Activation of seminal root primordia during wheat domestication reveals underlying mechanisms of plant resilience

Seminal roots constitute the initial wheat root system and provide the main route for water absorption during early stages of development. Seminal root number (SRN) varies among species. However, the mechanisms through which SRN is controlled and in turn contribute to environmental adaptation are poorly understood. Here, we show that SRN increased upon wheat domestication from 3 to 5 due to the activation of 2 root primordia that are suppressed in wild wheat, a trait controlled by loci expressed in the germinating embryo. Suppression of root primordia did not limit water uptake, indicating that 3 seminal roots is adequate to maintain growth during seedling development. The persistence of roots at their primordial state promoted seedling recovery from water stress through reactivation of suppressed primordia upon rehydration. Our findings suggest that under well‐watered conditions, SRN is not a limiting factor, and excessive number of roots may be costly and maladaptive. Following water stress, lack of substantial root system suppresses growth and rapid recovery of the root system is essential for seedling recovery. This study underscores SRN as key adaptive trait that was reshaped upon domestication. The maintenance of roots at their primordial state during seedling development may be regarded as seedling protective mechanism against water stress.     

Integrating trait‐based empirical and modeling research to improve ecological restoration

A global ecological restoration agenda has led to ambitious programs in environmental policy to mitigate declines in biodiversity and ecosystem services. Current restoration programs can incompletely return desired ecosystem service levels, while resilience of restored ecosystems to future threats is unknown. It is therefore essential to advance understanding and better utilize knowledge from ecological literature in restoration approaches. We identified an incomplete linkage between global change ecology, ecosystem function research, and restoration ecology. This gap impedes a full understanding of the interactive effects of changing environmental factors on the long‐term provision of ecosystem functions and a quantification of trade‐offs and synergies among multiple services. Approaches that account for the effects of multiple changing factors on the composition of plant traits and their direct and indirect impact on the provision of ecosystem functions and services can close this gap. However, studies on this multilayered relationship are currently missing. We therefore propose an integrated restoration agenda complementing trait‐based empirical studies with simulation modeling. We introduce an ongoing case study to demonstrate how this framework could allow systematic assessment of the impacts of interacting environmental factors on long‐term service provisioning. Our proposed agenda will benefit restoration programs by suggesting plant species compositions with specific traits that maximize the supply of multiple ecosystem services in the long term. Once the suggested compositions have been implemented in actual restoration projects, these assemblages should be monitored to assess whether they are resilient as well as to improve model parameterization. Additionally, the integration of empirical and simulation modeling research can improve global outcomes by raising the awareness of which restoration goals can be achieved, due to the quantification of trade‐offs and synergies among ecosystem services under a wide range of environmental conditions.     

Recovery of riverine vegetation after experimental disturbance: a field test of the patch dynamics concept

The Patch Dynamics Concept predicts different recovery patterns of communities after disturbance according to the spatial and temporal heterogeneity of the habitat. The aim of this study was to test the predictions arising from the Patch Dynamics Concept on the recovery of macrophyte communities after an experimental disturbance. The test was based on the comparison of the vegetation recovery in three stations located on former channels of the Rhône River, France, differing by their temporal heterogeneity, which was estimated by the frequency of flood scouring. In each station the experimental disturbance was set up by uprooting the aquatic plants in three experimental sets comprising four 1 m²-plots. The aquatic plants were surveyed in these sets as well as in their reference sets from July to November 1991.As predicted, the most frequently disturbed station recovered its species richness (19 species) and its vegetation cover in less than two months. The biological traits of the species occurring in this station are considered as r-strategies. The species colonizing the experimental sets were not necessarily present on the sets before the disturbance, but occurred regularly on other sites station. The rapidity of the community recovery demonstrates the high resilience of this ecosystem. According to the unpredictable character of its recolonization, the macrophyte community of this station could be said to be founder controlled with competitive lottery for establishment.The station with intermediate temporal heterogeneity was overgrown by some r-selected species but the community recolonization was predictable and this station had intermediate resilience. Its species richness was low (6 species).The less frequently disturbed station presented low resilience with a slow recovery of its community (more than 5 months); the species richness (4 species) and the traits of some species were related to K-strategies while others were related to r-strategies. The macrophyte community of this station could be said to be dominance controlled.Different patterns of recovery of the macrophyte communities of former channels of the Rhône River could be depicted according to their temporal heterogeneity; these patterns were consistent with the hypotheses arising from the Patch Dynamics Concept. However, the competitive lottery appeared to be limited at the scale of our experiment.     

Perturbation and abrupt shift in trophic control of biodiversity and productivity

Ecology is founded on the view that ecosystem properties like biodiversity and productivity change smoothly with changing environmental conditions. However, emerging theory predicts that environmental change may cause abrupt shifts to alternate states. In many ecosystems, top predators play a pivotal role in controlling plant productivity and diversity. Yet it remains uncertain if altering this control shifts systems to alternate states. I report on a test of the hypothesis that loss of predator control of ecosystem function causes abrupt state changes in diversity and productivity. In this meadow ecosystem, predators enhance plant diversity by causing a highly productive, competitively dominant plant species to be suppressed by herbivores. Experimental predator removal caused rapid proliferation of the competitively dominant plant. Moreover, temporally staggered predator reintroductions failed to restore the ecosystem. This loss of resilience confirmed that the ecosystem crossed a critical threshold and entrained into an alternate state.