Function of small habitat elements for enhancing plant diversity in different agricultural landscapes

doi:10.1016/j.biocon.2013.11.015

Biological Conservation

Volume 169, January 2014, Pages 206-213

https://doi.org/10.1016/j.biocon.2013.11.015 Get rights and content

Highlights

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We investigated the importance of small habitat elements for grassland plant diversity.
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Smallest share of specialists was found in small habitats in modern agricultural landscapes.
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β-Diversity was highest in the most intensively managed agricultural landscape.
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Species richness declined with distance to grasslands in modern landscapes.
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Small habitats provide an important function for plant richness at a landscape scale.

Abstract

The extensive transformation of agricultural landscapes worldwide has led to a decrease in grassland species related to traditional low-intensive farming. To properly manage and protect species, habitats and ecosystems in any of these landscapes requires a better understanding of direct and indirect effects of the processes driving biodiversity decline. In this study, we investigated how small habitat elements, represented by mid-field islets and road verges, in different types of agricultural landscapes can sustain a regional species pool for plant diversity otherwise associated to semi-natural grasslands. Although semi-natural grasslands had higher total and specialist richness, we found that small habitat elements harboured relatively high plant species richness, especially in a landscape with many semi-natural grasslands left. In the most intensively managed landscape, total richness declined as distance to the nearest semi-natural grassland increased. In contrast, β-diversity was highest in these landscapes indicating that small habitats are also negatively affected by distance to grassland. We found that species trait composition varied depending on habitat and landscape. The results confirm that fragmentation shape trait composition within plant communities, e.g. plant size, clonality, longevity, and dispersal traits. We conclude that small habitat elements increase the total area available to grassland species present in the landscape, boosting the spatio-temporal dynamics of grassland communities. Small habitat elements may hence function as refugia or stepping stone habitats, especially in intensively utilized agricultural landscapes, and should be regarded as a functional part of a semi-natural grassland network, analogous to a meta-population.

Introduction

Land-use change leading to loss, isolation and degradation of habitats is often viewed as one of the main causes driving species decline at local, regional and global scales (Ewers and Didham, 2006, Kuussaari et al., 2009). The most severe change occurred during the last century, when traditionally low intensive farming was either abandoned or converted into intensified and specialized agriculture (Sutherland, 2002, Stoate et al., 2009). Both changes threaten biodiversity (Poschlod et al., 2005, Lindborg et al., 2008) by either highly exploited landscapes with vast crop fields and very little natural habitats, or abandoned farmlands dominated by commercial forests and overgrown fields and grasslands (Tschartke et al., 2012). Still, in either landscape there might be both small, so-called remnant, habitats left from the former traditional landscape and more recent habitats like road verges. To properly manage and protect species, habitats and ecosystems in any of these landscapes requires a better understanding of direct and indirect effects of the processes driving biodiversity decline.

Landscape composition is a factor steering biodiversity patterns at both local and landscape scale (Fahrig et al., 2011). The composition and quality of the landscape matrix, surrounding a focal patch, may influence species richness and abundance (Ricketts, 2001, Cook et al., 2002, Debinski, 2006, Öckinger et al., 2012). Landscapes with intermediate structural complexity have been found to support more species than homogenous landscapes (Tscharntke et al., 2005). Hence habitat patches in complex, more heterogeneous landscapes potentially receive a higher diversity of colonizing species from the surrounding species pool (Tschartke et al., 2012). Species-rich core areas with high habitat quality are essentially acting as source habitats for species survival at large scales (Bengtsson et al., 2003, Leibold et al., 2004, Rand et al., 2006), and the spill-over of organisms from these habitats to agricultural areas have been well documented (e.g. Thies and Tscharntke, 1999, Ricketts et al., 2008). Small marginal habitats found outside protected areas, such as road verges, shading trees, mid-field islets, and cropland set asides may also be important for biodiversity (Tscharntke et al., 2005, Kleijn and Baldi, 2005, Cousins, 2006), functioning as refugia or sources of dispersal (Dorrough et al., 2007, Cousins and Lindborg, 2008, Auffret and Cousins, 2011). Contributing to dispersal among fragments they enhance colonization and decease local extinctions (Fischer and Stöcklin, 1985), which may mitigate negative effects caused by fragmentation and isolation even in quite species-poor agricultural landscapes (McIntyre and Hobbs, 1999, Vandermeer and Perfecto, 2007).

Although many species react negatively to habitat deterioration, loss and isolation, there may be a range in their response as an effect of variation in life-history traits (Fischer and Stöcklin, 1985, Verheyen and Hermy, 2004). Dispersal ability is suggested to explain plant community patterns and the recolonization process (Vellend et al., 2007, Götzenberger et al., 2012). Hence, life-history traits such as canopy height (Cadotte et al., 2006, Thomson et al., 2011) or seed production, e.g. seed size (Jakobsson and Eriksson, 2000), seed dispersal attributes and vectors (Ozinga et al., 2004, Tremlová and Münzbergová, 2007) are often examined in a dispersal context. Empirical studies have proposed that directional animal dispersal might be a key trait increasing species robustness to habitat fragmentation. (Montoya et al., 2008, Sutton and Morgan, 2009). In contrast to dispersal related traits, plant longevity and clonal reproduction are important for plant survival in a long-term perspective (Marini et al., 2012). In grassland systems, long-lived plants, often with clonal propagation tend to build up remnant population systems in abandoned or isolated grasslands, where local populations may persist over periods long enough to bridge unfavourable phases of successional development (Eriksson, 1996, Honnay and Bossuyt, 2005, Lindborg, 2007). Such remnant populations may increase the persistence of a plant community and help to explain cases of high local species diversity, e.g. the semi-natural grasslands of Northern Europe.

In this study, we investigate if small habitat elements in rural landscapes can sustain a regional species pool for plant diversity usually associated with semi-natural grasslands. To estimate the importance of these small habitats for landscape diversity, we examined the species–area relationship by calculating species accumulation curves. As a measure of the variation in species identity between sites in a landscape, we calculated β-diversity that may link diversity measures across scales (Anderson et al., 2006). We examined two different types of small habitat elements: (1) mid-field islets, i.e. small semi-natural areas isolated in crop fields, and not managed today, and (2) road verges, i.e. linear areas connecting habitats in a landscape and are today managed for traffic safety. We specifically addressed the following questions: (i) how a large share of plant species richness associated with managed semi-natural grasslands can be preserved in small habitats depending on landscape fragmentation? (ii) is plant species richness (both total and grassland specialists) in small habitats affected by landscape matrix and distance to nearest semi-natural grassland? If so, (iii) is this also detected in β-diversity (species turnover) and species traits (dispersal or persistence related)?

Section snippets

Landscape selection

Three rural landscapes with different matrix configuration were selected in south-central Sweden: Selaön (59°24′N, 17°10′E); area 15 km², Öllösa (59°8′N, 17°0′E) area 14 km² and Nynäs (58°50′N, 17°24′E); area 10 km². Selaön is a modern and fragmented agricultural landscape with a landscape matrix dominated by open agricultural fields and only little semi-natural grassland left (5%: Cousins and Eriksson, 2008). Öllösa is a landscape dominated by commercial forests and small-scale farming with

Species richness

Ninety-six out of 261 plant species found across all three landscapes were grassland specialists. Semi-natural grasslands did not differ significantly in total richness among the three landscapes, but grassland specialist richness in the modern forest landscape was markedly lower than in the traditional and modern agricultural landscape (Table 1, Fig. 1). However, there was a significant difference in total richness in the midfield-islets habitat, where the modern forest landscape had highest

Effect on the species pool

The total richness and richness of grassland specialists found in the small habitat elements was dependent on both type of element, distance to semi-natural grasslands and type of landscape matrix surrounding these habitats, but in significantly different ways. Species richness declined with distance to grassland habitat in the modern agricultural landscape, which was not detected in the other, more heterogeneous, landscapes. In addition, the grassland specialists were positively related to the

Acknowledgements

The authors thank J. Lindgren and S. Malmgren for vegetation sampling on the semi-natural grasslands in Nynäs and Öllösa; S. Malmgren is acknowledged for the GIS support. J.P. held an open-postdoctoral scholarship granted to S.C. by the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS). This study was partially funded by the EkoKlim project at Stockholm University and SAPES at Lund University.

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Citation Excerpt :
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Function of small habitat elements for enhancing plant diversity in different agricultural landscapes

Highlights

Abstract

Introduction

Section snippets

Landscape selection

Species richness

Effect on the species pool

Acknowledgements

No evidence of a plant extinction debt in highly fragmented calcareous grasslands in Belgium

Biol. Conserv.

Multivariate dispersion as a measure of beta diversity

Ecol. Lett.

Past and present management influences the seed bank and seed rain in rural landscape mosaic

J Appl. Ecol.

Landscape-moderated importance of hedges in conserving farmland bird diversity of organic vs. conventional croplands and grasslands

Biol. Conserv.

Forest Ecol. Manage.

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Ambio

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Am. Nat.

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Ecology

Island theory, matrix effects and species richness patterns in habitat fragments

Ecol. Lett.

A handbook of protocols for standardised and easy measurement of plant functional traits worldwide

Austr. J. Botany

Plant species richness in midfield islets and road verges – the effect of landscape fragmentation

Biol. Conserv.

Landscape history and soil properties affect grassland decline and plant species richness in rural landscapes

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The influence of field shape, area and surrounding landscape an plant species richness in grazed ex-fields

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Plant species occurrences in a rural hemiboreal landscape: effects of remnant habitats, site history, topography and soil

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After the hotspots are gone: land use history and grassland plant species diversity in a strongly transformed agricultural landscape

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Remnant grassland habitats as source communities for plant diversification in agricultural landscapes

Biol. Conserv.

The movement ecology and dynamics of plant communities in fragmented landscapes

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