Why are the tropics so warm/wet?
- More direct solar radiation. As warm air rises
- and cools, it can’t hold on to as much water vapor, aka clouds form.
Air from equator pushed up towards poles
air curves to the right, s hem to the left.
Effects of mountains on climate
- Decreasing air temp w/ ↑elevation
- Rain-shadow effect
- Aspect-direction mountain faces (n-facing slopes are moister than s-facing slopes)
- Inter-tropical convergence zone moves up&down equator, bringing wet season w/ it.
Land use change
how humans have changed the land
evolution of unrelated species in response to similar selection pressures
broad leaves herbaceous plants
thick, tough, waxy, magnolia
- Low-lattitude regions where precipitation
- Warm, wet, no seaons. Rain has 2 main peaks w/
Soils are nutrient poor
- Vegetation – Broad-leaved evergreen and
- deciduous trees.
Up to 5 plant levels
i)emergent trees, evergreen trees, make up canopy
- ii)lianas-woody vines & epiphytes –grows on
- tree branches.
iii)Understory grow in the shade of the canopy
iv)Shrubs and forbs on forest floor.
Tropical seasonal forests and savannas
Wet and dry seasons, shifts with ITCZ
- Large change in climate associated w/
- seasonality of rain fall.
- Vegetation – shorter, lower tree densities,
- grasses, shrubs. Leaves can fall in dry season.
Tropical seasonal biome
Tropical dry forests
- Thorn woodlands – widely spaced trees/shrubs. Found
- b/w tropical dry forest&savanna climates. Thorns on trees.
- Tropical savannas – fires and seasonal flooding
- contribute to its formation.
- High temp, low rainfall. Located around the
- descending air of Hadley cells.
- Vegetation – succulent plants, dought-decidous
- shrubs and grasses.
- Desertification – Loss of plant cover and soil
- More seasonal temp variation than tropical
- climates. Warm moist summers, cold dry winters.
- Despite ample precip, fires/overgrazing keeps
- trees from dominating the grasses.
- Nutrient rich soil from all the decomposed
- Most human-influenced biome. (b/c of ag and
- grazing practices.
Temperate shrublands and woodlands
Seasonability of precipitation
Woodlands (open canopy of short)
Wet winter, dry summer
Veggitation – evergreens, sclerophyllous leaves
Temperate Deciduous Forests
- Found at 30-50o N along e and w edges
- of Eurasia and e NA
- Lower species diversity. Canopy trees, shorter
Fertile soils and climate are conducive to ag.
Temperate Evergreen Forests
Wide range of temp and precip
Those with high precip, typically on w coast b/w 45o &50o = temperate rainforests
Nutrient-poor soils (evergreen leaves = acidic)
- Lower diversity than deciduous&tropical
Some forests subject to fires, logging.
Boreal Forests (taiga)
- Above 50o N, found only in the n
Extreme weather, subarctic regions.
Permafrost – subsurface soil layer that remains frozen year round for at least 3 years
Vegetation – coniferous species (spruces, pines, larches - deciduous needle trees)
Least affected by humans
Occurs primarily in the arctic
- Poleward decrease in temp and precip is
- associated w/ the zones of high pressure generated by the polar atmospheric
- circulation cells
Vegetation – sedges, forbs, grasses, low-growing shrubs like heaths willows and birches. Lichens and mosses.
when communities change over time
Orgs have 2 ways of changing
each species has a range of env tolerances that determine its potential geo distribution
Phys env influences orgs’ ecological success
- Ability to obtain resources, maintain metabolic functions, grow, reproduce.
- Extreme env conditions can impact survival
- Geo distributions also influenced by the biotic env (competition, ect).
- the total range of conditions that a species
- needs to survive and reproduce
pops of the same species w/ adaptations to unique envs.
Energy balance equation for all animals
∆H= SR + IRin – IRout ± Hcond ± Hconv – Hevap + Hmet
heat exchange b/w 2 solids