Jaan Liira

Bio: Jaan Liira is an academic researcher from University of Tartu. The author has contributed to research in topics: Species richness & Biodiversity. The author has an hindex of 39, co-authored 131 publications receiving 8071 citations. Previous affiliations of Jaan Liira include Autonomous University of Madrid & Sewanee: The University of the South.

Indicators for biodiversity in agricultural landscapes: a pan‐European study

Abstract: Summary 1. In many European agricultural landscapes, species richness is declining considerably. Studies performed at a very large spatial scale are helpful in understanding the reasons for this decline and as a basis for guiding policy. In a unique, large-scale study of 25 agricultural landscapes in seven European countries, we investigated relationships between species richness in several taxa, and the links between biodiversity and landscape structure and management. 2. We estimated the total species richness of vascular plants, birds and five arthropod groups in each 16-km 2 landscape, and recorded various measures of both landscape structure and intensity of agricultural land use. We studied correlations between taxonomic groups and the effects of landscape and land-use parameters on the number of species in different taxonomic groups. Our statistical approach also accounted for regional variation in species richness unrelated to landscape or land-use factors. 3. The results reveal strong geographical trends in species richness in all taxonomic groups. No single species group emerged as a good predictor of all other species groups. Species richness of all groups increased with the area of semi-natural habitats in the landscape. Species richness of birds and vascular plants was negatively associated with fertilizer use. 4. Synthesis and applications. We conclude that indicator taxa are unlikely to provide an effective means of predicting biodiversity at a large spatial scale, especially where there is large biogeographical variation in species richness. However, a small list of landscape and land-use parameters can be used in agricultural landscapes to infer large-scale patterns of species richness. Our results suggest that to halt the loss of biodiversity in these landscapes, it is important to preserve and, if possible, increase the area of semi-natural habitat.

How landscape structure, land-use intensity and habitat diversity affect components of total arthropod diversity in agricultural landscapes

Abstract: 1. Agricultural intensification poses a serious threat to biodiversity as a consequence of increased land-use intensity, decreased landscape heterogeneity and reduced habitat diversity. Although there is interest in the preservation of total species richness of an agricultural landscape (γ diversity), the effects of intensification have been assessed primarily by species richness at a local scale (α diversity). This ignores species richness between local communities (β diversity), which is an important component of total species richness. 2. In this study, measures of land-use intensity, landscape structure and habitat diversity were related to γ, α and β diversity of wild bees (Apoidea), carabid beetles (Carabidae), hoverflies (Syrphidae), true bugs (Heteroptera) and spiders (Araneae) within 16 local communities in 24 temperate European agricultural landscapes. 3. The total landscape species richness of all groups was most strongly affected by increased proximity of semi-natural habitat patches. Bees also decreased in landscapes with a high intensity of farmland management, demonstrating additive effects of both factors. 4. Separating total species diversity into components, the decrease in total species richness could be attributed primarily to a decrease in species diversity between local communities. Species richness of the local communities of all investigated groups decreased with increasing land-use intensity and, in the case of spiders, decreasing proximity of the semi-natural habitat patches. 5. The effect of increased habitat diversity appeared to be of secondary importance to total species richness but caused a shift in the relative contribution of α and β diversity towards the latter.

Composition of root-colonizing arbuscular mycorrhizal fungal communities in different ecosystems around the globe

Abstract: Summary 1 Arbuscular mycorrhizal (AM) fungi are obligate root symbionts that are present in most terrestrial ecosystems and have roles in plant mineral nutrition, carbon cycling and biotic interactions. In this work, 26 publications were surveyed that report on the occurrence of natural root-colonizing AM fungi identified using rDNA region sequences. A total of 52 host plant species were investigated. Sixteen publications provided data enabling a comparison to be made of AM fungal taxon richness and community composition across 36 host plant species and 25 locations. Ninety-five fungal taxa (small subunit rRNA gene sequence types) were involved, 49 of which were recorded from at least two study sites, and 65 from more than one host plant species. 2 The number of AM fungal taxa per host plant species differed between habitat types: a significantly higher richness was found in tropical forests (18.2 fungal taxa per plant species), followed by grasslands (8.3), temperate forests (5.6) and habitats under anthropogenic influence (arable fields and polluted sites, 5.2). 3 AM fungal communities exhibit differing compositions in broadly defined habitat types: tropical forests, temperate forests and habitats under anthropogenic influence. Grassland locations around the world host heterogeneous AM fungal communities. 4 A number of AM fungi had a global distribution, including sequence types related to the Glomus intraradices/fasciculatum group, G. mosseae, G. sp. UY1225 and G. hoi, as well as the Glomus and Scutellospora types of unknown taxonomic affiliation. Widespread taxa occur in both natural and anthropogenic (disturbed) habitats, and may show high local abundance. However, about 50% of taxa have been recorded from only a single site. 5 The current global analysis of AM fungal communities suggests that soil micro-organisms may exhibit different distribution patterns, resulting in a high variability of taxon richness and composition between particular ecosystems.

Is small-scale species richness limited by seed availability or microsite availability?

Abstract: To evaluate the relative roles of seed availability and competitive interactions in creating within-community patterns of species richness in unproductive grassland, we conducted a sowing experiment in a dry calcareous (alvar) grassland, where both the number of arriving seeds and the number of arriving species were approximately doubled compared to the natural seed rain. Also, in half of the plots, 36% of the vegetation and bryophyte cover was removed to simulate disturbance. Sowing significantly increased species richness and the number of seedlings in plots. Disturbance increased the number of seedlings but had no significant effect on species richness. In the first year, the highest number of seedlings was found in disturbed and sown plots. The dynamics of seedling numbers differed among species. Of the 15 sown species, seedlings of nine species were found in some plots. The number of seedlings of two species were not dependent on treatments, those of three species depended only on sowing, and for four species there was a significant positive interaction between sowing and disturbance. The establishment of sown species was not dependent on initial species richness or number of adult ramets in experimental plots. It was concluded that, though the behavior of individual species may differ, the local deficiency of seeds may be an important force generating small-scale community patterns of calcareous grasslands.

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

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Global pollinator declines: trends, impacts and drivers.

Abstract: Pollinators are a key component of global biodiversity, providing vital ecosystem services to crops and wild plants. There is clear evidence of recent declines in both wild and domesticated pollinators, and parallel declines in the plants that rely upon them. Here we describe the nature and extent of reported declines, and review the potential drivers of pollinator loss, including habitat loss and fragmentation, agrochemicals, pathogens, alien species, climate change and the interactions between them. Pollinator declines can result in loss of pollination services which have important negative ecological and economic impacts that could significantly affect the maintenance of wild plant diversity, wider ecosystem stability, crop production, food security and human welfare.

The unseen majority: Soil microbes as drivers of plant diversity and productivity in terrestrial ecosystems

Abstract: Microbes are the unseen majority in soil and comprise a large portion of lifes genetic diversity. Despite their abundance, the impact of soil microbes on ecosystem processes is still poorly understood. Here we explore the various roles that soil microbes play in terrestrial ecosystems with special emphasis on their contribution to plant productivity and diversity. Soil microbes are important regulators of plant productivity, especially in nutrient poor ecosystems where plant symbionts are responsible for the acquisition of limiting nutrients. Mycorrhizal fungi and nitrogenfixing bacteria are responsible for c. 5‐20% (grassland and savannah) to 80% (temperate and boreal forests) of all nitrogen, and up to 75% of phosphorus, that is acquired by plants annually. Free-living microbes also strongly regulate plant productivity, through the mineralization of, and competition for, nutrients that sustain plant productivity. Soil microbes, including microbial pathogens, are also important regulators of plant community dynamics and plant diversity, determining plant abundance and, in some cases, facilitating invasion by exotic plants. Conservative estimates suggest that c. 20 000 plant species are completely dependent on microbial symbionts for growth and survival pointing to the importance of soil microbes as regulators of plant species richness on Earth. Overall, this review shows that soil microbes must be considered as important drivers of plant diversity and productivity in terrestrial ecosystems.

Global effects of land use on local terrestrial biodiversity

Abstract: Human activities, especially conversion and degradation of habitats, are causing global biodiversity declines. How local ecological assemblages are responding is less clear--a concern given their importance for many ecosystem functions and services. We analysed a terrestrial assemblage database of unprecedented geographic and taxonomic coverage to quantify local biodiversity responses to land use and related changes. Here we show that in the worst-affected habitats, these pressures reduce within-sample species richness by an average of 76.5%, total abundance by 39.5% and rarefaction-based richness by 40.3%. We estimate that, globally, these pressures have already slightly reduced average within-sample richness (by 13.6%), total abundance (10.7%) and rarefaction-based richness (8.1%), with changes showing marked spatial variation. Rapid further losses are predicted under a business-as-usual land-use scenario; within-sample richness is projected to fall by a further 3.4% globally by 2100, with losses concentrated in biodiverse but economically poor countries. Strong mitigation can deliver much more positive biodiversity changes (up to a 1.9% average increase) that are less strongly related to countries' socioeconomic status.