Colin D. Meurk

Planning and design of ecological networks in urban areas

Urban ecological networks are defined differently in ecology, urban planning and landscape ecology, but they all have linearity and linkage in common. Early urban representations evolved from the constraints of deep ecological structure in the landscape to built elements that must work around natural linear obstacles—rivers, coastlines, dunes, cliffs, hills and valley swamps. Village commons were linked by roads. The Industrial Revolution led to accelerating urban growth, where the role of open space focussed on public health and transport. The Renaissance, Baroque and Picturesque movements accentuated networks in wooded parks, boulevards and sweeping riverine vistas. These provided a new aesthetic and sense of grandeur in the urban centres of European empires and later their colonies. Grafted onto this visual connectivity has been an awakened ecological understanding of spatial dynamics. The emergent notion of ecological corridor functionality provided support for green linear features, although initially this was based on untested theory. The idea of organisms moving along green highways seemed logical, but only recently has unequivocal empirical evidence emerged that demonstrates this functionality. Nevertheless, the main role of corridors may be to provide habitat rather than to act as connectors of nodal habitats. Most organisms can utilise stepping stones, and these may accommodate desired meta-populations while deterring pest movement. Swale drains and treatment wetlands provide riparian services and serve as biodiversity corridors. However, to most people the obvious function is visual—providing green fingers through what would otherwise be urban grey. The health benefits of these are have been demonstrated to be psychological as much as biophysical.

A landscape ecological framework for indigenous regeneration in rural New Zealand-Aotearoa

Abstract Practical steps using landscape ecological concepts to better integrate nature and culture within New Zealand’s agricultural landscape are proposed. In New Zealand, nature conservation is typically seen as distinct from agri-business, and the two goals are pursued in different places — with nature having steadily retreated from public view and experience. As a result, the New Zealand agricultural landscape is largely exotic, with little to indicate the rich biogeographical history of the land. In contrast, a productive cultural landscape in which indigenous species (and hence biodiversity) are both present and regenerating is projected. Ecological integrity is defined both in terms of life processes and indigenous content. Several examples are presented of spontaneous regeneration of indigenous species within the context of familiar landscape elements such as hedgerows, roadsides, shelterbelts, woodlots, gardens, and riparian margins. In combination, these elements have the potential to create a new landscape, culturally familiar, non-threatening and productive, yet also achieving biodiversity goals. Creation of such transitional landscapes can reinforce a sense of identity with the unique characteristics of New Zealand-Aotearoa, and in the longer term this will transform the way landscapes are perceived, valued and utilised.

The re-emergence of indigenous forest in an urban environment, Christchurch, New Zealand

Abstract Christchurch, the second largest city in New Zealand is a planned city on a coastal plain on the east coast of the South Island. The birth of the city and the subsequent century of development was characterised by colonial values and tree and garden planting with familiar European species along with those from Australia, North America, and eventually all other continents. The image of an “English garden city” with classical parks of oaks and willow-lined rivers became the accepted norm and the way in which the city has been promoted to potential tourists. Gardening is one of the top two recreational activities and exotic species greatly outnumber native species in the flora and in gardens. This has had serious consequences for the highly fragmented and degraded indigenous vegetation and its co-adapted wildlife. A few hardy indigenous species continued to regenerate through this period, but since the 1970s, there has been a progressive change of attitude and interest in reclaiming the natural heritage of the city, manifest in widespread private and public planting of indigenous species and active habitat restoration. In this article we examine the indigenous and exotic shrub and tree components of the Christchurch flora as planted street trees, in domestic gardens, and in parks. We also present data on shrub and tree regeneration in parks and domestic gardens in the city. Indications are that the more sensitive, less intrusive management of urban environments, combined with the greater density of indigenous seed sources, has allowed regeneration of a wide range of indigenous species across a broad spectrum of habitats – from neglected gardens to pavement cracks to exotic plantations. This is despite the competition from the prodigious seed banks and density of exotic trees, shrubs, and ground covers and albeit minimal impacts of introduced browsing and seed eating mammals. If the present trends continue through appropriate management and facilitation, these tentative signs of native forest regeneration should eventually proliferate into a sustainable mixed origin urban forest that resurrects and preserves the natural character of the region.

Evolution of Stilbocarpa, a megaherb from New Zealand's sub‐antarctic islands

Abstract Challenges to the traditional circumscription of Apiaceae and Araliaceae are emerging as a result of phylogenetic analysis of DNA sequences. Traditionally classified as Araliaceae, Stilbocarpa emerges with Schizeilema and Azorella, both members of the Apiaceae. In our analyses of nuclear ITS sequences, these three genera comprise a distinct Southern Hemisphere lineage. The humid climate, cool equable temperatures, locally abundant nutrients, and absence of herbivores are ecological features of the sub‐antarctic islands that may have contributed to the evolution of the unusual megaherb, Stilbocarpa, from these diminutive apiaceous ancestors.

URban Biotopes of Aotearoa New Zealand (URBANZ) (I): composition and diversity of temperate urban lawns in Christchurch

Christchurch urban lawns are dominated by non-native grasses and forbs. However, we document considerable plant diversity; the total number of species encountered in our 327 sampled lawns was 127, although 80 species occurred in <2% of lawns. Seven distinct lawn communities were identified by Two-Way INdicator SPecies ANalysis using occurrence of 47 species that occurred in > 2% of lawns. Our ability to explain variation in species composition was surprisingly good and indicates intensity of lawn maintenance such as frequency of mowing, irrigation, fertiliser, and herbicide use and whether clippings are removed or not plays the major role. Species richness significantly declines with an increase in total area of contiguous lawn, leaf litter cover, the presence of grass clippings, and on loamy soil. Hence, park lawns with coarser management had lower species richness than residential lawns. Native species were more prevalent in well tended residential lawns, where more frequent mowing and removal of clippings or litter build-up diminishes shoot competition or shading. There is tremendous potential for more native species in New Zealand lawns which would contribute substantially to the conservation of endangered lowland herbaceous flora.

Secondary woody vegetation patterns in New Zealand’s South Island dryland zone

Abstract Can New Zealand’s indigenous dryland ecosystems be rehabilitated by facilitating inherent successional tendencies to enhance development of indigenous-dominated and often woody communities in the long term? Here, we describe the geographic distribution of woody communities of New Zealand’s South Island drylands to generate hypotheses about successional trajectories to future vegetation states. Presences and absences of woody species in 3880 vegetation plots collated from past surveys were used to predict species potential distributions across drylands. Separate models and spatial predictions were built for each of four classes of woody richness, which were used as surrogates for successional stages. Woody species richness increased significantly from grassland to shrubland and from shrubland to forest cover, and trends in species traits also suggest richness class was related with successional stage. Indigenous woody species outnumbered exotic species in all richness classes. Assuming richness classes represent temporal progressions, our results suggest relatively homogeneous early-successional woody associations succeed to a divergent array of woody associations in different environments. Growth forms of species in our predicted associations suggest transitions from grassland to tall, tree-rich forests in northern and coastal drylands, and to liane-rich open or lightcanopied shrubland, woodland, or low forest in more severe inland environments. These putative communities are novel in species composition but physiognomically broadly similar to pre-settlement analogues. Especially in severe inland environments, unassisted transitions from grassland to indigenousdominated late-successional woody communities may depend on the exclusion of tall exotic trees, Scotch broom, and gorse in early succession.

Agricultural intensification: Whither indigenous biodiversity?

Abstract A new wave of agricultural intensification in New Zealand is causing increasing pressure on natural resources. Moller et al. (2008) suggest that the agricultural intensification is inevitable, that negative environmental impacts have only been demonstrated for aquatic system s, and that a new paradigm based on integrating indigenous biodiversity and agriculture offers the best way forward. We question all these assertions. Recent agricultural intensification is increasingly driven by international economic opportunities for agricorporates to maximise returns. Intensification over the last two decades is causing loss of habitat for indigenous species and homoge‐nisation of landscapes at scales unprecedented since deforestation by colonial farmers. Regional and district councils appear ill prepared for a formative role requiring sustainable land and resource use, while current patterns of local consumption and offshore resource subsidisation for agribusinesses are probably unsustainable. Irrespective of the drivers of agricultural intensification, residual indigenous biodiversity in agricultural landscapes in New Zealand is on an extinction pathway. The challenge for agro‐industry is to demonstrate that it can, in the absence of regulation, use natural resources and at the same time facilitate persistence of indigenous biodiversity components at scales that contribute to national biodiversity goals.

Competitive abilities of three indigenous New Zealand plant species in relation to the introduced plant Hieracium pilosella

Summary The competitive abilities of three montane indigenous New Zealand plant species ( Acaena buchananii , Festuca novae-zelandiae , and Raoulia australis ) when growing with the locally invasive, introduced Hieracium pilosella were compared in an outdoor pot experiment. Competitive ability was divided into the competitive effect, or the ability to deplete resources, and the competitive response, or the ability to tolerate low resource levels. The plants were grown in pots with or without Hieracium , in shade or full sunlight, and with high or low soil fertility. The competitive response rankings showed consistent hierarchies in the different treatments with Festuca being less suppressed than Acaena and Raoulia . Festuca performed especially well in low soil fertility and in shaded treatments, while the other two species were strongly suppressed by Hieracium even in those conditions. However, all three species did relatively better (less badly) in the low fertility and shaded treatments than in the more resource-rich treatments when interacting with Hieracium . The effect on Hieracium biomass of the indigenous species was generally small and the rankings of competitive effect showed no agreement between the species in the different environmental treatments. We suggest that competitive rankings based on the competitive response component is likely to be a more sensitive measure of competitive ability for these indigenous, slow-growing plants. The results also indicates that these two components of a plants competitive ability were negatively correlated and thus reflect trade-offs in dealing with competitive situations. Finally, in competition with Hieracium , low-growing indigenous species are likely to perform best when nutrients and light are maintained at low levels. Die Konkurrenzfahigkeit dreier auf Neuseeland heimischer Pflanzenarten ( Acaena buchananii, Festuca novae-zelandiae und Raoulia australis ) gegenuber der invasiven und eingefuhrten Art Hieracium pilosella wurde in einem Freilandtopfexperiment verglichen. Konkurrenzfahigkeit wurde dabei unterteilt in Konkurrenzwirkung, d. h. die Fahigkeit, Ressourcen zu verringern, und Konkurrenzantwort, d. h. die Fahigkeit, niedrige Ressourcenniveaus zu ertragen. Die Pflanzen wurden in Topfen mit bzw. ohne Hieracium , im Schatten bzw. in vollem Sonnenlicht, und mit hoher bzw. geringer Bodenfertilitat gehalten. Die Konkurrenzantworten in allen Behandlungen folgten durchweg den gleichen Rangstufen, wobei Festuca weniger eingeschrankt wurde als Acaena und Raoulia . Festuca gedieh besonders gut bei geringer Bodenfertilitat und in den Schattenbehandlungen, wahrend die beiden anderen Arten selbst unter diesen Bedingungen stark eingeschrankt wurden. Alle drei Arten gediehen jedoch unter Hieracium -Einfluss, relativ gesehen, besser (weniger schlecht) bei geringer Fertilitat und Schattenbehandlung als in den Behandlungen mit hoherem Ressourcenangebot. Der Einfluss der einheimischen Arten auf Hieracium war allgemein gering und die Konkurrenzwirkung jeder Art folgte in den verschiedenen Behandlungen verschiedenen Rangstufen. Wir meinen, dass Konkurrenzvergleiche, die sich auf die Konkurrenzantwortkomponente stutzen, ein genaueres Mass fur die Konkurrenzfahigkeit dieser einheimischen, langsam wachsenden Pflanzen sein durften. Die Ergebnisse deuten auch darauf hin, dass zwischen diesen beiden Komponenten der Konkurrenzfahigkeit einer Pflanze ein negativer Zusammenhang besteht, und sie daher einander ausschliessende Strategien darstellen, um mit Konkurrenzsituationen fertigzuwerden. In Konkurrenz mit Hieracium gedeihen niedrig wachsende einheimische Arten eher, wenn Nahrstoffe und Licht auf niedrigen Niveaus gehalten werden.

Climate, fire, farming and the recent vegetation history of subantarctic Campbell Island

Campbell Island is a small, uninhabited peat-covered island lying in the cool southern ocean 600 km south of the New Zealand mainland. Dracophyllum scrub is the main cover from sea level to 200 m, above which tussock grassland, macrophyllous forbs and tundra dominate. Seven peat profiles from sea level to the tundra zone provide an elevational transect for pollen and charcoal records spanning the last 500 years. Scrub density was relatively low between 200 and 400 cal yrs BP, possibly due to Little Ice Age cooling, but had recovered by the time Europeans discovered the island in AD 1810. Burning and grazing during a brief farming episode (AD 1895–1931) severely reduced scrub and palatable grasses and forbs. Vegetation recovery is now well advanced following cessation of farming and the later elimination of all feral grazing animals, cats and rats. Climates were cool in the southwest Pacific during the farming period, and since AD 1970 the island has warmed by c . 0·5°C. However, there has been no upwards movement of the scrubline despite vigorous regeneration of scrub at lower altitudes. The islands cloudy, highly oceanic climate appears to offset increasing summer warmth, and scrubline is likely to rise only if clearer and less windy, as well as warmer, summers eventuate.

Invasion of the Subantarctic Auckland Islands, New Zealand, by the Asterad Tree Olearia lyallii and its Interaction with a Resident Myrtaceous Tree Metrosideros umbellata

Natural and semi-natural plant invasions are central topics in biogeography and management of reserves. They also provide evidence on general ecological processes related to community structure and stability. This study ex- amines an invasion by Olearia lyallii in the subantarctic Auckland Islands, south of New Zealand. There are two principal forest-forming tree species on the Auckland Islands: Metrosideros umbellata (rata), which has occupied the islands for at least 9000 years, and Olearia lyallii (Olearia), which probably established early in the nineteenth century. Olearia is spreading in the Port Ross area and it has been suggested should be controlled because it may threaten the rata forest. The structure, composition, dynamics and establishment of these forests were studied in an attempt to predict the long-term effects of Olearia on these islands and to resolve the management dilemma. Results show that ecologically the two species are clearly segregated. Rata dominates and regenerates in sheltered places on dense peats with relatively high concentrations of magnesium and calcium. Olearia, in contrast, encroaches on coastal tall-tussock grassland, megaherbfield, shrubland and dwarf mixed-forest communities, growing on peat soils with high total soluble salts, Na, P and K concentrations derived from the marine aerosol and perhaps ions accumu-