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					               Visit to Chitwan, Nepal
                February 24-27, 2010
    Protocol to detect and
assess pollination deficit in
  crops in Nepalese sites
 Bernard E. Vaissière (INRA, Avignon, France)
Breno M. Freitas (U. de Ceará, Fortaleza, Brazil)
  Barbara Gemmill-Herren (FAO, Rome, Italy)
                                                    1
           Background : How to detect and
          assess pollination deficit in crops ?

       2008 : Literature review
January - March =>
  - Database: 67 publications that dealt with pollination
     deficit in crops
  - Preliminary draft of the review


=> Expert workshop in Avignon on April 3-6, 2008
                                                            2
                        Pollination deficit :
                       definition and concept
=> Pollination deficit
Based on Wilcock & Neiland (2002) who defined the concept of
pollination failure

Pollination deficit refers to quantitative or qualitative deficit
of pollination which decreases the sexual reproductive
output of plants

Other terminology
   • Pollination limitation (used by Ashman et al. 2004, Knight et
al. 2005) => refers to the absence of pollen deposition
    • Pollen limitation => refers to an inappropriate or insufficient
    deposition of pollen on the stigma
                                                                        3
             Working definition of pollination
                     deficit in crops
  Crop pollination deficit refers to inadequate
   pollen receipt that limits agricultural output

Inadequate pollen receipt
• Quantitative
• Qualitative (self-incompatible species)
• Timing (effective pollination period / stigmatic receptivity)

                              Limitation of agricultural output
                              • Quantitative or qualitative
                              • Productivity
                              • Sustainability
                                                                  4
      Pollination deficit definition and
                  concepts

                      Optimum
                       level
            Current         Pollination
             level
                              deficit



=> How to define and reach the optimum?



                                           5
         Methods to reach better or optimal
               pollination in crops

Optimum pollination => Maximum output given
the current available resources and taking into
account the production objectives
 • Yield / yield components [fruit set & seed set]
 • Fruit quality (size ; aspect)
 • Seed quality (seed germination rate; oil content)
 • Earliness and uniformity of output
 • Market value / profitability
 • Environmental & societal impacts
                                                       6
                Causes of pollination deficit
1. Pollen production & viability
2. Transport and deposition:
Quantitative pollination: # of visits received / flower
   => Lack of visits (population effect)
  (yield of Coffea arabica increased with the introduction of
   Africanized honeybees in Central America ; Roubik 2002)
Qualitative pollination: quality, distribution, origin of pollen
- Lack of wild bees with high pollination effectiveness
- Lack of wild bees for pPositive interaction with honey bees
- Low pollinator biodiversity => lower and less stable
   pollination
                                                                   7
       Methods to reach better or optimal
             pollination in crops


        Improved pollination
                    ≈
    Improved pollen transport,
     deposition & fertilization
effectiveness (viability, compatibility)
                                            8
         Consensus methods to reach better or
              optimal crop pollination
   1. Supplementation with honey bee colonies
       (apple, buckwheat, cucurbits, mustard)

Treatment :
Introduce colonies of honey bees (Apis cerana and/or
Apis mellifera) in or nearby the treated study fields at the
onset of effective flowering (e.g. flowering of production
trees in apple orchards) to increase density of honey bees
on flowers of study fields while the control fields will not
be provided with additional honey bee colonies
                                                               9
               Supplementation with honey bees - 2


    More realistic than hand pollination for most species
+   Applicable in farmer production management
    Easy practice in many circumstances, even around houses
    for subsistence crops

    • Pollination depends upon pollinator species introduced;
    • Limited to managed pollinators (Apis cerana or A. mellifera);
    • Unclear relationship between introduced bees and forager
       density;
–   • Effect of pollinator addition is probably not additive in
       relation to existing pollinator population;
    • Possible negative effects of high pollinator densities
     (e.g. bumble bees)
                                                                      10
             Supplementation with honey bees – 3
                        Experimental design
1. In homogeneous geographical area (≈ similar altitude and distance
to semi-natural habitat), select ten fields : 5 fields with and 5 fields
without colonies added (completely randomized design)

or
2. Use the geographical area (for example the altitude) as blocking
factor and select five pairs of fields, each subset of pairs in an
homogeneous area, with one field with and one field without colonies
added (randomized complete block design)

or
3. In large fields > 450 m long away from one side where
colonies can be introduced, select five such fields and test for a
gradient of pollinator density from near to far from side with colonies
(pollinator front) by recording data at 20, 220 and 420 m away from
                                                                           11
colonies                                                                   11
              Supplementation with honey bees – 4
                         Special requirements
• Record pollinator density & diversity just prior to colony
introduction to know baseline situation, that is the abundance and
diversity of the local pollinator population at onset of flowering;
• Colonies should be introduced at night or late evening or very
early morning so as to keep all their foraging force for their new
location;
• The stocking rate (number of introduced colonies per ha of target
crop) should be based upon existing practices, but also take
into account the area of flowering target crop without colony
provided in the surroundings (as a rule of thumb, the smaller the
study field, the higher the stocking rate should be and it is best not to go
below the introduction of 2 colonies along any study field to compensate for
the possible death of one colony following its introduction)
• Minimum distance between adjacent fields should be ≥ flight
distance of most pollinator species (≈ ≥ 2 km for honey bees);                 11
                                                                               12
             Consensus methods to reach better or
                  optimal crop pollination
  2. Proximity to semi-natural habitats (large cardamom)
 Treatment :
 Use the landscape context, in particular the proximity of
 the treated fields to large patches (> 0.5 ha) of semi-
 natural habitats to increase pollinator abundance &
 biodiversity in the flowers of the study fields while
 control fields will be selected away from semi-natural
 habitats (≥ 500 m)
Semi-natural habitat ≈ CORINE level 1 : forest, natural grassland, brush,…
                                                                        13
               Proximity to semi-natural habitats - 2

    • Realistic variations of pollinator abundance & diversity
    • Contrasting situations can be achieved
+
    • Takes into account all the pollinator fauna, including
     species not commercially raised


    • Potential correlated factors that affect yield components can
       confound results (e.g. fields along forest on steep slope may
       have inferior soil & overall agronomic conditions than faraway
–      fields in the valley)
    • Requires landscape heterogeneity
    • Large changes in pollinator community possible from year
      to year                                                           14
               Proximity to semi-natural habitats - 3
                        Experimental design
1. In homogeneous geographical area (≈ similar altitude and distance
to semi-natural habitat), select ten fields : 5 fields adjacent to and 5
fields away from semi-natural habitats (completely randomized design)
or
2. In mountainous areas, use the geographical area (e.g. the altitude)
as blocking factor and select five pairs of fields overall, with each
subset of pairs in an homogeneous area, and each field from a pair
adjacent to and the other set afar from semi-natural habitats
(randomized complete block design)

or
3. In large fields > 450 m long away from side close to semi-
natural habitats are available, select five such fields and test for a
gradient of pollinator density and diversity by recording data at 20, 220
and 420 m away from side with semi-natural habitats (pollinator front)
                                                                           15
               Proximity to semi-natural habitats - 4
                       Special requirements

• Area of semi-natural habitat adjacent to field should be as large as
possible so as to provide as diverse and abundant a pollinator fauna
as possible. For small bees, area ≥ 0.5 ha; for large bees => larger
fragment;

• Record distance to and type of closest semi-natural habitats
for all fields;

• If at all possible with GIS data available, determine proportion of
semi -natural habitats around each study fields within a 1 km
radius;

• Minimum distance between adjacent fields should be ≥ flight
distance of most pollinator species (≈ ≥ 2 km for honey bees);
                                                                         16
      Fixed-effect factors or independent
              variable (distance)

• Presence or absence of nearby honey bee
   colonies;
or
• Close or far from semi-natural habitats;
or
• When gradient is possible, distance to
   pollinator front (introduced colonies or
   closest semi-natural habitat)
                                              17
         Possible blocking factors for
        experimental design with paired
                     fields
• Altitude (valley versus hill top ; e.g., mustard);
• Distance to forest front (blocking factor if
   treatment is introduction of honey bee
   colonies ; e.g., apples);
• Variety and planting pattern (e.g., apples with
   production and pollenizer varieties);

• Village (e.g., possibly cucurbits)

                                                       18
     Dependent variables to be recorded

Forager density (forager/floral unit)
 • Pollinators/100 floral units (instantaneous
   counts)


Forager diversity (species richness)
 • Pollinator catch on transects (with sweep
   nets)

 Pollinator activity should be recorded under good weather
conditions for foraging : T ≥ 12°C, vegetation dry, light wind

                                                                 19
     Possible co-variables to be recorded

• Flower density at each recording of pollinator
   activity ;


• Temperature & relative humidity at each
   recording of pollinator activity ;


• Schedule of pesticide applications in relation
   to flowering;


                                                   20
If size of study field permits (≥ 0.3 ha) => set experimental
     site of 50 m x 25 m aligned along rows if present

                               25 m                   row of crop


                                             10 m
                                            minimum




               70 m 50 m
             minimum




                                       10 m
                                      minimum
                           45 m minimum
                                                                    21
                   Layout to measure pollinator abundance &
                    diversity when experimental site present
                                   [optional recordings in brackets]
                   25 m
                    3                   50
                                             i   Instantaneous count of potential pollinators
                              4                   (100 floral units scanned for pollinators in plot n° i)


   2                               4         j   Net captures : Subunit n° j of a fixed transect
                                        34       consisting of six 25-m long subunits for insects capture
               3                                 over a 2-m width for 5 min in each sub-unit

50 m

                          2
                                        17       [Plot to record the number of open flowers [in
                                                 1 m2 quadrant (buckwheat, mustard)]
   1                               5

           1

                                        0
                    6

       0   5   10       15    20   25


                                                                                                            22
    For smaller fields or fields with special shapes, the
          experimental site is the whole field
                        [optional recordings in brackets]
            3
                2              i   Instantaneous count of potential pollinators
    3                               (100 floral units scanned for pollinators in plot n° i;
                                   these flowers can be recorded on the side of the field
                                   to avoid trempling ofthe crop
4                       2
                                   Net captures : Subunit n° j of a fixed transect
                               j   consisting of six 25-m long subunits for insects capture
                                   over a 2-m width for 5 min in each sub-unit. If the
                                   perimeter of the field is < 150 m, it is OK to go back onto
                                   an area already sampled.


5                                  [Plot to record the number of open flowers [in
                        1
                                   1 m2 quadrant (buckwheat, mustard)]. These
                                   quadrats are set at a fixe spot nearby the start of a
                    1              subunit to record pollinator diversity
        4

            6




                                                                                                 23
For very large study fields, the experimental site
is set half way between the center and the border




                        d

                             d




                                                     24
           Experimental design

The management of all experimental
 units is assumed to be as similar as
  possible except for the pollinator
              treatment

             Same variety !


                                        25
           Dependent end variables
Assessing agronomic & economic yield
• Plants can compensate for pollen limitation with longer
  flowering periods, more flowers, etc...
• Fruit set and/or seed set can be ressource-limited

     (Knight TM et al. 2005. Pollen limitation of plant reproduction:
   pattern and processes. Annu. Rev. Ecol. Evol. Syst. 36 :467-497)




 Pollination treatments done on a plant-wide basis,
   that is with the whole plant as experimental unit
                                                                        26
                      Dependent variables

    Yield (agronomic terms : unit weight/unit area)
     • Straightforward (per plant or per plot)
     • Linked to commercial yield
+    • Meaningful variable for farmers & consumers
     • Dependent of agronomic situation

    • Long lag time until result
    • Between field variability can confound the link to pollination
        deficit (water availability; fertilizer; pest control)
–   • Data access may be difficult (harvesting before the farmer)
    • Undeterminate crops may require repeated harvesting over
        the season
                                                                   27
                      Dependent variables

Yield (monetary terms : market value)
    • Very context specific
    • May be very volatile
–   • Lack of accepted methodology (interdisciplinary)
    • Link to pollination deficit may be tenuous & difficilut to
        establish
    • May be beyond the control of individual farmers


    • Meaningful variable for farmers & consumers
    • Meaningful for government & policy makers
+   • May assist farmers with proper documentation
    • Can include other currency of value for society (e.g.,
       nutritional value)                                          28
                           Experimental units

    Individual plant or tree (e.g., apple, mustard in
    mixed plantings, cucurbits)

       • Yield unit
+      • Biological unit


       • Considerable work if using hand pollination or if
         dependent variable is fruit/seed set with many flowers
–
       • Does not control for ressource allocation between
         years except if recorded over several years

                                                                  29
                      Experimental units

    Plot / field (e.g., buckwheat, cucurbit)

     • When individual plant not possible (buckwheat, rape)
+    • Yield unit => talk to farmer
     • can be related to economic unit


     • Does not control for ressource allocation between years
–      except if recorded over several years
     (• Confound other inputs)


                                                                 30
                   Layout of the yield plots when experimental
                                   site present
                     25 m

           4
                                        50
                                                 Yield plot (length of row – usually 2 m – or
                                                 area of 1 m2 – as for buckwheat – or harvest
                                                 individually 5 adjacent plants – as in mixed
                                        34       planting of mustard – or 2 trees adjacent and
                         3
                                                 far away from pollenizer tree – as in apple)
50 m


                     2                       i
                                        17       Instantaneous count of potential pollinators




                                                 Plot to record the number of open flowers
                               1
                                        0


       0       5    10   15   20   25


                                                                                                 31
           Layout of the yield plots in smaller fields or
         fields with special shape where the experimental
                       site is the whole field
                                        L



                                               Yield plot (length of row – usually 2 m – or
                                        4L/5
                                4
                                               area of 1 m2 – as for buckwheat – or harvest

                                        3L/5
                                               individually 5 adjacent plants – as in mixed
                     3
Length                                         planting of mustard)
  L                        2
                                        2L/5

                                               Instantaneous count of potential pollinators
               1
                                        L/5



                                        0
                                               Plot to record the number of open flowers


     0   l/5       2l/5 3l/5 4l/5   l
                    width l

                                                                                              32
         Summary of protocol to detect &
         assess pollination deficit in crops
Method to expect better pollination
• Supplement local pollinator population with honey
    bees
• Proximity to semi-natural habitats

Variables to record
 • Pollinator density (forager/floral unit at the right
   time)
 • Pollinator diversity (even in coarse categories)
Experimental unit
• field or plot or plant
Final dependent variables
• Agronomic yield & monetary yield
                                                          33

				
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