Environmental Science 1021F/G Lecture Notes - Lecture 3: Crop Yield, Primary Production, Subsistence Agriculture
Course CodeENVSCI 1021F/G
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Food and Land
Ecosystem: Interrelationships between environment and living organisms; energy flow
-30%-40% of global cropland has been environmentally degraded
>we are using it above its sustainable yield
-Fertility of world’s soil reaching
peak that will threaten food
supplies, scientists warn
Soil: mixture of eroded rock,
organic material, nutrients, water,
air, living organisms
-potentially renewable resource,
slowly renewed, filters and holds
water, varying levels of maturity
O horizon: Organic material
provides the base
A horizon: topsoil, the most
nutrient dense horizon, where the
roots and living organisms will be.
Has humus, mostly broken down
B horizon: Fewer organic material,
trees often root here
C horizon: also known as parent
material, where soil begins to be
1) Deciduous soil: large O
horizon because of the
constant organic input
(shedding of leaves)
2) Coniferous forest: A horizon is
not well developed, because needles are acidic, making the soil acidic. A lot colder which
does not make it ideal for organisms breaking down the organic material.
3) Tropical forest soil: lots of rain fall, the nutrients get washed away or get taken up by
4) Desert Soil: rain is absent, not a lot of organic material being input, soil is nutrient poor.
5) Grassland soil: some grasslands are seasonal, they vary, the grass dies. A lot of nutrients.
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