Tuatara: Volume 9, Issue 3, January 1962
The New Zealand Lowland Podocarp Forest. Is it Subtropical?
The New Zealand Lowland Podocarp Forest. Is it Subtropical?
Visiting botanists from the north temperate zone are usually greatly impressed and not a little puzzled by the apparently tropical form of many of the plants in our lowland, podocarp-dicotylous forests.* Most New Zealand botanists regard these forests as subtropical in nature and origin following the original suggestion by Cockayne (1926), but visitors and authors of books on plant geography usually find this designation difficult to accept. Thus Polunin (1960) says ‘The rain forest in New Zealand is almost entirely temperate in nature, in spite of the prevalence of large tree ferns’ and Chapman (1958) feels that it is time that Cockayne's subtropical concept ‘ceased to colour the New Zealand botanist's interpretation of lowland forests’ and further states ‘It would seem then that Cockayne's and Schimper's view of the New Zealand lowland forest (except kauri forest) as subtropical cannot be substantiated.’ The basic objection seems to be that New Zealand is not thought to have a subtropical climate, nor to be situated within the subtropical zone. With the exception of the Auckland peninsula the first point is probably valid, the second point also, although it should be noted that unlike the tropical zone the subtropical zone is not geographically defined. Most people, however, would agree that New Zealand is rather too far from the equator to be included in such a zone, defined or not. A further objection, based on floristics, is put forward by Chapman (1958) who points out that ‘the lianes and epiphytes (of the New Zealand lowland forests), regarded as a subtropical feature, belong mostly to families other than those found as lianes and epiphytes in the tropics.’ Before attributing too much weight to these objections based on latitude, climate and floristics, we should remember that world vegetation types are primarily defined in terms of their structure and the life forms of the plants composing them. Admittedly a particular vegetation type usually develops in relation to a particular climate, but it should never be assumed that the two must always occur together. Vegetation change usually lags behind climatic change, so it is not unusual to find * The term ‘lowland forest’ in the remainder of the text refers to this type alone and does not include lowland Nothofagus forest. page 99 vegetation that cannot be related to the present climate of its area. Edaphic and historical factors may also prevent or delay the full development of vegetation in relation to climate.
There is also no necessary correlation between latitude and vegetation. Because of the temperature decrease from the equator to the poles world climates, and hence vegetation types, tend to follow a latitudinal sequence. The correlation between vegetation and the broad, geographically defined, latitudinal zones — tropical, temperate and polar — is reasonably good, but even here there may be some transgression of boundaries, e.g. where tropical rain forest extends a little beyond the Tropic of Capricorn in South America, south-east Asia and Australia (Richards, 1952).
With regard to the matter of floristics it should be emphasised that two areas of vegetation can be accepted as belonging to the same type without there being any floristic relationship between them. Thus what is known as Mediterranean scrub vegetation has developed independently in five widely separated areas in the world in relation to a particular climate, but the plants of any one area are largely unrelated to those of the other four. Similar cases of parallelism in plant form occur in the desert areas. Water-storing plants in the deserts of North America and South Africa, for example, are remarkably similar in appearance, but are in fact quite unrelated taxonomically. Plants of this form in North America belong to the Cactaceae and in South Africa mostly to the Euphorbiaceae. More pertinent to Chapman's argument are the tropical rain forests themselves. Tropical rain forest occurs in three widely separated areas: in south and central America; in south-east Asia and adjacent Pacific areas; and in central Africa. In his book on the tropical rain forest Richards says in reference to these areas, ‘In each of these formations almost all the species and many of the genera and families are peculiar and not shared with the other two.’ So the questionable contention that the epiphytes and climbers of New Zealand's lowland forests are largely unrelated to similar forms in the tropics would appear to have no bearing on the problem of whether or not the forests in question should be termed subtropical.
Chapman's second argument is also based on floristics. He questions Cockayne's belief that the affinities of the New Zealand lowland forest are with Malaya and suggests that the relationships are more with such islands as Samoa, Tonga, Fiji and New Caledonia. This may be so, but as these islands and Malaya both support tropical forest the question of the status of the New Zealand lowland forest is not affected.
Floristic relationships may lend support to the idea that two similar stands of vegetation can be classified as the same type, but the absence of such affinities cannot be taken as opposing such an idea.
From the foregoing it would seem that, ideally, the names of world vegetation types should be based on structure and life form and not on latitude, climate or floristics. However, it is not easy to devise page 100 names in this way and as names based on climate and latitude in particular are firmly entrenched, it might be easier to retain them, with the proviso that they should not be applied so rigidly that they conflict with the facts of structure and life form.
I think the second part of this paper will show quite clearly, that in terms of structure and life form the New Zealand lowland forest has a great deal in common with tropical rain forest in general, and floristically much in common with the adjacent tropics in particular. If a relationship with tropical rain forest is accepted, we must then decide whether the local forest should be placed in a world category next to tropical forest or next-but-one. Authors who have called the New Zealand forests temperate or warm-temperate have mostly recognised an intermediate category which they have termed subtropical. Schimper (1903) recognised these three types with the subtropical type rather vaguely defined as ‘impoverished tropical rain forest’. He states further, ‘It is difficult to draw the line between these forests and the much more peculiar temperate rain forests.’ He placed all the New Zealand forests under the latter heading.
More recently Dansereau (1957) has recognised the same types and again the differences are difficult to appreciate. Under subtropical forests Dansereau states ‘The fall in temperature reduces the number of flowering species’ and gives as an example of the type the forests of Hawaii. However, oceanic islands in general tend to be low in species in proportion to their areas, so isolation rather than temperature may be the explanation in this case. Under temperate rain forest Dansereau states that vascular epiphytes are few, but in New Zealand lowland forest, which he includes here, vascular epiphytes are quite abundant. The example given is northern New Zealand kauri (Agathis) forest, but the photograph illustrating the type is of Nothofagus forest.
In another recent plant geography text (Polunin 1960) the three forest types again appear. On page 350 Polunin mentions tropical, subtropical and warm-temperate rain forests, but I cannot find any further reference to the subtropical type elsewhere in his book.
In developing the schemes outlined above I think the authors have been led astray by their failure to distinguish between the New Zealand lowland forests (Agathis-dicotylous and podocarp-dicotylous) and the Nothofagus forests, which in general replace the latter at higher elevations and on poorer sites in the lowlands. In my view the Nothofagus forests are more akin to the temperate deciduous forests of the northern hemisphere than to the lowland forests in New Zealand. The fact that, in some places, there may be a wide transition zone where the forests intermingle, is no argument against separating them. Even the markedly different broadleaf-deciduous and coniferous forests in the northern hemisphere exhibit such transitions. Richards (1952) when referring page 101 to the forests of New South Wales states, 'The contrast in flora and physiognomy between the subtropical rain forest and the adjacent formations — Sclerophyll forest dominated by species of Eucalyptus and subantarctic rain forest dominated by Nothofagus — is everywhere extremely sharp.'
In a later edition of Schimper's work, van Faber (1935) followed Cockayne in differentiating between the two forest types, terming the lowland forests subtropical and the Nothofagus forests temperate.
Dansereau has also revised his scheme recently (Dansereau 1958), but it is still not clear whether or not he accepts two forest types for New Zealand. In this version only tropical and temperate rain forests are recognised. The examples given for temperate rain forest are New Zealand Nothofagus forest and the laurel forests of the Canary Islands.
It certainly seems that, on a world scale, an intermediate category between the New Zealand lowland forest and tropical rain forest cannot be maintained. The view that the New Zealand lowland forest comes into a category adjacent to that of tropical rain forest is supported by a comparison of the former with the montane tropical, or subtropical, forests of New Guinea. Robbins (1961), who has studied forests in both New Zealand and New Guinea, describes the mixed podocarp-broadleaf forest in montane New Guinea and observes ‘It is in such forest of the inland mountain regions that affinities with the New Zealand rain forests are so striking.’ Robbins also notes that there are many more species in this New Guinea forest than in its New Zealand counterpart, and that in most cases the genera are not known in New Zealand. He provides a list of the genera that are shared with New Zealand, and of these one is a moss, eight are ferns, three are gymnosperms and twenty-five angiosperms. These floristic affinities lend support, but are not necessary to the belief that these mixed montane forests in New Guinea belong to the same vegetation type as the lowland forests of New Zealand.
Nothofagus forests also occur in the montane areas of New Guinea and according to Robbins ‘beech forests exist side by side, as in New Zealand, with a mixed broadleaf-podocarp forest with usually a sharp boundary between the two’. On the basis of fossil pollen evidence, Couper (1960) has shown that Nothofagus and the podocarps are fairly recent immigrants into New Guinea from the south. They established themselves in New Guinea during the Pliocene cooling that led to the Pleistocene ice ages.
If it is granted that the New Zealand lowland forests come into a type next to that of tropical rain forest, it does not necessarily follow that they should be termed subtropical. Warm temperate rain forest might be considered more appropriate by many people, although personally I favour the term subtropical, as I feel that it best expresses the fairly close relationship with tropical rain forest. Richards also uses the term subtropical in this context and, referring page 102 to the subtropical forests of New South Wales, he says ‘It is evident that on the whole the resemblances between this subtropical forest and a typical equatorial rain forest are much more striking than the differences.’
As there is often a gradual transition from subtropical to tropical rain forest, the former is not easy to define. In general subtropical rain forest appears to differ from tropical rain forest in the following respects — fewer species; tendency towards local dominance of tree species (although this also occurs in some tropical rain forests according to Richards); an admixture of species of a more temperate nature (in New Zealand these are gymnosperms — podocarps or Agathis); smaller leaf size on the average; a greater abundance of tree ferns and bryophytes; denser undergrowth; a deeper humus layer in the soil; a greater accumulation of rotting logs due to the slower decay rate with lower temperatures; fewer tree species exhibiting buttressing and cauliflory; and sometimes a greater profusion of epiphytes.
Chapman feels that there might be a case for regarding the Agathis dominated forests in New Zealand as subtropical, but not the podocarp-dicotylous forests. These forest types can be classified as distinct within New Zealand, but I don't think they can be assigned to different vegetation types on a world scale.
It is interesting to note that both Cockayne (1921) and Robbins (1958) believe that the dicotylous element in the New Zealand subtropical forest is tending to replace the podocarp element at the present time. Robbins refers to ‘the general decline of the podocarp element in New Zealand mixed forests’ and ‘the trend towards a replacement of podocarp forest by broadleaf forests at present evident in the New Zealand vegetation pattern’. If this is so then presumably these New Zealand forests are tending to become less different from tropical rain forest in this respect.
Elsewhere in the world subtropical rain forest occurs, or formerly occurred, in southern Queensland and New South Wales, in limited montane and coastal areas in eastern South Africa, in south-east Brazil, in a limited area in south Chile, in southern Florida, south Japan, south and south-east China and possibly in the Canary Islands. In the last case the forest is known as laurel forest and occurs in moist gullies on the mountain sides. Schimper describes it as ‘a sclerophyllous forest transformed into a temperate rain forest, or a stage intermediate between them with a closer approximation to the sclerophyllous forest’. Christ (1885) mentions ‘a poor development of lianes and the absence of true epiphytes’ and also ‘Several of the woody species were partly identical with or partly related to Mediterranean sclerophyllous plants.’ It seems doubtful whether such forest can be regarded as being in the same category as subtropical forest, or even Nothofagus forest as Dansereau has suggested.page 103
Subtropical and tropical rain forests are fairly restricted in their distribution at the present time, but fossil evidence indicates that they were very much more widespread in the early Tertiary prior to the ice-age. At this time world climates were much more uniform than now and were, in general, warm and moist. Under these conditions tropical and subtropical rain forests extended from the equator to about 50° north and south to include such places as the south of England and Oregon. General cooling and progressive desiccation in some areas in the later Tertiary, culminating in the ice-ages, caused the extinction of most of the rain forest outside the geographical tropics. The surviving areas, listed earlier, of subtropical rain forest in temperate regions, are mostly near the tropics, but in several places in the southern hemisphere they extend to middle latitudes. The great preponderance of ocean in the southern hemisphere may have sufficiently reduced the severity of the climatic minimum in the middle latitudes to allow these forests to persist. In New Zealand, during the last glaciation, it has been suggested that forests were largely, if not entirely, restricted to areas north of about 39° (Harris pers. comm.). With the improved climate since that time forests have re-established themselves throughout the country.
Before giving some account of the structure and life forms of the New Zealand lowland forest I should like to discuss briefly the term ‘subantarctic rain forest’ as applied by Cockayne to the Nothofagus forests in New Zealand. Cockayne based the name on the Nothofagus forests extending into subantarctic South America and it could be inferred from this name that the subantarctic regions provide the optimum climate for this type of forest. If ‘subantarctic rain forest’ was regarded by Cockayne as a distinct world vegetation type, then I think his interpretation is open to question. As I have mentioned earlier, Nothofagus forest is structurally similar to the temperate deciduous forests of the northern hemisphere, the chief difference being that not all species of Nothofagus are deciduous. In South America there is a mixture of deciduous and evergreen species, in New Zealand only evergreen species, in Tasmania one evergreen and one deciduous species, in Australia and New Guinea only evergreen species. However Russel (1936) points out that some of the New Zealand species might well be described as near deciduous, as it is usually not long after the new season's leaves appear, that the previous season's leaves are shed. In my opinion the Nothofagus forests should be regarded as coming close to the category of temperate deciduous forests. Certainly Cockayne's ‘subantarctic’ forest appears to have very little in common with the subarctic or coniferous forest in the northern hemisphere.
The New Zealand Lowland Podocarp Forest
The accompanying map shows the approximate distribution of lowland forest in pre-European times. Forests in which Nothofagus is present are not shown. It is clear now that the lowland forests must have been even more extensive in pre-Maori times, as it is believed that many of the shrubland areas, particularly in the North Island, resulted from forest fires begun by Maoris. This belief is supported by the frequent appearance in Cook's log of the phrase ‘Fires inland’. The most extensive areas of lowland forest were in the North Island, but the type was also quite well represented in disjunct areas throughout the South Island and in Stewart Island. In the southern half of the country particularly, species become fewer with increasing latitude. An outpost of the forest is to be found in the Auckland Islands which, at 50° south latitude, are about the same distance from the equator as London. The low coastal forests here consist of Metrosideros umbellata (bearing many aerial roots) with a tree fern, Cyathea smithii, in the gullies, more occasional Neopanax simplex, several under-shrubs and several ferns, including six filmy ferns (Hymenophyllum).
Much of the New Zealand lowland forest was destroyed following European settlement, but in most of the original areas stands still remain in national parks, in other reserves, and under management by the Forest Service. In some places also, abandoned land is now reverting to forest.
The composition of the lowland forest is variable. Mostly there is a mixture of podocarps and angiosperms, but in places podocarps may form almost pure stands, or elsewhere, particularly coastally, podocarps may be absent. North of 39° S. the very large trees of the kauri (Agathis australis) play an important role.
In the podocarp-dicotylous forest six layers may be recognised: three canopy layers, a small tree layer, a shrub layer, and a layer of ground plants. The uppermost, usually discontinuous, canopy layer comprises emergent trees, mostly podocarps and Metrosideros robusta, and the two lower canopy layers are mostly dicotyledonous. The small tree layer comprises dicotyledons and tree ferns, the shrub layer mostly dicotyledons, and the ground layer mostly ferns. This stratification is similar to that of tropical rain forest, although in the latter the uppermost canopy layer is formed by dicotyledons only. The usual discontinuity of the uppermost stratum gives a characteristically uneven surface to both types of forest. (Fig. 3.)
In addition to what can be termed self-upholding plants there is usually an abundance of lianes and both herbaceous and shrubby epiphytes. These also are features in common with tropical rain forest.page 105
Life Forms and Geographic Affinities
(1) Trees and Shrubs
In New Zealand the following genera occur in the lowland forests.
|Podocarpus||6/7 T (Gen.)||Libocedrus||½ T (NC.)|
|Dacrydium||4/7 T (M. NG. NC. A. C.)||Agathis||1/1 T (Ph. B. P. A.)|
|Phyllocladus||2/3 T (Ph. B. NG. A.)|
|* Pseudowintera||2/3 T? ()||Corynocarpus||1/1 T (NH. NC.)|
|Beilschmiedia||2/2 T (Gen.)||Pennantia||1/1 T (A.)|
|Litsea||1/1 T (Gen.)||Mida||1/1 T? (JF.)|
|Hedycarya||1/1 T (P. A. NC.)||* Phebalium||1/1 T (A.)|
|Laurelia||1/1 t? (C.)||* Melicope||2/2 T (As. A.)|
|Ascarina||1/1 T (M. NG. P.)||Alectryon||1/1 T (NG. P. A.)|
|Macropiper||1/1 T (NG. P.)||Dodonaea||1/1 T (A.)|
|Melicytus||3/4 T (P.)||Schefflera||1/1 T (Gen.)|
|* Melicytus||1/4 T (P.)||Neopanax||5/6 T? ()|
|* Hymenanthera||1/6 T? (A.)||Meryta||1/1 T (?. NC. A.)|
|Fuchsia||⅓ T (T. S.)||Pseudopanax||6/8 T? (S.)|
|Heimerliodendron||1/1 T (P. A.)||* Pseudopanax||1/8 T? (S.)|
|Avicennia||1/1 T (Gen.)||* Corokia||2/3 t? ()|
|Persoonia||1/1 T (A.)||Griselinia||½ t? (S.)|
|Knightia||1/1 T (NC.)||Dracophyllum||5/35 T (A. NC.)|
|Pittosporum||10/26 T (Gen.)||Planchonella||1/1 T (M. P.)|
|Metrosideros||3/10 T (M. P. A.)||Myrsine||5/9 T (Gen.)|
|Eugenia||1/1 T (Gen.)||* Myrsine||3/9 T (Gen.)|
|Lophomyrtus||½ T? ()||Elingamita||1/1 T? ()|
|* Lophomyrtus||½ T? ()||Gymnelaea||4/4 T (P. NC. A.)|
|* Neomyrtus||1/1 T? ()||* Geniostoma||1/1 T (M. NG. P. A.)|
|Elaeocarpus||2/2 T (Gen.)||Coprosma||8/45 T (NG. P. A.)|
|Aristotelia||½ T (NH. A. S.)||* Coprosma||22/45 T (NG. P. A.)|
|Entelea||1/1 T? ()||Olearia||7/32 T (NG. A.)|
|Plagianthus||1/1 T (A.)||Senecio||1/41 T? (Cos.)|
|Hoheria||4/5 T? ()||* Senecio||2/41 T? (Cos.)|
|Ackama||1/1 T (NG.A.)||Brachyglottis||1/1 T? ()|
|Weinmannia||2/2 T (Gen.)||* Hebe||3/79 t? (NG. A. S.)|
|Quintinia||3/3 T (Ph. NG. A.)||Myoporunt||½ T (As. P. A.)|
|Ixerba||1/1 T? ()||* Rhabdothamnus||1/1 T? ()|
|Carpodetus||1/1 T (NG.)||Vitex||1/1 T? (Gen.)|
|Sophora||2/3 T (Gen.)||Vitex||1/1 T? (LH.)|
|Paratrophis||2/3 T (NG. P.)||Rhopalostylis||1/1 T? (LH.)|
|Paratrophis||⅓ T (NG. P.)||Cordyline||1/5 T (M. NG. P. S.)|
|* Alseuosmia||8/8 t? ()||Dysoxylum||1/1 (AS. M. NG. P. A.)|
Richards describes a number of morphological features which are characteristic of some or most tropical forest trees, e.g. slender trunks with thin, smooth bark; small, little-branched crowns; plank buttresses and stilt roots; pneumatophores; leaves mostly about cherry laurel size, simple, smooth margined, with pulvini and narrow prolongations known as drip tips; coppice shoots from bases of trunks common; cauliflory and ramiflory fairly common; insect pollination thought to be the rule.
Although complete information is not available, trees in the New Zealand lowland forests exhibit many of these features. Cockayne describes the majority of New Zealand trees as having slender, thin-barked trunks and small, dense crowns. Most podocarps, Agathis, the Nothofagus species, Metrosideros, Elaeocarpus and Gymnelaea, are numbered among the exceptions. Plank buttresses are rare, the best example being Laurelia novae-zelandiae (Fig. 7). The species of Nothofagus often have buttresses but these are usually fairly thick, although at times they have been referred to as plank-like. Stilt roots in the true sense are probably not present, although the species of Metrosideros produce aerial roots very readily and in M. excelsa particularly they may become quite massive. Pneumatophores are formed by Eugenia, Laurelia and Avicennia. The average leaf size is probably less than that of the tropical rain forest and, although the leaves are predominantly smooth-margined and undivided, there is a significant proportion of leaves with serrated margins and of compound leaves. Drip tips appear to be entirely wanting and pulvini are developed in Dysoxylum spectabile and possibly some others. Many of the trees produce coppice shoots very readily, e.g. Melicytus ramiflorus, Hedycarya arborea, Elaeocarpus dentatus, Weinmannia racemosa. A good example of cauliflory (production of flowers on the trunk) is found in Dysoxylum spectabile and ramiflory (production of flowers on older parts of branches) occurs in Melicytus, Hymenanthera and Myrsine. The conifers and Nothofagus are wind pollinated, but, with the exception of Coprosma, the other trees and shrubs are probably insect pollinated.page 108
A rather variable deciduous habit is exhibited by the fuchsias, two of the hoherias, Plagianthus betulinus, Muehlenbeckia, Sophora and Aristotelia serrata, but this is not necessarily a temperate feature as the deciduous condition, usually of brief duration, is not at all uncommon in tropical rain forests.
Richards's comment on the juvenile forms of some tropical forest trees is very interesting. ‘A number of large rain-forest trees, which later have normally branched crowns, remain unbranched with their leaves crowded on to the last few centimetres of the stem until they are 6-7 m. or more high.’ This is exactly the situation in several New Zealand species of Pseudopanax, a phenomenon which has puzzled New Zealand botanists for some time. Other New Zealand examples are Elaeocarpus dentatus and Knightia excelsa.
|Tmesipteris||1/1 T (P. A.)||Anarthropteris||1/1 T (P.)|
|Lycopodium||2/12 T (Cos.)||Grammitis||2/5 T (Cos.)|
|Hymenophyllum||9/21 T (Gen.)||Davallia||1/1 T (As. P.)|
|Trichomanes||6/6 T (Gen.)||Arthropteris||1/1 T (NG. NC.)|
|Pyrrosia||1/1 T (Gen.)||Asplenium||1/12 T (Cos.)|
|Phymatodes||3/3 T (A. P.)|
|* Pittosporum||2/26 T (Gen.)||* Senecio||1/41 T? (Cos).|
|* Metrosideros||1/10 T (M. A. P.)||Collospermum||3/3 T (P.)|
|* Weinmannia||½ T (Gen.)||Astelia||2/9 T (NG. A. NC. P. S.)|
|* Neopanax||1/6 T? ()||Dendrobium||1/1 T (M. A. P.)|
|* Griselinia||½ t? (S.)||Bulbophyllum||2/2 T (Af. M. A. S.)|
|* Dracophyllum||⅓5 T (A. NC.)||Earina||3/3 T (NC. P.)|
|* Coprosma||1/45 T (NG. A. P.)||Sarcochilus||1/1 T (I. M. A.)|
|These are also abundant as epiphytes.|
The genera marked * are woody, the remainder are herbaceous. Concerning epiphytes Richards writes, ‘The abundance and variety of epiphytes is one of the most striking differences between the Tropical Rain forest and temperate forests. As well as algae, fungi and bryophytes, the epiphytic flora of the Rain forest includes a wealth of pteridophytes and flowering plants. It is the presence of these vascular epiphytes which especially distinguishes the Tropical Rain forest from temperate plant communities.’ ‘In the Montane and Subtropical Rain forest, the two plant formations most nearly resembling the Tropical Rain forest, the epiphytic vegetation, though less rich in species, reaches a degree of luxuriance seldom approached in the lowland tropical forest.’
Fig. 2 : Forest interior. Kie-kie (Freycinetia banksii) on right. Tree fern is Cyathea medullaris. Gollan's Valley, near Wellington.
Photo: M. D. King
Fig. 3 : Exterior view of lowland forest. Emergent trees along skyline are rimu (Dacrydium cupressinum). Nearer trees are mostly kamahi (Weinmannia racemosta).
Akatarawa, near Wellington. Photo: M. D. King
(Fig. 5) assuming this mode of life more frequently than the other genera. Griselinia lucida usually sends a root to the ground, but does not become independent.
All of the epiphytes listed above can occur as ground plants. Conversely many plants not listed can occasionally occur as epiphytes, particularly on tree fern trunks.
|Lygodium||1/1 T (Gen.)||Rumohra||⅓ T (Gen.)|
|Blechnum||1/15 T (Cos.)|
|Clematis||5/10 T (NG. A. and Temp.)||Parsonsia||2/2 T (M. A. P.)|
|Muehlenbeckia||2/5 T (NG. A. S)||Senecio||1/41 T (Cos.)|
|Fuchsia||⅓ T (T. S.)||Tecomanthe||1/1 T (NG.)|
|Tetrapathaea||1/1 T? ()||Ripogonum||1/1 T (A.)|
|Metrosideros||6/10 T (M. A. P.)||Freycinetia||1/1 T (M. A. P.)|
|Rubus||5/5 T (NG. A. and Temp.)|
Fig. 4 : Epiphytic Collospermum hastatum and Blechnum filiforme. Leaves of Nikau (Rhopalostylis sapida) appearing at left. Gollan's Valley, near Wellington.
Photo: M. D. King
|Korthalsella||½ T (I. M. P.)||Elytranthe||3/4 T (M. A. P.)|
|Loranthus||1/1 T (Gen.)||Dactylanthus||1/1 T (Gen.)|
|Tupeia||1/1 T? ()||Mida||1/1 T? (J.F.)|
The first four genera are epiphytic and belong to the Loranthaceae, the last two root parasites. Richards mentions that all epiphytic parasites of the tropical rain forest belong to the Loranthaceae. ‘Their brilliant colours often make them conspicuous when in flower, A tree laden with Loranthaceae is one of the most beautiful sights of the Malayan Rain forest.’ Several of the New Zealand species of the family an colourful.
|Bagnisia||1/1 T (M.)||Gastrodia||3/3 T (As. M. A.)|
|Corybas||1/8 T (M. A.)|
(6) Ground Herbs
|Lycopodium||1/12 T (Cos.)||Hypolepis||5/5 T (Gen.)|
|Botrychium||½ T (Gen.)||Lindsaea||⅓ T (Gen.)|
|Marattia||1/1 T (Gen.)||Histiopteris||1/1 T (Gen.)|
|Todea||3/3 T (NG. NC.)||Pteris||2/3 T (Gen.)|
|Schizaea||⅓ T (Gen.)||Asplenium||5/12 T (Cos.)|
|Gleichenia||2/5 T (Gen.)||Blechnum||11/15 T (Cos.)|
|Loxoma||1/1 T? ()||Polystichum||3/4 T (Cos.)|
|Hymenophyllum||10/21 T (Gen.)||Ctenitis||3/3 T (Cos.)|
|Trichomanes||6/6 T (Gen.)||Rumohra||2/3 T (Gen.)|
|Thelypteris||2/5 T (Gen.)||Athyrium||2/2 T (Cos.)|
|Leptolepia||1/1 T (NG. A.)||Adiantum||6/6 T (Cos.)|
|Ranunculus||1/43 t? (Temp.)||Galium||3/3 t? (Cos.)|
|Cardamine||1/6 t? (Gen.)||Scutellaria||1/1 t? (S.)|
|Viola||⅓ t? (Temp.)||Libertia||2/3 T (NG. A. S.)|
|Gunnera||3/10 T (Gen.)||Astelia||3/9 T (NG. NC. A. P. S.)|
|Sfellaria||1/6 t? (Temp.)||Dianella||1/1 T (As. NG. A. P.)|
|Urtica||3/6 T (Cos.)||Microlaena||2/4 t? (A.)|
|Elatostema||1/1 T (Gen.)||Gahnia||2/8 T (M. P. A. LH.)|
|Parietaria||1/1 T (Gen.)||Uncinia||12/31 t? (Temp.)|
|Australina||1/1 T (Af. A.)||Carex||8/60 t? (Cos.)|
|Hydrocotyle||5/8 t? (Cos.)||Pterostylis||2/16 T (A. NC.)|
|Nertera||4/6 T (M. A. S.)||Corybas||5/8 T (M. A.)|
Ferns are by far the most common ground herbs and their abundance is a distinctive feature of the New Zealand forests. Angiosperms are generally less abundant except in forest openings or margins.
Summary of Geographic Affinities
Fig. 5 : Neopanax arboreum (Five-finger) epiphytic on a tree fern. Root-stem junction is near top of photograph. Tree fern trunk appears between descending roots of epiphyte. Plateau bush, upper Hutt Valley, near Wellington.
Fig. 6 : Descending rata (Metrosideros robusta) roots on pigeonwood (Hedycarya arborea). Silverstream, near Wellington.
Photos: M. D. King
In the first category 60 genera are largely restricted in their distribution outside New Zealand to the Asian-Polynesian tropics. The remainder are widely distributed in tropical regions, and temperate regions as well in some cases.
Of the third category 2 genera exhibit features generally regarded as tropical. Several species of Griselinia commonly occur as shrubby ground-rooted epiphytes and Laurelia novae-zelandiae has plank buttresses and pneumatophores.
In view of the facts set out above I feel that the conclusion that New Zealand lowland forest is closely related to tropical rain forest is inescapable. I also feel that the use of the term ‘subtropical’ for this forest is justifiable, even though geographic and climatic objections still remain. As mentioned earlier the ideal classification is one based on the nature of the vegetation itself, and it is to be hoped that some botanist with a knowledge of all types of world vegetation will devise such a classification. He would be doing a great service to plant geography.
Chapman, V. J., 1958. The Geographical Status of New Zealand Lowland Forest Vegetation. N.Z. Geographer, 14 : 103-14.
Christ, H., 1885. Vegetation und Flora der Canarischen Inseln. Engler's Jahrbucher, Vol. 6.
Cockayne, L., 1921. The Vegetation of New Zealand. 1st ed., Leipzig.
Cockayne, L., 1926. Monograph on the New Zealand Beech Forests. Part 1. N.Z. State Forest Serv. Bull. 4.
Couper, R. A., 1960. New Zealand Mesozoic and Cainozoic Plant Microfossils. Palaeontological Bull. 32. N.Z. Geol. Survey.
Dansereau, P., 1957. Biogeography. An Ecological Perspective. New York.
Dansereau, P., 1958. Proceedings Ninth Pacific Science Congress. 20 : 57-67.
Polunin, N., 1960. Introduction to Plant Geography. London.
Richards, P. W., 1952. The Tropical Rain Forest. Cambridge. University Press.
Robbins, R. G., 1957. The Status and Classification of New Zealand Forest Vegetation. Ph.D. thesis, Univ. of New Zealand.
Robbins, R. G., 1958. Direct Effect of the 1855 Earthquake on the Vegetation of the Orongorongo Valley, Wellington. Trans. Roy. Soc. N.Z. 85 : 205-12.page 115
Fig. 8 : Entanglement of supplejack (Ripogonum scandens). Silverstream, near Wellington. Photos: M. D. King
Robbins, R. G., 1961. The Montane Vegetation of New Guinea. Tuatara 8 (3) : 121-33.
Russel, R. S., 1936. Mechanism of Leaf-fall in Certain New Zealand Trees. Trans. Roy. Soc. N.Z., 65 : 407-21.
Schimper, A. F. W., 1903. Plant-geography upon a Physiological Basis. Oxford.
Schimper, A. F. W., 1935. Pflanzengeographie auf physiologischer Grundlage (ed. 3). Revised by F. C. Van Faber. Jena.
1 Numbers refer to — number of New Zealand species of genus occurring in lowland forest/total New Zealand species of genus.
- T = genus also occurring in tropical lowland and/or montane forests.
- T? = genus not known to occur in tropical forests, but family chiefly tropical or woody members of family chiefly tropical.
- t? = family chiefly temperate.
- * = shrub.
3 Details of distribution outside New Zealand: Af. = Africa, I. = India, As. = Asia, M. = Malaya, Ph. = Philippines, B. = Borneo, NG. = New Guinea, P. = Polynesia, NC. = New Caledonia, NH. = New Hebrides, A. = Australia, LH. = Lord Howe Island, C. = Chile, S. = South America, JF. = Juan Fernandez, Gen. = widespread in tropics, Cos. = Cosmopolitan, Temp. = temperate, () = New Zealand only.