Understanding Ecosystems

1
Understanding Ecosystems

• Vegetation Change on Mont Lozère

2
What is an Ecosystem?

• A community of plants and animals within a
  physical environment or habitat
• It can exist at any scale from large biomes e.g.
  Tropical rainforests to individual hedgerows
• Created by the interaction between the biotic and
  abiotic environment

3

• Over time, ecosystems evolve through clear
  developmental stages in response to the physical
  environment.
• Human intervention may upset this sequence both
  intentionally and unintentionally.
• Understanding how an ecosystem works involves
  studying two key components that of energy flows
  and nutrient recycling.

4
Energy Flows

• All energy within an ecosystem comes from what?
• The Sun
• Plants absorb the energy from the sun in a
  process known as photosynthesis. They are the
  primary producers and the first link in the food
  chain.
• Plants are consumed by plant eaters herbivores
  or primary consumers.
• They in turn are eaten by carnivores or secondary
  consumers.
• The food chain can therefore be seen as a
  sequence in which organisms at each level become
  the food source for the next.

5
Nutrient Cycling

• The circulation of minerals around the ecosystem.

Input dissolved in rainfall (from atmosphere)
Leaf fall, dying vegetation
Biomass
Uptake by plants
Litter
Litter decomposing
Loss in runoff
Soil
Loss by leaching
Input weathered from rock
6
Mont Lozère has a variety of different
ecosystems-

• Peat Bog
• Broom-Scrub
• Heather Moorland
• Coniferous woodland
• Deciduous Woodland
• Grassland

Each is different and is composed of a different
type of vegetation
7
Why do we get such different ecosystems in Lozère?

• Geology and Soils Parent Material
• Climate (Microclimate)
• Relief
• Aspect
• Artificially Introduced

8
Peat Bog-

• Formed in hollows in the impermeable granite.
• Ground is permanently waterlogged which halts the
  decomposition of plants in the bog as decomposing
  bacteria are aerobic and cannot survive in
  waterlogged soil.
• The rate of organic accumulation exceeds the rate
  of decomposition and layers of peat form.
• Granite bedrock becomes weathered, it produces
  acidic soil.
• Peat bog soils are therefore wet, acidic and as a
  consequence, low in nutrients, although rainwater
  will wash some soil and nutrients into the bog.

9
Broom Scrub

• Broom is a tough shrubby plant that grows up to
  2m high.
• It has little nutritive value and cattle find it
  very difficult to eat and digest.
• The broom scrub is burnt at approximately ten-
  year intervals, to remove the dense broom
  canopy and allow smaller herbaceous plants and
  grasses to flourish for a short period.
• This practise called ecobuage turns practically
  useless rough grazing into more productive
  grazing.

10
Heather Moorland

• The moorland area, at an altitude of 1530m, is
  very exposed and is unlikely to have ever been
  under forest cover.
• Only low growing, shrubby species with xerophytic
  adaptations survive the harsh conditions at this
  site.
• Winters are extreme and the ground may be under
  snow for four months. Summers are hot and
  droughty.
• Area dominated by common heather, bilberry,
  cowberry and alpine ladies mantle

11
Coniferous Forest

• Whole area used to be covered by oak, beech and
  mountain pine.
• However deforestation took place to make way for
  agricultural practices.
• PNC (1970) Afforestation, timber production.
• The main species planted are a variety of
  conifers, oak and beech, planted in mixed age
  stands to reduce fire and disease risk.
• There is little ground cover in the coniferous
  forest, due to lack of sunlight reaching the
  floor and due to the deep acidic layer of
  slowly-decomposing needles.

12
Deciduous Forest

• These are beech woods with very little
  undergrowth due to the dense leaf mosaic,
  characteristic of the species.
• Temperate deciduous forest ecosystems only occur
  in the northern hemisphere.
• Deciduous trees lose their leaves in winter.This
  is because their roots encounter difficulty in
  extracting water from cold soil and in response
  trees will shed their leaves in order to reduce
  water loss by transpiration.

13
Aims of Study-

• To determine which abiotic factors are
  instrumental in bringing about certain
  ecosystems.
• To quantify the plant community in contrasting
  ecosystems and to understand what factors in the
  abiotic environment lead to their presence.
• Identify land management practices which may have
  resulted in particular ecosystems

14
Objectives

• To examine the soils in several contrasting
  ecosystems and determine whether the soil depth,
  pH, texture or temperature is important in
  producing a particular ecosystem
• To use and rationalise a range of vegetation
  sampling procedures to quantify the vegetation
  community in a range of contrasting ecosystems
• To determine the effects of soil type in
  producing a particular vegetation community at a
  site.

15
Sampling

• If we want to know what kind of plants are in a
  particular habitat, and how many there are of
  each species, it is obviously impossible to go
  and count each and every one present.
• This problem is usually solved by taking a number
  of samples from around the habitat, making the
  necessary assumption that these samples are
  representative of the habitat in general.
• In order to be reasonably sure that the results
  from the samples do represent the habitat as
  closely as possible, careful planning beforehand
  is essential.

16
Studying the Plant community
Involves the use of Quadrats

• Qualitative Techniques
• Based on subjective observations and
  descriptions.
• Percentage cover open frame quadrat
• Abundance scale DAFOR
• Quantitative Techniques
• Where objective numerical data is collected.
• Percentage frequency gridded quadrat
• What size quadrat would you use???

17
Nesting Quadrat Exercise

• Idea of a Pilot Study
• The choice of quadrat size is affected by the
  diversity of the ecosystem and by the size of the
  organisms under investigation
• Use progressively bigger quadrats
• 10 x 10cm, 50 x 50cm or 100 x 100cm

5
7
10
10
18
How should your quadrat be placed in the study
area?
RANDOM
STRATIFIED
SYSTEMATIC
19
Random Sampling

• Not following any particular pattern.
• How could we ensure a random sample in order to
  eliminate bias?
• Quadrats placed in a 10m x 10m grid
• Co-ordinates plotted using a random number
  table
• Advantages / Disadvantages??
• How many quadrats is enough??

20
Running mean gaining a representative sample
21
The number of quadrats needed in this case 7
22

• Systematic Sampling
• Regular sampling system
• Big advantage, you know exactly where the sample
  has come from. Geographical idea of location
• Would sample this across a line or TRANSECT
• Good technique when your expecting to see a
  change across an Environmental Gradient
• Two types of transect
• Interrupted
• Continuous Belt

23

• Stratified Sampling
• Stratified sampling is used where there are
  small areas within a larger habitat which are
  clearly different. For example, scrub patches
  within a heathland area, or areas of bracken in a
  grassland.
• Sampling would be carried out either randomly,
  or systematically within each separate stratum
  identified.

• This recognizes major differences within
  communities before sampling begins.

24
In Summary

• When sampling vegetation the following must be
  considered
• Decide on quadrat size.
• Choose as sampling method (random, systematic or
  stratified).
• How will you record the vegetation cover,
  objective or subjective and choose your equipment
  accordingly.
• Choose the best recording sheet for your purposes.