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Conservation of semi-natural grasslands: Effects of different management methods on biodiversity
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. (Theoretical Biology)ORCID iD: 0000-0001-9262-4440
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Species-rich semi-natural grassland are valuable habitats in the agricultural landscape as they may contain a high diversity of both plant and animal species, as well as provide essential ecosystem services like pollination. To keep these habitats open and to maintain the biodiversity in them, management like grazing or mowing is necessary. Due to changed agricultural practices many semi-natural grasslands have been lost, e.g. due to secondary succession after abandonment or use of more intense management practices. As limited resources are available for the management and restoration of semi-natural grasslands, research is needed to find the best available management method that maintains biodiversity at a low cost. Therefore, the overall aim of this thesis was to use existing data to compare effects of different management methods and explore their effect on the biodiversity of semi-natural grasslands. More specifically, effects of grazing vs. mowing, different mowing frequencies and different mowing techniques were investigated using data from Swedish, European and global studies, with the aim of using the results to formulate management recommendations.

Paper I investigated the effect of mowing using a sickle bar mower or a grass trimmer at a 5-cm or 0-cm cutting height on plant indicator species of good management for species richness, poor management and excess nitrogen. Analyses of data from a Swedish 11-year field experiment revealed that over time, there was no difference in the odds of finding indicators of any type for any of the mowing techniques. This suggest that there is a similar effect of mowing using a sickle bar mower and a grass trimmer on the floristic composition of semi-natural grasslands.

Paper II and III investigated effects of different management methods using a Swedish long-term, multi-site field experiment. Paper II compared effects of grazing vs. mowing and paper III compared effects of annual mowing and mowing every third year. Both papers used meta-analyses to compare effect on plant indicator species of good management for species richness and poor management. Additionally, paper II examined effects of indicators of excess nitrogen, while paper III also examined effects on plant species richness and diversity and species-wise responses. For paper II, analyses revealed an increase in the odds of finding indicators of good management for species richness in mowed plots and increased odds of finding indicators of excess nitrogen in grazed plots. For paper III, meta-analyses revealed a small drop in plant species richness and diversity, and an increase in woody and tall-grown species, when mowing every third year. However, there were no difference in the odds of finding indicators of good management for species richness or poor management between mowing frequencies. These results suggest that mowing is a better long-term management method compared to grazing in seminatural grasslands in southern Sweden, while annual mowing have a slightly more positive effect compared to mowing every third year.

Paper IV and V investigated management effects on a larger scale, by systematically reviewing studies comparing effects of grazing vs. mowing or different mowing frequencies on grassland flora and fauna, and analysing the data using meta-analysis. The included mowing frequencies were annual mowing vs. mowing every fifth, third or second year, or mowing two, three or four times a year. Paper IV analysed data from 35 studies from across the globe, and revealed a slightly more positive effect of grazing on the biodiversity of seminatural grasslands. However, results differed for different grassland characteristics like e.g. geography, grassland type and previous management. Paper V analysed data from 29 European studies, and revealed a more positive effect of mowing more frequently than once per year. However, the differences were small and varied for different grassland characteristics. For example, a higher mowing frequency was better in more productive grasslands. These results suggest that grazing is slightly better than mowing and that mowing less frequently, e.g. every other year, can be a viable management method in less productive grasslands, as a way of using limited funds more efficiently.

The results from the papers included in this thesis suggest that different management methods have different effects on the biodiversity of semi-natural grasslands. However, in many cases these differences are relatively small. Thus, to a certain extent one of the most important factors for semi-natural grassland biodiversity seems to be the fact that management occurs at all, while the actual management methods is of less importance. Hence, choosing the most suitable management method for a certain situation should be based on conservation aims, grassland conditions, the previous management practice used, the cost of management, the availability of different management methods and previous research. 

Abstract [sv]

Näringsfattiga ängs- och hagmarker är en viktig del av jordbrukslandskapet, då de ofta innehåller en hög artrikedom av både växt- och djurarter, samtidigt som de bidrar till upprätthållandet av viktiga ekosystemtjänster som exempelvis pollinering. För att bevara diversiteten i dessa habitat är det viktigt att de sköts på rätt sätt, via exempelvis bete eller slåtter, eftersom dessa skötselmetoder motverkar igenväxning av gräsmarker, samtidigt som de bibehåller de näringsfattiga förhållandena genom avlägsnandet av biomassa. På grund av intensifierade jordbruksmetoder har många artrika ängs- och hagmarker gått förlorade. Detta beror bland annat på att skötsel upphört på grund av för låg avkastning, eller en ökad användning av gödsling som förändrat förhållandena i gräsmarkerna. Med anledning av detta har många av de arter som är bundna till denna habitattyp blivit mer ovanliga och hotade. Begränsade resurser är tillgängliga för skötsel och restaurering av ängs- och hagmarker och därför behövs forskning som undersöker effekten av olika skötselmetoder, för att hitta de som har mest positiv effekt till en så låg kostnad som möjligt. Det övergripande målet med denna avhandling var därför att undersöka effekten av olika skötselmetoder på diversiteten i ängs- och hagmarker, för att ta fram passande skötselrekommendationer.

Slåtter med verktyg som gräsröjare, som sliter sönder vegetationen, har länge ansetts ha en negativ effekt i jämförelse med skärande verktyg som exempelvis lie eller slåtterbalk, men få studier har undersökt detta. I artikel I undersöktes därför effekten av olika slåttermetoder på växter, i en ängsmark i södra Sverige. De undersökta metoderna var slåtter med slåtterbalk och slåtter med gräsröjare på två olika klipphöjder (o eller 5 cm). Effekterna undersöktes på indikatorarter för god hävd, brist på hävd och överskott av kväve. Resultaten visade att oddsen för att hitta de olika indikatorarterna inte skiljde sig mellan slåttermetoderna, vilket tyder på att de har en liknande effekt på vegetationen i ängsmarker.

Artikel II jämförde effekten av bete och slåtter och artikel III effekten av slåtter en gång per år och slåtter vart tredje år. Bägge artiklarna använde sig av data från ett långtidsexperiment som utfördes i elva olika gräsmarker i södra Sverige, och jämförde skötseleffekter på växtindikatorarter för god hävd och brist på hävd. Artikel II undersökte även effekten på indikatorarter för överskott av kväve medan artikel III även tittade på effekter på artrikedom och diversitet, samt effekter på individuella arter. I artikel II visade analyserna att oddsen att hitta indikatorer för god hävd ökade med slåtter medan oddsen att hitta indikatorer för överskott av kväve ökade med bete. Analyserna i artikel III visade på en liten minskning av artrikedomen och diversiteten samt en ökning av vedarter och högväxta arter vid slåtter vart tredje år. Det fanns dock ingen skillnad i oddsen att hitta indikatorarter för god hävd eller brist på hävd mellan de två slåtterfrekvenserna. Dessa resultat tyder på att slåtter är en bättre skötselmetod. jämfört med bete, medan slåtter en gång per år har en något mer positiv effekt jämfört med slåtter vart tredje år.

Artikel IV och V undersökte effekten av skötselmetoder på en större skala, genom att systematiskt gå igenom, granska och analysera data från studier som undersökt effekterna av bete och slåtter och olika slåtterfrekvenser, på floran och faunan i ängs- och hagmarker. Artikel IV analyserade data från 35 studier från hela världen som jämfört bete och slåtter, och fann en något mer positiv effekt av bete jämfört med slåtter på diversiteten av växt- och djurarter. Dock skiljde sig effekterna beroende på förhållandena i de undersökta gräsmarkerna, exempelvis beroende på geografi, gräsmarkstyp och tidigare skötsel. Artikel V analyserade data från 29 europeiska studier som jämfört slåtter en gång per år med slåtter vart femte, tredje eller vartannat år, eller slåtter två, tre eller fyra gånger per år. Analyserna visade på en något mer positiv effekt av slåtter oftare än en gång per år, men skillnaderna mellan slåtterfrekvenserna var små och de skiljde sig beroende på förhållandena i gräsmarkerna. Exempelvis så var en högre slåtterfrekvens bättre i mer produktiva gräsmarker. Resultaten från dessa två artiklar tyder på att bete är något bättre än slåtter, och att i mindre produktiva gräsmarker kan slåtter mer sällan än en gång per år, exempelvis vartannat år, vara ett sätt att använda de begränsade resurserna tillgängliga för skötsel på ett mer effektivt sätt.

Resultaten från artiklarna i denna avhandling visar att olika skötselmetoder har olika effekt på diversiteten i ängs- och hagmarker. Dock var dessa skillnader relativt små, vilket tyder på att i viss utsträckning är den viktigaste faktorn att skötsel faktiskt sker, medan själva skötselmetoden är av mindre betydelse. Därför är det viktigt att basera valet av skötselmetod i ett specifikt fall på bevarandemål, abiotiska förhållanden, tidigare skötselmetoder, kostnaden och tillgängligheten för olika skötselmetoder samt tidigare forskning.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. , p. 59
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1899
National Category
Ecology
Identifiers
URN: urn:nbn:se:liu:diva-144796DOI: 10.3384/diss.diva-144796ISBN: 9789176853795 (print)OAI: oai:DiVA.org:liu-144796DiVA, id: diva2:1178698
Public defence
2018-04-13, Planck, Fysikhuset, Campus Valla, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2018-01-30 Created: 2018-01-30 Last updated: 2018-03-09Bibliographically approved
List of papers
1. Mowing for biodiversity: grass trimmer and knife mower perform equally
Open this publication in new window or tab >>Mowing for biodiversity: grass trimmer and knife mower perform equally
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2014 (English)In: Biodiversity and Conservation, ISSN 0960-3115, E-ISSN 1572-9710, Vol. 23, no 12, p. 3073-3089Article in journal (Refereed) Published
Abstract [en]

Mowing of semi-natural grasslands is an important management method to maintain the conservation value and species-richness of this habitat. Mowing using cutting instruments, e.g. sickle bar mowers, is thought to be superior by practitioners compared with other mechanical instruments that tears off the plant material, e.g. grass trimmers. However, almost no studies exist that supports this assumption. We analysed a 12-year field trial in a semi-natural grassland in south-eastern Sweden, with the aim of determining which mowing technique best maintains the conservation value of semi-natural grasslands. Two mowing techniques were compared: mowing using a hand-pushed sickle bar mower (a type of knife mower), or mowing using a grass trimmer at a 5-cm or 0-cm cutting height. The odds that a recorded species belongs to a group of indicator species were calculated for sample plots, and odds ratios were calculated contrasting treatments. Three types of indicator species classification systems were used: (i) indicators of management for species richness, (ii) indicators of excess nitrogen and (iii) indicators of lack of management. The odds ratios were calculated for years 1–5, 7 and 12 of the trial. In addition, Principal Response Curve analysis was performed to analyse the change in vegetation composition over time and ANOVA for plant species richness in plots. The results showed that over time there were no differences in the odds of finding indicators of any of the three types, for any of the mowing techniques. Furthermore, there were no apparent change in vegetation composition and only a small effect on richness. These results suggest that mowing using a sickle bar mower or a grass trimmer had the same effect on the floristic composition of grasslands, and both techniques can be recommended for use in semi-natural grasslands.

Place, publisher, year, edition, pages
Springer Publishing Company, 2014
Keywords
Indicators, Management, Meta-analysis, Mowing techniques, Odds ratio, Semi-natural grassland, Sweden
National Category
Biological Sciences
Identifiers
urn:nbn:se:liu:diva-111926 (URN)10.1007/s10531-014-0765-8 (DOI)000343908600010 ()
Available from: 2014-11-10 Created: 2014-11-10 Last updated: 2018-01-30Bibliographically approved
2. The conservation benefit of mowing vs grazing for management ofspecies-rich grasslands: a multi-site, multi-year field experiment
Open this publication in new window or tab >>The conservation benefit of mowing vs grazing for management ofspecies-rich grasslands: a multi-site, multi-year field experiment
2015 (English)In: Nordic Journal of Botany, ISSN 0107-055X, E-ISSN 1756-1051, Vol. 33, no 6, p. 761-768Article in journal (Refereed) Published
Abstract [en]

Species-rich semi-natural grasslands in Europe are becoming more fragmented and many species that depend on thishabitat type are rare and threatened today. Management methods like mowing and grazing are needed to preserve remaininggrasslands. Because management is costly it is important to use the most cost-effective as well as the most beneficialmanagement method, but few studies have compared mowing and grazing. We investigated the effect of mowing andgrazing on grassland vegetation using data from 11 long-term field trials situated in southern Sweden. We calculated thechange in the odds of finding species belonging to three different groups of indicators at the start of the treatment and after8 and 14 years. The used indicator groups were indicators of good management, excess nitrogen and poor management.The results revealed an increase in the odds of finding indicators of good management in mowed plots and an increasein finding indicators of excess nitrogen in grazed plots. The odds of finding indicators of poor management remainedunchanged. Results from sub-analysis of the grazing intensity showed a more negative effect from grazing with low grazingintensity than normal/high grazing intensity. Therefore, mowing is the best long-term management method for seminaturalgrasslands in Sweden and grazing using a low grazing intensity should be avoided.

Place, publisher, year, edition, pages
Nordic Society Oikos, 2015
National Category
Environmental Sciences related to Agriculture and Land-use
Identifiers
urn:nbn:se:liu:diva-123378 (URN)10.1111/njb.00966 (DOI)000368428700017 ()
Note

Funding agencies: Swedish Board of Agriculture; Stiftelsen Oscar och Lili Lamms minne

Available from: 2015-12-14 Created: 2015-12-14 Last updated: 2018-01-30
3. The biodiversity cost of reducing management intensity in species-rich grasslands: Mowing annually vs. every third year
Open this publication in new window or tab >>The biodiversity cost of reducing management intensity in species-rich grasslands: Mowing annually vs. every third year
2017 (English)In: Basic and Applied Ecology, ISSN 1439-1791, E-ISSN 1618-0089, Vol. 22, p. 61-74Article in journal (Refereed) Published
Abstract [en]

Mowing is an important management method for species-rich semi-natural grasslands in Europe. Since mowing is costly, it is important to find a balance between mowing frequency and conservation benefits. We compared vegetation data from eleven field trials situated in southern Sweden that involved two mowing regimes, annually and every third year, as well as a no-management control. After approximately 14 years, mowing every third year showed (i) a drop in species richness and Shannon and GiniSimpson diversity indices, (ii) an increase in woody species, and (iii) increases in tall-grown species. However, there were no apparent changes in (iv) species that were indicative of poor management, nor (v) those indicating good management. For one of the trials, data after 38 years were also evaluated. Compared with annual mowing, there were strong negative changes in the number of species in the untreated control, while the results were conflicting for mowing every third year. In conclusion, the expected loss of conservation values from reduced mowing intensity was 5060% of the loss after abandonment. The outcomes, however, varied among the eleven sites. (C) 2017 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER GMBH, URBAN & FISCHER VERLAG, 2017
Keywords
Cutting; Indicators; Meta-analysis; Mowing; Odds ratio; Response ratio; Semi-natural grassland; Sweden
National Category
Ecology
Identifiers
urn:nbn:se:liu:diva-141735 (URN)10.1016/j.baae.2017.07.004 (DOI)000409994800007 ()
Note

Funding Agencies|Swedish Board of Agriculture

Available from: 2017-10-05 Created: 2017-10-05 Last updated: 2018-01-30
4. Grazing vs. mowing: A meta-analysis of biodiversity benefits forgrassland management
Open this publication in new window or tab >>Grazing vs. mowing: A meta-analysis of biodiversity benefits forgrassland management
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2016 (English)In: Agriculture, Ecosystems & Environment, ISSN 0167-8809, E-ISSN 1873-2305, Vol. 222, p. 200-212Article, review/survey (Refereed) Published
Abstract [en]

To maintain the high biodiversity of semi-natural grasslands, management by grazing or mowing isneeded. Given the limited resources and few remaining areas, the best management method should beused. However, only a few studies comparing the effects of mowing and grazing on grassland biodiversityexists. Therefore, the goal of the present review was to extract as much data as possible from theliterature and evaluate them using a meta-analysis approach. We searched scientific and grey literaturefor studies comparing the effects of grazing and annual mowing on outcomes relevant for biodiversityconservation. We identified 35 relevant studies on grazing and annual mowing that provided datasuitable for the meta-analysis. We found that grazing generally had a more positive effect on theconservation value of semi-natural grasslands compared to mowing, but effect sizes were generally smallto moderate for most contrasts. Furthermore, effects varied across some grassland characteristics e.g. fordifferent grassland types, with grazing and mowing having a similar effect or mowing having a morepositive effect in certain cases. Our results suggest, that in most cases grazing should be the preferredmanagement method when managing for grassland conservation.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Conservation management Cutting Evidence-based Livestock grazing Meadow Pasture Semi-natural grassland
National Category
Ecology
Identifiers
urn:nbn:se:liu:diva-125592 (URN)10.1016/j.agee.2016.02.008 (DOI)000384383600021 ()
Note

Funding agencies: Swedish Board of Agriculture

Available from: 2016-02-26 Created: 2016-02-26 Last updated: 2018-02-21

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