CONCEPTS OF BIOGEOCHEMICAL CYCLES
ARIZONA STATE UNIVERSITY
ABS 370 - ECOLOGY
SPRING 2024
Everything on earth, both living and non-living things, is composed of matter. This
material is composed of, among others: carbon (C), oxygen (O), nitrogen (N), hydrogen (H),
sulfur (S) and phosphorus (P). These chemical elements are utilized by producers to form
organic matter with the help of solar energy or energy derived from chemical reactions. The
organic matter produced is a source for organisms. The process of eating or being eaten in the
food chain results in the flow of material from other links in the chain. Even if a creature in
the food chain dies, the flow of matter continues. Because the dead living things are
decomposed by decomposers which will eventually enter the next food chain again. And so
on and so forth, forming an energy flow and material cycle.
A.
DEFINITION OF BIOGEOCHEMICAL CYCLES
Biogeochemistry is the continuous exchange or change between the living and non-living
components of the biosphere. In an ecosystem, material at each trophic level is not lost.
Material in the form of the constituent elements of organic matter is recycled. These elements
enter the biotic components through the air, soil and water. The recycling of these materials
involves living things and rocks (geophysical) so it is called the biogeochemical cycle (Figure
5.1.). The function of the biogeochemical cycle is as a material cycle that involves all
chemical elements that have been used by everything on earth, both biotic and abiotic
components, so that the biogeochemical cycle is called the biogeochemical cycle (Figure
5.1).
survival on earth is maintained.
1.
Water Cycle
Water in the atmosphere is in the form of water vapor. Water vapor comes from water on
land and sea that evaporates due to the heat of sunlight. Most of the water vapor in the
atmosphere comes from the ocean because the ocean covers 3/4 of the Earth's surface area.
Water vapor in the atmosphere is condensed into clouds that descend to the land and sea in
the deep form of rain. Rainwater on land enters the ground to form surface water and
groundwater.
Land plants absorb water in the soil. In the plant body water flows through a vessel. Then
through transpiration water vapor is released by plants into the atmosphere. Transpiration by
plants accounts for 90% of evaporation in terrestrial ecosystems. Animals obtain water
directly from surface water and from the plants and animals they eat, while humans use about
a quarter of the groundwater. Some water leaves the bodies of animals and humans as urine
and sweat.
Groundwater and surface water partly flow into rivers, then into lakes and into the sea.
This cycle is called the Long Cycle. While the cycle that begins with the process of
Transpiration and Evapotranspiration of water on the earth's surface, then followed by
Precipitation or the descent of water to the earth's surface is called the Short Cycle (Figure
6.2.).
The reciprocal processes of photosynthesis and cellular respiration are responsible for the
main changes and movements of carbon. Seasonal ups and downs in atmospheric CO2 and
O2 are caused by decreases in photosynthetic activity. On a global scale the return of CO2
and O2 to the atmosphere through respiration almost balances their removal through
photosynthesis.
But burning wood and fossil fuels adds even more CO2 to the atmosphere. As a result,
the amount of CO2 in the atmosphere increases. Atmospheric CO2 and O2 also move into
and out of aquatic systems, where they are involved in a dynamic equilibrium with other
forms of inorganic matter.
2.
Nitrogen Cycle
In nature, Nitrogen exists as organic compounds such as urea, proteins, and nucleic acids
or as inorganic compounds such as ammonia, nitrite, and nitrate.
First stage
Nitrogen cycling is the transfer of nitrogen from the atmosphere into the soil. In addition
to rainwater carrying some nitrogen, nitrogen addition to the soil occurs through the process
of nitrogen fixation. Biological nitrogen fixation can be done by Rhizobium bacteria that are
symbiotic with legumes, Azotobacter and Clostridium bacteria. In addition, blue green algae
in water also have the ability to fix nitrogen.
Second stage
Nitrate produced by biological fixation is used by producers (plants) to convert into
protein molecules. Furthermore, if the plant or animal dies, decomposing creatures break it
down into ammonia gas (NH3) and water-soluble ammonium salts (NH4+). This process is
called ammonification. Nitrosomonas bacteria convert ammonia and ammonium compounds
into nitrate by Nitrobacter. When oxygen in the soil is limited, nitrate is quickly transformed
into nitrogen gas or oxides of nitrogen by a process called denitrification.
3.
Sulfur Cycle
In this cycle oxidation (O2) and reduction (R) events occur, which are key to the exchange
of available SO4 reserves with iron sulfide reserves contained in the soil as a reserve supply.
Microorganisms at play:
H2S => S => SO4 sulfur bacteria (colorless, green, purple)
SO4 => H2S (anaerobic) : disulfovibrio bacteria
H2S => SO4 (aerobic) :thiobacilli bacteria S => SO4 and H2S (aerobic and anaerobic):
heterotroph bacteria S and N cycles are heavily influenced by the population of factory
smoke and the burning of fossil fuels. SO2 will affect photosynthesis while NO2 will affect
animal respiration. Also NO2 in the presence of ultraviolet light will react with unburned
hydrocarbons (from cars) and result in a painful photochemical haze, this is the synergistic
effect of NO2, with ultraviolet light.
Sulfur is present as inorganic sulfate. Sulfur is reduced by bacteria to sulfide and is
sometimes present as sulfur dioxide or hydrogen sulfide. Hydrogen sulfide is often lethal to
aquatic life and is generally produced from the decomposition of dead organic matter.Plants
absorb sulfur in the form of sulfate (SO4).
The transfer of sulfate occurs through the food chain process, then all living things die
and will be decomposed into their organic components by bacteria. Several types of bacteria
are involved in the sulfur cycle, including Desulfomaculum and Desulfibrio, which reduce
sulfate to sulfide in the form of hydrogen sulfide (H2S). H2S is then used by anaerobic
photoautotroph bacteria such as Chromatium and releases sulfur and oxygen. Sulfur is
oxidized to sulfate by chemolithotroph bacteria such as Thiobacillus.
4.
Phosphorus Cycle
Phosphorus is a scarce element compared to nitrogen. in water P:N2 = 1:23, tillage in the
USA over 50 years reduces phosphorus content in the form of P2 O5 by 36 %
Phosphorus is an essential element in life because all living things need phosphorus in
the form of ATP (Adenosine Tri Phosphate), as a source of energy for cell metabolism.
Phosphorus is found in nature in the form of phosphate ions (PO43-). Phosphate ions are
found in rocks. The existence of erosion and weathering events causes phosphate to be
carried to the river to the sea to form sediments. The movement of the earth's floor causes
sediments containing phosphate to surface. On land, plants take up phosphate dissolved in
groundwater.
Herbivores get phosphate from the plants they eat and carnivores get phosphate from the
herbivores they eat. All animals excrete phosphate through urine and feces. Bacteria and
fungi break down inorganic materials in the soil and release phosphorus, which is then taken
up by plants.
B.
BASIC TYPES AND PATTERNS OF BIOGEOCHEMICAL CYCLING
Chemical elements including protoplasmic elements tend to form a cycle in nature with a
special pattern: environment =>organism
=> environment, and this cycle is known as the biogeochemical cycle. The flow of elements
and compounds necessary for life is simply called the food cycle
For each cycle, a compartment (pool) will be found:
a.
Reserve pool: large and slow-moving, generally consisting of non-biological
components.
b.
The exchange pool or circulation pool is a smaller, but more active part that moves
back and forth rapidly between the organism and the environment.
In terms of the biosphere as a whole, the biogeochemical cycle consists of two basic groups:
A.
a type of gas whose reserves are in the atmosphere or hydrosphere.
B.
Sedimentary type where the reserves are located in the earth's crust
Gas-type cycling is more complete than sediment-type because P and Fe tend to be
disturbed, both of which are abundant in the pool.
Humans can affect the cycle of elements because they can change the perfect cycle
(cyclic) into an imperfect cycle (acyclic), for example, mining of P elements will disrupt the
cycle of unwise use of fertilizers which can lead to eutrophication and can reduce water
quality.
The goal of natural resource protection is to make acyclic processes cyclic. Resikling is a
good place to start improving the elemental cycle because resikling will control nutrients in
the water.
C.
QUANTITATIVE ASSESSMENT OF THE BIOGEOCHEMICAL CYCLE
The speed of exchange or transfer of elements from one place to another is more
important in determining the structure and function of the ecosystem than the amount present
at a place at a time To understand the role of the material cycle, the speed of circulation of
substances must be quantified. The speed of substance cycling can be determined using
tracers and monitoring techniques and remote sensing.
The use of isotopes for tracers, for example using P32 and Ca45, generally P does not
move smoothly and evenly from organisms. Some P will be bound to organisms or rocks, the
speed of P uptake by organisms is influenced by temperature, season and organism activity,
for example during the growth period P uptake will be rapid.
Irregular fertilization of ponds with P fertilizer can affect productivity because certain
organisms have been adapted to typical P requirements. Continuous over-fertilization can
result in species changes Botryococcus braunii thrives at a P concentration of 89 mg/m3
while Nitzchia palae thrives at a P concentration of 18 mg/m3.The increase in P from 18
mg/m3 to 89 mg/m3 means the replacement of Botryococcus with Nitzchia.
1.
Recycling Path
The two nutrient recycling pathways in the food chain are as follows:
a.
Returns via the animal excretory pathway.
b.
Returns through microorganism and detritus decomposition pathways.
Both pathways function in the ecosystem. Recycling pathway 1 is expected to be
dominant in plankton and other communities where the main energy flow is through the grass
food chain. In contrast, reverse circulation pathway 2 is dominant in grasslands, temperate
forests and other communities, where the energy flow pathway is through the detritus food
chain. Pathway 3 involves direct plant-to-plant cycling through symbiotic microorganisms.
SPECIES AND INDIVIDUALS IN ECOSYSTEMS:
Ecologists generally consider increasing ecosystem species richness to increase
productivity, stability, and resilience. Results from long-term field experiments suggest that
although species richness and interspecies competition result can lead to fluctuations in
individual species of populations, diversity tends to increase overall ecosystem productive
stability. Changes in biomass production by some species are associated with distinct changes
in biomass production of other species. In other words, a large number of species act as a
buffer against productivity reductions in any one species.
Several components of species diversity determine the effects in an actual ecosystem.
These include the number of species, their relative abundance, the particular species present,
interactions among species, and spatial and temporal variation. Current knowledge of the
consequences of biodiversity loss in actual ecosystems is limited, especially when
considering large changes in ecosystems and biodiversity.
Species extinction is the most concrete example of biodiversity loss. A species becomes
extinct when the last member dies. A species becomes extinct in the wild when the only
living individuals of the species are kept in an unnatural environment, such as a zoo.
Ecological theory suggests that several factors contribute to the vulnerability of certain
species. Species most vulnerable to extinction include large organisms; species high in food;
species with small population ranges or population sizes; species that have evolved in
isolation; species with little experience of disturbance; species with poor dispersal or
colonization abilities; migratory species, and species nesting or reproducing in colonies.
A.
CONCEPT OF HABITAT AND ECOLOGICAL NICHE
An organism's habitat is the place where the organism lives or where humans can find
the organism. Ecological niche, on the other hand, is a more inclusive term, which includes
not only the space or place an organism lives in, but also its role in the community, such as its
position on the food trophic level and its position on the environmental gradient: temperature,
humidity, pH, soil, and other existing conditions.
Three aspects of ecological niches, including :
1.
Habitat niche (spatial niche, habitat niche)
2.
Food level niche (trophic niche)
3.
Multidimensional niches ( multidimensional niche, hypervolume niche)
The ecological niche of an organism depends not only on where it lives, but also on
what it does (how it converts energy, behaves, reacts, changes the physical and biological
environment) and how it is inhibited by other species.
Analogies:
organism habitat = address
organism niche = profession (job title)
Habitat can also mean where the community lives. In this case, habitat includes only the
abiotic environment. But it can also involve both biotic and abiotic environments, for
example, the habitat of Trillium plants is in moist and shady places in the rainforest.
The concept of niche was developed by Charles Elton (1927), a British scientist, to
mean "the functional status of an organism in a particular community". In studying an
organism, we must know its activities, especially regarding its sources of nutrients and
energy, the speed of its metabolism and growth, the effect on other organisms when side by
side or in contact, and to what extent the organism we are investigating affects or is able to
change various processes in the ecosystem.
A niche is the position or status of an organism in a particular community and
ecosystem, which is the result of structural adaptations, physiological responses and specific
behaviors of that organism. So the niche of an organism is not only determined by where the
organism lives, but also by the various functions it has. It can be said, that biologically,
niches are the profession or way of life of organisms in their environment.
Knowledge of an organism's niche is necessary as a basis for understanding the
functioning of a community and ecosystem in the main habitat. To be able to distinguish the
niche of an organism, it is necessary to know about population density, collective
metabolism, the influence of abiotic factors on organisms, the influence of one organism on
another.
Many organisms, especially animals, have distinct stages of life development,
successively occupying different niches. For example, mosquito larvae live in shallow water
habitats, while adults occupy completely different habitats and niches.
Bird niches are fruit or seed eaters, caterpillar or ant eaters, fish or frog eaters. There are
general and specific niches. For example, chickens have a general niche because they can eat
worms, rice, meat, fish, grass and others. Chickens are polyphagous, which means they eat
many species. Eating several species is called oligophagy, eating only one species is called
monophagy such as leafhoppers, eating only rice.
If two or more animals have the same niche in the same habitat, there will be
competition. In intense competition, each species increases the efficiency of its way of life,
and each will become more specialized, i.e. its niche narrows. However, as the population
increases, competition between individuals within the species will also occur. In this
competition, weak individuals will be pushed to the margins of the niche. The effect is that
the niche widens, and the species becomes more generalist. This means that the species
becomes weaker or stronger. The more specialized a species is, the more vulnerable it is.
The concept of niches is a new concept. Let us review the analogy above: "if we want to
get acquainted with someone, we must first know his address, then to get to know more we
must also know about his position, interests, friends, his role in the environment."
Likewise with organisms, knowing their habitat is just the beginning of the introduction.
To determine the status of an organism in its natural environment, we must know its
activities, diet, energy sources, metabolism, growth, and its effect on surrounding organisms
and its ability to influence its environment. The morphological size of body organs can be
used as an index in comparing the niches of plants and animals.
In his research, Van Valen found that the length and width of a bird's beak is closely
related to its diet and this describes the index of niche width. The coefficient variation of beak
width was found to be influenced by nich width (variation in occupied habitat and variation
in diet).
Within the same species, competition will be greatly reduced if developmental stages
have different niches, for example, hunters eat plants (herbivores) while adult frogs are
insectivores. Differences in niches can also occur between male and female sexes, for
example, male and female woodpeckers (Dendrocopus) have beaks that are not the same size,
indicating that eating habits are different, so niches are different. In niches and many insects,
the body size of males and females is different, where males are larger than females because
the niches are also different.
B.
ECOLOGICAL EQUIVALENT
Organisms that occupy the same place or the same ecological niche in different
geographic regions are called ecological equivalents. Species with equivalent niches tend to
be taxonomically related when they occur in close proximity but often lack taxonomic
relatedness when they occur far apart from each other.
The species composition of communities differs greatly across geographical regions but
similar ecosystems can develop anywhere provided the physical habitat is similar, regardless
of geography. Ecological equivalent niches consisting of biological groups make up the flora
and fauna of these regions.
The ecosystem type of grasslands will develop where there is a grassland climate,
regardless of geography, but the species of grasses and grazers may differ especially if they
are far apart. Examples of grassland animals:
Table 7.1
North America
Eurasia
Africa
Australia
Bison
Antilope saga
Zebra
Kangaroos
Proghorn antilope
Wild horses
Assortment of antilopes
It says: Australian kangaroos are the ecological equivalent of North American bison and
pronghorn antelope.
C.
CHARACTER DISPLACEMENT: SYMPATRY AND ALLOPARTY
Species that occur in different geographic regions or separated by barriers are called
allopatric, while species that occur in the same regions (but not the same niches) are called
sympatric. Differences in closely related species are often more pronounced (i.e. divergent) in
sympatric populations and less pronounced (i.e. convergent) in allopatric populations. This
process of evaluation is known as character displacement. Browen and Wilson explain the
phenomenon of character displacement as follows:
" Two related species have overlapping habitat areas. In non-overlapping habitat areas (p and
q), populations of species A and B are very similar and may even be difficult to distinguish.
In overlapping habitat areas (r) where populations of species A and B occur together,
populations A and B are more divergent and can easily be distinguished because they have
different characteristics, such as different morphological behavior or physiology. Differences
For example, morphology in the beak will reduce overlap in food niches. Behavioral
differences will reduce interbreeding (remember Darwin Finches in the Galapagos Islands)"
D.
NATURAL SELECTION: FORMATION OF ALLOPATRIC AND SYMPATRIC
SPECIES
Species is a natural biological unit that has the same gene pool or species is a closed
genetic system. Species or species formation and species variety development can occur if
gene flow in the gene pool is blocked by an isolation mechanism. If isolation occurs due to
geographic separation, populations derived from the same ancestor will produce new species
that are allopathic (allopatric speciation).
If species occur due to ecological barriers or through genetic factors in the same area,
it will be able toproduce new species that are sympatric (sympatric speciation). The
mechanism of the emergence of new species is mainly due to the existence of allopatric
species, that is, if two population groups of one species that can interbreed are then separated
due to volcanoes or islands, so that the two groups cannot interbreed and because of
adaptation, they will eventually become two new species.
Example:
Darwins finches in the Galapagos Islands have a variety of beak shapes and body sizes.
Differences in shape beak and describe the different niches of an insect-eating round beak, a
seed-eating strong thick beak, and so on.
-
An example of genetic isolation in plants is :
Polyploidy (more than 2n chromosomes) will inhibit hybridization.
-
An example of rapid natural selection is :
What is known as industrial melanism or industrial blackening is the development of black
butterflies due to the environment, black becomes dominant due to factory fumes that can kill
lichens that give a whitish color to tree trunks. The loss of lichens causes the whitish color to
disappear and black becomes dominant, resulting in white butterflies being selected by
predators because they look more obvious.
E.
ARTIFICIAL SELECTION
Selection by humans with the aim of adapting plants and animals to their interests is
called artificial selection. Domestication of plants and animals does not only involve genetic
domestication of species, because of the mutual adaptation between domesticated species and
their keepers (domesticators) who are usually humans.
In domestication, there are actually two pathways of influence, which can bring about
changes (ecological and social, even genetic) in both humans and the organisms being reared.
Like maize and humans, where maize depends on humans, but conversely humans also
depend on maize. People who depend on maize will have The culture is different from that of
a society that depends on livestock. So the question "who is the slave of whom?" is the same
between humans and machines.
Domestication is a distinctive type of mutualistic relationship and is particularly
important because it can cause fundamental changes to the ecosystem. Humans and their
cattle can destroy the environment by overgrazing unless the relationship is one of mutualism
and not exploitation. Also, some big and bad problems arise due to domestics of plants or
animals that are released into the wild and turn into pests.
F.
BIOLOGICAL CLOCK
What is meant by biological clock (biological clock) is the ability of organisms to
measure their physiological time. The most common is the manipulation of circadian rhytm
(daily rhythm, circa: approximately; dies: day) or the ability to repeat events every 24 hours
even without the guidance of sunlight. Other events are those related to lunar periodicity
(which regulates tides) and seasonal cycles.
Organisms have a physiological mechanism for measuring time, known as a biological
clock. In general, the daily biological clock is the ability to determine the time and repeat
functions at every 24-hour interval even in circumstances that do not depend on the presence
of signs of physical factors such as sunlight. Biological clocks are also associated with
periodicities related to the moon and seasonal cycles.
The existence of certain "abilities" that are considered beneficial for an organism invites
the organism to be domesticated to a place that is thought to be suitable. Many of the
domesticated organisms are eventually cultivated and gradually undergo a change so that they
may end up being different from their original nature.
Domestication, whether in animals or plants, does not only involve the genetic
domestication of a species, but also the "mutual adaptation" between the domesticated species
and the domesticators, which are usually humans. Therefore, there are actually two
interplaying pathways that can lead to changes (ecological, social and even genetic) in
humans and the organisms they keep. However, if the domestication effort is done carelessly,
it can lead to big problems, with the uncontrolled release of domesticated organisms into the
wild and turning them into pests.
There are two theories regarding the mechanism of the biological clock:
1.
The endogenous time hypothesis is that clocks are contained within organisms and can
measure time without environmental cues.
2.
The external time hypothesis is that the clock is in the body of the organism whose
occurrence is regulated by signs from the environment.
However, the advantage of biological clocks is undoubted as they combine
environmental rhythms with the physiology of the organism to anticipate daily, seasonal and
other periodicities based on light, temperature or tides.
Example:
1.
Circadian rhytem: night animals (nocturnal) and day animals (diurnal). When a
nocturnal animal is placed in a laboratory that is kept dark, the daily rhythm
continues, just not 24 hours, but there are slight differences. Temperature changes
have little effect on the daily rhythm.
2.
Fish and bird migration.
3.
Evening sleep cycle (niktinasti).
G.
BASIC BEHAVIORAL PATTERNS
Behavior can be thought of as a complex of 8 components whose importance varies
depending on the organism:
a)
Tropism
b)
Taxis
c)
Reflex
d)
Instinct
e)
Learning
f)
Reasoning
Tropism occurs in organisms without a nervous system while taxis, reflexes, instincts,
learning and reasoning occur in organisms with a nervous system. The behavior of organisms
will affect population habitat selection, aggregation, predator-prey interactions, and so on.
•
Tropism:
Tropism is the movement of plant parts whose direction of movement is influenced by the
direction of stimulation. Tropism comes from the Greek word trope, which means turning. If
the movement is close to the direction of the stimulus is called positive tropism while if the
response motion away from the direction of the stimulus is called negative tropism.
Example:
a.
the motion of the plant stem towards the light,
b.
the motion of plant roots to the center of the earth,
c.
root movement towards water, and
d.
the twisting motion of the tip of the stem or tendril in vascular plants.
•
Taxis:
Taxis is the movement of moving part or all of the plant due to stimuli. Motion taxis
generally occurs in low-level plants. Taxis motion is divided into two kinds, namely:
1.
Phototaxis
Taxis caused by light stimulation is called phototaxis. Phototaxis motion occurs in green
algae Chlamydomonas directly towards the light of moderate intensity. But if the light
intensity increases, it will reach a certain limit where Chlamydomonas will suddenly reverse
direction and swim away from the light. Thus there is a change from positive phototaxis
motion to negative phototaxis motion. This can occur due to changes in light intensity, ie
plants will approach the light before exceeding its tolerance limit and will move away when it
has exceeded its tolerance limit.
2.
Chemotaxis
In addition to light, there are also other substances that can function as taxis motion
stimuli. Oxygen bacteria generally move to places that produce or contain a lot of oxygen.
Examples of taxis motion also occur in the gamete cells of moss plants. Spermatozoids in the
archegonium also move because they are attracted by sucrose or malic acid. This movement
occurs due to the presence of chemicals in the female gamete cells. This chemical-induced
taxis is called chemotaxis.
•
Instinct
Instinct is a pattern of behavior and reaction to a particular stimulus that is not learned
but has been there since the beginning of time birth of a living creature and are acquired
over generations (phylogenetic). Instincts are also stereotypical behaviors such as nest
building, food gathering, mating, protecting offspring, acquired without being learned.
•
Learning and reasoning
Related to the size of the brain, especially the cerebral cortex in primates.
Succession:
A.
SUCCESSION ECOLOGY
Ecosystem development, known as ecological succession, can be described by the
following three parameters:
a.
It is a process of community development that involves changes in the structure of
species and processes within the community in relation to time and the direction of
development is predictable.
b.
It is the result of modification of the physical environment by the community. So
succession is the regulation of the community, provided that the physical environment
determines the pattern of speed of change and limits the extent to which the community
can evolve.
c.
Eventually it reaches the top of the ecosystem where biomass is maximum and symbiotic
functions are maintained.
The sequence of communities that replace each other in an area is called a sere.
Transitional communities are called seral stages or developmental stages or pioneer stages.
The last stable system is called the climax.
Species replacement in sere occurs due to the tendency of populations to change or
modify the physical environment so that The situation is comfortable for other populations
and eventually a balance between the biotic and abiotic environment can be achieved.
1.
Bionergetics Ecosystem Development
In the early stages of ecological succession the rate of primary production or total
photosynthesis (P) exceeds the community respiration rate (R) so that P/R is greater than 1.
As long as P is greater than R there is an increase in biomass B.
If P/R < 1 is called heterotrophic succession If P/R > 1 is called autotrophic succession
2.
Diversity and Succession
As succession progresses, the variety of species increases but the dominance of one
species over another increases Other species are decreasing. The larger the size of the
organism, the longer its general length and the more complex its life cycle, the greater the
interspecific competition will cause a tendency to decrease the number of species that can
inhabit an area. In the bloom stage, the population size of organisms tends to be small and the
life cycle is simple and the development is fast. The increase in species variety in succession
is influenced by the increase in biomass and the increase in competence.
According to Margalef (1963), the number of species increases until mid-succession and
then decreases until climax. Genetic diversity includes variation in genetic material, such as
genes and chromosomes. Species (taxonomic) diversity is mostly interpreted as variation
among and within species (including human species), including variation in taxonomic units
such as phylum, family, genus etc.
Genetic diversity is the starting point in understanding the dimensions of biodiversity
issues, but at the species and ecosystem level forestry has a major influence.
Ecosystem diversity or even called biogeographic diversity is concerned with variation
within biogeographic regions, landscapes and habitats. We must realize that biodiversity is
always concerned with the variability of living things within a specific area or region.
3.
Succession Pressure: Quantity versus Quality
Species with high reproductive and growth rates are more likely to thrive in the early
stages but conversely in the late stages with selection pressure, species with low growth
potential but with great competition will be more profitable and more viable.
Communities consisting of various populations are dynamic in their interactions, which
means that ecosystems undergo changes over time. The progression of an ecosystem towards
maturity and equilibrium is known as ecological succession or succession.
Succession occurs as a result of modifications to the physical environment within a
community or ecosystem. The process of succession ends when a community or ecosystem
climaxes or has reached a state of equilibrium (homeostatis).
There are two kinds of succession in nature, primary succession and secondary
succession.
a.
Primary succession
Primary succession occurs when the original community is disturbed. This disturbance
results in the complete loss of the original community so that a new habitat is created in its
place. This disturbance can occur naturally, such as landslides, volcanic eruptions, new silt
deposits at river mouths, and sand deposits on beaches. Disturbance can also be man-made,
such as mining for tin, coal and petroleum.
An example found in Indonesia is the formation of succession on Mount Krakatau, which
erupted in 1883. In the area where Mount Krakatau erupted, pioneer plants such as lichens
and mosses that are resistant to sunlight and drought first appeared. The pioneer plants began
to weather the surface area of the land, so that simple soil was formed. When pioneer plants
die, they will invite decomposers to come. Substances formed due to decomposition activities
mix with the results of land weathering to form a more complex soil. With this soil, seeds that
come from outside the area can grow well. Then drought-resistant grasses grow. At the same
time, herbaceous plants grow to replace the pioneer plants with overshadowing it. Such
conditions do not make pioneers fertile but the opposite.
Meanwhile, grasses and shrubs with their strong roots continue to weather the land.
Dead plant parts are decomposed by fungi so that the soil becomes thicker. Then shrubs
grow. The shrubs shade the grass and shrubs, so there is competition. Over time the shrubs
become dominant and then the trees push the shrubs so that a forest is formed. That's when
the ecosystem is said to reach equilibrium or it is said that the ecosystem reaches a climax,
that is, the changes that occur are so small that they do not change the ecosystem much.
b.
Secondary Succession
Secondary succession occurs when a community is disturbed, either naturally or
artificially. The disturbance does not completely destroy the place where the organisms grow
so that the old substrate and life are still present in the community. Examples of natural
disturbances include floods, ocean waves, fires, strong winds, and artificial disturbances such
as deliberate logging of forests and burning of grasslands.
Examples of communities that give rise to succession in Indonesia include moorlands, alang-
alang fields, scrub former fields, and abandoned rubber plantations. Plant succession is the
replacement of one plant community by another. It can occur at a slow stage of integration
when the original growing site is so hard that few plants can grow on it, or it can occur very
quickly when a community is destroyed by a factor such as fire, flood, or insect epidemic and
replaced by another (Daniel et al., 1992).
Change is continuous, a series of community development that is a series and leads to a
steady (stable) and permanent state called climax. Tansley (1920) defines succession as a
stage-by-stage change that occurs in vegetation on a tendency of an area on the earth's surface
from one population to another. Clements (1916) distinguished six sub-components: (a)
nudation; (b) migration; (c) excesis; (d) competition; (e) reaction; (f) final stabilization,
climax. Clements' description of succession still holds true. However, something may
emphasize other subprocesses, for example numerical changes in population life-form
integration or changes in genetic adaptation of populations in the evolutionary flow.
Succession is an orientation study that considers all changes in vegetation that occur in
the same habitat over time (Mueller-Dombois and Ellenberg, 1974). Furthermore, it is said
that there are two types of succession, namely primary succession and secondary succession.
The difference between these two types of succession lies in the habitat conditions the
beginning of the succession process. Primary succession occurs when the original community
is disturbed. This disturbance results in the total loss of the original community so that in
place of the original community, a new habitat is formed. Secondary succession occurs when
a natural community or ecosystem is disturbed either naturally or artificially and the
disturbance does not totally destroy the place where the organisms grow so that in the
community the old substrate and life still exist.
The rate of population growth and species composition is rapid in the early phase of
succession, then declines in subsequent development. Conditions that limit the rate of
population growth and species composition in the next stage are environmental factors that
are less suitable for supporting the survival of certain species (Marsono and Sastrosumarto,
1981).
B.
CONCEPT CLIMAX
The final stable community of sera is the Climax Community. A climax community is
self-organizing and in balance with the physical habitat.
Contrary to the community in development, there is no annual buildup of net community
organic matter in the climax community. This is because the annual production of the
community is in balance with the annual consumption.
For certain regions it can be recognized:
a.
Single climatic climax where there is a balance with the general climate of the area. A number
of edaphic climaxes that depend on the local conditions of the region.
Climatic climax is the theoretical community that all successions aim to develop in an
area provided that the physical environment does not greatly affect the environmental
climate. Generally succession will end at an edaphic climax where topography, soil, water,
fire, and other disturbances prevent a single climatic climax from developing.
Based on the idea of a single climax each region has only one climax to which all
communities will lead albeit slowly.
According to the idea of multiple climaxes, it is unrealistic to assume that a community in
a certain climatic region will end up in the same state if the physical habitat conditions are
more or less the same.
A compromise between these two views is to recognize a theoretical single climatic
climax and a number of edaphic climaxes that depend on variations in the physical habitat. In
other words an area will have theoretically one stable climatic climax but the area may have
stores of these conditions e.g. substrate, temperature, wind, sunlight that can give rise to
several edaphic climaxes.
If a community is stable for a place but is not a climatic climax or edaphic climax, it is
formed because of human or animal work is called disclimax or anthropogenic subclimax. For
example, overgrazing of animals can result in a sand community where the local climate would have
formed a grass community. This desert community is the disclimax of the shadow grassland which is
the climatic climax.
This type of desert community is evidence of poor human management. Because when a
desert community in an area with a desert climate is natural.
A plantation (agricultural) ecosystem that has been maintained (stabilized) for a long time
can be considered a climax (disclimax). Unfortunately many agricultural systems in the
tropics and irrigated deserts are not stable at all because they are constantly threatened by
erosion, nutrient leaching, salt deposition and insect and disease infestation.
C.
SUSTAINABLE ECOSYSTEM
Species adapt to each other and to their communities, forming niches. The development
of more complex structures allows a greater number of species to coexist with each other. An
increase in species richness and complexity acts as a buffer to the community from
environmental stress and disasters, making it more stable.
In some environments, succession reaches what is called a climax, resulting in a stable
community dominated by a few prominent species. This equilibrium level, called a climax
community, is the result of a complex web of biotic interactions. An example is the tropical
rainforest, which contains hundreds of species per hectare.
The relationship between species diversity and community stability sheds light on the
importance of maintaining the greatest possible richness in biological communities. A forest
contains recently introduced species in contrast to local species with rich interaction networks
that have adapted to each other. Undisturbed communities that are rich in species have the
resilience to continue ecosystem functioning.
Soerianegara and Indrawan (1988) mentioned that in the formation of climax there are
two differences of opinion, namely; monoclimactic understanding and polylimactic
understanding. The monoclimactic understanding assumes that in a climatic area there is only
one kind of climax, namely climatic climax formation or vegetation only. This means that the
climax is a reflection of the climate, because climate is the most stable and influential factor.
The poly-climactic view assumes that not only climatic factors, such as sunlight,
temperature, humidity and precipitation, can cause a climax. On the contrary, it is argued that
there are other factors that can also cause climaxes, namely edaphic and biotic factors.
Edaphic factors arise due to soil influences such as soil composition, soil moisture, soil
temperature and groundwater conditions. While biotic factors are factors caused by humans
or animals, for example grasslands and tropical savannas. For the polyclimactic group, the
mangrove forest is a separate climax, namely the edaphic climax with special soil conditions.
