Browsing by Person "Walter, Julia"

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Effects of land-use intensity on functional community composition and nutrient dynamics in grassland
(2024) Walter, Julia; Thumm, Ulrich; Buchmann, Carsten M.; Heinonen-Tanski, Helvi
Land-use intensity drives productivity and ecosystem functions in grassland. The effects of long-term land-use intensification on plant functional community composition and its direct and indirect linkages to processes of nutrient cycling are largely unknown. We manipulated mowing frequency and nitrogen inputs in an experiment in temperate grassland over ten years. We assessed changes in species composition and calculated functional diversity (FDis) and community weighted mean (CWM) traits of specific leaf area (SLA), leaf dry matter content (LDMC) and leaf and root nitrogen of the plant community, using species-specific trait values derived from databases. We assessed above- and belowground decomposition and soil respiration. Plant diversity strongly decreased with increasing land-use intensity. CWM leaf nitrogen and SLA decreased, while CWM LDMC increased with land-use intensification, which could be linked to an increased proportion of graminoid species. Belowground processes were largely unaffected by land-use intensity. Land use affected aboveground litter composition directly and indirectly via community composition. Mowing frequency, and not a land-use index combining mowing frequency and fertilization, explained most of the variation in litter decomposition. Our results show that land-use intensification not only reduces plant diversity, but that these changes also affect nutrient dynamics.
The role of maternal environment and dispersal ability in plants' transgenerational plasticity
(2023) Lukić, Nataša; Zhu, Jinlei; Schurr, Frank M.; Walter, Julia
Transgenerational effects enable the transmission of environmental cues from parents to offspring. Adaptive maternal effects are expected to evolve if the maternal (or parental) environment contains information about the environment experienced by offspring. This correlation between maternal and offspring environments should be strongest in plant species with reduced dispersal ability. However, studies relating dispersal ability to the strength of maternal effects are rare. This study aimed to explore whether and how the dispersal distance of species and individuals affects offspring plant performance. Using seven common European plant species, we conducted a multi‐year common garden experiment exposing maternal plants to three different water conditions (mesic, drought and waterlogging). At the end of the season in the first year, seed heads were collected from the lower and upper parts of each mother plant and used for dispersal distance calculation. Offspring coming from the maternal lower and upper parts were exposed to the same water treatments as mothers. Contrasting our hypothesis, we found that maternal water experience and species' dispersal abilities did not influence offspring performance (plant aboveground, belowground, reproductive and dead biomass). We did not detect maternal effects, meaning that offspring plants with the same water conditions as their mothers had the same fitness as offspring with different water conditions. However, opposite to our expectations, the longer dispersal distance of individual seeds ensured a stronger maternal effect when exposed to the same water stress as their mothers. Consequently, a stressful environment would select for long‐distance dispersal.
Seed dispersal by wind decreases when plants are water‐stressed, potentially counteracting species coexistence and niche evolution
(2021) Zhu, Jinlei; Lukić, Nataša; Rajtschan, Verena; Walter, Julia; Schurr, Frank M.
Hydrology is a major environmental factor determining plant fitness, and hydrological niche segregation (HNS) has been widely used to explain species coexistence. Nevertheless, the distribution of plant species along hydrological gradients does not only depend on their hydrological niches but also depend on their seed dispersal, with dispersal either weakening or reinforcing the effects of HNS on coexistence. However, it is poorly understood how seed dispersal responds to hydrological conditions. To close this gap, we conducted a common‐garden experiment exposing five wind‐dispersed plant species (Bellis perennis, Chenopodium album, Crepis sancta, Hypochaeris glabra, and Hypochaeris radicata) to different hydrological conditions. We quantified the effects of hydrological conditions on seed production and dispersal traits, and simulated seed dispersal distances with a mechanistic dispersal model. We found species‐specific responses of seed production, seed dispersal traits, and predicted dispersal distances to hydrological conditions. Despite these species‐specific responses, there was a general positive relationship between seed production and dispersal distance: Plants growing in favorable hydrological conditions not only produce more seeds but also disperse them over longer distances. This arises mostly because plants growing in favorable environments grow taller and thus disperse their seeds over longer distances. We postulate that the positive relationship between seed production and dispersal may reduce the concentration of each species to the environments favorable for it, thus counteracting species coexistence. Moreover, the resulting asymmetrical gene flow from favorable to stressful habitats may slow down the microevolution of hydrological niches, causing evolutionary niche conservatism. Accounting for context‐dependent seed dispersal should thus improve ecological and evolutionary models for the spatial dynamics of plant populations and communities.