LESSON 2 NATURAL SYSTEMS

Aim

Explain the concepts of natural systems.

ECOLOGY

Ecology is the study of the ways in which living organisms, including humans, interact with their

environment. Permaculture is sometimes called the ‘cultivated ecology’. Permaculturists aim to create

sustainable, stable and productive ecosystems.

The Ecosystem

An ecosystem is made up of abiotic substances (soil, water, air and their components), and biotic (living)

substances (known as producers, consumers and decomposers). The producers are the plants. They

are the only organisms that are able to absorb and store energy from the sun. The other organisms (ie.

all animals) depend on the producers for their source of energy. Consumers are animals which eat

producers or other consumers. Decomposers are organisms that break down (rot) the structure of other

organisms when they die. Through the action of decomposers, nutrients are returned to the soil and

made available so that plants can use them over and over, and thus keep the cycle of life going. Diverse

interrelationships such as this exist in any ecosystem.

Constituents of the Ecosystem

These can be summarised as follows:

1. Abiotic Components

These are the physical features, plus the basic inorganic compounds of the environment, and include the

rocks, rivers, soil (not the plants and animals within the soil though), clouds, glaciers, etc.

They are identified as:

a) Inorganic substances - these are macro- and micro-nutrients, carbon dioxide (CO2), water (H2O),

hydrogen (H), soils, etc.

- these are all resources feeding into the ecosystem.

b) Organic compounds - proteins, carbohydrates, lipids.

- these are produced by autotrophs (see below) and provide a material link

between the biotic compounds.

c) Climate - elements such as light, temperature, humidity, wind and rain.

2. Biotic Components: The living organisms

a) Autotrophic components - Organisms which require only simple inorganic substances; they fix light (or

chemical) energy in simple organic compounds then use this stored energy to build up complex

substances.

Also known as PRODUCERS, the autotrophic organisms are largely green plants which are able to

manufacture the food they use from simple inorganic substances using light energy.

b) Heterotrophic components - Organisms which cannot manufacture the food they utilize. They

rearrange and ultimately decompose the compounds manufactured by autotrophs. There are two main

groups of heterotrophs.

1. CONSUMERS: Heterotrophs (animals) which ingest other organisms or particles of organic matter.

a. Primary Consumers - Feed on plants (herbivores - cattle, insects etc.)

b. Secondary Consumers - Primary carnivores feeding mainly on herbivores (eg. frogs, lizards etc).

c. Tertiary Consumers - Secondary or top order carnivores feeding mainly on other carnivores (eg.

snakes).

Some animals may be a combination of these, for example, humans are primary consumers when they

eat plants, and secondary consumers when they eat cattle (who have eaten grasses).

2. DECOMPOSERS: Heterotrophs (mainly bacteria and fungi) which break down complex compounds of

dead animals or plants absorb some of the products, and release simple inorganic substances useable

once more by the autotrophs.

Ecological Concepts

Knowing the basic components of an ecosystem leads also to knowledge of the basic ecological

concepts. Different authors might list concepts in different ways however the following are basic,

universally accepted, and essential to any ecosystem:

1. The sun is the source of all energy.

All energy in any organisms originally came from the sun. Other energies in the environment also

originated from the sun (eg. wind, tides, water cycle, light etc).

2. Everything is connected to everything else.

All living things interact with other things (both living and not living) in their environment.

The climate affects the living things in an area. The plants influence the insect population and the fish

eat the insects - and on it goes.

3. Everything must fit how and where it lives.

'Adaptation' is the key word of this concept (ie. unless a species adapts to a situation, it will not survive).

A principle related to this concept is the 'Dam Law'. The Dam Law states: 'die, adapt or move'.

4. Everything is going somewhere and becoming something else.

An ecosystem is dynamic; in a constant state of change. In death there is no waste matter: it is

continually recycled among biotic or abiotic components. Rocks are worn down into soil; soil is used by

plants, changed, moved and leached by the forces of the environment, etc.

5. There is no free lunch.

For every action there is a reaction. For every event there is a consequence. There is a delicate balance

of nature between producers and consumers which allows both to exist. If this inter-relationship becomes

and remains unbalanced, one or both members of the inter-relationship will die.

THE WEB OF LIFE

The interrelationships between the various aspects of the environment can be represented simply as:

CLIMATE - plants modify climate, climate affects plants and animals

PRODUCERS - animals eat plants

CONSUMERS - animal waste to soil

SOIL - soil eroded by animals and climate

DECOMPOSERS - decomposing animals and plants go into the soil.

Decomposed plant and animal material feeds new plants which in turn feed animals eating the plants.

These interrelationships can be represented by a WEB OF LIFE chart.

BIOMASS

Biomass is basically all biological matter mass, with respect to a particular part of the environment or part

of an organism.

Examples:

A tree could be regarded as having many biomass zones such as the trunk, the canopy, the roots and

the interface between the tree and the soil surface.

A forest’s biomass would incorporate trees, shrubs, all plants and animals, microbes, etc. In fact,

anything that can be regarded as biological (ie. living or once lived) which exists within the forest would

be part of its biomass.

Biomass is the term used to describe the mass of living matter (plant and/or animal including humans) in

a particular area. One of the principle goals of the permaculturist is to increase the productivity of their

system (i.e. to maximise the useable biomass produced).

Generally in most eco-systems the greatest percentage of the biomass consists of plants, with animals

often representing only a few percent of the total biomass. The total rate at which plants in an ecosystem

assimilate solar energy by photosynthesis is known as "gross primary productivity". Much of this is lost as

heat through respiration. The rate at which plants store energy in a form usable as food by other

organisms is known as "net primary productivity". It is measured in terms of the amount of organic matter

(food) that is produced per unit of time either in terms of mass (weight) or energy equivalent. For

example, it may be measured in dry grams per metre squared per day, or in calories per metre squared

per day.

Knowledge, therefore, of which plant and ecosystems types have the highest productivity can enable us

to decide which plants (crops) to grow and in what manner to gain the highest net productivity. We should

also, however, have an understanding of different ecosystem types to understand which factors in the

environment will limit the productivity of any particular ecosystem type.

CLIMATE

All plants are adapted to particular climatic conditions - therefore you should choose the plants to suit the

site where possible. In some instances however you can modify the site to provide more suitable

conditions, for example build dams to provide additional water for irrigation, or grow windbreaks for

protection.

NOTE: In many countries climatic data is often readily available from the Bureau of Meteorology (or

similar in your region) the bureau provides climatic data in a variety of forms that can be easily used to

determine growing conditions at potential fruit growing sites.

Temperature

All plants have a range of temperatures in which they will grow. Within this range is an optimum range

where the plants will give their best results. For example a particular plant may grow within the range 4 -

35ºC (39-95ºF) with an optimum range of 15-25º C (59-77ºF).

Maximum temperatures are generally not as critical as minimum temperatures. At high temperatures

plants may slow their growth to reduce water loss, whereas at low temperatures the plants may cease

growth or even die. As temperatures can vary quite significantly, from season to season and also from

day to night, you must consider the annual temperature cycle for your site. Use tables or maps that

indicate the average monthly maximum and minimum temperatures, to determine the potential growing

season for different plants at that site.

Frosts

Frosts can cause major damage to plants. Frost frequency depends on location and on local topography.

Frost conditions are most likely to occur on clear cold nights, with little or no wind, at inland sites or at

higher altitudes. It is least likely to occur in slightly elevated coastal areas, particularly where it is windy.

The likelihood of frost occurrence can be readily established from climatic records, and from talking with

locals. Newly planted trees are most vulnerable.

Wind

Wind is important to plant growth in a number of ways: the stronger the wind the greater the amount of

evaporation. Strong winds can physically damage plants. Slight winds on cold clear nights help prevent

frosts occurring. Sites subject to regular strong or gusty winds, hot dry winds, or very cold winds should

be avoided unless the site can be readily modified, for example by wind breaks.

Extreme hazards

Is the area subject to hail, snowfalls, thunderstorms, lighting or bushfires? These may be infrequent, but

they can do a lot of damage to both plants and to your home.

Microclimates

These are the environmental conditions that occur when local conditions modify the climatic

characteristics of an area, in some way, from the general overall climatic conditions of the area. These

local conditions or factors include the physical topography of the area (eg. hills, mountains, slopes, cliff

faces, gorges), local soil conditions (e.g. type, structure, depth), vegetation types and coverage, the

presence of water bodies (eg. rivers, streams, ponds, lakes), the action of animals (eg. animals digging

soil, animals eating vegetation), and man-made structures. Understanding how these local factors modify

the general climatic characteristics will enable the permaculturist to grow a much wider range of plants.

For example trees provide shade and maybe frost or sun protection, but can restrict light and reduce

growth rates (an advantage with some plants and a disadvantage with other plants).

Another example is that of hill-slopes. These will have a major effect on how much light a plant receives.

The amount of sunshine a hill-slope receives is dependant on its aspect and where it is situated (i.e.

country or hemisphere). In the southern hemisphere northerly facing slopes receive more sun than those

facing south. In the northern hemisphere this is reversed.

In the southern hemisphere, northeast facing slopes generally receive maximum direct radiation in the

morning, while north-westerly facing slopes receive their most radiation during the afternoon. Northwest

slopes therefore tend to heat up more slowly during the day than north-east ones, but will generally reach

a higher overall temperature, unless the slopes are shaded out by other topographical features. Northerly

slopes will generally be drier than adjacent southerly slopes due to the increased warmth. Steeper slopes

will receive the most radiation in winter, while lesser slopes will receive maximum radiation in summer.

The warmer northerly slopes are often used for fruit-bearing plants that require that extra bit of warmth

for ripening fruit. Taken over a whole year, in the UK the sunniest areas are found to be those that are flat

and on the coast.

The local topography will also have major effects on directing the passage of warm and cold air flows.

Generally cold air is denser than warm air, so the cold air tends to settle in low lying areas and

depressions. This can result in the creation of frost hollows, where cold air has collected at night.

Cold-air pockets can also collect, however, on flat mountain-tops, so don't think that frosty areas will

occur only in the lower areas. Upper slopes of valleys tend to be the most frost free areas. Topography

will also channel winds, and play the major role in determining the drainage characteristics of an area.

All of these local modifying factors need to be considered, when deciding what and where to plant.

Simply observing a site over an extended period (perhaps a year so that all seasons are observed) will

give you a lot on insight into local microclimates. Remember though that conditions can vary from year to

year also, sometimes considerably.

Typically different sites in the same locality can vary a great deal in their climatic characteristics and

suitability for growing various fruit producing plants.

A WARM SITE has an aspect which faces the midday sun (on a slope facing north in the southern

hemisphere). It will miss early and late season frosts which affect other parts of the locality because

cold air will fall into the valleys below.

Where a slope facing the midday sun is at a higher altitude, the advantages found normally are

counteracted by the cold which comes from being at a higher altitude.

A COLD SITE has an aspect facing away from the midday sun. It heats up less in summer because it

gets less direct sun. Being higher up the slopes it still may miss early and late frosts which drain into

the valleys below.

A VERY COLD SITE is a low spot in a valley which gets less direct sun than other sites and collects

frosts earlier and later in the season than other places.

AN AVERAGE SITE is flat. Frosts do not drain away as easily as on sloping ground. Sun is collected

in summer or winter at an average rate. If on top of a hill it will be warmer than part way down a slope.

NB: prevailing winds, shade from trees and buildings etc. can also affect the climatic characteristics of a

site.

Degree Days

One method of assessing the growing potential of a district is to measure the heat accumulated during

the season. From this, a base of 10 degrees Celsius is taken because below this temperature very little

plant growth occurs. The "base" figure of 10 degrees Celsius is then subtracted from the average

temperature for the month and the result is multiplied by the number of days in the month.

For example, if the average temperature is 17.5 degrees Celsius: degree-days for a 30 day month is

calculated as follows:

(17.5 - 10) X 30 = 225 degrees Celsius

Degree-days are useful for determining the suitability of various sites in a geographical area with similar

climatic patterns.

WATER

Water is the first of three key elements in any sustainable system the second being soil and the third

biodiversity. The world’s major water storage is in the soil (about 11%) not in catchments such as dams

and reservoirs (0.5%).

Water is a renewable resource within a fixed supply. The world's total amount of water has been

estimated at 1.35 x 10 to the eighteenth power cubic metres (or 1600 million-million litres). Most is in a

form unsuitable for human use, and there is uneven distribution around the world. About 97.2% is in salty

oceans or seas, and about 2.48% is in ice caps or glaciers, aquifers too deep to extract from, in the

atmosphere or in topsoil. Only about 0.32% is useable ground or surface water. Of this 99% is either too

expensive to get or in remote areas, or it is polluted. Only about 0.003% of the worlds total water supply

is usable. This provides about 12 million litres of usable water per person. The average daily use per

person, for example, in the USA (typical of developed nations) through direct personal use is about 700

litres, through direct agricultural use about 2300, through indirect agricultural use about 4000 litres, a total

of about 7000 litres per person per day.

There should be plenty of water for everyone, however three controlling factors:

Very unequal distribution,

Rapidly rising demand

Increasing pollution around urban and industrial areas.

This means that some areas of the planet are already using water at a greater rate than it is being

replenished. Water management will become increasingly important to try and cater for the increasing

demand for usable water.

The aims of permaculture systems:

Re-use water as much as possible before it passes out of the system.

Redirect water to prevent run-off from your property; build swales (ditches built along contours that

trap water on steep sites; plant in rip lines.

Harvest as much rain and runoff water as possible, primarily in the soil by increasing groundwater

storage (use mulch), and secondly in storage systems such as tanks, dams, constructed wetlands,

aquaponic systems (integrating hydroponics with re-circulating aquaculture) and solar aquatic ponds,

use of fungal systems for wastewater treatment.

Ensure that what water you do use and store is biologically cleansed and filtered throughout your

permaculture system.

Reduce personal consumption.

Do not consume more water then can be naturally replenished.

Water and Plant Growth

Water is a major component of plants and all other living things.

Generally less than 5% of the water taken in by the plant is used within the plant. In some cases the

amount used is as little as 1%.

The water remaining in the plant is used mainly in the cell tissue (which are 75 - 90% water) as a

carrier of foods and growth regulators from the leaves via the transport system (vascular system),

and in very small quantities as part of the photosynthetic process.

The remaining 95% or more acts as a carrier of nutrients through the plant, from the roots to the

leaves via the vascular system. What remains is then transpired into the atmosphere through the leaf

stomata (leaf pores), cooling the leaf canopy and reducing leaf burn or desiccation.

Transpiration

Plants need to transpire in order to grow. If either water supply is limited or other conditions are not

favourable then transpiration will be greatly reduced.

Evaporation from the crown of the plant is roughly proportional to the size of the crown.

Wind is the major cause of evaporation through reduced humidity around plant’s leaves.

Increasing temperature increases the rate of evaporation: During winter transpiration is generally

small, however in spring and early summer the amount of water transpired can be very large. High

soil moisture and increased light will also increase evaporation. On a sunny spring day, mature trees

can use more then 250 litres of water a day.

When there is adequate water in the soil, and conditions are favourable for evaporation at the leaf

surface, then water moves easily into the roots from the soil and up into the plant. As the soil dries the

water remaining in the soil is held more tightly to the soil particles. If evaporation through the leaf

continues and there is insufficient water in the soil to replace it, the plant will have water stress and wilt;

this may result in permanent damage or death.

Drought tolerant plants have adapted to survive without water but do not produce new growth during dry

conditions which limits harvests. In times of water shortage the leaf stomata may only open late at night

or early in the morning when humidity is high or dew is present. If water stress continues for a prolonged

period then the stomata may only open for short periods to allow the discharge of waste gases (eg.

oxygen) and to take in carbon-dioxide.

Too much water in the soil can also be a problem for healthy plant growth. While some plants are

adapted to growing in waterlogged soils or directly in water, the majority require sufficient levels of

oxygen in the root zone to maintain healthy growth. If a soil is poorly drained or floods, then the water will

displace all air in the soil, leaving insufficient oxygen for the plant roots to metabolise the carbohydrates

they require for energy and growth. The root tissue will die, the transpiration stream can’t then function,

and the plant will wilt from lack of water.

Minimising Plant Water Requirements

The watering requirements of your plants can be minimised in the following ways:

By choosing plant species and varieties that best suit the local climate.

By maintaining a well balanced fertile growing conditions (appropriate to the plants selected).

By watering (only if absolutely necessary eg. when first establishing plants) in the cool of the day

By using micro-irrigation systems eg. trickle systems where possible. These are much more efficient

in their use of water.

By slow, thorough watering. A thorough deep watering once or twice a week will be more effective

than light watering every day or two.

By avoiding watering on windy days.

By reducing excess evaporation. This can be achieved by keeping bare soil covered. Mulches, as

well as reducing weed growth will reduce evaporation. Compact groundcovers will slow evaporation

from the soil but they will use a lot of water themselves. Larger plants will shade the soil and limit

evaporation but they can make getting water to the soil in the first place rather tricky.

Arid Landscapes

To overcome shortage of water in arid landscapes the following points are worth considering:

Incorporate many small catchments and water storage strategies into the design.

Water should be stored in the ground and above the ground.

Placement of human and animal shelter close to water and to aid in the harvest of rainfall.

Check and repair dams, holding banks, irrigation systems - once a defect is noticed, fix it.

Utilise methods to collect runoff from roadways, paths, structures, etc.

Utilise mulch traps and condensation traps in deserts.

Clean and check slopes and runoff to storage areas.

Reduce evaporation loss and produce moisture barriers.

Recycle water.

Irrigation

Climate will influence the selection and design of the irrigation system. Criteria such as rainfall,

humidity, plant selection, growth stage, soil type, and wind all need consideration. Large masses of

water such as seas, oceans, lakes or dams will also modify microclimates (ie. temperature fluctuations

are less near large bodies of water). In permaculture systems water harvesting swales: contour

ditches, with an un-compacted earth mound on the lower side are typically used as a tree growing

system. Dams in areas of high evaporation are usually designed to be small in surface area, but deep.

Swales

Swales are frequently used in permaculture designs as a form of interception of run-off.

Swales are long, level excavations which vary in width built on contours or level survey lines. They are

designed to intercept water flow and hold it for a few hours to let it infiltrate deeper into the underlying

soil. Trees are essential in a swale system. Swales are usually used in arid regions, as well as in humid

districts for steep slopes.

Swales do not act as diversion channels for water. They are for holding water.

WASTE WATER TREATMENT (REED-BEDS)

The purification of waste (grey) water and effluents using reed-beds has been done for hundreds of

years. By allowing dirty water to pass through wetlands planted with reeds and rushes, the roots of

certain plants release oxygen which helps micro-organisms break down and filter out impurities. The

method can ultimately produce high quality water which may be suitable for drinking. The plant biomass

that grows in this system can also be harvested occasionally as a source of mulch.

Reed-beds may be naturally formed wetlands or artificially constructed and planted channels and beds.

Given the current degree of environmental pressure on the few natural wetlands remaining, it would

appear that further pressure on or usage of such wetlands is unwise. However, the deliberate building of

new, well-designed wetland/reed-beds could be a very useful enterprise.

Waste water normally contains a wide range of impurities in the form of solid particles or as dissolved

matter. Heavy metals, disease-causing pathogens, detergents and bulk nutrients are often present,

sometimes in high concentrations. These materials need to be removed if the water is to pumped back

into public water-ways or if it is going to be used for domestic applications.

When micro-organisms break down water pollutants, oxygen is used up. This oxygen consumption varies

with different materials as is known as the biological oxygen demand (BOD). For example, nutrient rich

wastes such as farm manures or silage effluent have a high BOD. When these pollutants find their way

into waterways, the oxygen level in the water becomes seriously depleted as a result of break down

processes causing parts of the natural flora and fauna of the waterway to die. When the water-body is

small and the flow rate is slow (eg. in conditions of low rainfall), this problem can be quite severe. The

blue-green species of Algae are then able to flourish, poisoning and fouling the water even further.

The problem of limited oxygen supply may be overcome by the use of 'flow-form' basins, pebble streams,

waterfalls, deep rock beds, etc. In this environment of plentiful oxygen, micro-organisms such as

bacteria, yeasts and fungi to become established and thrive on the surfaces of the pebbles or rocks and

consume the soluble polluting matter.

Alternatively, plants may be used to supply the oxygen necessary for micro-organisms to break down

these pollutants. Some plants, mainly reeds and rushes, absorb atmospheric oxygen through their leaves

and transfer it down hollow stems to their extensive root systems. The oxygen is then released through

fine root hairs into the soil where it helps build up micro-organism populations and facilitates the break

down of organic matter. Reed-beds work most effectively when a dense layer of rhizomes and root hairs

is formed. This may take about three years to fully develop.

The flow of water through a reed-bed may be either horizontal (across the soil and reeds) or vertical

(down through the reeds and soil). In both situations, the reed plants provide oxygen for the micro-

organisms. If the degree of pollution is only slight, horizontal flow reed-beds are adequate. A shallow

trench or pit about 60cm deep, lined with plastic sheeting and filled with gravel or porous soil can be

planted with species of Phragmites (eg. common reed); the waste water is allowed to pass through the

bed for purification. The process takes several days to remove most of the pollutants, including nitrates,

phosphates and some disease pathogens. A shallower version about 15cm deep and planted with Typha

species (bulrushes), have been used in the purification of acidic water from mining operations.

Vertical flow reed-bed systems consist of beds about 60cm deep filled with layers of different sized

gravels (larger material to the bottom) and a layer of sand on top. Appropriate reed species are planted

into this base. The beds are stepped or terraced, with an outlet pipe at the bottom of one bed draining

water into the reeds of the next bed. Generally, the waste water is pumped on flushes and allowed to

trickle down gradually before the next volume of water is applied. A thin layer of sludge gradually builds

up on the sand surface, eventually choking the system. The bed is then rested to enable the micro-

organisms to break down the excess organic matter. It is therefore necessary to have more than one bed

system when using the vertical flow method; while some are in use, the others are resting.

Solid materials can be fairly easily removed by settlement and filtration techniques. Separate gravel and

sand filter beds function well for this purpose.

While the reed-bed method is not really suited to cities or large-scale treatment plants because of the

excessive volume of waste produced, reed-bed treatment is very suitable for rural areas where on-farm

treatment plants can be established. Over 100 reed-beds have been built in the United Kingdom, some

as part of improved rural sewerage works, others for country houses and hotels, and still others for

treating waste water from farms, factories and mines. Reed-beds are ideal for treating the 'grey' water

from homes, although specialised systems are needed for treating toilet wastes. An area of about 5

square metres per person is generally sufficient for reed-beds on a small scale.

Some of the advantages of reed-beds over the more common mechanical waste water treatment

methods include:

Cheaper to install

Easier to install (low-tech)

Cheaper to run and maintain

Easier to maintain (low-tech)

Less energy required to run (gravity does the work)

Integrated with local environment

Biodiversity enhanced

Some weeding may be necessary in reed-beds, and vertical flow systems need to be alternately rested.

The low requirement for expertise (for installation and operation) means that reed-beds can be used by a

wide range of people, such as those in less developed districts or countries.

In a well planned permaculture system, the inclusion of waste water treatment techniques is an important

consideration, and reed-beds are a very good option. In addition to purifying water and providing mulch

materials, the artificial wetlands can be a home for a wide range of aquatic animals (including fish and

shellfish) and plants, a water source and habitat for birds and terrestrial animals and a pleasant place to

look at or explore for recreation. Planting trees which are tolerant of moist, nutrient-rich conditions,

adjacent to a reed-bed can further diversify the water treatment site.

Suitable Plants

A large range of aquatic plants are used in reed-beds, operating in different ways. Reed and rush species

which are used for enriching the soil with oxygen include Phragmites australis, Phragmites communis,

Schoenoplectus lacustris, Scirpus spp. and Typha latifolia (bullrush). These plants are essentially the

backbone of a good reed-bed system.

Species which are suitable for pathogen removal include Alisma plantago-aquatica (water plantain),

Juncus effusus, Iris pseudacorus (yellow flag), Mentha aquatica (water mint), Schoenoplectus lacustris

and Spartina species. Cyanide compounds, thiocyanates and phenols have been removed using Juncus

species.

Other plants which may be used in reed-bed systems include Carex spp., Eichornia crassipes (water

hyacinth), Glyceria maxima (reed Sweet grass), Lemna spp. (duck weeds), Nymphaea spp. (water lilies),

Pista sp. (water lettuce), Phalaris arundinacea (reed canary grass) and Symphytum officinale (comfrey).

Many other species can be incorporated into the system depending on the locality and prevailing climatic

conditions.

References:

*Gray, K. and Biddlestone, J. 1994 Go with the flow. The Garden. July: 302-303

*Mollison, B. 1988 Permaculture: A Designers' Manual. Tagari Publications, Tyalgum, NSW

*Morrow, R. 1993 Earth User's Guide to Permaculture. Kangaroo Press, Kenthurst, NSW

AQUATIC ENVIRONMENTS

Rivers, lakes, streams, wetlands, ponds etc are all aquatic, polyculture environments made up of

aquatic organisms such as plants, fish, birds, frogs, crustaceans and so on. These creatures are all

inter-dependant for food and food chains in the food web. Aquatic environments are natural or

cultivated, highly productive and sustainable ecosystems. Aquaculture is studied in detail in lesson 5.

SELF ASSESSMENT Perform the self assessment test titled ' test 2.1’ If you answer incorrectly, review the notes and try the test again.

THE HYDROLOGICAL CYCLE

It is easy to understand the importance of water to our lives so it can be an interesting exercise to see

how water is cycled through our environment. The diagram following entitled "The Hydrological Cycle"

shows what happens to the rainfall we receive.

The Hydrological Cycle

If we consider first the rainfall (precipitation) that we receive we can see from the diagram that three

things can happen:

i) The bulk of the rainfall falls onto the land surface.

ii) Some of the rain is intercepted (ie. something stops the rain from directly hitting the land surface, such

as vegetation.

iii) Some of the rain falls directly into water bodies (eg. creeks, rivers, lakes, oceans).

1. Direct fall onto the land surface

Water falling directly to the land surface can do one of four things:

a. Infiltrate (move into) the underlying soil.

b. Be evaporated back into the atmosphere.

c. Sit in depressions on the soil surface (from where it is later evaporated or slowly infiltrates into the

under-lying soil).

d. Runs off to lower lying areas (known as overland flow). If rain is heavy or the soil is hard to infiltrate

then there will be greater runoff. If rain is of low intensity or for only short periods, or the soil has good

infiltration characteristics (eg. sandy soils) then there will be little surface runoff.

Heavy surface runoff is a major cause of soil erosion of unprotected land surfaces. Therefore reducing

the effect of this runoff or protecting soil surfaces is a major need for effective permaculture systems. If

possible capturing this runoff in some way (eg. dams) for later use will make much more effective use of

natural rainfall.

2. Intercepted rainfall

Three things can happen at this stage:

Some of the water is evaporated back into the atmosphere before it even reaches the land surface

Some of the water will slowly drip to the land surface (eg. off vegetation).

Some of the water will flow down the surface of the intercepting body (eg. tree trunks and branches)

until it reaches the land surface (this is known as stem flow). This has two major effects, firstly

slowing down the rate at which some of the rainfall reaches the earth's surface, and secondly

concentrating what rainfall does flow down the branches and trunk, at the base of the trunk.

3. Water falling directly into water-bodies

The amount that falls directly into such bodies is usually small in comparison to what falls onto the land

(much bigger area) except in the larger water bodies (eg. oceans) where it will have little effect (directly)

on your permaculture system. Dams may have a small but significant increase in water volume from

direct rainfall, but most will come from surface runoff.

Rainfall

Actual rainfall is one of the major limiting factors determining what you grow in any particular site.

Deficiencies in rainfall can in many cases be offset by irrigation from alternative sources of water,

however if these sources are not available, or if water output is greater then input (compromising

sustainability) then you need to choose a site that provides sufficient natural rainfall for your plants.

There are four major points to consider regarding rainfall:

1. Distribution – ie. when the rain falls. An inch (25mm) of rainfall in a normally moist site during winter

conditions will not have the same significance as the same amount falling in a normally drier site, or in

summer.

2. Variability - some areas have very consistent rainfall, others do not. Two sites may have the same

average annual rainfall, but there may be quite different variation around that average at each site. For

example, each site may have an average annual rainfall of 1000mm (40 inch) but one may vary between

250 and 2000mm from year to year, while the other may only vary between 750 and 1300mm from year

to year.

3. Frequency – ie. how often it rains, can be important in determining the size of water storages. For

example where there is a large interval between periods of rain then water storages (e.g. farm tanks) will

have to be larger than for sites where rain falls frequently.

4. Intensity - This is the total rainfall annual divided by the number of wet days (days exceeding 0.2mm of

rain). This is very important in terms of runoff. In areas of high intensity rainfall runoff is generally high,

and consequently the percentage of water infiltrating into the soil is low in comparison to areas with low

intensity rainfall. Erosion can be a major problem in high intensity rainfall areas, while getting sufficient

runoff to boost water storages can be a problem in low intensity areas.

Evaporation

Evaporation is the loss of water as water vapour. It increases as temperatures increase, humidity drops

and winds increase. It can be measured by determining the amount of water evaporated from a free

water surface exposed in a pan. In countries, such as Australia, where surface water storage is extremely

important for agricultural purposes, evaporation is very significant. As with other climatic data, maps or

tables of evaporation data are generally readily available.

Infiltration

Infiltration into the soil surface will depend on a number of factors, including:

The type of soil - well structured and sandy soils will have much higher infiltration rates than heavy,

poorly structured soils (eg. clays).

The intensity of the rainfall - if rainfall is heavy then the amount of water reaching the surface maybe

greater than the amount of water that can be infiltrated. This means that the water either sits on the

surface until it can infiltrate into the soil later once rainfall has stopped or has reduced in intensity, or

be evaporated back into the atmosphere or it will runoff (overland flow).

As can be seen from the diagram ("The Hydrological Cycle") the water that passes into the soil can also

do several things:

It can be held in the soil (as "Soil Moisture Storage") where it can be utilised by plants and animals

(with some being transpired back into the atmosphere via the plants.

It can pass through passages in the soil (eg. cracks, animal burrows, cavities created by

decomposing plant roots) and pass out into lower areas as surface runoff. This is known as

"Through-flow". Passage of water in this way can be very rapid, and it can be a powerful cause of

erosion in soils that are easily dispersed (eg. tunnel erosion).

It can seep deeper into the underlying soil to an area known as the "Aeration Zone Storage". The

water here can be utilised by plants during very dry seasons. Water from this zone can also pass out

to the surface down-slope (into lower lying areas). This is known as "Interflow". Some water will also

percolate down deeper into "Ground Water Storage". In areas where ground water levels meet the

soil surface then water flows out (eg. springs) reaching creeks, rivers, etc.

It is this generally slow, regular flow of water from groundwater areas that keeps permanent streams

flowing in dry seasons. This is known as "Base Flow". Base Flow is one of two components to a

streams flow, the other being "Storm Flow", which is the water after rain from Overland Flow, Through

Flow and Interflow (see diagram). It is the often sudden surge of water after heavy rain that gives this

component of stream flow its name. These components of storm flow can often be diverted or slowed

down and used for providing water at a later date (eg. heavy vegetation or mulching reducing the

runoff rate, increasing the water-holding capacity of the soil so that more moisture is retained there,

terracing, banking or in some other way forming slopes to catch the runoff or slow it down).

It can percolate even deeper into deep storage (eg. aquifers, major artesian basins). Water from here

can flow out to the surface in much lower lying areas (eg. in saline affected areas). This water can

also be utilised through bores.

Effective Rainfall

Perhaps the most important climatic parameter that determines the growing season at a particular site is

'Effective Rainfall'. This can be defined as the rainfall over a certain period (eg. month) minus the soil

evaporation (equivalent to approximately one third of pan evaporation figures) during the same period.

Positive figures indicate that soil moisture is increasing, or in other words the amount of rainfall received

in that period exceeded the amount of water lost by evaporation. Negative figures indicate that

evaporation has exceeded rainfall and that the soil is drying up. The number of months in succession in

which rainfall exceeds evaporation (as long as temperature isn't a limiting factor) determines the growing

season of a particular site.

Calculating Effective Rainfall (using Melbourne, Australia as an example)

(Evaporation and Rainfall figures from Climate of Australia, October 1989 by the Bureau of Meteorology,

published by Aust. Govt. Publishing Services).

MONTH Dec. Jan. Feb.

Evaporation (E) in mm 187 204 179

Soil Evaporation = 1/3 (E) 62 68 60

Rainfall (R) in mm 58 47 48

Effective Rainfall = R - 1/3E (-4) (-21) (-12)

This indicates that there is no effective rainfall for the summer months in this locality (Melbourne). For

plants to successfully grow during these months there would have to be sufficient soil moisture storage

left from previous months or irrigation would have to be undertaken.

When the entire year is considered it can be seen that the natural growing season for Melbourne would

extend from March through to November.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

-21 -12 +8 +28 +39 +37 +34 +31 +31 +27 +9 -4

SOIL ENVIRONMENTS

Soil is composed of three main "ingredients". These are particles, air and water. Particles consist of clay,

sand, organic matter, living organisms, roots, nutrients, rocks, etc. Air provides essential gaseous

exchange areas within the soil. Water acts as a carrier for nutrients to the plant, flushes toxic elements

away from the plants, and like the other two "ingredients", keep the plant alive. The soil therefore will

influence the structure of the permaculture system. Soil itself has a structure that can affect plant growth.

Variations in soil over a small site can have a great affect in creating different microclimates.

Temperature, light, water and air characteristics of a soil can vary from place to place according to such

things as the depth of mulch/organic material on the soil surface; the depth of topsoil (which may have

been eroded from the top of a slope and deposited at the bottom of a slope etc. Adding mulch to an area

or working materials such as sand or manure into soil before planting can have a long term effect on the

type of microclimate created.

Simple soil testing is discussed in lesson 6.

Micro-organisms

The soil contains billions of life giving microorganisms in every handful, including thousands of species

of bacteria, hundreds of different species of protozoa and fungi, dozens of species of nematodes as

well as mites and other microscopic animals.

Some soil life breaks down and converts soil materials into humus and plant nutrients, holds these

nutrients in place and makes them available for plant use.

Organic Matter

The average soil contains around 2 to 4 percent organic matter. Organic content tends to drop in the

course of normal cultivation therefore adding organic matter to any soil-type will improve its quality. Only

soils already exceptionally high in organic matter, such as peat soils, will not benefit from additional

organic matter.

Organic matter benefits the soil in many ways, including:

Adding valuable slow-release nutrients to the soil.

Acting as a buffer against sudden chemical or temperature changes which can damage plant roots or

adversely affect soil micro-organisms.

Helping to improve soil structure.

Organic matter can be added in the following ways:

Incorporate home-made garden compost during the growing season.

Use organic mulches on top of the soil. Mulches such as leaf-mould, shredded prunings, composted

woody waste, and similar materials, are all ideal for the purpose. As material breaks down, particles

will be worked into the soil. Always mulch onto warm moist soil.

Leave crop plant roots in the soil, if possible, where they will decompose and increase the level of

organic material.

Incorporate well-rotted manure during the growing season.

Grow green manures whenever crops are not growing, particularly during winter months. The green

manures will protect the soil surface, as well as providing plenty of organic material to dig in.

Soils with good organic matter content are generally easily worked – that is, they have a ‘good tilth’. If

you squeeze a handful of soil into a ball in your hand and it remains in a hard lump, then it has a poor tilth

- hard clods will probably result when it is cultivated. If it crumbles, then it is well granulated with a good

tilth. Soils with good tilth are less subject to wind and water erosion.

SOIL DEGRADATION

When plants (trees and shrubs) are cleared from a site, soil is exposed to sunlight, soil aeration is

increased and the rate of weathering increases.

The proportion of organic matter in the soil gradually decreases, through the action of microbes in the soil

which use it as a source of energy unless the new land use provides a replacement for the material being

used (which the natural system was providing before it was cleared).

Types of Soil Degradation

A number of major soil related problems can and do occur these include:

1. Loss of soil fertility (plant nutrition is discussed in Lesson 6)

2. Erosion

3. Salinity

4. Soil compaction

5. Soil acidification

6. Build up of dangerous chemicals

Erosion

Soil erosion, which is the movement of soil particles from one place to another by wind or water, is

considered to be a major environmental problem. Erosion has been going on through most of earth's

history and has produced river valleys and shaped hills and mountains. Such erosion is generally slow,

but the action of humans has caused a rapid increase in the rate at which soil is eroded (ie. a rate faster

than natural weathering of bedrock can produce new soil). This has resulted in a loss of productive soil

from crop and grazing land, as well as layers of infertile soils being deposited on formerly fertile crop

lands; the formation of gullies; siltation of lakes and streams; and land slips. Humans have the capacity

for major destruction of our landscape and soil resources. Hopefully we also have the ability to prevent

and overcome these problems.

Causes of Human Erosion

Poor agricultural practices such as ploughing soil to poor to support cultivated plants or ploughing soil

in areas where rainfall is insufficient to support continuous plant growth.

Exposing soil on slopes.

Removal of forest vegetation.

Overgrazing.

Altering the characteristics of streams, causing bank erosion.

Causing increased peak water discharges (increased erosion power) due to changes in hydrological

regimes, by such means as altering the efficiency of channels (channel straightening); reducing

evapo-transpiration as a consequence of vegetation removal and also by the production of

impervious surfaces such as roads and footpaths; preventing infiltration into the soil and causing

increased runoff into streams.

Types of Erosion

The two basic types of erosion are:

1. Water erosion

2. Wind erosion.

Soil erosion, which is the movement of soil particles from one place to another by wind or water, is

considered to be a major environmental problem in much of the world. Erosion has been going on

through most of earth’s history and has etched out river valleys and shaped hills and mountains.

Such erosion is generally slow, however the action of man has caused a rapid expansion in the rate at

which soil is eroded i.e. a rate faster than natural weathering of bedrock material produces new soil

material. This has resulted in loss of productive soil from crop and grazing land, layers of infertile soils

being deposited on formerly fertile crop lands, the formation of gullies, siltation of lakes and streams and

mass land slips, etc. Man has the capacity for major destruction of our landscape and soil resources.

Hopefully we have the ability to prevent and overcome these problems.

Water Erosion

With water erosion, soil particles are detached by either splash erosion caused by raindrops or by the

effect of running water. Several types of water erosion are common in our landscapes. These are:

a/ Sheet erosion - where a fairly uniform layer of soil is removed over an entire surface area. This is

caused by splash from raindrops with the loosened soil generally transported in rills and gullies.

b/ Rill erosion - this occurs where water runs in very small channels over the soil surface. Over time

these small rills become deeper incisions. Losses consist mainly of surface soil.

c/ Gully erosion - this occurs when rills flow together to make larger streams. They tend to become

deeper with successive flows of water and can become major obstacles to cultivation. Gullies only

stabilize when their bottoms become level with their outlets.

d/ Bank erosion - this is the erosion by cutting banks of streams, rivers etc. It can be very serious at

times of large floods and cause major destruction to property such as buildings, roads and bridges.

Wind Erosion

If wind forces escalate to reach what is known as the "critical level" it can impart enough kinetic energy to

cause soil particles to move. Particles first start rolling along the ground or surface. Once they have

rolled a short distance they often begin to bounce into the air where wind movement is faster. The effect

of gravity causes these particles to head back down to the surface where they either bounce again or

collide with other particles causing them to also bounce along the surface (this is known as "saltation").

Two other kinds of wind borne particle movement occur.

These are:

"Free flight" where very small particles are entrained in air, which acts as a fluid, and these particles

are carried long distances; and

"Surface creep" where soil particles too large to bounce are moved downwind by collision with

bouncing smaller particles.

Control of Erosion

As erosion is caused by the effects of wind and water, the control methods are generally aimed at

modifying the effect of these two factors. Some of the most common control methods are listed below:

Prevention of soil detachment by the use of cover materials such as plants ie. trees, mulch, stubbles

crops, etc.

Crop production techniques such as fertilising to promote plant growth and hence surface cover.

Ploughing to destroy rills and contour planning to create small dams across a field to retard or

impound water flow.

Filling of small gullies by mechanical equipment or conversion into a protected or grassed waterway.

Terracing of slopes to reduce rates of runoff.

Prevention of erosion in the first place by careful selection of land use practices.

Conservation tillage agricultural methods.

Armouring of channels with rocks, tyres, concrete, timber, etc. to prevent bank erosion.

The use of wind breaks to modify wind action.

Ploughing into clod sizes too big to be eroded or ploughing into ridges – these cultural practices can

help reduce damage.

SALINITY

High salt levels in soils reduce the ability of plants to grow or even to survive. Some of this is due to

natural processes, however much occurs as a consequence of human action. Salinity has been

described as the "AIDS of the earth" and its influence is spreading through many countries where crop

production has been seriously affected, causing economic hardship.

Salinity problems have been grouped into two main causal types. Dry-land salinity is caused by the

discharge of saline groundwater where that groundwater intersects the surface topography. This often

occurs at the base of hills or in depressions within the hills on mountains themselves. The large scale

clearing of forests since the advent of European settlement in Australia for example has seen increased

"recharge" of aquifers (where groundwater gathers in the ground) due to less water being evapo-

transpired back to the atmosphere and hence a rise in the groundwater levels causing greater discharges

to the surface.

Wetland salinity occurs when irrigation practices have caused a rise in water tables bringing saline

groundwater within reach of plant roots. It is common on lower slopes and plains.

The wetland salinity problem is exacerbated by rises in groundwater levels due to recharge from aquifers

"leaking" as a consequence of vegetation (eg. forest) clearing upslope.

Sources of Salt

Salts are a naturally occurring by product of the weathering of bedrock and soil materials. Salts can be

accumulated in areas where they can become a problem by a number of ways which may have varying

importance from area to area. These include:

Cyclical movement - this is salt carried in evaporating ocean water that is later precipitated as rain

over inland and coastal areas.

Marine incursions – where inland seas existed in an area’s geological past: salt deposits are flow

remnants of these incursions.

In Situ weathering - the natural weathering of bedrock and soil resulting in the movement of salts

through a soil profile.

Aeolian deposits - salt that is believed to be material picked up and transported by wind from salt

pans, playa lakes, etc. In times of arid weather saline groundwater evaporated leaving saline surface

deposits in areas such as those encountered in some parts of Australia.

Control Methods for Salinity

Much of the control methods for salinity are very expensive and will require strong commitment by state

and national governments if they are to be undertaken. This will also require interstate co-operation as

such problems don't respect artificial boundaries. One of the major problems with salinity problems is

that the area in which the problem is manifest may be a fair distance from the source of the problem.

Thus we have saline groundwater discharging on the plains as a consequence of forest clearing high in

adjacent hills where salinity is not apparent.

Some of the main control methods are listed below:

Pumping to lower groundwater levels with the groundwater being pumped to evaporation basins or

streams

Careful irrigation practices to prevent or reduce a rise in groundwater levels

"Laser" grading to remove depressions and best utilise water on crop and grazing land

Use of saline resistant plant species

Re-vegetation of "recharge" areas

Re-vegetation of discharge sites to lower groundwater levels

Engineering methods designed to remove saline water from valuable crop land

By leaching suitable soils - eg. bowling greens, raised crop bed etc.

SOIL ACIDIFICATION

SOIL PH

Soil acidification is a problem becoming increasingly more common in cultivated soils. Soil acidification is

the increase in the ratio of hydrogen ions in comparison to "basic" ions within the soil. This ratio is

expressed as pH on a scale of 0 - 14 with 7 being neutral. The pH of a soil can have major effects on

plant growth as various nutrients become unavailable for plant use at various pH levels. Most plants

prefer a slightly acid soil however an increase in soil acidity to the levels being found in many areas of

cultivated land renders that land unsuitable for many crops or requires extensive amelioration to be

undertaken.

In rough terms pH can be described as a measure of the relative proportions of positive and negative

ions in the soil, in pure water they are equal and so the pH = 7, this is said to be neutral. A scale of 0 to

14 (called the pH scale) is used to record this measurement of pH.

0---------Acid---------7--------Alkaline--------14

^------------------------^---------------------------^

Most plants prefer a pH of 6 to 6.5 (ie. slightly acid), although there are many exceptions.

Plants may grow outside of their ideal pH range, but they will not grow as well. If the pH is below 4.5 or

above 8 it is very bad for the vast majority of plants.

Soil pH can be adjusted by the use of soil ameliorants. These include lime (to raise pH) and sulphate (to

lower pH). However, the soil will tend to buffer the effect of these chemicals and so calculation of the

amounts required is often difficult. The general rule is to apply small amounts until the required result is

obtained.

When lime is added to break up hard clay soils, it will also raise the pH of the soil (ie. make it more

alkaline). Addition of organic matter (eg. manure or compost), which contains weak acids, will cause the

pH to drop. If fresh manure is used, it can cause a drastic drop in pH.

WILDLIFE IN A PERMACULTURE SYSTEM

Plants and animals which are indigenous (ie. occur naturally) in an area are obviously well adapted to the

conditions found in that locality. They are usually an integral part of the complex ecosystem which occurs

there, and contribute towards the balance of nature in a way which enhances rather than conflicts with a

permaculture system.

As such the native plants and animals of an area should be cared for and preserved. To achieve this, you

must be very cautious in making changes to their habitat.

Always become aware of indigenous species before making changes to an environment.

Preserve a proportion of the natural environment in its existing state.

Areas which have been preserved in their existing state should be linked by strips (ie. corridors) which

are left unchanged (these corridors will allow plants and animals from different patches of preserved

"natural areas" to interbreed/interact.

Patches of indigenous plants can contribute towards a permaculture system in many ways including:

Controlling erosion.

Providing barriers against pests or diseases

Providing Food

Maintaining/replenishing soil fertility

Providing food and shelter for wildlife

Windbreaks

Biodiversity

Wildlife can contribute towards a permaculture system in many ways including:

Maintaining/replenishing soil fertility (eg. from manures)

Controlling pests

Game (eg. selective harvesting of unprotected species for food).

The following extract from the Permaculture Design Course Handbook (reproduced with kind permission

from the Permaculture Institute) raises a variety of issues which should be considered.

Wildlife Management

Encouragement

Species to encourage: insectivorous birds, ground birds

Forage: Extension of Zone II hardy forage systems and pioneer species, especially tagasaste, oaks,

pines, locusts (honey and black). (See lesson 3 for an explanation of permaculture zones).

Provide water

Provide shelter: hedgerows, escapement into dams, logs and litter, rough places

Mowing: Strip mowing for stability, mulch, seed crop. Permanent un-mown strips are needed.

Corridor into Zone I

Discouragement

Trap and cull systems for targeted noxious species

Increase bias towards chosen species

Provide no escapement, shelter, food or water"

STRUCTURE OF A PERMACULTURE SYSTEM

A permaculture system is made up of land, water, trees, soil, buildings, etc.

The arrangement and layout will mostly depend on personal preferences, providing the nine key guiding

principles, discussed in lesson 1 are followed:

1. Relative location

2. Multiple

3. Multiple elements

4. Elevational planning

5. Biological resources

6. Energy recycling

7. Natural succession

8. Maximise edges

9. Diversity.

Plants and their Function in a Permaculture System

The size, shape density and arrangement and diversity of plantings influences:

Temperature (plants make air and soil temperatures cooler in summer and warmer in winter).

Water (soil is less likely to dry out under a tree canopy).

Winds (direction can be changed, strength can be reduced).

Deciduous trees lose their leaves in winter creating different environmental effects in winter and in

summer

Frost (there is far less chance of frost beside or under the canopy of plants).

The Edge

As in natural forests there should be areas without large trees in a permaculture system.

The "edge" between a treed and non-treed area will be a different environment to the area with trees

and the area without trees. These "edges" provide conditions for growing things which won't grow

fully in the open or in the treed area either. The north edge of a treed area (in the southern

hemisphere) is sunny but sheltered while the south edge is cold but still sheltered, more than in the

open.

Pioneer plants are used initially in a permaculture system to provide vegetation and aid the

development of other plants which take much longer to establish (eg. legumes grow fast, fix nitrogen

- raise nitrogen levels - in the soil, and thus increase nutrients available to nut trees growing beside

them; over time the nuts will become firmly established and the legumes will die out). Pioneer plants

are frequently short lived.

GUILDS AND STACKING

Ecosystems can be stabilised and become efficient in the use of space through ‘stacking’. As in natural

forests -large trees dominate the system, they occupy the canopy level. The trees will affect everything

else - they create shade, reduce temperature fluctuations below (create insulation), reduce intensity of

light; reduce water loss from the ground surface, etc. The area beneath the canopy is occupied by lower

growing trees and shrubs, grasses and herbs grow at ground level.

In the natural habitat plants tend to grow in the following relationships:

1. The "upper-storey trees" can grow to over 100ft tall, although they are often shorter.

2. The "under-storey Trees" grow below the branches of the upper story, in some degree of shading, at

least during part of the day.

3. The "Seedling Tree" protected in its early life by the mature trees.

4. The "Shrubs" growing below the trees.

5. The ground covers, herbaceous perennials, annuals, mosses and other very low plants.

In permaculture we use the characteristics of the natural forest to our advantage - this relationship is

termed as "stacking". The plant used in stacking is termed as "Guild".

Stacking helps to:

Prevent weed growth through dense layering

Saves space

Prevents soil erosion

Plants use water, light and nutrients effectively

Revitalises degraded land.

Stacking also can refer to the careful selection of plants in the design. For example, how are the following

plants stacked: plants that supply nitrogen; plants that use nitrogen, plants that repel insects, plants that

climb using other plants for support? How careful are the guilds selected?

SUCCESSIONS occur in nature, whereby the type of vegetation changes in an area, over a period of

time, as the environment is affected by the plants and animals living in it.

Primary Successions are classified as follows:

1. Successions from dry to wet sites.

A typical sequence starts with lichens and mosses, perhaps with herbs this would then change to forest

or grassland.

2. Successions with bodies of water (eg. ponds, lakes, rivers etc).

Plants die in the water, embankments collapse, the shape of the water changes, the bottom can become

shallower finally shrubs and trees can grow on peat soil which builds up above the surface level.

3. Successions from rocky sites.

As plant roots and the weather breaks up the rock material, the nature of the soil changes making it more

suited to a different range of plants.

Secondary Successions occur when something happens causing a quick change in an area. This might

be a flood washing away topsoil, fire, logging, clearing sites for development -these and other such things

can cause a major change in turn, affecting the plant populations within just a year or so.

A common example of succession occurs when an existing tree or branch is damaged thereby allowing

light to penetrate. This causes new growth development in under-storey plants. Over time these

encouraged plants may take over from the damaged tree.

By manipulating the things explained above, you can affect micro climatic conditions to create

environments suitable for growing the plants you wish to grow in different parts of your permaculture

garden.

SELF ASSESSMENT Perform the self assessment test titled ' test 2.2’ If you answer incorrectly, review the notes and try the test again.

SET TASK

1. Visit an outdoor environment area (eg. garden, park, farm) and observe the various factors which

make up the ecosystem (ie. the abiotic and biotic components). Do not use a rainforest or heavily treed

situation for this set task. Try to see what relationships the living and non-living things might have with

each other (ie. where do the living things get their food, do they have shelter or provide any benefit to

other plants or animals, do they affect the soil, water, temperature, etc of the area?)

2. For at least one week, collect the local newspaper and cut out the weather map and details.

Progressively, keep an eye on how the weather changes and develops. See if you can make sense of

the isobars and weather maps. It may also be beneficial to watch the TV news weather report to see how

they interpret the information. Note your observations.

3. Carry out research to find any information you can on the water cycle.

ASSIGNMENT Download and do the assignment called ‘Lesson 2 assignment’.