of
more appropriate tree species.
Through Ecoslopes, a former research project financed by the European Union,
I came into contact with a successful village forestry project run by a team of
Austrian scientists and local communities in the Kathmandu Valley. Ecoslopes
brought together researchers from all over the world to develop ways to use plants
to repair and restore areas prone to landslides. Previous initiatives in Nepal had
been unsuccessful due to difficulties in getting active cooperation from villagers
during spring and summer, when they were busy with farming. The Ecoslopes
team addressed this by experimenting with winter tree planting, trialling both
native and non-native species with bamboo frames to hold the soil in place and
support the saplings. Bamboo is a cheap and widespread resource in Nepal and
bunches of canes were fixed in the ground with the help of poles. Many of the sap-
lings survived and also withstood the monsoon.
The trees that fared best were Indian willow ( Salix tetrasperma ) and Nepalese
alder ( Alnus nepaliensis ). The latter proved especially suitable for planting on soil
recently exposed to the elements, including land damaged by a landslide. Such
soils lack nitrogen, a key element needed to form the proteins on which all organ-
isms rely for nourishment. Nitrogen is absent from rock but comprises eighty
percent of the air we breathe. The problem is that it takes a lot of energy to turn
nitrogen from the air into a form that plants can absorb. A few families of bacteria
can perform this taskā€”and it is with these that the Nepalese alder has a reciprocal
relationship. The bacteria grow in nodules on the alder's roots and use energy-rich
carbohydrates provided by the tree to fix nitrogen. The nitrogen makes the soil
more fertile and also leads to an increase in humus when nitrogen-fixing plants
colonise the soil. The addition of nitrogen is often critical for successful restora-
tion of the soil because nitrogen disappears when the topsoil is washed away by
rain or landslides. Adding organic matter to the soil increases sapling growth and
survival rates by benefitting the mycorrhizal fungi that help the trees to absorb
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