Biodiversity in agriculture ecosystems
What is Biodiversity?
“Our collective life support system!”
Lecture layout:
How do we measure diversity?
Planned and associated biodiversity
How can we effect biodiversity in agricultural
systems?
Biodiversity of insects and microorganisms
Biodiversity
Biodiversity is a measure of
the relative diversity among
organisms present in a
specific ecosystem.
Enhanced biodiversity
enables a host of ecological
services such as pollination,
pest control, and
maintenance of soil fertility
How do we measure diversity
Richness: Number of species/functions
Evenness: How even is the distribution
Shanon diversity Index: accounts for both
richness and evenness
Diversity values 1.61 2.3
Diversity values 1.61 0.77
A B C
1.00E+07 1.00E+07 1.00E+07
1.00E+06 (most diverse) 1.00E+06 1.00E+06
1.00E+05 1.00E+05 1.00E+05
number of cells
number of cells
number of cells
1.00E+04 1.00E+04 1.00E+04
1.00E+03
1.00E+03
H = 6.91 H = 6.71
1.00E+03
H = 6.35
1.00E+02 1.00E+02 1.00E+02
E=1 E = 0.97
1.00E+01 1.00E+01 1.00E+01 E = 0.92
1.00E+00 1.00E+00 1.00E+00
1.00E-01 1.00E-01 1.00E-01
1 200 399 598 797 996 1 200 399 598 797 996 1 200 399 598 797 996
sp. code sp. code sp. code
108 cells, 1000 species
D E F
1.00E+07 1.00E+07
1.00E+07
1.00E+06 1.00E+06
1.00E+06
1.00E+05 1.00E+05 1.00E+05
H = 3.92
number of cells
number of cells
number of cells
1.00E+04 1.00E+04 1.00E+04 E = 0.57
1.00E+03 1.00E+03 1.00E+03 (least
1.00E+02 H = 5.67 1.00E+02
H = 4.52 1.00E+02 diverse)
1.00E+01
E = 0.82 1.00E+01 1.00E+01
1.00E+00 1.00E+00 E = 0.66 1.00E+00
1.00E-01 1.00E-01 1.00E-01
1 200 399 598 797 996 1 200 399 598 797 996 1 200 399 598 797 996
sp. code sp. code sp. code
Loss of diversity in conventional agriculture
the world’s agricultural landscapes are
planted mostly with some 12 species of grain
crops, 23 vegetable crop species, and about
35 fruit and nut crop species
No more than 70 plant species spread over
approximately 1440 million ha of presently
cultivated land in the world
Genetically, modern agriculture is
shockingly dependent on a handful of
varieties for its major crops
For example, in the US, 60–70% of the total
bean area is planted with 2–3 bean varieties,
72% of the potato area with four varieties and
53% of the cotton area with three varieties
Researchers have repeatedly warned
about the extreme vulnerability associated
with this genetic uniformity
The relative scarcity of outbreaks of diseases on
these crops is a testament to plant breeding and
cultivation practices
A hybrid (center) between cultivated potato (left) and wild species (right)
However, it is unclear if such conventional
breeding approaches can work indefinitely
The degree of biodiversity in agroecosystems
depends on four main characteristics:
1. The diversity of vegetation within and
around the agroecosystem
2. The permanence of the various
crops within the agroecosystem
3. The intensity of management
4. The extent of the isolation of the
agroecosystem from natural vegetation
Agricultural biodiversity can be grouped as follows:
Productive biota: crops, trees and animals chosen
by farmers which play a determining role in the
diversity and complexity of the agroecosystem.
Resource biota: organisms that contribute
to productivity through pollination,
biological control, decomposition, etc.
Destructive biota: weeds, insect pests,
microbial pathogens, etc. which farmers aim
at reducing through cultural management
Conyza bonariensis
planned biodiversity:
is the biodiversity associated with the crops
and livestock purposely included in the
agro-ecosystem by the farmer
Agroforestry:
is an integrated approach of using the interactive
benefits from combining trees and shrubs with
crops and/or livestock.
It combines agricultural and forestry technologies
to create more diverse, productive, profitable,
healthy and sustainable land-use systems
Case study:
Forest Network Farmland in the Zhujiang River Delta
Climatic conditions the
annual mean temperature
is 21.5 - 22.0ºC with a
minimum monthly mean
temperature (January) of
12.4 - 13.7ºC and a
maximum monthly mean
temperature (July) of 28.1 -
28.8ºC. The annual
precipitation is 1,600 -
2,200 mm
140,000ha of farmland forest network
has been established in the delta
Benefits from the Forest Network
the wind velocity was reduced by 15 - 20%.
In the low temperature seasons, the air and
soil temperatures raised by 0.5 - 1.5ºC
Rubber tree (Hevea brasiliensis) and
Tea (Camellia sinensis) Interplanting (Guangdong(
Cold dew wind is harmful to the growth of late
rice in Southern China. Under the protection
of the forest network, the damage to rice can
be greatly reduced .
Preventing the Damage of Late Cold
Spring to rice seedlings
Resisting Typhoons
Green manure – cover crops
A non-profit crop designed to improve soil fertility
Winter cover crop is mowed in spring
Advantages of cover crops
- Addition of soil organic matter and
improving soil structure
- Addition of nitrogen fertilizer
- Aids pest control: fights soil born
diseases and attracts beneficial insects
- Helps prevent soil erosion
Crop rotations
Increases biodiversity, fertility and pest management
Intercropping
is the practice of growing two or more crops in proximity
Plants grow in the same area but niches and
resource partitioning is somewhat different
Together, both plants use available resources
more efficiently
Row intercropping
Growing two or more crops simultaneously
where one or more crops are planted in rows
Strip intercropping
Growing two or more crops simultaneously in
different strips wide enough to permit independent
cultivation but narrow enough for the crops to interact
agronomically. This form of intercropping is more
common in highly modernized systems, especially
where the intensive use of machinery is desired.
intercropping strategies are planting a deep-rooted
crop with a shallow-rooted crop, or planting a tall
crop with a shorter crop that requires partial shade.
Disadvantages of intercropping
Each of the many possible intercropping
patterns is appropriate for a particular range of
conditions and inappropriate for others
Intercropping systems make it difficult to
cultivate between rows
Potential competition between crops for
water, nutrients, light etc.
Advantages of intercropping
Dependence on only crop is avoided – protection
against environment and economical extremes
Reduction in the outlay for fertilizers
There is much greater flexibility of the distribution
of labour and availability of harvest over a much
longer period of time
Maintain soil fertility as the nutrient
uptake is made from both crops
associated biodiversity:
includes all soil flora and fauna, herbivores,
carnivores, decomposers, etc. that colonize the
agroecosystem from surrounding environments
and that will thrive in the agroecosystem
depending on its management and structure
Buffer strip
A buffer strip is an area of land maintained in
permanent vegetation that helps to control air,
soil, and water quality, dealing primarily on land
that is used in agriculture.
Buffer strips trap sediment, and enhance
filtration of nutrients and pesticides by
slowing down runoff that could enter the
local surface waters.
The root systems of the planted vegetation in
these buffers hold soil particles together which
alleviate the soil of wind erosion and stabilize
stream banks providing protection against
substantial erosion and landslides
Areas with diverse vegetation provide more
protection from nutrient and pesticide flow
and at the same time provide better
biodiversity amongst plants and animals
A riparian buffer is a vegetated area (a "buffer
strip") near a stream
Riparian strip
Field ditch
The effect of biodiversity on insect population
Maize hybrids in the United States now
have a useful lifetime of about 4 years, half
of what it was 30 years ago
low pest potentials may be expected in
agroecosystems that exhibit the following
characteristics:
High crop diversity through mixing
crops in time and space
Discontinuity of monocultures in
time through rotations
Farms with a dominant perennial crop
component like orchards
High genetic diversity resulting from the
use of variety mixtures or crop multilines
The effect of biodiversity on insect population
Diverse systems have a variety of host plants
that can support and feed a variety of insects
A diverse system is more stable and more
resistant to stress
A variety of insects reduces the abundance
of crop pathogens through competition and
predatory relations
The establishment of a varied insect
community can take time and is dependent
upon multiply environmental properties.
Therefore, close monitoring of crop pests is
always essential.
Since nearby fields have a great effect on
insect population, a regional agrosystem
plan is desirable
Biodiversity, soil fertility and plant health
The beneficial effects of biodeiversity on
microorganisms populations are similar to
insect population:
- System stability and resistance to stress
- reduces pathogen establishment through
competition and predatory relations
More diverse microbial
communities are more efficient
Soil microbial functional diversity
(Shannon index H') and metabolic
quotient (qCO2 = soil basal
respiration/soil microbial biomass)
correlate inversely. A higher
diversity in the organic plots is
related to a lower qCO2, indicating
greater energy efficiency of the more
diverse microbial community. The
Shannon index is significantly
different between both conventional
systems (CONFYM, CONMIN) and
the BIODYN system, the qCO2,
between CONMIN and BIODYN
(P < 0.05).
Enhancing microbial diversity and abundance
Regular input of organic matter
No or minimal tilling
Minimal use of pesticides and synthetic
fertilizers
Using compost teas and other extracts
Compost tea is a liquid
extract or a dissolved
solution but not simply a
suspension of compost. It is
made by steeping compost
in water for 3-7 days
Compost tea is a concentrated inoculum of
microorganisms. Preparation of compost tea
may include aeration and nutrient addition
Compost tea application is highly
recommended for conversion plots
Compost tea foliar
sprays may help control
crop diseases
Control of powdery mildew in grapevines
Treatment Leaf infection (%)
(late season)
82a
Control (no treatment)
8b
Horse compost extr (3 day extr)
6b
Wettable sulfur preperation
5b
Horse compost extr+wettable sulfur
Summary
