lsm2251 11 landscapes

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.


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:





Key feature: heterogeneity vs. most of ecology deals with relatively homogeneous areas

A landscape is:





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 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




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.




of landscapes.


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.




of landscapes.


landscapes.



Not much progress yet, but there are on-going

studies that look at how landscape structure influences carbon dioxide uptake and release.




of landscapes.


landscapes.



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.

lsm2251 11 landscapes

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