Lauri Laanisto

The photosynthetic capacity in 35 ferns and fern allies: mesophyll CO2 diffusion as a key trait

Ferns and fern allies have low photosynthetic rates compared with seed plants. Their photosynthesis is thought to be limited principally by physical CO2 diffusion from the atmosphere to chloroplasts. The aim of this study was to understand the reasons for low photosynthesis in species of ferns and fern allies (Lycopodiopsida and Polypodiopsida). We performed a comprehensive assessment of the foliar gas-exchange and mesophyll structural traits involved in photosynthetic function for 35 species of ferns and fern allies. Additionally, the leaf economics spectrum (the interrelationships between photosynthetic capacity and leaf/frond traits such as leaf dry mass per unit area or nitrogen content) was tested. Low mesophyll conductance to CO2 was the main cause for low photosynthesis in ferns and fern allies, which, in turn, was associated with thick cell walls and reduced chloroplast distribution towards intercellular mesophyll air spaces. Generally, the leaf economics spectrum in ferns follows a trend similar to that in seed plants. Nevertheless, ferns and allies had less nitrogen per unit DW than seed plants (i.e. the same slope but a different intercept) and lower photosynthesis rates per leaf mass area and per unit of nitrogen.

Microfragmentation concept explains non-positive environmental heterogeneity–diversity relationships

Although recent studies have revealed that the relationship between diversity and environmental heterogeneity is not always positive, as classical niche theory predicts, scientists have had difficulty interpreting these results from an ecological perspective. We propose a new concept—microfragmentation—to explain how small-scale heterogeneity can have neutral or even negative effect on species diversity. We define microfragmentation as a community level process of splitting habitat into a more heterogeneous environment that can have non-positive effects on the diversity through habitat loss and subsequent isolation. We provide support for the microfragmentation concept with results from spatially explicit heterogeneity–diversity model simulations, in which varying sets of species (with different ratios of specialist and generalist species) were modeled at different levels of configurational heterogeneity (meaning that only the habitat structure was changed, not its composition). Our results indicate that environmental heterogeneity can affect community diversity in the same way as fragmentation at the landscape level. Although generalist species might not be seriously affected by microfragmentation, the persistence of specialist species can be seriously disturbed by small-scale patchiness. The microfragmentation concept provides new insight into community level diversity dynamics and can influence conservation and management strategies.

Extremely thick cell walls and low mesophyll conductance: welcome to the world of ancient living!

Highlight Low mesophyll conductance was the most important limiter of photosynthesis in the majority of evolutionarily old species and resulted from thick cell walls and low exposed chloroplast area.

Shedding light on shade: ecological perspectives of understorey plant life

Shade, in ecological sense, is not merely a lack of light, but a multi-faceted phenomenon that creates new and complex settings for community and ecosystem dynamics. Tolerating shade therefore affects plants’ ability to cope with other stressors, and also shape its interactions with surrounding organisms. The aim of this broad review was to map our current knowledge about how shade affects plants, plant communities and ecosystems – to gather together knowledge of what we know, but also to point out what we do not yet know. This review covers the following topics: the nature of shade, and ecological and physiological complexities related to growing under a canopy; plants’ capability of tolerating other stress factors while living under a shade – resource trade-offs and polytolerance of abiotic stress; ontogenetic effects of shade tolerance; coexistence patterns under the canopy – how shade determines the forest structure and diversity; shade-induced abiotic dynamics in understorey vegetation, including changing patterns of irradiance, temperature and humidity under the canopy; shade-driven plant–plant and plant–animal interactions – how shade mediates facilitation and stress, and how it creates differentiated environment for different herbivores and pollinators, including the role of volatile organic compounds. We also discuss the ways how vegetation in understorey environments will be affected by climate change, as shade might play a significant role in mitigating negative effects of climate change. Our review shows that living under a shade affects biotic and abiotic stress tolerance of plants, it also influences the outcomes of both symbiotic and competitive plant–plant and plant–animal interactions in a complex and dynamic manner. The current knowledge of shade-related mechanisms is rather ample, however there is much room for progress in integrating different implications of the multifaceted nature of shade into consistent and integral understanding how communities and ecosystems function.

A compendium of temperature responses of Rubisco kinetic traits: variability among and within photosynthetic groups and impacts on photosynthesis modeling

Highlight A synthesis of existing data reveals differences in the temperature responses of Rubisco kinetics among higher plants, with important consequences for photosynthesis modeling.

Comment on "Worldwide evidence of a unimodal relationship between productivity and plant species richness".

Fraser et al. (Reports, 17 July 2015, p. 302) report that a hump-backed model describes the worldwide relationship between productivity and plant species richness in grassland communities. We reanalyze their data from a larger-scale perspective, using local species pool. This influences richness far more strongly than productivity, and, when this is taken into account, the hump-backed richness-productivity relationship disappears.

Fertilising semi‐natural grasslands may cause long‐term negative effects on both biodiversity and ecosystem stability

Recently, the use of nutrientrich residues from bioenergy production (digestate) and intensive husbandry (slurry) for fertilising traditionally managed grasslands has gained increased attention (e.g. Duffková, Hejcman, & Libichová, 2015; Duffková & Libichová, 2013; Hensgen, Bühle, & Wachendorf, 2016; Kováčiková, Vargová, & Jančová, 2013). Hensgen et al. (2016) used lowdose nutrient applications (i.e. 25–54 kg N ha−1 year−1, 2–5 kg P ha−1 year−1 and 20–51 kg K ha−1 year−1 for 5 years) in seminatural grasslands to maintain productivity and claimed that these applications did not result in a loss of species richness during the 5year study. Similar shortterm experiments by Duffková and Libichová (2013) and Duffková et al. (2015) came to similar conclusions: lowdose cattle slurry application (i.e. 0–240 kg N ha−1 year−1 and 0–240 kg N ha−1 year−1, 0–40 kg P ha−1 year−1 and 0–180 kg K ha−1 year−1 for 6 years, respectively) increases the herbage yield without affecting the diversity in a speciesrich grassland. The use or recommendation of new intensive management strategies in seminatural grasslands is complicated. Such complexity is typical in ecosystems with high biodiversity and conservation values (e.g. Veen, Jefferson, de Smidt, & Van der Straaten, 2009). Generally, fertilisation decreases plant diversity and changes the species composition (Bobbink, Hornung, & Roelofs, 1998; Borer et al., 2014; De Schrijver Received: 18 September 2017 | Accepted: 22 January 2018 DOI: 10.1111/1365-2664.13129

Global database of plants with root-symbiotic nitrogen fixation: NodDB

Root symbiotic associations with Nfixing bacteria and mycorrhizal fungi are important evolutionary adaptations of plants to compete for nutrients. Nitrogenfixing plant–bacterial associations are widely distributed across all terrestrial biomes and continents apart from Antarctica. Nodulated plants form important components of plant communities, especially in Nlimited early successional ecosystems, riparian habitats and tropical savanna and shrubland biomes (Cleveland et al., 1999). In early successional habitats, Nfixing plants and their root symbiotic microbes contribute to soil development and facilitate recruitment of other plant species and consumers (Walker, Clarkson, Silvester, & Clarkson, 2003). The global symbiotic biological N fixation amounts roughly to 45 Mt annually, which is the main contributor to natural terrestrial N sources (Vitousek, Menge, Reed, & Cleveland, 2013). Nitrogenfixing mutualistic relationships between plant roots and bacteria have evolved multiple times in both partners (Rai, Söderbäck, & Bergman, 2000; Santi, Bogusz, & Franche, 2013; Werner, Cornwell, Sprent, Kattge, & Kiers, 2014; Doyle, 2016). The differentiated forms of associations occur as root (or additionally stem) nodules, but in multiple instances plants host Nfixing bacteria in undifferentiated leaf, stem or root tissues (Vessey, Pawlowski, & Bergman, 2005; Santi et al., 2013). Rhizobiaceae (αproteobacteria) and Burkholderiaceae (βproteobacteria) are the most well known Nfixing bacterial groups that nodulate mostly legumes (Fabaceae; Sprent, Ardley, & James, 2017). A small genus Parasponia (Cannabaceae) has evolved independently symbiotic associations with Rhizobiaceae (Trinick, 1980). In addition, rhizobial root nodules have been reported in three zygophyllaceous genera, Tribulus, Fagonia and Zygophyllum (Mostafa & Mahmoud, 1951), but Received: 20 November 2017 | Accepted: 12 February 2018 DOI: 10.1111/jvs.12627

Change in Species Composition during 55 Years: A Re-Sampling Study of Species-Rich Meadows in Estonia

We revisited 44 remnants of historically species-rich meadows in two regions in Estonia in order to evaluate their importance in harbouring meadow species. We used Ellenbergs indicator values (EIV), diversity and evenness indices and species functional traits (CSR strategy, height, clonal mobility, ramet life span) to analyse changes in vegetation and habitat conditions. Habitat loss resulted in similar amount of loss of both meadow specialists and generalists. Only meadow specialists were negatively affected by cessation of management in meadows unmown for more than 10 years in South Estonia. The largest change was an increase in Ellenbergs indicator value (EIV) of nutrients. We found a significant decline in typical meadow species (e.g. Briza media, Primula farinosa) and an increase in strong competitors. Species in the remnant meadows tended to have increased clonal mobility and shortened ramet life span, indicating fertile habitats. The ecological conditions became unfavourable for meadow species which prefer high illumination and unfertile conditions. The remnant meadows have largely lost the floristic diversity of the original nutrient-poor or moist species-rich meadows.