Relevance In Ecology Of Environmental Driver Rate Of Change: A Cross-Scale Approach

In the context of accelerating changes and the massive challenges those changes represent for the ecosystems, temporal ecology has emerged. Some work already exists that describes the importance of temporalities from the point of view of communities (i.g., describing temporal dynamics of communities, the timing of biological events in phenology, co-occurrence and coupling study of synchrony). How- ever, investigating the role of temporal dynamics of environmental drivers’ importance for biological responses remains scarce. The dy- namic of the temporal driver is the temporal context of the temporal- ity of communities, and it defines their time environment. Chapter 1 classifies the varieties of the temporality of drivers, shows how those temporalities are relevant, and proposes a systematic framework for their study. One particular aspect of the temporal dynamics of environmental drivers we focused on is the rate of change. This particular aspect has received growing attention in the last five years as it has been pointed out that it could be determinant in the passing of thresholds between stable states. We conducted a review and synthesis of the existing ex- perimental and theoretical work on rates of change of environmental drivers across levels of complexity in biology (i.e. organism, popula- tion, community, ecosystem). We did not limit ourselves to ecology because we believe a reductionist approach is needed to understand how the rate of change impacts the ecosystem since the response orig- inates at the individual level. Chapter 2 results from our work: rate of change matters for a variety of driver effects and shows no homoge- nous effects between magnitude for one diver, between drivers, and across levels of organizational complexity. Finally, we put into practice the framework we develop in chap- ter 2 to study the rate of change in a series of three experiments. We wanted to demonstrate that rates of temperature change affect growth and show in practice how to study this effect. We used a fungal com- munity collection of 30 strains. The rate of temperature affected fun- gal growth for moderate heat stress but did not affect thermal limits; hence, the temperature rate of change has a non-uniform effect on our tested system. We also showed a non-uniform effect across the strains, indicating strain-specific diversity in responses to temperature rate of changes. Finally, we showed that the rate of temperature change im- pacts competition outcomes. Our work demonstrates how the rate of change can be relevant in ecology and shows how it can be studied

Basic principles of temporal dynamics

All ecological disciplines consider temporal dynamics, although relevant concepts have been developed almost independently. We here introduce basic principles of temporal dynamics in ecology. We figured out essential features that describe temporal dynamics by finding similarities among about 60 ecological concepts and theories. We found that considering the hierarchically nested structure of complexity in temporal patterns (i.e. hierarchical complexity) can well describe the fundamental nature of temporal dynamics by expressing which patterns are observed at each scale. Across all ecological levels, driver–response relationships can be temporally variant and dependent on both short- and long-term past conditions. The framework can help with designing experiments, improving predictive power of statistics, and enhancing communications among ecological disciplines

Rate of environmental change across scales in ecology

The rate of change (RoC) of environmental drivers matters: biotic and abiotic components respond differently when faced with a fast or slow change in their environment. This phenomenon occurs across spatial scales and thus levels of ecological organization. We investigated the RoC of environmental drivers in the ecological literature and examined publication trends across ecological levels, including prevalent types of evidence and drivers. Research interest in environmental driver RoC has increased over time (particularly in the last decade), however, the amount of research and type of studies were not equally distributed across levels of organization and different subfields of ecology use temporal terminology (e.g. 'abrupt' and 'gradual') differently, making it difficult to compare studies. At the level of individual organisms, evidence indicates that responses and underlying mechanisms are different when environmental driver treatments are applied at different rates, thus we propose including a time dimension into reaction norms. There is much less experimental evidence at higher levels of ecological organization (i.e. population, community, ecosystem), although theoretical work at the population level indicates the importance of RoC for evolutionary responses. We identified very few studies at the community and ecosystem levels, although existing evidence indicates that driver RoC is important at these scales and potentially could be particularly important for some processes, such as community stability and cascade effects. We recommend shifting from a categorical (e.g. abruptversusgradual) to a quantitative and continuous (e.g. degrees C/h) RoC framework and explicit reporting of RoC parameters, including magnitude, duration and start and end points to ease cross-scale synthesis and alleviate ambiguity. Understanding how driver RoC affects individuals, populations, communities and ecosystems, and furthermore how these effects can feed back between levels is critical to making improved predictions about ecological responses to global change drivers. The application of a unified quantitative RoC framework for ecological studies investigating environmental driver RoC will both allow cross-scale synthesis to be accomplished more easily and has the potential for the generation of novel hypotheses

Myristate and the ecology of AM fungi : significance, opportunities, applications and challenges

A recent study by Sugiura and coworkers reported the nonsymbiotic growth and spore production of an arbuscular mycorrhizal (AM) fungus, Rhizophagus irregularis, when the fungus received an external supply of certain fatty acids, myristates (C:14). This discovery follows the insight that AM fungi receive fatty acids from their hosts when in symbiosis. If this result holds up and can be repeated under nonsterile conditions and with a broader range of fungi, it has numerous consequences for our understanding of AM fungal ecology, from the level of the fungus, at the plant community level, and to functional consequences in ecosystems. In addition, myristate may open up several avenues from a more applied perspective, including improved fungal culture and supplementation of AM fungi or inoculum in the field. We here map these potential opportunities, and additionally offer thoughts on potential risks of this potentially new technology. Lastly, we discuss the specific research challenges that need to be overcome to come to an understanding of the potential role of myristate in AM ecology

In situ fate of mineral N in the tree-soil-microorganism system before and after budburst in 20-year-old Quercus petraea (Matt.) Liebl.

Aims: We simultaneously quantified the fate of soil absorbed mineral nitrogen in different tree compartments along with nitrogen immobilization by microorganisms during spring in 20-year-old oak trees. Methods: A soil-applied(15)N solution was traced in situ into the fine roots, medium roots, xylem, phloem, branches, leaves, extractable soil, and microbial biomass before and after budburst, until LAI maximum was reached. Results: During the three weeks following the labeling, around half of the(15)N applied was incorporated into the microbial biomass while the leafless trees absorbed less than 10% of the(15)N. Before and after budburst, the microbial compartment was the main pool of(15)N, and yet the soil-absorbed(15)N still significantly contributed to the leaf nitrogen pool at budburst. This contribution in leaves sharply increased in the days following budburst. Conclusion: The potential competition for mineral nitrogen between trees and the soil microbial biomass is strong during spring. The dependence of the leaf nitrogen pool to internal or external stocks of nitrogen at budburst could be conditioned by environmental conditions

Myristate and the ecology of AM fungi: significance, opportunities, applications and challenges

A recent study by Sugiura and coworkers reported the nonsymbiotic growth and spore production of an arbuscular mycorrhizal (AM) fungus, Rhizophagus irregularis, when the fungus received an external supply of certain fatty acids, myristates (C:14). This discovery follows the insight that AM fungi receive fatty acids from their hosts when in symbiosis. If this result holds up and can be repeated under nonsterile conditions and with a broader range of fungi, it has numerous consequences for our understanding of AM fungal ecology, from the level of the fungus, at the plant community level, and to functional consequences in ecosystems. In addition, myristate may open up several avenues from a more applied perspective, including improved fungal culture and supplementation of AM fungi or inoculum in the field. We here map these potential opportunities, and additionally offer thoughts on potential risks of this potentially new technology. Lastly, we discuss the specific research challenges that need to be overcome to come to an understanding of the potential role of myristate in AM ecology