Deciduous Forests

Based on the moisture regime, moist deciduous forests are divided into primary/climax or secondary moist deciduous forests.  The primary moist deciduous forests generally occupy the rainfall zone of 1500 to 1800 mm, as a transition between wet evergreen and dry deciduous forests.  The secondary moist deciduous forests occur within the potential area of wet evergreen formations, where the rainfall is more than 2000 mm.  Although the floristic composition is almost similar in both the types, the relative dominance of certain species varies.

Secondary Dry Deciduous Forests

These are inferior climax forests predominated by poorly shaped, small sized trees.  Sandal is also seen in such forests.

Distribution: They are seen distributed in dry deciduous forests and intruding into the drier parts of moist deciduous forests. 

Locality Factors: The soil surface is hard and impervious due to exposure and trampling effected by heavy grazing, fuel and timber collection. 

Floristic: Top canopy trees – Bombax ceiba, Grewia tiliaefolia, Schleichera oleosa, Tectona grandis

Second storey – Feronia limonia, Santalum album Shrubs – Dodonaea viscosa, Lantana camara

Southern Dry Deciduous Forests

The sub group differs from the dry teak forest species-wise, though typical plants like Boswellia are conspicuous.  Heavy grazing invigorates growth of thorny species.  Bamboo is mostly absent and of poor quality, if present.  Climbers are rarely seen.

Distribution: It occurs throughout peninsular India, especially in drier localities.

Locality factors:  The rainfall varies from 875 mm –1125mm on dry sites and soils.  The shallow soiled, well-drained hillsides and the undulating grounds have identical forests, making it difficult to establish the relation of site and climate to the forest in situ. 

Floristic: Diospyros tomentosa, Chloroxylon swietenia, Hardwickia binata, Boswellia serrata

Primary moist deciduous forests (Lagerstroemia microcarpa – Tectona grandis – Dillenia pentagyna type – LTD)

Primary deciduous forests are found in isolated patches between the Anamalai and Wayanad plateaus.  Denser part of this type is the form of woodland and savanna woodland.  Dillenia pentagyna and Tabernaemontana heyneana are characteristic species of this type.  Lagerstroemia microcarpa and Tectona grandis, together with other species such as Anogeissus latifolia, Dalbergia paniculata, Pterocarpus marsupium, Terminalia paniculata, Hymenodictyon excelsum, Haldina cordifolia are common.

Secondary moist deciduous forests:

In kerala secondary forests cover larger areas than the primary type, mostly in the form of dense forests and woodland to savanna woodland.  Especially on the steep slopes, they are found as tree savanna. Floristically, there are similar to primary moist deciduous however, some deciduous species like Dillenia pentagyna, Tabernaemontana heyneana, Strychnos nux-vomica, and Xylia xylocarpa, are relatively more common than in the primary forests.  Tectona grandis, which is extensively planted, has also been found mixed with other species in dense formations.  In the dense forests often there is dominance of  evergreen species like Ixora brachiata, Olea dioica, Persea macrantha, Dimocarpus longan, Flacourtia montana etc.

Dry Deciduous forests

With in the given rainfall regime, dry deciduous forests in Kerala State are rare.  They are confined to northern slope of Anamalai in Chinnar Wild life Sanctuary, eastern part of Mannarkad Division, and South Wayanad Wildlife Sanctuary where the rainfall is less than 1200 mm. The physiognomic structure of these dry deciduous forests is highly variable, due to impoverishment of soil, especially on steep slopes, and also due to anthropogenic pressures including fire and grazing.  Three types of dry deciduous forests have been recognized.

Albizia amara –Acacia spp. Gyrocarpus asiaticus type (AAG)

This type is found only in Chinnar Wild life Sanctuary, up to 650 m.  On the lower slopes, Acacia chundra and A.leucophloea are characteristic species, particularly in the scrub woodland and thickets.  Albizia amara, Erythroxylum monogynum, Dichrostachys cinerea and Chloroxylon swietenia, and Hardwickia binata are the other common species of this type.

 On the slopes, especially on skeletal soils, tree savannas are the prominent formations.  In such habitat Gyrocarpus asiaticus, with metallic-coloured bark, is the characteristic species, along with other slope-loving species, like Cochlospermum religiosum, Givotia rottleriformis, Sterculia urens and Commiphora caudate.

 Anogeissus latifolia – Pterocarpus marsupium – Terminalia spp. type (APT)

 This type is found above 600 m in Mannarkad Division (northern part) and Chinnar WLS.  As it is generally found on slopes, physiognomy varies from savanna woodland to tree savanna.  Apart from the species mentioned in this type Dalbergia paniculata, D.latifolia, Emblica officinalis, Kydia calycina and Grewia tiliifolia are also common. 

Anogeissus latifolia – Tectona grandis – Terminalia spp.type (ATT) 

This type is found only in the South Wayanad WLS. It is generally represented by dense  forest and woodland to savanna woodland.  Compared to adjacent primary moist deciduous forests, here the species like Dillenia pentagyna, Alstonia scholaris, Callicarpa tomentosa disappear and the species mentioned in the type become dominant.  Other common species include Diospyros melanoxylon, Madhuca latifolia, Emblica officinalis, Lagerstroemia parviflora Careya arborea etc. In some poorly drained low-lying areas Shorea roxburghii become conspicuous.