Choice of Species
Forest growers have an opportunity to choose
the species mix and the genetic origins of the plants they
are going to grow on their farm. They can also reduce or increase
the prevalence of existing species. These genetic choices
can be based on:
the known performance of a particular species or variety,
an inclination towards indigenous or introduced genetic
a preference for greater or lesser genetic diversity.
Introducing new genetic material can irreversibly change the
genetic composition of existing vegetation in the area. This
can happen through hybridisaiton or interbreeding and can
be very difficult to reverse in the future. Another consideration
is that native genotypes lost from a site may be expensive
or impossible to recover. So, farmers need to think carefully
and strategically before making a decision about the genetic
composition of a forest.
After deciding which species to plant, farmers have several
choices about how they obtain their planting stock. These
seedfrom direct seeding,
seedlingsin various sized pots or open rooted,
clonal stockproduced from grafting or budding
root stock or stem or root cuttings.
Availability and cost, although important, are not the only
factors farmers need to think about. They should also consider:
the planting techniques they expect to use
the need for particular site preparation treatmentssuch
the shelf life of the planting stock
the need to protect seed/stock from vermin.
There is enormous genetic variability within almost every
tree species. Forest farmers need to consider growth rates,
frost resistance, branching habit, flowering times and wood
characteristics. There are seed-lots (or provenances), improved
seed varieties and clones available to provide the characteristics
farmers are looking for in most instances.
Because intensive tree breeding and clonal selection can be
complex and expensive, some industrial forestry organizations
are participating in cooperative breeding programs. These
concentrate on improving particular traits in a limited range
of species. Landowners may be able to benefit from this work
if they are able to buy stock selected for criteria similar
to, or compatible with, their needs. For example, a pulpwood
company may select trees of high wood density, small branches
and high growth rates. These characteristics may also be desirable
for a grower interested in the same species for sawlog production.
However, there is a risk that a breeding program will overlook
important attributes that would make the improved seed less
suited for some uses. For example, growth stresses, reaction
wood or spiral grain may be overlooked in a breeding program
focused on pulpwood production making the improved
seed inappropriate for sawlog production.
Tree breeding has improved growth and productivity across
several forestry and horticultural species. Despite these
improvements, farmers should be cautious about planting a
forest with a very narrow genetic base. The extreme example
is a clonal forest common in poplarswhere there
is no genetic difference between the individual trees. The
complexity of the interaction between the genetics and the
environmentand the long time periods involved in forestrymean
that maintaining a broad genetic base is often a sensible
risk management strategy. Where particular selections of either
species or varieties appear preferable, the farmer could choose
to incorporate a number of the more promising into a mixed
planting instead of choosing just one.
Indigenous or native tree species are generally thought to
be well adapted to the local soil and climatic environment.
However, in most farming situations the current environment
in which trees will grow may be very different to that of
the original native forest. In many areas farming practices
have resulted in significant changes in the soil properties
due to pasture and crop management, fertiliser application,
waterlogging and land degradation. There may also be different
pests and diseases and greater exposure to winds and frosts
than was the case prior to settlement of the area.
Growers should keep records of seed or plant sources and their
genetic origins. These will help identify the best performing
genetic material for use in later plantings, and might also
help in the marketing of tree products such as seed, cuttings
Tree species for
Some trees can
and seed suppliers
Back to top