in Sri Lanka - Ministry of Environment

the soil solution and the insolubility of soil minerals such as iron, phosphorus and magnesiumare given as reasons for the formation of edaphic climaxes. These could be artifacts ofimpenetrable ‘C’ horizon in the soil profile and subsequent water logging during wet conditionsand bad aeration (Sezchowycz, 1954). These are mainly dominated with Imperata cylindricaand Cymbopogon nardus but the presence of scattered or clumped trees (e.g. M. hexandra,Limonia acidissima) is a salient feature of this ecosystem.Villus found in Wilpaththu National Park, and at the Mahaweli flood plains are a specific natural,grass dominated, wetland ecosystem found in the dry zone of Sri Lanka. Swampy areas invillus are surrounded by seasonally flooded damp grasslands while occasionally flooded drygrasslands are located next to these up to the forest edge.On the other hand, grassland disclimaxes are recorded to have originated after the destructionof forests in the past and subsequent repeated cultivation and accompanying frequent burningand heavy grazing (de Rosayro, 1961; Pemadasa, 1990). Imperata cylindrica is a commonspecies in such grasslands but in some areas, such as Udawalawe National Park, these havebeen replaced by Panicum maximum. Annual herbs such as Croton hirtus, Eleutherantheraruderalis grow with perennials such as Tephrosia purpurea, Abutilon indicum and somePoaceae species and as a result, a clear seasonal variation in the vegetation can be observed.However, Heteropogon contortus may dominate if the grasslands are intensively and annuallyburnt over a long period of time (Perera and Wijesooriya, 2007).B. Prominent plants (families)In Dry forest ecosystemsEuphorbiaceae species are the most prominent in dry forest vegetations and their proportionalabundance is high in areas where more harsh environments exist (Table below). Drypetessepiaria is a universally distributed Euphorbiaceae member which dominates the forestunderstorey. M. hexandra (Sapotaceae) is also a unique species in the dry zone whichdominate in dry areas but the species is either rare or absent in cooler and moist conditions.In comparatively wetter areas, a mixture of Annonaceae, Ebenaceae, Melastomataceae andSapindaceae species tend to grow more frequently with some Euphorbiaceae, Rutaceae orSapotaceae species.The composition of species and plant families in secondary forests do not vary much withthe forest type, their location and the abiotic conditions. At early seral stages, individuals ofEuphorbiaceae (e.g. Flueggea leucopyrus, Figure 6c), Rubiaceae (e.g. Catunaregam spinosa,Tarenna asiatica) and Rhamnaceae (e.g. Ziziphus oenoplia) are prominant but Rubiaceae(e.g. Benkara malabarica, Haldina cordifolia) Tiliaceae (e.g. Diplodiscus verrucosus, Grewiaspp.), Verbenaceae (e.g. Premna spp.) and Sterculiaceae (e.g. Pterospermum suberifolium)species are prominent in late seral forests. Scrub jungle plagioclimaxes contains many speciesthat are common in early seral secondary forests but Fabaceae (e.g. Cassia auriculata, Figure6a; Dichrostachys cinerea, Figure 6b), Euphorbiaceae (e.g. Flueggea leucopyrus, Figure 6c)and Rhamnaceae species dominate in them.168