Trees of the Dipterocarpaceae family include giants such as the great Dipterocarpus alatus ( Yang Na ยางนนา ) a tree not native to Chiang Mai, planted along the Chiang Mai Lamphun Rd.
A tree of similar appearance which once dominated the Ping River flood plain is D. turbinatus ( Yang Daeng ยางแดง ). Seed of Yang Daeng can be collected in May near the Queen Sirikit Botanical Garden, the Mok Fah Waterfall on the road to Pai and near the Cave at Chiang Dao.
The year 2011 was what is known as a mast year for these trees and also for the riverine Hopea odorata ( Takien ตะเคียน). In a mast year trees flower profusely together and produce vast amounts of seed. From one ancient Yang Na at Wat Chedi Luang 27,000 seeds were collected and around 10,000 seedlings produced.
Grooves in the bark left by insecte is a distinguishing feature of both Yang Na & Yang Daeng
Dipterocarpus alatus -
seed & leaves
This is not altogether good news however because it leads to over production and planting of an exotic species which, by excluding the planting of local trees, degrades the biodiversity of the region. Large quantities of Yang Na seedlings now stock nurseries as far afield as Nan province 350 km from where the seed was collected in Chiang Mai. Meanwhile areas which once had huge numbers of this tree spreading across the paddy fields from Tak to Ubon Ratchatani need large scale replanting of Yang Na.
Good news, however is that large numbers of Takien are available from government nurseries and if every village temple, school in the northern valleys were to plant a few, in time this would transform our landscapes. What we also may welcome is what appears to be a very poor year for Yang Na seed production while large amounts of seed of Shorea roxburghii are dropping from the many old trees in the grounds of Chiang Mai University.
Shorea roxburghii - seed
Shorea roxburghii - in seed early March 2012
I have seen some trees at Chiang Mai university, large dipterocarps in a row. Some are labelled “Dipterocarpus Alatus” and clearly are, but a few of them appear slightly different, they are smaller, have lower branches and the bark on the branches is darker. I think they may well be Dipterocarpus Terbinatus but I cannot confirm it. I have good photos of the trees and their leaves but I couldn’t find good images on the internet to confirm my suspicions. How can I proceed?
Hello Neil. Very unlikely to be other than D.alatus . Without seed hard to tell according to Gardner there is difference I hairiness of leaves. Where exactly are the trees, I can take a look. There is one only D.turbinatus in the Huai Keow Arboretum, rest are D.alatus. D.obtusifolius is also around.