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Agroecology > Final > Flashcards

Final Flashcards

1
Q

What two types of biotic interactions exist?

A

Direct and Indirect.

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2
Q

What is direct biotic interaction?

A

When an organism directly affects another organism, like eating the other organism.

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3
Q

What is indirect biotic interaction?

A

Indirect interaction is when an organism indirectly affects another organism, such as changing the environment.

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4
Q

What three types of indirect biotic interactions did we talk about?

A

Removal interference - removes a resource (such as light, water and nutrients)
Additive interference - adds something to the environment that negatively affects another organism
Facilitation - adds something to the environment that positively affects another organism

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5
Q

What is commensalism and what is an example of it?

A

Commensalism is when species a needs species b to survive while it makes no difference to species b. An example is shade plants such as trees that provide shade to coffee plants.

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6
Q

What is mutualism & protocooperation and an example?

A

Mutualism is an obligate interaction and protocooperation is not obligate but they benefit from an interaction. An example is plants and pollinators.

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7
Q

What is amensalism and an example?

A

Species A is harmed by the presence of species B. Plants that produce allelopathic compounds.

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8
Q

What is the difference between intraspecific competition and interspecific competition?

A

Intraspecific competition is a competition between the same species and interspecific is a competition between different species.

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9
Q

How does interspecific and intraspecific competition play into agriculture?

A

Intraspecific plays into agriculture with planting densities and interspecific is all about weeds and other pests affecting yo yield.

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10
Q

What is multiple cropping?

A

A means of increasing diversity in agroecosystems, generally, by growing two or more crops in a year.

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11
Q

What are the time and space elements of multiple cropping?

A

Time refers to two or more crops of the same crop in a year, no diversity benefit, or rotation between two or more different crops. Space component involves multiple crops in space = intercropping.

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12
Q

What is relay cropping?

A

Multiple crop in time and space.

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13
Q

What are some mechanisms of intercrop interactions? (What do you want to limit and/or promote?)

A

Limit the competition between intercrops and promote the facilitation that one crop might have on another crop (legume with a cereal).

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14
Q

What is LER and how do you calculate it?

A

Land Equivalent Ratio, most common measure used to see if intercropping is over yielding or under yielding. LER = (P1/M1) + (P2/M2)

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15
Q

What consideration should be made in regards to LER? Is it an absolute measure?

A

No, it is not an absolute measure. The total yield may not be the most critical measure to a farmer. The yield of one particular crop may be more important - so maximize the yield of that crop. Also, the quality of the crop is important - calc. marketable yield also.

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16
Q

What is RVT and how is it calculated?

A

Relative value total. RVT = (acorn + bPbean)/aMcorn

The highest value crop is divided for mono crop.

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17
Q

What does RVI calculate?

A

The relative value of the intercrop. Takes into account the reduced cost of purchased input if the intercrop reduces/eliminates the need to purchase such inputs.

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18
Q

Identify 4 ecological principles to aid in design.

A

Spatial and temporal heterogeneity. Importance of disturbance in ecosystem structure and function. Perennialism is the most common condition in natural vegetation. Structural and functional diversity important but hard to quantify.

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19
Q

What are 5 benefits of trees in agroecosystems?

A

Positive microclimate effects, maintain or increase soil fertility, maintain or increase soil organic matter, reduce soil erosion, and harvest potential increase.

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20
Q

How do trees effect the microclimate of a system?

A

Lower soil temperature, alter soil moisture, minimize temperature fluctuations, shade effects and reduce wind. Resistance/resilience effects - moderate extremes?

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21
Q

How do trees maintain or increase soil fertility?

A

Biological nitrogen fixation if the tree is leguminous, reduced nutrient loss from runoff, nutrient pumping from sub-soil -> litter-fall, root turnover, and root exudate.Resistance/resilience effects - retain nutrients

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22
Q

How do trees help a system maintain or increase soil organic matter?

A

From leaf litter, root turnover, and root exudates, lack of disturbance. -> improves soil physical qualities and nutrient availability. Increases microbial activity - suppressive soils? Resistance/resilience effects - improve soil stability.

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23
Q

How do trees reduce soil erosion in a system?

A

Via cover of canopy and mulch on soil surface, as a barrier on slopes to catch and slow down runoff, and the roots hold soil in place. Resistance/resilience effects - retain good topsoil

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24
Q

How do trees add to the harvest potential?

A

By increasing the diversity of products that the system can harvest. Tree crop = fruit, nut, leaves, fodder, wood products, medicinal products. Resistance/resilience effects - diversity of income/food sources

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25
Q

Define agroforestry and give 5 examples.

A

Agroforestry is the intentional combining of agriculture and working trees to create sustainable farming and ranching systems. Silvopasture, windbreaks, riparian buffer, forest farming, alley cropping.

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26
Q

What is a windbreak and a few benefits?

A

Plantings of single or multiple rows of vegetation that are established for one or more environmental and economic purposes. Benefits: manage snow, reduce soil erosion, aesthetics, reduce airborne chemical drift, increase carbon storage, reduce energy needs.

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27
Q

Why is height important for a windbreak and what does it determine?

A

Height is important because it determines the distance of the downwind sheltered (protection) zone.

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28
Q

Why is density important for a windbreak?

A

Dense maximum wind reduction but short wind shadow. Moderately dense less wind reduction but longer wind shadow.

29
Q

Why is orientation for windbreak important?

A

The location or layout directly influences area protected and effects vary with critical weather periods and wind directions.

30
Q

Why is width important to a windbreak?

A

Density, wildlife values and trapping capacity and efficiency.

31
Q

Why is continuity important to a windbreak?

A

Gaps increase the speed of wind as it flows through

32
Q

What is silvopasture?

A

Combines timber livestock and forage production on the same acreage. Trees provide long-term return, while livestock and forages generate an annual income.

33
Q

Name some silvopasture benefits.

A

Improved plant vigor, lower animal stress -> lower vet bills increase milk and weight, reduced wildfire risk. Annual income.

34
Q

How does silvopasture benefit wildlife?

A

Sufficient food supplies, suitable cover, well distributed water, and adequate habitat.

35
Q

What and where are riparian forest buffers?

A

An area of mostly trees or shrubs located adjacent and up gradient from water that is capable of supporting woody vegetation.

36
Q

What is a riparian used for?

A

To create shade to lower water temp and improve habitat for cold water aquatic organisms, provide detritus and large woody debris for aquatic and terrestrial organisms, reduce runoff.

37
Q

To capture runoff what should one understand in setting up the buffer?

A

Where the source contaminates are and what they are so you can locate the buffer down-gradient. Contaminants may be transported by surface runoff or concentrated flows or subsurface flows -> subsurface flows mainly pass buffer root systems.

38
Q

What is the relationship between floodplains and riparian buffers?

A

They reduce floodwater velocity and erosive power, stream debris is blocked from entering farms, grasslands or urban lands, roots hold stream banks and keep the soil in place

39
Q

What is alley cropping?

A

Planting of trees or shrubs in two or more sets of single or multiple rows with agronomic, horticultural, or forage crops cultivated in the alleys between the rows of woody plants.

40
Q

How does alley cropping improve crop diversity and economic returns?

A

By allowing for annual crops for cash flow while growing long term woody investments. Allows two crops to be grown on the same acreage such as a forage or row crop and nut or fruit crop. Improves soil nutrients and utilization/recycling -> decreases off site movement of nutrients or chemicals

41
Q

What are downsides to alley cropping?

A

Intensive management, can remove land from annual production depending on the tree choice, can complicate herbicide application, and requires certain tools and infrastructure for woody products.

42
Q

What should be considered when planning an alley crop?

A

Light requirements for the crop grown in between trees, root competition between crops, type and size of the equipment being used.

43
Q

What is alley cropping seen as an alternative to?

A

Slash and burn for the developing world by incorporating an improved permanent fallow phase

44
Q

What would a researcher look for when selecting a hedgerow species? Farmers?

A

Minimize competition between trees and crops, synchronized nutrient release and crop uptake, maintenance of SOM, nutrient yields from pruning. Farmers: Impacts on crop yields, alternative harvest, labor requirements

45
Q

Name some findings from alley cropping study about yields in the short term.

A

Alley cropping didn’t work in very dry climates or infertile soils. Small amounts of fertilizer or better adapted species may help but if fertilizer is expensive then there is no economic incentive.

46
Q

Some findings for alley cropping in the long term.

A

Needs sufficient time to operate >5 years, yields compared to system without trees increases with time (low fert. led to failure in increased yield). Takes 3 years to detect the change. C, N, and P increased in proportion to amount of prunings in Nigeria

47
Q

Why was farmers response to alley cropping disappointing?

A

Increased labor demand, level of skill needed for pruning and such, initial loss of yields, risk, and competition for use of prunings.

48
Q

Why is it beneficial to have patio/temporal diversity?

A

For biocontrol because natural enemies can have a place to live rather than in a fully synchronized system all insect populations will crash and natural enemy life cycle will take too long before pests do damage. Also, brings stability to input costs, labor requirements, and harvest prices.

49
Q

Trap crop = ?

A

Annuals that are designed to attract pests away from cash crops

50
Q

How do you measure a sustainable system (5 things)?

A

Producing enough yield, economically viable in long run, is it preserving or enhancing the quality of natural resources, enhancing quality of life, resilient and adaptable to change.

51
Q

How did conventional practices lead to a loss of biodiversity in ag?

A

Conventional practices work primarily to manage a few factors perceived to be of direct importance to the system - crop plants, NPK, tillage/herbicides and insecticides -> simplification and homogenization

52
Q

What is the “challenge” about biodiversity to an agroecologist.

A

Understanding the identities of the larger unplanned biota to find what functions they serve and what value we may gain from their functions. To analyze how management practices can be modified to optimize biodiversity while taking into consideration both the short-term and long-term goals.

53
Q

What does alpha diversity measure?

A

Species richness and abundance within a community.

54
Q

What does beta diversity measure?

A

species diversity across communities or along gradient transects

55
Q

What does game diversity measure?

A

species diversity across a biogeographic region

56
Q

What does species richness do and what index can be used to better represent diversity?

A

Species richness represents the number of species and does not take into account evenness and gives a great influence to rare species. The shannon-weiner index accounts for number of species and evenness

57
Q

Which functional redundancy brings the most resilience and stability?

A

A partial overlap or diversified portfolio where species thrive at common points but they also have individual ranges that allow the system to be resilient to changes.

58
Q

How does structural diversity work?

A

Different layers or types of areas for organisms to live -> terraces and ponds, different levels of canopy in trees. Coffee plants shaded by trees, rice terraces, living fence

59
Q

Do intercrops reduce pest damage, what are the two hypothesis?

A

Enemies hypothesis: increase in predators and parasitoids due to increased availability of alternate food sources.
Resource concentration hypothesis: more difficult for pests to find desired host and/or tend to leave more quickly.

60
Q

How are rice systems in Java an example of spatio/temporal diversity?

A

Flooded fields all for natural enemies to feed on detritus feeders even when rice pest not present, provides a year round food source for natural enemies.

61
Q

Three levels of stability and a measure or two.

A

Ecosystem level: nutrient cycling, soil erosion
Community-level: species richness, functional redundancy, insect pest suppression, disease suppression.
Economic level: yield/cost/price, input availability, demand for labor, overall profit and sustainability

62
Q

How did farmers in Malawi cope with high elevation (being more isolated)?

A

By planting a high varietal diversity.

63
Q

What were some major concerns for Senegal rice?

A

Imports too much, river is main irrigator, salinity issues near coast, limited access to inputs

64
Q

What was the conclusion of SRI?

A

Farmer hybrid system resulted in a 40% reduction in herbicide us by doing one weeding and spot herbicide later.

65
Q

What is no till?

A

Less than 25% row width disturbance. Left undisturbed from harvest to planting, planting done in narrow seedbed or slot created by coulters. Weed control accomplished mainly with herbicides.

66
Q

What is ridge till?

A

Soil is left undisturbed from harvest to planting. Residue left on the surface

67
Q

What is mulch till?

A

Soil surface disturbed prior to planting

68
Q

What are some limitations in conservation tillage?

A

Bed temperatures may be lowered, macropores develop over time possibly increasing the leading of pesticides, soil chemistry may be altered detrimentally (plant reside can make soil more acidic), poor plant establishment.

Agroecology (3 decks)

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