Restoration of invaded grasslands in a changing …restorationcourse.okologia.mta.hu/sites/restorationcourse...Restoration of invaded grasslands in a changing world: Impacts of invasive

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

2

Why ecological restoration?

… because of climatic challenges for biodiversity and ecosystem functions

3

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Salinisation

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

4

FragmentationEutrophication

Biological invasions

Habitat lossesDiseases

Pollinator losses

… because of environmental sustainability on a cultivated planet

Foley et al. 2011, Nature 5

… for securing natural resources and environmental sustainability


Contributions of ecological restoration?

… for securing natural resources and environmental sustainability

Introduction 7

8

Why grassland restoration?

… because of their biodiversity and ecosystem functions

Veldman et al. 2015, Science 9

• 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 (conversionto arable land, afforestation, urbanisation)

… because of land-use changes resulting in grassland losses

Zerbe & Wiegleb 2009, Renaturierung von Ökosystemen 10

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 11

… because of research opportunities of grassland restoration

Kollmann et al. 2016, Restoration Ecology 12

Under-investigated in restoration studies:

Invertebrates

Microbes

Carbon sequestration

Decomposition

13

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 14

Ailanthus altissima

Hulme 2013, New Phytologist 15

… 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

16

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

Seed mixtures to suppress invasive alien plants

Solidago gigantea

17

Background: Niche occupation, resources and competition with invasive plants

Scientific framework for grassland restoration and suppression of IAS

Kollmann et al. 2018, Restoration Ecology 18

School of Life Sciences Weihenstephan

Ecosystem scale

Community scale

Population scale

Legal and socio-

economic framework

Vacratot, 21 August 2018

Plant diversity and invasion resistance

19

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

20

Diverse plant assemblages are more resistant to invasions due to a more exhaustive use of available resources (Elton 1958)

Diversity described as richness of 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 21

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

22

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

Funk et al. 2008, Trends in Ecology and Evolution 23

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

24

• 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 25

Results: Effects on native plant emergence and biomass

Teixeira et al. 2018, submitted 26

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.

27Teixeira et al. 2018, submitted

Results: Effects on soil macronutrients

Solidago giganteaNo Solidago gigantea

28Teixeira et al. 2018, submitted

Results: Effects on soil macronutrients

Solidago giganteaNo 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

29

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

30

The ability of the native community to thwart the

invasion success of arriving non-native species

Reduced niche opportunities for invasive alien plant species

31

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.

32

• 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?


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

33

Invasive alien plants


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

34Yannelli et al. 2017, Oecologia

Results: Suppression of the two invasive alien species

Yannelli et al. 2017, Oecologia 35

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


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

37

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

Laughlin et al. 2014, Ecology Letters 38

Theoretical background: limiting similarity

Applying trait-based models for plant community design

Laughlin et al. 2014, Ecology Letters

Plant communities and design

40

Ambrosia artemisiifolia

40

Solidago gigantea

41



• 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


aa

b

0

2

4

6

8

Control AA SG

Treatment

Inva

siv

e s

pp

s h

eig

ht (c

m)

A. artemisiifolia

aa

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 giganteaAmbrosia artemisiifolia

Results: Effects on plant community density


aa

b

0

2

4

6

Control AA SG

Treatment

Le

af a

rea

in

de

x

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

Results: Suppressive effect of the SG mixture


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

Solidago giganteaAmbrosia artemisiifolia

45

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 46

Theoretical background: Competitive hierarchies

Grime 1998, Journal of Ecology; Byun et al. 2015, Oecologia 47

Dominance effects – biomass ratio hypothesis

Interactions between abiotic constraints, propagule pressureand biotic resistance

Theoretical framework: Dominance–biomass hypothesis

Teixeira et al., unpubl. results 48

Methods: Native study plant species

• Classified according to their dominance hierarchy in natural sites (Ellenbergindicator values)

• Important traits for dominance hierarchy: seed mass, SLA, dry leaf area and canopy height

49

• 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)

o Plant emergence and vegetation cover

o Native and invasive plant biomass

o Soil and soil water nutrients

o Soil respiration (microbial metabolism)

Methods: Factorial experimental design

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


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


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 on emergence of native plants

Results: Suppression of natives by high seed densities and IAS


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

53

Conclusions for ecological restoration

Highlights of the results

54

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

55

Biotic resistance of a community can be strongly influenced by occurrence 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!


Test new species (combinations) based on functional similarity andphylogenetic relatedness

Verify results in field experiments

Develop commercial seed mixtures

Device improved sowing and managing recommendations

Contributions of ecological restoration!

Acknowledgements

Questions ?

References 1

58

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Byun, C., de Blois, S. & Brisson J. (2015) Interactions between abiotic constraint, propagule pressure, and biotic resistance regulate plant invasion. Oecologia, 178, 285–296.

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Hulme, P.E. (2011) Contrasting impacts of climate‐driven flowering phenology on changes in alien and native plant species distributions. New Phytologist, 189, 272–281.

Laughlin, D.C. (2014) Applying trait-based models to achieve functional targets for theory-driven ecological restoration. Ecology Letters, 17, 771–784.

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van der Plas, F. et al. (2016). Jack-of-all-trades effects drive biodiversity–ecosystem multifunctionality relationships in European forests. Nature Communications, 7, 11109.

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