Advocate • Connect September/October 2019 53
Farming and horticulture
Forest guilds – two examples
Forest Guilds Principal Primary support Secondary support Herbaceous Rhizosphere Ground cover Climbers- &RRO
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Nothofagus
truncata
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Nothofagus
solandri
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JURXQG Kunzea
ericoides,
Melicytus
lanceolatus,
Hoheria
sextylosaSophora
microphylla
Coprosma
lucidaDianella
nigraAstelia
fragransMetrosideros
carmine,
Metrosideros
perforata- :DUPWR
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Beilschmiedia
tawa,
Nestegis
cunninghamii
%ODFNPDLUH Alectryon
excelsus,
Hoheria
angustifoliaSophora
microphylla,
Coprosma
lucida,
Macropiper
excelsum,
Fuchsia
excorticata,
Alseuosmia
macrophyllaCardamine
debilis
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Dianella
nigra,
Libertia
JUDQGLÁRUDIpomoea
batatas
NŻPDUD Arthropodium
candidum,
Arthropodium
cirratum
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Asplenium
bulbiferumGriselinia
lucida,
Metrosideros
fulgensPPPAbove: An alternative planting pattern (to monoculture) is group planting. This involves 100
groups (of various species) per ha, planted in circles of 19 plants of the same species per circle,
plus 12 pioneering trees as guides (outer circle).sapling plots with their centres at 10-metre
intervals, the forester can establish 100
vigorous and well-formed trees per hectare,
within one human generation.
Each seedling plot can contain a different
tree species. Tree species for each plot may be
selected based on soil depth, rooting pattern,
aspect and community resource needs.
In between the seedling plots, useful fast-
growing pioneer species (outer circle in the
diagram) can be grown for earlier harvest.
To keep this forest improving in vitality
and tree quality over time, it is important
to avoid the boom-and-bust practice of
high grading. The strongest trees of best
form should be left to grow and reproduce,
with each one harvested only after its
descendants are established as saplings.
Ongoing management costs can be offset
by yields of seeds and food and removal of
lesser quality timbers.Choosing species
The natural variability of any landscape
needs to be taken into account when mixing
species. It is crucial to observe site conditions
and understand each species’ requirements.
Native beech trees make excellent
replacements for pine monocultures in
Aotearoa. Ectomycorrhizae associate with
conifers and beech, so young beech trees
benefit from existing mycorrhizal networks
in pine forest soil.
However, pines need to be removed as
the beech saplings are established, because
pines create a fire hazard for native trees,
and compete for water and nutrients. Once
a beech forest is reestablished, its shade
cover will prevent the spread of wilding
pines and eucalypts. However, shade-
tolerant exotic trees such as Douglas fir,spruce and redwood require active control.Tree guilds
Tree guilds can restore habitat vitality and
ecosystem function. Guilds are assemblies
of plant species that have a high degree
of symbiosis. For example, compatible
trees and shrubs have rooting systems
that occupy the soil differently. Including
nitrogen-fixing trees or shrubs, and trees
that generate different types of humus, can
accelerate soil carbon sequestration.
Tree guilds can also be designed
to provide natural resources. Forest
ecosystems can provide local communities
with materials and energy, meeting a
growing need for bioregional self-reliance.
The table gives a couple of examples of tree
guilds for localised reforestation projects.
Water sharing is another way that forest
systems mutually sustain themselves. Duringdrought, deciduous Acer species use their
immense heart-root system to draw water up
from deep in the subsoil and release it into
the topsoil. The closer that young plants are
to these trees, the better they do.Natural resource restoration
It is time to go beyond reforesting for solely
economic or purely altruistic motives.
To succeed in reforesting Aotearoa, we
can plant natives simultaneously or in
succession, but we also need to plant
compatible trees that sustain people and
indigenous life systems.Helmut Janssen is an ecosystem
scientist and nature guide.
Contact: [email protected],
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more on this subject from his book
Bush Vitality Assessment.