Species selection Flashcards
You match a species to site to meet the…..
Objectives
Environmental constraints
Failure to effectively meet objectives and enviro constraints leads to…
- Mortality during establishment or later
- Slow growth
- Poor health of trees
- Failure to meet objectives
Species selection Principle
- Consider the reason for tree planting
- Assess the planting site
- Select species that meet objectives (1) and will thrive (2)
- Assess species choices
* Identify any species specific concerns - Produce the tree planting prescription
3 main Reasons for planting…
Enviromental, Social and economic
Environmental reasons for tree planting
− Air temperature
regulation
− Air quality
− Water quality
− Stormwater
attenuation
Social reasons for tree planting
– Aesthetic appeal
– Community
gathering
– Recreation
– Historical link
– Human health
Economic reasons for tree planting
– Real estate value
– Energy
conservation
– Food production
– Wood or fibre
production
Species selection management types
- Low risk management would dictate that you select only species that can thrive on site
- High risk management would dictate that you are willing to risk planting trees that may not be optimally suited to site
Species selection rule of thumb
As the number of objectives and environmental stresses increase, the number of suitable species decreases
NZ soil erosion facts
200-300 million tonnes of soil lost every year to the oceans
10 times the global average
4 forms of soil erosion
Mass movement erosion
Fluvial erosion
Streambank erosion
Surface erosion
Mass movement erosion
Whole slopes slump, slip or landslide. Storms are primary triggers. Common in hill country
Fluvial erosion
H2O gouges shallow channels or deeper gullies in
the soil. Sediment washed into streams.
Streambank erosion
Special case of fluvial erosion. Occurs when banks cleared of trees become unstable
Surface erosion
Wind, rain or frost detaches soil particles from
the surface, allowing them to be washed or blown away. Occurs on any land exposed to wind and rain but occurs largely outside hill country.
Preventing soil erosion
Cover the soil to prevent it
from being exposed to the
elements
Convey water away from
the soil
Preventing soil erosion small and large scale
Small scale → mulch
* Large scale → no effective
man-made solutions, only
vegetation (incl. trees)
Preventing soil erosion in the short and long term
Short term → engineered
solutions (e.g. flumes, chutes,
terracing, pipe drop
structures)
* Medium to long term → trees
How do trees prevent erosion
- Deep, spreading
roots bind soil - Soil pore water
reduced by
transpiration - Tree canopy
reduces rate of
precipitation
reaching soil
Exotic species used for erosion control features
Some commonly planted exotic species
have invasive habits in different what makes them successful in erosion control also contributes to success
Rapid growth in full light (some even
under shade)
* Able to cover large areas because
* Seed dispersed by wind
* Early and prolific seeding
Native species used for erosion control
- Natives typically used in intensive
plantings, without harvesting (i.e.,
permanent forests) - Avoids ‘window of vulnerability’
problem - Slow growth rates (relative to fastgrowing exotics) increase time prior
to canopy closure and root
occupancy
So, ‘window of vulnerability’ exists
with natives too, but is only relevant
to initial establishment, rather than
being cyclical,
Planting Density - Intensive v. Extensive
stems/ha
Window of vulnerability
If intensive plantings are
harvested, land becomes more
vulnerable to erosion
* Increased soil moisture
infiltration
* Decreased root reinforcement
* Canopy closure and root
occupancy of subsequent
rotation reduces vulnerability
Ecological restoration
- Process of assisting recovery of a degraded ecosystem
- Returning to a historic trajectory to recover biotic expressions
- Taking into account native versus exotic species
native, exotic, introduced, naturalised, invasive defs
- Native: developed or evolved over long periods of time in a
particular region or ecosystem - Exotic: not native to the region or ecosystem
- Introduced: exotic and accidentally or intentionally brought into a
region or ecosystem - Naturalised: exotic and capable of establishing and reproducing in a
region or ecosystem - Invasive: exotic, naturalised and also capable of spreading rapidly,
disrupting ecosystem composition or function
Early successional species
- Grow naturally in open conditions
- Grow quickly to outcompete weeds
- Produce seed or fruit to attract dispersers
- Need little maintenance
- Examples include:
- Mānuka (Leptospermum scoparium)
late successional species
- Survive in shade and take advantage of gaps in canopy
- Eventually form dominant forest canopy
- Examples include:
- Miro (Prumnopitys ferruginea)
Restoration options
- Continuum from low to high input management
1. Assisting natural regeneration
2. Direct Seeding
3. Establishing a nurse crop
4. Planting a mixture of quick growing species - Options are not mutually exclusive
Assisting natural regeneration restoration option
- Appropriate for:
- Small degraded areas within/adjacent
to existing mature forest - Requires:
- Nearby seed source of early
successional species - Seedling protection*
- Control of browsing/grazing animals*
Direct seedling
- Appropriate for:
- Most situations, unless immediate cover is needed
- Requires:
- Large quantities of viable seed
- Mild environmental conditions during
germination and seedling stage - Existing vegetation is sparse or nonexistent
- Seedling protection*
Establish nurse crop
- Appropriate for:
- Situations where shelter (radiation/wind) is necessary for
regenerating species - Requires:
- Nearby seed source for late successional species, or
- Follow-up planting with late successional species
- Control of browsing/grazing animals*
- Remove competing grasses and weeds*
- Thinning intervention (selection of vigorous seedlings)*
Planting a mixture of fast growing species
- Appropriate for:
- Situations when rapid cover is desirable or necessary
- Requires:
- $$$
- Control of browsing/grazing
animals* - Remove competing grasses and
weeds* - Thinning intervention (selection of
vigorous seedlings)* - Post-planting irrigation*
- Direct planting of 30 – 60 cm
tall seedlings
Species selection for ecological restoration
- Choose indigenous species that will lead to recovery of
historic trajectory of biotic expression - Choose species that can thrive under current site conditions,
with consideration for future change - Eco-sourcing and seed propagation are good practice for
restoration projects
Restoration Considerations – Eco-Sourcing
- Seeds and seedlings should be
locally-sourced - Avoids hybridisation with
local varieties/species - Avoids displacement of local
varieties/species - Maintains representative
genetic diversity of a species
Restoration Considerations – Seed vs. Cuttings
- In the context of restoration,
there is a preference for
seeds over cuttings - Seeds can be collected from a
diverse range of individuals - Using clonal material
decreases genetic diversity - Reduces resilience to
climate change or pest/disease
outbreaks
Species selection for water management
Vegetation in riparian
zones directly influences
water quality
Water Pollution sources
Urban runoff and Rural runoff and leaching
Urban runoff examples
- Hydrocarbons (oil, fuel, diesel)
- Heavy metals
- Fertilizer, herbicide, pesticide, paint, concrete
wastewater - Sediment
Rural runoff and leaching
- Non-point sources of nitrates and reactive
phosphorus – stock urine, fertilizer, stock waste - E. coli bacteria
- Sediment
What is a Riparian Zone
- Junction between the land and water along a waterway
- Riparian vegetation
- filters sediment
- minimises bank erosion
Objectives in Riparian Management
- Reduce pollutant
loading
* Absorb nitrate and
fertiliser before they
are deposited into
water - Reduce
sedimentation - Reduce streambank
erosion - Provide fish habitat
and breeding
grounds
Therefore you require trees with a large root system, rapid growth, deciduous, large and has a dense crown
Riparian zones
- Low bank zone, high bank
zone, inland filter zone - Soil moisture will range
from standing water to
occasional flooding to moist
(drying out in summer)
Street trees
ignore
- Low bank zone, high bank
zone, inland filter zone - Soil moisture will range
from standing water to
occasional flooding to moist
(drying out in summer)
Street tree benefits
+ Improvements in physical and mental
health, property values, air quality, water
stormwater mitigation, wildlife habitat
+ Reduction in electricity use via shading
(summer), shelter (winter)
+ Prolongs life of asphalt via shading
Street tree drawbacks
− Nuisance via litter or allergens (species
specific)
− Infrastructure damage
− Danger if breakage occurs or shading during
winter months
Objectives for street trees
- Primary
- Provide shade in the summer
- But not winter
- Secondary
- Aesthetically pleasing
- Important considerations
- Minimise conflict with above-ground
infrastructure - Allow for clear sight lines
- Avoid messy litter
- Citizen safety
- avoid limb or stem breakage
Street tree site description
dry soil, compacted, high level of anthropogenic damage
Undesirable street tree fetaures
Fruit, agressive roots, pollen and sudden branch drop
Food, forage and fodder
- Sources of energy eaten by
humans (food) and animals
(forage/fodder) - Animals forage on their own,
but are also fed fodder by
humans - Trees provide renewable
source of nutrition
Forage and fodder during drought
- Stock rely on pasture
- Pasture decline occurs
- End of summer
- During drought
- Trees as forage and fodder
provide energy source for
stock when staple diet fails
Apart of farm drought resilience plan
Due to climate change how will farmers dependance on fodder change?
Climate change in NZ will result in
an increase in droughts Farmers will have
to increase their reliance on fodder
coppicing and pollarding
reserch
Species used for fodder
Poplar
fast growth
relatively large stems
* Less palatable due to size
* Better suited for cows
* Suited to a range of soil moisture
conditions
* Deep roots
* Green foliage during summer drought
* Rapid re-sprouting
Willow
* Very fast growth
* 4-5 times more new shoots than poplar
* Smaller stems than poplar (more
palatable)
* Suited for cows and sheep
* “Pasture-friendly”
* Casts a light shade
* Well suited to wet soil conditions
* Alternative to pasture on wet ground
* Better than pasture under drought
Negative effects poplar and willow can have on other crops
- Tree cover can
negatively affect
pasture through: - Shade effects
- Root competition
- “Rainshadow” effects
spatial layout for fodder
- Long tree-crop interface
needs neutral or
complementary tree
species - Row planting enables row
by row browsing with an
electric fence to ration
fodder
When purchasing tree your specification must not only include the species type you also need to specify
- Size
- Root characteristics
- Trunk characteristics
- Crown characteristics
- Canopy health
Not specifying can lead to compromises
Size in tree specification
- Good and bad tree stock comes
in all sizes - Size of planting stock purchase
will depend on - Objective
- Immediacy of desired impact
- Budget
- Larger trees cost more to produce
and establish - Post-planting care
- Larger trees more likely to require
irrigation, staking, etc.
Root characteristics- root collar
Root collar should be
visible or buried no more
than 2 cm beneath soil
surface
* Buried root collar suggests
tree may be planted too
deep
Root defects
- Kinks
- Circling roots
- Girdling roots
- Pot-bound roots
Visibility of defects can depend on production
method
* May need to remove root ball from pot/bag,
remove burlap, or remove soil from top of root ball
An ideal root system
- Has roots radiating outward from the trunk
- Forms a wide root plate
- Has dense fibrous nature
How to correct root defect
- Correct kinks by pruning behind the defect
- New root growth will be instigated
behind the point of pruning and
extend outwards - Root defects can be corrected
when stock is: - Re-planted into next largest
container size - Transplanted into field`
Trunk characteristics
- Tree height less important
than trunk diameter - Diameter at root collar is
critical - Trunk diameter is indicative
of carbohydrate reserves
critical during
establishment - Tree standing without
support of stake is
suggestive of appropriate
trunk diameter and taper
Excurrent trunk
strong apical
dominance
Straight vertical with the clear leader
- Single leader
- Typically a cone shaped crown
- Central leader diameter
exceeds branch diameters - Leader diameter 2x branch
diameter
trunk wounds
sun scald, fungal
fruiting bodies, cracks,
boring damage, girdling
from ties
Crown charateristics
Branches should not touch or rub
against one another, nor be
broken or dead
* Branch unions
* Strong attachments are critical
* Visible branch ridge
* Included bark results in weakness
* Branch distribution
* Clustering should be avoided
(except in case of whorls in conifers)
Tree health
- Current year’s shoot extension
should be ‘normal’ for the species - Size and colour of leaves should
be ‘normal’ for the species - Dependent on time of year
- May require prior knowledge or
comparison to others in same
cohort - No signs of pest or disease
