Transcript Heathlands and roads

© Amy Rogers
© Amy Rogers
© Amy Rogers
© Carl Corbidge
Heathlands and Roads
Virtual Field Trip
• You are going to be learning about a very
important habitat – lowland heathland.
• You will learn about a case study of the A3
Road that passes through the Devil’s
Punch Bowl heathland in Surrey.
• You will be collecting data and conducting
analyses to investigate how the road is
affecting the ecology of the heathland.
© Amy Rogers
What are you going to do?
Objectives
You will be finding out:
• what nitrogen deposition is, and why it is a problem for
heathlands;
• What habitat fragmentation is and why is it a problem for habitats
such as heathland;
• how to identify common heathland plant species;
• how to collect vegetation data using quadrats;
• how to analyse data (graphically and statistically) to investigate
the effect of nitrogen deposition on heathland vegetation.
What is nitrogen deposition?
Atmosphere
• Over the past few decades there has been
an increase in emissions of man-made
nitrogen-containing compounds into the
atmosphere, notably nitric oxide (NO),
nitrogen dioxide (NO2) and ammonia
(NH3).
• The nitrogen contained in these compounds
can leave the atmosphere and enter the
biosphere – this process is known as
nitrogen deposition.
Biosphere
Naturally occurring nitrogen gas (N2) only enters the biosphere after being
fixed by micro-organisms or lightning.
Nitrogen-containing compounds such as nitrous oxides (NOx) and ammonia
(NH3) can enter the biosphere by both wet (i.e. via precipitation) and dry
deposition (i.e. the direct deposition of gases) = nitrogen deposition.
N2
NH3 & NOX
Why is nitrogen deposition a problem for
heathlands?
• Healthy heathland soils are nutrient poor – this allows plants like
to heather to out-compete faster growing plants (such as grasses
and bracken) and dominate the heathland.
• If soil nutrient levels increase, faster growing species (grasses,
bracken, birch trees) may invade and turn the heathland into a
different habitat (woodland).
• Nitrogen deposition can increase soil nutrient levels and so
threatens the existence of the heathland habitat.
Nitrogen deposition: Nitrous Oxide (NOx)
Which of these sources was the greatest emitter of nitrous
oxide (NOx) in England and Wales in 2005?
Industry
10%
Domestic & Commercial
21%
Road Transport
51%
Other Sources
18%
Source: Data for Neighbourhoods and Regeneration (http://www.data4nr.net/resources/503/)
Nitrogen deposition: Ammonia (NH3)
In 2007, 289 thousand tonnes of ammonia were emitted in the UK
(excluding natural sources).
What percentage of these emissions came from agriculture
51%
61%
71%
81%
91%
The aim of our investigation
• We will be investigating both the impact of
anthropogenic nitrogen pollution from
traffic emissions, and the impact of habitat
fragmentation.
© Lauren Gough
• The main aim of our investigation is to
understand the impact roads such as the
A3 can have on heathland habitats.
Section A
© Amy Rogers
© Amy Rogers
© Amy Rogers
© Carl Corbidge
Introducing the case study
site - Devil’s Punch Bowl SSSI
Guildford
Hindhead
This study focuses on the
Devil’s Punch Bowl SSSI
which is located near
Hindhead in Surrey.
About the Devil’s Punch Bowl
The Devil’s Punch Bowl is a large (280 ha) SSSI in Surrey.
Devils Punch Bowl SSSI also forms part of the following larger sites:
• Wealden Heaths Phase II Special Protection Area.
• Surrey Hills Area of Outstanding Natural Beauty.
Compare and contrast the different designations held by the Devil’s
Punch Bowl (i.e., SSSI, Special Protection Area, Area of
Outstanding National Beauty). Answer question 1 on page 2 of
your workbook.
About the Devil’s Punch Bowl
5
Supports a series of semi-natural habitats.
4
• Units 1, 2 and 4 are dominated by lowland heathland.
• Units 3 and 5 are dominated by mixed deciduous and
yew woodland.
• Other habitats present include scrub and meadows.
Supports over 60 breeding bird species – heathland species
include nightjar, stonechat, tree pipit and whitethroat.
Provides habitat for a rich and varied invertebrate fauna.
3
1
2
Section B
© Amy Rogers
© Amy Rogers
© Amy Rogers
© Carl Corbidge
The effect of anthropogenic
nitrogen deposition on heathland
Nitrogen deposition, the A3 and heathland
• The A3 is a very busy road, with an annual
daily average traffic flow of over 20,000
vehicles.
• These vehicles will be emitting fumes
containing nitrous oxide.
• Nitrous oxide could be deposited on the
heathland at the Devil’s Punch Bowl,
adding nutrients to the soil.
Nitrogen deposition, the A3 and heathland
You have been asked to conduct a survey to help understand how
pollution from the traffic using the A3 is affecting the heathland
vegetation. We would like to know whether nitrogen deposition from the
exhaust fumes is affecting the heathland vegetation composition (i.e.
which species are growing and how dominant they are).
You will collect data on the percentage cover of the following species
groups:
• Dwarf Shrubs (heather and gorse)
• Bracken
• Grasses
• Mosses
• Lichens
Identification training: dwarf shrubs
Common heather
(Calluna vulgaris)
Bell Heather
(Erica cinerea)
© Roger Key
© Roger Key
© Peter Crittenden
Dwarf Shrub 1 - Heather
There are three species of heather that may be found on our field sites.
You do not need to be able to distinguish between these species.
Cross-leaved heath
(Erica tetralix)
© David Glynne Fox
Identification training: Heather
For the purposes of this study, we do not
need to distinguish between the different
species of heather. All three species
have the following characteristics:
• Small purple or pink flowers
• Small, narrow, linear green leaves.
Cross-leaved heath
(Erica tetralix)
Identification training: dwarf shrubs
© Roger Key
Dwarf Shrub 2 - Gorse
• Yellow flowers.
• Stems have long spines.
© Roger Key
Identification training: moss
•
•
•
•
Small, simple leaves.
Grow close to ground.
No flowers.
May appear brown in colour if
conditions have been dry.
© Lauren Gough
Identification training: lichen
• Occur in range of shapes and
colours.
• Made of a fungus and an alga.
Practice time!
Dwarf Shrub (gorse)
Can you identify the
different types of plant in
this quadrat?
Warning: Not all plants
will have flowers!
Moss
Dwarf Shrub (heather)
Lichen
Nitrogen deposition, the A3 and heathland
You will be collecting data on the percentage cover of different plant
species to assess the impact of anthropogenic nitrogen pollution on
heathland plant communities
But before we begin…..
What kind of things might we need to plan/think about
before starting an investigation such as this one?
The two main things we need to think about are:
• How will we measure percentage cover? What is our sampling
unit?
• How should our sampling units be arranged?
© Peter Crittenden
How will we measure plant percentage
cover?
We will be using quadrats (0.5 x
0.5 m) to measure the percentage
cover of heather and bracken:
• Place the quadrat over the area of
vegetation to be surveyed.
• Look at the quadrat from directly
above.
• The total area of ground within the
quadrat is 100%.
• For each plant species, estimate
the % area of the quadrat that it
covers.
© Peter Crittenden
Using quadrats to measure % plant cover
Estimate
cover of
quadrat.
the
percentage
heather in this
Did everyone in your class
give the same answer? How
varied were the estimates of
percentage cover?
© Peter Crittenden
Using quadrats to measure percentage
plant cover
Should we
include
plants
which
are
rooted outside the
quadrat, but whose
leaves fall over the
quadrat?
Should we count
grass or plants that
appear to be dead?
How should we arrange our quadrats?
For your investigation you will compare samples (quadrats) of
vegetation taken in areas close to the A3 with samples (quadrats) of
vegetation taken in areas far away from the A3.
The samples (quadrats) that are far away from the A3 need to be
separated from the A3 by a large enough distance to not be affected
by the traffic emissions.
Using the graph provided on page 4 of your workbook,
calculate the distance at which emissions from the A3
should no longer affect the heathland vegetation on the
Devil’s Punch Bowl SSSI.
How should we arrange our quadrats?
The following slide shows two alternative sampling strategies that
could be used to investigate whether emissions from the traffic using
the A3 is affecting the heathland vegetation.
Which of the sampling strategies do you think is better and why?
Distance beyond which
emissions have minimal impact
on heathland vegetation
Sampling strategy A (systematic)
A3
= quadrat
Sampling strategy B (random)
Alternative sampling strategy (systematic)
Can you think of any
alternative sampling strategies
that would be appropriate?
In the sampling strategy shown
on the right, why is it important
to have more than one
transect?
A3
= quadrat
How many quadrats of data should we
collect?
Within each site, how many quadrats of data should we
collect? Should we collect, 1, 5, 10 or more?
The more the better! More quadrats mean more information about
the effect of nitrogen deposition on the percentage cover of heather
and bracken. In practice, the number of quadrats you collect will
depend on factors such as the size of the study site and the amount
of time you have for data collection.
In this study you will be collecting 5 quadrats per site.
Open the document ‘quadrats.ppt’ to start
collecting your data!
Complete questions B2 to B4.
Nitrogen deposition, the A3 and heathland
Questioning the experimental methodology
Were there any anomalous results?
What were the potential sources of error in your
investigation, and how may they have affected the validity
and reliability of your data?
What were the limitations of your methodology and the site
selection? How may these limitations have affected your
ability to assess whether nitrogen deposition affects the
heathland plant species community.
Section C
© Amy Rogers
© Amy Rogers
© Amy Rogers
© Carl Corbidge
The effect of habitat
fragmentation on heathland
The A3 road
The A3 currently passes through the Devil’s
Punch Bowl SSSI.
The A3 prevents the Devil’s Punch Bowl
heathland from being a continuous habitat.
Instead it forms two discrete habitat blocks, one
north and one south of the A3.
The process of breaking a previously continuous
habitat into smaller, un-linked sections is called
habitat fragmentation.
A3
The effect of habitat fragmentation
Edge habitat
Interior habitat
Answer question C1 in your workbook
The effect of habitat fragmentation
– Edge Effects
• Fragmentation increases the amount of edge habitat.
• This can cause what is known as the ‘edge effect’ – when the edge
of a habitat experiences different conditions (abiotic or biotic) to the
interior of the habitat.
Edge habitat
Interior habitat
Edge Effects
• For example, imagine a forest surrounded by arable fields.
• The areas around the edge of the forest will experience higher light
levels than the areas in the interior of the forest.
• If a road is built through the middle of the forest, the areas of forest
bordering the road will also experience higher light levels.
• The amount of edge habitat, and the edge effect, has increased.
Arable field
Edge habitat
Interior habitat
The effect of habitat fragmentation
– Edge Effects
• Edge effects can dramatically alter the plant and
animal communities found on the edge of habitats.
• The smaller a habitat is, the greater the proportion of
its area which experiences edge effects.
Answer questions C2 – C3 in your workbook
The A3 Improvement Scheme
The A3 that currently runs through the
Devil’s Punch Bowl is being improved.
Following the improvements, traffic will
flow underneath the site in a tunnel
instead of crossing the site overland.
Entrance to the1.8 km tunnel
underneath the Devil’s Punch Bowl
SSSI. Image source: www.nce.co.uk
A3
Old route of A3
New route of A3
Tunnel
Image produced at www.magic.gov.uk on 02/03/2011
The A3 Improvement Scheme
What benefits might the A3 Improvement Scheme have on
the flora and fauna of the Devil’s Punch Bowl heathland?
© David Glynne Fox
• Reduced nutrient enrichment of the soil from
emissions of nitrous oxides (NOx). This will reduce
the likelihood of nitrogen-loving species (e.g.,
scrub, bracken, trees) invading and outcompeting
typical heathland plant species.
© Roger Key
Potential benefits of the A3 Improvement Scheme
include:
• Reduced loss of individuals due to road kill;
• Reducing effects of habitat fragmentation allowing
species (particularly reptiles) to migrate between
the northern and southern portions of the reserve.
© Tracey Farrer
Other benefits include: