Lecture 3 Tropical Plant Life Flashcards
Plant life forms (Synusiae) –> 生态群
– these are not taxonomic groups but are functional forms of plant
- Trees
- Shrubs
- Herbaceous plants (usually smaller)
- Vines (a woody vine is a liana)
- Epiphytes
- Hemi-epiphytes (e.g Strangler figs)
- Epiphylls
Trees
- produce woody tissues
- secondary growth
- common threshold height to distinguish between shrub and tree
If species can reach 5m or more in hight then is considered a tree–> quite arbitrary, but the biggest shrub usually cant reach more than 5m in height - Trees main structural component in forest. Without trees = scrublands
- have repeatedly evolved in many groups: isnt 1 family tree of trees
Scientific names for trees
Given forests may have 1000 tree species (Canada have about 400, Ontario has about 200)
Often doesn’t have common names for trees: so need to use scientific names:
- Latin names always consist of genus+species
- genus is capitalized
- species name (epithet) is not . E.g Drybalanops aromatica (it should be italicized)
- always italicized
Common to give a family name because families broader and people know them
- family names are not italicized
Also there are many species within a genus
- so sometimes dont know what the species is
- Drybalanops sp. know the genus but species isnt specified
- Drybalanops spp. More than one Drybalanops species there
Are forests inevitable? –> importance of competition
- woody tissue has evolved many times
- thought to be inevitable evolutionary development because gives some plants big advantages over others
• light
• taller plants have advantage of accessing light and shading neighbors - tree ferns
• stem = composed of leaf bases (fronds)
• fern on top and lumpy stem - palms
- also many flowering plants
Marginal cases of ‘trees’
Arbitrary threshold of what trees are:
- on Mount Kilimanjaro, have giant senecio –> intermediate trees?
Other marginal trees
- woody vines start as free standing and later develop into lianas
- also very large herbaceous plants –> bananas get really big but dont form wood.
Shrubs and treelets
- Plants that from woody tissue but dont reach 5m
- shrubs usually have multiple stems at base but stem not utilized consistently
- in some forests many tree species that dont actually reach canopy
• ~2-5m in height
• sit in understorey
Characteristics of shrubs and treelets
- produce flowers and fruits at small size
- shrubs:
• usually have multiple stems at base/have vegetative reproduction - Treelets:
• Single- stemmed trees that dont reach large sizes
• Ex: Cacao in Euphorbiacea family –> is where cocoa comes from
Canopy layers Diagram
- Non-technical sources might see idealized concept of how tropical forests are structured
- might say there are 5 distinct layers
- in reality, clear strata in most tropical forests are not so easy to recognize and in some cases dont exist
Typical lowland forest profile
- more formal way is to construct a profile diagram: locate crowns of trees
- from badas forest reserve in Brunei
• have tall dipterocap trees(emergent)
•but also intermediate height vegetation - so strata not as clear as what is often shown
Distinct strata in monodominant forest
- profiles differ among forests
- Mbau forest dominated by one species
• Gilbertiodendron
•Big trees all of same species - so here, find really distinct canopy layer
- so some tropical forest (particularly those that dominated by single species) show distinct strata.
Herbaceous plants
- often do find discrete herbaceous layer
- in addition to woody plants are plants that dont form woody structures
• herbs
• lack secondary growth - Herbaceous plants can grow 4-5m in height maximum without forming wood
- EX: Banana trees:
• Giant herb
• Isn’t actually a tree
• can chop them down in one slice - other characteristics understorey plants: Fan palms: Licuala
• Very common in understorey
• get to be 4-5m tall
• form distinct layer in understorey
Comparison with temperate forests
Tropical forest:
- more tree species than herb species:
• ~400 species
• ~200 herb species
Temperate forest:
- more herb species than tree species
• ~ 15 tree species
•~ 150 herbs species
Really different in terms of ratio of things even compared to a ‘non-diverse’ tropical forest
Tropical and temperate forests pretty much have no species in common.
Many ‘primitive’ plants in tropical understories
- often find ferns and fern allies (fern-like plants)
- selaginella: Iridescent leaves that look like fern but is in other group
- Bracken fern: one of only plant species to have almost global distribution: so do find it in forests in Ontario, and tropics.
Parasitic saprophytic plants
- some plants don’t photosynthesize
- parasitic plants: EX: Rafflesia
• Genus of plants that produce the largest flowers on the planet
• ~40-50 spp of Rafflesia
• all of them are obligate parasites on 1 genus of vines (tetrastigma)
• always find a haustorium on rafflesia:
= Modification of root that allows plant to penetrate into vascular system of host.
So it can suck nutrients/phloem
= True parasite
• Have very narrow host range
• so if need giant flowers, means that we must also have vines for them to eat.
Lianas
- woody vines
- germinate and establish on forest floor initially (free-living)
- eventually find trees and have climbing mechanisms for climbing up trees
- some reach canopy, some stay in understorey
- not true parasites:
• dont tap into vascular tissue of host
• but use host for structural support = pretty negative effect on host - but some lianas are as important as commodities.
Typical liana life cycle
- Lianas germinate on forest floor
- initially self- supporting
- when they grow toward dark things:
• most plants grow toward the window (positive phototropism) - Lianas when small have negative phototropism (skototropism)
•Mechanism for finding dark places
•Places consistently dark are usually where there is a big tree trunk
• Liana knows this - attach to tree trunk up to canopy
- once they’ve attached change to have positive phototropism
- most only produce flowers and fruits when up in the over-storey
Climbing mechanisms
- some have root structures that attached
- some have tendrils
- some have hooks
- sometimes stem is modified to wrap around plants
Epiphytes
- plants that grow on other plants: dont climb, just stay put
- initially deposited in canopy
- Often bird-dispersed
- wide variety of ferns, bromeliads, orchids, mosses (mostly in high elevation forests)
- usually growing in places where there’s not much soil
• so have adaptations to deal with low nutrient inputs and periodic drought
• no soil reservoirs to hold water
Epiphyte common metabolic trick
- CAM photosynthesis • keep stomates closed in daytime • only open at night to allow CO2 in • initially fix CO2 into acids • Mobilize acids during day and re-fix CO2 using main metabolic machinery that most plants (C3 have)
- Helps deal with drought- prone environments
Epiphylls
- plants grown on other plants:
• but rather than growing on woody parts of trees (epiphytes)
• grow on leaves - include algae, liverworts, lichens, mosses that grow on leaves
- epi= grow on, Phyll= leaves
- common in tropical forests especially when leaves are longer lived
- usually smaller sized
- trees that are late- successional (characteristic of old-growth forest) tend to have long-lived leaves = habitat for lots of Epiphylls
- pioneer species that come into open areas have short-lived leaves
- secondary forest: leaves are short-lived
• if no Epiphylls probably secondary forest.
Hemipiphytes
- start up in canopy like epiphyte
- but then roots grow down stem and get into soil
- some of them stay like that
- but some them take over host tree:
• have root structures that completely cover stem of host tree
• leaf structures grow out and take over canopy space
• eventually gigantic strangular figs take position of host tree in canopy
• host tree dies off
• get decayed host tree stem
Hemiepiphytic figs
About 900 species of them
Very ecologically important
Are pollinated by minute fig wasps
o Very specialized mating system involving fig wasps
Most species of tropical trees flower and fruit synchronously
o Figs don’t do that
o Instead have asynchronous fruiting
o Flower independently, different trees flower at different times
o Some place in forest will probably be fig flowering
o So very important resource for fruit-eating animals
If looking for birds and animals, should look for figs
Lianas vs. epiphytes vs. hemiepiphytes
vs. epiphylls
check the table that compares all three of them
Fig and Fig Wasp Life Cycle
Female fig wasps exit fig after it falls off tree
Fly up and cover kilometers to find other food
Squeeze into other fruiting fig through small opening
o Often their wings are broken off
Flowers of fig are inside of fig
Wasps pollinate within flower (transferred pollen from other fig)
find more resources at oneclass.com
find more resources at oneclass.com
FOR201 – January 19, 2016
Lay eggs in host tissue
So males and females develop within the fig
Then mate within fig
Fig trees also have 1:1 match between figs and fig wasps
Every fig species has specific pollinator
Figs as a “keystone resource”
Often in tropical forests there isn’t a lot of fruit
Exception:
o Figs
o Often in fruit all the time
Frugivores (especially larger ones) are often fig specialists
o Parrots
o Toucans
o Hornbills
o Fig specialists
o Monkeys/other primates
If in forest and hear loud squawking birds and primate calls probably will find figs
Competitive displacement by larger species
In Africa studies looking at primates and utilization of figs
Pecking order:
o Small monkeys (Guenons) usually find fig trees first
o Larger mangabeys listen for Guenons to find fig trees, then boot the Geunons out
o Chimps hear mangabeys and boot mangabeys out
Other “keystone” resources
Fig = resource for frugivores when aren’t many resources
But there are other “keystone” species
EX: Fast-growing gap-dependent/secondary forest species to produce year-round
o Musanga tree
Fall-back resource if no figs
Great blue turaco specializes on fruits
EX: Some understorey species produces a lot of fruits
o Some species in Rubiaceae
But fig trees often most importan
Dipterocarps
Southeast Asia often dominated by single family called Diperocarpaceae (Dipterocarps)
These are gigantic trees (~80-90 m in height)
o = Forests of SE Asia are usually twice height of forests in Central Amazonia
o Family of trees that are dominant also show masting behaviour
Only fruit every 5-7 years
Exaggerates importance of keystone species
o Because no fruit for long time, then suddenly a lot
Dipterocarp canopy world quite different from understorey
o Many canopy specialists have evolved
o Flying frogs, flying snakes, flying lizards
Di-ptero-carp = 2-winged fruit
Fruit have 2 wings
o But some have 5 wings
Dipterocarp wood highly valued for wood/timber
Sensitive system because really big system and long intervals between fruiting events
Dipterocarp seedlings after mast fruiting event
After get blanket of dipterocarp seedlings but eventually die off
Leaves opposite vs alternate
Woody stem and leaves arranged either attached to same point or aren’t
Simple vs compound
Sometimes have leaves that are compound
Entire structure produced at same time
Whole leaf is divided (like a fern)
Leaf composed of several leaflets
So should always make sure what you’re calling a leaf is a leaf not a leaflet
Can have alternate leaflets along rachis of leaf but leaf is opposite
Reproductive parts give critical information
Flowers and fruits (reproductive structures)
o Yellow: Giant palm flower structures
o Figs
If you see reproductive structures can probably give good botanical names
Some tropical trees to know
Common, widespread, easy to identify, tell you about the forest
[1] Cecropia spp.
Most characteristic pioneer species that comes into open areas in tropics Have big fan-shaped leaves Gigantic leaves If look carefully: o Base of stems o The leaves are alternate o Have some fruiting structures o Also have ants that live on them o Sparse looking ragged canopies o Umbrella-like leaves If lots of them they’re a pioneer species that come in after big disturbance = secondary forest
[2] Miconia spp.
Opposite leaves Characteristic venation pattern (3-big veins) Then tertiary veins find more resources at oneclass.com find more resources at oneclass.com FOR201 – January 19, 2016 Many species of it o Some have purple underside Mostly pioneer trees (come into disturbed areas) Native to Neotropics but have spread
[3] Inga spp.
Inga is in the legume family (pea family)
Has pinnate compound leaves
Trees of various sizes
Leaves themselves are alternate
Along rachus has phalanges
And if look really closely, have glands
o Glands visited by ants
= extra-floral nectaries
o Mutualistic relationships
Nitrogen-fixing
o Could be primary or secondary forest
Compound leaves with phalanges
In neotropics are the biggest genus of trees
o Trends to be more ingas than anything else
o = most speciose legume genus in Neotropics
[4] Astrocaryum spp.
Understory palms that grow in clumps Long pinnate compound leaves Very thorny trunk Overlapping thorns o Really nasty If find palm, giant pinnate leaves Single bunch of leaves (monopodial) Widespread in secondary and primary forest
[5] Ficus spp.
Figs
One of largest tropical genera -all over tropics
Keystone
If break leaf usually have sap (bleed white)
Most are hemiepiphytes, but some free-standing trees
Should look for terminal cone-shaped buds (Can also see figs)
Fig venation patterns
Alternate leaf patterns
Figs are usually more abundant in primary forest
Trees have to be established, then figs come in
Takes time for figs to come in
