David A. Norton

Threatened and uncommon plants of New Zealand

Abstract A reappraisal of the conservation status of the indigenous New Zealand vascular plant flora is presented. The list comprises 792 taxa (34% of New Zealands total indigenous vascular flora) in the following categories: Extinct 4 taxa, Acutely Threatened 122 taxa (comprising 47 taxa Nationally Critical, 54 Nationally Endangered, 21 Nationally Vulnerable), Chronically Threatened 96 taxa (comprising Serious Decline 26 taxa, Gradual Decline 70 taxa), At Risk 499 taxa (comprising Sparse 126 taxa, Range Restricted 373 taxa), Non‐resident Native 26 taxa (comprising Vagrant 16 taxa, Colonist 10 taxa), and Data Deficient 45 taxa. A further 208 plants are listed as Taxonomically Indeterminate, being those which might warrant further conservation attention once their taxonomic status is clarified. A further 31 named taxa and 18 rated as Taxonomically Indeterminate, and previously considered to be threatened and/or uncommon, are removed from this updated listing. A concordance of plant names is provided. The lists presented use a new threat classification system developed by the New Zealand Department of Conservation for sole use within this country. This paper represents the first time the entire known indigenous vascular flora has been assessed from a conservation perspective since the mid 1970s. A brief analysis of the patterns of rarity exhibited by the taxa listed is presented.

Mistletoes as parasites: Host specificity and speciation.

Recent research on parasite evolution has highlighted the importance of host specialization in speciation, either through host-switching or cospeciation. Many parasites show common patterns of host specificity, with higher host specificity where host abundance is high and reliable, phylogenetically conservative host specificity, and formation of races on or in different host species. Recent advances in our understanding of host specificity and speciation patterns in a variety of animal parasites provides valuable insights into the evolutionary biology of mistletoes.

Ecological restoration at Mainland Islands in New Zealand

Abstract While important advances have been made in recovering threatened species and restoring damaged habitats on offshore islands, effective conservation management is also required on the main (North and South) islands if representative elements of New Zealands remaining biodiversity are to be protected. The recent initiation of Mainland Island projects constitutes an important step in that ecosystem-focused restoration goals are being pursued at mainland sites. The intensity and scope of pest control undertaken at Mainland Islands is greater than has normally been the case previously, as has been monitoring of results and conservation outcomes. Preliminary results suggest that declines in monitored species have been arrested and ecological processes re-vitalised. In addition to restoring values at individual sites Mainland Islands may be important places where our capacity to manage ecosystems more generally may be developed. Advances in our understanding of ecological processes and of responses to management using sound scientific procedures as part of operational programmes could lead to improved predictions to underpin management decisions. Refinements to management techniques and the development of appropriate skills, as well as enhancing public support and involvement could also be expected to have major benefits for conservation management more widely.

Threatened and uncommon plants of New Zealand (2008 revision)

Abstract A reappraisal of the conservation status of the indigenous New Zealand vascular plant flora is presented using the 2008 version of the threat classification system developed for the New Zealand Department of Conservation. The list comprises 897 taxa (38% of New Zealands total indigenous vascular flora) in the following categories: Extinct—6 taxa, Threatened—180 taxa (comprising 91 Nationally Critical taxa, 45 Nationally Endangered, and 44 Nationally Vulnerable), At Risk—651 taxa (comprising 83 Declining, 6 Recovering, 20 Relict, and 542 Naturally Uncommon taxa), 25 taxa listed as either Vagrant (12) or Coloniser (13), and 35 as Data Deficient. A further 171 plants are listed as taxonom ically indeterminate, being those which might warrant further conservation attention once their taxonomic status is clarified. Forty‐four recognised taxa and 26 plants rated as taxonomically indeterminate, and previously considered to be threatened and/or uncommon, are removed from this updated listing. A brief analysis of the patterns of rarity exhibited by the listed taxa is presented. Overall, the conservation status of the New Zealand indigenous vascular plant flora is worsening, with 7.6% of this flora now regarded as threatened with extinction. A concordance of plants names from the 2004 listing is provided.

Dendroecological studies in New Zealand 1. An evaluation of tree age estimates based on increment cores

Abstract Tree-ring counts from increment cores are widely used in ecological studies for determining tree ages. In New Zealand many canopy trees are slow-growing and long-lived, and have extremely narrow rings. Single rings or groups of rings may be absent on some radii. Such narrow and absent rings cause difficulties in ring counting and necessitate careful sample preparation. The errors associated with age estimates derived from cores which do not reach the chronological centre of the tree (partial cores) are discussed. Four partial core lengths and three methods of estimation were used on cross-sections of known age from Agathis australis, Libocedrus bidwillu, Nothofagus solandri, and Prumnopitys taxifolia. It is concluded that mean errors may be less than ± 10% where the core length represents 90% of the geometric radius (half the measured diameter) increase with shorter cores. However, much greater errors may apply to individual estimates, up to ± 78% in one case. Moreover, the direction of the error...

Climate and Growth of Pinus Sylvestris at Its Upper Altitudinal Limit in Scotland: Evidence from Tree Growth-Rings

The influence of climatic factors on the growth of Pinus sylvestris was evaluated by comparing annual ring-widths from seven sites along an altitudinal gradient in Scotland with monthly climatic data. Temperature was found to be more important than rainfall in influencing growth. Both late-winter (January-February) and summer (July-August) temperatures were significantly and positively correlated with ring-width. Winter browing or frost drought is a possible cause of the winter temperature correlation (...)

Species Invasions and the Limits to Restoration: Learning from the New Zealand Experience

Species invasions impose key biotic thresholds limiting the success of ecological restoration projects. These thresholds may be difficult to reverse and will have long-term consequences for restoration because of invasion legacies such as extinctions; because most invasive species cannot be eliminated given current technology and resources; and because even when controlled to low levels, invasive species continue to exert substantial pressure on native biodiversity. Restoration outcomes in the face of biological invasions are likely to be novel and will require long-term resource commitment, as any letup in invasive species management will result in the loss of the conservation gains achieved.

The ecology of Dacrydium cupressinum: A review

Abstract Literature relating to the ecology of rimu (Dacrydium cupressinum) is reviewed with respect to the reproductive biology, vegetative morphology and growth, and population dynamics of this species.

The diet of introduced brushtail possums Trichosurus vulpecula in a low-diversity New Zealand Nothofagus forest and possible implications for conservation management

Abstract We evaluate the diet of introduced brushtail possums Trichosurus vulpecula in a relatively low-diversity New Zealand Nothofagus forest. Although possums only invaded this area 30–40 years ago, densities (0·5–1·0 ha −1 ) are similar to those recorded for other Nothofagus forests. Thirty-three food types are eaten by possums, but the four most important contribute 68·4% of annual diet. Preference indices show that foliage consumption is non-random, with some species being highly favoured, particularly short-lived ‘seral’ tree species. Although possums rely heavily on foliage, the type of food consumed is strongly influenced by seasonal shifts in availability of key food types. Invertebrates and fruit are seasonally important in the diet and are probably taken opportunistically to supplement the staple foliage diet. Possum damage is less obvious in Nothofagus forests than in floristically more diverse forests as palatable species form only a small proportion of the biomass. However, these species make a major contribution to overall forest diversity and, through selective browsing, possums reduce diversity and accentuate the strong bias towards unpalatable biomass. These changes have significant implications for forest birds, as there is considerable overlap between possum and bird diet. If possum browsing continues, it is likely to restrict food supply for some birds. Most concern in possum control has gone into more diverse mixed-species forests, but even in low-diversity Nothofagus forests with few possums, these animals can have a disproportionately large impact on forest composition. Possum control in these forests is therefore likely to have considerable long-term benefits for ecosystem health.

A multivariate approach to assessing threat and for priority setting in threatened species conservation

Abstract The use of multivariate techniques for assessing the threats facing species and for determining priority groupings in threatened species conservation is evaluated. Scores based on different criteria provide species profiles that allow species to be placed in multidimensional space. Species that group together are likely to be threatened for similar reasons. Multivariate techniques identify the main factors threatening species and highlight problems with linear ranking schemes, especially where species can have the same total score for very different reasons. Multi-variate techniques also allow identification of redundant criteria used in deriving species scores, and are free of problems associated with interdependence between criteria. Multivariate techniques provide a powerful additional tool for determining management priorities and for assessing threat and can also be used for assessing changes in species status with time and for modelling potential management actions for improving the security of a species. However, in using these techniques it is essential to make a clear distinction between threat and priority.