Evaluation of the Hamilton City Council plants for Gullies programme

This evaluation found that the Hamilton City Council Plants for Gullies programme is successfully facilitating the restoration and enhancement of Hamilton City gullies by private gully owners. The mean number of native species in surveyed gullies was 2.1 in non-restored sites and 18.4 in restored sites. While the mean number of invasive species was 4.1 in non-restored sites to 2.6 in restored sites. This quantitative measure is a valuable indication of the ecosystem gains for Hamilton City. Hamilton gully owners are very satisfied with the Plants for Gullies programme; the mean satisfaction rating was 8.9 out of 10. These residents dedicate significant time and energy to restoring their gully sections; the mean time contribution of survey participants was 10.3 hours per month. Gully owners were found to be utilising knowledge acquired through participation in the programme to add valuable diversity to their gully ecosystems. This was repeatedly demonstrated by programme participants not only reintroducing the native plants supplied by the programme but also adding large quantities of privately-sourced plants. This investigation found that the Plants for Gullies and Gully Restoration programmes are effective in communicating key ecological restoration concepts. This was reflected by gully owner prioritisation of eco-sourcing, biodiversity and weed control as considerations in their restoration projects. The Gully Restoration Guide was found to be the most valuable component of the programme’s educational tools. However, it is recommended that this resource is updated to support the many gully owners who require information for advanced stages of ecological restoration. In summary, the Plants for Gullies programme is successfully delivering gully restoration assistance and advice to gully owners, which is resulting in significant improvements to Hamilton City’s gully systems. The programme is valued by all who are involved and could be recommended to other New Zealand cities as an effective model for environmental restoration and community engagement

Seed rain and soil seed banks limit native regeneration within urban forest restoration plantings in Hamilton City, New Zealand

Restoration of native forest vegetation in urban environments may be limited due to isolation from native seed sources and to the prevalence of exotic plant species. To investigate urban seed availability we recorded the composition of seed rain, soil seed banks and vegetation at native forest restoration plantings up to 36 years old in Hamilton City and compared these with naturally regenerating forest within the city and in a nearby rural native forest remnant. Seed rain, soil seed banks (fern spores inclusive) and understorey vegetation in urban forest were found to have higher exotic species richness and lower native species density and richness than rural forest. Both understorey vegetation and soil seed banks of urban sites >20 years old had lower exotic species richness than younger (10–20 years) sites, indicating a developmental threshold that provided some resistance to exotic species establishment. However, the prevalence of exotic species in urban seed rain will allow reinvasion through edge habitat and following disturbance to canopy vegetation. Persistent soil seed banks from both urban and rural sites were dominated by exotic herbaceous species and native fern species, while few other native forest species were found to persist for >1 year in the seed bank. Enrichment planting will be required for those native species with limited dispersal or short-lived seeds, thus improving native seed availability in urban forests as more planted species mature reproductively. Further research into species seed traits and seedling establishment is needed to refine effective management strategies for successful restoration of urban native forests

Effect of Coriaria arborea on seed banks during primary succession on Mt Tarawera, New Zealand

An experiment was conducted over two years to investigate the effect of Coriaria arborea, a native nitrogen-fixing shrub, on soil seed banks at sites representing a post-volcanic successional sequence on Mt Tarawera, New Zealand. The sites ranged from bare volcanic ash and lapilli substrate, through low-growing pre-Coriaria vegetation, to dense stands of Coriaria scrub. Soils (to a depth of 50 mm) under recently established Coriaria and older stands had more seedlings (1096 and 1585 seedlings 0.4 m-2, respectively) and species (37 and 45 species 0.4 m-2, respectively) emerge than where there was no Coriaria (243-320 seedlings 0.4 m-2, 14-25 species 0.4 m-2) and were the only soils with Coriaria seedlings. In total, 3488 seedlings representing 63 taxa were recorded. Seeds were still germinating after 24 months but rates declined markedly in the second year. For example, Coriaria reached a germination peak at 8 weeks but continued to germinate sporadically over the 2-year period. Tree species present in young forest within 0.5 km of the sites were absent. Establishment of Coriaria greatly accelerated an underlying trend of gradually increasing abundance and diversity of seeds in the soil with vegetation age. Adventive, wind-dispersed, and annual species were over-represented in the seed banks compared with the regional evergreen forest-dominated flora. These proportions are expected to decline as succession to forest gradually occurs

Pattern and process of vegetation change (succession) in recent volcanic landscapes of New Zealand and Hawaii

Volcanic activity (including lava flows, debris flows and tephra eruptions) is a regular feature of many landscapes of the North Island of New Zealand and the Hawaiian archipelago. Over the last 35 years, we have been using a combination of the chronosequence and direct monitoring methodologies (Clarkson 1998; Walker et al. 2010) to research the pattern and process of vegetation change (succession) in these landscapes. The following account summarizes pattern and process from our main study sites: Whakaari (White Island), Rangitoto Island, Mt Tarawera, Mt Ngauruhoe, Mt Ruapehu, and Mt Taranaki in New Zealand and Mauna Loa in Hawaii. The main focus of this account is forest development following significant eruptions

Ecological restoration in Hamilton City, North Island, New Zealand

Hamilton City (New Zealand) has less than 20 hectares of high-quality, indigenous species dominated ecosystems, and only 1.6% of the original indigenous vegetation remains within the ecological district. A gradual recognition of the magnitude of landscape transformation has gathered momentum to the stage that there is now a concerted public and private effort to retrofit the City by restoring and reconstructing indigenous ecosystems. The initial focus was on rehabilitating existing key sites, but has shifted to restoring parts of the distinctive gully landform that occupies some 750 ha or 8% of the City. A new initiative at Waiwhakareke (Horseshoe Lake) will involve reconstruction from scratch of a range of ecosystems characteristic of the ecological district over an area of 60 ha. This address will examine a vision for ecological restoration in Hamilton City within the context of policy, education, and community dimensions that have triggered a shift from traditional parks and gardens management to ecosystem management

Bringing nature back into cities: urban land environments, indigenous cover and urban restoration

1. The restoration of urban ecosystems is an increasingly important strategy to maintain and enhance indigenous biodiversity as well as reconnecting people to the environment. High levels of endemism, the sensitivity of species that have evolved without humans, and the invasion of exotic species have all contributed to severe depletion of indigenous biodiversity in New Zealand. In this work, we analysed national patterns of urban biodiversity in New Zealand and the contribution that urban restoration can make to maximising and enhancing indigenous biodiversity. 2. We analysed data from two national databases in relation to the 20 largest New Zealand cities. We quantified existing indigenous biodiversity within cities, both within the core built up matrix and in centroid buffer zones of 5, 10 and 20 km around this urban centre. We analysed the type and frequency of land environments underlying cities as indicators of the range of native ecosystems that are (or can potentially be) represented within the broader environmental profile of New Zealand. We identified acutely threatened land environments that are represented within urban and periurban areas and the potential role of cities in enhancing biodiversity from these land environments. 3. New Zealand cities are highly variable in both landform and level of indigenous resource. Thirteen of 20 major land environments in New Zealand are represented in cities, and nearly three-quarters of all acutely threatened land environments are represented within 20 km of city cores nationally. Indigenous land cover is low within urban cores, with less than 2% on average remaining, and fragmentation is high. However, indigenous cover increases to more than 10% on average in the periurban zone, and the size of indigenous remnants also increases. The number of remaining indigenous landcover types also increases from only 5 types within the urban centre, to 14 types within 20 km of the inner urban cores. 4. In New Zealand, ecosystem restoration alone is not enough to prevent biodiversity loss from urban environments, with remnant indigenous cover in the urban core too small (and currently too degraded) to support biodiversity long-term. For some cities, indigenous cover in the periurban zone is also extremely low. This has significant ramifications for the threatened lowland and coastal environments that are most commonly represented in cities. Reconstruction of ecosystems is required to achieve a target of 10% indigenous cover in cities: the addition of land to land banks for this purpose is crucial. Future planning that protects indigenous remnants within the periurban zone is critical to the survival of many species within urban areas, mitigating the homogenisation and depletion of indigenous flora and fauna typical of urbanisation. A national urban biodiversity plan would help city councils address biodiversity issues beyond a local and regional focus, while encouraging predominantly local solutions to restoration challenges, based on the highly variable land environments, ecosystems and patch connectivity present within different urban areas

Indigenous vegetation types of Hamilton Ecological District

The following descriptions of indigenous vegetation types and lists of the most characteristic species have been compiled for the major landform units of the Hamilton Ecological District, which lies within the Waikato Ecological Region (McEwen 1987). The boundaries of the Hamilton Ecological District correspond approximately to those of the Hamilton basin, with the addition of parts of hills and foothills at the margins of the basin. The vegetation descriptions and species lists are based on knowledge of the flora of vegetation remnants in the ecological district, historical records (e.g., Gudex 1954), and extrapolation of data from other North Island sites with similar environmental profiles

The use of chronosequences in studies of ecological succession and soil development

1. Chronosequences and associated space-for-time substitutions are an important and often necessary tool for studying temporal dynamics of plant communities and soil development across multiple time-scales. However, they are often used inappropriately, leading to false conclusions about ecological patterns and processes, which has prompted recent strong criticism of the approach. Here, we evaluate when chronosequences may or may not be appropriate for studying community and ecosystem development. 2. Chronosequences are appropriate to study plant succession at decadal to millennial time-scales when there is evidence that sites of different ages are following the same trajectory. They can also be reliably used to study aspects of soil development that occur between temporally linked sites over time-scales of centuries to millennia, sometimes independently of their application to shorter-term plant and soil biological communities. 3. Some characteristics of changing plant and soil biological communities (e.g. species richness, plant cover, vegetation structure, soil organic matter accumulation) are more likely to be related in a predictable and temporally linear manner than are other characteristics (e.g. species composition and abundance) and are therefore more reliably studied using a chronosequence approach. 4. Chronosequences are most appropriate for studying communities that are following convergent successional trajectories and have low biodiversity, rapid species turnover and low frequency and severity of disturbance. Chronosequences are least suitable for studying successional trajectories that are divergent, species-rich, highly disturbed or arrested in time because then there are often major difficulties in determining temporal linkages between stages. 5. Synthesis. We conclude that, when successional trajectories exceed the life span of investigators and the experimental and observational studies that they perform, temporal change can be successfully explored through the judicious use of chronosequences

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