Lecture 1: Introduction Flashcards
Where are the tropicS?
23.4 degrees both North & South of the equator
temperature in the tropics:
minimal variation throughout the year and diurnally (during the day)
tropics mainly dry/wet?
- mainly wet! : rainforest >2m rainfall yr^-1
- wetter and drier seasons
basic Structure of trocial forest (2 levels)
- tall: lots of sun
- Dense dark undergrowth
who do tropical forests vary?
1) continental variation
2) hydrology
3) altitude
4) rainfall
Continental variations:
- the amazon
- the congo
- Borneo
- –> different species in different areas
hydrology variation e.g. Amazon
- Terra firme - dry
- Varzea - flooded for some time in year
hydrology variation e.g. Borneo
- Dry dipterocarp
- Peatswamp
Altitude variation:
-in the Andes BOTTOM -amazon rainforest -subtropical cloud forest -icy mountain tops -TOP species vary at different heights
rainfall variation: Andes:
- rainfall comes in from the east from atlantic ocean, rains over THE AMAZON
- mountain block rain access to West –> Tumbesian dry forest (C. 800mm rainfall per year)
other tropical dry forests:
- eastern Kenya/ Tanzania
- Western Madagascar
- Indochina
why do tropical forests matter??
- most species on earth!
- enigmatic wildlife
- most endemic (restricted range) species
- highest densities of species on earth
- typified by complex networks of interactions
- provide key ecosystems services
how would you describe the diversity in the tropics?
HYPERDIVERSE
- tropical forests have huge DENSITIES of species
- 1 hectare can have 650 tree species
- 7 hectares in SE Peruvian Amazon has 600 birds species
networks of interactions:
- rainforests typified by complex networks of interactions between species
- predation (e.g. largepredators exert top down effects on smaller predators)
- nutrient cycling
- plant pollination by insects, birds & bats
- seed dispersed by birds & mammals
- symbiotic relationship where species live together & trade benefits
example of symbiotic relationship in the tropics
“Devil’s” gardens
-Clearings in forest dominated by 1-2 species of ant-plant
Duroia hirsuta plant provides Myrmelachista schumanni ants with housing in domatia
Some Devil’s gardens get very large
594 D. hirsuta trees
15,000 queen & 3 million worker ants
Colonies can live for 800 years
how do the locals think Devils gardens arise?
- “spirit clearings” are invisible villages of spirits
- Swollen trunks surrounding clearing caused by fires set by spirits for swidden gardens
Real reasons for Devils gardens
- galling by ants
- -trees swollen trucks due to the trees inhabited by M. schumanni workers, brood and queens
- -71% of trees around clearing had gals
- -M. schumanni severely nest site limited
- Cultivated by ants?
- -M. schumanni workers kill other understored plants by injecting them with formic acid
- Creates clearings in which host plant thrives
- Selective advantage for host ant-plants
Ecosystem service definition:
the provision of a natural resource of process that is valued by humankind - Edwards et al. 2014 Trends Ecol Evol
examples of rainforests & ecosystems services:
- Carbon storage (mitigates climate change)
- Wood, fruits & animal protein
- Hydrological services
- -rainfall and temperature control
- -erosion & flood protection
Tropical forests are under
THREAT - Global Biodiversity Crisis
global biodiversity crisis:
- decrease in birds, mammals, birds & amphibians
- increase in extinction rates
- -distant past 0.1/1000 years
- -recent past 100/1000 years
- man is causing the 6th mass extinction, the only biologically driven one
whats new with this mass extinction:
the only biologically drive one
where is mass biodiversity loss?
IN THE TROPICS
____ are driving a biodiversity crisis
humans
-biodiversity loss is most severe in tropical rainforests
major drivers of biodiversity crisis:
Forest loss (farming & fragmentation), degradation (logging), and hunting are the major drivers
