Quiz 4 Flashcards
What was increased through diversification of landscapes and cropping systems?
Agroecosystem performance and resilience.
What are some of the effects of increased biological diversity noted in a recent review by Cardinale et al. (2012)?
Greater productivity, greater carbon sequestration, greater retention of nutrients, and greater ability to resist and recover from various forms of stress, including herbivorous pests, diseases, droughts, and floods.
What are some benefits of resilient agroecosystems?
- Better able to withstand and recover from disturbances due to pests, weather, and other biophysical factors
- Better able to withstand and recover from disturbances due to pests, weather, and other biophysical factors
What meand: In general, the relationship between biological diversity and ecosystem function resembles an asymptotic hyperbola? (Cardinale et al., 2012)
That is, increases in the number of species present in an ecosystem from a very low level to some intermediate level engender large changes in ecosystem function, whereas increases in species richness above some intermediate, and undetermined, value engender smaller effect
What was the analogy Professor Shahid Naeem of Columbia University used to explain about loosing species diversity?
Imagine using a needle nose pliers and remove parts from a super computer and see if it will still works as well as before.
Industrial agriculture has been characterized by large reductions in ______________?
Biological diversity both across landscapes and within farming systems (DeFries et al., 2004; Vandermeer et al., 2005).
Simplification of crop and non-crop vegetation in the Corn Belt has been a strategy pursued through decisions and actions of individual farmers and through federal and state policies had what goals?
- Producing huge amounts of corn
- Producing huge amounts of soybean
- Producing huge amounts of chicken
- Producing huge amounts of cattle
- Producing huge amounts of hogs
- Producing huge amounts of ethanol
- Producing huge amounts of farm revenue
What are the emerging and continuous challenges that started threatening the Corn Belt?
- Soil erosion
- Water quality degradation by nutrient and pesticide emissions
- Greater prevalence of herbicide-resistant weeds
- Volatility in production costs and crop prices
- Loss of knowledge and infrastructure to support diverse markets
- Declines in rural community vitality
- Nitrogen into the Gulf of Mexico
Corn and soybean have replaced native, perennial species whose deep roots and long growth period from early spring to late fall. How these perennials were better than the crops?
- More effective holding the soil in place
- Promoted water infiltration
- Transpiration into atmosphere
- Fostering carbon sequestration
- Nutrient retention
The consequences of this shift in vegetation are illustrated by results from an experiment conducted in Illinois comparing nitrate-N losses to drainage water from two annual crops—corn and soybean—and a reconstructed, multispecies prairie community harvested for biomass. What was the results?
After a two-year establishment period for the perennial prairie species, loss of leached N was 9- to 18-fold greater from the annual crops than from the prairie community (Smith et al., 2013).
The effects of integrating diverse, deep-rooted communities of perennial plants into landscapes and watersheds dominated by row crops are being investigated in experimental watersheds in central Iowa in which strips of reconstructed prairie have been interwoven into corn and soybean fields. What were some of the results?
When compared to 100% row-crop watersheds managed without tillage:
- There was a 95% reduction in sediment export
- 90% reduction in total phosphorus export
- 85% reduction in total nitrogen export from watersheds containing 10% prairie
- Additional benefits for biodiversity conservation of plants and birds have been documented in these experimental watersheds.
- One of the least expensive conservation practices ($60 to $85/ha)
- Biodiversity-ecosystem function relationships can be highly non-linear
Impacts from using the prairie system
Positive: may be increasingly important as a shift in the region’s climate regime toward a greater frequency of high intensity rainfall events threatens agroecosystem resilience by increasing soil erosion and crop damage, even in zero-tillage systems
Negative: though yields of corn and soybean per cropped hectare were unaffected by the presence of the prairie conservation strips, total production of corn and soybean were reduced 10% due to the substitution of prairie vegetation for crops
Conclusion: increases in soil, water, and nature conservation involved a trade-off with crop production.
Can monocultures of perennial species offer benefits?
Monocultures of perennial species can also confer substantial environmental benefits
The type and level of benefit varies with plant species and management
(Asbjornsen et al., 2014)
Which is better:
Short rotation sequences and monocultures
or
Extended rotation sequences that included multiple crop species?
A recent review by Bennett et al. (2012) found yield reductions from 3 to 57% for major crops grown in short rotation sequences and monocultures relative to yields in extended rotation sequences that included multiple crop species.
Cite some of the factors that lower the productivity in less diverse rotations
- Increased prevalence and greater damage from insect pests and weeds
- Deleterious interactions with soil microbes and nematodes
- Soil compaction
- Nutrient depletion
- Self-inhibition due to toxic compounds from plant exudates
- Reduced soil water availability.
