Advanced

Plant species diversity in semi-natural grasslands. Effects of scale, landscape structure and habitat history

Reitalu, Triin LU (2008)
Abstract (Swedish)
Popular Abstract in Swedish

Växters artdiversitet i naturbetesmarker.Effekter av landskapsstruktur och habitathistoria.

I min avhandling har jag undersökt växters artdiversitet i fragmenterade naturbetesmarker, av olika ålder och med olika historisk markanvändning. Jag har även undersökt betydelsen av habitatens isolerinsgrad i dagens och i det förflutna landskapet för dagens artdiversitet med hänsyn till variation i betestryck. Artdiversiteten har undersökts på olika rumsliga nivåer – finskalig artdiversitet (inom samplingsrutor, 0.25-1 m²) och storskalig artdiversitet (inom gräsmarker, >0.1 ha). Jag diskuterar även betydelsen av mina resultat för restaurering och bevarande av naturbetesmarker.

... (More)
Popular Abstract in Swedish

Växters artdiversitet i naturbetesmarker.Effekter av landskapsstruktur och habitathistoria.

I min avhandling har jag undersökt växters artdiversitet i fragmenterade naturbetesmarker, av olika ålder och med olika historisk markanvändning. Jag har även undersökt betydelsen av habitatens isolerinsgrad i dagens och i det förflutna landskapet för dagens artdiversitet med hänsyn till variation i betestryck. Artdiversiteten har undersökts på olika rumsliga nivåer – finskalig artdiversitet (inom samplingsrutor, 0.25-1 m²) och storskalig artdiversitet (inom gräsmarker, >0.1 ha). Jag diskuterar även betydelsen av mina resultat för restaurering och bevarande av naturbetesmarker.

Artrikedom i naturbetesmarker påverkas av habitatens ålder. Inom den storskaliga artdiversiten (på gräsmarksnivå) visade resultaten att både specialister (typiska gräsmarksarter) och generalister hade ackumulerats i äldre betesmarker. Inom den finskaliga artdiversiteten, hade äldre betesmarker högre andel av typiska gräsmarksarter än yngre betesmarker. Betesmark på före detta skogsmark uppvisade större likheter med gammal naturbetesmark än betesmark på före detta åkermark. Resultaten visar även på ett samband mellan mänsklig populationstäthet under sen järnålder (dvs för mer än 800 år sedan) och nutida artdiversitet i gräsmarker – vilket antyder att människans närvaro påverkar artdiversiteten över mycket lång tid.

Habitatens konnektivitet, i motsats till isolering, i landskapet har stor betydelse för artrikedomen i gräsmarker. Den relativa betydelsen av historisk respektive nutida habitatkonnektivitet skilde sig i de olika studierna beroende på hur studien var upplagd – på vilken skala studien genomfördes, vilka ålderskategorier som fanns representerade bland de studerade betesmarkerna, vilka historiska byar som studerades, samt vilka artgrupper (generalister eller specialister) som studien gällde. Resultaten antyder trots allt att finskalig (< 1 m2) artdiversitet är mer känslig för habitatfragmentering än storskalig artdiversitet (på gräsmarksnivå).

I betesmarker där betet upphört påvisades en lägre småskalig artdiversitet än i betade gräsmarker. Det fanns även samband mellan artdiversitet och lätt mätbara faktorer såsom avstånd till bebyggelse och mänsklig populationstäthet – faktorer som kan betraktas som goda indikatorer på intensiteten i skötsel.

Sammantaget visar mina resultat att det är viktigt att ta hänsyn till olika skalnivåer när man studerar artdiversitet i fragmenterade habitat samt att de historiska aspekterna, såsom habitatens ålder och historisk habitatstruktur, är viktigta faktorer att beakta när man utarbetar riktlinjer för restaurering och bevarande av naturbetesmarker. (Less)
Abstract
The thesis examines the impact of present and past landscape structure, habitat history and management on different aspects of present-day plant species diversity in fragmented semi-natural grasslands in Sweden and in Estonia.

Species diversity was significantly associated with present and/or past grassland connectivity in the majority of the studies in the thesis. However, relationships between diversity and habitat connectivity differed between the studies – depending on the the group of studied species and on the scale of study. Present grassland connectivity was positively associated with fine-scale (0.25–1 m2), rather than large-scale (>0.1 ha), species diversity – suggesting that small-scale diversity may be more... (More)
The thesis examines the impact of present and past landscape structure, habitat history and management on different aspects of present-day plant species diversity in fragmented semi-natural grasslands in Sweden and in Estonia.

Species diversity was significantly associated with present and/or past grassland connectivity in the majority of the studies in the thesis. However, relationships between diversity and habitat connectivity differed between the studies – depending on the the group of studied species and on the scale of study. Present grassland connectivity was positively associated with fine-scale (0.25–1 m2), rather than large-scale (>0.1 ha), species diversity – suggesting that small-scale diversity may be more sensitive to habitat fragmentation than large-scale diversity. High landscape diversity in the surroundings of the grassland sites had a positive effect on species richness, emphasizing the importance of considering landscape context when examining the influence of landscape-scale processes on plant communities. Within-habitat environmental heterogeneity had a positive influence on both large-scale and fine-scale species diversity.

Grassland history (age; previous land-use) had a significant impact on present-day species diversity. Large-scale species richness increased with grassland age (30 to >280 years of grassland continuity). While fine-scale species richness was independent of habitat age, the proportion of grassland specialist species on a fine scale was higher in old grasslands and in grasslands on previously forested land than in previously arable sites. Diversity was positively associated with Late Iron Age human population density – indicating that human land-use legacies that influence present-day plant species diversity may reach back more than 800 years.

Grassland management by grazing or mowing is, by definition, essential for the persistence of semi-natural grasslands. Fine-scale species diversity decreased with decreasing grazing intensity in the studied grasslands. The results also suggest that simple descriptors (distance from settlements; human population density) related to human activities may provide good indicators for management processes that influence levels of small-scale plant species diversity.

Comparison of the responses of fine-scale species evenness and richness to differences in landscape structure and history showed that evenness was associated mainly with historical factors, while richness was also influenced by contemporary landscape structure. Patterns of species co-occurrence were associated with different factors on different spatial scales. The results of the thesis emphasize the importance of (a) examining different aspects of species diversity on multiple spatial scales (b) including information on historical habitat distribution, when studying the community responses to habitat fragmentation and when making conservation decisions for fragmented habitats. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Herben, Tomáš, Department of Botany, Faculty of Science, Charles University, Czech Republic
organization
publishing date
type
Thesis
publication status
published
subject
keywords
habitat fragmentation, landscape diversity, habitat connectivity, historical maps, continuity, land-use history
pages
118 pages
defense location
Blå hallen, Ecology Building, Sölvegatan 37, Lund
defense date
2008-10-24 10:00
ISBN
978-91-7105-281-0
language
English
LU publication?
yes
id
2af99a88-e9c6-4382-a4af-e6987a3c1e11 (old id 1241917)
date added to LUP
2008-09-26 11:33:26
date last changed
2016-09-19 08:45:17
@phdthesis{2af99a88-e9c6-4382-a4af-e6987a3c1e11,
  abstract     = {The thesis examines the impact of present and past landscape structure, habitat history and management on different aspects of present-day plant species diversity in fragmented semi-natural grasslands in Sweden and in Estonia.<br/><br>
	Species diversity was significantly associated with present and/or past grassland connectivity in the majority of the studies in the thesis. However, relationships between diversity and habitat connectivity differed between the studies – depending on the the group of studied species and on the scale of study. Present grassland connectivity was positively associated with fine-scale (0.25–1 m2), rather than large-scale (&gt;0.1 ha), species diversity – suggesting that small-scale diversity may be more sensitive to habitat fragmentation than large-scale diversity. High landscape diversity in the surroundings of the grassland sites had a positive effect on species richness, emphasizing the importance of considering landscape context when examining the influence of landscape-scale processes on plant communities. Within-habitat environmental heterogeneity had a positive influence on both large-scale and fine-scale species diversity.<br/><br>
	Grassland history (age; previous land-use) had a significant impact on present-day species diversity. Large-scale species richness increased with grassland age (30 to &gt;280 years of grassland continuity). While fine-scale species richness was independent of habitat age, the proportion of grassland specialist species on a fine scale was higher in old grasslands and in grasslands on previously forested land than in previously arable sites. Diversity was positively associated with Late Iron Age human population density – indicating that human land-use legacies that influence present-day plant species diversity may reach back more than 800 years.<br/><br>
	Grassland management by grazing or mowing is, by definition, essential for the persistence of semi-natural grasslands. Fine-scale species diversity decreased with decreasing grazing intensity in the studied grasslands. The results also suggest that simple descriptors (distance from settlements; human population density) related to human activities may provide good indicators for management processes that influence levels of small-scale plant species diversity.<br/><br>
	Comparison of the responses of fine-scale species evenness and richness to differences in landscape structure and history showed that evenness was associated mainly with historical factors, while richness was also influenced by contemporary landscape structure. Patterns of species co-occurrence were associated with different factors on different spatial scales. The results of the thesis emphasize the importance of (a) examining different aspects of species diversity on multiple spatial scales (b) including information on historical habitat distribution, when studying the community responses to habitat fragmentation and when making conservation decisions for fragmented habitats.},
  author       = {Reitalu, Triin},
  isbn         = {978-91-7105-281-0},
  keyword      = {habitat fragmentation,landscape diversity,habitat connectivity,historical maps,continuity,land-use history},
  language     = {eng},
  pages        = {118},
  school       = {Lund University},
  title        = {Plant species diversity in semi-natural grasslands. Effects of scale, landscape structure and habitat history},
  year         = {2008},
}