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)
