Search

Plants influence numerous soil biotic factors that can alter the performance of later growing plants—defined as plant-soil feedback (PSF). Here, we investigate whether PSF effects are linked with the temporal changes in root exudate diversity and the rhizosphere microbiome of two common grassland species (Holcus lanatus and Jacobaea vulgaris). Both plant species were grown separately establishing conspecific and heterospecific soils. In the feedback phase, we determined plant biomass, measured root exudate composition, and characterised rhizosphere microbial communities weekly (eight time points). Over time, we found a strong negative conspecific PSF on J. vulgaris in its early growth phase which changed into a neutral PSF, whereas H. lanatus exhibited a more persistent negative PSF. Root exudate diversity increased considerably over time for both plant species. Rhizosphere microbial communities were distinct in conspecific and heterospecific soils and showed strong temporal patterns. Bacterial communities converged over time. Using path models, PSF effects could be linked to the temporal dynamics of root exudate diversity, whereby shifts in rhizosphere microbial diversity contributed to temporal variation in PSF to a lesser extent. Our results highlight the importance of root exudates and rhizosphere microbial communities in driving temporal changes in the strength of PSF effects.

Plants leave legacy effects in the soil they grow in, which can drive important vegetation processes, including productivity, community dynamics and species turnover. Plants at the same time also face continuous pressure posed by insect herbivores. Given the intimate interactions between plants and herbivores in ecosystems, plant identity and herbivory are likely to interactively shape soil legacies. However, the mechanisms that drive such legacy effects on future generations of plants and associated herbivores are little known. In a greenhouse study, we exposed 10 common grasses and non-leguminous forbs individually to insect herbivory by two closely related noctuid caterpillars, Mamestra brassicae and Trichoplusia ni (Lepidoptera: Noctuidae) or kept them free of herbivores. We then used the soil legacies created by these plant individuals to grow a plant community composed of all 10 plant species in each soil and exposed these plant communities to M. brassicae. We measured conditioning plant biomass, soil respiration and chemistry of the conditioned soils, as well as individual plant, plant community and herbivore biomass responses. At the end of the conditioning phase, soils with herbivore legacies had higher soil respiration, but only significantly so for M. brassicae. Herbivore legacies had minimal impacts on community productivity. However, path models reveal that herbivore-induced soil legacies affected responding herbivores through changes in plant community shoot: root ratios. Soil legacy effect patterns differed between functional groups. We found strong plant species and functional group-specific effects on soil respiration parameters, which in turn led to plant community shifts in grass: forb biomass ratios. Soil legacies were negative for the growth of plants of the same functional group. Synthesis. We show that insect herbivory, plant species and their functional groups, all incur soil microbial responses that lead to subtle (herbivory) or strong (p

Purpose: Insect herbivory affects plant growth, nutrient and secondary metabolite concentrations and litter quality. Changes to litter quality due to insect herbivory can alter decomposition, with knock on effects for plant growth mediated through the plant-litter-soil feedback pathway. Methods: Using a multi-phase glasshouse experiment, we tested how changes in shoot and root litter quality of fast- and slow-growing grass caused by insect herbivores affect the performance of response plants in the soil in which the litter decomposed. Results: We found that insect herbivory resulted in marginal changes to litter quality and did not affect growth when plants were grown with fast- versus slow-growing litter. Overall, presence of litter resulted in reduced root and shoot growth and this effect was significantly more negative in shoots versus roots. However, this effect was minimal, with a loss of c. 1.4% and 3.1% dry weight biomass in roots versus shoots, respectively. Further, shoot litter exposed to insect herbivory interacted with response plant identity to affect root growth. Conclusions: Our results suggest that whether litter originates from plant tissues exposed to insect herbivory or not and its interaction with fast- versus slow-growing grasses is of little importance, but species-specific responses to herbivory-conditioned litter can occur. Taken collectively, the overall role of the plant-litter-soil feedback pathway, as well as its interaction with insect herbivory, is unlikely to affect broader ecosystem processes in this system.

Global warming and precipitation extremes (drought or increased precipitation) strongly affect plant primary production and thereby terrestrial ecosystem functioning. Recent syntheses show that combined effects of warming and precipitation extremes on plant biomass are generally additive, while individual experiments often show interactive effects, indicating that combined effects are more negative or positive than expected based on the effects of single factors. Here, we examined whether variation in biomass responses to single and combined effects of warming and precipitation extremes can be explained by plant growth form and community type. We performed a meta-analysis of 37 studies, which experimentally crossed warming and precipitation treatments, to test whether biomass responses to combined effects of warming and precipitation extremes depended on plant woodiness and community type (monocultures versus mixtures). Our results confirmed that the effects of warming and precipitation extremes were overall additive. However, combined effects of warming and drought on above- and belowground biomass were less negative in woody- than in herbaceous plant systems and more negative in plant mixtures than in monocultures. We further show that drought effects on plant biomass were more negative in greenhouse- than in field studies, suggesting that greenhouse experiments may overstate drought effects in the field. Our results highlight the importance of plant system characteristics to better understand plant responses to climate change.

Global warming and precipitation extremes (drought or increased precipitation) strongly affect plant primary production and thereby terrestrial ecosystem functioning. Recent syntheses show that combined effects of warming and precipitation extremes on plant biomass are generally additive, while individual experiments often show interactive effects, indicating that combined effects are more negative or positive than expected based on the effects of single factors. Here, we examined whether variation in biomass responses to single and combined effects of warming and precipitation extremes can be explained by plant growth form and community type. We performed a meta-analysis of 37 studies, which experimentally crossed warming and precipitation treatments, to test whether biomass responses to combined effects of warming and precipitation extremes depended on plant woodiness and community type (monocultures versus mixtures). Our results confirmed that the effects of warming and precipitation extremes were overall additive. However, combined effects of warming and drought on above- and belowground biomass were less negative in woody- than in herbaceous plant systems and more negative in plant mixtures than in monocultures. We further show that drought effects on plant biomass were more negative in greenhouse- than in field studies, suggesting that greenhouse experiments may overstate drought effects in the field. Our results highlight the importance of plant system characteristics to better understand plant responses to climate change.

Global warming and precipitation extremes (drought or increased precipitation) strongly affect plant primary production and thereby terrestrial ecosystem functioning. Recent syntheses show that combined effects of warming and precipitation extremes on plant biomass are generally additive, while individual experiments often show interactive effects, indicating that combined effects are more negative or positive than expected based on the effects of single factors. Here, we examined whether variation in biomass responses to single and combined effects of warming and precipitation extremes can be explained by plant growth form and community type. We performed a meta-analysis of 37 studies, which experimentally crossed warming and precipitation treatments, to test whether biomass responses to combined effects of warming and precipitation extremes depended on plant woodiness and community type (monocultures versus mixtures). Our results confirmed that the effects of warming and precipitation extremes were overall additive. However, combined effects of warming and drought on above- and belowground biomass were less negative in woody- than in herbaceous plant systems and more negative in plant mixtures than in monocultures. We further show that drought effects on plant biomass were more negative in greenhouse, than in field studies, suggesting that greenhouse experiments may overstate drought effects in the field. Our results highlight the importance of plant system characteristics to better understand plant responses to climate change., Global warming and precipitation extremes (drought or increased precipitation) strongly affect plant primary production and thereby terrestrial ecosystem functioning. Recent syntheses show that combined effects of warming and precipitation extremes on plant biomass are generally additive, while individual experiments often show interactive effects, indicating that combined effects are more negative or positive than expected based on the effects of single factors. Here, we examined whether variation in biomass responses to single and combined effects of warming and precipitation extremes can be explained by plant growth form and community type. We performed a meta-analysis of 37 studies, which experimentally crossed warming and precipitation treatments, to test whether biomass responses to combined effects of warming and precipitation extremes depended on plant woodiness and community type (monocultures versus mixtures). Our results confirmed that the effects of warming and precipitation extremes were overall additive. However, combined effects of warming and drought on above- and belowground biomass were less negative in woody- than in herbaceous plant systems and more negative in plant mixtures than in monocultures. We further show that drought effects on plant biomass were more negative in greenhouse, than in field studies, suggesting that greenhouse experiments may overstate drought effects in the field. Our results highlight the importance of plant system characteristics to better understand plant responses to climate change.