grazing as a tool in restoration - uni-muenster.de€¦ · • threatened vegetation types...

Grazing as a tool in restorationCarsten Eichberg

SER Summer School, Münster 2009

Introduction Hypotheses Case studies: Competitors, Microsites, Zoochory Synopsis

Habitat fragmentation• Two aspects: reduction of habitat size and habitat isolation• Small plant populations have a higher extinction risk (Fischer & Stöcklin 1997)• Lower probability of new habitats to be colonised by target species (Hölzel et al. 2009)

Habitat degradation• Nutrient enrichment of the soil by fertilizer application and atmospheric deposition

• Negative relationship between productivity and number of threatened plant species (Süss et al. 2007)

Long‐term conservation requires:‐ Enlargement of existing habitats by including degraded sites with restoration

potential (Bakker & Berendse 1999) ‐ Improvement of habitat connectivity (Lindborg & Eriksson 2004)

Threats to semi‐natural grasslands in Central Europe

Inland dunes in the upper Rhine valley (Germany) –A model system for habitat fragmentation

• Late glacial aeolian transport of calcareous sand from glacial Rhine deposits

• Dry, nutrient‐poor, calcareous ecosystems

• Threatened vegetation types protected by the EU fauna‐flora‐habitat directive:

Frankfurt

N

Darmstadt region

a) Xeric sand calcareous grasslands (Koelerion glaucae)

b) Semi‐natural dry grasslands on calcareous substrates (Allio Stipetum capillatae)


Schwabe & Kratochwil 2009

100 m

N

• Land use changes led to dune fragmentation and degradation

Situation in 2002: two fragmented nature reserves

Situation in 1934: one continuous military training area

Reserve 145 ha

Reserve 2 71 ha

Inland dunes in the upper Rhine valley ‐ A model system for habitat fragmentation

‐ Nutrient enrichment (habitat‐typical succession correlates negatively with soil nutrient contents, especially phosphate; Süß et al. 2004) Site limitation

‐ Seed bank and seed rain poor in target species (Stroh et al. 2002) Seed limitation


Griesheimer Sand

Restoration of inland dune grasslandsEnlargement and (re‐)connection of habitats

Topsoil inversion

Deep sand depositon

Inoculation with raked/mown plant material

Abiotic restoration

Biotic restoration

Management

Donor site

Recipient site

Grazing

Degraded sites Degraded and well‐developed sites

Aim: Establishment of habitatnetworks comprising well‐developed and restored sites(Schwabe & Kratochwil 2009)


Habitat isolation Seed rain (LDD by wind)Photo: M. Stroh; Nov. 2005; Rotböhl

Nutrient-rich fields

Nutrient-rich fieldsRestoredarea

Dune fragment

Dunefragment

Seed rain

Seedbank

Intra-habitat seed dispersal, disturbance, phytomass reductionInter-habitat seed dispersal


Hypotheses

Sheep grazing in open inland sand ecosystems…

1) …suppresses competitive graminoid species of species‐poor mid‐successional stages,

2) …generates microsites suitable for regeneration of subordinate plant species,

3) …leads to seed dispersal and post‐dispersal processes improving connectivity of isolated habitats.

4) These effects lead to a mitigation of seed and (micro)site limitations and an enhancement of plant species diversity.


Method• 17 permanent plots à 80 m²: 9 sheep‐grazed plots vs. 8 non‐grazed plots• Relevés (2000‐2006)• Nature reserve Griesheimer Düne

Reduction of competitive plant species


Results (data not yet published, in prep.)• After a 6‐yr grazing period sheep grazing led to a significant reduction of the competitive grass species Calamagrostis epigejos and a significant increase in phytodiversity.

Creation of microsites: Livestock trails

Eichberg et al. 2008

Method

• Relevés on sheep trails and control plots, nature reserve August‐Euler‐Flugplatz

• Extensive grazing regime: 4‐ to 13‐ha paddocks, 170‐450 sheep, short‐term grazing period (a few days to weeks per year)

Results

• Sheep trails cover ca. 1 % of the paddock area

• Trail development driven by the distribution ofessential resources (water, salt) and requisites(shade)

Shady area

Paddock boundary

Sheep trail


Water tank + salt lick

∗ Sheep trailControl

DCA ordination (eigenvalues: 0.42 Axis 1, 0.06 Axis 2), K: pioneer stages; F, A: mid-succ. stages

Regressive effect in mid‐successional stages

Creation of microsites: Livestock trailsResults

Medicago minima

Cover‐abundance of 7 habitat‐typical annuals (e.g. Medicago minima) higher andof 4 perennials lower on trails as compared to controls (p < 0.05, Wilcoxon test)

Plant species diversity enhanced in community F (p < 0.05; no effect in K and A)


Schwabe et al. 2004

Seed dispersal –One step within the multi‐stage process of plant recruitment


• ca. 1 seed/g dry faeces½ million seeds per

800 sheep per day

• 74 species

• 92 vascular plant species

• 9 Red List species (e.g. Stipa capillata)

• 36 % target species, 35 % ruderal sp., 29 % other sp.

• 34 % species overlap endo‐/epizoochory

• ca. 16‐19 seeds/ 100 cm² fleece

• 53 species

Endozoochory Epizoochory

Eichberg 2005, Wessels 2007

Seed dispersal by sheep: 1) Seed quantities and qualities

- 3‐4 tamed sheep- Hand‐picking of seeds (fleece)- Faecal‐bag method- Pioneer and mid‐succ. sandgrassland stages


Questions

1. The seeds of which species of sand pioneer vegetation are dispersed endozoochorously by sheep?

2. What is the (a) seedling emergence and (b) fruiting success of these species?

3. What are the overall effects of faeces, disturbance and a combination of both factors on (a) the total density of generative individuals emerging and of those fruiting on the plots and (b) the species diversity?

2) Endozoochorous seed dispersal, post‐dispersal fate and soil disturbance


Exp. 2: Field

F‐D‐F+D‐

F‐D+F+D+

F: sheep faeces, D: soil disturbance

Seedling emergence and fruiting success under natural conditions

Methods

Exp. 1: Common garden

Seedling emergence under optimisedconditions (continuous watering)

• Collection of faeces: faecal‐bag method, four sheep

n = 32 faeces samples n = 28 split‐plots

• Exposure of faeces:


Results

• Faeces‐borne seedlings of 28 vascular plant species were foundunder optimised conditions

• 124 ± 25 (mean ± SE) seeds/100 g dry faeces

• Carex hirta (graminoid competitor) most abundant species (47 %)

• 5 threatened species in low abundances (2 %):

Vicia lathyroides, Medicago minima, Phleum arenarium, Silene conica, Carex praecox

Seedling emergence on sheep dung: Common garden experiment



Seedling emergence on sheep dung: Field experiment

Trifolium campestre

Vicia lathyroides

FB: faeces‐borne, SB: soil‐borne%: proportion of faeces‐borne individuals in the total amount of individuals of a species

Faeces‐borne seedlingsof 15 species were foundunder field conditions



Seedling emergence of faeces‐borne seedlings:Exp. 1 (common garden) vs. Exp. 2 (field)

Trifolium campestre

Vicia lathyroides

Environmental filter: stress tolerant plant speciesbenefit from field conditions; competitive specieswere suppressed under field conditions

Reduced in the fieldEnhanced in the field



Fruiting success of faeces‐borne seedlings (field experiment)

Individuals of 5 species reached fruiting stage(1‐5 individuals per species; 2.4 kg dry dung were investigated in total):

Medicago minima

Phleum arenarium

Silene conicaVicialathyroides

Vulpia myuros

all species are:

• Low‐growing annuals

• Stress‐tolerant ruderals (sensu Grime 1977)

• Habitat specialists

threatened in Germany and/or Hesse

www.floraweb.de www.floraweb.de



P: potential seedling emergence (Exp. 1); E: seedlings in the field (Exp. 2);R: fruiting individuals in the field (Exp. 2); 1: year 2003; 2: year 2004

Overall effects of faeces (F) and disturbance (D) in the field experiment

Indiviuals with fruiting success(Proc Mixed, SAS):

Faeces: + (year 1), ‐ (year 2)(faeces x year, p < 0.001)

Disturbance: + (both years, p < 0.01)

No sign. interaction F x D

→ The same effects werefound for species diversity

Mean indiviudal density with SE in parentheses



Summary – Endozoochorous dispersal, post‐dispersal fate, soil disturbance

• Germinable seeds of 28 vascular plant species in sheep faeces

• Ambiguity in seed transport of as well habitat‐typical as competitive species

• Especially threatened species able to establish and set seeds after dispersal but not competitive species

• Increase in local density and diversity of fruiting plant individuals by experimental soil disturbance (mimicking sheep‐mediated gaps); faeces: increase 1st year, decrease 2nd year



3) Epizoochorous seed dispersal: Influence of seed morphology and seed mass

Error: SEn = 3

Seed pool:

Seed mass (mg):

Seed surface:

Method: Classification of seeds naturally attached to sheep fleece, three

sheep, three target plant communities

Results: Seeds of all morphology types are dispersed epizoochorously. Both

seed mass and seed surface impact the percentage of available seed species

being attached (seed pool x seed mass x seed surface, p < 0.001, Proc Mixed).

Sheep fleece (E)Growing vegetation (V)

Wessels et al. 2008


→ Naturally attached seedsreach sink area

Agrimonia procera

ST = sheep transfer (habitat change)

Stipa capillata

1 cm

a

b

a b

4) Epizoochorous seed dispersal: Retention time in sheep fleece

Error: SE

Method: Repeated counts of seeds naturally attached to sheep fleece, theanimals walked a 3‐km inter‐area distance


Wessels et al. 2008

Questions

1. How long is the retention time of achenes ofJ. cyanoides in sheep fleece?

2. How far do sheep transport the achenes?

3. What is the post‐dispersal fate of above‐ground achenes?

4. Does sheep‐epizoochorous dispersal enableJ. cyanoides to set seedlings and establishitself in formerly unsettled habitats?

5. What is the effect of sheep trampling on thehorizontal and vertical displacement ofachenes?

5) Epizoochorous dispersal and post‐dispersal fate


Seed dispersal and seedling establishment

Methods

Two field experiments: in each experiment two paddocks were set up with each twosheep grazing Koelerion glaucae pioneer vegetation

Exp. 2Exp. 1

• 10 cm x 10 cm‐plots à 5 achenes

• 20 grazed plots + 20 controls

• 24‐h grazing period

• 180 achenes/sheep

• Three body parts

• 3‐day grazing period

Seed displacement by trampling


Results

Retention time of J. cyanoides achenes in sheep fleece (Exp. 1)

18 % of the achenes remained > 2 h in the fleeces

94 % of the dispersed and retrieved achenes were located in < 10 m distance from the place of diaspore application

1‐4: sheep individuals



99 % achene loss by predation

C

Fate of above‐ground achenes after dispersal (Exp. 1)

ungerm: ungerminated achenes; germ: germinated achenes; pred: achenes lost by predation; tot mor: total mortality



Paddock Paddock

Transport and establishment processes J. cyanoides (Exp. 1)


Seedling establishment limited by summer drought(mortality: 68 %)


Sc: soil covering class (0‐4); X: remaining fixed on soil surface in lateral position; I: incorporation into the soil; H: hidden; L: release of the achenes from fixed position.

grazed ungrazed

On average 14 % complete incorporation of achenes into the soil (p < 0.001, Fisher‘s exact test)

Trampling effects (Exp. 2)



• Jurinea cyanoides established in a new area after epizoochorousdispersal by sheep

• Establishment was severely limited by several factors:

• Only seedlings derived from buried achenes able to establish

• Sheep trampling enhanced incorporation of achenes into the soillower risk of above‐ground predation

Summary – Epizoochorous seed dispersal and post dispersal fate

‐ short retention time of achenes in the fleeces (82 % remained < 2 h)

‐ high above‐ground predation of achenes (99 %)

‐ high seedling mortality due to drought (68 %)



Synopsis

1. Sheep grazing reduced the cover of Calamagrostis epigejos and enhanced the

(habitat‐typical) phytodiversity.

2. Sheep generated microsites (e.g. livestock trails) supporting subordinate plant

species.

3. Sheep acted as seed dispersal vectors:

Seeds were dispersed in high diversities and densities.

Two modes of dispersal were realized in combination and complement each

other (endo‐, epizoochory).

Transported seeds of habitat‐typical plant species could reach sink habitats

and establish after sheep‐zoochorous dispersal.

These results give support to hypotheses 1‐4.

Roaming sheep flocks have the potential to enhance/maintain phytodiversity

of open inland sand ecosystems and to develop functional habitat networks. In

praxis, stands dominated by fruiting competitors should be treated with

circumspection.


Acknowledgements

Scientific support

• Prof. Dr. Angelika‐Schwabe‐Kratochwil (Darmstadt)

• Dr. Christian Storm (Darmstadt)

• Dr. Saskia Wessels (Houten, NL) and Vegetation Ecology working group (Darmstadt)

Financial support and cooperations

• Federal Ministry for the Environment, Nature Conservation and Nuclear Safety

• German Federal Agency for Nature Conservation

• Evangelisches Studienwerk e.V. Villigst

• Landkreis Darmstadt‐Dieburg

• Regierungspräsidium Darmstadt

• Landschaftspflegehof Stürz

ReferencesBakker, J.P. & Berendse, F. 1999. Constraints in the restoration of ecological diversity in grassland and heathland communities. Trends in Ecology and Evolution 14: 63-68.

Eichberg, C. 2005. Plant-diaspore pools and processes in inland sand ecosystems: soil seed banks, epi- and endozoochory. Ph.D. Thesis, Darmstadt University of Technology, Germany.

Eichberg, C., Storm, C. & Schwabe, A. 2005. Epizoochorous and post-dispersal processes in a rare plant species: Jurineacyanoides (L.) Rchb. (Asteraceae). Flora 200: 477-489.

Eichberg C., Storm C. & Schwabe A. 2007. Endozoochorous dispersal, seedling emergence and fruiting success in disturbed and undisturbed successional stages of sheep-grazed inland sand ecosystems. Flora 202: 3-26.

Eichberg, C., Boes, J. & Schwabe, A. 2008. Which vegetation and seed bank changes are induced by the disturbance regime oflivestock trails? Abhandlungen aus dem Westfälischen Museum für Naturkunde 70: 63-80.

Fischer, M. & Stöcklin, J. 1997. Local extinctions of plants in remnants of extensively used calcareous grasslands 1950-1985. Conservation Biology 11: 727-737.

Hölzel, N., Rebele, F., Rosenthal, G. & Eichberg, C. 2009. Ökologische Grundlagen und limitierende Faktoren der Renaturierung. In: Zerbe S. & Wiegleb G. (Eds.): Renaturierung von Ökosystemen in Mitteleuropa. Spektrum Akademischer Verlag.

Lindborg, R. & Eriksson, O. 2004. Historical landscape connectivity affects present plant species diversity. Ecology 85: 1840-1845.

Schwabe, A. & Kratochwil, A. 2009. Renaturierung von Sandökosystemen im Binnenland. In: Zerbe S. & Wiegleb G. (Eds.): Renaturierung von Ökosystemen in Mitteleuropa. Spektrum Akademischer Verlag.

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Stroh, M., Storm, C., Zehm, A. & Schwabe, A. 2002. Restorative grazing as a tool for directed succession with diaspore inoculation: the model of sand ecosystems. Phytocoenologia 32: 595-625.

Süss, K., Storm, C., Zehm, A. & Schwabe, A. 2004. Succession in inland sand ecosystems: which factors determine the occurrenceof the tall grass species Calamagrostis epigejos (L.) Roth and Stipa capillata L.? Plant Biology 6: 465-476.

Süss, K., Storm, C., Zimmermann, K. & Schwabe, A. 2007. The interrelationship between productivity, plant species richness andlivestock diet: a question of scale? Applied Vegetation Science 10: 169-182.

Wessels, S. 2007. The contribution of sheep zoochory to the conservation and restoration of target plant communities in isolated sand ecosystems. Ph.D. Thesis, Darmstadt University of Technology, Germany.

Wessels, S., Eichberg, C., Storm, C. & Schwabe, A. 2008. Do plant-community-based grazing regimes lead to epizoochorousdispersal of high proportions of target species? Flora 203: 304-326.

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