Substrate modification for enhanced native forest restoration,Reefton

Restoration of postmining substrates to native forest is a standard requirement of resource consents for mine sites located within areas of native forest in New Zealand. Unweathered waste rock presents significant challenges for plant growth, and past research highlights the importance of replacing soil as part of restoration. However, replacing soil with its horizon structure intact or even obtaining sufficient soil for restoration can be a challenge in some situations. In this paper, we describe the results of two trials undertaken at the OceanaGold Ltd. open‐cast gold mine in Reefton to explore the influence of substrate conditions on the growth of native forest seedlings. We show that beech (Nothofagus) seedlings grown on A‐horizon soil grew significantly better than those grown on soil mixed with waste rock, and both grew significantly better than plants grown just on waste rock. In the second trial, we show that bark chips are not a good substitute for soil. These results confirm the importance of having the correct substrate for successful native forest restoration.     

Post-establishment assessment of host plant specificity of Arytainilla spartiophila (Hemiptera: Psyllidae), an adventive biological control agent of Scotch broom,Cytisus scoparius

Scotch broom, Cytisus scoparius (Fabaceae), is a shrub native to Europe that is invasive in the USA, New Zealand and Australia. The psyllid Arytainilla spartiophila has been purposely introduced to Australia and New Zealand as a biological control agent of C. scoparius, but is an accidental introduction to California. Lupines (Lupinus spp.) are the closest native taxon to Cytisus in North America, and are therefore considered to be at the highest risk for non-target damage. However, because no lupines are native to Australia or New Zealand, only one imported forage species was evaluated during prior host specificity testing. We conducted a laboratory nymphal transfer experiment, a field choice experiment and a field survey to assess risk to three lupine species (Lupinus albifrons, Lupinus bicolor and Lupinus formosus). In the laboratory, 20% of third-instar nymphs were able to develop to adulthood on L. formosus but not on the other lupine species, while 40% completed development on C. scoparius. In the field experiment, potted lupine and C. scoparius plants were placed beside large infested C. scoparius plants; oviposition occurred on all the potted C. scoparius plants, but on none of the lupines. In the field survey, no A. spartiophila eggs or nymphs were found on naturally occurring lupines growing adjacent to infested C. scoparius. The results indicate that A. spartiophila is not likely to damage or reproduce on lupines in the field. This study provides an example of how field studies can help clarify the host specificity of biological control agents.     

Bone-seed (

Bone-seed, Chrysanthemoides monilifera ssp. monilifera (L.), is an environmental weed of coastal vegetation communities scattered throughout New Zealand. To assess the long-term implications for native forest regeneration in sites where bone-seed is present, we selected four study sites around Wellington, New Zealand, where bone-seed was abundant. We compared seed bank composition in bone-seed-invaded sites with nearby native forest patches, and monitored bone-seed and native seedling recruitment with and without control of mature bone-seed plants. We also tested the potential effects of fire on bone-seed recruitment in these communities by heating seeds prior to germination. Bone-seed, gorse (Ulex europaeus), and native species emerged from seed bank samples taken from bone-seed-invaded sites, but only native species and (less) gorse emerged from seed bank samples taken from native forest patches. Gorse germination was strongly promoted by heat but bone-seed germination was less affected by heat. Bone-seed seedling abundance increased dramatically following canopy removal, whereas native seedling abundance decreased dramatically. This suggests that disturbance of any form is likely to favour recruitment of bone-seed (and gorse) over native species, although in the long term, native seedlings can establish beneath the canopy of mature bone-seed plants. It is not yet known if, in the absence of further disturbance, regenerating native vegetation will eventually replace bone-seed in New Zealand.     

Range reshuffling: Climate change,invasive species,and the case of Nothofagus forests in Aotearoa New Zealand

Aim

The impact of climate change on forest biodiversity and ecosystem services will be partly determined by the relative fortunes of invasive and native forest trees under future conditions. Aotearoa New Zealand has high conservation value native forests and one of the world's worst invasive tree problems. We assess the relative effects of habitat redistribution on native Nothofagus and invasive conifer (Pinaceae) species in New Zealand as a case study on the compounding impacts of climate change and tree invasions.

Location

Aotearoa New Zealand.

Methods

We use species distribution models (SDMs) to predict the current and future distribution of habitat for five native Nothofagus species and 13 invasive conifer species under two 2070 climate scenarios. We calculate habitat loss/gain for all species and examine overlap between the invasive and native species now and in future.

Results

Most species will lose habitat overall. The native species saw large changes in the distribution of habitat with extensive losses in North Island and gains mostly in South Island. Concerningly, we found that most new habitat for Nothofagus was also suitable for at least one invasive species. However, there were refugia for the native species in the wetter parts of the climate space.

Main Conclusion

If the predicted changes in habitat distribution translate to shifts in forest distribution, it would cause widespread ecological disruption. We discuss how acclimation, adaptation and biotic interactions may prevent/delay some changes. But we also highlight that the poor establishment capacity of Nothofagus, and the contrasting ability of the conifers to invade, will present persistent conservation challenges in areas of both new habitat and forest retreat. Pinaceae are problematic invaders globally, and our results highlight that control of invasions and active native forest restoration will likely be key to managing forest biodiversity under future climates.     

Inferring the introduction history of the invasive apomictic grass Cortaderia jubata using microsatellite markers

Aim Reconstructing the introduction history of exotic species is critical to understanding ecological and evolutionary processes that underlie invasive spread and to designing strategies that prevent or manage invasions. The aims of this study were to infer the introduction history of the invasive apomictic bunchgrass Cortaderia jubata and to determine if molecular data support the postulated horticultural origin of invasive populations. Location Invaded areas in the USA (California, Maui) and New Zealand; native areas in Bolivia, Ecuador and Peru. Methods We used nuclear microsatellite markers to genotype 281 plants from invaded areas in California, Maui and New Zealand, and 77 herbarium specimens from native South America, and compared the genotypic and clonal variation of C. jubata from the invaded and native ranges. Clonal diversity was determined from genotypic diversity using two analytical methods. Results Invasive C. jubata from invaded regions in California, Maui and New Zealand consisted of the same single clone that probably originated from a single introduced genotype. In contrast, 14 clones were detected in herbarium specimens from the native areas of Bolivia, Ecuador and Peru. The invasive clone matched the most common clone identified in herbarium specimens from southern Ecuador where horticultural stock is presumed to have originated. Main conclusions The lack of clonal and genotypic diversity in invasive plants, but moderately high diversity detected in native plants, indicates a significant reduction in genetic variation associated with the introduction of C. jubata outside of its native range. Based on historical accounts of the horticultural introduction of C. jubata and the results of this study, a severe founder effect probably occurred during deliberate introduction of C. jubata into cultivation. Our results are consistent with the postulated horticultural origin of invasive C. jubata and point to southern Ecuador as the geographical source of invasive populations.     

Should the flower bud weevil Anthonomus santacruzi (Coleoptera: Curculionidae) be considered for release against the invasive tree Solanum mauritianum (Solanaceae) in New Zealand?

The invasive tree Solanum mauritianum Scop. has been targeted for biological control in South Africa and New Zealand, by deploying insect agents that could constrain its excessive reproductive output. The flower-feeding weevil Anthonomus santacruzi (Curculionidae) was approved for release in South Africa in 2007 but following the loss of the original culture in quarantine, new stocks were introduced from Argentina in 2008–2009. This study was initiated to confirm that the host range of the new culture was the same as that of the previous one, but also to assess the risks associated with the weevil's release in New Zealand. Different testing procedures, including no-choice tests and multi-choice tests in different arenas, produced inconsistent and ambiguous results. During no-choice tests, oviposition and larval development to adulthood occurred on three non-target species including two native South African and one native New Zealand Solanum species. However, subsequent multi-choice tests and a risk assessment suggested that the risks of anything more than collateral damage to non-target Solanum species are low. Overall, these data do not deviate substantially from the results of the original quarantine tests which facilitated the release of A. santacruzi in South Africa in 2009. Although we argue that none of the New Zealand native and cultivated species are at risk, stronger evidence from open-field trials and chemical ecology studies may be required to convince the regulatory authorities that A. santacruzi is suitable for release in New Zealand.     

Protura in native and exotic forests in the North Island of New Zealand

Abstract

This study provides data on population and community ecology of Protura in native forests and Pinus radiata plantations in New Zealand. Abundance, age structure, sex ratios, biodiversity, and relationship with soil chemistry are discussed. Protura were significantly more abundant in pine plantations in comparison to native forests. Among native forests, Protura were most abundant under Southern beech (Nothofagus solandri). The abundance patterns may reflect the association between Protura and fungal communities in the soil. No correlation was found between soil organic matter, nitrogen, phosphorous, pH, cation exchange capacity, and the density of Protura. Protura assemblage composition was significantly related to forest type. New Zealand endemic species were associated with native forests; species with distribution outside New Zealand dominated in pine plantations. The distribution records within New Zealand were expanded for five species. The Protura fauna of New Zealand was increased to 18 species. Berberentulus capensis, Eosentomon australicum and Australentulus tillyardi are new records for New Zealand fauna.     

Assessing the risks of releasing a sap-sucking lace bug, <Emphasis Type="Italic">Gargaphia decoris</Emphasis>, against the invasive tree <Emphasis Type="Italic">Solanum mauritianum</Emphasis> in New Zealand

The South American tree Solanum mauritianum Scopoli (Solanaceae), a major environmental weed in South Africa and New Zealand, has been targeted for biological control, with releases of agents restricted to South Africa. The leaf-sucking lace bug, Gargaphia decoris Drake (Tingidae), so far the only agent released, has become established in South Africa with recent reports of severe damage at a few field sites. To evaluate the insect’s suitability for release in New Zealand, host-specificity testing was carried out in South Africa in laboratory and open-field trials, with selected cultivated and native species of Solanum from New Zealand. No-choice tests confirmed the results of earlier trials that none of the three native New Zealand Solanum species are acceptable as hosts. Although the cultivated Solanum muricatum Aiton and S. quitoense Lam. also proved unacceptable as hosts, some cultivars of S. melongena L. (eggplant) supported feeding, development and oviposition in the no-choice tests. Although eggplant was routinely accepted under laboratory no-choice conditions in this and previous studies, observations in the native and introduced range of G. decoris, open-field trials and risk assessment based on multiple measures of insect performance indicate that the insect has a host range restricted to S. mauritianum. These results strongly support the proposed release of G. decoris in New Zealand because risks to non-target native and cultivated Solanum species appear to be negligible. An application for permission to release G. decoris in New Zealand will be submitted to the regulatory authority. Handling editor: John Scott.     

Impact of an exotic vine Clematis vitalba (F. Ranunculaceae) and of control measures on plant biodiversity in indigenous forest,Taihape, New Zealand

The exotic vine, Clematis vitalba L. (F. Ranunculaceae), has been in forest reserves around Taihape in the Rangitikei Ecological Region of the central North Island, New Zealand, for about 70 years. Before this weed was abundant, Taihape forests were rich in species of indigenous vascular plants, especially woody species. Clematis vitalba and its control are contributing to a loss of forest structure and of indigenous biodiversity at the ecosystem and species levels, to a lack of recruitment of indigenous species, to an influx of other weeds and to changes in growth forms of indigenous shrubs. Species that have disappeared or become uncommon in forest with C. vitalba tend to be those that are nationally threatened or uncommon, have restricted distributions or are biogeographically significant. Current control of C. vitalba in the Taihape forest is piecemeal and long-term. It is based on mechanical and chemical methods, followed by grazing with sheep to prevent regeneration. Recommendations are made for rapid removal of C. vitalba from all untreated parts of the reserve, followed by manual control or spot- spraying, permanent removal of sheep, control of other serious weeds and implementation of a restoration programme.     

Potential risk of accidental introduction of Asian gypsy moth (Lymantria dispar) to Australasia: effects of climatic conditions and suitability of native plants

1 The potential risk of the establishment of the Asian strain of the gypsy moth (AGM) (Lymantria dispar) in New Zealand and Australia (Australasia) was assessed from a study of the insect's host range and potential distribution. In New Zealand, viable eggs of AGM have been continuously intercepted on cargo from Asia, and therefore there is a high probability of accidental introductions of AGM to Australasia. 2 We predicted potential distribution ranges of AGM based on climatic conditions. Asian gypsy moth is predicted to be able to persist in N and SE New Zealand and SE and SW Australia. 3 Using three populations of AGM and 59 species (seven families) of plant (55 from Australasia and four from elsewhere), we also conducted laboratory trials to examine the ability of AGM larvae to complete development on native plants from Australasia. Asian gypsy moth was able to complete development on 26 out of the 55 native species tested. Furthermore, larval performance on at least five species of Australian native plant was as good as on AGM's preferred host species (Quercus pubescens and Q. robur). 4 Larval performance of AGM was poor on all but one species of New Zealand native tree species (Nothofagus solandri), and therefore the risk of establishment in the indigenous forests of New Zealand is considered to be low. 5 Given the suitability of some Australian plants and the climatic suitability for the establishment of AGM, this insect should be treated as a serious quarantine threat and managed accordingly, particularly in Australia.     

Ecological Restoration of Native Forest at Aratiatia, North Island, New Zealand

Successional pathways in native forest, planted 15–33 years ago on reconstructed surfaces to restore aesthetic values destroyed by hydro‐electric dam construction at Aratiatia, central North Island, New Zealand, were compared with those on similar surfaces left unplanted. Only native species were planted. Classification identified three canopy communities and several ground layer communities with significant inter‐stratum relationships: Pittosporum tenuifolium‐Sophora tetraptera short forest with ground layers dominated by litter; P. tenuifolium‐Kunzea ericoides short forest over adventive grasses on planted sites; and adventive Cytisus scoparius shrubland over grasses on unplanted sites. Planted communities mirror young secondary forests on intact substrates in the district, but have lower density and similar or higher basal area than such forests elsewhere. Established seedlings of seven planted canopy trees, mostly early successional bird‐dispersed species, are reasonably widespread in floristically rich Pittosporum‐Sophora forest. Seedlings of only two species are widespread in floristically poor Pittosporum‐Kunzea forest, and none on unplanted sites. This first large‐scale attempt at ecological restoration in New Zealand, by mass planting of new surfaces with early successional native woody species, has created aesthetically‐pleasing stands of indigenous forest on sites which would otherwise remain in relatively stable adventive shrubland communities for the foreseeable future. Only continued monitoring will show whether further management is necessary and whether natural processes are operating at a level sufficient to ensure that artificially initiated successions will continue along more or less natural pathways.     

Invading Monotypic Stands of Phalaris arundinacea: A Test of Fire, Herbicide, and Woody and Herbaceous Native Plant Groups

Phalaris arundinacea L. is an aggressive species that can dominate wetlands by producing monotypic stands that suppress native vegetation. In this study invasion windows were created for native species in monotypic stands of P. arundinacea with either fire or herbicide. Three native species groups, herbaceous plants, herbaceous seeds, and woody shrubs, were planted into plots burned or treated with herbicide in the early spring. Fire did not create an effective invasion window for native species; there was no difference in P. arundinacea root and shoot biomass or cover between burned and control plots (p≥ 0.998). Herbicide treatment created an invasion window for native species by reducing P. arundinacea root and shoot biomass for two growing seasons, but that invasion window was fast closing by the end of the second growing season because P. arundinacea shoot biomass had nearly reached the shoot biomass levels in the control plots (p= 0.053). Transplant mortality, frost, and animal herbivory prevented the herbaceous species and woody seedlings from becoming fully established in the plots treated with herbicide during the first year of the experiment. Transplanted monocots had a greater survival than dicots. By the second growing season the herbaceous group had the greatest mean areal cover (5%), compared to the woody seedlings (3%) and seed group (0%). Long‐term monitoring of the plots will determine whether the herbaceous transplants will compete effectively with P. arundinacea and whether the woody species will survive, shade the P. arundinacea, and accelerate forest succession.     

Genetic structure of an introduced paper wasp,Polistes chinensis antennalis (Hymenoptera,Vespidae) in New Zealand

Several eusocial wasps are prominent invaders to remote islands. The paper wasp Polistes chinensis antennalis is native to East Asia, was introduced to New Zealand in 1979 and has expanded its distribution there. This provides an excellent opportunity to examine the impacts of an initial bottleneck and subsequent expansion on genetic structure. We analysed and compared the genetic population structures of the native (Japan and South Korea) and invasive New Zealand populations. Although 94% of individuals had shared haplotypes detected across both populations, the remaining 6% had private haplotypes identified in only one of the three countries. The genetic variation at microsatellite loci was lower in New Zealand than in native countries, and the genetic structure in New Zealand was clearly distinct from that in its native range. Higher frequencies of diploid‐male‐ and triploid‐female‐producing colonies were detected in New Zealand than in the native countries, showing the reduction in genetic variation via a genetic bottleneck. At least two independent introductions were suggested, and the putative source regions for New Zealand were assigned as Kanto (central island) and Kyushu (south island) in Japan. Serial founder events following the initial introduction were also indicated. The estimated dispersal distance between mother and daughter in New Zealand was twice that in Japan. Thus, the introduction history of P. chinensis antennalis in New Zealand is probably the result of at least two independent introductions, passing through a bottleneck during introduction, followed by population expansion from the point of introduction.     

Effects of forest fragment management on vegetation condition and maintenance of canopy composition in a New Zealand pastoral landscape

Residual forest fragments in areas dominated by pastoral agriculture can have high value for biodiversity conservation but are still subject to ongoing degradation as (i) processes initiated by fragmentation continue to operate, for example, changes in canopy replacement probabilities; and (ii) deleterious processes impinge upon them from the surrounding matrix, for example, browsing and trampling by vagrant livestock. Responses by management to slow or reverse these processes require evaluation. Stock (mainly cattle and sheep) exclusion by fencing and mammal pest (mainly Trichosurus vulpecula (brushtail possum)) control are currently used as management tools to maintain or improve the vegetation condition of fragments in New Zealand. We examined the effectiveness of these tools by sampling vegetation composition, forest structure and regeneration of woody species in 41 old‐growth fragments dominated by Beilschmiedia tawa, selected to populate a factorial design that included four different fencing classes (unfenced, fenced 2–10, 10–20 and >20 years ago), with and without sustained mammal pest control. Fencing for more than 10 years led to higher abundances of native ground ferns and shrubs, and lower abundances and numbers of mostly adventive herbaceous ground cover species. In contrast, lianes were less abundant with mammal pest control, whereas herbs were more abundant. Fencing led to a high‐density pulse of seedlings and saplings of woody species within 10 years that then thinned. Mammal pest control allowed increases in abundance of some species palatable to T. vulpecula, and increased the ratio of canopy to subcanopy seedlings in the regeneration pulse caused by fencing. Neither treatment, however, led to the restoration of indigenous species richness to reference forest levels, nor allowed densities of juveniles of shade‐tolerant canopy species to establish to levels commensurate with replacement of existing canopy trees. Most woody seedlings that established following fencing were of short‐lived subcanopy species. These management actions will therefore slow but not reverse the long‐term degradation of these forest fragments, which will eventually differ substantially from continuous forest under current management regimes. Additional measures such as replanting may be necessary not only to ensure replacement of some current species but also to restore lost species.     

Host specificity of the ragwort flea beetle Longitarsus jacobaeae (Waterhouse) (Coleoptera:Chrysomelidae)

Abstract

The ragwort flea beetle, Longitarsus jacobaeae, was tested for host specificity against representative species of native New Zealand Senecio. Adult feeding and oviposition tests were carried out under quarantine with and without a choice of host plants. Larval development was assessed using potted plants. It was concluded that L. jacobaeae is highly specific to Senecio jacobaea and that it is extremely unlikely to be damaging to native New Zealand Senecio species.     

Morphological plasticity and ecophysiological response of ground ivy (Glechoma hederacea,Lamiaceae) in contrasting natural habitats within its native range

Abstract

Some species intrinsically have a high invasiveness capacity, shown by high phenotypic plasticity and rapid growth, enabling a wide distribution across their native habitats and successful invasion in the introduced range. For such species, information from native habitats is critically important. An example is Glechoma hederacea, native to Eurasia but introduced and widespread in the USA. Our main objective was to investigate variation in traits of native G. hederacea populations across contrasting habitats: open, forest edge and understory. Vegetation was sampled and the ecophysiological and morphological traits were measured with accompanying environmental parameters. Results showed that in native habitats environmental conditions cover wide gradients of light and soil moisture. Plants had the highest cover in nutrient-rich, shaded habitats, representing the optimal habitat, indicating shade tolerance of G. hederacea. Plants from forest understory exhibited strong similarities in investigated traits to plants from the forest edge, even though this was a drier, sunnier habitat. Plants from open, sunny habitats experienced stress as indicated by the quantum efficiency of PSII and significantly higher sexual reproduction. Results show that G. hederacea is moderately tolerant simultaneously to shade and drought, a characteristic that has been reported for numerous invasive species, while at the same time it shares some characteristics with weedy plants.     

Sampling indigenous ground‐living beetles in a stand of non‐native tree privet (Ligustrum lucidum) in New Zealand raises new management questions

Small urban forest reserves in New Zealand have been shown to have value in conserving indigenous beetle diversity. However there is little information available on the ability of non‐native vegetation areas such as tree privet to support indigenous beetle assemblages. To investigate this for one site, ground‐living beetles were collected using pitfall traps over a year at a small urban forest of the invasive tree Ligustrum lucidum (tree privet) in Auckland, New Zealand. A total of 815 beetles were found, from 20 families and 42 relative taxonomic units. Using monthly data, there was no correlation between soil moisture and diversity index (P = 0.805) or species richness (P = 0.375). These results raise the question of whether urban patches of non‐native tree privet may have potential as reservoirs of beetle diversity, if only until they are replaced with native vegetation.     

The abundance,distribution and structural characteristics of tree‐holes in Nothofagus forest,New Zealand

Tree‐holes provide an important microhabitat that is used for feeding, roosting and breeding by numerous species around the world. Yet despite their ecological importance for many of New Zealand's endangered species, few studies have investigated the abundance or distribution of tree‐holes in native forests. We used complementary ground and climbed tree surveys to determine the abundance, distribution and characteristics of tree‐holes in undisturbed Nothofagus forest in the Lewis Pass, New Zealand. We found that hole‐bearing trees were surprisingly abundant compared with many other studies, including Australian Eucalyptus species and American beech. In fact, we estimated as many as 3906 tree‐holes per hectare, of which 963 holes per hectare were potentially large enough to provide roost sites for hole‐nesting bats in New Zealand, while only eight holes per hectare were potentially suitable for specialist hole‐nesting birds. This was of great interest as primary cavity‐excavating animals are absent from New Zealand forests, compared with North America and Australia. Moreover, tree‐hole formation in New Zealand is likely to be dominated by abiotic processes, such as branch breakage from windstorms and snow damage. As has been found in many other studies, tree‐holes were not uniformly distributed throughout the forest. Tree‐holes were significantly more abundant on the least abundant tree species, Nothofagus fusca, than on either N. menziesii or N. solandri. In addition to tree species, tree size was also an important factor influencing the structural characteristics of tree‐holes and their abundance in this forest. Moreover, these trends were not fully evident without climbed tree surveys. Our results revealed that ground‐based surveys consistently underestimated the number of tree‐holes present on Nothofagus trees, and illustrate the importance of using climbed inspections where possible in tree‐hole surveys. We compare our results with other studies overseas and discuss how these are linked to the biotic and abiotic processes involved in tree‐hole formation. We consider the potential implications of our findings for New Zealand's hole‐dwelling fauna and how stand dynamics and past and future forest management practices will influence the structural characteristics of tree‐holes and their abundance in remnant forest throughout New Zealand.