Natural Regeneration Forestry Lecture 3 PDF

Dr. Gagan Mehta Assistant Professor  The renewal of a forest by some means (e.g. natural or artificial) is known as regenerations.  The regeneration has been defined in a number of ways by several workers.  1) "The renewal of a forest crops by natural or artificial means; a...

Dr. Gagan Mehta Assistant Professor  The renewal of a forest by some means (e.g. natural or artificial) is known as regenerations.  The regeneration has been defined in a number of ways by several workers.  1) "The renewal of a forest crops by natural or artificial means; also the new crop so obtained".  2) Regeneration as, "The renewal by self-sown seed or by vegetative means." It is of two types viz., Natural regeneration and Artificial regeneration. .  There are following methods of regeneration of forest:  A) Natural Regeneration,  B) Artificial regeneration and  C) Natural regeneration supplemented by Planting  The renewal of a forest crop, by self-sown seed, or by coppice or root-suckers, also the crop so obtained or also it can be defined as Reforestation of a stand by natural seeding.  Seedling crop: It is a crop consisting of seedling neither of planted nor of coppice or root sucker but originating in situ from natural forest  I) Natural Regeneration from Seed  II) Natural Regeneration by Coppice  III) Natural Regeneration by Root Suckers  1) Natural Regeneration from Seed: Successful natural regeneration from seed depends upon  Seed production,  Seed dispersal,  Seed germination,  Establishment of seedlings.  Seeds are cultured ovules, which contain the embryo.  Seed production depends upon various factors such as species, age of tree, size of crown and climate.  1. Species: All the species do not seed annually and abundantly.  For eg. Teak, babul(Acacia nilotica), khair (Acacia catechu), sheesham seed every year,  while deodar, fir (Abies pindrow), spruce (Picea smithiana) seed at an interval of years.  2. Age: The age has direct correlation with seed production. Young and over matured trees yield poor quality seeds in meager quantity. The middle aged trees give sufficient and good quality seeds.  3. Size of crown: As a general rule, the bigger the crown, the larger the production of seeds. This is because larger crown enhances more entrapment of solar energy which helps in photosynthesis.  So for selecting seed bearers for natural regeneration, middle-aged mature trees with well developed crown should be selected.  4. Climate: As a general rule, warmer climate favors large seed production. Therefore in hilly areas, trees growing towards lower limit of altitudinal zone produces more seeds than those growing towards upper limit.  Hot dry years are followed by good seed years on an account of increase in photosynthesis.  Other external factors which affect seed production are fire injury, insect attack, girdling. ◦ Injury by fire and insect attack stimulate seed production.  The seed produced by the trees is dispersed by the agency of wind, water, gravity, birds and animals. ◦ By Wind:- Conifers, Acer, Rhododendron, Populus, , Acacia catechu, Casuarina, Bombax ceiba etc. ◦ By water:- Most mangrove species, Dalbergia, Teak etc. ◦ By gravity:- Oak, Juglans regia, Aesculus, etc. ◦ By birds:- Prunus, Mulberry, Diospyros melanoxylon, etc. ◦ ◦ By animals:- Acacia arabica, Prosopis juiflora, Zizyphus, etc.  Germination in plants refers to the process by which a seed begins to sprout and grow into a seedling under the right growing conditions.  Some related terminologies:  Germinative capacity: It is the percentage by number of seeds in a given sample that actually germinate.  Germinative energy: It is the percentage by number of seeds in a given sample that have germinated upto the time when the rate of germination reaches its peak.  Plant percent: It is the percentage by number of seeds in a sample that develop into seedling at the end of first growing season.  Seedling year: It is defined as a year in which a given species produces abundant first year seedling. Species Germinative Plant percent capacity Acacia arbica 50 26 Shorea robusta 80 66 Tectona grandis 50 25 Dalbergia sissoo 90 78 Pinus roxburghii 80 37 Cedrus deodara 65 58 Abies pindrow 13 6  Germination of seed depends upon various ◦ (a) Internal factors (b) External factors (a) Internal factors: (i) Permiability to water: Moisture is very essential for germination; if the seed has a hard coat, it prevents moisture reach in the seed embryo and therefore prevents germination. (ii) Permiablility to oxygen: Oxygen is necessary for germination. Factors which inhibit moisture reaching the seed, also prevents oxygen reaching it. (iii) Development of embryo: The embryo should be fully developed at the time of seed fall. If it is not developed, the seed lies dormant, till it is fully developed. Eg:- Fraxinus floribunda (Seeds lies dormant for whole year after fall)  (iv) After ripening processes: Even if the embryo is fully developed, seeds, sometimes do not germinate because the embryo is not chemically ready for germination. Such seeds only germinate after the completion of after ripening processes. Eg:- Juniperus macropoda.  (v) Viability: Viability is defined as the potential capacity of a seed to germinate. Generally, recalcitrant seeds have less viability whereas orthodox seeds have longer viability. ◦ Recalcitrant seeds: Seeds which can not survive drying below a relatively a high moisture content (20-50% on wet basis) and cannot be stored at low temperatures for long period. Eg: Shorea robusta, Dipterocarpus, Azadirachta indica, Mangifera etc. ◦ Orthodox seeds: Seeds which withstand drying down to low moisture content of about (5% on wet basis) and can be stored at low temperatures for long period. Eg: Pinus, Pecia, Eucalyptus, Prosopis, Albizia etc.  (vi) Size of seed: The size of seeds, affects natural regeneration because while very minute seeds are washed away with rain, very big seeds do not get properly covered with soil or humus and so do not germinate.  It vary with the speices.  As a general rule, within the average size of seed produced by the species, the thicker the seed, the better the germination.