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BLG 311 (61)
Lecture

human activities

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Department
Biology
Course
BLG 311
Professor
Ross Mc Naughton
Semester
Summer

Description
Deforestation  Clearing of forests for agriculture or buildings; cleared areas may be mined for mineral ores; timber obtained may be used for paper, charcoal, furniture, building material  Reduces transpiration, rainfall, humidity o Increases risk of fire  Increases velocity of rain reaching the soil o Soil erosion / leaching of ions  Reduces biodiversity o More extreme environment / abiotic factors increase / unstable ecosystem o Change in (micro)climate / levels of light / temp / humidity o Loss of niches/habitats and complex food webs o Animals move away/higher death rate/extinction  Lower biomass and productivity per hectare Effect on Nitrogen Cycle  Growth in human population is increasing the demand for agriculture o for land for farming o for grazing land to provide animal protein  Many decomposing fungi live in association with roots of trees o Less NH4+ can be absorbed by plants from decomposition o The soil itself is often a poor source of mineral ions o Thus, reduced input in the nitrogen cycle; slower and less recycling of NH4+  Nitrogen in soil is lost as smoke but ash is still rich in nutrients for crops o Yield falls with subsequent crops o Crops are harvested before they die/decompose o Nitrogen is not recycled and not returned to the soil o Fertilisers (NO3, NH4+) make up that loss o Ions from fertiliser readily leach out of the soil by rain into lakes and rivers o Increases growth of algae and water plants  [EXAM] Ploughing increases the activity of nitrifying bacteria in the soil o Oxygen enters the soil o Nitrifying bacteria are aerobic o Convert ammonia/ammonium ions to nitrite, nitrite to nitrate o Nitrate is absorbed/used by plants o To make protein/amino acids/DNA/ATP/NAD(P)/chloroph
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