lsm2251 11 landscapes
TRANSCRIPT
LSM 2251
Lecture 12
Landscape Ecology
Summary of Lecture 10:
1. An ecosystem consists of a community and its physical environment.
2. Ecosystem ecologists mostly study energy and nutrient flows.3. Energy cannot be recycled, nutrients must be.4. Trophic levels are relative positions in the food web. The
number of trophic levels is higher in ectotherm food webs, since less energy is lost at each stage.
5. On a global scale, terrestrial Net Primary Production is controlled by temperature and rainfall. Nutrients are locally important. Marine NPP is largely controlled by nutrients. Consumers can have a positive or negative influence.
6. Carbon follows the same pathway as energy through ecosystems. Carbon is recycled globally but not locally.
Summary of Lecture 10:
7. Plant growth is limited by the nutrient with the least favorable supply, i.e. lowest availability relative to needs. This is thought to be usually N or P in terrestrial systems, but can be a micronutrient, such as Mo.
8. Decomposition has a key role in the supply of nutrients for plant growth, so factors that slow decomposition (drought, cold, tough or chemically defended plant materials) reduce the rate of supply of nutrients.
9. P tightly cycled, K less so. N is lost as oxides in fires. Leakage is mostly replaced by weathering of soil minerals, except C & N.
10. Small catchment studies show the key role of plant uptake in minimizing nutrient losses.
11. Human activities have a huge impact on C, N and other cycles.
Natural cycle – because is more forest in northern hemisphere than southern
Human carbon dioxide
emissions
NPP
estimate
from
satellite
June
Red>yellow
> green>
blue>black>
grey
December
From NASA- data from
MODIS
satellite
Climate change projections for Singapore by 2100:
From „downscaling‟ of the IPCC global results:
Temperature 2.7 – 4.2oC higher than today
Rainfall trends uncertain – some models predict higher
overall, some lower, but most agree that wet periods
will be wetter and dry periods drier.
i.e. more floods and droughts
Bukit Timah Nature Reserve
Different ways of looking at Bukit Timah Nature Reserve:
Single species
Species-species interactions
Entire guilds/communities
relative abundance
species richness
evenness
diversity
Food webs
Other interaction webs
Keystone species
Succession and stability
Energy and nutrient fluxes
As a patch of forest in a larger landscape – this week!
Alex Yee: Honours Project 2009-10
Reading:
Molles - Chapter 21
Smith & Smith – Chapter 19
See also the article in Wikipedia. This has been built up by many authors, so it is not very consistent, but it gives a better overview than Molles.
There is also an excellent on-line publication by TG Barnes “Landscape Ecology and Ecosystems Management” at: www.ca.uky.edu/agc/pubs/for/for76/for76.htm
Note: this lecture will necessarily be a
fairly superficial summary of a huge topic.
A landscape is:
A heterogeneous area consisting of distinctive patches, or landscape elements, organized into a mosaic pattern. Molles
A heterogeneous landscape composed of interacting ecosystems. Smith & Smith
A spatially heterogeneous area characterized by diverse interacting patches or ecosystems. Wikipedia.
A heterogeneous area consisting of distinct patches. Me
A landscape is:
A heterogeneous area consisting of distinctive patches, or landscape elements, organized into a mosaic pattern. Molles
A heterogeneous landscape composed of interacting ecosystems. Smith & Smith
A spatially heterogeneous area characterized by diverse interacting patches or ecosystems. Wikipedia.
A heterogeneous area consisting of distinct patches. Me
Key feature: heterogeneity vs. most of ecology deals with relatively homogeneous areas
A landscape is:
A heterogeneous area consisting of distinctive patches, or landscape elements, organized into a mosaic pattern. Molles
A heterogeneous landscape composed of interacting ecosystems. Smith & Smith
A spatially heterogeneous area characterized by diverse interacting patches or ecosystems. Wikipedia.
A heterogeneous area consisting of distinct patches. Me
Key feature: heterogeneity vs. most of ecology deals with relatively homogeneous areas
Arguably, this is the best approach for studying Singapore.
Landscapes are made up of patches or landscape
elements - relatively homogeneous areas that are
distinct from their surroundings.
Note1: landscape ecology usually deals with the
human scale, i.e. metres to kilometres, and the
terminology and methods are rarely applied at
much larger or smaller scales. Sometimes,
however, a bird, mammal or butterfly (etc.) scale
makes more sense.
Landscapes are made up of patches or landscape
elements - relatively homogeneous areas that are
distinct from their surroundings.
Note1: landscape ecology usually deals with the
human scale, i.e. metres to kilometres, and the
terminology and methods are rarely applied at
much larger or smaller scales. Sometimes,
however, a bird, mammal or butterfly (etc.) scale
makes more sense.
Note2: two technical developments over recent
decades – remote sensing from satellites and
geographical information systems (GIS) – have
contributed greatly to the development of
landscape ecology.
Satellite images
invite a
landscape
perspective
Defo
resta
tion in
Bra
zil
GIS makes quantification of landscapes easy.
Land cover
surrounding
Madison, WI.
Fields are
colored yellow
and brown,
water is
colored blue,
and urban
surfaces are
colored red.
From the
Wikipedia
article.
With a GIS you
can abstract
particular
landscape
elements and
study them
separately.
This is forest.
This view of
the landscape
is particularly
relevant for
forest-
dependent
species.
This is
impervious
surfaces.
This view of
the landscape
is particularly
relevant for
urban species.
Note that the
impervious
surfaces in the
landscape are
more
connected
than the forest
Alex Yee: Honours Project 2009-10
Vegetation Types Area (ha) Proportion
(%)
Number of
Patches
Non-vegetated 28,270.43 38.85 22275
Managed Vegetation 19,972.96 27.45 29075
Scrubland 4,307.54 5.92 8340
Young Secondary F. 14,288.48 19.64 2920
Old Secondary Forest 994.68 1.37 42
Primary Forest 118.34 0.16 15
Mangrove Forest 662.43 0.91 491
Freshwater Marsh 76.6 0.11 227
Freshwater Swamp F. 283.12 0.39 125
Landscape ecology includes:
1. Describing landscapes, often quantitatively
2. Understanding the history and spatial dynamics
of landscapes.
3. Measuring interactions and exchanges across
landscapes.
4. Understanding the influences of landscapes on
biotic and abiotic processes.
5. Learning to manage landscapes.
Landscape ecologists:
…study the effects of spatial pattern on ecological
processes.
Most professional landscape ecologists are paid
as wildlife managers, so their focus is on
understanding and then managing the effects of
landscapes on one or more target species, e.g.
giant pandas, tigers, urban birds.
Landscape ecology includes:
1. Describing landscapes, often quantitatively
Landscape structure:
Size
Shape
Composition
Number
Position
of patches
Each square
is 10 x 10km
– a typical
scale for
landscape
studies. Only
two elements
are shown:
forest and
deforested
areas.
The human
brain is
surprisingly poor
at dealing with
this sort of
heterogeneous
pattern, so
quantitative
measures of
landscape
structure are
very important.
This is % forest
in the whole
landscape.
This is patch
shape, defined
here as the ratio
of the perimeter
of the patch to
the perimeter of
a circle of the
same area, i.e. it
varies from 1,
for a perfect
circle, upwards.
Median values
are:
1.16
1.60
Many real landscapes have > 2
elements, but the number
considered is fairly arbitrary,
e.g., for Singapore, we could use
green/non-green,
forest/non-forest, or
forest/shrubland/grassland/urban..
But note that ignoring the
differences within particular
elements/patch types (i.e.
assuming they are homogenous)
oversimplifies the real situation
and is a weakness of the
landscape approach.
matrix
patch
patch
Another concept: the matrix is the most continuous and/or most
connected landscape element. Most, but not all, landscapes have
a matrix in which the other elements are embedded as patches.
patch
patch
Landscape ecology includes:
1. Describing landscapes, often quantitatively
2. Understanding the history and spatial dynamics
of landscapes.
What creates the patchiness?
geological processes
biological processes
human impacts (most emphasis in landscape ecology)
The Yukon, Canada. Association between vegetation elements
(green) and surface geology (white) in a natural landscape.
Some animals, such as beavers and elephants, act as “landscape
engineers”, creating patchiness in an otherwise homogenous
landscape
Beavers re-
invaded 300
km2 of
Minnesota in
1925, after
extirpation,
subsequently
transforming
the
landscape.
They're back!
Beavers return to
Scotland for first
time in 500 years!
Mail Online
In May, 2009, 11 beavers from Norway were released in Scotland,
where they had been extirpated by hunting 500 years ago.
They're back!
Beavers return to
Scotland for first
time in 500 years!
Mail Online
The hope is that beaver reintroduction will restore natural habitat
heterogeneity and benefit other species
African elephant pushing over a tree.
Many
landscapes
are the
product of
human
influences.
This graph
and the
previous one
show the
change in the
total area of
each major
landscape
element, but
not patch
number, size,
shape etc.
1819 1900 1990
Land-use changes in Singapore 1819-1990: primary forest;
cultivated land; secondary grassland, shrubland and forest; urban
areas (including parks and gardens). Again, this graph lacks
information on other aspects of landscape structure (which would
make it a lot more useful!)
1819 1900 1990
The graph also simplifies the landscape by recognizing only four
elements. The secondary vegetation in the 19th century was
mostly grassland, maintained by frequent fires, while today it is
mostly forest. The main crops in the 19th century were gambier
and pepper, but in the first half of the 20th century rubber trees.
Landscape ecology includes:
1. Describing landscapes, often quantitatively
2. Understanding the history and spatial dynamics
of landscapes.
3. Measuring interactions and exchanges across
landscapes.
Interactions and exchanges can involve energy,
materials (water, nutrients etc.) or organisms, but
most work has been on organisms.
A lot of recent work has focused on fragments of the original habitat in a human-modified matrix.
matrix
fragment
fragment
Defo
resta
tion in
Bra
zil
Rainforest
patch
Agricultural
matrix
This study used
experimental
patches to study
the influence of
landscape structure
on small mammal
movements in
prairie in the USA
Small mammals in small patches were less likely to move,
but when they did move they moved further than those in
large patches.
Fig. 21.13
These graphs show the
influence of patch size on
population size and density of
a butterfly species.
The study also showed that
more isolated patches
supported fewer butterflies
and that the populations in
small patches were more
likely to go extinct.
Note: these patterns depend
on the movements of
butterflies between patches
but, unlike the previous study,
these movements were not
directly studied.
Another butterfly study
showed the importance
of connectivity, which is
a major theme in
landscape ecology.
Such studies have
obvious implications for
conservation
The Biological Dynamics of Forest Fragments
project in Amazonia created 1, 10, and 100 hectare
forest patches in a pasture matrix and has been
studying changes in the organisms in the patches
for 30 years. Species have been lost from all patch
sizes, but much faster from the smaller ones.
1 ha
10 ha 100 ha
Many studies have shown the importance of natural habitat
connectivity for wildlife survival in agricultural landscapes.
Landscape ecology includes:
1. Describing landscapes, often quantitatively
2. Understanding the history and spatial dynamics
of landscapes.
3. Measuring interactions and exchanges across
landscapes.
4. Understanding the influences of landscapes on
biotic and abiotic processes.
Not much progress yet, but there are on-going
studies that look at how landscape structure influences carbon dioxide uptake and release.
Landscape ecology includes:
1. Describing landscapes, often quantitatively
2. Understanding the history and spatial dynamics
of landscapes.
3. Measuring interactions and exchanges across
landscapes.
4. Understanding the influences of landscapes on
biotic and abiotic processes.
5. Learning to manage landscapes.
Landscape management is very often
about restoring connections. This is
the Bukit Timah Expressway, which
has divided BTNR from the Central
Catchment Nature reserve since 1986
The proposed “Eco-link” will provide (by 2014) a
forested connection between BTNR and CCNR:
but will wild species use it?
Note: it is not just for animals: plants can cross as
seeds in the guts of dispersal agents.
Different ways of looking at Bukit Timah Nature Reserve:
Single species
Species-interactions
Entire guilds/communities
relative abundance
species richness
evenness
diversity
Food webs
Other interaction webs
Keystone species
Energy and nutrient fluxes
Succession and stability
As a patch of forest in a larger landscape – this week!
The same principal on
a bigger scale:
This forest management
plan in British Columbia,
Canada, uses landscape
ecology principals to
protect biodiversity by
ensuring that core
ecosystems are
connected by
„landscape corridors‟
And bigger: an on-going effort
to link up existing and planned
conservation areas in northern
SE Asia and SW China with
„biodiversity conservation
corridors‟. Note: the major
problems in such plans are
usually socioeconomic not
scientific.
Giant panda distribution has become highly fragmented in the last
2-3 centuries. How does this influence their chances of survival?
Community
or Ecosystem
Landscape
Community
Community
Community
Community
Landscape
Community
A regional scale
is particularly
appropriate for
looking at
problems like the
extinction of
species.
Other
problems
need a
global
view
Summary of Lecture 11:
1. A landscape is a heterogeneous area consisting of
distinct patches
2. Patches or landscape elements are distinct, relatively
homogenous areas.
3. Usually applied at the human scale, although the scale of
the organism(s) of interest may be more appropriate.
4. Landscapes can be described by the types, sizes,
shapes, numbers and positions of the patches.
5. Patchiness can arise from the physical environment or the
action of „landscape engineers‟, but most studied
examples are a result of human impacts.
6. The most connected landscape element is the matrix.
7. Understanding and managing landscapes often involves
consideration of connectivity.