3. ecosystem measurement

8/2/2019 3. Ecosystem Measurement

1/34

Click to edit Master subtitle style

4/15/12

Ecosystem MeasurementMenghitung Parameter Lingkungan


2/34

4/15/12

EcosystemsEcology is the study of inter-relationships between organisms and their

environment. Its aim it to explain why organisms live where they do.

Ecosystem A reasonably self-contained area together with all its livingorganisms

Habitat The physical or abiotic part of an ecosystem, i.e. a definedarea with specific characteristics where the organisms live,

e.g. oak forest, deep sea, sand dune, rocky shore,moorland, hedgerow, garden pond, etc

Community The living or biotic part of an ecosystem, i.e. all theorganisms of all the different species living in one habitat.

Biotic Any living or biological factor

Abiotic Any non-living or physical factor.

Population The members of the same species living in one habitat.

Species A group of organisms that can successfully interbreed


3/34

4/15/12

Estimating Populations andDistribution

One of the most fundamental problems

faced by community and populationecologists is that ofmeasuring populationsizes and distributions.

The data is important for comparingdifferences between communities andspecies. It is necessary for impactassessments (measuring effects ofdisturbance) and restoration ecology(restoring ecological systems).

It is also used to set harvest limits on

commercial and game species (e.g. fish,


4/34

4/15/12

Estimating Populations andDistribution

To study the dynamics of apopulation, or how the distributionof the members of a population isinfluenced by a biotic or an abioticfactor, it is necessary to estimatethe population size. In otherwords, it will be necessary to

count the number of individuals ina population.

Such counting is usually carried

out by taking samples.


5/34


6/34

4/15/12

The objective of sampling is to collect as manyrandomly selected samples as possible(so as to

increase the proportion of the total populationsampled). The accuracy of an estimate increases with thenumber of samples taken. This is because the numberof individuals found in any given sample will vary from

the number found in other samples. By collectingnumerous samples, the effect of these variations can beaveraged out. The purpose for collecting the samples randomly is to

avoid biasing the data. Data can become biased whenindividuals of some species are sampled morefrequently, or less frequently, than expected atrandom. Such biases can cause the population size tobe either over estimated or under estimated, (erroneous

estimates of population size).

Sampling Objectives


7/344/15/12

Population size generally refers to the number of

individuals present in the population, and is self-explanatory.

Density refers to the number of individuals in a given

area.

For ecologists density is usually a more usefulmeasure. This is because density is standardized perunit area, and therefore, can be correlated with

environmental factors or used to compare differentpopulations.

Population and Density


8/344/15/12

In a random dispersion, the locations of all individuals areindependent of each other.In a uniformdispersion, the occurrence of one individualreduces the likelihood of finding another individual

nearby. In this case the individuals tend to be spread outas far from each other as possible.In a clumpeddispersion, the occurrence of one individualincreases the likelihood of finding another individualnearby. In this case, individuals tend to form groups (or

clumps

Distribution and Density


9/344/15/12

Spatial distribution ofpopulations is important because it

provides information about the social behavior and/orecological requirements of the species.

Some plants in clumped distributions because theypropagate by rhizomes(underground shoots) or becauseseed dispersal is limited. Clumped distributions in plantsmay also occur because ofslight variations in soilchemistry or moisture content.

Many animals exhibit rather uniform distributions becausethey are territorial (especially birds), expelling all intrudersfrom their territories. Random distributions are alsocommon, but their precise cause is more difficult toexplain.

Spatial Distribution


10/344/15/12

Unfortunately, it is often difficult to visually assess the

precise spatial distribution of a population.Furthermore, it is often useful to obtain some number(quantitative measure) that describes spatialdistribution in order to compare different populations.For this reason, there are a variety of statisticalprocedures that are used to describe spatialdistributions.

Communities are assemblages of many species living in

a common environment. Interactions between speciescan have profound influences of their distributions andabundances. Comprehensive understanding of howspecies interact can contribute to understanding howthe community is organized.

Spatial Distribution


11/344/15/12

One way to look at species interactions is to evaluate

the level of association between them.Two species are said to be positively associated if they arefound together more often than expected by chance. Positiveassociations can be expected if the species share similarmicrohabitat needs or if the association provides some benefitto one (commensualisms) or both (mutualism) of the speciesinvolved.

Two species are negatively associated if they are foundtogether less frequently than expected by chance. Such asituation can arise if the species have very different

microhabitat requirements, or if one species, in some way,inhibits the other. For example, some plants practiceallelopathy, the production and release of chemicals that inhibitthe growth of other plant species. Allelopathy results in anegative association between the allelopathic species and

those species whose growth is inhibited.

Species Association


12/34


4/15/12

Sampling TechniquesCara-cara sampling ekologi


13/344/15/12

Random sampling with quadrats

The quadrat method is used primarily in studies of plant populations,or where animals are immobile. The principal assumptions of this

technique are that the quadrats are chosen randomly, the organismsdo not move from one quadrat to another during the census period,and that the samples taken are representative of the population as awhole. It is often conducted by dividing the census area into a grid.

Each square within the grid is known as a quadrat and represents thesample unit. Quadrats are chosen at random by using a randomnumber generator or a random number table to select coordinates.The number of individuals of the target species is then counted ineach of the chosen quadrats.

Ecologists use units to measure organisms within the quadrats.Frequency (f) is an indication of the presence of an organism in aquadrat area. This gives no measure of numbers, however the usualunit is that of density the numbers of the organisms per unit area.Sometimes percentage cover is used, an indication of how much the

quadrat area is occupied.

i l


14/344/15/12

Counting along Transects

Transects are used to describe the distribution of species ina straight line across a habitat.

Transects are particularly useful for identifying anddescribing where there is a change in habitat.

A simple line transect records all of the species whichactually touch the rope or tape stretched across thehabitat.

A belt transect records all the species present between

two lines, and an interrupted belt transect records all thosespecies present in a number of quadrats places at fixedpoints along a line stretched across the habitat.


15/344/15/12

Mark-release-recapture techniques for more mobilespecies

This method of sampling is most useful when dealing with ananimal population that moves around.Ecologists must always ensure minimum disturbance of theorganism if results are to be truly representative and that thepopulation will behave as normal.

In this method individual organisms are captured, unharmed,using a quantitative technique. They are counted and thendiscretely marked or tagged in some way, and then releasedback into the environment.After leaving time for dispersal, the population is thenrecaptured, and another count is made. This gives thenumber of marked animals and the number unmarked.

This can allow ecologists to estimate of the entire population ina given habitat.


16/344/15/12

The following equation is used to estimate

the population:

S = total number of individuals in the

total population

S1= number captured, marked and

released in first sample e.g. 8S2= total number captured in second

sample e.g. 10

S3= total marked individuals captured insecond sample e.g. 2

S = S1 X S2

S3

S = 8 X 10

2population = 40individuals


17/344/15/12

Diversity

Diversity depends on the number of

species (species richness of acommunity) in an ecosystem and theabundance of each species thenumber of individuals of each species.

The populations of an ecosystem cansupport demands on abiotic and bioticfactors.

The growth of populations depends onlimiting factors


18/34

4/15/12

Abiotic factorsphysiological adaptations of organisms only allow them to live in

a certain range of pH, light, temp etc it is part of what definestheir niche.

Biotic factors (interactions between organisms)

Intraspecific competition occurs between individuals of the samespecies, eg for a patch of soil to grow on, or a nesting site or food.

Interspecific competition occurs between different speciesneeding the same resource at the same trophic level.Plant species compete for light, herbivore species compete forplants or carnivore species compete for preyPredation a predator is a limiting factor on growth on thepopulation of its prey and the prey is a limiting factor on thepredator population

LimitingFactors


19/34

4/15/12

D = N(N-1)n(n-1)

Where:

N = total number of organisms of all species inthe areaD = index of diversityn = total number of organisms of each species in

the area

An index of diversity is used as a measure of therange and numbers of species in an area. Itusually takes into account the number of species

present and the number of individuals of eachspecies. It can be calculated by the following

formulae:


20/34

4/15/12

Diversity:crested

newt

8

stickleback 20

Leech 15

Great pondsnail

20

Dragon flylarva

2

Stoneflylarva

10

Waterboatman

6

Caddisfly 30

d =111 X 110

(8X7)+(20X19)+(15X14)+(20X19)+(2X1)+(10X9)+(6X5)+(30X29)

d = 12210

2018 therefore d = 6.05

L Di i


21/34

4/15/12

In extreme environments the diversity of organisms isusually low (has a low index number). This may result in

an unstable ecosystem in which populations are usuallydominated by abiotic factors.

The abiotic factor(s) are extreme and few species have

adaptations allowing them to survive. Therefore foodwebs are relatively simple, with few food chains, orconnections between them because few producerssurvive. This can produce an unstable ecosystem becausea change in the population of one species can cause big

changes in populations of other species.

Low Diversity:

Hi h Di i


22/34

4/15/12

In less hostile environments the diversity of organisms is

usually high (high index number).

This may result in a stable dominat ecosystem in whichpopulations are usually ed by biotic factors, and abioticfactors are not extreme.

Many species have adaptations that allow them to survive,including many plants/producers.

Therefore food webs are complex, with many inter-connected food chains. This results in a stable ecosystembecause if the population of one species changes, thereare alternative food sources for populations of otherspecies.

High Diversity:

Factors Affecting Pop lation Si e


23/34


4/15/12

Factors Affecting Population Size

Many different factors interact to determine

population size, and it can be very difficult todetermine which factors are the mostimportant.

Factors can be split into two broad group:abiotic factors and biotic factors.

Well look at 7 different factors.


24/34

4/15/12

1. Abiotic Factors

The population is obviously affected by theabiotic environment such as: temperature;water/humidity; pH; light/shade; soil(edaphic factors); mineral supply; current

(wind/water); topography (altitude, slope,aspect); catastrophes (floods/fire/frost);pollution. Successful species are generally

well adapted to their abiotic environment.In harsh environments (very cold, very hot,very dry, very acid, etc.) only a few specieswill have successfully adapted to theconditions so they will not have much

2 S


25/34

4/15/12

2. Seasons

Many abiotic factors vary with the seasons, and this can

cause a periodic oscillation in the population size.

This is only seen in species with a short life cycle comparedto the seasons, such as insects. Species with long life

cycles (longer than a year) do not change with the seasonslike this.


26/34

4/15/12

3. Food Supply

A population obviouslydepends on the population ofits food supply: if there isplenty of food the populationincreases and vice versa.

For example red deerintroduced to an Alaskanisland at first showed a

population increase, but thislarge population grazed thevegetation too quickly for theslow growth to recover, so thefood supply dwindled and thedeer population crashed

4 I t ifi


27/34

4/15/12

4. InterspecificCompetition

Interspecific competition is competition forresources (such as food, space, water, light,etc.) between members of different species,and in general one species will out-competeanother one.

This can be demonstrated by growing twodifferent species of the protozoanParamecium in flasks in a lab. They both

grow well in lab flasks when grownseparately, but when grown togetherP.aurelia out-competes P.caudatum for food,so the population ofP.caudatum falls due to

interspecific competition:


28/34

4/15/12

Interspecific Competition

5 Intraspeci ic


29/34

4/15/12

5. . Intraspeci icCompetition

Intraspecific competition is competition

for resources between members of thesame species. This is more significantthan interspecific competition, sincemember of the same species have the

same niche and so compete for exactlythe same resources.

Intraspecific competition tends to have astabilising influence on population size. If

the population gets too big, intraspecificpopulation increases, so the populationfalls again. If the population gets toosmall, intraspecific population decreases,so the population increases again:


30/34

4/15/12

Intraspecific Competition

Intraspecific competition is also the driving force behindnatural selection, since the individuals with the bestgenes are more likely to win the competition and pass on

their genes.Some species use aggressive behaviour to minimise realcompetition. Ritual fights, displays, threat postures areused to allow some individuals (the best) to reproduceand exclude others (the weakest). This avoids real fights

or shortages, and results in an optimum size for a

6 Predation


31/34

4/15/12

6. PredationThe populations of predators and their prey

depend on each other, so they tend to show

cyclical changes. This has been famouslymeasured for populations of lynx (predator) andhare (prey) in Canada, and can also bedemonstrated in a lab experiment using twospecies of mite: Eotetranchus (a herbivore) andTyphlodromus (a predator).

If the population of the prey increases, thepredator will have more food, so its populationwill start to increase. This means that more preywill be eaten, so its population will decrease, socausing a cycle in both populations:


32/34

4/15/12

Predation


33/34

4/15/12

7. Parasitism and Disease

Parasites and their hosts have a closesymbiotic relationship, so their populationsalso oscillate.

This is demonstrated by winter moth

caterpillars (the host species) and wasplarvae (parasites on the caterpillars).

If the population of parasite increases, they

kill their hosts, so their populationdecreases. This means there are fewer hostsfor the parasite, so their populationdecreases.

This allows the host population to recover,


34/34

4/15/12

Parasitism and Disease

3. ecosystem measurement

Documents