**4.1 Case study establishing space-planted kanuka on pastoral land**

In July 2021, 30 kānuka seedlings (*Kunzea ericoides*) were planted on two aspects (North and South) on three hill country pastoral farms with contrasting rainfall (**Table 1**). Seedlings were grown in root trainer pots and at planting were on average 52 cm tall (minimum: 29 cm; maximum: 69 cm). The seedlings were protected using a plastic mesh tube and supported by two steel Y-posts and a steel rebar (**Figure 4**). Weather stations were installed on both aspects at each farm to measure rainfall. The weather station rain sensors at the Gladstone sites malfunctioned on both aspects, so rainfall data for this farm was used from a local weather station. Livestock (sheep, cattle) were continuously grazing at all sites. There have been three measurements so far on the trees (**Table 1**), although the third measurement (t3) was not undertaken at Ahuriri because a recent storm event (Cyclone Gabrielle) had made the site inaccessible. Any seedling deaths between the planting date and measurement 1 (t1) were likely related to root desiccation following planting.

Rainfall at the Ahuriri north and south slopes was 1447 and 1417 mm in 2022, respectively, and it was 1807 and 1828 mm at Taumarunui north and south, respectively. The rainfall at the Gladstone site was 1230 mm in 2022. The mean heights at t1, t2, and t3 for all the seedlings over all the sites were 62.7, 93.3, and 153.1 cm, respectively (**Figure 5**). This represented an average growth of 9.9, 40.8, and 100 cm at t1, t2, and t3, respectively. Seedling survival was varied. At t3, 70% of the seedlings survived at Gladstone north, 90% survived at Gladstone south, 96.4% survived at Taumarunui north, and 93.3% at Taumarunui south. At t2, 83.3% of the seedlings survived at Ahuriri north and 72.0% survived at Ahuriri south. There were 0% shock deaths at Taumarunui, 8.3% at Gladstone, and 21.8% at Ahuriri. Livestock damaged the protectors of 0% of the seedlings at Gladstone, 8.3% at Ahuriri, and 4.8% at Taumarunui.


It is likely that the higher rainfall at Taumarunui resulted in the higher growth rate of kānuka at this farm at t3 compared to Gladstone. Kānuka growth was higher on

#### **Table 1.**

*Site information, planting and measurement dates for the kãnuka establishment trial.*

*Drivers and New Opportunities for Woody Vegetation Use in Erosion Management in Pastoral… DOI: http://dx.doi.org/10.5772/intechopen.112241*

#### **Figure 5.**

*Kānuka heights after measurements t2 and t3 for each aspect (north and south) and the three farms (Ahuriri, Gladstone, Taumarunui).*

the drier and warmer North facing slopes, though the two drought-prone sites had exceptional wet summers in both 2021–2022 and 2022–2023. Further analysis after the trial has finished will compare rainfall data with morphometric data (e.g., slope) to provide a better understanding as to the drivers of seedling survival and growth. The average growth rates for the poplar clones in **Figure 1** after year 2 were between 2.0 and 6.2 m. The kānuka seedlings grew on average 1.5 m at t3, although will likely grow slightly more until the end of year 2 (July 2022). This gives evidence that the kānuka would stabilize slopes more slowly than poplar. However, kānuka may take a similar time to reach maturity height because kānuka is a smaller tree (10–20 m) than poplar (25–35 m) when fully grown. Rate of root extension of young kānuka or root biomass and distribution of mature kanuka in space planted systems, features important for erosion control, are yet to be researched.
