158 Transactions. 



regular sheep-feed on the montane tussock grassland is badly needed, 

 and for this purpose the fencing-off and feeding-o£f of small areas is 

 necessary. 



5. Changes in the Vegetation. 



It is impossible to describe accurately the analytical composition of 

 really j^rimitive 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 aj^preciable 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 forma- 

 tion 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 elimi- 

 nated profound alteration has occurred. This has resulted in the pro- 

 duction of a totally different formation, approaching the desert type. 

 Whether or not this new vegetation is a stable jDermanent 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 condi- 

 tions 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 eco- 

 logically. 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 comjilet© 

 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, how- 

 ever, 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 pro- 

 duced. The production of steppe from tussock grassland has not, 

 however, taken jilace 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 associa- 

 tions took place. It is generally said that the effect of stock has been 

 to reduce very largely what runholders call " the better and finer 



