1. Girma Shumi, Jannik Schultner, Ine Dorresteijn, Patricia Rodrigues, Jan Hanspach, Kristoffer Hylander, Feyera Senbeta and Joern Fischer
Land use legacy effects on woody vegetation in agricultural
landscapes of southwestern Ethiopia
www.leuphana.de 19/17/2017
54th Annual Meeting of the
Association of Tropical Biology and
Conservation, MERIDA, YUCATAN,
MEXICO, July 9-14, 2017
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Introduction
Extinction debt – current community
contains species whose populations
cannot be sustained;
Immigration credit – environment is
suitable for certain species, current
community does not contain them as
they have not yet colonized it
Two contrasting land use legacy effects
Accounting for legacy effects and designing appropriate conservation strategies thus,
• Need to understand how current species richness and composition patterns relate to
present and historical land use
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1. Present-day land use variables influence woody plant species composition,
distribution and richness
2. Legacy effects of historical land use influence species composition, distribution and
richness, particularly forest specialists surviving as relicts in farmland
3. Legacy effects could be detectable from population structure – large diameter trees
might disappear in old farmland but persist in converted farmland
Hypotheses of the study
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Studyareaand methods
• Sampling
72 (53 in arable & 19 grazing) 1 ha
circular study sites
o Recorded all woody plant species-
height ≥ 1.5m;
o Measured diameter at breast height
(DBH) of all plants DBH ≥ 5 cm
Grouped them into forest specialist,
generalist, pioneer & planted species
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• Historical distances – study sites to nearest
≥ 1 ha historical forest edge
• Current distances – study sites to nearest
≥ 1 ha current forest edge
• Environmental variables
Site-level forest cover; terrain wetness
index; and altitude
Studyareaand methods
• Permanent farmland sites
• Recently converted farmland sites
8. • Data analysis
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Studyareaand methods
Non-metric multidimensional scaling (NMDS)
Generalized linear mixed effects models (GLMMs)
DBH size class distribution
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Results and discussion
• Species composition and distribution
128 species, 48 families
Forest specialist occupied distinct locations
Historical distance was positively correlated with generalist & pioneer species
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Results and discussion
• Species richness models
Planted species richness – lowest far away from forest edge in current farm lands
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Results and discussion
• DBH size class distribution
Few old trees of forest specialist species
Generalist and pioneer species showed
nearly normal distribution
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Results and discussion
Overall
• Hypothesis 1
• Only planted species richness negatively related with current distance; and
generalist species richness was affected by farmland type
Fewer relationship between current land use and current species richness
• Hypothesis 2
• Significant relationships between historical distance and total species, generalist,
pioneer, and planted species richness but not forest specialist species richness
The dominant legacy effect identified was immigration credit, rather than
extinction debt
• Hypothesis 3
• Only recently converted farmland showed limited evidence of large relict of
forest trees, while trees of other groups was close to natural populations in both
converted and permanent farmland sites
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Conservationimplications
Possible extinction debt for forest specialist species in farmland was rapidly paid off -
farmers cleared remnant trees
Evidence of immigration credit in farmland for total, generalist, pioneer and planted
species richness and composition
o Nurse tree effects in increasingly old farmland development of novel ecosystems
and sustainable cultural landscapes
o Long-established farmland unrecognised conservation value
o Forest conservation should remain the highest priority
Biodiversity conservation policies should also recognize the agricultural mosaic
A future priority could also be to reintroduce forest specialists into the farmland mosaic
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Thankyou for your attention
ERC- project to Joern Fischer
Farmers, field workers and local community for their cooperation
Oromia regional state and government of Ethiopia for permission
Acknowledgement
Questions and comments are welcome!