THE GRASS COVERING OF THE CANTERBURY PLAINS.

Press, Volume LXIII, Issue 19148, 3 November 1927, Page 11

THE GRASS COVERING OF THE CANTERBURY PLAINS.

—♦ (SPECUIXT WRIITBIT TOR THI P&IS8.) [By Professor Arnold "Wall.] 1. Formation and history of Plains.— Built up during the post-Tertiary period mainly of water-borne gravels from the Southern Alps conveyed by the great rivers, formerly much larger than they are now; the Plains are covered with a shallow layer of soil consisting of water-borne sand and wind-borne dust varying greatly in depth in different localities. As the rivers constantly changed their courses successive areas were denuded and then left dry, re-peopled with herbage and re-established as grassland. Portions left long undisturbed, e.g., at the lower end near the 1 Port Hills round to Lake Ellesmere, where the gravels ceased to be deposited by the dwindling current, became swampy and supported heavy bush in places; whereas portions recently established remain long very dry, and these, with the marginal areas of the present river-beds themselves, support a very definitely xerophytic flora. Thus we had (and still have in a fragmentary state): (1) Barren shingle of the active river-bed (e.g., Waimakariri, near Christchurch); (2) very dry areas neighbouring these • beds and in some other localities (e.g., Hororata poor lands); (3) good grassland with comparatively deep soil and good cropping land (e.g., Rblleston and Lincoln districts); (4) swamp (now almost all drained, but near New Brighton and about Lake Ellesmere near Greenpark); (5) damp sedgy ground in hollows, not exactly swamps, as in parts of New. Brighton dunes and formerly in such places as Victoria Lake, Hagley Park;

(6) bush, but this does not concern us in this paper. ; The grass-covering naturally varied considerably according to these variations in cdaphic conditions.

2. Available information on grasslands in old times.—As soon .as white men settled on the Plains cultivation began, and in a comparatively short time the best of the former grasslands were entirely converted to new uses. The river-beds, and their immediate neighbourhood, the sandy dunes of the coast of such areas as Sandy Knolls, near the rivers, and the very barren portions alone escaped. Little or no information seems to be available on the details of the old grassland. No list of species, I think, exists.. Armstrong's list of the plants in the Domain in 1564 printed by Miss Herriott in her [ "History of Hagley Park" includes only eleven grasses, of which I should reckon two very doubtful (Agrostis parviflora, Deschampsia caespitosa). The earliest account of any such area as this known to me is Buchanan's "Sketch of tho Botany of Otago" (Vol. 1., Transactions New Zealand Institute), written before 1865, and he deals only with the grasslands of Central Otago and gives no list of species. In those districts he says simply that tho grass was of very sparse: growth and consisted of three species, meaning, no doubt, as Petrie says in his Report on | the Grass-denuded Lands of Central Otago (1912), Poa caespitosa, Festuca j novae-z'ealandiae, and Agropyrum scabrum*

List of Species (excluding . purely Coastal Species . like Festttca littoralis, AtrbpiS stricta). Large Species. Poa ieaespitosa—Pasture (1); after burning W- --" '•■ Fostuca hovao-zelandiae —Pasture (1): after bnrning (4). : '. . ■' . Agropyrum senbrum—Pasture (1); may be a palatable grass." . . Dicbelacline crinita—Pasture (1); may be a good grass." " '...'' Hierochloe reddens —Swamp (5). , Danthonia Raoulii —High pasture only (1). Danthonia Raoulii var. flavescens —Higb pasture, 400-600 feet (2). Deyeuxia avchoides —Pasture (1) ; placed high by all other authorities. Deyeuxia avenoides var brachyantha—Pasture (as above). Deyeuxia Forsteri—Damp ground; not valued in Cockayne's list. Deschampsia caespitosa—Swamp; not valued in Cockayne's list. Asperella gracilis (probable)— Pasture; no authority values' it at all. Arundo conspicua—Damp ground (1). i.e., about 13 species and varieties, of which five are not pasture-grasses, ' though j two (Hierochloe . and Deschampsia) would i have value for cattle and horses.' ,

Medium Species. Danthonia sami-annularis. —Pasture (3). _ Danthonia ' semi-annularis and varieties— Pasture (3). Danthonia pilosa—Pasture (4). Danthonia-. Buchanani—®ry pasture (Marman) (3). ' . . Poa Colensoi —Pasture (3). 'Perhaps my estimate too high."—Cockayne. Poa intermedia-I—Pasture. 1 —Pasture. (3). _ Poa imbecilla—Shade only; not valued in Cockayne's list.' • • , . '. ~ Trisetum antarcticum —Shade, ; especially damp; not valued by Cockayne. Alopecurus. , not, .in Cockayne's list. .. .. Poa vseticulrais—Coastal .(only!); not in Cockayne's list'. Stipa sotacea (introduced!)— -very dry pasture; not in Cockayne's list. Echinopogon dry pasture (0). Eleven species, of which one or two are doubtful, one probably introduced, and one useless (Poa imbecilla) if it existed on the Plains at all. ' _ , Small Species. / Zoysia pungens—Very dry pasture"; 1 not in Cockayne's list.- . .Triodia cxigua— pasture (0). Poa Maniototo —Very dry pasture (1). Poa Lindsayi—Pasture (1). . Poa exigua—Very dry pasture; not valued in

Cockayne's list. Agrostis muscosa —Damp ground only (near sea); not valued in Cockayne s list, i.e., six species of which at least one would be useless (Agrostis muscosa).

Doubtful Species. Koeleria .Kurtzii —A form ou the Plains is known, but thought to be introduced. Agrostis Petriei—Known in Otago Plains (Petrie). Agrostis tenella—Known in Otago Plains (Petrie) and in Southern Alps. Triodia piimils—Known in Otago Plains (Petrie) and in Southern Alps. Deschampsia riovae-zelnndiae —In- Southern Alps C, 2000 feet. Deveuxia quadriseta—ln Southern Alps C, 2000 feet. Altogether about 25 to 27 species oh the lower Plains; and about six to eight doubt- *"'• ... The . figures in brackets indicate the degree of palatability of each species, with fivo as a maximum, according to Dr. Cockavne's Table published in the New Zealand journal of Agriculture, June, 1019. as a result of his Hanmer experiments. From his statement in 1020 (Journal of Agriculture) I gather that he would give a higher figuro to Agropyrum scabrum than (1) as a result of his Otago experiments. j

4. Comparisons. —(a) With similar land of Central Otago. The areas are very similar in general character and the list of grasses in each almost the same. In Canterbury the very dry areas form a proportionally smaller part of the whole, however, and probably the area of wet land and swamps was proportionally larger. The staple pasture-lands of the districts were no doubt very similar, though the Otago Plains lie. a good deal higher than Canterbury and have a larger proportion of subalpino species. It is doubtful, e.g., whether such a grass as Koeleria Kurtzii or Triodia pumila grew on what we should properly call the Canterbury Plains. The Otago list includes a few species which are not known to me as plants of tho Canterbury Plains, though some of thorn occur in the front ranges of toe Southern Alps. These are: Triodia pumila (OJd Man Eange), Deschampsia hovae-zela'ndiae (Hakatere), Agrostis tenella (Broken Biver), and Poa pusilla (Western Alps generally). On the other hand,! know of no grasses of the Canterbury Plains which are not recorded to have existed in Otago, if the purely, coastal species be excluded.

(*) With the high grasslands of the volcanic plateau. Those high lands remain more or less in their original state over a large part of the district, e.g., included in the Tongariro National Park. My observations were chiefly made on the southern side of Kuapehu, between that mountain and the Kaimanawa Ranges. This plateau is about 2000_ to 3000 feet above the sea. The soil is the usual pumice of that district, and the rainfall is very much greater than with us. "Rabbits are very numerous; sheep have been grazed there for a very long time; wild horses abound, and burning has evidently been very frequent, so that the original associations have no doubt been much disturbed. Still, very few introduced grasses occur except in the immediate neighbourhood of settlements or camps where horses have been used.

The chief point of contrast is in the almost entire absence, in the northern area, of small bottom grasses. All the large species of our list, except Deschampsia caespitosa, were observed and nearly all the medium species. I except only Alopecurus geniculatus and Poa seticulmis. There are a few species unknown to us, at any rate as plants of the Plains, especially the large form of Poa anceps and, in damp places, Trisetum youngii (common in Southern Alps). There is also plenty of Microlaena stipoides, which with us is, I think, only an introduced species (Rangitata Plains). But the small grasses of our list are entirely absent, with the sole exception of Danthonia uuda, and there is in consequence nothing like our pasture. Whether small grasses of . this class have been destroyed by fire or eaten out one cannot say.

Pasture Value. There can be no doubt that the old native grassland at its best, afforded most excellent pasture. But no pure association of native grasses now remains to us on low country. The best' land is under crops and the worst largely invaded by exotics. Even upon the driest and least promising of soils, shingle only just abandoned by the rivers, English grasses appear as soon as natives, and liold their own. Aira caryophylla and Pestuca myuros especially are prominent among these. Some idea of the capabilities of the former pastures may be gained from the present uplands and from tradition, which is regrettably faint and vague. Wa learn, for instance, from old settlers that sheep used to come off the Mackenzie Country "rolling fat" in the early days before English grass penetrated there; and we can see for ourselves how sheep flourish now in such places as the Upper Waimakariri flats or the lower slopes (say to 4000 feet) on the Ashburton Mountains and similar localities where exotics as yet play quite 'a subordinate part in the association.

But in such parts of the Plains as are still grassed, such as the lands closely bordering the great river-beds, tho river-beds themselves, and the areas which are too poor to repay cultivation (as the Itangitata Plains and the poor lands west of Hororata), the continual burning, the frequent overstocking, tho rabbits, and the introduction of exotic

grasses have completely changed the old facies of the country, and no fair inference as to its former carrying capacity can be drawn. No doubt indiscriminate burning on dry lands has done much harm, and native grasses of value have thus been destroyed. As early as 1865 Buchanan gives emphatic warning against this practice.. Petrie's report of 1912 is very strong against it (p. 14). But this is a controversial matter and • beyond, the scope of this, paper. . Looking now at the composition of

tho old pasture and the part played in it by individual species we ; shall prob-. ably find it agreed that the most valu-. able and important native grasses are among the larger kindß of our list: the large' tussocks of Poa and Festuca as shelter grasses for' the smaller kinds and as affording nutriment after .burning:- Agropyrum scabrum, Dichelachne crinita, and Deyeuxia avenoides. The giaflt Toe-Toe and Snowgrass, on one band, and the tiny Agrostis muscosa and Poa maniototo, on the other, are equally useless. Among the medium grasses the most valuable.are undoubtedly the two widely-known Danthonias —D. semi-annularis arid. D. pilosa (with their varieties). Among tho true bottom-grasses the best would be Dan: thonia ' niida and probably Triodia. exigua, Poa Lindsayi, and, if it occurred, Triodia pumila. There is, however, much difference of opinion in respect of some species and especially of Poa colensoi. Petrie is very positive: "This species is l'doubtless the most valuablo of the native grasses. Its tender, palatable, ' nutritious foliage is greedily eaten by: all classes of stock;" and Buchanan says that this grass "is everywhere closely cropped by all kinds' of stockand even in the absence of any analysis may be j accepted as a grass of first-class quality." Oheeseman s,ays: "Poa colensoi is one of the most important of the. indigenous pasture-grasses. It is eaten by all kinds of stock, and is a specially valuable sheep-grass in mountain districts."

Dr. Cockayne, on the other hand, who treats it.together with the larger form known as Poa interinedia,,ranks it comparatively low. In his Table of 1919, based upon his Hanmer experiments, it is valued (3), and he adds.that this estimate is perhaps too high. In his article of December, 1920 (in the Journal of Agriculture), he ranks it below "blue-grass" (Agropyrum scabruin), observing, however, that young plants show niuch higher palatability. In his article of April, 1920, he definitely places it above the two large tussocks (Poa caespitosa and Festuca novaezelandiae) and "considerably lower" than Yorkshire fog, catsear, sorrel, and hawkshead, and "very much lower" than Poa pratensis and cocksfoot. I have myself noticed (for example, on Mt. ■ Herbert) that this grass is very little eaten when there arc other species and especially introduced species in competition with it. I have in my mind's eye certain very nicelooking small tussocks of this grass which to my knowledge have never been touched by sheep for several years (at about 2800 feet on Mt. Herbert), but there is abundance - of other feed in their neighbourhood. In high mountains or subalpine country, however, it would seem that this grass must have the value accorded to it by the authorities just mentioned, as on certain high ridges and tops where sheep continually feed and apparently do well there is practically no other grass present at all. I have noticed this, also, close to the glaciers at the head of the Eangitata Biver or the flats in the river-bed.

Guthrie-Smith in Tutira (1922) pays an eloquent tribute to the value of Agropyruni'' scabrum (blue-grass) as horse-feed, specially referring to experience of it at Mt. Peel in early days. Character of the Old Grassland. This grassland in its virgin state is a thing which has gone from us for' ever. We may imagine what it was, helped out by the character of the subaljpine pastures as they are now in occasional favoured spots. At its best, upon,ihe deeper soils of the Plains, it consisted of very large and thick tussocks, never very far apart, with a rich, deep, continuous mat of smaller grasses completely filling up all interspaces, the whole forming a kind of miniature thicket .impenetrable by the.sun's rays and able to'resist with ease the most furious onslaughts of the north-west wind. As soon as the grass was eaten out sufficiently to leave any

ground bare, deterioration began; and in the absence of a wise, far-seeing policy, such deterioration, aided by over-stocking, injudicious burning', and rabbits, gradually resulted, in certain well-known districts .of Otago and, inland / Canterbury, in mere desolation. But this has not been the fate of any part of the Canterbury Plains proper.

Problems of the Past. These are (1) purely scientific' and (2) economic. . Purely scientific is, for instance, the question what exactly was the composition of the old'grassland, an answer to which is attempted here, and the further question, with respect to its present condition, exactly how much of the result is due to each of the disturbing or destroying factors: the stock, or rabbits, or burning, or introduction of exotic species. Of the Putine. The chief economic question concerns the future of those lands on the Plains which are still predominantly pasture. Can they be improved? Are they now satisfactory, e.g., as '■ drought-resisting pasture? Could any native grasses be reintroduced with advantage into these pastures, and, if so, which particular species? Could any ejeotic grasses be tried, like the Australian or South African or Andean species flourishing in drought-stricken country? Experiments now being carried out by the Agricultural Department in the Mackenzie Country and elsewhere will, it is hoped, supply such data as may enablo these problems to be solved.