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Agroecology > FINAL4 Trees in agroecosystems > Flashcards

FINAL4 Trees in agroecosystems Flashcards

0
Q

Microclimate effects

A 
lower soil temperature
alter soil moisture
minimize temperature fluctuations 
Shade effects
Reduce wind 
Resistance/resilience effects – moderate extremes?
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1
Q

4 ecological principles to aid in design:

A
  1. spatial and temporal heterogeneity
  2. importance of disturbance in ecosystem structure and function
  3. perennialism is the most common condition in natural vegetation
  4. structural and functional diversity important but hard to quantify

(Emphasize need to understand and manipulate tree/crop interactions in design of agroforestry systems)

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2
Q

Maintain or increase soil fertility

A

biological nitrogen fixation (if leguminous or associated with Frankia symbiosis)
reduce nutrient loss
nutrient pumping from sub-soil (how significant?)
litterfall, root turnover, and root exudate
Resistance/resilience effects – retain nutrients?

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3
Q

Maintain or increase soil organic matter

A

from leaf litter, root turnover, and root exudates, lack of disturbance
improved soil physical qualities and nutrient availability
increases microbial activity - suppressive soils?
Resistance/resilience effects – improve soil stability

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4
Q

Reduce soil erosion

A

via cover of canopy and mulch on soil surface
as barrier on slopes to catch and slow down runoff
roots hold soil in place
Resistance/resilience effects – retain good topsoil

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5
Q

Harvest potential

A

increased diversity of products
tree crop products (fruit, nuts, leaves),fodder, wood products, medicinal products, plus whatever is produced between the trees

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6
Q

Resistance/resilience effects

A

diversity of income/food sources

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7
Q

What is Agroforestry?

A

the intentional combining of agriculture and working trees to create sustainable farming and ranching systems.

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8
Q

What is a windbreak?

A

Plantings of single or multiple rows of vegetation (trees, shrubs, grass) that are established for one or more environmental and economic purposes

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9
Q

What are the benefits to windbreaking?

A 
Reduce soil erosion
Protect plants
Enhance plant growth
Manage snow
Provide shelter
Reduce energy needs
Improve wildlife habitat 
Enhance aesthetics
Moderate noise  
Screen views
Reduce airborne chemical drift
Improve irrigation efficiency
Increase carbon storage
Mitigate odors
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10
Q

What are the effects of windbreaking?.

A

Windbreaks:
lower wind velocity causing air-borne material to be deposited
physically trap air-borne material
adsorb some of the chemicals attached to air-borne material
alter the microclimate on the downwind side of the windbreak

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11
Q

Why is density important for windbreaks?

A

Dense: maximum wind reduction but short wind shadow

Moderately dense: less wind reduction but longer wind shadow

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12
Q

Why is orientation important for windbreakers?

A

Location or layout:
Directly influences area protected
Effects vary with critical weather periods and wind directions

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13
Q

Why is length important for windbreakers?

A

For full protection, the windbreak needs to extend the entire length of the area needing protection to account for changing wind directions.
Doubling the length of a windbreak will generally increase the area protected by 4 times

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14
Q

Why is height important for wind breakers?.

A

H = Effective height of the windbreak

The height determines the distance of the downwind sheltered (protection) zone

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15
Q

Why is width important of windbreakers?

A

Width influences:
Density
Wildlife values
Trapping capacity and efficiency

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16
Q

Why is continuity important for winbreakers?

A

Wind speed increases in a gap

Gaps in the windbreak can result in damage or complications downwind

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17
Q

Types of windbreaks:

A

-field
-livestock
-

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18
Q

Multi-purpose windbreaks

A

Bio-energy feedstock
Food security
Wildlife
Income products

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19
Q

What is silvopasture

A

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

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20
Q

Management System Components

A

trees-forages-livestock

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21
Q

Silvopasture Benefits

A 
Improved plant vigor
Lower animal stress
Reduced wildfire risk
Improved wildlife habitat
Annual income
Long-term income
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22
Q

Silvopasture Benefits-lower animal stress

A

Increased weight gain
Increase milk yields
Higher conception rates
Lower veterinarian bills

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23
Q

Silvopasture Benefits-reduced wildfire risks

A 
Reduced: 
Stand density
Ladder fuels
Fuel loading
Winds
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24
Q

Silvopasture Benefits-Improved wildlife habitat

A

Sufficient food supplies
Suitable cover
Well distributed water
Adequate habitat

25
Q

Riparian Forest Buffer

A

What: An area of predominantly trees and/or shrubs located adjacent to and up-gradient from watercourses or water bodies
Where: On areas adjacent to permanent or intermittent streams, lakes, ponds, wetlands and areas with ground water recharge that are capable of supporting woody vegetation.

26
Q

Use Riparian Forest Buffers to:

A

Create shade to lower water temperatures & improve habitat for cold water aquatic organisms
Provide a detritus and large woody debris for aquatic and terrestrial organisms
Create wildlife habitat and establish wildlife corridors
Restore natural riparian plant communities
Reduce excess amounts of sediment, organic material, nutrients and pesticides in surface runoff and in shallow ground water flow
Provide a harvestable crop of timber, fiber, forage, fruit etc.
Protect floodplain integrity
Increase carbon storage

27
Q

Riparian Forest Buffer Design Considerations

A

Three-zone buffer system
Buffer widths and zones influence use and functionality
Minimum zone widths will vary by region

28
Q

Riparian Forest Buffer Reduce excess contaminants

A

Understand the source contaminants and locate the buffer down-gradient from them.
Contaminants (sediment, chemicals, etc.) may be transported by surface sheet runoff or concentrated flows or by subsurface flows.
Subsurface flows in many settings bypass riparian buffer root systems

29
Q

Riparian Forest Buffer Provide floodplain protection

A

Riparian buffers reduce floodwater velocity and erosive power
Stream debris is blocked from entering cropland, grassland, and urban lands
Roots hold stream banks and keep the soil in place
Peak storm flows may be reduced, lowering flooding levels

30
Q

Riparian Forest Buffer Provide detritus and woody debris

A

Detritus and large debris are particularly important for stream/riparian food chains
Placement in close proximity to the stream or water body insures that some leaf drop, twigs, and other detritus (and eventually large woody debris) enters the aquatic system.

31
Q

Riparian Forest Buffer Create wildlife habitat

A

Use widths to match desired conditions
Value of riparian habitat increased if adjacent upland habitat is created
Natural tree mortality can increase habitat diversity
Full site functionality takes time

32
Q

Restore natural plant communities

A

Wildlife benefit from a mosaic of natural plant communities
Connect fragmented riparian forests.
Isolated patches may be under-utilized or act as a magnet for predators
Use native species where ever possible

33
Q

Riparian Forest Buffer Provide harvestable crops

A

Marketable products depend on current and future demand.
Potential products:
wood (sawlogs, post, poles, veneer)
fiber (pulp, firewood, energy biomass)
forage (livestock)
fruit (nuts, berries)
other crops (ginseng, mushrooms, herbs and floral greenery, etc.)

34
Q

Riparian Forest Buffer Increase carbon storage

A

Riparian buffers are effective at storing carbon
Trees grow rapidly in riparian zones due to favorable moisture and nutrient conditions
Net carbon benefits are realized if the wood fiber is used for solid wood products or fuel

35
Q

What is Alley Cropping

A

the 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.

36
Q

Alley Cropping Benefits

A

Improves crop or forage quality and quantity by enhancing microclimate;
Improves the microenvironment to increase crop yieldsProtects alleyway crops from physical damage from winds

37
Q

Alley Cropping Benefits

A

Improve Crop Diversity, and Economic Returns
Allows production of annual crops for cash flow while growing longer term woody investments.
Allows two crops to be grown on the same acreage such as a forage or row crop and nut or fruit crops
Allows crop diversity which reduces risk

38
Q

Alley Cropping Benefits

A

Increases net carbon storage in the soil and vegetation
Roots, crop residue, leaves and forage add to soil carbonTrees add to total carbon stored on site through sequestration in the above ground and below ground biomass

39
Q

Alley Cropping Benefits

A

Improves utilization and recycling of soil nutrients
Tree roots are generally deeper than crop roots
Nutrients and chemicals that pass through crop root zone are intercepted by trees
Nutrients are utilized by the trees and recycled back to the soil surface by leaf drop

40
Q

Alley Crop Benefits

A

Decreases off site movement of nutrients or chemicals - surface
Trees planted on contour trap sediment and residue along with attached nutrients and chemicals
Infiltration increases in tree rows decreasing overland flow and associated movement of soluble nutrients and chemicals off site

41
Q

Alley Cropping - Issues

A

Involves intensive management
May remove land from annual production, depending on the tree crop
May complicate herbicide application
Requires marketing infrastructure for woody plant products

42
Q

Alley Cropping-Design Considerations

A

Light requirement for the crop or forage to be grown in the alley way
Root Competition between crops
Type and size of the equipment being used

43
Q

Tree or Shrub Criteria for Alley Cropping

A

Marketable
Yields annual or periodic commercial product (wood, nuts or fruit)
Appropriate shade for the alley crop
Minimal roots at soil surface
Adapted to site and soils
Foliage residue does not interfere with alley crop
Growth requirements complement alley crop

44
Q

Alley Cropping - tropics

A

fast-growing trees and shrubs established in hedgerows on arable cropland and annual food crops are cultivated in the alleys between the hedgerows.
Hedge prunings are used as soil mulch for fertility and soil improvement rather than for harvest as fodder, fuelwood, or food
Hedgerows are typically spaced 4-10 m apart

45
Q

History of Alley Cropping

A

Seen as an alternative to slash-and-burn for the developing world

Basically incorporates an improved permanent fallow phase
slows loss of nutrients add organic matter and nutrients via prunings

46
Q

History of Alley Cropping

A

Alley cropping was developed in 1976 at the International Institute of Tropical Agriculture (IITA) in Nigeria
Very attractive to research scientists
easy to design multi-factorial trials of species, spacing, and management.
More research done than for all other agroforestry techniques put together

47
Q

Main objectives of alley cropping

A

Improve soil quality

Reduce soil erosion from cultivation on steep slopes

48
Q

Criteria for Hedgerow Species Selection - Researchers

A

Minimize competition between trees and crops (light, moisture, nutrients)
looked at variation in root structure and N - fixation (by leguminous tree species)
Synchronized nutrient release and crop uptake
Optimize litter decomposition and nutrient release patterns - affected by quality of litter (C/N ratio, lignin and polyphenols)
Maintenance of soil organic matter
from litter, prunings, root decay and exudates etc.
Nutrient yields from pruning
quantity and quality of biomass produced

49
Q

Criteria for Hedgerow Species Selection - Farmers

A

Same as researchers plus…
Impacts on crop yields
Provide alternative harvest products: food, fodder and fuelwood
Labor requirements: quantity and timing of pruning and other management

50
Q

Hedgerow Biophysical issues

A

Soil fertility:
Improvement a long term process via SOM build up.
Little direct movement of nutrients from mulch into crops (10-20% of N)
Recycling of nutrients (especially P) insufficient to replenish nutrients removed in harvested crop.
Supplemental fertilizers greatly improve yields in most systems
tree-crop competition highest in low fertility sites and gets worse over time
low P greatly reduces N fixation and hence N input

51
Q

Hedgerow Biophysical issues 2

A

Soil fertility contd.
Timing - need to synchronize N release with crop demand
Lignin and polyphenols in mulch slow decomposition
Trade off between rapid N release and weed suppression ability of the mulchLight effects:
Need careful spacing and pruning management to provide canopy closure in fallow period for weed suppression, and cut the canopy back during crop cycle

52
Q

Alley cropping Performance - short-term yields

A

Disappointing yields:
improved in 17 of 40 trials investigated including “on-station” trials
Found that alley cropping didn’t work in very dry climates or on infertile soils
Applying small amounts of fertilizer or finding better adapted species may help
no economic incentive to plant trees if fertilizers are very inexpensive

53
Q

Alley Cropping Performance: Long-Term Yield

A

Evaluated after long-term interactions have sufficient time to operate (>5 yrs)
criteria–> that yields compared to system without trees increases with time
in 10 out of 12 trials alley cropping led to higher yields
the two failures come from low fert. sites

54
Q

Alley Cropping Performance - Soil Improvement

A

Long-term yields strongly dependant on soil improvement
takes at least 3 yrs to detect changes
soil properties improvement usually related to increased SOM
on-station trials in Nigeria, soil C, N, and P increased in proportion to the amount of prunings
From 20 other studies, 50% show large and 25% show moderate improvement

55
Q

Alley Cropping Performance -Farmers Response

A

Ultimate test of any agroforestry system is the spontaneous adoption by farmers
Disappointing in the extreme
problems:
increased labor demand
level of skill needed (pruning and it’s timing)
initial loss of yields,
risk
competition for use of prunings - soil mulch, fodder, firewood etc.?

56
Q

Lessons learned from Tropical Alley Cropping Experience

A

Difficult trade-offs in farmer adoption
management complexity, loss of cropland, lack of familiarity with pruning, lack of effective farmer education
On-station results may differ from on-farm results
May be better ways to harness the soil-improving qualities of trees - less management intensive?

57
Q

Lessons learned from Tropical Alley Cropping Experience -2

A

Need for supplemental fertilizers to maintain yields
Need research on trees adapted to dry systems
Long-term results could outweigh the short-term losses (note: original intent of these systems was to halt degradation). Shown to effectively reduce erosion on sloped land.

58
Q

What makes a system sustainable?

A

To continue to meet the goals outlined above the system must:
be sufficiently productive
use resources efficiently – minimize undesired waste
be resilient and adaptable to changing conditions (climate, weather, market, fuel supply, labor availability etc)

59
Q

How do we know a system is moving towards sustainability?

A

Need measures of performance or indicators for each goal

Look at trends over time

Agroecology (11 decks)

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