“PROPUESTA DE MEJORA DE LA MATRIZ DE INDICADORES PARA RESULTADOS”

A stratified random sample of public greenspaces in Wellington City was selected for sampling from within the kākā extent polygon (

Figure 3.1). All greenspaces with known damage were selected (n = 5), and the remaining 10 sites were randomly selected. All sites were publically accessible Wellington City Council owned or managed areas.

A starting location for sampling within a site was randomly selected on a map of the site prior to my arrival and searching took place from this point until a damaged focal tree was found. This focal tree and the nine closest trees with overlapping canopies were defined as a group for the purposes of sampling. A tree group was defined in this way to be both tree-centric; as nearby trees exert competitive pressures on each other, and kākā-centric; as kākā will often climb and walk between trees along adjacent branches rather than flying. If fewer than nine trees formed a continuous canopy with the focal tree, all trees in the group were sampled. As kākā select mature trees for sap feeding, all trees sampled had a minimum DBH of 5 cm to exclude herbaceous plants and tree saplings. Tree species were not sampled in accordance with availability due to the relative rarity of sap feeding damage.

The focal tree and each of the nine neighbours were sampled for a suite of 12 variables: seven describing individual tree characteristics and five describing their microhabitat and distribution on the landscape. These variables were generated from previous research of sap foraging in kākā and other species, and preliminary observations in Wellington (Charles 2012).

Tree height; calculated using a hand held clinometer, species and diameter at breast height (DBH, measured at 1.3 m) were recorded. A 50 mm diameter circular section of the outer bark layer (the rhytidome) was removed from a randomly selected point at breast height on the trunk of each tree using a hole saw to drill through the outer bark layer to expose living phloem tissue. Bark thickness was calculated as the mean of the bark thickness at three randomly

47 selected points on the edge of each circle of bark removal. Bark type was

categorised as smooth or ridged. Decorticating bark was included in the smooth bark category as the bark surface was smooth below shed bark.

Cambial electrical resistance and solute concentration of phloem tissue were assayed to provide a relative estimate of the energy available from sap feeding. Solute concentration of phloem tissue was measured in a similar way to that used by Martinez-Trinidad (2010). A piece of tissue 25 x 10 x 2mm was excised from where the phloem had been exposed due to bark removal and placed in a vial with 1 ml distilled water. After 48 hours, 0.3 ml of water was tested using a hand-held refractometer (Atago Pocket PAL-06S) and salinity values were converted to Degrees Brix (1°Bx = 1 gram dissolved solid in 100 grams of solution). As sap is composed mainly of sugars (Stewart et al. 1973; Snyder 1992), this provides a measurement of relative carbohydrate concentration (Goldingay 1987).

Cambial electrical resistance was assayed in a manner similar to that used by Eberhardt (2000). Stainless steel electrodes of a DSE Q5300 digital multimeter were inserted vertically 20 mm apart into the exposed phloem layer to a depth of approximately 5 mm. The minimum electrical resistance from 5 minutes of a pulsed electrical current was recorded at two points and averaged to provide a mean value of cambial electrical resistance (CER). CER measures the resistance to movement of an electrical current through the cambial tissue, which has been found to correlate with growth rate, phloem width (Carter & Blanchard 1978) and live bark thickness (Kile et al. 1982). High vigour, wider phloem and thicker live bark all indicate a greater turnover of sap sugars and higher sugar availability to feeders (Mackowski 1988). Studies of yellow-bellied glider sap feeding have suggested that this species selects trees with lower CER (Mackowski 1988; Eberhardt 2000).

Microhabitat variables; aspect and TOPEX (topographic exposure) were

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Aspect was a binary variable describing a site as north or south facing. TOPEX values were calculated as the sum of the inclination to the horizon at each of the eight cardinal points. Tree density was measured as the number of live trunks ≥ 5 cm DBH within a 10 m radius of each sampled tree.

For each tree group, the shortest distance to the KWS fence, where kākā were released and supplementary food is available, was calculated using Google Earth (Version 5.1.3533.1731, Google Inc. 2009). Human disturbance was measured as the minimum distance from each tree group to a building or road also using Google Earth.

Trees were inspected using binoculars to identify bark damage caused by kākā. Sap feeding damage was identified as removed patches or transverse gouges in bark of the trunk or branches such that the outer and inner bark layers were removed to expose the vascular cambium underneath, which remained intact or superficially damaged. Bark chips on the ground below the tree often signalled the presence of kākā damage. If damage was observed, the type, location, height and extent were recorded. Damage was identified as being present on the lowest, middle and/or top third of the tree and located on the main bole and/or lateral branches. The extent of bark damage was estimated by sight as a

percentage of total bark area for each tree. The health of each tree was assessed by estimating the foliage loss and browning as a percentage of the total canopy of the tree.

Up to three tree groups, each of up to ten trees, were sampled at each site. If a damaged tree was not identified after 60 minutes of searching at a site, damage was assumed to be negligible or absent and three randomly selected focal trees and tree groups were sampled.