FINAL3-BIODIVERSITY Flashcards by Nessa Scott

Unplanned Biodiversity

Weeds (in field)
Surrounding (none – all)
Soil Biota
Arthropods (except releases of biocontrol agents)
Non-domesticated animals

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Planned Biodiversity

Crop Varieties
Some surrounding vegetation (none – all)
(e.g., other monocrops, intercrops, non-crops)
Domesticated animals

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Loss of Biodiversity in agriculture

Conventional practices

Conventional practices work primarily to manage a few factors perceived to be of direct importance to the system
The crop plants
A few nutrients (N,P,K)
Tillage/herbicides
Insecticides

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Loss of Biodiversity in agriculture

TREND:

simplification / homogenization

Homogenization + Simplification = Productivity/Profitability

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Biodiversity: The Challenge

As agroecologists: the challenge we face is to:

try and understand what the identities of the larger, unplanned biota,
what function they serve,
what value we wish to assign to their functions,
How management practices can be modified to optimize biodiversity, taking into consideration both short-term (profit) and long-term (sustainability) goals

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Biodiversity includes:

genetic variability~

Within and between species

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Biodiversity includes:

Alpha diversity~

Measure of a species richness and abundance within a community

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Biodiversity includes:

Beta Diversity~

species diversity across communities or along gradient transects

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Biodiversity includes:

Gamma Diversity~

Species diversity along a biogeographic region

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Identifying biodiversity

Alpha biodiversity!~

Spatial component: Within field

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Identifying biodiversity

Beta Diversity!~

Spatial Component:

Number and evenness of species over a landscape

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Gamma Diversity!~

Number and evenness of species over region

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Can you have a high alpha biodiversity low beta biodiversity agroecosystem?

YES

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Shannon-Weiner index

Accounts for #species and evenness

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Ecosystem functions:

Processes critical to ecosystem vitality
Nutrient, water, air cycling
Biomass production
Decomposition

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Ecosystem services:

Functions that are valued by us
Pollination services
Biological control
Soil fertility

Stability

Ability to withstand disturbance

resistance

ability to resist stress

resilience

ability to recover after stress

Biodiversity…

alpha diversity: species richness and relative abundance, planned & unplanned)

Genetic Diversity

within species

Structural Diversity…

*or Habitat Diversity defined in 4-parts:

(e.g., Plant architecture, habitat diversity, constructed)
(- Living fences, Deciduous borders)
*Major habitat system: e.g., terrestrial, aquatic;
*Formation type: e.g., woodland, open ground;
*Vertical layers: e.g., ground flora, shrub, high canopy;
-Traditional shaded coffee
systems
*Qualifiers: e.g., deciduous, coniferous, annual, etc

Functional: complexity of interactions among system components
Constructed diversity - terraces, ponds, etc

Temporal Diversity

(e.g., Variable planting times, life histories)

Crop rotation

Spatial Diversity

(e.g., beta diversity of vegetation types, or crop varieties, or crop stages, gamma diversity)
Landscape complexity
(% natural habitat in landscape)

Functional biodiversity

``` Biological pest control Pollination services Nutrient cycling Synergistic interactions eg. -legume/non-legume -Plant mycorrhizae -Microclimate modification – windbreaks, shade Risk aversion: -Multiple products -Spread workload Landscape stability: -Perennial ground cover, hedgerows etc reduce runoff/erosion ```

Functional diversity

Ladybugs and carabids and pea aphid control (Losey 1998)

Do Intercrops reduce pest damage? | Proposed mechanisms include:

Enemies Hypothesis | Resource Concentration Hypothesis

Resource Concentration Hypothesis

more difficult for pests to find desired host and/or tend to leave more quickly

Enemies Hypothesis:

increase in predators and parasitoids due to increased availability of alternate food sources

Effect of polycultures on herbivore populations

decreased population: 52% of studies increased populations: 15% of studies no effect on population of 13% of studies variable effect on population of 20% of studies

Effect of polycultures on natural enemy populations:

increased population: 53% of studies decreased population: 9% of studies no effect on population of 13% of studies variable effect on population of 25% of studies

Non-Synchronous Planting Not Only Leads to More Stable Arthropod Ecology, … but

``` More Stable Labor Requirements More Stable Input Costs More Stable Harvest Prices Left to their own, Farmers Drift away from Enforced Synchronous plantings ```

Summary: Some measures of Stability

``` Ecosystem-Level Nutrient cycling (ability of plant-soil microbe systems to process nutrients) Soil Erosion (physical sustainability of soil system over time) ``` Community-Level Species Richness (conservation as well as agronomic issue) Functional Redundancy (systems “buffered” by multiple species having similar functions)Population-Level Insect Pest Suppression (by “beneficials”) Disease Suppression (e.g., rice blast example) Economic-Level Yield, costs and price stability (reduced reliance on volatile purchased inputs; “spreading the risk” through a variety of crops) Input Availability (avoiding demand “bottlenecks” when costs can rise) Demand for Labor (spread over year to provide stable work force) Overall Profit and sustainability (integrates all of the above)