introduction to tropical forests (lecture 1) Flashcards
Where are the tropics?
Between 23.4 degrees of latitude north (tropic of cancer) and south (tropic of capricorn) of the equator
How are tropical and temperate climates different?
- minimal variation in temperature throughout the year and diurnally = HOT
- mainly wet: rainforests get more than two metres of rainfall per year
- wetter and drier seasons but little seasonality overall
What are structural characteristics of tropical forests?
- tall
- dense
- dark
What are different types of tropical rainforest?
- continental variation
- hydrology
- altitude
- rainfall
different types of forest have different species compositions
continental variation:
- amazon, congo, borneo
hydrology:
- terra firme (dry ground)
- varzea (seasonally/permanently flood inundated forest)
- peatswamp
- dry dipterocarp
altitude:
- tierra caliente (low)
- tierra templada
- tierra fria
- tierra helada
- tierra nevada (high)
e. g. in Andes - rainforest to subtropical cloud forest
rainfall:
- dry vs rainforest
- mountain range rain shadow
Why do tropical forests matter?
- most species on earth
- enigmatic wildlife
- most endemic species (restricted range)
- highest species density on earth
- typified by complex networks of interactions
- key ecosystem services
What is tropical forest hyperdiversity?
- huge species densities
- as many as 650 tree species in one hectare
- 7 hectares in south east peruvian amazon, 600 bird species
What networks of interactions between species are there in the tropical rainforest?
- predation (top down effects exerted onto smaller predators by larger ones)
- nutrient recycling
- plant pollination by birds, insects, bas
- seed dispersals by birds & mammals
- symbiotic relationships where species live together and trade benefits
What are “devil’s gardens”?
- clearings in forest dominated by one or two species of ant-plant
- Duroia hirsuta plant provides Myrmelachista schumanni ants with housing in domatia
- some devil’s gardens are v large
e. g. - 594 D. hirsuta trees
- 15,000 queen/ 3,000,000 worker ants
- colonies can last 800 years
How do devil’s gardens get so large?
local legend?
- “spirit clearings” invisible villages of spirits
- swollen trunks surrounding clearing caused by fires set by spirits for swidden gardens
galling by ants?
- swollen trunks inhabited by ant workers, brood and queens
- 71% trees around clearing had galls
- severely nest site limited
cultivated by ants?
- ant workers kill other understorey plants with formic acid
- makes clearings for host plant
- selective advantage for host ant-plants
What are ecosystem services?
- ecosystem service is “the provision of a natural resource or process that is valued by humankind” (Edwards et al. 2014 Trends Ecol Evol)
What ecosystem services do tropical forests provide?
- carbon storage, mitigating climate change
- wood, fruits, animal protein
- hydrological services
e. g. rainfall/temperature control, erosion/flood protection
How is tropical biodiversity threatened in the tropics?
- humans causing sixth & only biologically driven mass extinction
- biodiversity loss most extreme in tropics
biodiversity loss mostly driven by:
- habitat loss (farming & fragmentation)
- degradation (logging)
- overexploitation (e.g. hunting)
