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

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

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

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

An ecological study of Chinese privet (Ligustrum sinense Lour.) in the Waikato Region

Chinese privet (Ligustrum sinense) has naturalised across the Waikato region invading lowland native forest and wetland habitat. This shrub has the ability to form a dense canopy or subcanopy and appears to exclude other native species from establishing in the understorey. Chinese privet seedlings were found in abundance underneath privet canopy, where they grow slower than when invading a new site yet are able to succeed adult plants and continually occupy a site. Chinese privet seedlings establish readily under intact native canopy but are more prolific in disturbed high light environments. Fruit is produced in abundance and is dispersed by birds particularly beneath perch sites, which limits seed dispersal over open ground. Chinese privet seedlings appear to be palatable to stock, but rapidly out-compete and dominate regenerating native species when grazing pressure is removed. A short-lived seedbank, six months to one year viability, suggests that the removal of adult plants will quickly reduce the number of seedlings establishing. This invasive shrub is a serious weed in south-eastern USA where it is well established and would appear to have similar potential in New Zealand to form vast, dense thickets with very low floristic diversity

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

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

Assessment of vegetation condition and health at Claudelands Bush (Jubilee Bush; Te Papanui)

As the largest remnant indigenous natural area, Claudelands Bush is a key asset for Hamilton city. With a history including clearance, logging and grazing; high numbers of plant species have been lost from the bush. Some of these pressures still exist today such as drainage, invasion by adventive plant species, presence of animal pests and the small size of the bush fragment. These pressures continue to contribute to native species losses. To reduce species loss and improve vegetation condition and biodiversity, management has been taking place in the area since the 1980’s. Management included planting of native species, weeding of the bush, construction of wind breaks and boardwalks

Waiwhakareke Restoration Plantings: Establishment of Monitoring Plots 2005-06

Waiwhakareke Natural Heritage Park is being developed to reconstruct native lowland and wetland ecosystems as were once widespread in the Waikato Region. The 60ha Natural Heritage Park is located on the north-west outskirts of Hamilton City and includes a peat lake (Horseshoe Lake) which is surrounded by introduced willow trees. There is some native marginal vegetation around the lake, including rushes and sedges, and an extensive area of gently sloping pasture completes the catchment. The restoration and recreation of the native plant and animal communities is being lead by the Hamilton City Council in partnership with The University of Waikato, Wintec, Nga Mana Toopu o Kirikiriroa Limited Resource Management and Cultural Consultants and Tui 2000 (McQueen 2005; McQueen & Clarkson 2003)