The Vegetation of Mount Peel, Canterbury, N.Z. Part 2.*—The Grasslands and Other Herbaceous Communities.
[Read before the Canterbury Philosophical Institute, 10th June, 1925; received by Editor, 15th June, 1925; issued separately, 13th November, 1926.]
Both low and tall tussock-grassland are well developed at Mount Peel. The tendency, of sown grassland, after felled forest, to be succeeded by Poa caespitosa grassland has already been referred to. In this section the modified tussock-grasslands of the montane and the subalpine belts are discussed. In the communities previously described exotic plants are of quite minor importance, but in the grasslands they are of considerable significance, especially from the economic point of view, and they are therefore more fully referred to. In the lists exotic species are distinguished by an asterisk.
The montane low tussock-grassland appears to be a climax association, forest being inhibited by the prevailing strong winds, and by the rainfall falling below the critical point for forest establishment, except in the sheltered gullies such as that of the Lynn stream.
The association clothes the lower slopes of the spurs and valleys facing towards the Rangitata and the Orari rivers, and is replaced at an elevation of some 600 m. by tall tussock-grassland. The dominant species are Poa caespitosa and Festuca novae-zealandiae in varying proportions.
The tall tussock-grassland is the most extensive association at Mount Peel, forming a broad belt between the altitudes, roughly, of 700 m. and 1300 m. Above it merges, often by insensible degrees, into fellfield, and in special circumstances into herb-field; below, it is also often impossible to draw a definite line of demarcation between the tall and the low tussock-grassland. Very clear in the grasslands is the fact that the depth and duration of lie of the snow is the major factor in deciding the altitudinal range of the belts. Very marked, too, is the great change as one passes over from the exposed sunny slopes facing the Rangitata to the more sheltered and shaded southern-facing slopes. The rather open association of the one side is replaced by a compeltely closed association on the other. The sole dominant is Danthonia flavescens. D. Raoulii var. rubra is rare, and confined to sour, boggy ground.
(b.) Festuca Novae-Zealandiae—Poa Caespitosa Association.
1. Composition and Structure.
The number of indigenous species considered true members of the association is 102, representing 74 genera and 33 families. There are
[Footnote] * Part I. in Trans. N.Z. Inst., vol. 56, p. 37.
7 pteridophytes, 30 monocotyledons, and 65 dicotyledons. Of these 53 are more or less common, 40 infrequent or local, and 9 rather rare. There are 17 species of Grramineae, 16 of Compositae, and 13 families are represented by 1 species each.
The growth-forms represented are:—5 small tuberous-rooted summer-green herbs; 13 simple rosette plants; 33 tuft-plants, including 12 tussock or semi-tussock plants; 3 trailing herbs; 36 creeping plants, including 7 turf-forming plants, 16 mat-forming plants; 12 bushy plants, including 4 shrubs and 1 tuft-tree. These may be grouped as herbaceous 77, semi-woody 17, woody 8.
Though the general physiognomy is similar throughout and only one association is recognized, detailed examination shows that the composition varies from place to place. In general Festuca novaezealandiae is dominant over very considerable areas, with Poa caespitosa sub-dominant; but there are also large areas where the relative importance of the two species is reversed, or where the two are present in approximately equal amounts. Abundant members are Agropyron scabrum, its long drooping flowering culms forming in season a striking feature on many slopes, *Agrostis vulgaris, Dichelachne crinita, *Anthoxanthum odoratum, *Rumex Acetosella, Hydrocotyle novaezelandiae var. montana, Nertera dichondraefolia, *Hypochaeris radicata, Helichrysum filicaule, Cotula squalida. Poa Colensoi, Danthonia semi-annularis and D. pilosa, although very common, do not assume the importance or dominance they have in certain low tussock-grassland communities elsewhere. Other very common species are Carex breiviculmis, Luzula campestris vars., Ranunculus multiscapus, Acaena Sanguisorbae vars., especially var. pusilla (but not remarkably aggressive), Geranium sessiliflorum vars., Oxalis corniculata, Epilobium chloraefolium var. verum, Oreomyrrhis andicola var. ramosa, Deyeuxia avenoides var. brachyantha, Wahlenbergia gracilis vars., Celmisia spectabilis, Vittadinia australis var., Gnaphalium collinum, Helichrysum bellidioides, *Trifolium repens, *T. dubium, *Holcus lanatus, *Crepis capillaris, *Cerastium vulgatum.
Often of physiognomic importance are Phormium Colensoi, Cordyline australis, Fuchsia Colensoi, Carmichaelia subulata, this last now closely eaten down. Aciphylla Colensoi is now quite uncommon, odd plants indicating the probable sites of the once striking colonies. Aciphylla squarrosa, now rare except along road-sides, was probably also common, as may have been Angelica montana, now only to be found in places inaccessible to sheep.
On much insolated and wind-bitten slopes the low tussock-grassland may ascend to about 1000 m. altitude, while on steep, shaded spurs tall tussock-grassland may descend to 300 m. Closer examination reveals how surely the composition of the grassland changes in accordance with apparently quite minor variations of slope and aspect. On concave slopes Poa caespitosa at once becomes abundant, with often an increase of Agropyron scabrum and *Agrostis vulgaris. Here also will occur *Holcus lanatus, Hydrocotyle novae-zelandiae var. montana, Chrysobactron Hookeri var. angustifolia, Viola Cunninghamii, Pratia angulata, Microlaena stipoides, Poa Kirkii var., Carex Colensoi, Ranunculus hirtus, Epilobium nerterioides, Anisotome aro-
matica var., Senecio bellidioides, with perhaps odd tussocks of Danthonia flavescens.
Small steep banks usually show Senecio bellidioides, Viola Cunninghamii, Viola filicaulis, Anisotome aromatica, Asplenium flabelli folium, Lycopodium fastigiatum, in fair quantity.
On flushed ground Juncus polyanthemos* var., Schoenus pauciflorus and Carex ternria form colonies, pure or mixed. Here generally is much Chrysobactron Hookeri var. angustifolia, and with other plants coming in, e.g. Mazus radicans, Oreobolus pectinatus, small areas of bog are developed. On dry concave slopes numerous examples of Cordyline australis may occur, presenting a park-like appearance.
On steeper concave slopes much exposed to wind and sun we have a complete contrast. Where not actually occupied by debris scrub, such slopes present an intermediate character. The grassland is open, Pteridium esculentum is often abundant, with sometimes Hypolepis Millefolium and Paesia scaberula. Very often there is much *Verbascum Thapsus, *Digitalis purpurea and *Cirsium lanceolatum. Odd plants of Discaria toumatou, Muehlenbeckia complexa, Rubus australis, R. cissoides, R. subpauperatus and Coprosma parviflora may be dotted about.
Convex slopes and ridges are characterized by the dominance of Festuca novae-zealandiae, and the presence of much Helichrysum filicaule, Leucopogon Fraseri, Blechnum penna marina and Scleranthus biflorus. Other plants more frequent here are Deyeuxia avenoides var. brachyantha, Triodia pumila, Echinopogon ovatus, Muehlenbeckia axillaris, Halorrhagis procumbens, Vittadinia australis var., Raoulia subsericea and R. Monroi.
Where dry rocky outcrops occur the following are usually met with: Poa Colensoi, Danthonia setifolia, Luzula campestris vars., Colobanthus acicularis, Angelica montana, Wahlenbergia albomarginata, Tillaea Sieberiana, Hebe, amplexicaulis, Coprosma brunnea, Brachycome Sinclairii, with certain of the common grassland plants, e.g. Leucopogon Fraseri, Celmisia spectabilis. Where the rocks are damper and more shaded Hymenophyllum multifidum, Anisotome aromatica vars., and Senecio bellidioides will also be present. At the bases of the rocks, if miniature débris slopes are formed, Rubus spp., Hymenanthera dentata var. alpina and other plants of the débris scrub association may be present.
The larger streams in the grassland have their banks occupied by more or less well-developed gully forest. On the smaller ones this is reduced to a thin shrubby margin with Olearia avicenniaefolia and Hebe salicifolia var. communis predominating. Quite small streams are often marked out by lines of Arundo conspicua, broken by sheets of Carex ternaria and Juncus polyanthemos var., or Schoenus pauciflorus.
Certain secondary successions now in progress are here dealt with. Where excessive burning has occurred two successions are set up on sunny slopes that have suffered severely. Both of these probably
resemble in a measure the primary successions on such slopes, with the modifications due to the presence of relies of the original grassland cover, the presence of exotic plants in the neighbourhood, and the presence of stock.
Concave slopes revert to an open débris community in which Pteriduim esculentum is dominant. Rubus australis, R. subpauperatus, R. cissoides occur, usually in quantity, and Epilobium cinereum, E. hirtigerum, *Verbascum Thapsus, *Rumex Acetosella, Coriaria sarmentosa and *Hypochaeris radicata may be abundant. Where consolidated tracks cross these débris slopes Pteridium esculentum disappears and Poa caespitosa or Festuca novae-zealandiae may be plentiful.
In the rabbit-infested area of the Orari side certain burnt-over slopes covered in fine débris are still further depleted of their grassland species, and *Verbascum Thapsus is now present in great quantities, with little else but *Rumex Acetosella and Epilobiun nerterioides. In a few cases spp. of Epilobia are almost the sole plants present.
On other slopes a succession somewhat resembling that occurring on the river-beds is set up. Here on the very open ground Raoulia subsericea, R. Monroi and Celmisia spectabilis are early comers, the mats of the scabweeds forming a seed-bed for grasses and herbs from the adjacent areas. Leucopogon Fraseri and Helichrysun filicaule are also common. Acaena Sanguisorbae var. pusilla, a quite minor feature of the grassland, here becomes aggressive forming mats of fair size. *Rumex Acetosella and *Hypochaeris radicata also spread rapidly and occupy, much ground, as does Blechnum penna marina. Festuca novae-zealandiae gradually regains possession; the seabweeds having played their parts, succumb, and low tussock-grassland is restored.
On the richly manured ground where sheep camp the following form a distinct, if small, community: *Rumex Acetosella, *Stellaria media, *Geranium molle, *Myosotis caespitosa, *Poa pratensis, with which may be *Sisymbrium officinale, *Senecio sylvaticus, *Marrubium vulgare (this last not here forming the large colonies often so characteristic of sheep camps). In some camps there are patches of Cotula squalida forming a dense turf.
(c.)Danthonia Flavescens Association.
1. Composition and Structure.
This lower subalpine association, although much modified, has far fewer exotic species present, both in number of species and in their quantity. Indigenous species, truly members of the community, number 124, representing 74 genera and 28 families. There are 6 pteridophytes, 40 monocotyledons, 78 dicotyledons. There are 25 species of Gramineae, 22 of Compositae, and 8 of Cyperaceae. There are 10 families represented by 1 species each. There are 69 species more or less common, 48 infrequent or local, 7 rather or quite rare.
The following growth-forms are represented: 2 small tuberousrooted summer-green herbs; 21 simple rosette plants; 48 tuft plants, including 9 tussock plants; 35 creeping plants, including 18 matforming
plants; 18 bushy plants, including 14 shrubs; These may be grouped as 90 herbaceous, 13 semi-woody, and 21 woody plants. While in places all the shrubs appear to be true members of the association, in others they are relicts or remnants of former scrub communities.
The dominant plant throughout is Danthonia flavescens, varying in circumference and height according to exposure, elevation, and to the degree of severity of burning to which it has been subjected. There are no plants assuming sub-dominance, but more or less plentiful are: Lycopodium fastigiatum, Carex breviculmis, Deyeuxid aveiuoides var. brachyantha, Danthonia pilosa, Danthonia semi-annularis, Agrostis pilosa, Luzula campesiris vars., Viola Cunninghamii, Epilobium chloraefolium var. verum, Anisotome, aromatica vars., Leucopogon Fraseri, Gentiana corymbifera, Euphrasia zealandica, Nertera dichondraefolia, Lagenophora petiolata, Helichrysum filicaule, H. bellidioides, Celmisia spectabilis, Senecio bellidioides, and at the higher levels Celmisia Lyallii and Hierochloe Fraseri. Other generally distributed species are Blechnum penna marina, Poa Colensoi, Agropyron scabrum, Stellaria gracilenta, Geranium sessiliflorum vars., Pimelea pseudo-Lyallii, Anisotome filifolia, Gaultheria depressa, Celmisia gracilenta. Of exotics *Hypochaeris radicata and *Rumex Acetosella are to be met with throughout, especially in the drier areas, while at lower levels the species found in low tussock-grassland may also be met with.
On the sunny exposed slopes, especially as one ascends, the association is more open than elsewhere, largely owing to the periodical burning of the tussocks, which in the upper portions of the belt has induced an extensive fell-field closely resembling the true lower subalpine fell-field. Celmisia spectabilis is here extremely abundant, and Acaena Sanguisorbae var. pusilla, elsewhere insignificant, becomes, frequent. Koeleria sp., Deyeuxia avenoides var. brachyantha, Poa Colensoi, *Anthoxanthum odoratum, Geranium sessilifiorum vars., and Scleranthus biflorus are more frequent than in the less affected parts.
In the closed association of the southern-facing slopes the above mentioned plants become much less conspicuous, their places being taken by Anisotome aromatica vars., Acaena Sanguisorbae var. pilosa, Viola Cunninghamii, Hydrocotyle novae-zelandiae var. montana. Gaultheria depressa, Forstera Bidwillii, and especially by a marked amount of Celmisia coriacea, Senecio bellidioides. Here too are frequent colonies of Phormium Colensoi, Aciphylla Colensoi, Astelia Cockaynei, Hebe buxifolia var. odora, Hebe sp. (aff. H. Traversii), and in places Coprosma, serrulata. The vegetation becomes much more luxuriant, and exotic species are rare or completely absent over wide areas. These variations are repeated on a minor scale and in a less complete way with the varying aspects of the secondary ridges. On some steep, shaded slopes Blechnum, capense becomes dominant; its brown sheets recognizable from afar, and forming outliers of the Blechnum capense—Phormium Colensoi belt next described.
Flushed areas on concave slopes have present in exceptional abundance Carex ternaria, Schoenus pauciflorus, Oreobolus pectinatus,
Viola Cunninghamii, Forstera Bidwillii, Phyllachne Colensoi, Ourisia caespitosa, and a true bog-community may be developed.
The upper portions of the tall tussock-grassland on the steep slopes leading to the main divide have a very distinct appearance, but the transition is a very gradual one. There is great abundance of Celmisia Lyallii, often of very large size and becoming almost sub-dominant. The soil is of a raw peaty character, almost boggy over much of the slopes, while the snow cover is dense in winter, and remains long. Danthonia flavescens forms smaller tussocks, less densely placed, and between the major plants occur in plenty Astelia montana, A. Petriei, Celmisia coriacea, and within the tussocks Hierochloe Fraseri. Very common too are Lycopodium fastigiatum, Poa imbecilla var., Microlaena Colensoi, Viola Cunninghamii, Gaultheria depressa, Forstera Bidwillii, Ourisia caespitosa, Coprosma repens, Anisotome aromatica vars., Celmisia discolor. The shrubs Dracophyllum uniflorum, Hebe buxifolia var. odora, Hebe lycopodioides, are frequent. On similar slopes receiving rather more sun and wind the ground between the tussocks may be almost bare. In such areas Aciphylla, Colensoi is often conspicuous.
Rocks in the tall tussock-grassland at its lower elevations have a similar assemblage of species to that of the low tussock-grassland rocks. Dry rocks, however, have a greater differentiation of species according to the amount of sun received. On the sun-baked rocks the main species are. Blechnum penna marina, Poa Colensoi, Luzulu campestris vars., Danthonia setifolia, Epilobium pubens (at the lower elevations only), Muehlenbeckia complexa, Leucopogon Fraseri, Pentachondra pumila, Scleranthus biflorus, Helichrysum filicaule, Brachycome Sinclairii (stunted). Shaded rocks are characterized by much more frequent Asplenium Richardi, Anisotome aromatica vars., Suttonia nummularia, Gaultheria rupestris, Celmisia discolor, Senecio bellidioides.
Damper rocks have much the same cover as those of low tussock-grassland, but Hymenophyllum multifidum and H. villosum often make close mats on the steeper faces.
At higher elevations come the rock buttresses and rocky spurs with the Dracophyllum uniflorum shrubland already described. Along streamsides occur shrub communities, often more or less fragmentary, of the types already described, especially Hebe shrublands.
The crests of the spurs are razor-backed and rocky, contrasting with the rounded crests of the lower portions. Characteristic plants, in quantity, of these ridges are Blechnum penna marina, Lycopodium fastigiatum, Halorrhagis procumbens, Leucopogon Fraseri, Pentachondra pumila, with the tussocks of Danthonia flavescens and the rosettes of Celmisia spectabilis smaller and further apart than elsewhere. Frequent also is a woolly form of Craspedia uniflora, near akin to Craspedia alpina. Burning intensifies this open condition, and then Pteridium esculentum, Raoulia subsericea, and the exotics *Anthoxanthum odoratum, *Hypochaeris radicata may appear in noticeable amounts.
In various places shallow depressions occur, in which drifted snow collects, and slowly melting forms temporary pools. If of fair size
the hollow may be bare of vegetation towards the centre, but usually there are patches of a dark moss. Surrounding this come scattered depressed tufts of Poa imbecilla var., with *Rumex Acetosella and *Hypochaeris radicata. Further back still *Agrostis vulgaris forms a turf, merging into a girdle of Festuca novae-zealandiae and Poa caespitosa with *Holcus lanatus, and this again merges as the slope increases into the tall tussock-grassland. At higher elevations Agrostis muscosa takes the place of Poa, imbecilla, and Carex Wakatipu that of *Agrostis vulgaris, while the low tussocks may be infrequent or absent.
Several large slips have occurred in the tall tussock-grassland, especially at its junction with the Phormium Colensoi-Blechnum capense belt. On the bare ground exposed by the slip the loose material develops into a miniature shingle-slip of fine débris. The earliest plants to gain root-hold are Raoulia tenuicaulis, Acaena glabra, Epilobium pycnostachyum, Epilobium melanocaulon var. typica and var. viride, Epilobium pedunculare var., Cardamine heterophylla, Viola Cunninghamii, Myosotis pygmaea var., and *Rumex Acetosella. There is thus an interesting assemblage of plants from the river-bed, the true shingle-slips and the adjacent grassland. The circular mats of Raoulia tenuicaulis widen at a rapid rate, and on them are established Poa caespitosa, Acaena Sanguisorbae var. pusilla, Geranium sessiliflorum, Helichrysum bellidioides, *Poa pratensis, *Hypochaeris radicata, and, of special moment, Coriaria lurida and C. sarmentosa. On the stable ground thus formed other plants of the adjacent grassland establish, Raoulia tenuicaulis and Coriaria form vigorous marginal growth, the various patches finally coalescing to form a close cover, on which Blechnum capense and Danthonia flavescens become aggressive.
Early comers on to rocks exposed by slips are Danthonia setifolia, Poa Colensoi, Anisotome aromatica, Angelica montana and Olearia avicenniaefolia.
B. The Blechnum Capense—Phormium Colensoi Community.
A belt with Blechnum capense dominant, and containing much Phormium Colensoi (sometimes co-dominant) occurs between the tall tussock-grassland and the forest or its shrubland margin. On the southern faces towards the Scotsburn Creek the belt is continuous; elsewhere it is interrupted, occurring on steep slopes above the gully forests and dying out as the more gentle slopes above are reached. The ground is peaty and seldom dry. Blechnum capense covers the ground in great dense sheets, through which grow the numerous Phormium tussocks, while Aciphylla Colensoi and Coriaria sarmentosa are often frequent. Any of the grassland plants may be found, but few and far between. Cassinia fulvida var. montana, C. Vauvilliersii var., Hebe buxifolia var. odora, H. salicifolia var. communis, and Dracophyllum longifolium may be present. In some cases a Hebe scrub appears to be developing, and in others there is certainly an induced succession dominated by Cassinia where fire has succeeded in running through the belt.
C. The Fell-Field Communities.
(a.) General, Composition.
The fell-field belt extends from the tall tussock-grassland to the highest peaks. Although there are several distinct associations, notably the Celmisia Lyallii association of the steeper slopes, and the Celmisia viscosa association of flatter areas, there are many places where these intergrade, and it seems preferable to note the general composition before describing the associations in some detail. There are 73 species true members of the fell-field, representing 46 genera and 22 families. There are 14 species of Gramineae, 19 of Compositae (7 Celmisiae), while 8 families are represented by 1 species each. There are 2 pteridophytes, 20 monocotyledons, and 51 dicotyledons. The following growth-forms are represented: 9 simple rosette plants; 28 tuft plants, including 6 tussocks; 1 trailing woody plant; 25 creeping plants, including 19 mat-forming plants, and 3 cushion or semicushion plants; 10 bushy plants, including 8 shrubs. These may be grouped as 44 herbaceous, 15 semi-woody, 14 woody plants. Of the species 44 are more or less common, 23 are infrequent or local, 6 more or less rare.
(b.) Celmisia Lyallii Association.
On the Rangitata faces this association is very open, the surface dries out readily and is composed of coarse, angular, stable débris. Celmisia Lyallii is dominant, with Danthonia flavescens frequent to sub-dominant. Celmisia spectabilis is plentiful, extremely so where burning has been severe, and here the Celmisia Lyallii is much less prominent. Quite common are Poa Colensoi, *Rumex Acetosella, Aciphylla Monroi var., while fairly frequent are Koeleria sp., Agrostis subulata, Deyeuxia avenoides var. brachyantha, Triodia pumila, Poa Lindsayi, Claytonia australasica, Anisotome filifolia, Epilobium tasmamicum, Stellaria gracilenta, Celmisia discolor. More local, but frequent, are Carmichaelia Monroi, Corallospartuim crassicaule, Myosotis Traversii, Craspedia uniflora var.
Shallow hollows are usually bare, except for scattered small cushions of Agrostis muscosa and marginal Carex Wakatipu. Where streams occur Claytonia australasica forms dense, luxuriant patches. Here too may be small stretches of Schoenus pauciflorus or Hypolepis Millefolium, and in the water great mats of Epilobium macropus and Montia fontana.
The association merges below into the induced fell-field caused by the burning of the tussock-grassland, which may be recognized by the presence of several grassland species not found in the true fell-field, e.g. Raoulia subsericea, Carex breviculmis. Above it merges into the association next described. On the southern slopes the association is much closer and grades into the herb-field. It here looks, at a little distance, like tall tussock-grassland, owing to the luxuriant growth of Celmisia Lyallii, although Danthonia flavescens may be almost absent from wide stretches.
(c.) Celmisia Viscosa Association.
On the wind-swept slopes of Middle Peel, especially on its flattened summit, where snow lies long and drainage is poor, there occurs an open association in which the great mats of Celmisia viscosa predominate. Dracophyllum rosmarinifolium is plentiful, and in places subdominant. On the bare ground between these are the small tufts and cushions of Agrostis subulata, Poa Colensoi, Luzula pumila, Luzula Cheesemanii, Anisotome aromatica var., Aciphylla Monroi var., Drapetes Dieffenbachii, Phyllachne Colensoi, Gentiana corymbifera (stunted), ‘Pygmea pulvinaris, Helichrysum grandiflorum, Celmisia discolor, C. Haastii, C. laricifolia. The cushions and mats are often undermined and dissected by the wind.
The numerous shallow hollows have usually a mossy centre with Carex Wakatipu, Luzula campestris vars., and often abundance of Celmisia Haastii surrounding it. Other hollows are quite bare. Where drainage is freer Celmisia Haastii is especially abundant, C. discolor becomes luxuriant, and Phyllachne Colensoi forms large, vivid green cushions. Here too may be occasional Poa caespitosa, Danthonia flavescens and Celmisia incana var.
(d.) Poa Colensoi Association.
Poa Colensoi, a more or less frequent member of both fell-field and herb-field sometimes produces an induced association where fire has been able to run through the original cover. Celmisia Lyallii, flourishing in the most rigorous situations, cannot long, however, withstand fire, and yields place to the fire-resisting Poa Colensoi. Danthonia flavescens becomes small and decadent, while Gnaphalium Mackayi forms large, low mats, as does to a less extent Raoulia subsericea. Between the Poa tussocks Acaena Sanguisorbae var. pilosa and Celmisia spectabilis are common. Other plants present in this community are Festuca novae-zealandiae, Danthonia setifolia, Plantago Brownii, P. lanigera. Exotics are very rare in this association, but there may be in places a little dwarfed, *Rumex Acetosella. The association occurs at about 1500 m. altitude.
D. The Herb-Field.
True herb-field is developed to only a small extent at Mount Peel, although on the southern faces of the subalpine belt there is much Celmisia Lyallii fell-field which approximates to, and in favourable places—sheltered, gentle, rather shaded slopes—merges into the herbfield now described. Celmisia Lyallii is in general dominant, and is always of physiognomic importance. The following fell-field plants are abundant: Lycopodium fastigiatum, Poa Colensoi, Carex Wakatipu, Luzula campestris vars., Anisotome aromatica vars., Gentiana corymbifera, Celmisia Haastii, C. viscosa. Common are Danthonia flavescens, Viola Cunninghamii, Drapetes Dieffenbachiii, Epilobium tasmanicum, Celmisia discolor. The other members of the fell-field are infrequent or absent.
In addition to the fell-field plants we find Lycopodium Selago, Poa Kirkii, Schoenus pauciflorus, Uncinia compacta, Oreobolus pectinatus,
Ranunculus Enysii, R. gracilipes, R. Monroi forma dentatus, Gentiana bellidifolia, Geum parviflorum, G. leiospermum, Hydrocotyle novae-zelandiae var. montana, Gaultheria depressa, Myosotis pygmaea, Ourisia caespitosa, ‘Euphrasia Monroi, E. Laingii, Plantago Brownii, Coprosma repens, Lobelia linnaeoides, Nertera depressa, Forstera Bidwillii, F. tenella, Senecio bellidioides, Celmisia sessiliflora. The association is thus characterized by its closed nature, the variety and individual abundance of its herbs, and the infrequence of woody plants. On its lower margins it usually merges into a Hebe shrubland. Beyond a rare example of *Rumex Acetosella and *Hypochaeris radicata in barish patches caused by small slips, exotic plants are absent.
In the flushed ground above stream sources Celmisia Haastii assumes a local dominance, giving a greyish green tint to the whole slope. Streamsides are much richer in plants than those of the fell-field. Here to be found are Schoenus pauciflorus in quantity, Scirpus aucklandicus, Carex Raoulii, Poa imbecilla, Cardamine heterophylla var., Oxalis lactea, Ranunculus Monroi, Schizeleima hydrocotyloides, Senecio Lyallii vars., and in the water abundance of Epilobium macropus and Montia fontana. On gravelly margins are Claytonia australasica, Raoulia tenuicaulis, Epilobium pedunculare var.,.Ourisia caespitosa.
E. The Shingle-Slips.
There are a few moderate sized shingle-slips on the slopes of Middle Peel facing south-west. On the coarse, moving rubble of the upper portions at some 1500 m. there are scattered about Poa sclerophylla, Ranunculus Haastii, and less frequently Cotula atrata. A little lower, especially where the débris is finer, occur Epilobium pycnostachyum, Anisotome filifolia, Myosotis Traversii, Acaena glabra, Craspedia alpina. On the semi-stable margins there are many small tussocks of Poa Colensoi, and as these increase in number the surface becomes sufficiently stable for other fell-field plants to gain root-hold.
Rocks jutting up through the shingle-slips have the usual rock-plants of this altitude, and if large give an opportunity for oases of fell-field on their lower margins. Here may be found large low cushions of Leucogenes Leontopodium, sometimes with tuft-plants established on them. Where such a spot is damp through ooze Schoenus pauciflorus may be present in quantity, usually associated with Lycopodium fastigiatum, Ourisia caespitosa, Forstera Bidwillii, Coprosma repens.
F. The River-Bed.
The portion of the bed of the Rangitata River in the area under examination, some 12 km. long, is characteristic of the larger rivers crossing the Canterbury Plain, with its swift, anastomosing streams, and its wide stretches of large boulders margined by flood plains, and backed by steep terraces some 30 m. high. The successions from bare river-bed by way of an open community of Raouliae and Epilobiae to Discaria toumatou shrubland, Coprosma shrubland, or low tussock-grassland, are the same in essentials as those described in the papers of Cockayne (1911), Cockayne and Foweraker (1916, p. 175), and
Foweraker (1917). It does not, then, seem necessary to make detailed references to the phenomena at Mount Peel. Certain matters concerning exotic species are dealt with in a later section.
Worthy of note is the absence or extreme rarity of Helichrysum depressum, the rarity of Coprosma Petriei, Carmichaelia nana, Coriaria lurida, and the comparative infrequence of Raoulia Monroi, and R. lutescens.
Swampland is not much in evidence in our area, and such swamps as occur are mainly indigenous-induced communities, though there are some apparently modified examples of long-esixting swamps in the grassland associations. There are also numerous small swampy areas along slow-flowing streams through the flood-plain of the Rangitata. Where these streams widen into still ponds the water surface shows Azolla rubra, Lemna minor, Myriophyllum propinquum var., Potamogeton Cheesemanii, * Ranunculus aquatilis. On the margins there is usually a girdle of Eleocharis acuta, followed in the shallower water by Carex ternaria and Juncus lampocarpus, and then Carex Gaudichaudiana with Epilobium Billardieranum var. The main swamps are of two types, leaving out the swamp forest and the Leptospermum swamp already described.
(b.)Carex Secta Swamp.
The Carex secta swamps studied are mainly indigenous-induced communities after the removal of forest, and in process of returning to forest. The large, trunked tussocks of the Carex, with immense mop-like heads, which often touch across the intervening water, are very striking. On these heads is often a good deal of Hierochloe redolens as a tuft plant, and sometimes stunted Blechnum capense, Pteridum esculentum, and luxuriant Hydrocotyle novae-zelandiae var. On the water there is much Azolla rubra, here of a sage-green colour owing to the shade of the tussocks. Also common are Ranunculus rivularis, Epilobium pallidiflorum, E. chionanthum, E. insulare, *Mimulus moschatus. Where the tussocks are farther apart are sheets of Eleocharis acuta, and in the deeper water Potamogeton Cheesemanii. Towards the margins will be much Carex ternaria, C. Gaudichaudiana, C. Oederi var. catarractae, and as the grassland is neared *Holcus lanatus, *Agrostis vulgaris, Potentilla anserina var. anserinoides, and other damp-ground plants, e.g. Epilobium nerterioides, Chrysobactron Hookeri var.angustifolia, Pratia angulata, Mazus radicans, with the exotics *Rumex crispus, *R. obtusifolius, *Prunella vulgaris, *Myosotis caespitosa.
The incoming of shrubs, and the development towards Podocarp forest has already been described. Where, however, cattle have access to the swamps, the ground between the outlying tussocks becomes consolidated and dried; * Holcus lanatus and * Agrostis vulgaris increase markedly and form hummocks, while * Trifolium repens often becomes important. The tussocks of Carex secta then die out, as they do after drainage of swamp, and a weedy grass results.
(c.) Schoenus Pauciflorus Swamp.
This community occurs where streams widen out into many channels on the flood plains, and is now much modified, and owing to stock approximates to bog. The few examples still retaining a truly swamp facies are similar in species, other than the dominants, to those of Carex secta swamp, and the transition to grassland is similar. A noticeable feature is the large amount of Olearia lineata, small in the swamps, and reaching a height of about 3 m. on the ‘margins. The green-stemmed variety of Schoenus pauciflorus, though infrequent, is more often met with in the swamp, than in the bogs later described. How far the Schoenus is a true swamp plant, and how far an indicator that bog conditions are approaching my observations are insufficient to pronounce, but the Schoenus seems perfectly at home under true swamp conditions.
H. The Bogs.
True bog is little developed at Mount Peel, although there are numerous boggy patches, already referred to, in the low and tall tussock-grassland, and in fell- and herb-field. There are some small patches of Schoenus pauciflorus bog in the montane grassland, conspicuous owing to the brownish-grey tint of the dominant plant, which form a close cover of tussocks. Associated with the Schoenus are Sphagnum sp., now present only in small amounts and in a depauperated condition, Oreobolus pectinatus, Carax stellulata, C. Gaudichaudiana, small Hierochloe redolens, Chrysobactron Hookeri var. angustifolia, Luzula campestris var., Halorrhagis micrantha, Viola Cunninghamii, Nertera depressa, Pratia angulata, Drosera Arcturi, Anisotome aromatica var., Microtis unifolia, Prasophyllum Colensoi, Celmisia gracilenta, and less commonly Blechnum penna marina, Utricularia monanthos, Mazus radicans, Plantago triandra, Aciphylla squarrosa, Olearia virgata var.
I.The Rock Communities.
(a.) Vegetation Of The Upper Subalpine Rocks.
The rock-plants of the lower belts have already been dealt with. There remains the distinctive vegetation of the rocks of the highest peaks. The great masses of jagged rocks at the summit of Big Mount Peel at about 1700 m. have in the crevices exposed to the most rigorous conditions of wind and sun ‘the following species of common occurrence: Danthonia setifolia, Agrostis subulata, Poa Colensoi, Colo-banthus acicularis, Exocarpus Bidwillii, Dracophyllum rosmarinifolium, Hebe Cheesemanii, Raoulia eximia, Leucogenes grandiceps, Celmisia incana var. Less common are Trisetum subspicatum, Wahlenbergia albo-marginata (with thick succulent leaves), Hebe amplexicaulis, Coprosma sp. aff. propinqua, Pimelea Traversii.
The large fissured blocks at the bases of the rocks are characterized by dense rounded masses of Dracophyllum uniflorum, cushions of Hymenanthera dentata var. alpina, and occasional Aciphylla Colensoi. The damper, more shaded, and less exposed crevices contain more soil and have Polypodium pumilum, Poa imbecilla var., Marsippospermum gracile, Cardamine depressa, Ranunculus Monroi formadentatus
(very small, and shaggy with ferruginous tomentum), Anisotome, aromatica, Epilobium tasmanicum, Aciphylla Monroi (much more luxuriant than in the open fell-field), and Leucogenes Leontopodium. Polystichum cystotegia is a member at rather lower elevations, where other species, e.g. Celmisia discolor, Myosotis australis, show a transition to the rocks already described.
(b.)General Composition And Growth-Forms.
Taking the area as a whole the plants found on rocks may be grouped as follows: plants of wet rocks 46, including 11 pteridophytes, 10 monocotyledons, 25 dicotyledons; plants of dry rocks 69, including 11 pteridophytes, 10 monocotyledons, 48 dicotyledons; plants apparently indifferent as to wetness or dryness 15, including 2 pteridophytes, 1 monocotyledon, 12 dicotyledons. There are 15 species of Polypodiaceae, 13 of Gramineae, 9 of Scrophulariaceae, 15 of Compositae.
Of the 130 species 1 is a small, tuberous-rooted summer-green herb; 14 are simple rosette plants. 45 are tuft plants, including 12 ferns, 16 grasslike tufts or tussocks; 1 is a woody, trailing plant; 4 are woody lianes capable of forming mounded masses in the open; 33 are creeping plants, including 12 mat-forming plants; 32 are bushy plants, including 5 cushion or semi-cushion plants. They may be grouped as herbaceous 69, semi-woody 18, woody 43.
Of the 130 species allowed as true rock-plants 83% are found in other stations, but comparatively infrequently. A number of species not included may occasionally be found on rocks, where e.g. the crevices are wide, deep, and contain much soil. The plants that are entirely confined to rocks at Mount Peel, as far as my observations go, are Cheilanthes Sieberi, Asplenium Richardi, Polypodium pumilum, Polystichum cystotegia, Colobanthus acicularis, Cardamine depressa, Angelica montana, Pimelea Traversii, Hebe Cheesemanii, Hebe amplexicaulis, Hebe Allanii, Veronica Lyallii, Veronica linifolia, Raoulia eximia, Leucogenes grandiceps, Helichrysum Selago. Almost entirely so is Hymenophyllum pulcherrimum.
J. The Exotic Plants.
Thanks to the work of Cockayne the very prevalent misstatements in biological literature as to the powerlessness of the indigenous species to hold their own in competition with exotic species have been sufficiently refuted, and the true, position has been clearly stated. Reference may especially be made to his remarks in Section 5 of The Vegetation of New Zealand (1921, p. 280 et seq.), and it will suffice to say here that my observations at Mount Peel completely support his contentions. One or two matters may, however, be referred to. My list includes 143 species, but it should be stated that the gardens and waste-places near the village were not searchingly examined, and doubtless contain a number of species not noted, but these are of no moment from the point of view of the present paper. Of the 143 species, 35 are either rare or very infrequent; 23 are practically confined to cultivated land; 22 are confined to road-sides, hedgerows, and
waste places near the village; 9 have been intentionally sown; 9 are found as weeds of the artificial pastures; 10 are found in running water; 3 are found on swamp-margins where cattle run; 12 colonize débris slopes in the low tussock-grassland, and the open riverbed; 20 occur in the much-modified parts of the tussock-grassland. Species that play any significant part in the various indigenous associations have been mentioned when discussing these. There are 23 species of Gramineae, 16 of Compositae, 14 of Leguminosae, 13 of Caryophyllaceae, 10 of Scrophulariaceae, 9 of Rosaceae. The 143 species represent 99 genera and 35 families, and include 58 annuals.
(b.) Exotic-Induced Communities.
1. *Ulex europaeus Thicket of the Riverbed.
This association now occupies very large areas on the riverbed of the Rangitata, and completely overshadows the remnants of the indigenous Discaria toumatou thicket. It must, however, be emphasized that this development occurs only on the main river-bed where water-supply from beneath is considerable. On the small shingle-fans where the mountain streams debouch on to the terraces, and on the smaller stream-beds incised in these terraces the conditions are much more xerophytic. The layer of shingle before water is reached is much thicker, and the volume of water very much less. Here * Ulex europaeus is quite subordinate in amount, and occurs but rarely in the initial stages. Discaria toumatou thicket or mixed Coprosma shrubland are still the marked physiognomic features of these situations.
There is said to have been no Ulex on the Rangitata riverbed prior to 1873, about which time the plant was freely used for hedges. The account here given refers to the present state of affairs. On the recently vacated bed, for the most part covered with large boulders, odd plants of * Ulex europaeus and * Cytisus scoparius have established themselves. Between these are occasional small plants of any of * Holcus lanatus, * Agrostis vulgaris, Poa Lindsayi, * Aira caryophyllea, * Festuca bromoides, Muehlenbeckia axillaris, *Trifolium repens, Epilobium microphyllum, E. pedunculare var., * Hypochaeris radicata, Gnaphalium luteoalbum, Raoulia australis, R. tenuicaulis, and more rarely several other species. When floods occur patches of silt form round the Ulex, and on these patches * Agrostis vulgaris, * Rumex Acetosella, * Trifolium repens, Acaena microphylla, A. inermis form a turf. The small mats of Muehlenbeckia and Raoulia also collect silt and extend their borders, forming a seed-bed for various species, including Poa caespitosa. Usually the Ulex grows rapidly, seeds profusely, and forms dense patches that coalesce to form thickets under which the other plants become decadent. Successive floods increase the depth of the silt and completely bury the boulders. At this stage * Holcus lanatus and * Anthoxanthum odoratum are almost the only survivors below the Ulex.
Such thickets are often burnt and the sandy surface exposed. Ulex regenerates from the base and may be cropped by rabbits and sheep to a dense cushion form. The bare sand becomes occupied by * Holcus lanatus, * Rumex Acetosella, Oxalis corniculata (often very abun-
dant) and a brown moss. Here too Raoulia lutescens, uncommon on the original riverbed, is often quite frequent. In places Triodia exigua, * Poa, pratensis, * Agrostis vulgaris, * Trifolium repens greatly assist in forming a turf. Such an area if stocked with sheep and the rabbits kept in subjection becomes an exotic-induced grassland that is invaded by Poa caespitosa and Festuca novae-zealandiae which produce a grassland very similar to the modified low tussock-grassland of the terraces. If the Ulex is not kept down it soon re-establishes a thicket.
2. * Ulex europaeus Thicket of the Hillside.
Great thickets of Ulex form a striking feature of certain hill-slopes on the Rangitata face. A similar thicket of * Cytisus scoparius occurs on one slope in the montane tussock-grassland.
Some fifty years ago a * Ulex europaeus hedge of the “bank and ditch” type was constructed from one gully forest to another across a “saddle” at 500 m. altitude. The hedge was on a sunny slope facing the east and ran through the Blechnum, capense belt and the lower tall tussock-grassland. From this hedge have developed the thickets now found, which are still extending their margins. Burning and cutting have been attempted from time to time, but never in a wholesale manner, and sufficient Ulex has always been left to reseed the burnt areas under more favourable conditions than before, while regeneration from the burnt stumps has been abundant. Over a considerable portion of the infested area the original associations have been obliterated. Towards the margins the course of the struggle may still be followed. The seedling Ulex grows rapidly, shading the herbaceous plants, which become drawn up and etiolated, and gradually succumb. Danthonia flavescens, Phormium Colensoi, Aciphylla Colensoi, and various shrubs, persist longer, but are killed out by the burning so that finally there is an almost pure Ulex association. In places, however, * Holcus lanatus and * Anthoxanthum odoratum are plentiful, with distant-noded culms stretching up through the bushes.
Where burning has been unusually severe on dry, sunny slopes Pteridium esculentum, may occur plentifully and even dominate the Ulex.
A noteworthy feature is the ready downward migration, of the * Ulex, and the much slower upward movement. Above an altitude of some 550 m. Ulex loses its aggressive powers and is represented by odd stunted bushes, and above 600 m. is hardly to be found at all.
K. Floristic Notes.
It does not seem necessary to provide a complete list of species noted, but as, in general, only the commoner species have been mentioned in the body of the paper, attention may be drawn to the presence of certain of the rarer species. Of species previously recorded for Mount Peel I have failed to discover Veronica anomala, which is mentioned by Cheeseman in the Manual ed. 1 (1906), p. 523) on the authority of Armstrong. I have, however, observed certain narrow-leaved forms of Hebe buxifolia that, as Cheeseman remarks, approach Veronica anomala somewhat closely.
The species noted by me may be tabulated as follows:
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There are 33 species of Polypodiaceae, 40 of Gramineae, 31 of Cyper-aceae, 27 of Onagraceae, 24 of Rubiaceae, 62 of Compositae, while there are 22 families represented by 1 species each. Of genera Carex has 18 species, Epilobium 24, Coprosma 17, Celmisia 11.
Attention may be drawn to the presence of: Gleichenia circinata var. hecistophylla—ridges in hillside forest, very rare; Cyathea Cunninghamii—plentiful in oen locality in hillside forest; Libocedrus Bidwillii—in hillside forest, rare; Hierochloe Fraseri var. recurvata—upper tall tussock-grassland; Deyeuxia Youngii var. Petriei—in Blechnum capense belt, rare; Deschampsia tenella—in lower fell-field, rare; Poa dipsacea—in herb-field, rare; Carex comans var. pulchella —in lower forest; Luzula Cheesemanii—in upper fell-field, rather rare; Astelia Petriei—in tall tussock-grassland, local; Korthalsella salicornioides—on Leptospermum ericoides, plentiful in one locality; Clematis foetida var.?—a small shrubland plant; Ranunculus Enysii —in herb-field, rare; Pittosporum Colensoi var.?—a small tree, very distinct from P. tenuifolium, and also from northern forms of P. Colensoi, not seen in flower or fruit, gully forest, rare; Carmichaelia flagelliformis—so named by the late Mr. Petrie, in lower subalpine scrub, rare; Edwardsia microphylla×prostrata—in débris scrub in one locality, near the Rangitata Gorge; Epilobium pedunculare var. minutiflorum—along stream beds, infrequent; Schizeleima hydrocoty-loides—by streams in herb-field, rare; Angelica decipiens—in tall tussock-grassland;×Hebe Kirkii—river terrace shrubland, very infrequent; Hebe Cheesemanii (= Veronica quadrifaria of the Manual) —Summit rocks, plentiful; Veronica linifolia—rocks by streamsides, noted in one locality only; Euphrasia Laingii—in herb-field; Plantago lanigera—very infrequent; Coprosma areolata—forest-margin, rare; Nertera Cunninghamii—exactly matching the North-west Nelson plant, noted in one locality only; Lobelia linnaeoides—herb-field, infrequent; Olearia Haastii—by streams in tussock-grassland, very rare; Olearia fragrantissima—Lynn Valley, not common; Celmisia incana var.?—a rock-plant near summit, possibly sp. nov., common; Celmisia coriacea×Lyallii—fell-field, rare;×Helichrysum Purdiei —by stremside, Lynn Valley, infrequent; Cotula pectinata—fell-field, infrequent.
The new species discovered were Gaya Allanii—forest-margins, a few plants noted; Hebe Allanii—a rock-plant in tussock-grassland, noted in two localities, and there common.
Cheeseman, T. F., 1906. A Manual of the New Zealand Flora, Wellington.
Cockayne, L., 1911. “On the Peopling by Plants of the Subalpine River-bed of the Rakaia (Southern Alps of New Zealand),” Trans, and Proc. Bot. Soc. Edin., vol. 24, p. 104.
Cockayne, L, 1921. Die Vegetation der Erde, 14, Vegetation of New Zealand. Leipzig.
Cockayne, L, and Foweraker, C. E., 1916. “Notes from the Canterbury College Mountain Biological Station: No. 4—The Principal Plant Associations in the immediate vicinity of the Station,” Trans. N.Z Inst., vol. 48, p. 166.
Foweraker, C. E., 1917. “Notes from the Canterbury Mountain Biological Station, Cass: No. 5—The Mat-plants, Cushion-plants, and Allied Forms of the Cass River-bed (Eastern Botanical District, New Zealand).” Trans. N.Z. Inst., vol. 49, p. 1.