#21 Agricultural Ecosystems

Question 1

Agroecosystem

Answer 1

The domesticated intermediate between natural and fabricated ecosystems (cities)

Question 2

Agroecosystem examples

Answer 2

• energy sources are processed fuels
• reduced diversity to maximize yields
• artificial selection rather than natural selection
• the control is external and goal oriented via subsystem feedback as in natural ecosystems

Question 3

Agroecosystem Energetic Processes (input, output, and input/output)

Answer 3

Input: sunlight, human and animal labour, mechanized energy, and chemical
Output: crop, vegetable, and animal products
Input/Output: pre-industrial, semi-industrial, and full industrial stages

Question 4

Agroecosystem Biogeochemical Processes (input and output)

Answer 4

Input: nutrients released from soil, fixed from atmosphere, absorbed from water, fertilizers, food, and feed, returned as manure.
Output: Nutrients in crop or livestock consumed on or exported from the farm, leaching, losses due to denitrification, burning, runoff, and erosion.

Question 5

What are some other agroecosystem processes?

Answer 5

• hydrological
• successional
• biotic regulation (pest management)

Question 6

stability of agroecosystem

Answer 6

the consistency of production under a given set of environmental management conditions, or the given degree of variation from year to year

Question 7

Sustainability of agroecosystems

Answer 7

the ability of an agroecosystem to maintain production through time, in the face of long-term ecological constraints and socioeconomic pressures.

Question 8

Why are agroecosystems considered unstable and unsustainable?

Answer 8

• low biodiversity and structural complexity (monoculture)
• Loss of the successional stage (ability to cycle nutrients, conserve soil, and regulate pest populations)
• System becomes dependant on human intervention to function

Question 9

Ecological Consequences of Agroecosystems

Answer 9

• Water Pollution: runoff contains high N and P levels
• Loss of Top Soil: by wind and water, plant communities and associated herbivores can become extinct
• Fossil Fuel Dependance
• Soil Salinization: from continuous irrigation
• Dessertification: from severe grazing
• ## habitat loss and loss of diversity

Question 10

Emerging ecological consequences of agroecosystems

Answer 10

• gmo’s
• biofuels
• climate change

Question 11

what is the agroecosystem solution?

Answer 11

changing the view from maximizing yield and profit in the short-term, to a sustainable productivity system

Question 12

Why are traditional farming practices receiving recent attention?

Answer 12

• energy efficient
• ecologically sustainable
• providing adequate food for local populations

Question 13

What are the benefits of Shelterbelts

Answer 13

• reducing wind and increasing survival for livestock
• Increased vegetation increases diversity
• pollination benefits

Question 14

What was the worlds largest ecological project in the world?

Answer 14

three-north shelter-belt

Question 15

How does temperature affect dormancy?

Answer 15

low temperature reduces dormancy, high temperature increases dormancy as it occur s in the spring