Hopea odorata Roxb. var. odorata, known locally as ตะเคียน Takien is a member of the family Dipterocarpaceae .
Seed production of some species in the Dipterocarp family can vary greatly between years and a year where large number of trees produce many seed is known as a mast year.
The year 2011 was a mast year for Hopea in Chiang Mai and the Huey Keow Arboretum nursery is growing young trees from locally collected seed.
Ten kilometres to the north at Huey Teng Tao there is a stream with two old Hopea trees. In the past five years I can recall seeing neither seed nor seedlings from these trees despite the fact the environment is suitable for growing Hopeas, until that is, fire comes along. Hopeas have been successfully grown along two of the streams leading into the dam at Huey Teng Tao with Gum Hak Doi Suthep planting nursery raised trees and also seed directly into the moist earth along the stream.
The picture, taken 3rd September 2011, shows young Hopeas growing in the moisture along the stream edges.
Many seedlings were also observed up the slope and a little upstream from the parent tree. Only two old trees from the original Hopea dominated gallery forest remain and apart from this years extraordinary recruitment no other Hopeas are to be found. Of the number which had been planted in recent years and grown well, all were killed by fire in 2010.
Fire is not the only threat to the forest here. Both the remaining old Hopeas now face death from the construction of check dams, by Rotary International of Chiang Mai, which have caused massive erosion .
Urgent work is required to demolish these dams and place stones and sand around the roots of the old trees. This requires that the concrete be manually broken with hammers and extreme care taken ensure Hopea seedlings are not trampled or buried.
The lesson here and also from elswhere in the Doi Suthep-Pui national Park is that check dams do not produce the claimed benefits to the environment. Rather they create erosion, disrupt the natural stream ecology of invertebrates travelling along the stream and divert money and a great deal of well intentioned effort from useful work such as weed control.
At the beginning of August many seedlings were seen growing in sand washed down from upstream.
These have now vanished beneath a new layer of sand washed down in the latest storms and the volume of sand is high because erosion continues unabated around the check dams.
This picture on the left was taken in May when hundreds of seedlings were observed.
Also growing here is Mikania micranthra or Mile-A-Minute. This rampant weed needs to be controlled to prevent destruction of young trees.
The area shown in these photos is of special significance for the study of forest regeneration in Chiang Mai.
As the land is managed by the Thai Army it is to be hoped that the management cooperate with Rotary International, CMU researchers and community volunteers to cordon off this area from destructive trampling, remove the dams, prevent fire and control weeds. We may then have a true Ecotourism site worthy of visiting by people birds and forest animals.