Lecture 2 Tropical Forests And Their Role In The History Of Ideas

Question 1

Exaggerated tales of tropical forests

Answer 1

For Europeans + North asians forests were exotic

• -> many erroneous ideas
• -> people thought they were really chaotic

Vicious animals

• -> were dangerous places
• -> crazy wild beasts in there
• -> people thought would get attacks by apes

Impenetrable ‘jungle’ with vicious animals –> strong cultural images of forests

Question 2

A common but non-scientific term –> ‘Jungle’

Answer 2

What does the word ‘Jungle’ actually mean?

• -> word is derived from Hindi word jangal which means desert: waste area, uncultivated
• -> doesnt have a formal scientific meaning
• -> so for this course we don’t use ‘Jungle’ in the essays

Question 3

Species-poor with a uniform flora

Answer 3

Later on in European history were initial explorations in areas of tropics: coast of African, islands

People brought back coconuts and other species to European: bananas, Jack fruit, structures from red mangroves, sea almonds

Always brought same thins back from the tropics:
–> idea emerged that plants in the tropics were all the same

Question 4

Where did the early explorers explore?

Answer 4

Scientists never went far inland
Basically just going to the beach
Even if they did go inland, –> met local people that had agricultural areas
But they didnt go back into forested areas
So came up with idea that there were just pan-tropical species that were everywhere in tropics
Thought there were a small number of species
But in tropics, things are actually quite different and very diverse between different tropics places.

Question 5

Even great scientists make great mistakes

Answer 5

Carl Linnaeus (1707-1778)
Wrote a summary of tropical forests
What he wrote about tropical forests was pretty much fall wrong

Question 6

The most famous tropical voyage in the history of science

Answer 6

Charles Darwin in 1840s on the beagle

Went to Galapagos

Question 7

Voyage of the beagle (1831-1836)

Answer 7

• • Didn’t visit Asian tropics, but went south through Australia and off coast of Africa
• • this was not the first scientific voyage of discovery: darwin modeled his voyage after Alexander Von Humboldt
• • Humboldt was darwin’s hero

Question 8

Alexander Von Humboldt

Answer 8

Botanist

Question 9

The world’s first international scientific expedition

Answer 9

• -Was launched in 1799
• -Went to Latin American to Orinoco river with Aime Bonpland
• -was first purely scientific expedition (which wasn’t the case with Darwin): before scientists usually go with explorers looking for gold/land
• • had interdisciplinary scientific team: Botanist, zoologist, geologists
• • first scientists go into real topics (not just going to beach)
• • went to Andes, Orinoco and upper America

Question 10

Excitement of tropics

Answer 10

Coconut trees
Foot high bouquet of flowers
Everything looked new to people on this expedition because no one had really ever ventured into rainforest before.

Question 11

Route of Orinoco expedition

Answer 11

Coast of South America, Caribbean
Expedition made up hundreds of miles in Orinoco collecting thousands of species
Eventually went up into the Andes

Question 12

Von Humboldt and the relationship between climate and vegetation

Answer 12

• • Humboldt’s big achievement was a map of Chimborazo mountains in Andes
• • if look at height of mountains in terms of being as as from the centre of the earth, Chimborazo is the tallest (taller than Everest, Everest s broad)
• • Humboldt was the first to systematically link climate, soils, geology, vegetations
• • going up Chimborazo, things higher on the mountain looked more similar to European plants (northern latitudes)
• • first person to notice parallel between going up in elevation in tropics and going north in latitude

Question 13

Orinoco flow: reverses direction

Answer 13

Sometimes flows in one direction, then switches

If have big rain in one area can have flow reversal –> remarkable geographical discovery

Question 14

Von Humboldt’s legacy

Answer 14

• -concept of the scientific expedition
• • made last major attempt to synthesize all scientific knowledge into 1 work (single work ‘Cosmos’)
• • More geographical places named after von Humboldt than any other individuals in history
• • inspired to next generation of scientists (including Darwin, Von Liebig and Wallace)

Question 15

Charles Darwin and the voyage of the Beagle

Answer 15

• -Went to Galápagos Islands
• -noticed finches
• -gave him ideas for natural selection
• -sent finches specimens to John Gould who looked at patterns: was Gould that identified ‘Darwin’s’ finches and linked beak evolution to islands geography
• • then later on, darwin interpreted patterns

Question 16

Darwin’s unacknowledged source

Answer 16

– forester Patrick Matthew who didnt go to the tropics, worked in Europe
– did work on apple trees:
Noticed that if he planted cultivated apple trees back in forest, they died
By selecting trees that produce big apples, was diverting energy from other things in tree so couldnt compete in natural forests
So has to be natural process of selection analogous to cultivation that happens in wild to allow trees to survive (divisions between species not so clear)
– darwin did experiments on apple (grafting) that replicated things Matthew did
– so Patrick Matthew was actually the first guy to use word ‘Natural selection’
– Darwin never cited him because Matthew was a radical

Question 17

Darwin’s legacy beyond natural selection

Answer 17

• -Foundations of community ecology: tangled bank limits population growth
• -earthworms and the biology of soil formation
• -pollination biology
• -sexual selection
• -structure of biological thinking and argumentation
• • but natural selection not his originally

Question 18

Other Great 19th century tropical biologists/explorers

Answer 18

Many biologists lose loves to research in tropics – from disease

Question 19

Alfred Russel Wallace

Answer 19

–In spite of spending huge amounts of time in tropics lived to quite old
–collected more beetles than any single other person
–continued doing this in spite of first great beetle collection being lost in shipwreck
–Wallace laid foundations for natural history and biogeography for Southeast Asia (Malay Archipelago)
– Unlike Darwin who stayed on 1 boat, Wallace lived on the site for long time, met the local people:
Learned local languages
Took up culture in way that was unusual in 1800s.

Question 20

Wallace and evolutionary biology

Answer 20

Discovered birds of paradise

Question 21

Southeast Asia

Answer 21

• -Contributed to biogeography
• -started off close to Singapore, then to Borneo, then to Lombok island
• • noticed species changed completely between islands
• • went over narrow gap between 2 islands and almost no species in common
• -noticed differences were systematic
• -different set of species found in 2 close areas

Question 22

Borneo vs Guinea

Answer 22

In Borneo find Gibbon, Broadbill, rhinoceros hornbill
In Guinea find tree Kangaroos, birds of paradise, parrots
Almost no overlap between biota in 2 islands
Why?
– separated on 2 different tectonic plates
–Wallace didnt actually figure this out but got really close

Question 23

Tropical florist regions

Answer 23

• -completely different in 2 parts of tropics
• -tropics divided into 2 zones:
  (1) new word tropics=Neotropics
  
  • -> sub-zones: Central America, South America
  • -> in general, Central America has different species than South America

(2) Paleotropics
– > subzones:
Africa
Madagascar (own unique biological realm from Africa)
South Eastern Asia (Indonesia, Singapore, India etc):
(a) core area centered on Borneo
(b) North of this border, climate is really different : Monosoonal/seasonal forests
(c) also includes New Guinea: other side of Wallace’line
(d) New Caledonia: ecologically separated for long time from other continents
(e) Australia: small bit of tropical area in Australia

• • across zones and sub-zones have few species in common:
    
    • -> with exception of coconuts (which are very widely dispersed)
    • -> in general, almost no overlap in biota of different areas
• • bur notice still some green in desert band areas (like Monsoonal Asia)
    
    • -> mostly places with mountain ranges resulting in more unique and endemic species
    • -> as get into areas with mountain ranges separating places, many more unique and endemic specie.

Question 24

Some of Wallace’s major contributions

Answer 24

• • first to link geographic distributions to evolution
• • first field observations on Orangutans
• -independent proposed natural selection, and co-authored paper with darwin which promoted the concept
• -collected >100000specimens from region known as ‘Wallacea’: most birds and insects
• -introduced concept of polymorphism
• -introduced concepts of functionality in animal coloration, including aposematic (warning) coloration: e.g Black and hello stripes on bees-toxic/dangerous organisms
• • first proposed ‘green belts’ near urban areas: having conservation areas
• • introduced statistical methods in epidemiology
• -concept of ‘exobiology’: extra-terrestrial origin of life on earth: there is an extra-terrestrial origin for life on earth = seeding of life from other planets

Question 25

Two more Wallace contributions:
‘‘The museum ‘diorama’”
“Recognition marks’ in natural history

Answer 25

1. Diorama:
   First person to come up with museum diorama
   Allow us to see where organisms live in museums instead of seeing bunch of dead animas in glass boxes
2. Recognition marks
   First to use recognition marks that are used in natural history works
   Establishing what you have to look for to identify species in the fields: distinguishing characteristics of species.

Question 26

Truth about tropics forests

Answer 26

• • are not impenetrable ‘jungles’ or fruit-filled gardens of Eden
• -most diverse/complex ecosystems on planet
• -Huge variation from place to place
• -understood mostly through collaborative sciences
• -rapidly declining due to human population pressure and patterns of resource use
• -represent one of the most important scientific and social challenges to the human species.

Question 27

Global distribution of forests

Answer 27

• -area of forest in northern hemisphere
• -south of it is band of deserts
• -at equator is another area of forested area
• -go south again is another band of deserts
• -further south is subtle band of vegetation

Question 28

Latitudinal gradients in forest types

Answer 28

• • northern and southern bands corresponds to boreal and temperate forest:
    (a) these are divided geographically by dry and tropical areas
    (b) most of northern forest is giant Eurasian chunk of forest –> very continuous
• • tropical forests:
    (a) few species in common between tropical and temperate /boreal forests
    (b) whereas have more similar species between temperate/boreal forests.
• -tropics forests more broken up:
  (a) no land bridge between them (no continuous)
  (b) lots of geographic separation for things to evolve separately
  (c) so lots of moss species that are the same across Canada, Russia, Scandinavia
  (d) but almost nothing like that in tropics

Question 29

What determines the global distribution of vegetation types?

Answer 29

1. Temperature: as Humboldt said
2. Rainforest (total amount and seasonality)
3. Soils
4. Natural disturbance regime (wind, fire): say recent hurricane struck, then forest will look different
5. Human activities

Question 30

Latitudinal variation in solar energy

Answer 30

More energy from sun at equator than northern latitudes
Pattern driven by geometry (check the equation)
At equator, sunlight spread out over narrower range
Towards pole, same flux of energy projected over larger surface area
If you’re north of Tropic of Capricorn, sun is never directly ahead
So difference in energy =first part of explaining pattern

Question 31

Diurnal variation in light

Answer 31

Truncated sine wave function
Clouds interfere
But maximum light follows half of sine wave

Question 32

What are mountain tops cool?

Answer 32

Ideal gas law PV=nRT
T=PV/nR
Pressure goes down:
-->Lower pressure as go up in elevation
-->change in pressure results in changes of temperature: other things stay constant

Question 33

Adiabatic cooling (or adiabatic lapse)
'Adiabatic' =not involving work

Answer 33

Change in temperature
Approximately relationships:
–> if have dry air and go up 100m, will have decline of 1 Celsius: 1C/100m
–>if have moist air only decline 0.6 for every 100m: 0.6C/100m
Water molecules in air gain heat of condensation
Phase change of water involves a lot of energy
So partially offsets adiabatic cooling

Question 34

Using Adiabatic lapse rate

Answer 34

A math question , here you can skip

Question 35

‘Hopkins’ Bioclimatic law

Answer 35

–If go from equator north or south get progressive decline in temperatures
– loser to equator, 120 m of elevation =1 degree of latitude
–Andrew Hopkins came up with this relationship between elevation and latitude:
(a) came up with this by looking at patterns of plant distributions
(b)Manitoba maple:
Common in waste areas in Toronto
If climb up mountains in southern Mexico, will find it.
Might also found other maples

Question 36

Precipitation

Answer 36

Vegetation you find at a site is also determined by rainfall
Fundamentally all plants require water
Water has to come from precipitation
Plants and soils can store water but have limited capacity: so if have variable rainfall, plants that can store will maintain water
But in general, seasonality and total amount of rainfall are important

Question 37

Climate Diagrams (Klimadiagrams)

Answer 37

• German came up with it
  -divid monthly rainfall totals into areas considered wet, dry and drought
• Wet period:
  (a) Rainfall exceeds potential evapotranspiration
  (b) corresponds to ~100 mm of rain paper month
• dry period:
  System likely to lose more water than gains but not whole lot more
• drought period:
  Less than 50 mm or rain per month
  Might be affected by temperature regime too
• could have areas that have similar total rainfall but different patterns (different seasonality)
• India:
  Monsoonal period
  Then really heavy rainfall
  But very Singapore
• Singapore
  One of the least seasonal places on planet
  Is wet but not hugely wet
• so big differences in vegetation

Question 38

Climatic variation in tropical Asia

Answer 38

• show areas close to equator in Southeast Asia: Singapore is the least seasonal
• northern areas:
  monsoonal areas
  Big annual seasonal changes in rainfall belts
  Then pronounced dry season
  Also in Australia
• can map rainforests onto map
  Usually to be considered rainforest, get ~1500 mm of rain per year

Question 39

Aseasonal wet tropical forests include world’s most diverse forests

Answer 39

Area in Amazonian Ecuador
High diversity of plants
Very wet

Question 40

Seasonal dry tropical forest has much lower diversity

Answer 40

Grass in understorey
Very different
Western Ghats, India
Far fewer species = enormous differences in diversity that track differences in climate

Question 41

Seasonal vs aseasonal tropical forests

Answer 41

Seasonal tropical forest
- distinct dry/drought season (at least 2 months in direction)
- more deciduous trees:
(a) lose leaves during dry season = drought deciduous
- often have natural fire region:
EX: forests in Thailand and southeast Asian often have low level ground fires
- Trees are smaller
-lower tree species diversity
-higher Liana abundance = woody climbers
More light getting through and lianas need lots of sun

Aseasonal

• Often wet for whole time
• few deciduous trees
• fires of any sort uncommon
• larger trees
• high tree species diversity
• lower liana abundance

Question 42

Some more basics of climatology

Answer 42

• All this energy coming into equator
• in addition to making it warmer on average, have a lot of chance for evaporation:
  (a) Evaporation off water bodies (lakes, rivers, streams)
  (b) Transpiration through leaves
• results in lots of rising warm and moist air
  (a) rising warm air cools according to adiabatic lapse rate
  (b) water precipitates, and forms clouds
  (c) thats why lots of clouds in tropics

Question 43

Hadley cells

Answer 43

• general widespread circulation pattern
• areas right at equator where have maximum energy coming in and maximum evaporation = ITCZ
• pattern of air movement that is one of big climate patterns of planet
  (a) as warm moist air rises, lots of rainfall precipitates out
  (b) then air with rain squeezed out (so very dry) moves north and south and descends at 30 degrees’ latitude
  (c) creates high pressure zone
  (d) these are where the band of deserts lie
• Hadley cell circulation gives rise to bands of wet forest and bands of desert

Question 44

Global distribution of deserts

Answer 44

But some places still have forest even in the band of desert: especially Asia

Question 45

Sub-tropical forests

Answer 45

• subtropics: more or less between 15-40N and S
• areas that if there weren’t ‘other things’ going on, they would be deserts:
  (a) in general, these are mountainous places
  (b) have forests coursing where there is sufficient moisture
• big chunks of sub-tropical forests (China, Australia, Mexico etc)
• these areas receive moisture:
  But often close to these areas also have hot dry areas

Question 46

Rain shadows

Answer 46

• patterns is driven by rain shadows:
  Rain shadow effect is pronounced in sub-tropical zones
• have wind coming in and affecting patterns of rainfall close to mountains
• as air rises and cools (adiabatically), reach particular elevation where clouds form
  (a) water in liquid form and condensation
  (b) particular elevation band where lots of rain squeezed out of clouds
  (c) so get forested area
• above condensation level (cloud level), air cools at dry adiabatic lapse rate:
  Above that band of clouds can be really cold, because lapse rate is higher
• have dry air descending on other side of mountain
  (a) all of that air is warming up at dry adiabatic lapse rate
  (b) get pattern
  (c) so as go over mountain to other side, is much hotter because of difference in wet and dry adiabatic rate
• so subtropical forests can be quite wet, but found close to hot dry desert areas

Question 47

Rain-shadow vegetation

Answer 47

• sparsely trees savannah
  Rain shadow variation
• is within close proximity of extremely wet high elevation forest

Question 48

Tropical rainforest climate

Answer 48

• rainforest climates vary between major parts of tropics
• major biogeographic areas with little vegetation in common
• temperatures:
  Don’t vary much
  -solar radiation:
  Don’t vary much
• precipitation:
  Huge variance
  Amazonia has big range
  East Malesia really wet
  Africa, India, Australia are dryer areas: marginally about 1500 mm annually necessary for rainforest.

Question 49

Soils.. why things arent so simple

Answer 49

• Differences in soil really contribute to wide range of vegetation
• comes out from weathering of geological material in combination with activities of plants (and animals to some extent)
• creates natural substrate for rooting of terrestrial vegetation
• in general, soil has to do with climate and vegetation

Question 50

What else do trees need, beyond favorable temperature and water?

Answer 50

• plants need nutrients
• big 3:
  N, P, K
  In general, in tropics, there is high temperature and many ancient substrates
  Nutrients leach out
  P is only available from geological sources
  So most tropical forests tend to be P limited
  Whereas northern forests more nitrogen limited
• but a lot of differences in soil in within tropics

Question 51

Typical tropical soils

Answer 51

• highly weathered:
  Hot; very cold; lots of water percolating through soil
• reddish coloration because organic acids leaching things from soil = tropical soils usually red
• 2 main types of tropical soils
  (1) Ultisols: red-clay soils, distinct A and B soils, Ult= ultimate product of weathering.(2) Oxisols
  Ox from oxides of Fe and Al
  More yellow-red due to more bioturbation
  More bioturbation so no distinct horizons
  More organism stirring up soil
  What organism?

Question 52

Giant tropical earthworms

Answer 52

Giant earthworm stirring soil
Bioturbation
Termites also help
Result in bioturbated oxisol soils

Question 53

Health forest (kerangas)

Answer 53

• distinct forest vegetation
• depend on differences in soil and soil parent material
• health forest in Malaysia:
  (1) tops of trees are about head-height =very depauperate forest
  (2) find them on rocky substrates of sandy soils
  (3) usually nitrogen limited

Question 54

Tropical coastal forests

Answer 54

Distinctive 
Depauperate flora
Same species occur from place to place 
Characteristic ocean-dispersed species 
Not very productive = issues with salt spray

Question 55

Swamp forests

Answer 55

If go inland, find swamp forests
Forests with continuous or intermittent flooding 
Swamp = wetland with trees
Main types of swamp forests: 
        (1) mangroves
        (2) freshwater swamp forests 
        (3) Peat swamp forests 
Vary depending on whether flooding happens often, and on salt

Question 56

Mangroves and mangrove species

Answer 56

Mangrove

• associated with salt/brackish water
• formed pan-tropically in coastlines and estuaries

mangrove species:

• species are dispersed by sea water floating propagules: so many species have large distributions
• most common species are rhizophora and Avicenna:
  (1) both global in distribution
  (2) have weird roots
  (3) root structures look like breathing tubes
• species have adaptations to environment
  (1) Pneumataphores = breathing tubes in roots to oxygenate them (since they are under water)
  (2) Stilt roots: air channels, structures that anchor plants and oxygenate roots

Question 57

Bruguiera

Answer 57

• weird reproductive biology
• many mangroves have fruits that actually germinate on the trees
• baby mangrove trees hang off other mangrove trees=viviparous seeding
• convenient from management perspective: can pull off seed, stick it mud.

Question 58

Nipa

Answer 58

Salt water palms

Question 59

Freshwater swamp forests

Answer 59

• No saltwater involved
• Flooded/periodically flooded forest type inland enough that no salt water intrusion
• many different kinds of swamp water forests
• depends if forests is in big estuaries, lake area, or little streams
• in Malaysia, small level streams dominated by certain plants

Question 60

Varzea and Igapo

Answer 60

• many types of freshwater swamp forests
• Varzea:
  (1) swamp forest types where have white water rivers
  (2) white rivers from silt: have high pH, also high productivity
  -Igapo
  (1) forests that have black water rivers:
  Like Rio Negro in amazon
  Low pH
  Lots of dissolved tannins from leaves
  Lower productivity systems
• middle picture
  Silty river from varzea
  Black water rivers so acidic that mosquitos cant breed in it.

Question 61

Peat Swamp Forests

Answer 61

• rivers draining intact peat swamp forests are tannin-stained ‘blackwaters’
• big areas in SE Asia and New Guinea
• peat swamps have accumulation of undecomposed plant matter
  Rooted in layers of peat
  Gradual process
  Are places where have gigantic peat formations (in Borneo)
• Modern types of forests most similar to Carboniferous forests that give rise to oil reserves.

Question 62

What is peat

Answer 62

Accumulated non-decomposed organic matter

Dig down into muck and find organic matter

Question 63

Biodiversity and threads to peat swamp forests

Answer 63

• common organisms in undistributed peat swamp forests:
  Sumatran Rhino
  Proboscis Monkey
  Bornean Swamp Toad
• can deal with acidic conditions
• threats:
  Clearing and draining, burning off peat to make shrimp ponds
  Shrimp ponds gradually acidify, and become non-productive
  Clearing for oil/palm developments
  Peat fires

Question 64

Characteristics changes in forest with increasing altitude

Answer 64

• shorter trees
• smaller leaves
• more epiphytes (especially mosses)
• trees more gnarled: stems less straight
• big changes in species composition: = latitudinal variation
  More plants related to temperate zones: conifers, Ericaceae (blueberry family), Fagaceae (beech)

Question 65

Cross section slide

Answer 65

• lowland rain forest: really tall
• lower montane forest: shorter but still multiple layers, often tree ferns
• lower montane cloud forest: often particular areas where cloud forms; cloud forest
• upper montane cloud forest
• subalpine cloud forest:
  High elevation forests sometimes called elfin forests
• have full altitudinal gradient in forest structure

Question 66

Cloud forest

Answer 66

Not actually that diverse 
Convergent to temperate forest 
40-50 tree species rather than 100
Shorter trees
Lots of moss converted trees
Not many lianas
Relatively low diversity, but really specialized unique species 
One mountain might have different set of species than another

Question 67

Key physiognomic characteristics of tropical forest types

Make sure to check out the diagram

Answer 67

Tropical dry forest has most lianas