Bush Ecology
Patterns of balance and interaction in a coastal broadleaf-podocarp forest
Layers
A fully functioning bush structure is comprised of a number of horizontal layers:
1 • Bush Floor
- decaying litter, new seedlings & low-growing plants
2 • Sub-canopy - shrubs & small trees, vines & epiphytes, tree ferns & nikau
3 • Canopy - established, mature canopy species
4 • Emergents - tallest trees, usually growing as individual specimens
Edge
The bush edge
is the interface between the bush core and open grassland. This area is exposed to sunlight & wind, leading to lower humidity & greater temperature fluctuations compared to the bush interior - only certain species will thrive in these conditions.
Succession
Regenerating bush passes through a series of successional plant communities, each overwhelming the one before, until the climax community is reached. Each stage, beginning with pioneers such as kanuka, improves the growing conditions sufficiently to allow the next succession to establish.
Canopy
The bush canopy acts as a 'continuous lid', keeping in humidity & protecting the interior from strong sunlight. Canopy species, such as puriri, are adapted to full sun exposure - when they die & collapse a light well is created towards which replacement canopy seedlings grow.
Sub-canopy
The bush subcanopy layer is composed of shade-tolerant species and as most are adapted to higher humidity levels they often don't thrive at the bush edge. These plants are generally dependent on their surrounding vegetation, either for protection from the sun & wind or for physical support (vines & epiphytes).
Emergents
The upper bush layer is not continuous but instead made up of various individual trees which have pushed through the canopy layer, such as kauri & tanekaha. These emergents often grow straight up without branching until they reach open sunlight where their form then becomes multi-branched.
Regenerating Bush Composition
Evolving plant communities on Te Matuku Point:
• Tea tree/broadleaved/tree fern shrubland
• Mixed coastal broadleaved forest
• Tea tree-dominant scrubland
• Pohutukawa coastal forest strip
• Broadleaved/kowhai tidal creek forest
• Estuarine margin brackish shrubland
Remnant Bush Composition
In nearby Omaru Bay, unlike Te Matuku Point, species-rich bush remnants still remain:
• In a gully lies taraire, with large emergent kahikatea
• Further up the slope, a mixed forest consisting of mamangi, rewarewa, tawa, miro & lancewood.
• Up on the exposed ridge is kanuka, with some pohutukawa, kauri & tanekaha
Auckland City District Plan - Hauraki Gulf Islands Section
Bush Health
There are a number of signs to look for when assessing general bush health:
1 • Evidence of pest & grazing stock damage
2 • Condition of bush floor litter & seedling population
3 • Weed levels - high or low
4 • Canopy condition - intact or in decline
5 • Watch & listen for birdlife
6 • Bush edge - intact or exposed
