Art. XVIII.—Notes from the Canterbury College Mountain Biological Station.
No. 3.—Some Economic Considerations concerning Montane Tussock Grassland.
[Read before the Philosophical Institute of Canterbury, 1st December, 1915.]
Montane low tussock grassland is not really sharply defined from lowland low tussock grassland, both being very similar associations of the same climatic formation. The term should be applied only to that tussock association in which Festuca novae-zealandiae (Hack.) Cockayne is the leading physiognomic plant, while lowland tussock grassland should be restricted to that where the characteristic tussock growth-form is represented by Poa caespitosa Hook. f. As implied by the name, lowland tussock grassland is normally developed on land of low elevation, and rarely ascends higher than 1,000 ft. Poa caespitosa, however, is not uncommon at higher elevations, but is then mainly confined to moist places along the sides of streams and on the outskirts of forest, and rarely becomes the dominant element of the open grassland. Between true lowland tussock and true montane tussock many intermediate stages can be found, where both Festuca novae-zealandiae and Poa caespitosa are in more or less equal quantity.
Much of the vegetation in the vicinity of the Cass Mountain Biological Station is typical montane low tussock grassland, and, in fact, it is the main climax association, apart from mountain southern-beech forest, of all the area up to an altitude of over 3,000 ft. This is not to say that many other associations are not present; but they nearly all are stages in the ultimate production of montane grassland which appears to be under natural conditions, the final vegetation of the land-surface, except in sheltered situations, where true forest may be developed. The presence of this uniform climatic formation, characterized by the complete dominance, so far as general appearance is concerned, of the even-sized and almost evenly spaced tussocks of Festuca novae-zealandiae, is the special vegetation feature of the valleys and slopes of the mountain-ranges east of the dividing range of the South Island
2 Area and Distribution
Montane tussock grassland is especially characteristic of the South Island,* and comprises an area of over 6,000,000 acres, or, roughly, one-
[Footnote] * In the North Island there is a considerable area of the formation here being dealt with situated on the Volcanic Plateau southwards of Mount Ruapehu with Festuca novae-zealandiae or a closely related variety or species dominant. The Waimarino Plain, on the contrary, on the west of the volcanoes, although at about the same altitude (3,000 ft., more or less), has Danthonia Raoulis Hook f as its dominant tussock.
seventh of the occupied land of New Zealand. This great plant formation stretches in an almost unbroken line from the Wairau River in Marlborough to the heavily wooded mountains of Southland. It forms a broad belt, interrupted here and there by forest, mainly of the southern-beech — Nothofagus cliffortioides (Hook f.) Oerst. — type, between the agricultural land of the lowlands and the subalpine belt. It occupies both valleys and mountain-slopes with its uniform vegetation, and gives a rather monotonous aspect to the landscape, on account of its uniform height and unvarying brownish-yellow hue.
The montane tussock grassland districts of the South Island form one of the few types of vegetation on occupied land that has, in general appearance and in the permanence of its dominant elements, apparently remained comparatively unchanged since the advent of the white man. In certain localities—notably in Central Otago and portions of South Canterbury—this primitive formation has been profoundly modified; but in general the montane tussock grasslands are superficially, and so far as their effect on scenery is concerned, in much the same condition as when first brought under occupation.
The montane tussock grasslands have been utilized as sheep-grazing pasture for over half a century. For this purpose they were immediately available in their primitive condition, and they were amongst the first of the areas used for pastoral purposes, ranking in this respect with the original employment of the lowland tussock grasslands. They represent one of the few natural resources of the Dominion that have remained a permanent asset without having to be intentionally modified or specially treated to render them capable of continued production. The same statement would also be true of the primitive lowland tussock associations, but it was early recognized that the land occupied by the latter was in many cases admirably adapted for ordinary farming operations. Thus the replacement of the Poa caespitosa association by artificial associations both of a temporary and semi-permanent nature became a general practice. To-day much of the lowland tussock grassland has been converted into arable farms, and even where the plough could not be utilized the extensive surface-sowing of European grasses on the ashes formed by the burning of the tussocks has in many places completely changed the original vegetation. With the montane tussock grassland such has not been the case, and it is only in isolated instances that the original vegetation has been eliminated and replaced by artificial associations.
It may appear strange that in New Zealand, where the general trend of farming operations is in the direction of increasing the carrying-capacity of land, comparatively no effort is made towards any improvement in the utilization of the montane tussock grasslands. For the past fifty years the methods adopted have not varied except in one particular—namely, in a change in the type of sheep that is used. In the early days nearly the whole of the flocks on the upland sheep-stations of the South Island were merinos. This was due largely to the fact that in Australia this was the dominant breed, and that New Zealand was originally mainly stocked from that country. During the past twenty years, however, the merino flocks have suffered a great decline, and their place on the montane tussock-land has been very largely taken
by half-bred and cross-bred sheep. Apart, however, from a change in the type of sheep carried, no attempt has really been made to improve the carrying-capacity of the grasslands themselves. Certainly during recent years a controversy has raged on the advisability of burning montane tussock grassland, but no finality has been reached regarding this procedure, although there is a growing tendency to restrict burning to special times and places.
There are, however, three distinct factors to which must be attributed the lack of any progression in the utilization of upland tussock grass-lands. Briefly expressed, these three factors may be summarized under the following heads: (1.) The fact that the greater part of the land is held under a system of short leasehold. (2.) That our knowledge of what plants could be profitably substituted for the present vegetation is almost nil, and the methods for the payable establishment of such plants are quite problematical. (3.) That the individual runs are in general so large that they furnish ample incomes to their holders without the adoption of any special methods of soil-utilization.
In general, sheep-stations which consist largely of montane tussock grassland are situated in mountainous districts, and their higher portions consist of subalpine and alpine associations. The former are largely used for grazing purposes during the summer; hence the term “summer country.” The lower montane belt is generally called “winter country,” as it is the only ground on which stock can be carried during the winter months. Thus on many stations the montane tussock grassland is without stock for considerable periods of the year, and especially at that period when the grasses are in flower and seed. During the winter, however, this tussock land, especially that portion lying towards the sun, is wholly responsible for the carrying of all stock, as comparatively no provision is ever made for the production of special winter feed. This is perhaps the most striking difference between the methods adopted on lowland and upland sheep-runs. At times, in the neighbourhood of the homesteads themselves, a little cultivation is carried on, but this is almost wholly in the direction of providing chaff for the working-horses of the station. A few paddocks of European grasses may also be laid down, but the prevalent custom of using mixtures largely composed of rye-grass (Lolium italicum A Br.), which dies out in a year or two, has discouraged any extensive development in this direction. On certain stations, however, excellent home paddocks of cocksfoot (Dactylis glomerata L.) are established, and it seems reasonable to expect that such a practice would become largely extended were the individual holdings smaller.
No fattening for market is ever attempted on true montane sheep-country, but on most stations a certain number of store sheep may be annually disposed of. In certain seasons, however, the winter mortality is so high that the normal number of stock carried cannot be maintained without extensive outside buying.
Reliable figures on the number of sheep carried on the montane tussock grasslands are not available, but from a careful computation from the sheep returns I estimate it at about two millions, or, roughly, one-twelfth of the sheep of the Dominion. As the area under discussion comprises about 6,000,000 acres, this gives a carrying-capacity of one-third of a sheep per acre. In point of fact, however, I think this estimate is on the high side.
4. The Leading Grasses.
The two leading grasses of the montane tussock grassland are the fescue tussock (Festuca novae-zealandiae) and the blue tussock (Poa Colensoi Hook. f). It is generally conceded that the fescue tussock itself is of little value, but that it affords an indispensable shelter where the more palatable elements of the vegetation are able to develop. The culms of the fescue tussock are from 6 in. to 2 ft. in height. The leaves are hard, harsh, narrow, and involute, persisting in a living condition for a long period, and gradually drying off at the tips; when quite young they are relished by sheep, but in an ordinary tussock they are so protected by the older leaves that it is impossible for sheep to graze on them. This is clearly seen when an area is overstocked; the sheep rapidly lose condition, but there is no palpable alteration in the tussocks, and they are never grazed down. When rabbits are abundant, however, the tussocks are often eaten, so that they look like inverted brushes. It would thus seem that the fescue tussock is of little value as sheep-feed, and as on an average over two-thirds of the vegetation consists of this plant the small carrying-capacity of montane tussock grassland is easily explained. Whether or not the fescue is indispensable for the growth of the other elements of the vegetation is not clear, but it seems feasible to expect that, as the formation is clearly a climatic one, the dominant plant must play an important part in this respect.
The blue tussock (Poa Colensoi) is generally looked upon as the most important feeding-element of the montane tussock grassland. It forms much smaller tussocks than does the fescue, and at times fills in most of the intervening spaces. For my part, I think that the feeding-value of the blue tussock has been exaggerated. Even on land recently grazed very little sign of actual feeding-down can be seen, but certainly sheep do much better on land where there is an abundance of this grass than on land where it is scarce. The blue tussock is, however, especially eaten by rabbits, and they graze it almost bare to the ground, totally preventing any seed-production. In the district surrounding the Cass Biological Station rabbits have always been practically non-existent, and it consequently affords a most excellent locality for a complete study of the plants actually eaten regularly by sheep, as these are virtually the only class of stock that has ever been pastured there. In many areas of the montane tussock grassland the blue grass, Agropyron scabrum Beauv., is an important constituent, and its flat glaucous leaves are regularly eaten by sheep. In the vicinity of the Cass Station this grass is exceedingly rare, and it has either never been common there or else has been completely eaten out by sheep.
With regard to the other elements of the montane grassland vegetation it is evident that certain of them afford palatable sheep-feed, for I am certain that those plants most abundant—namely, the fescue tussock and blue tussock—are by no means responsible for the sustenance of the stock carried. It, however, has to be remembered that a carrying-capacity of at most one-third of a sheep per acre does not require a large amount of herbage; and were all the vegetation of the montane grassland fed upon, the number of sheep carried would be far and away greater than it is at present. The way that such unlikely food-plants as those belonging to the genera Aciphylla, Discaria (when burnt down), and Carmichaelia are cropped down but left severely alone on land where feed is abundant is a clear indication that palatable feed is really scarce. A really proper investigation of the plants affording
regular sheep-feed on the montane tussock grassland is badly needed, and for this purpose the fencing-off and feeding-off of small areas is necessary.
5. Changes in the Vegetation.
It is impossible to describe accurately the analytical composition of really primitive montane tussock grassland. The whole area now occupied by this formation has been for sixty years subjected to the modifying influence of grazing, a factor absent in the arrangement and constitution of the primitive vegetation. It is generally assumed that the montane tussock grassland has not altered to any appreciable extent except in so far as the naturalization of exotic species is concerned. It is also generally thought that certain elements of the vegetation not primarily of any importance in the general physiognomy of the formation have become gradually rarer and rarer.
It is, however, fully recognized that over certain areas where through special circumstances the dominant tussock growth-form has been eliminated profound alteration has occurred. This has resulted in the production of a totally different formation, approaching the desert type. Whether or not this new vegetation is a stable permanent one or is merely a transitory type leading to more closed types of associations is not known, but I am inclined to think it is a climax one so long as the present grazing-conditions remain the same. This replacement of montane grassland by a desert or semi-desert type of formation has occurred over wide areas in Central Otago and the Mackenzie country. There the extremely low rainfall, coupled with the various new conditions brought into activity by man's utilization of the land for pastoral purposes, can be held responsible for this remarkable substitution of one formation by another in no way related either taxonomically or ecologically. Over the montane tussock grassland subjected to a rainfall of approximately 30 in. per annum no such radical change has taken place. Nevertheless, with the exception of the rabbit factor (admittedly more important in the so-called “depleted areas”) this grassland has been subjected to the same general pastoral conditions as that where complete replacement has taken place. In general character the montane tussock grassland in areas of moderate rainfall has, apart from the presence of introduced plants, a distinctly primitive appearance, due to the apparently unchanged dominance of the tussock growth-form. It, however, seems impossible to think that profound changes have not taken place apart from the gradual reduction in frequency of occurrence of certain species. At any rate, the wiping-out of certain elements, where this has occurred, must have resulted in their replacement by other plants. If such had not been the case a general opening-up of the formation would have taken place, and steppe would have been produced. The production of steppe from tussock grassland has not, however, taken place in localities of moderate rainfall, except in isolated cases where some specially unfavourable soil or climatic factor, such as wind, has exerted a preponderating influence. Thus, if it is assumed that the relative frequency of certain species has diminished, it is also fair to assume a corresponding increase of other species. It is, however, quite probable that in the depleted areas the grassland degenerated into true steppe before final replacement by desert and semi-desert associations took place. It is generally said that the effect of stock has been to reduce very largely what runholders call “the better and finer
grasses,” whatever may be meant by that very general phrase. If a certain proportion of the original vegetation has been more or less eliminated — which there seems no reason to doubt — the remarkable feature of the present-day montane tussock grasslands is that the dominant growth-form has remained permanently the same. Replacement has been in the direction of an increase in the dominance of the tussock growth-form rather than in any reduction. This unexpected happening is perhaps one of the most remarkable ecological facts with regard to the influence of stock on a primitive New Zealand association capable of sustaining grazing animals. The lowland tussock grassland, for instance, has in many instances been replaced by a partial sward grass, Danthonia pilosa. Fern heath has in many places been turned into meadow land simply by means of stock and the invasion of introduced plants Phormium tenax areas on comparatively dry land have by heavy stocking been replaced by sward grasses. Coastal and rain forest have been destroyed in a similar way. In these cases the leading physiognomic plants of the primitive associations have been more or less eliminated and replaced by species of a different growth-form, and that not of the tussock type. In the montane tussock grassland areas, with the exceptions already mentioned, the original dominant growth-form has, in spite of grazing, burning, and other introduced factors, become, if anything, intensified rather than reduced. Again, this tussock growth-form is a climax one, and had attained its dominating position in the vegetation in the complete absence of any grazing animals.
More remarkable still is the fact that many of the areas of southern-beech forest in the montane tussock belt which have been destroyed by man's activity, and not sown intentionally, have developed into typical present-day montane tussock grassland. It would thus appear, then, as if the tussock growth-form is the only one that is capable of remaining permanently dominant over the montane tussock grasslands.
In most cases Festuca novae-zealandiae is the species showing this great dominance, but in certain instances other plants with a similar growth-form are locally the more important. Festuca novae-zealandiae is extremely specialized, and variation in habitat is not followed—as in many other plants, such as Leptospermum scoparium, for example—by an alteration in outward form. It seems reasonable to suppose that specialization in form would render a plant capable of occupying only special stations, and that any wide variation in habitat would act unfavourably towards its continued establishment. With the fescue tussock no such restriction to any one special station is apparent. The great area occupied by the montane tussock grassland, although apparently uniform in habitat, is said to be so simply because the dominant physiognomic plants occupying it show no outward response to any change of habitat. That the habitat occupied by the montane tussock grassland varies considerably is shown by the behaviour of introduced plants. Thus in certain places the sweetbrier (Rosa rubiginosa) is a tall shrub many feet in height, while in others the individuals of the same race remain as small shrubs not more than 3 ft. high at the outside. In the Cass neighbourhood the great variation in the development of cat's-ear (Hypochoeris radicata L.) is most noticeable, and if these variations are looked upon as environmental they indicate considerable differences in the habitat.
Another feature with regard to montane tussock grassland is the small amount of seasonal variation which occurs in the general appearance
of the formation. The colour of the tussock is almost invariable during the whole year, and there are no periods of specially rapid growth. This latter, of course, is partly due to the fact that the leaves are long-lived and do not die off each year, so that there does not seem to be any special season for the maturing of the foliage. This almost absolute uniformness of the general appearance of the tussock grassland is one of its most striking features, and sharply marks it off from many other types of grassland in New Zealand.
It has been previously shown that the elements of montane tussock grassland are at most only sparingly grazed upon. It is thus really not peculiar that the dominant physiognomic plants should have retained their position in the formation. In grasses it does not appear unusual that the species least eaten are the most likely to increase. Thus in the pumice soil of the Volcanic Plateau sowings composed of about equal quantities of cocksfoot and fiorin (Agrostis stolonifera L.) become at the end of a few years almost pure fiorin pastures. In this case the cocksfoot is kept eaten down, while the fiorin is rejected. In other cases, however, the grass fed on attains the mastery over that not touched, as is seen in artificially induced pastures of one or other of the forms of Danthonia pilosa R. Br., where originally the lowland tussock was the more important constituent. In such cases, however, the palatable plant that increases must be better fitted for the conditions than are the species which it displaces.
Before the advent of pastoral occupation, there is no doubt that many areas which are now typical montane tussock grassland were occupied with associations that were gradually turning in course of time into ordinary tussock association. Thus, for instance, Discaria thickets were probably more numerous than at present, occupying young consolidated fans and other features of the land-surface that were of comparatively recent origin. Burning has had the effect of more or less eliminating this scrub, and has induced the climax associations of tussock grassland to become developed more rapidly than would have otherwise been the case.
In the neighbourhood of Cass the main feature of the grassland is the very large amount of Poa Colensoi. I am inclined to think that this grass was not particularly important in the primitive vegetation, but has increased enormously since the advent of pastoral operations. Its prevalence is especially noticeable on areas formed of material comparatively recently water-transported, such as fans, young river-terraces, and the like. On the hillsides, on the other hand, Festuca novaezealandiae is easily dominant, and the blue tussock (Poa Colensoi) is quite a subsidiary element of the vegetation. The last-named grass also appears to be on the increase where burning has been extensively practised. Being smaller than the fescue tussock, it is probably less affected by summer burns than is the taller grass. A notable feature near Cass was its generally uneaten appearance, which was certainly indicative that this grass is not favoured by stock. Of course, it must be recognized that Poa Colensoi is an aggregate species, and it is possible that certain forms are more palatable to stock than are others. Another characteristic feature of the Cass tussock-land is the almost complete absence of the true blue grass, Aqropyron scabrum. In general, I should say that in the upper Waimakariri river-basin the main effect of pastoral operations on the indigenous vegetation has been the more general domination of the tussock growth-form element in the tussock grassland and the reduction in frequency of occurrence of shrubby plants, due to
burning, and of certain other shrubby elements, such as the tall species of Carmichaelia, due to combined burning and grazing. The scarcity of Agropyron scabrum is peculiar, and due either to its having been eaten out or not ever having been an important element of the formation. Over certain areas the injurious effects of summer burns on the fescue tussock are notable, but there is no appearance in general of any opening-up of the grassland and the production of steppe. Unlike what happens on lowland tussock grassland, no invasion with Danthonia pilosa has occurred. Certainly a few plants of both that species and D. semiannularis are to be seen, but there is no appearance of that replacement of the tussock growth-form by this genus which is so noticeable and characteristic of much lowland tussock grassland in both the main islands of New Zealand.
6 Deterioration in Carrying-capacity.
It is generally accepted that the carrying-capacity of the montane tussock grasslands has seriously deteriorated since they were first brought under occupation. From an examination of the sheep returns covering a considerable period it is evident that deterioration is not a general feature, but is confined to certain special areas. So far as the upper Waimakariri river-basin is concerned, the figures for the four main sheep-stations during the past thirty-five years are as follows:—
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
|Name of Station||1879||1889.||1899.||1909.||1914.|
These figures show that the stock carried thirty-five years ago and to-day is approximately the same, but that during the past six years a considerable decrease has taken place It will be noticed, however, that the carrying-capacity of the two smaller stations has throughout remained much the same. On all these stations the winter country is montane tussock grassland, but they also possess large areas of summer country.
Thus, so far as the upper Waimakariri area is concerned, it is hardly correct to say that the grazing-land has seriously deteriorated, as it is quite possible that the low figures for 1913 and 1914 may be improved again in a year or two, as has been the case in the past when a diminution in the flocks has been recorded.
For purposes of comparison it is perhaps fairer to take the stock in a whole sheep district for a number of years. As the Mackenzie County sheep district is one that is frequently quoted as showing serious deterioration in the carrying-capacity of its tussock grassland, the
[Footnote] * These figures are for 1898, the 1899 ones being just under 5,000, but the reduction is due to excessive mortality.
[Footnote] † 1913 figures. Those for 1914 show a decrease to 24,000, but this is only temporary, as the run is understocked through both sales and winter losses.
following figures are instructive (all the low tussock grassland of this area can be classed as montane):—
Here again it is seen that thirty years' continuous grazing has not lessened the carrying-capacity of the whole area. Nevertheless there is a very large extent of country in this sheep district where the majority of the tussocks have died out, and considerable stretches of land that were formerly typical montane tussock-land are now virtual desert, with patches or circular low flat cushions of Raoulia lutescens as the dominant physiognomic plant. From this it would certainly appear as if the montane tussock-land was not the important grazing association of the area. It is commonly asserted that if only the country could be restored to the condition it was in forty years ago the amount of stock carried would be vastly increased. Yet in the Mackenzie sheep district the destruction of much of the montane tussock has not resulted in diminution in the aggregate numbers of sheep carried. In fact, thirty years ago in that district there were 70,000 fewer sheep than there are to-day. When the figures for Vincent County (Central Otago) are examined it will be seen that serious deterioration in carrying-capacity has occurred. In 1879 this county pastured over 490,000 sheep, while in 1914 the flocks numbered only 330,000, showing a decrease of over 160,000 sheep. In Vincent County almost the whole of the montane tussock grassland association has been destroyed, and its place taken by an almost desert vegetation. To show how seriously the carrying-capacity has been influenced in parts of the Vincent County the case of Galloway Station may be mentioned. In 1879 the number of stock pastured was approximately 70,000, but to-day the number carried on the same area is a trifle over 20,000.
With regard to Vincent County in general, two factors which have not been in operation in the upper Waimakariri river-basin must be recognized. These are a very low rainfall and a superabundance of rabbits from the early “eighties” onwards. The system of sheep-farming in Vincent County and in the upper Waimakariri has been exactly similar, and extensive burning of the tussock grassland a noticeable feature of the management in both localities. In Vincent County extensive and repeated burning of the tussock, coupled with the low rainfall (less than 15 in per annum at Galloway) and the continued presence of rabbits in large numbers, has virtually destroyed the montane tussock grassland vegetation. On the other hand, the same system of management in the upper Waimakariri has in the presence of a fair rainfall (over 30 in. per annum, and higher in the west) and in the absence of rabbits resulted in comparatively no deterioration in carrying-capacity until after 1909. Since that date the number carried has fallen considerably, but this is due to excessive winter losses, and not to the deterioration of the vegetation. When it is considered that the Waimakariri
river-basin has been continually utilized for sheep-grazing for over half a century, and that comparatively nothing effective has been done in the way of intentional sowing of grasses, &c., to improve the feeding-quality, it is remarkable that the carrying-capacity should have been maintained. From this it would appear that in areas of fair rainfall, provided rabbits are not present, the montane tussock grassland will retain its normal comparatively low carrying-capacity for an indefinite period. If, however, any attempt at overstocking is resorted to, the carrying-capacity becomes lessened; but after being stocked for a few years below the average the carrying-capacity again becomes normal.
7. The Rival Theories of Burning.
In the early times of the utilization of the montane tussock grassland it was recognized that the dominant fescue tussock, when in its natural state, afforded but scant feed. Accordingly the practice of burning off the tops of the tussocks each year was resorted to in order to stimulate a fresh young growth that would be readily fed off by sheep. This practice of burning was general from the “sixties” onwards, being carried out at all times of year, including midsummer. After a while it was decided that summer burning had an injurious effect, and this practice was abandoned, but autumn and spring burning still remained popular, and was generally carried out. During the past decade the utility of burning at all has been largely questioned, and at present the montane tussock-land runholders are divided into two distinct schools, one asserting the necessity and the other the fallacy of burning. The arguments adduced by both sides have not been subjected to scientific experimental investigation, so that the truth or otherwise of the premises laid down by both burners and anti-burners has never been accurately determined.
The premises on which the two schools base all their arguments may be summarized as follows:—
(A.) Arguments for Burning.
(1.) The tussocks in their natural state afford no feed for stock, the young growth being so protected by the older inedible leaves that it cannot be grazed off.
(2.) The burning results in the production of succulent fresh green herbage readily eaten by sheep.
(3.) Non-burning results in the too rank growth of the tussocks. This causes the leaves of adjacent tussocks to almost completely cover the ground, and increases the difficulty of grazing the areas between the tussocks.
(4.) Burning in early spring and in early autumn does not kill out the tussocks.
(5.) The destruction of tussocks over wide areas can generally be traced to summer burning, a practice now universally rejected.
(B.) Arguments against Burning.
(1.) The burning of tussocks results in their gradual weakening, and final death.
(2.) The continued healthy development of the tussock growth-form as the dominant feature of the vegetation is essential for the welfare
of the other elements of the association. Any weakening and killing-out of the tussocks leads to the general destruction of the association, and its replacement by a vegetation of infinitely worse feeding-value.
(3.) The growth resulting from the burning of the tussocks is capable of yielding feed only for a brief period, as burnt tussocks, even when grazed soon after burning, rapidly reassume their tussocky condition.
(4.) Burning lessens the amount of natural seeding, and this leads to the rapid creation of bare ground.
The evidence on which the anti-burners base their claims is on the wide extent of country, more particularly in Central Otago, where the gradual disappearance of the tussock has been followed by the elimination of the whole of the association and the production of a virtual desert type of vegetation quite useless for grazing purposes. The proburners, on the other hand, assert that many stations which do not burn, although they keep the tussock grassland in an apparently unimpaired condition, cannot keep their stock in as good a condition as when burning is carried out. Again, with regard to Central Otago, it is urged that the rabbit factor has played the essential part in the destruction of the vegetation, and this supposition is probably in the main quite correct.
8. The Future of Montane Tussock Grassland.
It is difficult to forecast the future of montane tussock grassland From present appearances, however, it seems likely that the greater part of the area occupied by this formation is capable of remaining permanently in much the same condition as it is to-day. In other words, it is likely to remain inferior sheep-grazing country, capable of supporting at most one sheep on 3 to 5 acres. On other portions, where both soil and climatic conditions are adverse, a gradual deterioration in carrying-capacity will be experienced, provided special efforts are not made to modify these conditions. Their modification by manuring, cultivation, shelter-tree planting, and other methods is quite possible, but, generally speaking, impracticable from the expense standpoint. The limited experimentation carried out by the Department of Agriculture has all been in the direction of showing the impracticable nature of such work. Other areas, again, where the soil and climatic conditions are good, will probably in time, when great reduction in the size of individual holdings takes place, be converted into better-class grazing-land through cultivation and other farming operations. The production of special crops, more particularly lucerne and also root crops,* may also play an important part in the future. The application of such methods would have a very important bearing on the tussock grassland as a whole. The increased production of feed over certain areas would enable periodical spelling of much of the land without the necessity for reducing the total carrying-capacity.
One point is, however, of great importance, and this is that the present vegetation appears to be specially attuned to the conditions, and this vegetation is of an extremely xerophytic nature. There must be some very powerful factors that have led to the development of such a vegetation, and with these still in operation it seems unreasonable to
[Footnote] * There is a prevalent opinion amongst runholders that sheep grazed on montane tussock grassland refuse to feed on root crops.
expect that ordinary grassland of a more mesophytic type is likely to be produced by artificial means. It is, however, possible that certain grasses that one might term facultative xerophytes, such as certain forms of Danthonia pilosa, might become in time important consituents of the montane tussock grassland. When conditions are favourable Danthonia pilosa is distinctly a mesophytic grass, with broad flat green leaves; but when conditions are adverse they dry and roll up, fresh green succulent herbage being again produced on the advent of more congenial conditions. If Danthonia pilosa would spread over the montane grassland, and become an important constituent of the vegetation, a great increase in carrying-capacity would be secured.
Spelling the ground during the seeding season has often been advocated, and the increased carrying-capacity over certain areas that has followed understocking for some years seems to indicate that such a procedure would be productive of good results. Against this has to be reckoned the fact that much of the montane tussock grassland has already for many years past been more or less unstocked during the late summer and autumn, when the flocks are mainly located on the higher summer country. Again, the special spelling of definite areas during definite periods would entail a very large expenditure in fencing.
It has been calculated that over one-seventh of the occupied land of New Zealand is composed of montane tussock grassland, from which, roughly, 2 ½ lb. of wool is produced per acre each year. A certain number of store sheep are also disposed of from this land, but the number is considerably less than is generally thought. On this huge area the average gross returns are far less than on any other of the occupied lands, and the adoption of any methods which will increase the turnover would be of far-reaching importance. In order to determine if any methods can be adopted in this direction, a complete investigation of the vegetation with respect to sheep-grazing is necessary, and should precede any definitely experimental work on the improvement of the carrying-capacity of the land.
The Canterbury College Mountain Biological Station offers exceptional facilities for this all-important research. With the aid of a few hurdles, some sheep, and proper scientific observation much could be accomplished. When it is said that even after sixty years' continuous occupation of the ground for sheep-grazing comparatively no accurate knowledge is available as to what plants are really furnishing the bulk of the feed, the need for a thorough investigation of the vegetation from the economic standpoint becomes apparent. It is safe to say that until such time as this has been done any statements as to the future of the montane tussock grassland are largely a matter of pure speculation.