A presentation by Dr. Fredrick Ouma Ayuke : Soil Macrofauna functional groups and their effects on soil structure, as relatwed to agricultural management practices accross agro-ecological zones of Sub Saharan Africa

1. 5/27/2010
Soil macrofauna as ecosystems engineers
Soil macrofauna Biodiversity, Soil structure and Organic
Resource Management in East and West African Earthworms and termites are important
cropping systems ecosystem engineers (Jones et al. 1994).
Their role in sustainable crop
Fredrick Ayukea*, b, Mirjam Pullemana, Lijbert Brussaarda, Johan Sixc, Bernard production includes:
Vanlauweb
Improve soil structure & water
retention
Earthworms
Lavelle et al. 1998
Microbial
Soil water
content
OM
degradation Incorporate organic material into soil
activities
Improved Improve soil fertility through organic
matter decomposition and nutrient
Water
Infiltration
rate
release
*a Department of Soil Quality, Wageningen University, P.O Box 47, NL-6700 AA Wageningen, The Netherlands Nutrient
uptake
Clay transfer &
b Tropical Soil Biology and Fertility (TSBF) Institute of CIAT, P.O Box 30677-00100, Nairobi, Kenya transformation
N
c Department of Plant Sciences, University of California, Davis, CA 95616, USA Termites (Courtesy of Soulemayne Konate)
Objectives & Hypotheses Objectives continued:
This study aimed at: 1. Assessing effects of climate and agricultural
management on earthworm and termite biodiversity across SSA 2. Explore relations between soil macrofauna (earthworms
and termites), soil aggregation and SOM dynamics in
Hypotheses differently managed agro-ecosystems”
Biodiversity of earthworms and termites will: Specifically:
a) the extent to which soil macrofauna explains
1. Decrease with increasing temperature and decreasing differences in aggregation across a wide range of climatic
precipitation and soil conditions in SSA, and
b) compare these relationships between arable and
2. Be lower in agricultural than in fallow systems fallow systems representing different levels of
management intensity.
3. Be higher under long-term agricultural management that had led
to high-C soils than where it had led to low-C soils
Materials & Methods Sub-humid AEZ Semi-arid AEZ
Study sites
Long-term trials across the
sub-humid to semi-arid
agroecological zones of East & Fallow
West Africa
Shrubland Bush Shrubland
The trials differed in management
of:
Organic resources
Mineral N High-C
Rotation T. candida-maize S. siamea+NPK Millet-cowpea
Tillage
Low-C
Maize, no input Maize, no input Millet, no input
KENYA NIGERIA NIGER
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2. 5/27/2010
Results Earthworms
Soil macrofauna biodiversity
Millsonia inermis, Saria, Burkina Faso
20 earthworm taxa in 3 families:
Ocnerodrilidae (4 taxa)
Acanthodrilidae (8 taxa)
Eudrilidae (8 taxa)
Earthworm and termite taxonomic richness and functional groups
Termites based on monolith and transect methods
Earthworm taxa Termite taxa
Functional Functional Food
Taxonomic group Taxonomic group
group a group b type c
Ocnerodrilidae Rhinotermitidae-Rhinotermitinae
Nematogenia lacuum Endogeic Captotermes intermedias I WLG
Gordiodrilus robustus Endogeic Schedorhinotermes lamanianus I WLG
Gordiodrilus wemanus Endogeic Rhinotermitidae-Psammotermitinae
Gordiodrilus marcusi Endogeic Psammotermes hybostoma I WLG
Acanthodrilidae Termitidae-Nasutitermitinae
Millsonia inermis Endogeic Nasutitermes spec II WLG
Endogeic Trinevitermes spec II LG
20 termite taxa in two families:
Millsonia guttata
Dichogaster (Dt.) saliens Epigeic Termitidae-Macrotermitinae
Dichogaster (Dt.) affinis Epigeic Ancistrotermes cavithorax II WLG
Epigeic II FWLG
Termitidae (17 taxa)
Dichogaster (Dt.) bolaui Macrotermes nr. Vitrialatus
Dichogaster (Dt.) modiglianii
Di h t (Dt ) di li ii Epigeic
E i i Macrotermes subhyalinus
M t bh li II FWLG
Dichogaster (Dt.) spec nov 1 Epigeic Macrotermes herus II FWLG
Dichogaster (Dt.) spec nov 2 Epigeic Microtermes pusillas II FWLG
Rhinotermitidae (3 taxa) Eudrilidae
Polytoreutus annulatus Epigeic
Macrotermes spp.
Microtermes spp.
II
II
FWLG
FWLG
Hyperiodrilus africanus Epigeic Odontotermes magdalenae II FWLG
Hyperiodrilus spec nov Epigeic Odontotermes spp. II FWLG
Eudrilus buettneri Epigeic Pseudacanthotermes spiniger II FLG
Ephyriodrilus afroccidentalis Epigeic Pseudacanthotermes spp II FLSD
Eminoscolex violaceus Epigeic Termitidae-Termitinae
Stuhlamannia spec nov Epigeic Amitermes-Amitermes stephensoni II WLSD
M. bellicosus, Tamale (Ghana) Lavellea spec nov Epigeic Microcerotermes parvulus II WLG
Termes-Termes baculi III WS
Cubitermes- Tubeculitermes spec IV S
a
Based on classification by Swift & Bignell (2001). (W=wood; L=leaf litter; S=soil; D=Dung/manure; F=fungus
grower; G=dead/dry grass. bBased on classification by Eggleton et al. (2002). c based on field notes/observation.
c
based on observations by Kooyman & Onck (1987).
RDA biplot on earthworm species abundance and environmental variables RDA biplot on termite species abundance and environmental variables
Axis 1: temperature/altitudinal gradient
Axis 1: precipitation/latitudinal gradient
Axis 2: Soil C/latitudinal gradient
Axis 2: temperature/texture/ longitudinal gradient.
Axes partition sites that are cooler and are at high altitudes from lower relatively hotter altitudes
More taxa occur on warmer/drier sides
Earthworm taxa are less abundant on the higher, cooler altitudes characteristic of East African sites
Axes mainly separate East & West Africa.
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3. 5/27/2010
Shannon diversity indices across fallow and arable systems
Treatment
Arable system
Soil Macrofauna and ecosystem functioning
Fallow High-C Low-C P-value
Earthworm diversity 0.13a 0.07b 0.02c <0.001
(H′)
Termite diversity (H′) 0.08a 0.06a 0.03b 0.008
Factor analysis and factor pattern after varimax rotation
Possible attributes: factor & multiple regression analysis
Treatment
Fallow Arable system
Fallow system
Factor I Factor II Factor I Factor II
(n=36) Arable system (n=72) Termite
Variable Factor I Factor II Factor I Factor II SOM, (abundance &
Termite Shannon index −0.1 0.5 −0.1 0.2 Texture, biomass),
Earthworm Shannon index 0.5 −0.4 −0.1 0.7 Climate, Termite Earthworm
Termite abundance 0.2 0.6 0.2 0.7 Earthworm (Shannon (Shannon
(Shannon diversity, diversity,
Earthworm abundance 0.6 −0.3 0.0 0.7 Possible diversity & abundance & SOM, Texture, abundance and
Termite biomass 0.3 0.7 0.3 0.6 attributes abundance) biomass) Climate biomass)
Earthworm biomass −0.1 −0. 8 −0.2 0.6
Average t
A temperature
t −0.9
09 02
−0.2 −0.9
09 01
−0.1
Precipitation 0.7 0.1 0.7 0.0 Multiple regression analysis with aggregate fractions and factors with loading coefficients >0.05
Total organic C 1.0 0.1 1.0 0.0 (%variance accounted for by factors)
Total
Total organic N 1.0 0.1 1.0 0.0 macroaggregates
Clay 0.9 0.3 0.9 −0.1 (sand corrected) 88.5 4.1 90.4 7.6
Sand −0.9 −0.1 −0.9 0.1 Microaggregates
within
Factor eigenvalues 5.6 2.0 5.1 2.4 macroaggregates
(mM) 82.6 4.9 91.3 8.7
Explained variance (%) 45.9 17.8 42.6 20.0
Conclusions Conclusions continued:
Macrofauna, especially earthworms, and to a lesser extent
Differences in climate coincide with differences in soil
types and geographical region. These factors are termites, are important drivers of stable soil aggregation, in
associated with earthworm and termite diversity conjunction with climate, soil organic C content and soil
texture in Sub-Saharan agroecosystems
Agriculture has negative effects on earthworm and
termite diversity as compared to long-term fallow The beneficial impact of earthworms and termites on soil
aggregation is reduced with increasing management intensity
Under continuous crop production, agricultural (e.g. soil disturbance due to cultivation)
management that resulted in low-C soils had lower
earthworm and termite diversity than agricultural
management that had resulted in high-C soils Our results are important for designing agricultural
management systems aimed at increasing long-term soil
fertility in Sub-Saharan Africa.
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4. 5/27/2010
Recommendations from this study: General recommendations:
The agroecological conditions studied, i.e: As mineral and organic fertilizers are often limited in quantity and quality,
soil fertility research has to focus on developing integrated management
Long-term application of manure in combination with fertilizer strategies to address soil fertility decline (Integrated Soil Fertility
Conservational tillage plus maize stover residue application; Management (ISFM) and Conservation Agriculture (CA))
Hand-hoeing plus manure
affect faunal activities in different ways. Hence: As the soil biota are responsible for the key ecosystem functions of
decomposition and nutrient cycling, soil organic matter synthesis and
recommendation of these practices should be tailored to mineralization, soil structural modification, aggregate stabilization, ISFM
f S
meet the circumstances of target farmers & CA have to maximize beneficial soil biota.
Although there is pressure on land in many parts of Sub-Saharan Africa
fallowing (or similar practices) has to be an integral part of land
management in view of the conservation of biodiversity for enhanced
ecosystem functioning
Acknowledgements
WOTRO/NWO through Wageningen University for awarding the
Scholarship and Research funds and Norman E. Borlaug LEAP
through UC-Davis and the International Atomic Energy Agency
(IAEA) for co-funding the research
Collaborating Institutions
TSBF-CIAT, KEFRI, Kenyatta University (Nairobi, Kenya)
INERA,
INERA IFDC (Burkina Faso)
Others: IITA-Nigeria, SARI-Ghana, ICRISAT-Niger, KARI-Kenya,
CHITEDZE Agricultural Inst.
It was a teamwork
for cooperating during periods of data collection
Special thanks to all my promoters and in particular Prof. Lijbert
Brussaard for sending me off on the long journey.
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