Taimekoosluse ja arbuskulaarmükoriisse seenekoosluse dünaamika rohumaadel muutuva maakasutuse tingimustes

Väitekirja elektrooniline versioon ei sisalda publikatsiooneEnam kui kaks kolmandikku maismaaökosüsteemidest on inimtegevuse poolt tugevasti mõjutatud. Viimaste hulka kuuluvad ka Euroopa pool-looduslikud rohumaad, mis paistavad silma oma taimekoosluste suure mitmekesisusega. Need rohumaad on kujunenud kestva ja mõõduka niitmise ja/või karjatamise tulemusel ning nende säilitamiseks on vaja samasuguse maakasutuse jätkumist. Kuna pool-looduslike rohumaade pindala on drastiliselt vähenenud, on looduskaitseliste eesmärkide täitmiseks tihtipeale vajalik ka nende rohumaade taimekoosluste taastamine. See omakorda nõuab detailset arusaama rohumaade elurikkust mõjutavatest teguritest. Madalakasvulised väheviljakate rohumaade taimeliigid on valguslembesed ja neil on väiksed, tuule või kariloomade kaasabil levivad seemned. Kinnikasvanud rohumaadel ei ole selliste taimeliikide jaoks piisavalt valgust ning puuduvad sobilikud tingimused seemneleviks. Lisaks võib niiduliikide populatsioonide seisundit halvendada ning taastumist takistada sümbiontsete mullamikroobide puudumine. Viimaste hulka kuuluvad ka arbuskulaarmükoriissed (AM) seened. Antud doktoritöö tulemused kinnitasid, et lisaks seemnelevi soodustamisele ja valgustingimuste parandamisele on kinnikasvanud rohumaade taastamisel tähtis roll ka AM seentel. Tüüpilises avatud rohumaa taimekoosluses on tunduvalt rohkem mükoriisa olemasolust oluliselt sõltuvaid taimeliike kui kinnikasvanud rohumaa taimekoosluses. Seetõttu võib AM seente olemasolu või puudumine rohumaade taastamisprotsessi oluliselt mõjutada.Human activities have modified about two thirds of all terrestrial ecosystems. European semi-natural grasslands are among the most diverse ecosystems globally; at the same time, they are among the ecosystems most affected by human activities. Such grasslands develop under extensive land use practices – notably grazing and mowing – and land use change can dramatically decrease the extent and quality of such habitats, posing a considerable threat to grassland biodiversity. Many restoration efforts have been undertaken to mitigate against habitat loss, but re-establishing grassland specialist plants often challenges restoration practitioners. This may be because many typical grassland plant species have small seeds adapted to dispersal by wind or grazing animals. As such, a lack of grazing animals or dense vegetation around restored grassland patches might hinder seed dispersal between grassland patches, and thus maintenance of vital meta-populations. It is also possible that restoration sites lack certain soil organisms found in intact habitats, and their absence impairs the establishment of plants that rely on them (e.g. symbiotic fungi, such as arbuscular mycorrhizal (AM) fungi). The aim of this doctoral thesis was to assess the relevance of these factors for successful grassland restoration. The results of the thesis confirm the importance of facilitating plant species dispersal between grassland patches by re-opening the vegetation to create dispersal corridors and by re-introducing continuous grazing management, with grazing animals able to move between grassland patches. Moreover, the results suggest that a lack of suitable AM fungi in the soil of severely altered and isolated grassland patches might hamper natural re-establishment of typical grassland vegetation. Coordinated re-introduction of target plant and AM fungal communities could increase restoration succession in such cases

Rhizosphere fungal community assembly varied across functional guilds in a temperate forest

Background Rhizosphere fungi play an important role in plant community dynamics and biogeochemical cycling. While the drivers of fungal community assembly have been studied in varied ecosystems, it is still unclear how these processes function for rhizosphere soil fungi in temperate forests. Furthermore, it is unknown whether the relative contributions of important determinants remain consistent or vary across fungal ecological guilds. This study used high-throughput next-generation sequencing to characterize the fungal communities of 247 rhizosphere soil samples from 19 tree species in a temperate forest within Northeast China. We aimed to investigate how three important determinants in temperate forests (host tree species, neighbouring plant communities, and edaphic properties) influence the community assembly of fungal functional guilds in the rhizosphere soil of trees. Results We found that host tree species contributed more to plant pathogens’ community composition than ectomycorrhizal fungi, and plant pathogens consistently showed higher host specialization than ectomycorrhizal fungi. Saprotrophs also showed high host specialization, which was mediated by the tree species’ effect on rhizosphere soil pH. Although neighboring plant communities contributed remarkably to richness of all fungal guilds, this effect on fungal composition varied across functional guilds, with stronger effect for biotrophic guilds (plant pathogens and ectomycorrhizal fungi) than for non-biotrophic guild (saprotrophs). Neighboring plant communities shaped the ectomycorrhizal community composition strongly in all samples regardless of host trees’ mycorrhizal type, whereas edaphic properties were the most important drivers for this guild in samples from only ectomycorrhizal-associated trees. Edaphic properties played an important role in shaping ectomycorrhizal and saprotrophic fungal compositions, indicating the importance of edaphic properties on the fungal functional guilds associated with the absorption and decomposition of nutrients. Conclusions These results demonstrated that rhizosphere soil fungal community assembly determinants varied across fungal guilds, reflecting their different ecological functions in temperate forest ecosystems.This work was supported by the National Key Research and Development Program of China (2022YFF1300501), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant XDB31030000), the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (Grant ZDBS-LY-DQC019)

Acceptance of near-natural greenspace management relates to ecological and socio-cultural assigned values among European urbanites

Grasslands are widespread elements of urban greenspace providing recreational, psychological and aesthetic benefits to city residents. Two urban grassland types of contrasting management dominate urban greenspaces: frequently mown, species-poor short-cut lawns and less intensively managed, near-natural tall-grass meadows. The higher conservation value of tall-grass meadows makes management interventions such as converting short-cut lawns into tall-grass meadows a promising tool for urban biodiversity conservation. The societal success of such interventions, however, depends on identifying the values urban residents assign to different types of urban grasslands, and how these values translate to attitudes towards greenspace management. Using 2027 questionnaires across 19 European cities, we identify the assigned values that correlate with people's personal greenspace use and their preferences for different types of urban grasslands to determine how these values relate to the agreement with a scenario of converting 50 of their cities� short-cut lawns into tall-grass meadows. We found that most people assigned nature-related values, such as wildness, to tall-grass meadows and utility-related values, such as recreation, to short-cut lawns. Positive value associations of wildness and species richness with tall-grass meadows, and social and nature-related greenspace activities, positively correlated with agreeing to convert short-cut lawns into tall-grass meadows. Conversely, disapproval of lawn conversion correlated with positive value associations of cleanliness and recreation potential with short-cut lawns. Here, people using greenspaces for nature-related activities were outstandingly positive about lawn conversion. The results show that the plurality of values assigned to different types of urban grasslands should be considered in urban greenspace planning. For example, tall-grass meadows could be managed to also accommodate the values associated with short-cut lawns, such as tidiness and recreation potential, to support their societal acceptance

Tiny Fungi in the Soil Are Like Medicine for Nature

Like humans, plant and animal species have a specific type of place, called an ecosystem, where they prefer to live. If the ecosystem changes too much, some species will disappear, much the same way people avoid living in the desert because it is too hot and dry. Humans modify many ecosystems, sometimes so severely that almost no plants or animals can live there anymore. To help damaged ecosystems recover, we often start by planting trees or other plants. Biologists found that mycorrhizal fungi, tiny fungi living in the soil and inside plant roots, could speed up ecosystem recovery by making plants grow back faster and stronger. In this article, we describe how the recovery of ecosystems can be enhanced by mycorrhizal fungi, and when mycorrhizal fungi are especially helpful

How can mycorrhizal symbiosis mediate multiple abiotic stresses in woody plants?

Mycorrhizal symbiosis is an ancient association of plants and mycorrhizal fungi central to woody plant evolution and expansion. This symbiosis has established a complex exchange of services between plants and mycorrhizal fungi that ultimately helps plants thrive in extreme abiotic conditions and build resistance against lack of nutrients and water, pathogens, herbivores, or pollutants. Here, we briefly comment on the roles of mycorrhizal symbiosis as modulators of the responses of woody plants to multiple abiotic stress factors typical to ongoing global change. We comment on the most studied factors, i.e. drought, extreme temperatures, nutrient and light deficiency. There is a general lack of understanding of the interaction among stress factors and their combined effects on woody plants, their symbiotic interaction with mycorrhizal fungi and their impact on ecosystem processes. As a first step, identifying and ranking the severity of stress factors and situations/locations where multiple stress factors co-occur could guide initial expectations and hypotheses to comprehend the mycorrhizal benefits to woody species tolerance under multifactorial stress combinations. We finally highlight topical areas that require more information and research.CGB and YM have been funded by the Estonian Ministry of Education and Research (PRG1065) and an ERC incentive grant from the University of Tartu to CGB (PLTOMARENG70)

Special Issue: Urban ecosystems: potentials, challenges, and solutions

ISSN:1439-1791ISSN:1618-008

Special issue: Urban ecosystems: potentials, challenges, and solutions

n conclusion, the work highlighted above needs to be seen in the context of strengthening urban ecological research during the last decades (Barot et al., 2019). This underlines the importance of not only studying, but also actively shaping cities by exploiting their ecological potentials, despite any limitations and barriers. This issue demonstrates that creating, conserving, or restoring biodiverse urban ecosystems is possible, though it requires careful urban greenspace planning, design, management, maintenance, as well as information campaigns and restoration programs. Supporting and conserving urban nature will result in ecological improvements in close proximity to the majority of the earth's population, directly providing health and well-being benefits through contact with high-quality nature and indirectly by enhancing biodiversity and ecosystem service provisioning in and beyond urban areas. Thus, the importance of urban ecology for the successful development of our societies must be emphasised. We hope this Special Issue will help propagate and encourage the planning of more liveable cities that support both biodiversity and humans in the future

Arbuscular mycorrhizal fungal community composition determines the competitive response of two grassland forbs

We performed a greenhouse experiment to assess how differences in AM fungal community composition affect competitive response of grassland plant species. We used a full factorial design to determine how inoculation with natural AM fungal communities from different habitats in Western Estonia affects the growth response of two grassland forbs (Leontodon hispidus L., Plantago lanceolata L.) to competition with a dominant grass (Festuca rubra L.). We used AM fungal inocula that were known to differ in AM fungal diversity and composition: more diverse AM fungal communities from open grasslands and less diverse AM fungal communities from former grassland densely overgrown by pines (young pine forest). The presence of AM fungi balanced competition between forb and grass species, by enhancing competitive response of the forbs. The magnitude of this effect was dependent on forb species identity and on the origin of the AM fungal inoculum in the soil. The grassland inoculum enhanced the competitive response of the forb species more effectively than the forest inoculum, but inoculum-specific competitive responses varied according to the habitat preference of the forb species. Our findings provide evidence that composition and diversity of natural AM fungal communities, as well as co-adaptation of plant hosts and AM-fungal communities to local habitat conditions, can determine plant-plant interactions and thus ultimately influence plant community structure in nature