• Energy Research

Abstract Maternal effects (i.e. trans‐generational plasticity) and soil legacies generated by drought and plant diversity can affect plant performance and alter nutrient cycling and plant community dynamics. However, the relative importance and combined effects of these factors on plant growth dynamics remain poorly understood. We used soil and seeds from an existing plant diversity and drought manipulation field experiment in temperate grassland to test maternal, soil drought and diversity legacy effects, and their interactions, on offspring plant performance of two grassland species (Alopecurus pratensis and Holcus lanatus) under contrasting glasshouse conditions. Our results showed that drought soil legacy effects eclipsed maternal effects on plant biomass. Drought soil legacy effects were attributed to changes in both abiotic (i.e. nutrient availability) and biotic soil properties (i.e. microbial carbon and enzyme activity), as well as plant root and shoot atom 15N excess. Further, plant tissue nutrient concentrations and soil microbial C:N responses to drought legacies varied between the two plant species and soils from high and low plant diversity treatments. However, these diversity effects did not affect plant root or shoot biomass. These findings demonstrate that while maternal effects resulting from drought occur in grasslands, their impacts on plant performance are likely minor relative to drought legacy effects on soil abiotic and biotic properties. This suggests that soil drought legacy effects could become increasingly important drivers of plant community dynamics and ecosystem functioning as extreme weather events become more frequent and intense with climate change. A plain language summary is available for this article.

Grazing affects grasslands worldwide. However, the global patterns and general mechanisms of how grazing affects plant reproductive traits are poorly understood, especially in the context of different climates and grazing duration. We conducted a meta-analysis of 114 independent grazing studies worldwide that measured plant reproductive traits in grasslands. The results showed that the number of tillers of plant increased under grazing. Grazing did not affect the number of reproductive branches of forbs, but significantly reduced the number of reproductive branches of grasses. Grazing increased the number of vegetative branches of all plants and reduced the proportion of reproductive branches. Grazing significantly reduced the number of flowers in forbs. Seed yield in the two plant functional groups was reduced compared with no-grazing. Under grazing, the sexual reproduction of grasses decreased much more substantially than that of forbs. This may be due to biomass allocation pattern of grasses under grazing (i.e., belowground versus aboveground). Under grazing, plants tended to adopt rapid, low-input asexual reproduction rather than long-term, high-risk sexual reproduction. This study represents the first large-scale evaluation of plant reproductive trait responses under grazing and demonstrates that grazing inhibits sexual reproduction and promotes asexual reproduction. The effect of grazing on plant sexual reproduction was influenced by grazing intensity, mean annual precipitation, and grazing duration. These results will assist in the development of sustainable grazing management strategies to improve the balance between human welfare and grassland ecosystem health.

There is a need for accurate predictions of ecosystem carbon (C) and water fluxes in field conditions. Previous research has shown that ecosystem properties can be predicted from community abundance-weighted means (CWM) of plant functional traits and measures of trait variability within a community (FDvar). The capacity for traits to predict carbon (C) and water fluxes, and the seasonal dependency of these trait-function relationships has not been fully explored. Here we measured daytime C and water fluxes over four seasons in grasslands of a range of successional ages in southern England. In a model selection procedure, we related these fluxes to environmental covariates and plant biomass measures before adding CWM and FDvar plant trait measures that were scaled up from measures of individual plants grown in greenhouse conditions. Models describing fluxes in periods of low biological activity contained few predictors, which were usually abiotic factors. In more biologically active periods, models contained more predictors, including plant trait measures. Field-based plant biomass measures were generally better predictors of fluxes than CWM and FDvar traits. However, when these measures were used in combination traits accounted for additional variation. Where traits were significant predictors their identity often reflected seasonal vegetation dynamics. These results suggest that database derived trait measures can improve the prediction of ecosystem C and water fluxes. Controlled studies and those involving more detailed flux measurements are required to validate and explore these findings, a worthwhile effort given the potential for using simple vegetation measures to help predict landscape-scale fluxes.

This file contains data in De Long et al. 2019 “Drought soil legacy overrides maternal effects on plant growth”. These data are the seed data collected on the two target species, Alopecurus pratensis and Holcus lanatus.

This file contains data in De Long et al. 2019 “Drought soil legacy overrides maternal effects on plant growth”. These data are the field data collected on soil moisture.

Plant-soil feedbacks (PSFs) describe the effect of a plant species on soil properties, which affect the performance of future generations. Here we test the hypothesis that drought alters PSFs by reducing plant-microbe associations and nutrient uptake. We chose two grassland forb species, previously shown to respond differently to soil conditioning and drought, to test our hypothesis. We conditioned unsterilised grassland soil with one generation of each species, and left a third soil unconditioned. We grew a second generation consisting of each combination of plant species, soil, and drought in a full factorial design, and measured soil microbial community and nutrient availability. Scabiosa columbaria displayed negative PSF (smaller plants) under non-droughted conditions, but neutral under drought, suggesting that drought disrupts plant-soil interactions and can advantage the plant. Photosynthetic efficiency of S. columbaria was reduced under drought, but recovered on rewetting regardless of soil conditioning, indicating that PSFs do not impede resilience of this species. Sanguisorba minor showed positive PSFs (larger plants), probably due to an increase in soil N in conspecific soil, but neutral PSF under drought. PSF neutralisation appeared to occur through drought-induced change in the soil microbial community for this species. When S. minor was planted in conspecific soil, photosynthetic efficiency declined to almost zero, with no recovery following rewetting. We attributed this to increased demand for water through higher demand for nutrients with positive PSF. Here we show that drought neutralises PSFs of two grassland forbs, which could have implications for plant communities under climate change.

Unprecedented climate change, pollutants and habitat alterations are causing abiotic stress across all plants and animals. Global increases in temperature, as well as decreases in pH in the ocean, have already caused microbiome dysbiosis in a range of species, and previously commensal microbes have turned pathogenic in response to extreme environmental conditions. This will have far-reaching consequences for host survival and associated ecosystem functions. However, host microbiomes may actually be the key to buffering these unprecedented environmental changes. The host microbiome contains massive genetic potential, and their vast numbers, high turnover, wide metabolic scope and short generation times may afford opportunities for faster acclimatisation and adaptation. Examples of this already exist, although responses are likely to be highly context-dependent. It is becoming increasingly clear that preservation of the microbiome is likely to be the key to maintaining healthy ecosystems in an uncertain future. However, there are still large knowledge gaps in almost every area, which need to be urgently addressed so we can apply conservation efforts in a judicious manner.