EXOTIC AND INDIGENOUS SPECIES:
“The term exotic in forestry lakes a generally accepted definition simply ‘any species grown outside its natural range or distribution” like Eucalyptus spp Populus spp Acacias, Prosopis juliflora, Broussonetia papyrifera, Ailanthus excela, Robinia pseudoacacia and Casuarina equisetifolia.
NEED AND IMPORTANCE OF EXOTICS:
Pakistan is spending a lot of foreign exchange on the import of timber on the import of timber and timber products annually, while the demand for the same is still increasing rapidly with the expansion of wood-based industries and rise in the standard of living. It is therefore imperative, that all its resources are fully exploited to achieve self-sufficiency in forest products. The production can be increased by putting more area under forest and by introducing fast-growing exotic species.
PROPERTIES OF SUCCESSFUL EXOTICS:
Often, however, exotic plantations are formed on open grasslands sandy waste or another tract devoid of the forest, and here their creation is an advantage rather than otherwise, apart from utilitarian considerations.
The exotic trees grown in commercial forests for the production of wood have the following properties:
- their produce is of high value
- their rate of yield is high
In addition to these, exotic trees have the following properties in common:
- An adequate supply of seeds (or cuttings) is available
- They are easy to rise in nurseries.
- They are easy to establish and grow in plantations
- Insects or diseases do not prevent their successful growth
- Information is available on methods of growing them and on their rate of growth and yield.
TRIALS FOR INTRODUCTION OF EXOTICS:
The procedure adopted in Nigeria, Uganda, and Zambia for the introduction of exotic species has been quite successful and is recommended for use in other arid zones.
The Species Elimination Trials
The trial is designed to eliminate from further consideration those species clearly unsuited to the environment of the new planting area.
Species elimination trials in Nigeria have given sufficiently reliable information to eliminate about half the species at a reasonable cost after two years.
The Species Growth Trial
The growth trial provides information on performance, growth rate, stem and crown form, agencies causing injury or death, and crop benefits to be derived from those species emerging successfully from elimination trials.
Growth trials are established on different soil types and different climatic zones of the region.
Species Plantation trials
Comparison of different spacing, fertilizers, cultivation and other Silvicultural treatments should be made on trial plots designed for that purpose. The species, which pass this test and meet the desired purpose, may then be recommended for field planting.
Species Trials in Pakistan and Some Results
The indigenous plant species have evolved through long and continued selection and probably are the best suited to the local environment i.e. in the plain and arid area following species are grown Prosopis spicegera, Salvadora oleoides, Tamarix articulate, Acacia senegal, Zizyphus jujuba and Tecoma undulata
EXOTIC SPECIES RECOMMENDED FOR VARIOUS ZONES:
- Northern Hilly Tract: Populus deltoides, Robinia pseudoacacia.
- Sub-Mountain Range: Eucalyptus tereticornis
- Western Hilly Areas: Populus deltoides, Eucalyptus spp.
- Indus plain: Acacia cyanophylla, A. tortilis, Eucalyptus camaldulensis, Leucaena leucocephala (iple iple), Poplus euramericana.
- Deserts: Acacia aneura, A. tortilis, A. Victoria, Prosopis juliflora, P. cineraria.
- Saline Areas: A. nilotica, A. cyanophylla, E. camaldulensis, E. microtheca, Leucaena leucocephala, Prosopis juliflora.
- Waterlogged Areas: E. camaldulensis, E. robusta.
“An indigenous species is one that grows naturally in the country, concerned though, not necessarily in all parts and certainly not suited to all sites.”
Eg Natural origin of chir is in b/w 3000 ft to 6000ft altitude.
Advantages of Indigenous Species:
- The growth of natural stands provides some indication of possible performance in plantation
- The species is adapted to the environment and already filling and ecological niche.
- I. Species, even in monoculture are generally considered more ecologically valuable than exotics for the conservation of native fauna and flora.
- The timber is likely to be known to local wood-using industries.
For these reasons, if and indigenous spp grows well in a plantation on the sites for afforestation, there is no compelling reason to widen the choice.
Image: (Exotic) Eucalyptus Spp linear plantation in Naseerabad District Balochistan. The main objective to combat salinity and waterlogging and to reduce impacts of hot-winds | February 3, 2018 | Image by Author.
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