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Johor Fig Remediation Phase 2

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During mid-September 2012, Treescape completed the final tree remediation works for the heritage listed 140-year-old Johor Fig owned by the Singaporean Government agency, Sentosa Leisure Group.

This final stage included a tree health analysis, following the first stage of the tree remediation works. It also including:

  • Vertical mulching
  • Support frame installation
  • Application of compost tea and microbiologically active fertiliser
  • Horizontal mulch installation
  • Borer and fungi management

During the initial phases of the project, Treescape formed a strong working relationship with Singaporean landscaping firm TEHC, which will implement the ongoing 24 month tree maintenance plan, under the supervision of Treescape.

Tree Health and Status

When Treescape revisited the site in mid-September, a full analysis of the tree’s current health status was undertaken.

- Sentosa had had deadwood on the northern limbs removed, and treated the five different insect attacks.
- The southern bow had defoliated another 15%.
- Three new epicormic shoots had developed on the secondary branches of southern bow.
- The borer infestation remained present on the southern bow, even after initial insecticide application.
- Fungi fruiting bodies were observed on the southern bow when the temporary dressing was removed.
- The remainder of the tree canopy displayed a normal foliage colour and foliage density, which indicated no further decline in tree health and vigour.
- The installed moisture barrier had proven effective in preventing water from an adjacent pond moving into the root ball, and soil moisture levels had decreased drastically within the western portions of the root ball. The soil is comprised primarily of reactive marine clay which, when saturated, will expand and contract as moisture levels decrease. As the majority of the soil and root ball are drying out following the moisture barrier installation, the soil is slightly contracting further, exposing surface roots.

Vertical Mulching

Vertical mulching was performed by drilling 52 holes at an approximate width of 150mm, to a soil depth of 700mm. The holes were strategically located amongst the feeder roots and confined within the canopy drip line.

The drilled holes were backfilled with a root favourable soil mix, consisting of 60% soil and 40% cured compost mulch.

Groundwater

High moisture levels and ground water surfacing at a depth of 600mm was observed during soil coring along the southern bow. It was evident that a localised spring was saturating soils to a soil depth of 600mm. Sentosa Leisure Group agreed to run a small sub-drain from the southern bow, that will ensure the ground water does not re-flood the root ball or damage the concrete support footings.

Compost Tea and Microbiologically Active Fertiliser Application

Treescape supervised and monitored the brewing of compost tea comprised of soil inoculums and fungi/bacteria sourced from the adjacent Johor Fig. Subsequently, 1,000 litres of compost tea was directly soil injected into the root ball.

In addition, 2,000 litres of microbiologically active fertilisers were soil injected over a number of days to feed and sustain the freshly established soil microbiology. This will aid improved nutrient uptake by the tree.

Support Frame Installations

Three steel support frames were installed to control torsional movement of limbs one, two and four of the tree, as these were considered the most structurally compromised.

The support frames were partially fabricated by Treescape in Australia and assembled onsite by Sin Yong Ironworks.

The installation was undertaken in accordance with the certified engineering drawing prepared by Westera Partners (Australia).

Horizontal Mulch Installation

Ten cubic metres of cured forest mulch was applied to the surface feeder roots of the tree, to a depth of 100mm and in a six metre radius from the tree trunk. The mulch will help the soil to retain moisture, improve the physical soil structure and create favourable condition s for the microbial life by maintaining even soil temperatures. In addition, the mulch will enhance fig development as extreme or rapid changes in soil temperature halt root growth.

Microbes in the soil will, over time, break down the organic mulches, releasing nutrients into the soil that will function as a slow release fertiliser. The carbon released by the humus-decayed organic matter in the soil will attract moisture from the air on humid days. The mycorrhzial fungi will collect and supply this moisture and nutrients to the tree roots.

A geotextile mulch pillow was fitted to the periphery of the mulch installation to prevent future mulch erosion and wash-out during high rain fall events.

Borer and Fungi Management

All borer activities within the southern bow were intensively treated with Aborsystem stem injection by TEHC. This will be monitored over the next month. In addition, TEHC will send a sample of the fungi fruiting bodies found underneath the temporary dressing, and a sample of the oozing wound on the western limb, to AVA. Subsequently, TEHC will treat these areas with a fungicide.

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