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Melanodendron integrifolium 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Asterales Compositae

Scientific Name: Melanodendron integrifolium (Roxb.) DC.
Common Name(s):
English Black Cabbage Tree
Synonym(s):
Solidago integrifolia Roxb.
Taxonomic Notes: Molecular phylogenetic studies (Eastwood, Gibby and Cronk 2002) show a close relationship between Melanodendron and Commidendrum consistent with the hypothesis that the two genera originated from a common ancestor via a single dispersal event. This close relationship is further supported by shared wood anatomy (Carlquist 2001). The first major ecological shift in the evolution of arborescent Asteraceae on St Helena would have occurred in the divergence of Commdendrum (dryer) and Melanodendrom (wetter) from a common ancestor. Melanodendron integrifolium is confined to the wettest and coolest habitats on St Helena, and has characteristic features of a species adapted to wet sub-tropical conditions (Carlquist 2001).

Assessment Information [top]

Red List Category & Criteria: Vulnerable D2 ver 3.1
Year Published: 2016
Date Assessed: 2015-06-13
Assessor(s): Lambdon, P.W. & Ellick, S.
Reviewer(s): Clubbe, C.P.
Contributor(s): Cairns-Wicks, R.
Justification:
Black Cabbage Tree (Melanodendron integrifolium DC.) is considered to be Vulnerable under criterion D2 because the area of occupancy is less than 20 km2, there are no more than two to three locations and it faces a plausible threat of becoming Critically Endangered in a short period of time. The main concerns arise from disease outbreaks, declining levels of natural recruitment and competition from invasive non-native weeds.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Black Cabbage Tree is endemic to the island of St Helena, South Atlantic Ocean, where it is restricted to cloud forest fragments along the Central Ridge.

The extent of occurrence (EOO), based on the area of a minimum convex polygon around known localities, is 7.75 km2. The area of occupancy (AOO), based on a 2 km × 2 km grid, is 8 km2. Following IUCN Red List Guidelines, the EOO is therefore increased to 8 km2 to match the AOO.

This distinctive tree is a species of St Helena’s cloud forest zone, although it now survives in only three remnant fragments of suitable habitat along the island’s Central Ridge, between 695 and 820 m altitude. The majority of the population lies along Diana’s Peak Ridge where it is widely dispersed through almost continuous native vegetation from Cabbage Tree Road in the north to Wash House in the south, a distance of approximately 1.5 km. There is also a moderately healthy colony on the cliffs of High Peak, though this occupies a much smaller area of native vegetation (the span is only 250 m). The final, tiny subpopulation lies at The Depot, at the western end of the upland zone. In total, the area of habitat occupied by the species is approximately 0.169 km2.
Countries occurrence:
Native:
Saint Helena, Ascension and Tristan da Cunha (Saint Helena (main island))
Additional data:
Estimated area of occupancy (AOO) - km2:8Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:8
Continuing decline in extent of occurrence (EOO):NoExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:2Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):695
Upper elevation limit (metres):820
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:

Following a census conducted in 2013-14, the world population of the species, including all individuals found in apparently wild situations, was estimated to be 2,262 mature plants (approximate 95% confidence range: 2,187 – 2,358). A large majority was confined to Diana’s Peak Ridge. High Peak held 11.2%, and only five plants remained at The Depot.

This total appears to indicate a substantial increase since the last reasonably comprehensive survey was conducted in the 1990s (Smith and Williams1996). At that time, approximately 780 individuals were found in the Diana’s Peak area. However, it is difficult to compare the two surveys directly. Many of the steeper slopes and valleys are difficult to view or access, and the 2013-14 counts benefited from high-resolution digital photographs to cover areas where only distant views were possible. Also, Black Cabbage Tree flowers whilst still reasonably small, and there may have been some discrepancy over what was considered to be a “mature” individual. In 2013-14, the definition was taken to include all plants which were potentially large enough to produce inflorescences, many of which were well below the typical maximum size for the species.

The 1990s census coincided with a period of progressive conservation. Based on its findings, a management plan was produced and an ambitious programme of tree planting undertaken. This resulted in approximately 1,800 Black Cabbage seedlings being established in wild situations. The provenance of today’s trees is no longer clear, so it is difficult to assess the success of these efforts, or to identify which of the current cohort of trees is truly “wild” (i.e., arising via natural colonization processes from parents already growing in natural habitats). However, it is likely that a reasonable proportion of the seedlings survived to maturity and that the current population estimate has therefore been somewhat boosted as a result. Concentrations of planted Black Cabbage Tree are likely to be present on the eastern side of Diana’s Peak summit, in Warren’s Valley and on the eastern slopes of Cuckold’s Point (the most southerly of the three peaks along Diana’s Peak Ridge).

In addition to the advances, there also appear to have been substantial declines in some areas. “Cabbage Tree Road”, the main route of entry to Diana’s Peak, was once famed as a forested walkway, but today only two ageing Black Cabbage specimens lie along the route. Similarly, by comparing data from Smith and Williams (1996) with the recent survey, there is a strong indication of heavy losses from large expanses of the steep western escarpment of Diana’s Peak Ridge and the ridge above Wash House.

Further afield, the subpopulation at High Peak may be holding its own despite encroachment from New Zealand Flax (Phormium tenax J.R.Forst. & G.Forst.). However, Cairns-Wicks (2003) reported that the species also occurred at “a few locations across the ridges and outside of [what was then Diana’s Peak] National Park”. There do not appear to be any survivors from these scattered relicts except for the few plants at The Depot, where numbers have certainly dwindled over recent years.

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:2262Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:3Continuing decline in subpopulations:No
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:

St Helena’s “cabbage trees” comprise eight Asteraceae species belonging to endemic genera, which have probably evolved a large size and/or woody habit in isolation on the island to fill niches left vacant as a result of the scarcity of other arborescent plants. Black Cabbage is still the most widespread of these and remains a community co-dominant in the cloud forest zone, where it plays an important ecological role.

Much of the cloud forest is blanketed by Tree Fern thicket (dominated by Dicksonia arborescens L’Hér). This is a dense habitat with relatively little understorey vegetation due to the presence of a thick, acidic litter layer. Black Cabbage Trees are dispersed through the Tree Ferns and compete for space effectively, the broad, dark canopies shading a moderately large area. Such gaps create pockets of diversity where a rich understorey can flourish. A number of endemic bryophytes and vascular plants are dependent on the conditions created, as are several extremely rare invertebrates, such as the Spiky Yellow Woodlouse (Pseudolaureola atlantica Vandel) which has become a flagship for St Helena conservation. These species benefit from the exposed mineral soils which provide space for seedlings and gametophytes to establish, and the high humidity trapped under the dense canopy. Particularly where older trees are present, there may be important resources of dead wood for xylophagous insects, and rough, slightly spongy bark which allows epiphytes to establish. The epiphytic flora thrives in particular abundance along the very crest of the Central Ridge where interception of mist from incoming cloud reaches a maximum.

Black Cabbage Tree typically flowers in spectacular displays between October and early December, providing copious quantities of pollen for numerous small insects. The fruits mature in abundance a few weeks later, but in wet years a proportion of the annual crop may rot on the branch before release. The light achenes are dispersed on the wind. The efficiency of this process probably depends on local topography, but amongst dense Tree Ferns most of the crop appears to settle within 10 m or so of the parent. Seedlings germinate wherever suitable bare ground is available. Since this is usually a scarce resource, very few recruits survive to adulthood. They also root abundantly on Tree Fern trunks and often become well-established, although most of the saplings die unless the trunk falls within a few years, when a few may gain further purchase into the soil. Adult trees are resilient against the strong winds which buffet much of the cloud forest zone during the winter months, although this inevitably takes its toll and the typical lifespan is probably modest.

Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: The wood was formerly used for timber but has not been exploited for at least a century.

Threats [top]

Major Threat(s):

Initial heavy losses arose as a result of the rapid deforestation of the uplands following establishment of a permanent British colony on St Helena in 1659. The clearances were primarily to make way for pasture, but as one of the larger trees on the island with a trunk of reasonable girth, Black Cabbage would have been particularly sought after as a source of firewood and timber. A further wave of destruction followed in the late 19th and early 20th Centuries, when large tracts of unproductive land on the steep slopes of the Central Ridge were converted to plantations of New Zealand Flax. The flax industry collapsed in the 1960s, but vast areas are still blanketed by the original monocultures. The net result of these waves of destruction has been to confine the remaining cloud forest to isolated fragments with little opportunity for expansion, limited genetic exchange and heavy constraints on normal ecological processes such as cycles of succession and recolonization.

Although the remaining cloud forest fragments are now protected and relatively stable in extent, they continue to suffer from deterioration. Present day threats derive mainly from interactions with non-native species. There is certainly some direct competition from invasive trees such as Bilberry (Solanum mauritianum Scop.) and Quinine (Cinchona officinalis L.), which are already abundant on Diana’s Peak Ridge. The Flax continues to encroach, particularly at High Peak. Sprawling growths of Small Fuchsia (Fuchsia coccinea Curt.) also form dense tangles which can creep over living branches, although these are more of a threat amongst Tree Fern thicket. Probably a more serious threat is posed by ground cover herbs which compete for open soil, and thus remove the already limiting micro-habitats suitable for germination. The native cloud forest community is largely lacking in low-growing, patch-forming species, so the impact of encroachment by pasture grasses such as Cow Grass (Paspalum scrobiculatum L.), Running Sedge (Kyllinga brevifolia Rottb.) and the invasive Feather Moss (Pseudoscleropodium purum) into freshly-created clearings is probably much underestimated.

A final threat comes from disease. In both 2008 and 2014, a sudden wave of die-back killed significant numbers of large, mature trees in the Diana’s Peak area. The cause of this die-back is unknown and there were few external symptoms. In both instances, the effect was manifested during warm, dry conditions following a period of sustained, heavy rain. Infection by an oomycete of the genus Phytophthora (de Bary) is one possibility, but thus far no pathological tests have been possible. There are sufficient trees remaining that the impact of the disease was not particularly noticeable by the following year. Despite this, continued waves of loss at a similar frequency (removing many prime, mature specimens from the population), coupled with a decline in the rate of recruitment, could lead to a long-term crash.

The threats to the species affect not just the population of Black Cabbage Tree in isolation, but also the associated habitat which it creates. The latter is particularly sensitive because a cluster of trees growing in close proximity is normally necessary to provide sufficient space to sustain an open understorey. There is relatively little evidence to assess the change in distribution of this habitat, but there is a reasonable likelihood that it has already suffered severe declines. Today there are very few pockets remaining on Diana’s Peak Ridge. A few concentrations remain around High Peak, but only a single aggregation of approximately 25 trees at ‘The Dell’ can be called a fragment of ‘woodland’. As a consequence, community associates such as Large Kidney Fern (Dryopteris cognata (C.Presl) Kuntze), Dwarf Tongue-Fern (Grammitis ebenina (Maxon) Tardieu), the Spiky Yellow Woodlouse and Rainbow Leaf-Beetle (Vernonia wollastoniana White) are severely threatened with extinction.

The scarcity of Black Cabbage woodland is largely due to the fact that most of the surviving trees are now individually dispersed, often densely crowded within a matrix of Tree Fern thicket or invasive vegetation. This may partly reflect patterns of tree planting in the 1990s. However, even where clusters exist, they may fail to suppress the established, denser understorey. Creation of open spaces below the trees is certainly not a simple case of succession, since Tree Ferns will tolerate the heavy canopy shade and even encroach under it. Research is much needed to understand the dynamics of cloud forest habitat cycles, how the clearings form and what maintains them.

Conservation Actions [top]

Conservation Actions:

Black Cabbage Tree is confined to the Central Peaks National Park (designated in 2013 following expansion of the former Diana’s Peak National Park and development of a wider National Conservation Area network on St Helena). It will be protected under the National Conservation Area development plans, which are expected to be in place in 2016. The species will also be protected under the new Environmental Protection Ordinance, presently in the final stages of drafting and expected to be issued in 2016.

St Helena Government employ a small ‘Habitats Team’ to conduct ecological restoration and removal of invasive species from key sites in the Diana’s Peak area. Their efforts have undoubtedly been vital in maintaining the current, reasonably healthy population of Black Cabbage Tree. The species has experienced substantial declines on the steep western slopes which are largely inaccessible to management, and has only held its own on the eastern flanks which have been subject to a steady programme of invasive control. However, St Helena has little economic wealth and the team operates on a minimal budget which is regularly threatened with cuts. Staff turn-over is high, resulting in a regular drain on knowledge and experience. The continuation of the programme is therefore subject to a degree of uncertainty.

Black Cabbage Tree is one of the most difficult of the upland endemic species to grow in cultivation. Seed viability is moderate and germination can be achieved reasonably easily, but the rate of growth is very slow, and the plants require a high humidity environment which usually confines them to a shade house with misting facilities. This places a heavy constraint on space. As a consequence, production rates have generally been very low. Even in the 1990s, success was mainly achieved by re-locating wild seedlings, rather than by multiplication in the nursery. However, since 2012, renewed efforts have seen an increase in production at St Helena Government’s Endemic Plant Nursery. Saplings are usually planted out after one year, but remain small and vulnerable to desiccation for some time. Meanwhile, seed has been banked on-island and samples have also been sent to Kew's Millennium Seed Bank in the UK.

In the future, targeted work is needed to recreate Black Cabbage Tree woodland, in addition to the basic programme of more scattered tree planting. The St Helena National Trust are currently engaged on a fixed-term project to restore suitable conditions to one part of High Peak (funded by the Darwin Plus initiative). It is hoped that this will expand and link existing pockets to create a more sustainable complex of fragments, with benefit for several associated species.


Citation: Lambdon, P.W. & Ellick, S. 2016. Melanodendron integrifolium. The IUCN Red List of Threatened Species 2016: e.T37594A67371221. . Downloaded on 21 November 2017.
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