Ecological study of Hickford Park and coastal walkway route options

An ecological study of Hickford Park, (New Plymouth) was conducted by the Environmental Research Institute, University of Waikato, for the New Plymouth District Council. The main ecological features of the park were mapped and described and recommendations were made for the future management of the site. Hickford Park encompasses significant wetland habitat (Waipu Lagoons and oxidation ponds), sections of planted native species, an extensive duneland system, exotic plantation forest, grazed pasture, sports playing fields and the recently completed Taranaki Velodrome. The Waipu Lagoons represent a rare coastal lagoon ecosystem type in Taranaki, and host a diverse range of native wetland flora and fauna. The acclaimed coastal walkway currently extends half way through Hickford Park to St Andrews Drive. The environmental impacts of several proposed routes for the extension of the coastal walkway through the remainder of the park to Bell Block beach were assessed and recommendations made for the preferred route from an ecological perspective. In summary: • Indigenous vegetation and habitats of indigenous fauna should not be disturbed if an alternative option is available. Possible ecological impacts of the walkway development may include removal of native vegetation, impact on dune system, alteration to land contours and slope, soil disturbance and sediment input to waterways. • Construction of the coastal walkway along the originally proposed route option (1.1) would require both vegetation removal and re-contouring and would result in a decrease or degradation of natural dune habitat. • Route option 1.2 appears to be the most feasible option, as the Waitara sewer line has previously been installed in the same location and no vegetation removal would be required. • Route options 1.2, 1.3 and the proposed walkway links, provide an opportunity to enhance the public’s appreciation of the ecology within Hickford Park. • In all cases, the ecological effects of the preferred walkway route should be offset via enhancement and restoration plantings

Ecological study of Barrett Domain, New Plymouth

An ecological survey of Barrett Domain (New Plymouth) was conducted by the Environmental Research Institute, University of Waikato, for the New Plymouth District Council. The main ecological features of the domain were mapped and described, preliminary ecological impact assessments of domain upgrades were conducted, and recommendations made for the future management of the site. Barrett Domain encompasses a regionally significant wetland habitat (Barrett Lake), several hectares of remnant semi-coastal forest and areas of well-established planted native species. Wetland vegetation around Barrett Lake comprised reedland (kuta, raupo) and flaxland, and the lake provides refuge to a number of indigenous water birds. Semi-coastal forest at the site was dominated by tawa, kohekohe and pukatea, with a diverse range of understory and epiphyte species. Planted natives included a significant kauri grove, and patches of pohutukawa and puriri. Swamp forest to the west of the lake comprised mature pukatea and swamp maire, and if acquired in the land transfer, the ecological value of the domain would be greatly enhanced. Four permanent i-Tree vegetation monitoring plots and a National Wetland Monitoring plot were established at the domain and should be re-measured at 5 yearly intervals. Any ecological impacts associated with the construction of a path around the perimeter of Barrett Lake could be offset by restoration planting at the southern lake margin. Management recommendations include: • Restoration planting with appropriate native species at the southern lake margin and several other key areas within the domain. • Removing/monitoring exotic species, including the gorse and grey willow on the lake margin, and wandering Jew and climbing asparagus in the forest remnants. • Fencing (stock proofing) the swamp forest at the west of the lake once it is acquired. • Continuing with pest control and monitoring. • Obtaining new interpretive signage

Structure, composition and dynamics of Metrosideros excelsa (pōhutukawa) forest, Bay of Plenty, New Zealand

The structure, composition and dynamics of a rare forest type, Metrosideros excelsa (henceforward referred to as Metrosideros) forest, were assessed in the Bay of Plenty Region, North Island, New Zealand. Metrosideros and associated species’ shade tolerances were also investigated. Study sites extended from Waihi Beach in the west, to Opape headlands in the east of the region. Thirty five quadrats ranging from 50–400 m² in size were measured resulting in a total survey area of 14,200 m². Metrosideros forests were floristically poor in comparison to other indigenous forest types; though semi-coastal Metrosideros forest hosted a more diverse understory than coastal forest. A total of 122 indigenous species were recorded, however only a minority of these were considered common and widespread, such species included Coprosma macrocarpa, Coprosma robusta, Cyathea dealbata, Melicytus ramiflorus, Myrsine australis, Pseudopanax lessonii, Pseudopanax arboreus, Beilschmiedia tawa, Dysoxylum spectabile and Litsea calicaris. In general, forest understories comprised of a sparse shrub layer, overtopped by a sub-canopy dominated by either tree ferns in steep inland localities, Pseudopanax spp., Coprosma spp. and Melicytus ramiflorus on coastal headlands, or Coprosma spp., Myrsine, Beilschmiedia, Dysoxylum and Litsea in mature and semi-coastal forest. Metrosideros growth rates were determined in two ways; first from the diameter growth of stems in four permanent quadrats, and second from ring counts on cut stem disks. Metrosideros stems initially had high growth rates, which could exceed 4 mm year⁻¹ in the first 80 years, however diameter growth subsequently slowed down as trees developed. All Metrosideros populations had regenerated in cohorts. The derived diameter age relationship suggested that stands ranged from 20–>300 years old, with mature forest being formed within 250 years. The oldest trees measured may be >1000 years old, and represent relics of the regions original vegetation. The sequence of forest development quantified for Bay of Plenty forests shows a decline in Metrosideros stems from >2000–<400 stems ha⁻¹ over a period of c. 300 years; a result of self-thinning. This was coupled with an increase in Metrosideros basal area from <20 m² ha⁻¹ to an average of 50 m² ha⁻¹; plateauing after 70 years. Total stem density and basal area were greatest in stands between 60–300 years old. The diameter frequency distributions quantified for key species suggested that appreciable shifts in species composition were occurring. The replacement strategies among key canopy species involved establishment at different phases of forest development, and this directly reflected species’ differing shade tolerances. Shade intolerant species Metrosideros and Kunzea ericoides (which could form mixed stands) established solely following disturbance. Metrosideros forest is likely to replace itself indefinitely on the unstable coastal headlands cliffs in the region, where frequent disturbances provide suitable regeneration sites. However, in semi-coastal localities, where disturbance is less frequent, Metrosideros is succeeded by shade tolerant species. Litsea, Dysoxylum and Corynocarpus laevigatus establish in mid-successional forest, however may be somewhat reliant on canopy gaps to stimulate height growth. Conversely Beilschmiedia, the most shade tolerant species, commonly establishes in mature forest and is capable of continued regeneration; thus is likely to be a dominant component of the forest community that replaces Metrosideros forest, in the Bay of Plenty. This research contributes to the national reporting of quantitative data describing the structure and composition of New Zealand’s indigenous forests, provides the first quantitative model of forest succession in Metrosideros forest in the Bay of Plenty, and contributes to the understanding of linkages between species’ shade tolerance, regenerative strategies and successional status

Evaluation of vegetation and stream health within sites supported by the Hamilton City Council Plants for Gullies Programme

Between August 2012 and March 2013, the Environmental Research Institute, University of Waikato, conducted a survey of randomly selected Hamilton gully sites which had received plants from the Hamilton City Council’s Plants for Gullies Programme. This survey assessed recent plantings, existing gully vegetation and stream health, along with property owner awareness and engagement with the key restoration principles. The Plants for Gullies Programme has been extremely well received by the Hamilton community and gully owners. Survey participants were actively restoring their gully sites with the most common goal (c. 40%) being the establishment of native plant dominance within 10 years. Gully owners have a good understanding of restoration theory and practise; on average, plant placement in the gullies scored 15.7 out of 20 with consideration of plant environmental requirements and the concept of ecosourcing was understood by c. 76% of landowners surveyed. Also, most of the interviewed participants (c. 80%) were active in seeking guidance from other gullies, often through organised tours. Current stream health was qualitatively assessed and characterised at each of the gully sites. Results provide baseline data for future monitoring. The majority of surveyed sites (c. 50%) had sand or silt substrate and the Bankwood gully had the best features for fauna habitat (e.g. debris and areas of low flow). At the time of visit, c. 60% of surveyed streams had clear water clarity. The poorest water clarity scores were in the Waitawhiriwhiri gully. When assessed on width, length and density, the average riparian buffer score was 12.8 out of 20 while the average stream shading score was 12.7 out of 20. The average bank stability score was 13.1 out of 20, reflecting an erosion problem that many gully owners talked about. Surveyed gullies were diverse in terms of native and exotic vegetation structure and composition; native species contributed between c. 30% to 100% of surveyed trees and shrubs, whereas groundcovers were predominantly exotic. This assessment of gully sites has shown that the Plants for Gullies Programme improves native species diversity through the re-introduction of species that are not naturally regenerating. The Plants for Gullies programme is a powerful tool for engaging private landowners and making cost-effective change to Hamilton City’s native biodiversity. There is now a community of willing gully owners who will continue to restore their gullies with the support of a programme or network. It is our recommendation that the Plants for Gullies Programme is reinstated before this community loses momentum

Environmental effects of the Manganui ski field, Mt Taranaki/Egmont

During May 2012, the environmental effects of the Manganui ski field were examined. Permanent quadrats first established in 1974 to monitor vegetation changes were re-measured, vegetation mapping was conducted, modifications to ground form and drainage were identified, soil compaction was examined, and stream water from the ski field catchment was tested for nutrient enrichment. This report focusses primarily on the lower Manganui ski field, as the upper Manganui ski field consists mostly of unmodified herbfield or gravelfield, protected by a sufficient snow base over the winter months. The lower Manganui ski field has a long history of modification spanning from the early 1900s. Vegetation types mapped on the lower field included unmown tussockfield, mown tussock-herbfield, shrubland and exotics. The re-measurement of vegetation in permanent quadrats on the lower field suggests that since the last re-measurement in 1994, several exotic species have increased in cover, including Carex ovalis, Poa annua, and Agrostis capillaris (percentage cover increases of up to 46.6%, 42.0% and 20.7% respectively). Vegetation mapping and historic photographs indicate that the lower ski field sits within the elevational belt of shrubland vegetation, little of which remains due to regular mowing conducted on the field since 1947. Shrubs which have been largely excluded from the field through mowing include Brachyglottis elaeagnifolius, Hebe odora, Ozothamnus vauvilliersii, Dracophyllum filifolium, Pseudopanax colensoi, Raukaua simplex and Hebe stricta var. egmontiana. Areas of the ski field dominated by exotic vegetation were predominantly associated with historic culvert construction and rock dynamiting. Compaction by machinery was confined to the sensitive mossfield area at the base of the lower field

Vegetation dieback as a proxy for temperature within a wet pyroclastic density current: A novel experiment and observations from the 6th of August 2012 Tongariro eruption

The 6th of August 2012 eruption of Te Maari (Mt Tongariro, New Zealand) generated wet pyroclastic density currents (PDCs) which caused widespread dieback of vegetation (singed, brown foliage) in their path. An absence of significant charcoal formation suggests that PDC temperatures were mostly below 250 °C. Textural evidence for liquid water being present in the matrices during emplacement (vesicles) suggests that temperatures were b100 °C. We determined a probable minimum PDC temperature using an experiment replicating the critical temperatures required to induce foliar browning in seven species affected by the eruption. In locations where all species exhibited browned foliage (or were defoliated), temperatures were probably ≥64 °C assuming a PDC duration of 60 s. In the more distal areas, where only the most susceptible species were browned while others remained healthy and unaffected, temperatures were probably around 51–58 °C. These results have relevance to volcanic hazard mitigation and risk assessment, especially on the popular Tongariro Alpine Crossing

Restoration planting in urban environments

Since the year 2000 we have been involved in numerous restoration planting projects in urban environments. Our work has focussed mainly on sites within the city of Hamilton, but we have also been involved with projects in other New Zealand cities, such as New Plymouth and Tauranga. Our approach to restoration planting has involved a combination of science and practice. While the main aim is always to restore, reassemble or reconstruct plant communities dominated by native species, we also try to inject as much science into our projects as possible − research by management. The science underpinning is essential to understand specific site conditions, species selection, species composition, ecosystem processes and to monitor progress. Findings from our work have helped shape the best practice techniques for restoring indigenous plant communities in urban environments. Some main restoration planting principles are covered below along with two case studies from Hamilton. While we have focussed on urban settings, the principles and examples given are broadly applicable to plantings in the peri-urban and rural zones, especially riparian planting