Normally when searching for epiphyte news I do a google scholar search for papers published in 2013 or 2014. This time I entered 1940 and came up with this interesting piece from 1942 by George Simpson and John Scott Thomas. Amongst notes on a range of species are the following accounts of Metrosideros diffusa (white climbing rata) and Metrosideros robusta (northern rata).
1940's science!
Metrosideros diffusa
The juvenile, whether terrestrial or climbing, pushes out wiry roots from closely-place nodes; adult flowering branches are shrubby divaricating laterals from the ascending stems.
This is a very succinct description of the difference between the climbing, host-hugging juvenile and the cloud-shaped, highly-branched adult stems that form when they reach the sun.
The juvenile, whether terrestrial or climbing, pushes out wiry roots from closely-place nodes; adult flowering branches are shrubby divaricating laterals from the ascending stems.
This is a very succinct description of the difference between the climbing, host-hugging juvenile and the cloud-shaped, highly-branched adult stems that form when they reach the sun.
Metrosideros diffusa. Photo: Tony Foster.
Metrosideros robusta
Zotov (1939, p.275) disputes the theory of Kirk (1889, p.263) that the coalescence of the decending stems and lateral binders of this epiphyte imprisons and destroys forest trees.
He states that he has not found evidence of strangulation, and he maintains that the "light demanding" host is destroyed by the intensity of shade thrown by the faster-growing epiphyte.
Other observers have suggested to us that root competition may be the destructive agent or a soil reaction set up by the closely matted fibrous roots.
Kirk (loc. cit.) states that puriri (Vitex lucens), to increase its girth, bursts apart the stems of the epiphyte and, if this be accepted, shade can have but little effect on that species.
A shade maximum is reached when the epiphyte slightly overreaches the crown of its host, yet the host lives through this crucial period and survives while the epiphyte develops large spreading branches with a high open crown affording a sufficiency of light, more than most trees offer to much of their foliage.
Its fascinating that our understanding of the effect that Northern rata has on its hosts has not advanced a whole lot since 1942. It is still considered that this hemiepiphyte does not strangle its host but either out-lives or maybe shades it out. Interesting that Kirk talked about puriri bursting these Northern rata stems apart - what a sight that would be!
Zotov (1939, p.275) disputes the theory of Kirk (1889, p.263) that the coalescence of the decending stems and lateral binders of this epiphyte imprisons and destroys forest trees.
He states that he has not found evidence of strangulation, and he maintains that the "light demanding" host is destroyed by the intensity of shade thrown by the faster-growing epiphyte.
Other observers have suggested to us that root competition may be the destructive agent or a soil reaction set up by the closely matted fibrous roots.
Kirk (loc. cit.) states that puriri (Vitex lucens), to increase its girth, bursts apart the stems of the epiphyte and, if this be accepted, shade can have but little effect on that species.
A shade maximum is reached when the epiphyte slightly overreaches the crown of its host, yet the host lives through this crucial period and survives while the epiphyte develops large spreading branches with a high open crown affording a sufficiency of light, more than most trees offer to much of their foliage.
Its fascinating that our understanding of the effect that Northern rata has on its hosts has not advanced a whole lot since 1942. It is still considered that this hemiepiphyte does not strangle its host but either out-lives or maybe shades it out. Interesting that Kirk talked about puriri bursting these Northern rata stems apart - what a sight that would be!
Metrosideros robusta roots. Photo: Jon Sullivan
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