TUSSOCK LAND IN NEW ZEALAND

Southland Times, Issue 23793, 15 April 1939, Page 19

TUSSOCK LAND IN NEW ZEALAND

DETERIORATION OF COUNTRY SURVEY OF SOUTH ISLAND AREAS The deterioration of tussock country forms the subject of a preliminary report by the Department of Scientific and Industrial Research. The report states that whether the changes in the vegetation since the early days of colonization have been brought about unwittingly or otherwise their pro-, gress from year to year is too slow to be observed. Ever on an increasing scale valuable pastures and soil are being lost, and valuable plains are becoming more and more subject to flood hazards.

The steadily falling sheep-carrying capacity of the tussock pastures has been a source of worry to run holders for some time and has become of serious national concern. As long ago as 1865, Buchanan, a noted naturalist of the day, observed the ominous signs of deterioration of the land and warned against the practices then in vogue, the pastoral practices which, in fact, continue almost unchanged to the present day. Last summer MrV. D. Zotov, of the Botany Division, Plant Research Bureau, Department of Scientific and Industrial Research made a survey of the tussock grasslands as a preliminary investigation for further research into the problems of deterioration and improvement of the pastoral lands. The results of the findings have just been published in Bulletin 73 of the Department of Scientific and Industrial Research, “Survey of the Tussockgrasslands of the South Island.” Although the bulletin is necessarily somewhat technical, it contains much of general interest to practical men, while numerous well-selected illustrations give striking evidence of the changes that are taking place, states The Press. VEGETATION RECONSTRUCTION

An attempt is made in the first instance to reconstruct the vegetation as far as possible in its original state. As the result of this, the whole of the tussock country is classified into the drier or the natural grasslands which are natural under the prevailing conditions of rainfall, and include most of Otago and Canterbury below an elevation of 2500 ft and the wetter or induced grasslands which were originally under forest but consisted of tussock grasses at the time of European settlement. These extended throughout the remaining country up to an altitude of 4000 feet. There were no barren or semi-barren lands as are now to be seen in the hills of Canterbury or the depleted “scab-weed” area of Central Otago. CLASSES OF DEPLETION The process of depletion was found to be more or less strongly manifested throughout the tussock country. The most serious cause of depletion is periodic burning followed by grazing on the flush of young growth. This practice tends temporarily to raise carrying capacity to its maximum and results in overstocking and this is inevitably followed by depletion and decline in carrying capacity. Of course, invasion by rabbits has aggravated the situation. Mr Zotov, however, produces evidence to show that the multiplication of rabbits was favoured by the depletion initiated by the malpractices of burning and overstocking. The role of the tussock, especially in the drier parts, is discussed at some length. It is considered that the hard tussock is an essential constituent of the tussock grasslands pastures in that it is this species which reduces winddrying and otherwise shelters the shorter and more palatable species. Mr Zotov also believes, in view of the peculiar climatic conditions prevailing that reliance must be placed mainly, if not entirely, on our native species for improvement of pastures. Among various species, he recommends trials with blue-grass, but he gives a warning that there are varieties to be encountered which would suit one locality admirably and yet fail in another. EROSION LOSSES Hand in hand with depletion goes erosion. The fact is not generally appreciated that the erosion in the tussock country is already assuming great proportions. Water erosion in the form of gullying and sheet erosion is very active throughout, despite the fact that the rainfall there is rather low. Exposed hillsides, especially . in Otago, are now stripped of their soil. On the higher country of Canterbury, tens of thousands of acres have their top soil already buried under stony debris due to frost action on the ground now devoid of vegetation. Whatever may be the interpretation, the fact remains that soil is being lost rapidly on a big scale, and this is indeed a serious national loss.