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Introduction

August 12, 2019


and welcome to this course on forest biometry
i am doctor ankur awadhiya an officer in the indian forest service in this course we shall
look at what forest biometry is all about what we measure in this discipline how do
we measure those things in this discipline why do we need this discipline and so on so
let us look at this term forest biomatery let us look at the word roots so we have forest
biometry so this has three words in total one is forest the second is bio and third
is metry the term forest is derived from the latin word foris which means outside so this
is the same word root that we have in the case of foreign so foreign means in outside
land why do we call forest as forest because in earlier times and also ah quite ah correct
in in todays situations forests are outside of residential areas so they are not where
people live so they are outside of villages towns in cities so which is why we call these
forests now forests ah traditionally have been lands
where you have a number of trees so this is a land that is covered with trees
and also with some undergrowth so we could say forest is a tract of land covered with
trees and undergrowth in the case of our country india we have had
a case called as the godavarman case now in this case our honorable supreme court has
taken a dictionary meaning of forest so forest in india means two lands one from the dictionary
definition so that is any tract of land that is covered with trees and undergrowth or also
any land that is declared to be forest under any act so for instance if you went to rajasthan
and if you looked at the sand dunes there you would be having vast expanses of land
that do not have quite so many trees but they might be having some undergrowth do we call
these as forests yes if they have been defined as forests under any act or if they have been
worked upon as forest traditionally so we would call them as forests and we define them
as scrub forests so that is what forest is about the second
term that we have in our definition is biometry now biometry also is divided into two parts
so here we have bio now bio means something that is related to life so this is the same
word root that comes in say biography or in the case of biology or in the case of say
bioenergy or say bio geography or say biosynthesis so again looking at the word roots bio plus
graphing graphy means to write so biography is the writing of a life logy means study
so biology is the study of life bio energy is that energy that is created out of life
forms biogeography is geography that deals with different life forms biosynthesis is
the generation of the synthesis of chemicals by various life forms so bio means life something
related to life now the third point in this term is metry
now metry means to measure so ah where do we see this word metry we see it in thermometer
metron is to measure thermo means temperature so it is something that measures temperature
we see it in geometry metry is to measure geo means earth so the beginnings of the mathematical
discipline of geometry related to the measurements of ah parts of earth so which is why we call
it geometry we see it an photometer so meter means something that measures photo is light
so photometer is something that measures light so now looking at it in to to we have forest
biometry so metry is measurement so what do we measure here we measure something that
is related to bio so we measure the life forms where do we measure it we measure it in a
forest so forest biometry is the science of measuring forest
now why do we need this discipline why do we need a separate discipline of forest biometry
we need it for a number of reasons one so let us call this reasons for this discipline
so we have forest biometry why do we need this discipline one we need this discipline
manage things now why do we need to manage forest well because why do we need forest
in the first place we need ah forest for a number of reasons one they give us wood what
is something that is needed by the society we needed for the manufacturing of furniture
we needed for those we need it for a number of things one we might need forest to overcome
climate change because it is a ah because when trees make wood they are essentially
converting carbon dioxide into biomass so that is leading to carbon sequestration so
carbon sequestration is something that we need to bring down global warming so that
could be another reason to have forest we could also have forest just for the sake
of having it because it feels good to know that you have forests around it feels good
to go to a forest you feel rejuvenated you see a number of life forms you could be managing
forests for biodiversity because there are so many species all around and they need for
us to live so that is called as management by aims so you could be having the aim of
gathering wood for your society or to make a profit or for carbon sequestration or for
biodiversity you could also be managing a forest not for the wood for biodiversity but
for biodiversity peruse for instance our national parks and the wildlife sanctuaries so this
is there we are managing forests but then why do we need to measure forests for this
because you cannot manage anything till you know what you are managing till you know how
much of your quantity is there only then can be tell whether that quantity is growing with
time whether that quantity is reducing with time or whether that [quanticy/quantity] quantity
is remaining constant with time so if we plotted q versus t
now suppose you are managing your forests for biodiversity you would wanted to maintain
in a position of status curve if you wanted to to manage a tract of land that is scrub
forests that that is a denuded land it does not have any forests and if you wanted to
manage it in it in such a way that it would have for this later on in future you would
go for this curve similarly if you figured out that your forests were having this curve
you would think of reasons in which you could bring it to a steady state or to an increasing
trend so for all of these purposes you need to measure your forests the second reason
why we need this discipline is because its of its predictive value so for instance if
we are making a plan if you are making a a plan to say mitigate climate change and if
we say that today we have a forest of say ten million square kilometers and after five
years will be having a forest of say ten point five million square kilometers
so wood that change be substantial in our ah in our aim of a ah mitigating climate change
how much of more carbon would it be able to sequester if you wanted to know that we would
need a discipline with a predictive value so that would enable us to predict if in time
t equal to t naught if we had a biomass b is equal to b naught and at time t equal to
t when we wanted we want to know how much would the biomass b so which is why we need
a discipline with a predictive value now at what scale do we do these measurements these
scales could be at various levels so for instance you could be measuring some trees that are
growing in your backyard or you could be be measuring some trees that are growing in a
farmland because we are trying to promote agroforestry which is the application of forestry
to agriculture and agriculture to forestry so its a mixed bag in which in the same plot
of land you are you can grow some trees and you can also harvest it for agricultural purposes
so it becomes a dual use so suppose you want to want to popularize
ah agroforestry you would want to tell your farmers how much would there income b say
after five years or say after three years so for those cases you will need to measure
at a very small scale so if we look at the slide we would see that we can have measurements
at different scales you can have local measurements or say even district level measurements we
could be having regional level measurements say in the case of ah states we could be having
national level measurements or we could be even be having international level measurements
which might be important for planning purposes say for climate change mitigation now what
is the time span in which do we we do these measurements
now as we talked before we can have the time of present so for instance if you have a tract
with some trees you want to know how much of what is this so you would be measuring
it now you could also be having a time span of future which is used for predictive purposes
that is all about the timespan of measurements now what do we measure in forest biometry
if we looked at the slides here you can see that on the left side you have a monument
and ah right next to it is a tree on the right panel you can see a few logs of wood so what
can be measured using the science of forest biometry in the case of a tree you can measure
a number of parameters say the height of the tree the canopy of the tree so canopy is the
upper layer is the the upper which branches and leaves in a forest that often makes an
umbrella over the bare ground so as you can see in this figure ah you can measure this
the diameter of the canopy or the height of the canopy you could also be measuring the
diameter of the tree or in the case of the logs you could be measuring the diameter and
length of the logs from which you would be able to calculate the volume of the logs you
could be measuring the density of the wood so volume multiplied by density would give
you the biomass when you look up to the forest you can see the canopy so here on the left
panel we are seeing a forest from bottom up and on the right side of the panel we are
seeing or dense forest a view from inside the forest so what do we measure here well
we can look at canopy closure so canopy closure will tell us what is the percentage of the
view above that is covered by the canopies so suppose you had a canopy closure of around
say ninety percent or we could represent it as zero point nine so that would mean that
ninety percent of the light that is coming from top is being intercepted by the tree
cover so only ten percent of the light is able to reach down below to the ground level
on the other hand suppose you had a this ah canopy closure of say around zero point three
that would mean that if we draw these trees on the ground
so suppose this you have these two trees and you are trying to take a measurement at this
point so from here you would see that only this much amount of space is available for
light to penetrate and all the other portions have been taken up by canopies so suppose
if you had a canopy cover of say thirty percent so that would mean that seventy percent of
light is available at ground and thirty percent is intercepted
by canopy so why do we need this figure because if we had a canopy cover of thirty percent
so you have seventy percent of light that is available for your new growth so these
are the ah locations that you could use for regenerating the forest on the other hand
if you had a canopy cover of say eighty percent so you you have very little light now plants
need light to grow they need it for the for the process of photosynthesis to to generate
new biomass if your canopy was already very dense you might not be able to grow new trees
at the same time there are a number of species that are light demanding species so if you
have a light demanding species and if you if you put it into the soil at an area where
you have a very dense canopy cover this species would die because it requires it demands a
large quantum of light on the other end there are some trees known as shade tolerant trees
so if you had a a a very ah good canopy cover and if you planted your shade tolerant trees
they would be able to two to thrive there but if you planted them at a location that
had very less canopy they might die so all these measurements are required to manage
your forest coming back to the slide if we looked at ah the forest on the right panel
you have a stand now a forest stand is a contiguous community of trees with similar attributes
that distinguish it from adjacent communities so basically it is a patch of forest that
has very similar attributes that are different from ah other patches so the stand has stand
parameters so stand parameters includes your stand volume carbon sequestration biodiversity
index and so on so the the volume of this stand the ah the sum total of all the volumes
of different trees of the stand would give you the stand volume carbon sequestration
would be a measure of the amount of biomass that we have there in this time biodiversity
index would tell you how many different kinds of species are there in your stand so how
do we measure all these parameters so we have a number of parameters so what are the various
parameters that we have we have diameters as we have seen in both in the case of logs
and in the case of trees we have the girth which is if you have a tree the circumference
of the tree would be this girth so you can also measure it for logs or for trees you
could also be measuring the basal area which is the area of the cross section you could
be measuring height both for logs or for trees um you could be having a number of angular
measurements or let us call it just angles you could be measuring mass so if you have
mass in volume you could beginning density you could be measuring canopy or you could
be measuring other parameters so in this course we shall look at how do we measure all these
and what are the standard ways of doing it what are the instruments involved so if we
looked at the slide again so we have an instrument called calipers so you all have used vernier
calipers in the schools so calibers can be used to measure diameters or lengths but you
could also be using a ruler or maybe a tape for the same measurement so which one do you
use for what purposes we also have an instrument called the wedge prism that you see in the
central panel so it is a transparent piece of glass and if you are if you look through
through that wedge prism as you can see here it causes a displacement of whatever is in
front of it so here you can see in the central figure that ah the central portion of the
main stem is displaced towards the right so why do we need that we will come to it
in a later class we also have altimeters we have weighing balances for masses we have
i clinometers for angles we have rangefinders so these days laser rangefinders are a huge
rage so we could use those to measure distances we also have lidar know lidar stands for light
detection and ranging so this is one technique that uses laser lights to get a ah three dimensional
picture of your scene as we can see in the slide so here we are seeing in an aeroplane
that is going above our ground surface it is sending these waves in receiving goes back
and then we are having a simulation that is showing this the topography of the piece we
could be using a densiometer that is used for the measurement of canopies we could also
be using computer simulations now in the first class it might appear that that this is a
very primitive science because it is very easy to measure these things so for instance
if we look at this picture here we are seeing a few trees and suppose we wanted to measure
the tree in the center you would say that its very easy you would go there with a tape
or you go there with calipers of with with a ruler and you would get the measurements
it appears easy but the devil lies in the details
so as we can observe in this picture the tree is thicker near the ground and as we go up
the diameter reduces so to represent it in a figure if you have any tree the diameter
so suppose this is your tree the diameter at the bottom would be greater than the diameters
as you go up so suppose you had d one d two d three d four would having d one is greater
than d two is greater than g three is greater than d four this is because of a thing that
we call is taper so will come to taper in a later class but now coming back to the figure
on the slide here we can see that if you look at at the very bottom of this tree it appears
thicker if you go up it becomes smaller so if you wanted to measure the diameter of that
of this tree where are you going to measure it which is the correct region to measure
the diameter and if you choose any particular region as your standard would that be acceptable
to others there are a number of other complexities so
for instance if you looked at this site it appears to be a very much your swampy location
how are you going to access this site especially if you wanted to take your calipers along
how are you going to access it how do you take your instruments to this site even if
you are taken your instruments where do you stand this tree appears sloping towards the
left side so do you stand to the right of it to the left of it or where do you stand
where do you measure the diameter how do you deal with knots and branches so for instance
in this case you can see that ah this tree as soon as it if you move up from the bottom
you can see that you have a large branch that goes towards the left so how do you deal with
these so suppose you wanted to measure the length of the main stem is the central stem
the main stem or is the left side in a stem is the main stem where it is the canopy begin
so when we talk about parameters like let us draw a tree again so suppose this is your
tree and this is your canopy so where does the canopy start does it begin here does it
begin it suppose you have a branch here so this your canopy or suppose you have a branch
that goes like this is this your canopy so suppose you wanted to measure the canopy parameter
the canopy parameters include your canopy length your canopy diameter canopy height
so how do you ah you discern these values where does the height begin to what height
do we take the branch as a log so this is your tree if you wanted to cut this tree do
you cut it till here to you cut it till here do you cut it till here this is at all these
different heights you would be having a different diameter ah how do you deal with forking now
forking is the situation in which you have a tree and it gives out branches like this
so this is a forked tree now if you wanted to measure the diameter of this tree
where would you measure this diameter is this one tree or is this two trees how do you determine
that and where do you measure its diameter do you measure the diameters here you measure
the diameter here do you measure the diameter here or is the your diameters the sum of d
one plus d two or may be the average of d one and d two so how do you deal with these
complexities so we have a number of complexities and in this course we shall learn about these
and several other topics thank you so much for your attention

6 Comments

  • Reply g n May 29, 2018 at 11:52 am

    thank you sir …

  • Reply Aajesh kelhy September 28, 2018 at 11:52 am

    Sir please try to make videos on all forestry n its related topics

  • Reply Aditya yadav Aditya November 13, 2018 at 9:33 am

    Sir forest mensuration ka lecture daliye please

  • Reply Dekay Muxlim November 18, 2018 at 6:58 pm

    Excellent sir๐Ÿ˜

  • Reply accountkhatpen unodostres June 27, 2019 at 12:14 pm

    Sir, can you give me any fedback of the book, titled "Indian Forestry" by K.Manikandan and S.Prabhu?
    I was highly recommended for Forestry optional so I bought it. My issue is that the book is only extensive and not reliable.

    (If others have an info about the aforementioned book, do reply. It would help out alot)

  • Reply Yhebron Lagud July 13, 2019 at 5:15 am

    Hi Sir, you have very good presentation in your videos and a superb lecture. May I ask sir the book you are using in your lecture. Thanks

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