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Forests and Their ManagementDr. Ankur AwadhiyaDepartment of BiotechnologyIndian Institute of Technology, KanpurModule - 07 Silvicultural Management – I Lecture - 19Regeneration(Refer Slide Time: 00:16) [FL]. Today we begin a new module which is Silvicultural Management. This module has 3 lectures; Regeneration, silvicultural systems and clear felling systems.(Refer Slide Time: 00:30)So, we begin with the first lecture – ‘Regeneration.’So, what is regeneration? “Forest regeneration is the act of renewing tree cover by establishing young trees naturally or artificially-generally, promptly after the previous stand or forest has been removed.”So, when we say regeneration; we are generating the forest again. So, why do we need to generate a forest? Because, the previous stand or the forest has been removed. Now, this removal can be because of artificial factors or because of natural factors.Now, artificial factors could include the harvesting of timber. So, you had a forest you extracted all the timber out of it; for which you had to cut the trees, and once these trees have been cut; now, this site has to be regenerated. So, that the forest will grow again on this particular site. The second option would be a natural way in which the forest has been degraded. So, for instance, you have a forest and it is subject to forest fires or probably it is subject to an insect infestation; because of which the forest has been lost. So, once this forest has been lost, we now need to regenerate this area. So, that the forest grows again.So, forest regeneration is the act of renewing the tree cover. So, we are trying to renew the tree cover by establishing young trees, and these young trees can be established either naturally or artificially. So, we will look at both of these natural regeneration and artificial regeneration, and it is generally done promptly after the previous stand of forest has been removed. Why is it done promptly after the previous stand has been removed? Because, once the forest cover is removed from an area, the soil becomes exposed. So, the soil is now subject to the desiccating action of sun; it is subject to wind erosion, water erosion,leaking and so on. So, we have to do it as soon as possible before the soil loses its fertility; otherwise if it has lost its fertility, then probably we will have to do more expensive treatments such as the addition of manure or fertilizers. Or in some cases if the soil has been lost because of erosion, will we might have to put the soil back there on thesite again. (Refer Slide Time: 02:59)So, there are three ways to regenerate the forest. These are natural regeneration, assisted natural regeneration and artificial regeneration. So, in the case of natural regeneration, you are using the natural processes to regenerate this forest. In the case of assisted national regeneration, you are having a natural regeneration, but you are help that you are giving it some sort of an assistance to help it. And in the case of artificial regeneration, you can do artificial regeneration by direct sowing of seeds or you can do artificial regeneration by planting the seedlings. So, in this case, we are either sowing seeds or we are planting new plants.(Refer Slide Time: 03:42)So, let us now have a look at natural regeneration. Natural regeneration is defined as re?establishment of a forest stand by natural means that is by natural seeding or vegetative regeneration. So, we are re-establishing the forest stand by natural means, and there are two natural means; one is natural seeding. So, a number of trees produce their the fruits which have the seeds, and these seeds when they are released into the environment; theygerminate and form the new seedlings, or the other option is vegetative regeneration. (Refer Slide Time: 04:26)So, a good example of vegetative regeneration is coppicing. Now, what happens in coppicing is that you have this tree, and then for harvesting of timber this tree, is cut at this location. So, now, what you are left with is a stump; but then, with the next rains this stump will start giving out shoots here and these shoots will be known as coppices. c o double p i c e, and with time these coppices; so, what we generally do is; we remove one of these coppices and allow one to grow. So, then this coppice will after a while. it willform the seedling; it will form the new tree.So, after a while what you will see is that this portion has now formed into a new tree.So, this is a vegetative regeneration of the forest by natural means. So, it comes under natural regeneration. So, the characteristics are that it relies on older trees left on the land to provide seed to regenerate the site. So, in this case, we are leaving out the older trees. This seed - these trees are also known as seed trees or mother trees. So, we leave themout on the land so that they produce the seeds, and these seeds then regenerate the forest. And, the second characteristic is that it can be employed, only if the site has not yet been harvested. So, suppose you have a forest and you have completely harvested your forest. So, that no tree remains on the site. In that case, you cannot go for natural regeneration because there is no possibility of new seed production in the area. (Refer Slide Time: 06:08)So, the steps are one; you select the seed trees. Now, the seed trees have to be selected because they should be of a desirable characteristic. So, if you have those plants that are very young or very old, they might not produce copious amounts of seeds, whereas the matured plants that are in the prime of their health will produce a larger number of seeds.So, when you are harvesting your forest, the first consideration is that you should leave out the seed trees; they should not be harvested. So, you select the seed trees, then you log the area without damaging the seed trees, and then you allow time for the site to regenerate naturally. (Refer Slide Time: 06:51)Now, naturally regeneration is dependent on a number of factors that are mostly out of our control. So, it depends on seed production. So, suppose you went for a natural regeneration and you created a site; you left out the seed trees, but then in that particular year, these trees did not produce a number of seeds; or probably, they did not produce viable seeds, which means that the seeds were formed, but those seeds were not capable of germinating.So, what will happen in that case is that, because you do not have any control, your forests will not regenerate. So, it depends on a lot on the seed production in that year,which depends on seed year, age of the tree, size of the crown, climate external factors. Now what is seed year? Generally, for a number of species, we observe that the number of seeds that are produced in every year will vary. And generally, in every 3 or 4 years,there will be 1 year in which these trees will produce a very large number of seeds. So, that year in which a tree produces a very large number of seeds; a very large number of viable seeds, is known as a seed year (Refer Slide Time: 08:14)So, what we do in this case is that, if you have a species that shows this characteristic; so, what you will see is that, the number of seeds produced versus time in years. So, there will be a year in which the seed production is very high; next year it will be low, then it is again low; then again low; and then this year, its high; then its low for 3 years, and then again, its high. So, if your species shows this characteristic, and that is what you should do is that you should time your logging or harvesting of your forest, in such a manner that when you want seeds to be produce, it comes in the seed year.So, essentially what you will do is that you log after this point because the next year you will have a large number of seeds. So, natural regeneration is dependent on seed production, which depends on the seed year. It also depends on the age of the tree. So, if your tree is a matured tree; not very young, not very old, in the prime of its health, then it will produce a large number of seeds. It also depends on the size of the crown. So, what do we mean by size of the crown?(Refer Slide Time: 09:38) Suppose, we have 2 trees, both are of the same size, but this tree has as a small crown, but this tree has a very large sized crown. So, by a very large size crown, we mean that it will be having a number of branches and a large number of leaves in this tree.So, what happens is that because this tree, this tree B is having; so, this is A, this is B. So, because tree B is having a large crown size; large number of branches. So, those branches are the locations where it will have the fruits; it will have the flowers, and then it will have the fruits, which will have the seeds. So, more number of branches would generally mean that it will be having more number of fruits. Also, more number of leaves means that it has a very high amount of photosynthesis, which means that it is able to capture more and more energy; it is able to divert all the those energy for seed production.So, if you have a larger crowns tree, then it will produce more number of seeds. It also depends on the climate. So, if there is a mismatch of the of the climate; if there is an extreme climate or an extreme weather, then the then the seed production will be affected. It also depends on external factors like diseases pests or fire.So, if you have a tree that is a diseased tree, or if it has pests such as insects; so, there are a number of insects that are living on that tree with that have made holes in that in the trunk of that tree, and which are draining out the resources from that tree. So, the amount of energy that the that this tree will be able to devote to seed production will be less. So, typically, a tree that is diseased or is extremely pest infested will be having less number of seeds. It also depends on fire. So, in the case of, if you have a forest that has recently been exposed to a forest fire, then typically your trees will not be in a very good condition to produce the seeds.Now, natural regeneration also depends on seed dispersal by wind, water, gravity, birds and animals. So, what it means is that if you have a tree. (Refer Slide Time: 12:12)So, here is your tree and when this tree produces the seeds, they fall on the ground here. Now, if your seeds fall here and when a plant grows; when the next generation grows,this next generation is coming in the shade area of the mother tree. So, in which case,your seedling will not be able to get enough amount of sunlight; because of which, it might not grow as well. Whereas if you have a condition in which when you have these seeds; or when you have these fruits and then there is a bird that eats up these seeds, and then goes to another location, and then with its dropping the seed falls here. So, it is now away from the shade zone of its mother tree.So, what happens in that case is that, when the seedling grows, it gets enough amount of light and it is able to show a very good amount of growth. So, natural regeneration will also depend on seed dispersal. So, if you have seed dispersal by these different means, in that case, the quantum of natural regeneration will be much better.Now, your seed where ours your seeds were produced, then they got dispersed. The next stage is germination. So, germination is the stage, in which your seed gives out a new seedling. Germination is dependent on moisture, temperature, seed viability,permeability of seed coat, and other factors.So, if you have a seed and your seed fell into an area that was very dry. (Refer Slide Time: 14:00)So, here you have seeds. Now, your seeds got dispersed, but they got dispersed into an area that was say a rocky area, or an extremely dry area, or probably they got dispersed to an area that is waterlogged. So, in these conditions, your seeds might not be able to germinate. Now, if your seed does not germinate, then your regeneration will not happen. So, this is also a factor that controls the natural regeneration. Next is establishment. Establishment is development of a new crop to a stage where the young regeneration safe for normal from normal adverse influences like frost draught or weeds. So, what is establishment? In this case, suppose your seeds fell into an area that was in area, but then birds came and ate of these seeds. So, these seeds get eaten up.What will happen then?(Refer Slide Time: 15:08)Your seeds, even though they were capable of germinating, probably a few of those seeds have already germinated; but then they got eaten up. Now, will have to protect these young seeds and seedlings to a stage when where they are where they are able to resist the adverse influences.So, the time at which your new crop has reached to a level of maturity that it is safe from normal adverse influences. Now, the point through highlight here is normal adverse influences. When we talk about establishment, we are not talking about all the adverse influences. So, even after your new crop has established, and if there is say a forest fire,it is possible that your regeneration is gone. But then, in the case of establishment, we are only saying the normal adverse circumstances like frost, draught or weeds. So, if your seed is able; so, if your stand is able to reach this stage; your young crop are able to reach this stage, then your natural regeneration will be ok.(Refer Slide Time: 16:30)Now, natural regeneration has a number of advantages. The most important being low cost; it is practically free. So, you when you are doing your logging, you just leave a few trees and mother nature will take care of the other things; so, it is low cost. There is a less requirement of heavy machinery and labour. Practically, you do not have to do anything;the natural forces of dispersal will take care of everything. So, you do not have a large requirement of heavy machinery or labour. It gives you an aesthetically pleasing natural forest look. Because, this is a natural process. So, all the forest will look like a natural forest when they form it helps in preservation of adapted populations. What does that mean?(Refer Slide Time: 17:25) Suppose, you have a site; suppose you have 2 sites. Now, both these sites you have trees of the same species, but probably this site has more draught like conditions and this site has a more waterlogged lake conditions.Now, in this case, when your when your tree A was, when this site was being populated by new trees, because you had a draught like situation. So, those individuals that were better able to tolerate draught or were better able to resist the draught form in this location A. Whereas, those individuals that are better able to resist waterlogged conditions are get established in the location B.Now, in the case of natural regeneration, what happens is that the next generation of progeny that forms in this area also has the abilities to tolerate draught, and the next generation that forms in this area also has abilities through genetics to be better able to resist the waterlogged situations. And, this is a very big advantage of natural regeneration, because, in things like artificial regeneration when we are planting the seeds, it is very difficult to ensure that all the local micro-climatic conditions arematched accurately.So, for instance, if you went for an artificial regeneration and you took these seeds from A and if you planted them here in the B’s side, then because these seeds; the red seeds are able to tolerate draught, but they are unable to tolerate the water logged situations. So, your regeneration would not have occurred. But in the case of natural regeneration, the preservation of locally adapted populations ensures that the that the level of survival is better. So, there is also a good adaptation to micro sites and there is also a preservation of genetic variability. Why a preservation of genetic variability? Because, in the case of artificial regeneration,because you are you are collecting seeds from a few trees. So, it is not possible to collect from a very large number of trees. So, in that case, those trees that you collected the seeds from their genetic constitution is ah is maintained in the next generation, whereasthe other genetic variability; that was there in the site, gets lost. Whereas, in the case of natural regeneration, because you do not have to do anything; you just have to leave a few trees. So, typically a larger number of trees are left and so, the genetic variability that is present in the site is preserved. (Refer Slide Time: 20:28)However natural regeneration also has certain disadvantages. One; the seed crop must be available. For instance, if you want to regenerate an area that does not have any seed trees left, then you cannot go for natural regeneration. Dry soil conditions may result in heavy mortality.Now, in the case of natural regeneration, what you are doing is that you are removing a large number of trees for timber and you are leaving out a few trees as mother trees. But then because, you have removed the other trees; so, sunlight is able to reach to the soil surface and its also able to desiccate the soil. Theis dry soil conditions may result in heavy mortality; could be heavy mortality, because of insects and seed feeders that consume a number of seeds.So, because of these factors - the dry soil and the insect conditions, you do not have much control over the success rate of natural regeneration, and there have also beenconditions or cases, where the foresters went for a natural regeneration, but were unable to regenerate the site.So, in that case of a beautiful looking hill, that was come that was all full of trees; you went for a natural regeneration. But then, in that year, you were unable to regenerate it naturally. So, now, that complete hill has become denuded. (Refer Slide Time: 22:09)So, we also have examples such as the these. Then there is competition from other vegetation. Because, what is happening in this natural regeneration is that, you left out this mother tree, it gave out the seeds that got dispersed; but then, there is grass on the forest floor or probably there are some shrubs or probably there are some other trees that are now competing with your seedlings. So, because of this competition, there is a good chance that your regeneration might fail even more; so, because you are not doing anything to help your regeneration. Then, there is little control over spacing and stand density. So, if you want to manage a stand for timber; you will probably want to go for a situation, in which your spacing is well controlled. So, for instance, you will want to go for an area in which you plant seeds like these. So, that all your plants are at the same distance and are better able to utilize the resources. And, it also makes it easy to perform any management operations later on. But in the case of a natural regeneration, because you do not have any control over where your seeds are falling; you will have a situation in which in certain locations, you will have a more clumpy formation of your stand. In other locations, you will you might haveareas with very sparse number of trees.So, if you go for a with a natural regeneration, then you do not have a good control over the spacing in your stand and so, it might make it difficult to later on to perform other management operations. Also, you have a very less control over the stand density. So, here your density was uniform, if you went for artificial regeneration; but here you have a clumpy regeneration and so, there is a very less control over the density in your stand. There is also little control over genetic improvement. Because, you are not selecting those trees that and that have those properties that are better suited to your operations.So, for instance, in if you want to manage a stand for timber, you will probably want trees that grow very fast that attain a very good height; that have a very smooth bowl;and, that do not have a large number of branches; because the more the number of branches, the more wood is there that gets lost during the operations. (Refer Slide Time: 25:02)So, you will select for those trees that have a cylindrical bowl like this. Whereas, in the case of natural regeneration, you might have a situation in which the trees have a very irregular bowl with a large number of branches.So, even though you want trees like this, but you get trees like this. So, you do not have much control over genetic improvement. You cannot select those trees that have your desired qualities and the site may also take longer to regenerate, because there is nothing in your control. So, it might take longer to regenerate. (Refer Slide Time: 25:49)So, to overcome these disadvantages, we have got two options. We can go for assisted natural regeneration or we can go for artificial regeneration.Now, Assisted Natural Regeneration is or ANR is a method for enhancing the establishment of secondary forest from degraded grassland and shrub vegetation, by protecting and nurturing the mother trees and their wildings inherently present in the area.So, what you are doing here is that you are assisting or helping the natural regeneration.So, that the establishment of the secondary forest gets enhanced. And how are you doing it? You are doing it by protecting and nurturing both the mother trees and the wildings or the progeny.So, how do you do that? The method is that you give assistance to natural regeneration through removing or reducing the barriers to natural regeneration. So, we are trying to reduce the barriers, and these barriers include soil degradation, competition with weed species, recurring disturbances, unsuitable microclimate and so on. And, enrichment planting may also be done as in when required. (Refer Slide Time: 27:06) .So, what are the steps in ANR? The first thing is that, you do a marking of the woody regeneration and then, you liberate the woody regeneration by removing the nearby growth also through our process called ring weeding.(Refer Slide Time: 27:28)So, what you are doing here is that you had this mother tree that produce these seeds, and these seeds are now there on the ground. And, they have given out the seedlings at these locations.So, what you do here is the first step is that, you mark this woody regeneration, which means that you note that you have these woody regeneration 1, 2, 3, 4, 5, 6, 7. So, you note that you have woody regeneration here. Next, you liberate this woody regeneration by removing the nearby growth in a ring weeding fashion. What does that mean? It means that; suppose you had grasses in this whole area; so, in the case of ring weeding, what you will do is, for every individual that you have bark,you create a ring around it and you remove all the grasses that are there in this region; in this ring. So, you are not trying to remove all the grasses, but around every plant in a ring fashion; you are removing the grasses; so, that the competition that your seedling was facing is now removed.So, you liberate; this is known as liberation. So, you liberate the woody regeneration by removing the nearby growth in a ring weeding fashion. Then, you can also go for suppressing the weedy vegetation by pressing grass using a board etcetera. So, in this case you did a ring weeding, but you also try to suppress the nearby grass, by putting a board here and pressing all of these grasses. So, that you try to crush these grasses.Next, you protect this area from disturbance.  Because, everything is within your control. So, you have a good amount of flexibility. There is low management intensity, because once you have planted this area, the only thing that you need to do after a while is probably some amount of weeding or some amount of casualty replacement, which is, which means that, if there is ah if you have planted a seedling and it dies out after a while, you just replace that seedling.So, the amount of management intensity that is required in this region is very less. This option to introduce improved seed or planting material, which you did not have in the case of natural regeneration or ANR. The results are quicker, because in this case, the establishment also is quicker; because what you are doing is, you are taking your seeds;you are growing them in a nursery; you develop seedlings, and then you keep your seedlings in the nursery for say 2 or 3 years.So, you already have very tall plants, and by the time you put them on the soil, they are already quite well established. So, you do not have to wait for them to develop more resistance against the natural adverse conditions. So, the establishment is very quick in the case of artificial regeneration. There is also a better yield, and it creates even aged forest, because all the plants will be of the same age.(Refer Slide Time: 45:15)However, there are also certain disadvantages to artificial regeneration. It is cost and labour intensive, because everything is under your control; but also, everything has to beto be managed. So, you in the case of natural regeneration, you just left out a few trees and they developed their seeds, which germinated establish themselves. So, there wasthere was very little requirement of labour or money in in that process. But in the case of artificial regeneration, you have to select trees; you have to collect your seeds from those trees; you will you have to treat those seeds; you have to germinate those seeds; then you have to grow them in a nursery; you have to tend for them; you have to care for them; you have to put water; you have to protect them against diseases and insects; and, you have to complete this process for the next 2 or 3 years. Once that is done, you have to dig holes in in the ground; you have to make pits; then you put your seedlings; there the planting operation also has to be done manually or by using equipment.So, all of these require time; all of these require labour; all of these required costs. So, it is labour intensive and it is cost intensive. Also, it is less adapted to micro-sites, becauseit is possible that when you collected your seeds you, collected them from an area that was facing a little amount of draught. So, your plants are those that are better adapted to draught like conditions.So, the seeds that you collect from these areas will also generate plants that are better adapted to draught like conditions. But the final planting site might be one that is nothaving a condition of draught. On the other hand, it is having a waterlogged condition. So, in that case, it is and there is a good possibility that your plantation might fail.So, there is very little amount of control over adaptation to the micro-sites. Also, it results in more disturbance to soil and the area, because you are disturbing the soil you are doing your pits. And when you are doing your pits, you are also keeping your pits for a while till your planting material comes to that area, and in that period of time, your soil is exposed to the sun; your soil is also exposed to or susceptible to erosion, because of air or water.So, artificial regeneration, one disadvantage is that it leads to more disturbance to the soil in the area. But with all of these techniques and with all of this knowledge, now you can select which technique is the best suited for your species or for your area. So, in this lecture, we had a look at what is regeneration; how do we do regeneration; the kinds of regeneration, and what are the advantages and disadvantages of each and every of these techniques. So, that is all for todayThank you for your attention [FL].