Interacting effects of fertilization, mowing and grazing on plant species diversity of 1500 grasslands in Germany differ between regions

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Basic and Applied Ecology 14 (2013) 126–136

nteracting effects of fertilization, mowing and grazing on plant speciesiversity of 1500 grasslands in Germany differ between regions

tephanie A. Sochera,∗, Daniel Pratia, Steffen Bocha, Jörg Müllerb, Henryk Baumbachb,c,onja Gockele,l, Andreas Hempb,j, Ingo Schöningd,e, Konstans Wellsf,g, Francois Buscoth,k,lisabeth K.V. Kalkof,1, Karl Eduard Linsenmairi, Ernst-Detlef Schulzed,olfgang W. Weissere,l, Markus Fischera,b

Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, SwitzerlandInstitute of Biochemistry and Biology, University of Potsdam, Maulbeerallee 1, D-14469 Potsdam, GermanyInstitute of Botany, Herbaria Haussknecht, Botanical Garden, University Jena, Philosophenweg 16, D-07743 Jena, GermanyMax Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, D-07745 Jena, GermanyInstitute of Ecology, Friedrich-Schiller-University Jena, Dornburgerstr. 159, D-07743 Jena, GermanyInstitute of Experimental Ecology, University of Ulm, Albert-Einstein Allee 11, D-89069 Ulm, GermanyBiodiversity and Climate Research Centre (BiK-F), D-60325 Frankfurt (Main), GermanyHelmholtz Centre for Environmental Research – UFZ, Department of Soil Ecology, Theodor-Lieser-Strasse 4, D-06120 Halle, GermanyTheodor-Boveri-Institute for Biosciences, University of Würzburg, Am Hubland, D-97074 Würzburg, GermanyDepartment of Plant Systematics, University of Bayreuth, Universitätsstr. 30, D-95447 Bayreuth, GermanyChair of Soil Ecology, Institute of Biology, University of Leipzig, Johannis-Allee 21-23, D-04103 Leipzig, GermanyDepartment of Ecology and Ecosystem Management, Terrestrial Ecology, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2,-85350 Freising, Germany

eceived 25 January 2012; accepted 20 December 2012vailable online 20 January 2013

bstract

The relationship of different types of grassland use with plant species richness and composition (functional groups oferbs, legumes, and grasses) has so far been studied at small regional scales or comprising only few components of land use.e comprehensively studied the relationship between abandonment, fertilization, mowing intensity, and grazing by different

ivestock types on plant diversity and composition of 1514 grassland sites in three regions in North-East, Central and South-est Germany. We further considered environmental site conditions including soil type and topographical situation. Fertilized

rasslands showed clearly reduced plant species diversity (−15% plant species richness, −0.1 Shannon diversity on fertilized

rasslands plots of 16 m2) and changed composition (−3% proportion of herb species), grazing had the second largest effectsnd mowing the smallest ones. Among the grazed sites, the ones grazed by sheep had higher than average species richness+27%), and the cattle grazed ones lower (−42%). Further, these general results were strongly modulated by interactions betweenhe different components of land use and by regional context: land-use effects differed largely in size and sometimes even in irection between regions. This highlights the importance of comparing different regions and to involve a large number of plots

∗Corresponding author. Tel.: +41 31 631 4923; fax: +41 31 631 4911.E-mail address: [email protected] (S.A. Socher).

1 Deceased.

439-1791/$ – see front matter © 2012 Gesellschaft für Ökologie. Published by Elsevier GmbH. All rights reserved.ttp://dx.doi.org/10.1016/j.baae.2012.12.003

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S.A. Socher et al. / Basic and Applied Ecology 14 (2013) 126–136 127

hen studying relationships between land use and plant diversity. Overall, our results show that great caution is necessary whenxtrapolating results and management recommendations to other regions.

usammenfassung

Der Einfluss unterschiedlicher Grasland-Nutzungstypen auf den Artenreichtum und die Zusammensetzung der PflanzenKräuter, Leguminosen und Gräser) wurde bisher nur auf kleiner regionaler Skala oder nur mit wenigen Landnutzungtypenetestet. In einer vergleichenden Studie zeigen wir die Effekte von Verbrachung, Düngung, Mahd und Beweidung durch unter-chiedlichen Tierbestand auf Artenreichtum und Zusammensetzung der Pflanzen auf 1514 Grasländern in drei unterschiedlichenegionen in Nordost, Zentral und Südwest Deutschland. Zusätzlich wurden standortbedingte Umweltfaktoren wie Bodentypennd topographische Daten mit einbezogen. Gedüngte Graslandflächen hatten klar reduzierte Artendiversität (−15% Artenzahl,0.1 Shannon Diversität auf gedüngten Flächen von 16 m2) und veränderte Zusammensetzung (−3% Anteil an Kräutern),

ie Effekte der Beweidung waren am zweitgrößten und die der Mahd am kleinsten. Mahd mit mittlerer Intensität (2 Schnittero Jahr) und Schafbeweidung erhöhten die Artenzahl (+27%), während Rinderbeweidung die Artenzahl verringerte (−42%).iese allgemeinen Muster wurden durch Wechselwirkungen zwischen Landnutzungstypen und durch verschiedene regionaleontexte moduliert: die Größe und teilweise sogar Richtung der Unterschiede zwischen Landnutzungstypen unterschied sichwischen den Regionen. Das verdeutlicht die Bedeutung, verschiedene Regionen miteinander zu vergleichen und viele Unter-uchungsflächen einzubeziehen, um verläßliche Aussagen über Beziehungen zwischen Landnutzung und Artendiversität machenu können. Zusammenfassend ist also grosse Vorsicht geboten, wenn Ergebnisse und Nutzungsempfehlungen über Regioneninweg verallgemeinert werden sollen.

2012 Gesellschaft für Ökologie. Published by Elsevier GmbH. All rights reserved.

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eywords: Biodiversity exploratories; Functional groups; Land use

ntroduction

Agricultural management has a strong effect on biodi-ersity (Houghton 1994; Sala et al. 2000; Poschlod 2005;llenberg & Leuschner 2010; Maskell, Smart, Bullock,hompson, & Stevens 2010). In Germany, half of the land-cape is dedicated to agriculture (47%) and 30% of thegricultural area is used as meadows or pastures. Most ofhese grasslands are intensively used for haymaking or cat-le herding and only 5% are used in organic farming at lowntensity (Statistisches Jahrbuch 2009). Highly intensivelysed grasslands are characterized by the application of largemounts of fertilizer (up to 400 kg/ha/year), high mowing fre-uencies (four to five times per year), and high stocking rates70 livestock units/ha). On less intensively used grasslandsertilizer applications are lower or absent, sheep replace cat-le as main grazers, and the first and often only cut is doneate in the year to ensure successful plant recruitment (Rookt al. 2004).

In Central Europe, grasslands are among the most species-ich ecosystems, but during the last century increasingntensification has led to a species decline across many taxa.ertilization, in particular of semi-natural and nutrient-poorrasslands, has led to a drastic decline of the diversitiesf plants and other taxa (Kölliker, Stadelmann, Reidy, &osberger 1998; Hansson & Fogelfors 2000; Fischer & Wipf002; Jacquemyn, Brys, & Hermy 2003; Hautier, Niklaus,

Hector 2009; Kleijn et al. 2009). Clearly, the gradient

f land use intensity reflects the opposed interests betweenigh productivity and maintenance of diversity (Klimek,ichter, Hofmann, & Isselstein 2007). In addition, as Central

ll2

Livestock type; Shannon diversity

uropean grasslands were established largely from wood-ands during a long history of low-intensity anthropogenicand use, the currently ongoing abandonment of uneconomi-al sites and the subsequent succession threaten these systemsnd their diversity.

A recent meta-analysis by Kleijn et al. (2009) across30 grasslands in six European countries showed that plantpecies richness generally decreases with higher nitrogennput (Kleijn et al. 2009). However, other studies reportedighest plant species richness at moderate levels of fertilizerpplication (Zechmeister, Schmitzberger, Steurer, Peterseil,

Wrbka 2003). Furthermore, fertilization intensity is oftenonfounded with mowing intensity. A study across 84 Aus-rian farms showed that plant species richness decreased withimultaneously increasing mowing and fertilization intensitySchmitzberger et al. 2005), but could not disentangle theontributions of both management factors to the observedpecies richness decline.

In addition to fertilization and mowing, grazing inten-ity is a major factor influencing grassland plant diversity.eviews suggest negative effects of more intense grazing onlant species diversity in mesotrophic grasslands (Stewart &ullin 2008) but positive effects at higher levels of productiv-

ty (Proulx & Mazumder 1998). Such dependence of grazingffects on nutrient availability and moisture suggests that theevel of grazing supporting high diversity increases with siteroductivity (Kondoh 2001). In addition to grazing intensity,razing effects may differ between sheep, cattle and other

ivestock, although the effect of livestock type is consideredess important than that of grazing intensity (Stewart & Pullin008). Moreover, within livestock species body size matters

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28 S.A. Socher et al. / Basic and

ore for effects on biodiversity than breed does (Rook et al.004). Interpreting studies on diversity effects of land useype (fertilization, type of livestock, and grazing intensity) isften complicated by simultaneous variation of further envi-onmental site conditions, such as slope, elevation, or soilype, and because farmers manage marginally suited sitesess intensively (Klimek et al. 2007). A comprehensive anal-sis of land use effects on plant diversity should thereforenclude such site variation in order to distinguish land useffects from those of environmental factors. Most previoustudies were restricted in scope by either focusing on singlespects of land use, on habitats of high conservation value,r on single regions. However, the interacting effects amongifferent aspects of land use, such as fertilization, grazing,nd mowing intensities, have not yet been addressed by aarge scale study across different regions.

Plant species diversity can be assessed by several meas-res. Clearly, species richness is the most commonly usedndex (Magurran 2004). Shannon’s evenness includes infor-

ation on the dominance structure within communities, andhannon diversity combines species richness and evenness.long similar lines, many other indices have been described

see Smith & Wilson 1996). However, these measures ofiversity indices do not capture whether and how differ-nt functional plant groups respond distinctly to differentspects of land use. Functional plant groups were definedccording to several morphological or physiological char-cteristics (Roscher et al. 2004; Ellenberg & Leuschner010). The most commonly used classification into herbs,rasses, and legumes is of both agricultural and conservationnterest.

In this paper, we study land use effects on vascular plantpecies diversity (plant species richness, Shannon index, andvenness) and functional group composition of about 1500rassland sites. We studied three distinct regions in Germany,he so-called Biodiversity Exploratories (Fischer, Kalko, et al.010), with different geographic background to cover a broadariety of landscape types including post-glacial lowlands,illy lands, and low mountain ranges, together representa-ive for large parts of Germany. In each region the studyovers fertilized and unfertilized grasslands of different landse types (fallows, meadows, pastures, and mown pastures).astures were grazed by the typical livestock types for Ger-any, i.e. sheep, cattle, and horse. We also considered several

nvironmental parameters including soil type, elevation, andlope.

In particular we address the following questions:

(i) How do different components of land use affect plantspecies diversity?

(ii) How do different functional plant groups respond to landuse?

iii) How consistent are land use effects on plant speciesdiversity and composition across the three studyregions?

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Ecology 14 (2013) 126–136

aterials and methods

tudy area

We studied vascular plant diversity in the context of a largeesearch program on the relationships between land use, bio-iversity, and ecosystem processes, the German Biodiversityxploratories project (www.biodiversity-exploratories.de).he three Biodiversity Exploratories are situated in three

egions, each with a variety of differently used grasslandsnd forests (Fischer, Bossdorf, et al. 2010; Fischer, Kalko,t al. 2010). The exploratory Schorfheide-Chorin in the low-ands of NE Germany forms part of the UNESCO Biosphereeserve Schorfheide-Chorin. The exploratory Hainich-Dün

s situated in the hilly lands of Central Germany and includeshe National Park Hainich. The exploratory Schwäbischelb in a low mountain range of SW Germany is situated

n the UNESCO Biosphere Reserve Schwäbische Alb. Allhree Biodiversity Exploratories cover different grasslands:rom semi-natural forms used at very low intensity to veryntensively managed ones. In each of the three exploratories,rasslands are scattered among arable fields, forests, and set-lement areas. To study the effect of land use on grasslands comprehensively as possible, we assessed plant diversityn circa 500 grassland plots in each Biodiversity Exploratory.lots were selected to cover the whole range of land use typesharacteristic for that region. Plots had a minimum distancef 500 m from each other when the land use type was the samend of 200 m when it was different (see Fischer, Bossdorf,t al. 2010 for details on plot selection).

and use, soil, and topographic information

We obtained information on the current land use of thelots from questionnaires answered by farmers and landwners, including the land use type (fallow, meadow, pas-ure, and mown pasture), livestock type (cattle, horse, horsend cattle, or sheep), fertilization (fertilized and unfertili-ed plots), and mowing intensity (number of cuts; Fischer,alko, et al. 2010). Whereas fallows were abandoned sitesf formerly managed grasslands, mown pastures desig-ate grasslands mown once per year either before or afterhey were grazed, hence they experience biomass removaly grazing and mowing within the same year. In con-rast, pastures and meadows refer to exclusive biomassemoval by either grazing or mowing within a year. Welso inferred the history of land use by asking the farm-rs how long the sites had been used as grassland andhether land use intensity changed recently. However, as

his information was not available for all plots and becauseime used as grassland showed neither a main effect on

pecies richness nor an interaction effect with the regions,e excluded it from the final models. Furthermore, mostf the grasslands had the same land use for the last 5ears.

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For each plot, a soil sample had been taken and soilype classified according to the World Reference Base ofoil Resources (IUSS Working Group WRB 2007; Fischer,ossdorf, et al. 2010; Fischer, Kalko, et al. 2010). The main

oil groups were Histosols in Schorfheide-Chorin (318 plots),ambisols in Hainich-Dün (235), and Cambisols (205 plots)nd Leptosols (194 plots) in the Schwäbische Alb. Finally,opographic information on elevation and slope of each plotas derived from digital terrain models. Full information on

and use and soil type was available for 1292 out of 1514rassland plots.

egetation relevés

From 25 May to 15 August 2007 we recorded vegeta-ion relevés in 1514 plots in the three exploratories. Wee-assessed 138 plots in May 2009 and discarded the earlierelevés because of unreliable data mainly from species-richrassland that had been recorded too late in the season.n all plots vegetation relevés were taken in an area ofm × 4 m situated next to the position where the soil coread been sampled. Moreover, we recorded the ground covery each vascular plant species to the nearest percent fol-owing the nomenclature of Wisskirchen & Häupler (1998).or each plot we determined vascular plant species richnessS), Shannon Index of diversity (H′) and Evenness (J′) as′ = −∑

pi × ln pi, and J′ = H′/ln S, where pi is the proportionf total abundance of the ith species. We also classified vas-ular plant species according to the functional groups herbs,rasses, and legumes and determined the absolute and relativepecies richness for each class.

tatistical analyses

To test the effect of the different components of land usen measures of vascular plant diversity we used generalizedinear models. We analyzed six response variables: speciesichness and diversity indices (S, H′ and J′) of vascular plants,nd the relative species richness of herb, legume, and grasspecies (in percent).

As our comparative data set was unbalanced with respecto the distribution of specific combinations of land use typesver exploratories (Fischer, Bossdorf, et al. 2010), we usedeparate models for more balanced subsets of data (seeollowing paragraphs) to examine differences between (i)allows and managed grasslands, (ii) fertilized and unferti-ized grasslands, (iii) mowing effects in meadows and mownastures, and (iv) livestock type effects of sheep, cattle, andorses. In all models we fitted the exploratory and the co-ariates (soil type, elevation, and slope) first, followed by the

omponents of land use.

Because there were no fallows in the Schwäbische Alb wexamined the effect of fallows for the other two exploratories.or all further analyses, we excluded fallows.

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Ecology 14 (2013) 126–136 129

To examine the effect of fertilization we ran a modelncluding land use type (pasture, meadow, mown pasture),ertilization, and the interactions land use type × fertilization,xploratory × land use type, exploratory × fertilization, andxploratory × land use type × fertilization.

To examine the effect of mowing intensity we ran a modelncluding land use type (excluding fallows and pastures),he number of cuts, the interaction between them, and theirnteractions with the respective exploratory.

To examine the effect of sheep, cattle, and horses wean a model including land use type (excluding fallows andeadows), fertilization, livestock type, and the two-way and

hree-way interactions between exploratory, land use type,ertilization, sheep, and other livestock type. Because wexpected larger differences between sheep grazing and thether livestock types than between cattle and horse grazedlots, we split the livestock type effect by first testing theffect of sheep grazing and then the remaining effect of thether livestock types (cattle, horses, or cattle and horses). Theequence of fitting the land use variables turned out not tohange statistical significances and therefore we just presenthe sequence outlined above for each model. It turned out toe highly necessary to include environmental site conditionssoil type, elevation, and slope) as they were significant in allested models. We also tested for temporal effects (year andate of recording), but these were not significant and there-ore excluded from the models. We performed all statisticalnalyses with the software R version 2.10.0 (R Developmentore Team 2009).

esults

ifferences between the biodiversityxploratories

On all 1514 plots we recorded a total of 623 vascular plantpecies, ranging from 365 vascular plant species in the 465lots in the Schwäbische Alb, to 353 in the 515 plots inainich-Dün, to 318 in the 534 plots in Schorfheide-Chorin.Vascular plant species richness per 16 m2, Shannon diver-

ity and the proportions of herb and legume species wereighest in the Schwäbische Alb, lower in the Hainich-ün exploratory and lowest in the Schorfheide-Chorin

xploratory (see Appendix A: Table 1). Mean evennessas quite similar in all three exploratories. Thus, while the

izes of the regional species pools were not very differ-nt between the three exploratories, there was pronouncedegional variation in plant community diversity and compo-ition at the plot level. Accordingly, the factor exploratorytrongly affected species diversity per plot in all mod-ls.

Variation in species richness per plot among regions wasuch larger than the corresponding variation in total rich-

ess per region (coefficient of variation, CV = 25.1% for plotpecies richness vs. CV = 7.1% for total species richness),

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Table 1. Summary of analyses of variance of effects of exploratory, covariates (soil type, elevation, and slope), and fallow on vascular plantspecies diversity and composition on 16 m2 plot for the two exploratories with fallows.

Df Vascular plantspecies richness

Shannondiversity

Evenness Proportion ofherb species

Proportion ofgrass species

Proportion oflegume species

F F F F F F

Exploratory (E) 1 157.60*** 46.95*** 0.01 47.59*** 63.33*** 96.01***

Soil type 11 7.53*** 2.49** 1.62 5.40*** 6.30*** 26.79***

Elevation 1 21.81*** 7.78** 0.40 0.54 0.45 5.19*

Slope 1 46.47*** 29.67*** 6.46* 14.74*** 27.49*** 2.51Fallow yes/no (Fa) 1 9.41** 1.53 6.06* 3.70 11.76*** 5.79*

E × Fa 1 27.66*** 21.27*** 4.62* 1.95 0.14 1.17Residuals 917

Residual mean squares 50.80 0.191 0.011 0.013 0.013 0.004

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ndicating that differences between the regional species poolontributed only little to variation in local richness.

ifferences between fallows and managedrasslands

Overall, the 52 fallow plots in Schorfheide-Chorin (37lots) and Hainich-Dün (15 plots) had lower evenness−0.04), proportion of grass (−10.8%), and proportion ofegume species (−30%) than managed grassland plots, butimilar number of vascular plants (+49%) and Shannon diver-ity (−0.24). However, these relationships varied stronglyepending on the exploratory (Table 1, Fig. 1). Whereas inainich-Dün fallow plots had higher vascular plant species

ichness (+49%) and higher Shannon diversity (+0.3) than

anaged plots, whereas evenness was very similar (−0.001)

here were slightly fewer vascular plant species (−4%), lowerhannon diversity (−0.2), and evenness (−0.057) for fallow

ig. 1. The difference between fallows (N = 52) and managedN = 1355) grasslands in vascular plant species richness (numberf species per 16 m2) for Hainich-Dün and Schorfheide-Chorin, thewo exploratories where fallows occurred and for both exploratoriesombined. Error bars denote 1SE.

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lots than for managed plots in Schorfheide-Chorin. Overall,his indicates that the relationship between abandonment andrassland diversity differs very much between study regions.

ifferences between fertilized and unfertilizedrasslands

Fertilization of plots decreased vascular plant species rich-ess (−15%), Shannon diversity (−0.1), and a small decreasen the proportion of herb species (−3%), but increasedhe proportion of grass species (+6%; Table 2). Differ-nces between fertilized and unfertilized grasslands differedetween exploratories for vascular plant species richnessFig. 2), proportion of legume species, and proportion ofrass species, as indicated by significant fertilization-by-

xploratory effects (Table 2, Fig. 3). Whereas the differencesetween fertilized and unfertilized sites were more pro-ounced in the Schwäbische Alb and Hainich-Dün, they were

ig. 2. The difference between fertilized (N = 614) and unfertilizedN = 792) grasslands in vascular plant species richness (number ofpecies per 16 m2) in all exploratories combined, in the Schwäbischelb, Hainich-Dün, and Schorfheide-Chorin. Error bars denote 1SE.

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S.A. Socher et al. / Basic and Applied Ecology 14 (2013) 126–136 131

Table 2. Summary of analyses of variance of effects of exploratory, covariates (soil type, elevation, and slope), land use type (meadows,pastures, and mown pastures), and fertilization on vascular plant species diversity and composition on 16 m2 plot.

Df Vascular plantspecies richness

Shannondiversity

Evenness Proportion ofherb species

Proportion ofgrass species

Proportion oflegume species

F F F F F F

Exploratory (E) 2 264.95*** 152.42*** 24.89*** 72.48*** 78.63*** 71.14***

Soil type 11 5.86*** 2.67** 1.89* 6.49*** 7.32*** 33.27***

Elevation 1 61.52*** 36.94*** 5.08* 2.12 3.58 4.10*

Slope 1 143.35*** 48.02*** 2.64 26.31*** 48.88*** 0.35Land use type (LUT) 2 65.49*** 30.35*** 8.60*** 22.73*** 26.24*** 8.85***

Fertilization (F) 1 93.76*** 28.37*** 1.05 4.32* 7.20** 1.14LUT × F 2 10.15*** 11.66*** 6.77** 2.70 2.11 2.24E × LUT 4 5.59*** 16.13*** 19.19*** 12.79*** 13.09*** 22.96***

E × F 2 22.84*** 2.15 1.60 1.99 3.01* 5.24**

E × LUT × F 4 6.83*** 8.90*** 6.80*** 3.44** 4.13** 11.36***

Residuals 1261

Residual mean squares 51.30 0.157 0.010 0.010 0.010 0.003

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ot significant in the Schorfheide-Chorin exploratory, if ana-yzed separately by exploratory (data not shown).

The three land-use types meadow, mown pasture, andasture differed in all measured variables, but again withronounced differences among the exploratories (Table 2,ig. 4). In the Schwäbische Alb, pastures had higher vascu-

ar plant species richness and Shannon diversity, followedy meadows and mown pastures, whereas evenness andunctional group composition was remarkably similar acrossand-use types. In Hainich-Dün, pastures had higher vascularlant species richness, Shannon diversity, and a higher pro-ortion of herbs, followed by mown pastures and meadows.

inally, in Schorfheide-Chorin land-use types were overallery similar in diversity and composition, with only a slightlyigher number of vascular plants on pastures (Fig. 4).

ig. 3. The difference between fertilized (N = 614) and unfertili-ed (N = 792) grasslands in the proportion of species number ofrasses, legumes, and herbs in all exploratories combined, in thechwäbische Alb, Hainich-Dün, and Schorfheide-Chorin.

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Furthermore, differences between fertilized and unferti-ized sites interacted with the land use types for speciesichness, Shannon diversity, and evenness. Fertilized mownastures and meadows had more vascular plant species thannfertilized ones, whereas fertilized pastures had fewer vas-ular plant species than unfertilized ones. Shannon diversitynd evenness were higher for fertilized meadows than fornfertilized ones, whereas they were lower for fertilizedown pastures and pastures than for unfertilized plots.Finally, significant three-way interactions between

xploratory, land-use types, and fertilization indicate thathe effect of fertilization is strongly context dependent: it

ot only depends on the land-use types which are fertilizedut this interaction between fertilization and land use variescross the three study regions (Table 2).

ig. 4. The difference between the three land use types (meadow= 496, mown pasture N = 361, and pasture N = 498) in vascu-

ar plant species richness (number of species per 16 m2) for allxploratories combined, and for the Schwäbische Alb, Hainich-Dün,nd Schorfheide-Chorin. Error bars denote 1SE.

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Table 3. Summary of analyses of variance of effects of exploratory, covariates (soil type, elevation, and slope), land use type, and the numberof cuts on vascular plant species diversity and composition on 16 m2 plots for mown grasslands.

Df Vascular plantspecies richness

Shannondiversity

Evenness Proportion ofherb species

Proportion ofgrass species

Proportion oflegume species

F F F F F F

Exploratory (E) 2 135.28*** 94.03*** 30.11*** 43.14*** 41.73*** 76.29***

Soil type 11 1.91* 2.46** 1.79 2.72** 2.79** 12.65***

Elevation 1 31.40*** 16.93*** 3.39 3.25 4.16* 0.44Slope 1 12.62*** 2.56 0.03 2.45 3.72 0.04Land use type (LUT) 1 1.84 5.00* 13.93*** 0.63 0.38 4.24*

Number of cuts (NC) 1 5.92* 0.39 0.02 2.30 2.96 5.85*

LUT × NC 1 0.16 0.48 0.14 7.48** 7.54** 0.02E × LUT 2 6.02** 15.98*** 16.63*** 18.42*** 17.90*** 26.12***

E × NC 2 15.43*** 5.15** 2.15 2.86 3.31* 1.29E × LUT × NC 1 8.06** 1.11 0.001 0.39 0.38 0.28Residuals 780

Residual mean squares 35.90 0.15 0.01 0.01 0.01 0.00

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Fig. 5. The difference between mowing frequency (cut onceN = 421, twice N = 286, or three times a year N = 149) in vascu-lar plant species richness (number of species per 16 m2) in allexploratories combined, in the Schwäbische Alb, Hainich-Dün, andSd

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In summary, the generally negative relationship of fertil-zation and the positive relationship of pastures with plantpecies diversity and proportion of herb species differedetween exploratories.

elationship of mowing frequency withrassland diversity

Analyzing mowing frequency for meadows and mown pas-ures revealed an increase of vascular plant species richnessnd a decrease of the proportion of legume species with theumber of cuts (Table 3) with pronounced variation amonghe exploratories. Whereas increased mowing frequencyecreased vascular plant species richness (−19%, Fig. 5) andhannon diversity (−0.45), and increased the proportion ofrass species (+26%) from one to three cuts in Hainich-Dün,t increased vascular plant species richness (+12%), Shan-on diversity (+0.17) and the proportion of grass species+10%) in Schorfheide-Chorin. In the Schwäbische Alb vas-ular plant species richness and Shannon diversity wereighest on plots mown twice per year, and the proportionf grass species decreased by 13% with increasing cuttingrequency. Together, these results, too, illustrate that relation-hips between land use and diversity differ between regions.

Furthermore, the effect of mowing frequency on the pro-ortion of herb and grass species differed between meadowsnd mown pastures (Table 3). Meadows cut twice per year hadhe highest proportion of grass and the lowest proportion oferb species, whereas mown pastures cut twice had the lowestroportion of grass species and the highest proportion of herb

pecies, which indicates that species composition respondedifferently to mowing, depending on land use type.

Overall, the differences between grasslands of differentutting frequencies and the interactions between land use

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chorfheide-Chorin (meadows and mown pastures only). Error barsenote 1SE.

omponents and cutting frequency were rather small, whereashe interaction between exploratory and cutting frequencyas pronounced (Fig. 5).

ifferences between grasslands grazed byifferent livestock types

Analyzing the effect of livestock type on pastures andown pastures showed that vascular plant species rich-

ess (+27%) and Shannon diversity (+0.3) were significantly

igher on plots grazed by sheep than by other livestock (cattlend cattle and horse). Plots grazed by cattle and horses hadigher vascular plant species richness (+12%) and a higher

Page 8

S.A. Socher et al. / Basic and Applied

Fig. 6. The difference between grasslands grazed by different livestock types (sheep N = 289, cattle N = 461, cattle and horse N = 33,and horse N = 76) in vascular plant species richness (number ofspecies per 16 m2, pastures and mown pastures only). Error barsdenote 1SE.

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lar plant species richness, Shannon diversity and evenness,whereas on meadows, its effects were less pronounced oreven positive. Possibly this was due to different species com-

roportion of grass (+15%), but a lower proportion of herbpecies (+9%) than plots grazed by cattle only (see Appendix: Table 2, Fig. 6).Pastures grazed by sheep had higher vascular plant species

ichness (+38%) and proportion of herb species (+8%)ut lower proportion of grass species (−18%) comparedith mown pastures. In addition, unfertilized plots grazedy sheep had higher Shannon diversity (+0.26), evenness+0.015), and proportion of herb species (+6%) comparedith fertilized plots (see Appendix A: Table 2). In con-

rast, unfertilized plots grazed by cattle and horses had aower number of vascular plants, Shannon diversity, androportion of herbs, but a higher proportion of grasseshan fertilized plots. Thus, differences between grasslandsrazed by different livestock types largely depended onhether grasslands were additionally mown and fertilizedr not.

Finally, in the Schwäbische Alb the differences betweenites grazed by sheep and by other livestock were higheror Shannon diversity (+0.17), evenness (+0.02), and pro-ortion of herb species (+9%) but lower for the proportionf legume species (−32%) than in Hainich-Dün. Sheep pas-ures in the Schorfheide-Chorin differed from the ones inhe two other exploratories, but this type of land use wasoo rare (number of plots = 8) to allow statistically robustomparisons.

In summary, the differences in diversity and compo-ition between grasslands grazed by different livestockypes were mainly driven by differences between sheep-razed and other pastures, whereas differences between thether livestock types (cattle, horses, or cattle and horses)ere comparatively small. In contrast to other aspectsf land use (see above), relationships of livestock typeith land use were rather consistent across explorato-

ies. p

Ecology 14 (2013) 126–136 133

iscussion

bandonment of management and plantiversity

It has been suggested that abandonment of grassland useeads to a decline in plant species diversity due to the competi-ion for light that follows decreased occurrence of vegetationaps as safe sites for germination, or due to increaseditter accumulation (Jacquemyn, van Mechelen, Brys, &onnay 2011). Such an effect was absent in Schorfheide-horin with its typically wetter soils. This might be due

o more similar species composition between fallows andanaged grasslands in the Schorfheide-Chorin, or due to

nknown differences in time since abandonment. In contrast,allows in Hainich-Dün showed increased diversity, prob-bly because abandonment occurred only recently and thencrease in diversity is caused by a temporary effect of bushncroachment. Moreover, we cannot exclude the possibil-ty that species-rich grasslands were more often abandonedhan poorer grasslands in Hainich-Dün, thus reversing theause-effect relationship between management and diversity.

From a conservation point of view our results indicate thatlant species may decline after grassland management aban-onment in some sites, as suggested by other studies (Rookt al. 2004; Maurer, Weyand, Fischer, & Stöcklin 2006), buthis effect may be absent or even opposite elsewhere. Becausebandonment effects may change over time, long-term obser-ational studies are better suited to assess its consequencesor diversity than our comparative approach is.

ertilization and plant diversity

The generally lower vascular plant species richness ofertilized grasslands (Stevens, Dise, Mountford, & Gowing004; Crawley et al. 2005; Silvertown et al. 2006; Kleijn et al.009) differed between land use types (meadows, mown pas-ures, and pastures) and exploratories. Fewer vascular plantpecies and lower Shannon diversity on fertilized plots wasossibly caused by a competitive advantage of taller grasses,hich increased with fertilization, over smaller herbs. Thiseneral trend was due to the findings in the Schwäbische Albnd Hainich-Dün, while patterns differed in the Schorfheide-horin, possibly due to its wetter soils (Table 2). We couldot test for a unimodal fertilization-diversity relationshipsGrime 1973; Wilson & Tilman 2002; but see Adler et al.011), because we did not have information on the amountf fertilizer for all the plots. In a subset of 150 plots we foundlinearly negative instead of a hump-shaped relationship

etween productivity and diversity (Socher et al. 2012).On pastures, fertilization was most detrimental for vascu-

ositions and larger heterogeneity of the species composition

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34 S.A. Socher et al. / Basic and

n pastures compared with meadows. Moreover, it may resultrom differences in light availability, which may be higher ineadows due to cutting and may thus allow more species to

ersist (Hautier et al. 2009) and more seedlings to germinate.he small increase of species diversity with fertilization oneadows is surprising and likely caused by fertilization ineadows of lower initial species diversities and a decrease

f meadows at higher initial diversities. Our results indicategenerally high sensitivity of pasture vegetation in Hainich-ün and the Schwäbische Alb to fertilization. However, our

esults also show that this did not apply to all regions, asertilization effects differed in the Schorfheide-Chorin. Thisrevents us from generalizing our results on fertilization andimultaneously confirms the advantage of including threeistinct regions in this study. Also, the omnipresence of inter-ctions of fertilization effects with effects of land-use typesnd of exploratories highlights the importance of studyingifferent aspects of land use simultaneously across severaleographical regions.

owing and plant diversity

Pooled over the meadows and mown pastures of thexploratories vascular plant species richness was high-st at intermediate cutting frequency (two cuts per year),upporting predictions based on the intermediate disturb-nce hypothesis (Grime 1973; Kondoh 2001). Mowingay initially increase light availability, thereby promoting

ubdominant species and germination rates (Collins 1998;autier et al. 2009), but at higher cutting frequencies only

ew species are able to cope with such a degree of disturbancend thus diversity decreases.

Effects of mowing frequency differed between meadowsnd mown pastures. Mowing twice per year favored grassver herb species on meadows, but not on mown pastures.n meadows, grasses may be favored due to their cutting-olerant growth form and herbs may suffer from low seedlingecruitment due to the absence of safe sites for recruitmentn relatively homogenous swards. In mown pastures, how-ver, mowing reduces the cover of those species that arevoided by grazers, which are often herbs, and thus mow-ng has an equalizing effect on the competitive balance of thepecies.

The effects of mowing frequency varied considerably inirection depending on region, with an optimum in Schwäbis-he Alp, a reduction in Hainich-Dün and a stimulation ofpecies richness in the Schorfheide grasslands (Table 3).rom a conservation point of view these results indicate

hat mowing at intermediate levels generally enhances plantpecies richness, but that this general pattern is modified ineveral ways. It strongly depends on geographic region, dif-

ers between functional plant groups, and the latter effectdditionally depends on whether sites are additionally grazed.his suggests that there is no best universal mowing fre-uency to promote plant species richness, but that mowing

ta

Ecology 14 (2013) 126–136

egimes need to be adapted to regional and local circum-tances.

ivestock type and plant diversity

Among the pastures and mown pastures we recordedigher diversity, evenness and proportion of herbs at sitesrazed by sheep than by cattle or horses. The promotion oferb species on sheep pastures could be due to the ability ofheep to create high fine-scale sward heterogeneity (Proulx

Mazumder 1998; Klimek, Marini, Hofmann, & Isselstein008) offering higher niche diversity (Maurer et al. 2006).owever, as we did a comprehensive comparative study in

he field and not an experiment, it may also be that sheeprazed pastures had been established at nutrient-poorer sitesf initially higher species diversity.

Our results indicate that promoting plant species richnessy grazing calls for careful selection of livestock types andtocking densities, according to regional conditions, becauseivestock types may differ in their effects on species diver-ity and composition. In our case, based on detailed landse information for a subset of 150 plots, grazing intensitynumber of livestock × grazing duration per ha) did not dif-er between sheep and cattle grazed plots and only slightlymong regions (Blüthgen et al. 2012). However, it is likelyhat in other regions grazing intensity varies between live-tock types and may have contributed to idiosyncratic grazingffects in different regions (Rook et al. 2004; Stewart & Pullin008).

ifferences between regions

To assess whether results – and derived conservation rec-mmendations – can be generalized, we included manyifferent land use types and environmental site conditions inhree distinct geographic regions. Repeatedly, relationshipsetween land use and plant species diversity and compositioniffered between regions, although all regions comprised theame basic land use varieties. Most likely the regional differ-nces may be explained by the prevalent soil types in the threeegions, with many wet, organic Histosols in Schorfheidend dry, shallow Leptosols in the Schwäbische Alb (IUSSorking Group WRB 2007). The differences in relationships

etween land use type and plant diversity in the differentxploratories demonstrate that results and conservation con-lusions cannot simply be generalized across regions, but thatheir interpretation requires careful consideration of regionaleculiarities.

onclusions

Our study suggests that, among the land use types appliedo German grasslands, fertilization has the largest and neg-tive effects on plant species diversity and composition,

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ollowed by positive effects of grazing and mixed effectsf mowing. Conserving high vascular plant species rich-ess calls for avoiding fertilization especially of pastures.mong the grazed sites, sheep grazed pastures had higher

pecies richness, while cattle grazing decreased species rich-ess. An important message of our study is that these generalesults are strongly context dependent, in particular the effectf mowing, highlighting the importance of comparing dif-erent regions and involving a large number of study plotshen studying land use effects on plant diversity. It calls for

arefully comparing environmental conditions before extrap-lating results and management recommendations betweenegions.

cknowledgements

We dedicate this article to the memory of our friend, col-eague and co-author Elisabeth K.V. Kalko, who very sadlyassed away during the final stage of this work. We thankll local teams supporting us during the vegetation period,specially Metke Lilienthal, Ralf Lauterbach, Martin Fellen-orf, Jörg Hailer, Uta Schumacher, Ulf Pommer, and Claudiaeilwinder. Further, we thank Jens Nieschulze for providing

opographic data, Simone Pfeiffer and Ilka May for projectnfrastructure. We thank Prof Hövemeyer and three anony-

ous reviewers for helpful comments on the manuscript.e thank the DFG for funding in the framework of theFG Priority Program 1374 “Infrastructure-Biodiversity-xploratories” (FI1246/6-1, FI1246/9-1) and the Universityf Bern. Field work permits were given by the respon-ible state environmental offices of Baden-Württemberg,hüringen, and Brandenburg (according to § 72 Bbg-atSchG).

ppendix A. Supplementary data

Supplementary data associated with this article cane found, in the online version, at http://dx.doi.org/10.016/j.baae.2012.12.003.

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