A. Natural regeneration (NR) from seed
When regeneration obtained from seed forms a crop, it is called a seedling crop. It is neither planted nor of coppice or root-sucker origin but originating in situ from natural regeneration. When this seedling crop grows into a forest, it is called a high forest. NR from seed depends on the followings:
- Seed Production: The most important consideration for natural regeneration from seed is the production of adequate amount of fertile seeds by the trees of the area or in the vicinity. The production of seed depends on the following: species, age of trees, size of crown, climate, and other external factors.
- Seed Dispersal: The seed produced by the trees is dispersed by the agency of wind, water, gravity, birds and animals. Some examples of seed dispersal by various agencies are given below:
- Wind: Conifers, Acer, Betula, Populus, Alnus , Salix, Terminalia, Dalbergia, Acacia , Adina , Bombax, etc.
- Water: Most mangrove species, Dalbergia, Teak, etc.
- Birds: Prunus, Mulberry, Diospyrus, etc.
- Animals: Acaica arabica, Prosopssis juliflora, Zizyphus, Anthocephallus, etc.
- Gravity: Oak, Juglans, Asculus, etc.
- Seed Germination: After dispersal, insects, birds and rodents destroy a lot of seeds. The others germinate provided they are deposited on suitable soil. Germination of seeds depends upon several internal and external factors listed below:
- Internal Factors: Permeability to water, permeability to O2, development of embryo ( i.e., Fraxinus floribunda takes one year), after ripening (i.e., Juniperus macropoda), viability of seeds, size of seeds, germination capacity, germination energy
- External factors: Moisture, air, temperature, light (i.e., Cassia fistula or Albizzia procera requires light), seed Bed.
- Seedling Establishment: Even if germination is good, it does not mean that natural regeneration would be good because a large number of seedlings die at the end of rains or as a result of frost during winter or drought during summer. In addition, there may be other factors such as weeds, grazing, fire, which may kill the seedlings. Thus, establishment is defined as the development of new crop ‘naturally or assisted’ to a stage when the young regeneration ‘natural or artificial’ is considered safe from normal adverse influences and no longer needs special protection or tending operation other than cleaning, thinning and pruning. The following factors affect establishment of seedlings:
- Development of roots
- Soil conditions – Moisture, Aeration, Nutrients
- Other Climatic Factors- high or low temp.
- Drip (Slash erosion)
- Condition of grasses and other competing weeds
- Grazing, Browsing and Fire
- Composition of the crop
B. Natural regeneration from vegetative parts
When regeneration obtained by coppice forms a crop, it is called coppice crop and when it develops into a forest, it is called coppice forest to differentiate it from the high forest.
Natural regeneration by coppice can be obtained either by:
- Seedling coppice: Coppice shoots arising from the base of seedlings that have been cut or burnt back. This method of obtaining natural regeneration is used for cutting back woody shoots and established reproduction which is not making any progress so that they may produce vigorous shoots and soon develop into saplings.
- Stool coppice: Coppice arising from the stool or a living stump of a tree is called stool coppice. In this method, regeneration is obtained from the shoots arising from the adventitious buds of the stump of felled trees. The coppice shoots generally arise either from near the base of the stump or from its top. The shoots arising from near the top of the stump are liable to be damaged by the rotting of the upper portion of the stump as well as by wind, etc.
Vegetative reproduction can be obtained by any of the following methods:
- Coppice: Vegetative reproduction in which the tree, plants or the seedlings of a species when cut near the ground level produce shoots.
- Root Sucker (A shoot rising from the root of a woody plant): Vegetative reproduction in which a root of a plant is partially or wholly cut to produce a shoot called root sucker.
- Cutting: Vegetative propagation in which a portion of the stem, branch or root is placed in the soil or other medium, in order that it may develop into a plant. Depending on the part of the plant used, cuttings may be classified into stem cutting, branch cutting, root cutting and root and shoot cutting. Root and shoot cutting is a young plant with pruned taproot and severed stem used for planting.
- Layering: Inducing development of roots on branches while they are still attached to the trees is called layering. Layering may be done in soil or in air and so layering is of two kinds: air Layering and soil Layering
- Grafting: Vegetative propagation in which a portion called scion (any unrooted portion of a plant used for grafting or budding on a rooted stock), of one plant is applied to stock (a rooted plant on which a scion is grafted), usually rooted, which is another plant, with the object of securing vegetative union between the two, when the scion is detached from the parent plant and the shoot of the other plant is severed, to produce a new plant to be planted out. Attempt is made to transport the scions to the grafting place within 24 hours.
- Budding: A vegetative reproduction in which, a bud with some portion of the bark of a genetically superior plant is grafted on an inferior plant so that it can produce shoot when the old shoot of the stock is cut off. Bud is grafted on the stock in the form of a patch after removing the bark of the stock in that portion or by making an incision in the bark of the stock in the form of T and then fixing the scion inside it.