FINAL4 Trees in agroecosystems

Question 0

Microclimate effects

Answer 0

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

Question 1

4 ecological principles to aid in design:

Answer 1

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)

Question 2

Maintain or increase soil fertility

Answer 2

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?

Question 3

Maintain or increase soil organic matter

Answer 3

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

Question 4

Reduce soil erosion

Answer 4

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

Question 5

Harvest potential

Answer 5

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

Question 6

Resistance/resilience effects

Answer 6

diversity of income/food sources

Question 7

What is Agroforestry?

Answer 7

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

Question 8

What is a windbreak?

Answer 8

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

Question 9

What are the benefits to windbreaking?

Answer 9

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

Question 10

What are the effects of windbreaking?.

Answer 10

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

Question 11

Why is density important for windbreaks?

Answer 11

Dense: maximum wind reduction but short wind shadow

Moderately dense: less wind reduction but longer wind shadow

Question 12

Why is orientation important for windbreakers?

Answer 12

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

Question 13

Why is length important for windbreakers?

Answer 13

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

Question 14

Why is height important for wind breakers?.

Answer 14

H = Effective height of the windbreak

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

Question 15

Why is width important of windbreakers?

Answer 15

Width influences:
Density
Wildlife values
Trapping capacity and efficiency

Question 16

Why is continuity important for winbreakers?

Answer 16

Wind speed increases in a gap

Gaps in the windbreak can result in damage or complications downwind

Question 17

Types of windbreaks:

Answer 17

-field
-livestock
-

Question 18

Multi-purpose windbreaks

Answer 18

Bio-energy feedstock
Food security
Wildlife
Income products

Question 19

What is silvopasture

Answer 19

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

Question 20

Management System Components

Answer 20

trees-forages-livestock

Question 21

Silvopasture Benefits

Answer 21

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

Question 22

Silvopasture Benefits-lower animal stress

Answer 22

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

Question 23

Silvopasture Benefits-reduced wildfire risks

Answer 23

Reduced: 
Stand density
Ladder fuels
Fuel loading
Winds

Question 24

Silvopasture Benefits-Improved wildlife habitat

Answer 24

Sufficient food supplies Suitable cover Well distributed water Adequate habitat

Question 25

Riparian Forest Buffer

Answer 25

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.

Question 26

Use Riparian Forest Buffers to:

Answer 26

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

Question 27

Riparian Forest Buffer Design Considerations

Answer 27

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

Question 28

Riparian Forest Buffer Reduce excess contaminants

Answer 28

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

Question 29

Riparian Forest Buffer Provide floodplain protection

Answer 29

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

Question 30

Riparian Forest Buffer Provide detritus and woody debris

Answer 30

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.

Question 31

Riparian Forest Buffer Create wildlife habitat

Answer 31

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

Question 32

Restore natural plant communities

Answer 32

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

Question 33

Riparian Forest Buffer Provide harvestable crops

Answer 33

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.)

Question 34

Riparian Forest Buffer Increase carbon storage

Answer 34

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

Question 35

What is Alley Cropping

Answer 35

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.

Question 36

Alley Cropping Benefits

Answer 36

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

Question 37

Alley Cropping Benefits

Answer 37

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

Question 38

Alley Cropping Benefits

Answer 38

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

Question 39

Alley Cropping Benefits

Answer 39

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

Question 40

Alley Crop Benefits

Answer 40

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

Question 41

Alley Cropping - Issues

Answer 41

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

Question 42

Alley Cropping-Design Considerations

Answer 42

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

Question 43

Tree or Shrub Criteria for Alley Cropping

Answer 43

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

Question 44

Alley Cropping - tropics

Answer 44

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

Question 45

History of Alley Cropping

Answer 45

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

Question 46

History of Alley Cropping

Answer 46

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

Question 47

Main objectives of alley cropping

Answer 47

Improve soil quality Reduce soil erosion from cultivation on steep slopes

Question 48

Criteria for Hedgerow Species Selection - Researchers

Answer 48

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

Question 49

Criteria for Hedgerow Species Selection - Farmers

Answer 49

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

Question 50

Hedgerow Biophysical issues

Answer 50

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

Question 51

Hedgerow Biophysical issues 2

Answer 51

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

Question 52

Alley cropping Performance - short-term yields

Answer 52

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

Question 53

Alley Cropping Performance: Long-Term Yield

Answer 53

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

Question 54

Alley Cropping Performance - Soil Improvement

Answer 54

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

Question 55

Alley Cropping Performance -Farmers Response

Answer 55

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.?

Question 56

Lessons learned from Tropical Alley Cropping Experience

Answer 56

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?

Question 57

Lessons learned from Tropical Alley Cropping Experience -2

Answer 57

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.

Question 58

What makes a system sustainable?

Answer 58

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)

Question 59

How do we know a system is moving towards sustainability?

Answer 59

Need measures of performance or indicators for each goal Look at trends over time