Wednesday, March 7, 2012

Post Midterm - Lecture 1 - biomes + anthropogenic biomes

1biomes¶

1.1biomes as a function of temp and precipitation¶

• saturation Curie - Amt of moisture in the air is a function of temp (cold air can't hold much water)
• increase of precipitation - increase in biomass
• moisture is limiting reactant in productivity
• ecological niche

1.2arctic/tundra¶

• northernmost/southernmost - antarctic is mostly an ice sheet, so we mostly just talk about the north
• much more tundra in the north than in the south
• long winters, short growing season
• winter: mostly dark
• summer: can get very hot, summer radiation is 80% of montreal radiation - short but intense growing season
• 10 degree celcius summer isotherm (tree-line). above this latitude, it is unfavorable for trees to grow
• <250mm precipitaiton annually
• treeless, mostly grasses, ligands, dwarf woody plants, mosses
• most vegetation is annual
• perennial vegation is insulated by snow in the winter (in the snow, temp is around freezing)
• landscape is very young (as compared with when the glaciers receded)
• • thus, most stuff grows on the rocks
• animals: insects or rodents. note: animals have to graze on limited material. the only exceptions are animals that get food from the oceans

1.3alpine¶

• 10 dgree isotherm, but instead of latitude (like arctic), it's elevation
• Himalayas is largest
• slope and aspect play important role
• slope: rook slides, avalanches, regular disturbances kill of plants
• aspect: which direction are facing (north vs south)
• plants are self pollinating (don't rely on insects), plants are bulblets - instead of seeds - survive over winter
• fewer large animals in alpine vs arctic (less water, no access to oceans)

1.4boreal/taiga¶

• just below tundra
• worlds largest forest biome
• circumvoyla - same ecosystem all the way around the world
• spruce, firs, mosses, ligands, lemmings, boles, caribou, moose
• trees are relatively small, <30m
• trees: thin+spindly (so ice + snow doesn't break the branches)
• permafrost in northern taiga - usually 2-3m active soil, then solid ice below that
• drunken trees - melting permafrost
• trees are rather young - disturbance factors: fires in summer, insect infestations, ice and snow, limiting area, outgrow itself (roots can only go so far)
• peatlands - anaerobic respiration, breaking down carbon very slowly. leaves don't break down as quickly -> thus a huge carbon store
• peatlands - methane production

1.5temperate rainforest¶

• rare ecosystem (BC, New zealand)
• lots of rain
• dominated by conifers
• located on oceans, don't have freezing regions
• confiers are better than deciduous for colder conditions
• • conifers: year round productivity (they don't drop their leaves)
• epiphytes - grow on trees (like moss on trees)
• redwoods - CA, tall, old
• douglas firs - 400 yrs
• • cuz: tall because: lack of disturbance (no ice storms, no fires)

1.6temperate¶

• mcgill nature reserve
• • one of oldest beech maple forest in region
• deciduous - take advantage of summer productivity
• fire - rejuvenation of soil, germination of seeds
• east to west - gets drier, gets more to open grasslands

1.7temperate grasslands/prairie¶

• too dry for trees, still enough moisture for grasslands
• great plans, parries, the 'step?' in central asia
• hot in summer, cold in winter
• defined by grasses: tend to be annual (hars winters), very deep roots (droughts in summer) - very productive soil
• high abundance in diversity of large mammals (horses, bison, deer, kangaroo)
• fires: common, important, thunderstorms, returns nutrients to soil

1.8temperate scrubland/chaparral (mediteranean)¶

• dry
• near oceans - hot but moderate
• vegetation: dense scrub
• southern cal, Mediterranean, chile, south africa
• wine country
• natural vegetation is aromatic (sage, lavender)
• fire is common, vegetation is < 50 yrs old
• santa anna winds in socal - massive brushfires
• citrus, grapes, olives

1.9arid/deserts¶

• <50 cm a year
• air is trying to suck out water from every surface
• extremely dry, can be very hot or very cold (mongolia)
• hot in day, cold at night
• 4 causes of aridity
• 1) high pressure zones (hadley and farell cells)
• 2) away from oceans, no source of moisture (australian outback), no winds bringing moisture
• 3) topographic rain shadow (nevada, arizona) - air coming on other side of mountain is dry - all water gets dropped on other side of mountain
• 4) cold ocean currents (northern chile) - make air very dry (can't hold alotta water)
• landscape: sand (sahara) or rocky
• lack water: erosian+disturbance is caused by wind (prevents vegetation)
• specialized plants to adapt (mesophytes, zerophytes)
• plants: spines (protection from animals), no leaves, or very thick waxy leaves (prevent evaporation)
• most animals are nocturnal (less evaporation, to hot during the day)

1.10savanna and seasonal forest¶

• distinct with isolated trees
• 65% africa, 60% of …
• large Amt of rainfall - extremely seasonal (dry wet seasonality) - really dfines the savanna
• plants are well adapted to drought (dry hot period), grasses w/deep roots, trees w/waxy leaves
• grasses dominate due to disturbances (mostly fire)
• thick bark, thick leaves - resistant to fire
• grass can grow back from roots after a fire
• c4 plants, rather than c3 - well adapted to hot temps
• large animals: antelope, wildebeest, zebra, giraffe, rhinos, cheetahs, lions
• great migrations - migrate with shifting precipitation with interopical convergence zone

1.11humid tropical forest¶

• warm temps, lots of ramie
• hadley cells meet - intertropical convergence zone
• most productive ecosystem - not limited by temp or by precipitation
• multiple layers or ecosystems
• central america, south america, southeast asia, congo
• diversity: perhaps due to age, perhaps due to amt of energy
• 10% of land area, 50-90% of species
• limiting factor: nutrients - soils are nutrient poor - very old - weathering for ~10s of thousands yrs old - nutrients are leached out by runoff - most of nutrients is almost all in vegetation - high rate of nutrient recycling (if a tree falls, its nutrients gets picked up quickly)
• lungs of the earth (terrestrial)

2human impact¶

2.1erle ellis - describing anthropogenic biomes¶

2.1.1data sets¶

• population density, croplands, pastures, irrigation, rices, tree cover -> define anthromes

2.1.2anthromes¶

• 3 kinds:
• 1) used (dense settlements, villages, croplands, rangelands)
• 2) seminatural
• 3) wild

2.1.3wildlands¶

• don't have people
• tundra, deserts, alpine
• 19% of global tree cover
• unproductive regions
• boreal forest - classic example
• still not pristine (logging, hydro dams/reservoirs, mining, oil+gas (tar sands) : resource extraction

2.2forested¶

• populated and remote regions
• 45% tree cover
• semiwild
• new england, USA

2.3rangelands¶

• grazing lands, dry areas
• residential or populated or remote
• original vegetation, animals

2.4croplands¶

• 25% tree cover
• remote, residential,

2.5villages¶

• densely populated but primarily agriculture
• anthromes: rice, irrigated, pastoral, rained

2.6urban and dense¶

• also includes suburban - lawns naturally wouldn't be there

2.7glaol summary¶

• 80% population in urban/village
• land: 23% wildlands, 77% antrhopogenic biomes
• net primary productivity: 11% wildlands, 89% anthropogenic

2.8metrics¶

• embeddedness - % of land not used by humans where humans exist
• intensification - moderate: ecosystem is largely intact, substantial: range lands, new animals, major change: croplands, profound: villages, maximal: urban areas
• china, nigeria, germany, indue, east asia - completely changed
• age of novel ecosystems dependent on new world vs old world
• biggest change over last 300 yrs is in asia - transition to villages