RIVER erosion

Evening Post, Volume CXXV, Issue 110, 12 May 1938, Page 8

RIVER erosion

ALDER PROTECTION

STATE FORESTRY VIEWS

A reply had been received from the Director of Forestry (Mr. A. D. McGavock), in reply to. a letter from the Wellington Acclimatisation Society asking for advice regarding the suitability of after trees to counteract river erosion, said the chairman (Dr. G F. V. Anson) at the meeting of the society last night. It stated.— "There are 30 different -species of alder. It is probable that the trees you speak of are common black alders I (Alnus glutinosa), which was until very recently almost the only species planted in New Zealand. This has always been recognised as a tree inhabiting low-lying swampy sites and stream banks. It is, for example, extremely abundant on the banks of the Waikato River from C ambridge downwards. There is no difficulty in propagating the 'tree, although it is practically never seen in local catalogues, owing to the lack'of demand. I "It is, however, very' questionable whether it would be wise to use the species on the banks of any of the major rivers, owing to its free seeding habits. Enormous quantities of freely visible seed are shed into the water, germinate there, and take root wherever they are lodged by the current. The tree also cappices freely when cut back and so is hard to eradicate if, at some future date, it is fouad to be creating downstream obstacles by its seedlings." 1 The executive committee had considered the "letter, said: Dr. .toisoru, and recommended that the plarfting of the tree Should be fully considered. It might be advisable Ho obtain cuttings. The only objection to it by the Forestry Department was in regard to the larger rivers. Mr. D. G. Gibbs: If it is put into the tributaries it will get'into the main streams. Mr. A. Seed said that he had discussed its planting with an officer of the Forestry Department, who had pointed out that the only difficulty was the seed being .deposited on sandbanks and islands in rivers. It would be cheaper for the river boards, perhaps, to remove seedlings from unwanted positions than to go to the expense of groynes and other protective works, which the planting of alders would obviate.

The matter was clearly arousing interest, said the chairman, as he had personally received several letters. ■ • The State Forestry Service had sold a lot of it for poles, as the wood was very durable in wet ground, said Mr. Seed. It would be necessary *o make a survey of the society's district, said Dr. Anson, and decide whether to concentrate on certain streams or introduce the tree generally. Streams sucn as the Maungaterera in the Wairarapa would be most suitable. It was decided to write asking the country sub-committees to reply naming suitable streams in their districts, and what assistance could be relied on these committees in planting areas i agreed upoa,