The species is a small tree endemic New Caledonia. It is fairly well spread in the central portion of the island and is found in some protected areas. The species has an extent of occurrence (EOO) of 5,320 km² with a range extending across New Caledonia. The species has experienced historical population decline largely due to climate change which has since been exacerbated by pressures on the landscape from nickel mining and fire. All of these factors still threaten the species, but perhaps the main threat being fire as it has been shown that this reduces regeneration potential for Nothofagus species and can force conversion of forest to woodland or maquis. Nothofagus balansae has one of the widest ranges of any Nothofagus species in New Caledonia, despite its fractured localities, it is not severely fragmented and there is no immediate specific threat. This species has been globally assessed as Least Concern.

Aire géographique

This species is endemic to New Caledonia and is fairly well spread in the central portion of the island with a collective population in the south. It has occurrences in Boulinda, Paéoua, Mé Aiu, Négropo, Creek Pernod, Ouinnée and Pic du Pin. It is no longer considered to occur in on the Tchingou massif (L. Barrabé pers. comm. 2018). The species is recorded from 200 m above sea level to elevations that exceed 1,000 m asl with an estimated extent of occurrence (EOO) of 5,320 km².

Population

Subpopulations are largely made up of older individuals of a similar age. The disjunct distribution, on both a local and a regional scale, suggests that all species of Nothofagus were either previously more widespread or that isolated subpopulations have been mobile following climatic shifts (Veblen et al. 1996). Recent pollen analysis suggests a much more widespread distribution of the genus; which suggests that climate change has been a long contributing factor to the decreasing population of the species. Considering its current range is fairly broad across the country, it could be assumed that it was once fairly common. Due to climate change alongside anthropogenic threats such as conversion of land use is likely to have exacerbated population decline of the species.

Habitat

This is a small tree species, growing to 10 to 15 m in height (Endemia 2017). It thrives in wet dense forest on ultramafic soils (Veblen et al. 1996). Within a Nothofagus forest, there is often little overlap between species stands. The under canopy of trees typically occur 5–10 m lower often containing species that comprise the upper canopy in mixed rain forest. This layer commonly includes several genera in the families Podocarpaceae, Araliaceae, Cunoniaceae, Lauraceae, Myrtacee, Sapindaceae, Euphorbiaceae and Apocynaceae along with many other species (Veblen et al. 1996). In a recent paper by Amir et al. (2006), it was discovered that arbsucular mychorrhiza colonised many endemic species associated with metal-enriched ultramafic soils, Nothofagus balansae being one. This relationship, alongside the species' association with an ectomychorrhizal fungus is important in the adaption and success of the species on ultramafic soils. This may be relevant to ecological restoration of abandoned mining sites. Nothofagus balansae is likely to be common species within this habitat, which could suggest that restoring damaged environments by mining sites could 'jump start' the ecological cycle.

The species requires large scale disturbance to the forest canopy to be able to successfully regenerate (J. Read pers. comm. 2018). There are seedlings at some sites of Nothofagus forests, showing regeneration is possible even when conditions may not be most ideal.

Menaces

There is little literature available regarding threats to Nothofagus species. The species is potentially threatened by the major threats of climate change and nickel mining which are having a devastating effect on much of New Caledonia’s flora. The degree to which this impacts the species specifically is not known.

The region is experiencing rapid economic growth, rising population and the constant mining for nickel is causing many species to become fragmented and extinct in parts of the island. Many Nothofagus species habituate to lower montane forests (600–800 m) which suggests that these species are unlikely to be able to shift in response to a changing climate due to poor wind dispersal and the need for specialised soil conditions. Nickel mining is a threat to the species near Kopéto, Koniambo, Kiel, Négropo, Ménazi where mining sites are present and causing risk to the species (L. Barrabé pers. comm. 2018).
The species may also be affected by the increase of fire. There are concerns of a reduced regeneration potential for Nothofagus forests within New Caledonia especially following fires where rainforest is often replaced by xerophytic woodland or maquis. As there is growing incidence of fire on the island this could become a greater threat to the species as its native habitat is lost. Nothofagus has not been known to invade these new habitats. At present, it is unknown the extent to which this change impacts N. balansae (Veblen et al. 1996).

Conservation

BGCI Plant Search (2017) states, there are currently no ex situ collections of the species; it is recommended these are made. The species is found in three protected areas: Rivière Bleue, Pic du Pin and Montagne des Sources.

Bibliographie

Endemia.nc 2016. Faune et Flore de Nouvelle-Calédonie.

Munzinger J., Morat Ph., Jaffré T., Gâteblé G., Pillon Y., Tronchet F., Veillon J.-M., & M. Chalopin 2016. FLORICAL: Checklist of the vascular indigenous flora of New Caledonia. vers. 22.IV.2016.

Experts

Assessor(s): Baldwin, H.

Reviewer(s): Tanguy, V., Read, J., Barrabé, L.

Contributor(s): Rivers, M., Barstow, M.