Forest Management Revision | Silviculture | New Trends | Alison
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Module 1: Revision in Forest Management

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Revision in Silvicultural Practices and Newer Trends in Forestry

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Forests and Their Management Dr. Ankur Awadhiya Department of Biotechnology Indian Institute of Technology, Kanpur Module - 12 Revision Lecture - 36 Revision (Part 3) (Refer Slide Time: 00:16) [FL] We move forward with our Revision module. So, in module 9, we looked at logging and yield, logging and processing, growing stock and increment, and yield and sustained yield.(Refer Slide Time: 00:25) Now, logging; the process of logging or cutting trees and harvesting trees begins with this stage of cruising, in which the timber lands are surveyed to locate and estimate the volume and grade of standing timber that meets the requirements. (Refer Slide Time: 00:38) This is followed by marking which is a selection of trees for harvesting; based on forest management prescription, standard colours are used. And, typically, yellow or orange means that a tree has to be cut for harvest, blue means that it has to be retained. Typically, we use blue for trees that are very close to a river, red is boundary line, white is research plot and black is a correction marking to mark over the mistakes. (Refer Slide Time: 01:07) So, during marking, we make an enumeration register followed by a marking register. The enumeration register tells us what each tree is, how does it look like, what are its characteristics. And then, the marking register makes use of the enumeration register to specify which trees are to be felled, and how do these trees look like, what is their species, what is their diameter, what is the height, what is the condition and so on. (Refer Slide Time: 01:37)Then, felling is done and using axe, saw, chain saw, or other devices. (Refer Slide Time: 01:43) The most important factor is safety on the floor and especially, the distances that need to be maintained from different equipment and also from the falling tree. (Refer Slide Time: 01:53) So, we decide on the escape paths, which are typically 45 degrees to the back of the felling; we decide on 2 escape paths for every tree.(Refer Slide Time: 02:03) Now, in the process of logging, we make the cuts. So, there are different cuts; you have the face cut, on the front which comprises of the top cut, and the bottom cut, and followed by a back cut, and the portion that remains in between is known as the holding wood which also acts as hinge. (Refer Slide Time: 02:23) So, this is how the cuts are made. You make the top cut, then bottom cut, followed by the back cut.(Refer Slide Time: 02:29) Now, conventionally, 3 faces are generally used. The first one is a conventional face where the top cut is at 45 degrees, the bottom cut is parallel to the ground, the Humboldt cut has a top cut which is parallel to the ground, and a bottom cut which is downwards and there is also an open cut where the angle is greater than 70 degrees. (Refer Slide Time: 02:51) And, all these 3 faces have different advantages. The conventional face has the greatest accuracy in constructing the face cuts, Humboldt face has the greatest saving of timber, and open face provides the greatest control by the hinge wood.(Refer Slide Time: 03:04) (Refer Slide Time: 03:07) So, this is how a front cut is being made.(Refer Slide Time: 03:09) Back cut made with a saw and the portion that remains makes up for a hinge. (Refer Slide Time: 03:12)(Refer Slide Time: 03:19) So, this is how a stump looks like. Then, you have the felled logs. (Refer Slide Time: 03:22)(Refer Slide Time: 03:23) Then, these felled logs are delimbed. So, delimbing is the process of cutting off the branches. Generally, these branches are left on the site so as to protect the regeneration and also to act as food for the herbivores. (Refer Slide Time: 03:43) But, in our country, because of a dearth of timber, we generally these branches are also taken out.(Refer Slide Time: 03:46) Then, bucking is the process of cutting the timber to size. (Refer Slide Time: 03:48) Then, hammer marks are put on this on these timber blocks.(Refer Slide Time: 03:52) (Refer Slide Time: 03:57) And then, these timber is skidded from the logging area to the landing area, typically using elephants or tractors or labour, and then on the landing site, these timber are arranged in the form of stacks.(Refer Slide Time: 03:59) (Refer Slide Time: 04:01)(Refer Slide Time: 04:02) (Refer Slide Time: 04:09)(Refer Slide Time: 04:10) (Refer Slide Time: 04:12) So, this is how stacks look like; and these stacks are also known as thappis, and in the we also maintain register for a thappi.(Refer Slide Time: 04:20) And then, there is loading and transportation in which the logs are moved from the landing area to a depot. (Refer Slide Time: 04:26) This loading can be done using a crane ,or through using a forwarder; is a machine in which you have a truck and a crane together.(Refer Slide Time: 04:29) (Refer Slide Time: 04:37)(Refer Slide Time: 04:38) Then, it is unloaded in a depot. (Refer Slide Time: 04:40) (Refer Slide Time: 04:54)And, in the depot, the typical processes are seasoning in which is a process in which the amount of moisture in the wood is reduced slowly so as to avoid any deformities. Then, grading is done in which timber of similar size and shape and condition is put together. And then, the graded lots are made; they are again marked with paint. (Refer Slide Time: 05:03)(Refer Slide Time: 05:04) (Refer Slide Time: 05:06) And then, they are put up for auction.(Refer Slide Time: 05:09) Now, people can use the this wood directly to make furnitures or other stuffs, or they can convert it into plywood and generally soft wood is used to make plywoods. In the process of making plywood, first of all the the timber is converted into thin sheets like shavings and then these sheets are glued together using a press. (Refer Slide Time: 05:26)(Refer Slide Time: 05:29) (Refer Slide Time: 05:30)(Refer Slide Time: 05:31) (Refer Slide Time: 05:32)(Refer Slide Time: 05:33) In the next lecture, we looked at growing stock in increment. (Refer Slide Time: 05:36) Growing stock is defined as volume of all living trees more than X centimeter in diameter at breast height or above buttress if these are higher, measured over bark from the ground or stump height to a top stem diameter of Y centimeter, excluding or including branches to a minimum diameter of Z centimetres. And, it excludes small branches, twigs, foliage, flowers, seeds, stump and roots. So, essentially growing stock is the volume of all the timber of all the trees put together, and because very small timber is difficult to measure; so, we typically remove very small timber from these calculations. And, in India, X is taken to be 10 centimeters. (Refer Slide Time: 06:23) So, it is the sum total of all trees by number or volume or biomass growing within a particular area of interest. (Refer Slide Time: 06:31) Now, we also define a commercial growing stock which is the part of the growing stock of species, considered as actually or potentially commercial under current market conditions, measured above a minimum say “X centimeter” diameter at breast height.(Refer Slide Time: 06:45) Now, there are different factors that affect growth in natural forest: regeneration, spatial distribution, silvicultural treatment, artificial thinning, site conditions, climatic conditions. (Refer Slide Time: 06:57) And similarly, in the case of plantation forests, these are the factors that influence growth, initial spacing and treatment, silvicultural treatment, artificial thinning and pruning, site conditions including nutrition and climatic conditions.(Refer Slide Time: 07:12) Next, we look at the logistic growth equation. (Refer Slide Time: 07:16) Which is the equation for the S shaped sigmoidal curve, and this tells us that the change in the growing stock which is dy by dt is equal to r, which is the intrinsic growth rate, multiplied by the growing stock at that particular point of time, multiplied by K minus y divided by K, where K is the carrying capacity of the environment. Now, if we look at this curve, there are 3 phases: this is the lag phase where the growth is very slow, this is height, and then you have the phase of stagnation or stability.(Refer Slide Time: 07:50) So, we have the lag phase, log phase and the stationary phase. (Refer Slide Time: 07:54) Now, increment is defined as an increase in diameter, growth, basal area, height volume, quality or value of individual trees or crops during a given period. So, increment is what is changing, what is the increase.(Refer Slide Time: 08:07) And, in a stand, trees put increment, but not all at the same time. And so, we define different components of increment. So, in growth or recruitment is the volume of those trees that were not counted in the first measurement due to their small diameter, but are now countable due to the increase in diameter. Harvest is the volume of those trees that were harvested during the measurement period; mortality is the volume of those trees that died during the measurement period. (Refer Slide Time: 08:35)And then, we can define the net growth in growing stock as V 2 minus V 1 that is the change in the growing stock in the two measurement periods; so, V 2 minus V 1. The net growth in initial volume is V 2 minus V 1 plus H, which is the trees that were harvested, minus I, which is the trees that were recruited in this period. And, gross growth in the initial volume is given as V 2 minus V 1 plus H minus I plus M. (Refer Slide Time: 09:10) Then, we define periodic annual increment as the increment over a period of P years at any stage in a tree’s history. So, it is PAI is the growing stock at time t minus growing stock at a time t minus p divided by P. So, this is the average rate of increment over a specific period.(Refer Slide Time: 09:36) If this specific period is made to be 1 year, then we call it a current annual increment which is the increment over a period of 1 year, at any stage in the tree’s history. (Refer Slide Time: 09:46) So, if we looked at the logistic growth equation, the CAI will be given as the differential of this curve or y prime t. So, here, you have the logistic growth equation, this one is y prime. Now, y prime is essentially the slope of this curve. So, in this portion, it will be very less; in this portion it will be very less; in this portion it will be maximum, which is what we are seeing here.(Refer Slide Time: 10:13) We also defined mean annual increment which is the increment over the whole period from origin to a specific age. So, mean annual increment is given by the growing stock at time t divided by t, which is what we are seeing here by this yellow curve. Now, the CAI is maximum at the point of inflection, and the MAI is maximum at the point where CAI and MAI are cutting each other. (Refer Slide Time: 10:43)And, the this point of cutting also gives us the optimum harvest time, this is the time when the stand has reached its maximum mean annual increment, after this point the stand will continue to add it to its growing stock, but at a lower rate. (Refer Slide Time: 10:58) Now, what are the factors affecting increment? These are species, internal conditions: both genetic and physiological, and external conditions: climatic, edaphic and biotic. (Refer Slide Time: 11:08) Site quality is defined as the relative productive capacity of a particular site. The relative productive capacity not the absolute productive capacity, because the at the absolute productive capacity is given by a combination of site quality plus the management inputs. So, site quality ask the question, if you are not doing any management input to the site, what is the amount of growing stock or increment that this site can support? (Refer Slide Time: 11:39) Now, what are the management inputs? They are fertilizer, site treatment, irrigation, grazing, control over soil, compaction and growing stock manipulation. (Refer Slide Time: 11:48) Now, the measurement of site quality is done in through various methods. The first one is the CVP index or the Patterson index; this is the formula TV into P into G into Edivided by T a into 12 into 1000 and forest growth happens only when I is greater than 25. The other option is that of looking at the vegetative characteristics. So, you actually look at what plants are growing in that area. So, you can look at the species such as, if you see that Palash is there in in an area; then Palash is an indicator of a degraded forest or it tells you that the site quality is not that high, and you can also look at tree characteristics, that is you can look at what is the size of the trees that are actually growing there. If they have a large DBH, if they have good basal area, if they have good height, good volume, then it will tell us that the site quality is good. (Refer Slide Time: 12:42) Now, field estimation of site quality is done through 2 methods: crop height method and the sample plot method. Now, in the crop height method, you get the top height and compare it with the yield table, which will give you the top heights for different site qualities. Now, top height is not the height of the tallest trees; it is the mean height of trees with the largest DBH in a stand. This; the second method; is the sample plot method in which case we plot the diameter height curves and then compare them with the standards.(Refer Slide Time: 13:13) So, here we are seeing that there are these 4 different standards 1, 2, 3, 4 and, this is the actual field situation. So, we can say that this one is very close to site quality 3. (Refer Slide Time: 13:30)(Refer Slide Time: 13:34) Next, we looked at yield and sustained yield. Yield has got two meanings: the amount of timber that can be harvested per period, which is typically taken to be 1 year. So, the amount of timber that you can harvest every year. Or, the second meaning is the amount of timber that can be removed at any time. We just asking the question that, if you look at a snapshot of the forest, what is the total inventory of growing stock that is available that can be removed.. (Refer Slide Time: 13:58)But typically, we go with sustained yield which is yield that can be harvested every year till perpetuity. (Refer Slide Time: 14:04) Now, to find out these yields or to compute these yields, we have different methods. The easiest one is the area method. (Refer Slide Time: 14:13) Now, in the area method, we say that for an even-aged crop the area that should be processed every year is equal to the total area divided by the rotation period.(Refer Slide Time: 14:25) So, this is a very simple method. It works for even-aged crop; each coupe can be intensively treated. (Refer Slide Time: 14:30) However, it is difficult to predict volume. So, you cannot tell what is the amount of timber that you will be extracting every year, what is the value that you will be generating every year, it’s difficult to tell, and it is not suited for uneven-aged crops.(Refer Slide Time: 14:45) The second method is the volume method; it is a slight modification of the area method. So, the volume that can be extracted every year or the volume that can be harvested is equal to the total volume divided by the rotation period. (Refer Slide Time: 14:59) The disadvantages are that it does not include growth and increment of the crop and it does not consider the site quality.(Refer Slide Time: 15:06) And, the next method is the Hundeshagen’s method of yield regulation, which essentially says that, if you have more inventory, if you have more crop, then you can extract more. If you have less crop, you can extract less. So, essentially, harvest is proportional to the inventory or H by I is a constant. However, even in this case, there is an issue because in the case of very young crops; this will continue to give us some value of harvest, even though there is no tree that is mature enough for harvesting. (Refer Slide Time: 15:38) (Refer Slide Time: 15:44)(Refer Slide Time: 15:46) Now, one very commonly used method is the von Mantel’s method, which approximates inventory by the area of a triangle, and it tells us that the volume that can be extracted every year is equal to 2 times of the inventory, divided by R or 2 times the growing stock divided by R. So, as against the volume method, which told us that the amount extracted is growing stock divided by R, this one says that you can extract 2 times of that because the growing stock is not a stationary thing; it is also putting up increment. So, this is an improvement over the volume method.(Refer Slide Time: 16:13) Then, we also have the Austrian formula which says that you can extract the annual increment, but then you also have to consider the excess inventory over the normal forest that needs to be adjusted and this adjustment can be done over a period of say P years. In which case, you will say that the amount extracted every year is increment plus I t minus I of a regular or a normal forest divided by P. P is generally taken to be one-third of the rotation period. (Refer Slide Time: 16:43)Next, we have the Cotta’s formula. And, Cotta formula says that the volume that the annual yield is equal to the volume or the growing stock divided by the number of years in the periodic block plus i by 2, where i is the annual increment. (Refer Slide Time: 17:04) Then, the next method is yield regulation by the number of trees; in which case, we plot the curve for a normal forest, we plot the actual field situations. And, there in the ND curve; we can see that for each and every time interclasses, how many trees can be extracted to bring our forests close to the normal forest. (Refer Slide Time: 17:24)And finally, we have yield regulation by simulation through computers; in which case, we input the current inventory, we input growth parameters, we iterate it to get or to generate a growth pattern of the forest, make decisions about felling, input the felling decision to the model, and then iterate it once again. And, this process will go on again and again. So, after this iteration, you will again make a decision about felling and put the felling decision, iterate. Then, again make a decision about felling, and put the felling decision, iterate and this process will go on and on. (Refer Slide Time: 17:55) Then, in module 10, we looked at silvicultural practices; that is seed collection and treatment, nursery techniques, planting and tending.(Refer Slide Time: 18:04) In seed collection, we defined seed as an embryonic plant that is enclosed in an outer protective coating. (Refer Slide Time: 18:09) This is how seeds look like.(Refer Slide Time: 18:11) So, you have an outer protective coating in the form of a seed coat, and you have the embryonic plant, which is shown as the cotyledons, which are the leaves and the hypocotyl, and there is endosperm, which provides food to this embryo. (Refer Slide Time: 18:26) Now, we define good seeds; good seeds are well ripened and healthy. They are pure and free from inert materials and weed seeds, viable and have good germination capacity, uniform in their structure and appearance, free from damage and should not be broken and infected by pests and diseases.(Refer Slide Time: 18:44) Now, the quantity of seeds that you need for your operations depends on the number of plants that are required; including the amount that you will require to casualty, plus the germination percentage, plus it depends on the loss in picking out, mortality in seedling containers or transplanting and the culling loss. (Refer Slide Time: 19:05) And, the total quantity of seeds required is given by the number of seedlings that are required for planting, divided by the survival factor; where survival factor is given as germination percentage, multiplied by prickling loss factor percentage, multiplied by mortality factor, multiplied by culling loss factor. And, total quantity of seeds that is required is given by total number of seeds divided by number of seeds per kg. (Refer Slide Time: 19:29) Now, when we are doing a seed collection, we need to determine the best days for seed collection. Typically, seeds are collected in the seed years when the plants have a very large production of seeds. But even in the seed year, which is the particular day when you should be doing the collection, is determined by either laboratory methods or field methods. Now, laboratory methods include maximum dry weight, chemical analysis of fat and nitrogen content, examination of embryo development and endosperm of sample seeds through X-ray radiographs; typically, by soaking of the seeds in barium chloride solution, which makes it opaque to the X-rays. And, barium chloride is only able to enter it into the non-living portions, it does not enter into the living portions. So, you can very easily if you see the embryonic development. Or, you can look at the moisture content of the fruits. The field method includes density of fruits, colour of fruits and visual examination of seed contents after cutting.(Refer Slide Time: 20:30) We also determine the best trees to collect the seeds from, and these are generally dominant or co-dominant trees; you collect from a minimum of 10 to 50 trees, collect from trees that are far from each other to avoid collecting from half siblings or parents. Before collecting, mark individual trees, collect equal number of cones, fruits or seeds per tree, mixing of trees make for large scale collections. (Refer Slide Time: 20:56)Now, for a proper seed collection, you need to organize collecting teams, transportation, equipment, records, permits and seed extraction, because as soon as you collect these seeds, they have to be processed. (Refer Slide Time: 21:10) Now, ways of collecting seeds include natural seed fall, manual shaking, mechanical shaking, use of tree funnels, raiding of animal caches including squirrels and ants, collection by plucking and collection by cutting, breaking and sawing which is typically the last. (Refer Slide Time: 21:28)Other operations include depulping, where the pulp is removed; drying under the shade, sun drying, drying with artificial heat or kilns; dewinging of seeds; hand picking of large sized impurities, threshing, sieving, blowing, grading, testing and so on. (Refer Slide Time: 21:46) Now, seed testing; we require information about the determination of genuineness, determination of purity, determination of seed viability and vigour. Now, seed viability and vigour; the vigour is the rate at which these seeds will actually grow into plants. So, this these are determined by cutting test, physical test such as winnowing and floating, chemical tests such as TTZ or Triphenyl Tetrazolium Chloride or Bromide reduction test, the viable parts are stained in red, non-living parts become colourless. So, if you have a seed in which it looks colourless throughout, it means that it has already died, or we can look at germination tests in which the seeds are actually germinated. In which case, we look at 2 parameters; germination percentage which is the number of seeds that germinate as a percentage of the total number of seeds that were tested. Helps in conservation breeding, helps in standardization of stud books.(Refer Slide Time: 50:21) And, we looked at the case study of Mysore zoo as an example. (Refer Slide Time: 50:26)(Refer Slide Time: 50:27) (Refer Slide Time: 50:28)(Refer Slide Time: 50:29) What all things are done, how animals are cared for. (Refer Slide Time: 50:36) Then, we looked there to bear rescue facility and so on.(Refer Slide Time: 50:40) (Refer Slide Time: 50:42) And also, the need for behaviour enrichment so that the animals do not feel bored. Now, next we looked at in situ conservation. So, we started with the traditional ways of creating reserves. Earlier results were created by looking at beautiful areas, high species diversity or areas that are harbouring unique animals.(Refer Slide Time: 50:58) But these days, if you look at the scientific creation of reserves, we have to look at areas with high species richness. So, that is more number of species per unit area, high species endemism which is those species that are only found in certain areas, and high number of species under threat. (Refer Slide Time: 51:15)(Refer Slide Time: 51:16) (Refer Slide Time: 51:17)(Refer Slide Time: 50:18) So, we can look at all these different maps and then come up with those sites that have high richness endemism and threat and they are known as the biodiversity hotspots. (Refer Slide Time: 51:22)(Refer Slide Time: 51:25) Now, typically, the level of threat that we are targeting is a middle level of threat, because if it is very low threat then probably you do not need a sanctuary or a reserve and if the threat is very high, than probably even the construction of a sanctuary is not going to help that situation. Or the in the time that it will take to construct the sanctuary, the area will already be lost. (Refer Slide Time: 51:51) We also looked at gap analysis, which identifies holes in the existing network of protected areas.(Refer Slide Time: 51:57) (Refer Slide Time: 51:59) Then, we looked at principles of reserve design; you need to have big reserves, because it is costing cost effective.(Refer Slide Time: 52:01) And also, it provides more habitats, it is less vulnerable to catastrophes. (Refer Slide Time: 52:10)(Refer Slide Time: 52:12) So, one big is better than several small, closer reserves are to be promoted. (Refer Slide Time: 52:16) Clustered formation is preferred as compared to a linear formation.(Refer Slide Time: 52:19) (Refer Slide Time: 52:21)(Refer Slide Time: 52:22) Circular reserves are preferred because they have low biotic pressure. Connection needs to be made to be maintained. (Refer Slide Time: 52:26) And then, we looked at of sanctuary creation. So, like in Madhya Pradesh, we on the government began with looking at the biodiversity intactness index map, which tells us what are the locations where the biodiversity is still formed. So, this is an indication of the species richness.(Refer Slide Time: 52:43) Then, gap analysis; then, we also did a gap analysis to understand which are the locations that need sanctuaries and then we also looked at clustered approaches, how to maintain the connectivity of these habitats, how to come up with new stepping stone corridors. While ensuring that the level of threat is kept as low as possible; so basically, we went with only reserve forest areas where all the rights are there with the government, and where we do not have any villages or encroachments or forest right pattas, which have been given over the years. And with that, we came to the conclusion about what are the areas of the sanctuaries that need to be made. So, that brings us to the conclusion of this course. I hope you like this course. Good luck with your exam preparation. Do well. So, that is all for today. Thank you for your attention [FL].

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