POPULATION STRUCTURE AND REGENERATION OF DALBERGIA LATIFOLIA ROXB. AND D.SISSOIDES WIGHT & ARN. IN KERALA AND TAMIL NADU, INDIA

Abstract

Dalbergia latifolia Roxb. and D.sissoides Wight & Arn. are the two important precious 
timber tree species of India. D. latifolia is distributed in many parts of the country from the 
sub-Himalayan tract to Southern India, whereas D.sissoides has a restricted distribution in the 
Western Ghats, from the hills of Karnataka southwards to Pulneys and Kerala. Of late, the 
populations of D. latifolia and D.sissoides have been dwindling considerably in the forest 
areas and D.latifolia has been categorised as “Vulnerable” in the Red Data book of IUCN. 
The study on regeneration of forest trees has important implications for the management of forest 
genetic resources, especially that of precious timber species like D.latifolia and D.sissoides. In 
this context, a study was undertaken during 2011 to 2017 in the forest areas of two States -
Kerala and Tamil Nadu to assess the natural regeneration and population structure, so as to 
determine the status of these species, so that suitable managerial interventions could be made 
to conserve them. Out of 14 Forest Divisions of Kerala surveyed, natural regeneration of 
D.latifolia was found to be good in only six divisions viz. Thrissur, Kannur, Munnar,
Malayattoor, Nilambur South and Nemmara. In rest of the eight divisions, saplings were not 
recorded and only seedlings were available. Of the seven Forest Divisions of Tamil Nadu 
studied, D.latifolia was recorded in six divisions. Salem division exhibited good regeneration, 
whereas it was fair in Erode, Coimbatore and Tirunelveli divisions and there was no 
regeneration in Theni and Dharmapuri divisions. Presence of D.sissoides was recorded in 
only seven divisions of Kerala and among them in five divisions viz. South Wayanad, 
Chalakudy, Thrissur, Palakkad and Munnar there was no regeneration. In Mannarkad and 
Nemmara divisions, only seedlings were present and saplings were totally absent. Among the 
seven forest divisions surveyed in Tamil Nadu, there was no regeneration of D.sissoides in 
Coimbatore, Theni and Tirunelveli divisions. Saplings were not recorded in Gudalur division 
and only seedlings were available. Thus, overall natural regeneration of D.sissoides in both 
the States was found to be in an “alarming” situation. The girth class-wise population of 
D.latifolia trees in Kerala revealed that nine divisions namely Mannarkad, Chalakudy, South 
Wayanad, North Wayanad, Kannur, Malayattoor, Munnar, Ranni and Thiruvananthapuram 
had healthy population structure and the rest of the five divisions viz. Palakkad, Nemmara, 
Nilambur South, Konni and Thrissur had unhealthy population structure. In Tamil Nadu, 
D.latifolia populations of Coimbatore, Erode and Theni divisions were of healthy nature, 
while other divisions like Salem, Dharmapuri and Tirunelveli did not have healthy 
populations. The population structure of D.sissoides occurring in Mannarkad and Nemmara 
divisions of Kerala was found to be healthy, while in rest of the five divisions like 
Chalakudy, Thrissur, Palakkad, South Wayanad and Munnar, it was not of healthy nature. 
D.sissoides in Theni and Gudalur divisions of Tamil Nadu had more or less healthy populations, whereas Coimbatore and Tirunelveli division did not have healthy population 
structure. The overall population structure of Dalbergias showed that the contribution of 
seedlings to the population of saplings and trees was very poor. The seedling and sapling
stages were much vulnerable to the impact of fire, grazing and weed competition. An 
enumeration of the important tree associates of both the species revealed that they have 
species association characteristic to the respective forest types which harbour them. The 
present population structure of both the species in Kerala and Tamil Nadu has indicated that 
they are likely to encounter severe threat in future due to various biotic and abiotic factors, 
including the climate change, if timely managerial interventions are not made. Therefore, 
both the species should be prioritized as important “Forest Genetic Resources” and get the 
required attention for in-situ and ex-situ conservation. Artificial regeneration of these species 
has also to be taken up so as to augment the declining population in the natural forests.