Restoration of invaded grasslands in a changing world: Impacts of - - PowerPoint PPT Presentation

Restoration of invaded grasslands in a changing world: Impacts of invasive plants and climate change on ecosystem functioning

Johannes Kollmann1, Florencia Yannelli1,2 & Leonardo Teixeira1,3

1Chair of Restoration Ecology, Technical University of Munich, Germany 2Centre for Invasion Biology, Stellenbosch University, South Africa 3Center for Biosciences, Federal University of Rio Grande do Norte, Brazil

SER Europe Summer School on Ecological Restoration, 20.–24.08.2018, Vacratot

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Why ecological restoration?

… because of climatic challenges for biodiversity and ecosystem functions

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Warming Drought

http://i.telegraph.co.uk

Hurricanes Salinisation

www.foodnavigator.com

… due to land-use changes affecting biodiversity and ecosystem functions

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Fragmentation Eutrophication Biological invasions Habitat losses Diseases Pollinator losses

… because of environmental sustainability on a cultivated planet

Foley et al. 2011, Nature

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… for securing natural resources and environmental sustainability

Foley et al. 2011, Nature

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Contributions of ecological restoration?

… for securing natural resources and environmental sustainability

Introduction

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Why grassland restoration?

… because of their biodiversity and ecosystem functions

Veldman et al. 2015, Science

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• Grasslands cover 40% of all terrestrial biomes
• Ecological value: species richness, erosion control,

groundwater production, carbon sequestration

• Economic value: livestock grazing, food production
• Subject to increasing land-use change (conversion

to arable land, afforestation, urbanisation)

… because of land-use changes resulting in grassland losses

Zerbe & Wiegleb 2009, Renaturierung von Ökosystemen

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1954 1992

11 km

Reduction of grassland area near Münster in NW Germany

• –44% area and +67% number of patches

… because of the dynamics of grassland degradation and restoration

Andrade … Kollmann et al. 2016, Brazilian Journal Nature Conservation

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… because of research opportunities of grassland restoration

Kollmann et al. 2016, Restoration Ecology

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Under-investigated in restoration studies:

• Invertebrates
• Microbes
• Carbon

sequestration

• Decomposition

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Why addressing invasive alien plants?

… because of threats of invasive species to the functioning of ecosystems

• Invasive alien species (IAS) are

the second most important threat to biodiversity

• IAS can change plant community

composition in the long term

Ehrenfeld 2003, Ecosystems; Batten et al. 2006, Biological Invasions; Ehrenfeld 2010, Annual Review of Ecology, Evolution, and Systematics; Vilà et al. 2011, Ecology Letters; Trentanovi et al. 2013, Diversity and Distributions

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Ailanthus altissima

Hulme 2013, New Phytologist

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… because enhanced invasions under climate change

• Neophytes respond faster and stronger to climate change

Native: Impatiens noli-tangere Alien: Impatiens parviflora

Example: Contrasting climate‐driven flowering phenology and spread of alien vs. native plants in Britain

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Example: Reclamation of new road sides – Suppression of invasive plants?

• Seed mixtures to suppress invasive alien plants

Solidago gigantea

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Background: Niche occupation, resources and competition with invasive plants

Scientific framework for grassland restoration and suppression of IAS

Kollmann et al. 2018, Restoration Ecology

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Ecosystem scale Community scale Population scale Legal and socio- economic framework Vacratot, 21 August 2018

Plant diversity and invasion resistance

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 The biotic resistance hypothesis predicts that an increase in the number of resident species enhances the use of resources and therefore reduces the establishment probability of invaders (D’Antonio & Chambers 2006)

Richardson 2011, Fifty years of invasion ecology: the legacy of Charles Elton

Charles Elton (1900–1991)

Plant diversity and invasion resistance

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 Diverse plant assemblages are more resistant to invasions due to a more exhaustive use of available resources (Elton 1958)  Diversity described as richness

• f either species numbers or

functional groups (Levine & D'Antonio 1999; Pokorny et al. 2005)

Richardson 2011, Fifty years of invasion ecology: the legacy of Charles Elton

Charles Elton (1900–1991)

Resource competition: a mechanism of invasion success

Funk & Vitousek 2007, Nature; Gonzáles-Moreno et al. 2014, Diversity and Distributions

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“Because no species can maximize growth, reproduction and competitive ability across all environments, the success of invasive species is habitat- or context-dependent.”

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Case study 1: Invasive species and plant functional diversity moderate soil fertility in experimental grasslands

Funk et al. 2008, Trends in Ecology and Evolution

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Theoretical background: Diversity-invasibility hypothesis

• Effects of functional diversity on grassland invasion?
• Investigates if functionally diverse communities can reduce IAS impacts on

native biomass, soil and soil water nutrients. Prediction: Higher functional diversity enhances biotic resistance of restored grasslands

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• Four levels of functional groups (0, 1, 2, 3)
• Two levels of Solidago gigantea (+, -)
• Five blocks and eight treatment

combinations (40 trays à 0.12 m2)

• 16 hours light period per day
• 21°C average temperature
• Five months
• Invasive species effects on native plant

biomass?

• Direct and indirect effects on nutrients in

soil and soil water?

Greenhouse experiment: design

Teixeira et al. 2018, submitted

Teixeira et al. 2018, submitted

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Results: Effects on native plant emergence and biomass

Teixeira et al. 2018, submitted

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Discussion: Effects on native plant emergence and biomass

• Functional diversity does not affect

native plants emergence but biomass production (in invaded communities).

• Invaded communities have greater total

biomass but less native plant biomass than uninvaded ones.

• S. gigantea reduced emergence and

biomass of native plants.

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Teixeira et al. 2018, submitted

Results: Effects on soil macronutrients

Solidago gigantea No Solidago gigantea

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Teixeira et al. 2018, submitted

Results: Effects on soil macronutrients

Solidago gigantea No Solidago gigantea

• Functional diversity directly controls only

two nutrient types in the soil (i.e. phosphate and ammonium)

• The presence of S. gigantea disrupts the

effects of functional diversity on soil nutrients

• It creates new effects on nutrients by

changing soil pH conditions via biomass

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Case study 2: Preventing plant invasions at early stages of revegetation – the role of limiting similarity, relatedness and highly competitive species

Reducing invasibility of native communities: Biotic resistance

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The ability of the native community to thwart the invasion success of arriving non-native species Reduced niche opportunities for invasive alien plant species

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Similar species have the same symbol Native species are represented as colored shapes, invasive species as white shapes

Theoretical background: Trait-based community assembly rules

Funk et al. 2008, Trends in Ecology and Evolution

Limiting similarity predicts that invasive species will be unlikely to establish, if there are native species with similar traits present in the resident community or if available niches are occupied.

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• Four levels of functional group indentity

(FG1, 2a, b, 3)

• Two levels of propagule pressure
• Tested with Solidago gigantea and

Ambrosia artemisiifolia

• 80 trays 0.12 m2, eight weeks
• Effects of native species functional trait

similarity on invasive species performance?

• Effects of native species phylogenetic

similarity on invasive species performance?

Greenhouse experiment: design

Yannelli et al. 2017, Oecologia

Native species 51 plant species present in mesic grasslands of Central Europe Invasive species

Methods: Clustering of species in functional groups and phylogeny

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Invasive alien plants Yannelli et al. 2017, Oecologia

Traits

• Longevity
• Life form
• Shoot morphology
• Root morphology
• Seed mass
• Canopy height
• SLA
• Dry leaf mass

Observations: Suppression of the two invasive alien species

FG1 + Amb art (HP) Control (HP) FG1 + Sol gig (HP) Control (HP)

Solidago gigantea Ambrosia artemisiifolia

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Yannelli et al. 2017, Oecologia

Results: Suppression of the two invasive alien species

Yannelli et al. 2017, Oecologia

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Native communities Phylogenetic distance

Solidago gigantea Solidago gigantea Ambrosia artemisiifolia Ambrosia artemisiifolia

High (black) and low (white) IAS propagule pressure (mean ± SE) Weighted mean distance of IAS to each native species (grey), and distance to the most abundant native species (black)

Results: Suppression of the two invasive alien species

Yannelli et al. 2017, Oecologia

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Native communities Phylogenetic distance

Solidago gigantea Solidago gigantea Ambrosia artemisiifolia Ambrosia artemisiifolia

• Species of the same

functional group do suppress less strongly

• Suppression decreases

with increasing phylogenetic distance

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Case study 3: Restoring grasslands in a changing world – effects of limiting similarity versus seed density

Laughlin et al. 2014, Ecology Letters

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Theoretical background: limiting similarity

Applying trait-based models for plant community design

Laughlin et al. 2014, Ecology Letters

Plant communities and design

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Ambrosia artemisiifolia

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Solidago gigantea

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Greenhouse experiment: design

Yannelli et al. 2017, Oecologia

• Two native communities (AA and SG type)
• Tested separately with Solidago gigantea

and Ambrosia artemisiifolia

• Monoculture of each invasive species
• Trays 0.12 m2 area, eight weeks, total of

36 trays

• Native species functional trait similarity

effect on invasive species performance? Native plants 32 grassland species present in vegetation of the Bavarian lowlands

Results: Effects on height of invasive alien plants

Yannelli et al. 2017, Oecologia

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a a b

2 4 6 8 Control AA SG

Treatment Invasive spps height (cm)

• A. artemisiifolia

a a b

0.0 0.5 1.0 1.5 2.0 Control AA SG

Treatment S.gigantea

• IAS plants were taller in communities designed to suppress S. gigantea (SG)

AA + Ambrosia artemisiifolia SG + Ambrosia artemisiifolia Solidago gigantea Ambrosia artemisiifolia

Results: Effects on plant community density

Yannelli et al. 2017, Oecologia

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a a b

2 4 6 Control AA SG

Treatment Leaf area index

• Density was higher in communities designed to suppress S. gigantea (SG).

Results: Suppressive effect of the SG mixture

Yannelli et al. 2017, Oecologia

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• Aboveground IAS biomass was lower in communities designed to suppress S. gigantea (SG).

Solidago gigantea Ambrosia artemisiifolia

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Case study 4: Restoring grasslands in a changing world – effects of competitive hierarchy, propagule pressure and extreme weather events

Laughlin et al. 2014, Ecology Letters

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Theoretical background: Competitive hierarchies

Grime 1998, Journal of Ecology; Byun et al. 2015, Oecologia

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• Dominance effects – biomass ratio

hypothesis

• Interactions between abiotic

constraints, propagule pressure and biotic resistance

Theoretical framework: Dominance–biomass hypothesis

Teixeira et al., unpubl. results

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Methods: Native study plant species

• Classified according to their dominance

hierarchy in natural sites (Ellenberg indicator values)

• Important traits for dominance hierarchy:

seed mass, SLA, dry leaf area and canopy height

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• Two levels of relative abundance (A, B)
• Two levels of propagule size (1, 3 g m-²)
• Two levels of propagule number (1, 3 times)
• Two levels of invasion (+, -)
• Extreme weather events (biweekly flooding

and heating during 72 hours; five months)

Three replicates and eight treatment combinations (trays 0.12 m2)

• Plant emergence and vegetation cover
• Native and invasive plant biomass
• Soil and soil water nutrients
• Soil respiration (microbial metabolism)

Methods: Factorial experimental design

Using four climate chambers at TUMmesa we simulated climate change scenarios:

Teixeira et al., unpubl. results

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• Higher emergence of native

plants in communities with fewer A. elatius, due to a higher number of (smaller) seeds

• Native plant emergence in

the same communities negatively affected by S. gigantea

Results: Suppression of natives by high seed densities and IAS

Teixeira et al., unpubl. results

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• When manipulating

propagule pressure of invasive plants, patterns are repeated, i.e. higher emergence with fewer A. elatius

• No clear effects of invasive

plant propagule pressure

• n emergence of native

plants

Results: Suppression of natives by high seed densities and IAS

Teixeira et al., unpubl. results

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• Emergence of S. gigantea

not affected by competitive hierarchies of native plants

• Propagule size is the main

factor controlling invasive plant emergence

Results: Suppression of IAS by high seed densities

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Conclusions for ecological restoration

Highlights of the results

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 Invasive plants interfere with community biomass, thus impacting nutrient stocks and reducing native species.  Altered nutrient conditions create a positive feedback for further invasions.  Functional diversity does not consistently reduce the impact of invasive alien species  Species of the same functional group are not more suppressive, while there are phylogenetic effects.  Emergence of invasive alien species independent of competitive hierarchies of native plants.  High seed densities suppress native and invasive alien species.

Food for thoughts

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 Biotic resistance of a community can be strongly influenced by

• ccurrence of highly competitive species.

 The functional trait selection has to consider traits correlated to all important plant responses and development stages.  To be discussed whether we have the right traits available in current trait databases.  Phylogenetic relatedness can be a helpful proxy when traits are difficult to measure.

Perspectives for future research and applications: Don‘t give up!

Foley et al. 2011, Nature

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• Test new species (combinations) based on functional similarity and

phylogenetic relatedness

• Verify results in field experiments
• Develop commercial seed mixtures
• Device improved sowing and managing recommendations

Contributions of ecological restoration!

Acknowledgements

Questions ?

References 1

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