Cold stress and freezing tolerance negatively affect the fitness of Arabidopsis thaliana accessions under field and controlled conditions

Main conclusion Higher acclimated freezing tolerance improved winter survival, but reduced reproductive fitness of Arabidopsis thaliana accessions under field and controlled conditions. Abstract Low temperature is one of the most important abiotic factors influencing plant fitness and geographical distribution. In addition, cold stress is known to influence crop yield and is therefore of great economic importance. Increased freezing tolerance can be acquired by the process of cold acclimation, but this may be associated with a fitness cost. To assess the influence of cold stress on the fitness of plants, long-term field trials over 5 years were performed with six natural accessions of Arabidopsis thaliana ranging from very tolerant to very sensitive to freezing. Fitness parameters, as seed yield and 1000 seed mass, were measured and correlation analyses with temperature and freezing tolerance data performed. The results were compared with fitness parameters from controlled chamber experiments over 3 years with application of cold priming and triggering conditions. Winter survival and seed yield per plant were positively correlated with temperature in field experiments. In addition, winter survival and 1000 seed mass were correlated with the cold-acclimated freezing tolerance of the selected Arabidopsis accessions. The results provide strong evidence for a trade-off between higher freezing tolerance and reproductive fitness in A. thaliana, which might have ecological impacts in the context of global warming.

Dredging fundamentally reshapes the ecological significance of 3D terrain features for fish in estuarine seascapes

Context Landscape modification alters the condition of ecosystems and the structure of terrain, with widespread impacts on biodiversity and ecosystem functioning. Seafloor dredging impacts a diversity of flora and fauna in many coastal landscapes, and these processes also transform three-dimensional terrain features. The potential ecological significance of these terrain changes in urban seascapes has, however, not been investigated. Objectives We examined the effects of terrain variation on fish assemblages in 29 estuaries in eastern Australia, and tested whether dredging changes how fish associate with terrain features. Methods We surveyed fish assemblages with baited remote underwater video stations and quantified terrain variation with nine complementary metrics (e.g. depth, aspect, curvature, slope, roughness), extracted from bathymetry maps created with multi-beam sonar. Results Fish diversity and abundance were strongly linked to seafloor terrain in both natural and dredged estuaries, and were highest in shallow waters and near features with high curvature. Dredging, however, significantly altered the terrain of dredged estuaries and transformed the significance of terrain features for fish assemblages. Abundance and diversity switched from being correlated with lower roughness and steeper slopes in natural estuaries to being linked to features with higher roughness and gentler slopes in dredged estuaries. Conclusions Contrasting fish-terrain relationships highlight previously unrecognised ecological impacts of dredging, but indicate that plasticity in terrain use might be characteristic of assemblages in urban landscapes. Incorporating terrain features into spatial conservation planning might help to improve management outcomes, but we suggest that different approaches would be needed in natural and modified landscapes.

Find New RoadsTM? A Systematic Review on the Impacts of Off-Road Vehicle Activity on Soil, Vegetation, and Wildlife

The global use of off-road vehicles (ORVs) in natural environments has accelerated rapidly over the last few decades, resulting in significant social and environmental consequences. As the demand, use, and promotion of light-duty ORVs like all-terrain vehicles (ATVs), motorcycles, four-wheel drive trucks and sport utility vehicles (SUVs) increases in remote wilderness, the landscape is becoming fragmented into disorganized and destructive networks of trails and roads. Substantial ecological impacts to a wide range of ecosystem structures and functions will likely result from ORV activity. Applying a global systematic review, we examine 105 publications about plant, soil, and wildlife responses to ORV traffic in different habitats to help guide the direction of future research, monitoring programs, and mitigation efforts. Most studies investigated impacts to animals, followed by soils, then vegetative responses. Soil studies primarily focused on physical impacts to the soil (i.e., compaction, erosion, rut depth), but some studies suggest that soil chemical and biological properties may also be impacted by ORV traffic. The literature on plant responses to ORV activities primarily explored vegetation loss, although impacts on the plant community were also investigated. Animal studies investigated impacts of ORV use on invertebrates, mammals, birds, and to a lesser extent reptiles/amphibians, including population-level, community-level, and behavioral responses. Overall, research on environmental impacts of ORV traffic is biased to coastal and desert ecosystems in the northern hemisphere (primarily in the US), often does not address mechanisms that may produce ecological impacts (e.g., intensity of vehicular disturbance and ecosystem- or species-specific sensitivity to ORV activities), and frequently focused on short-term responses. More research is needed to understand the mechanisms that cause the different responses of soil, plant, and animals to ORVs over the long-term in a broad range of ecosystems to support real-time management and conservation efforts.

Greenhouse Gas Forcing a Necessary Causation for Marine Heatwaves Over the Northeast Pacific Warming Pool

Over the last decade, the northeast Pacific (NP) experienced strong marine heatwaves (MHWs) that produced devastating marine ecological impacts and received major societal concerns. Here, we assess the link between the well-mixed greenhouse gas (GHG) forcing and the occurrence probabilities of the duration and intensity of the NP MHWs. To begin with, we apply attribution technique on the SST time series, and detect a region of systematically and externally-forced SST increase -- the long-term warming pool -- co-located with the past notably Blob-like SST anomalies. The anthropogenic signal has recently emerged from the natural variability of SST over the warming pool, which we attribute primarily to increased GHG concentrations, with anthropogenic aerosols playing a secondary role. With extreme event attribution technique, we further show that GHG forcing is a necessary, but not a sufficient, causation for the multi-year persistent MHW events in the current climate, such as that happened in 2019/2020 over the warming pool. However, the occurrence of the 2019/2020 MHW was extremely unlikely in the absence of GHG forcing. Thus, as GHG emissions continue to firmly rise, it is very likely that GHG forcings will become a sufficient cause for events of the magnitude of the 2019/2020 record event.

Diagnostic classification of flash drought events reveals distinct classes of forcings and impacts

Recent years have seen growing appreciation that rapidly intensifying “flash droughts” are significant climate hazards with major economic and ecological impacts. This has motivated efforts to inventory, monitor, and forecast flash drought events. Here we consider the question of whether the term “flash drought” comprises multiple distinct classes of event, which would imply that understanding and forecasting flash droughts might require more than one framework. To do this, we first extend and evaluate a soil moisture volatility-based flash drought definition that we introduced in previous work and use it to inventory the onset dates and severity of flash droughts across the Contiguous United States (CONUS) for the period 1979-2018. Using this inventory, we examine meteorological and land surface conditions associated with flash drought onset and recovery. These same meteorological and land surface conditions are then used to classify the flash droughts based on precursor conditions that may represent predictable drivers of the event. We find that distinct classes of flash drought can be diagnosed in the event inventory. Specifically, we describe three classes of flash drought: “dry and demanding” events for which antecedent evaporative demand is high and soil moisture is low, “evaporative” events with more modest antecedent evaporative demand and soil moisture anomalies, but positive antecedent evaporative anomalies, and “stealth” flash droughts, which are different from the other two classes in that precursor meteorological anomalies are modest relative to the other classes. The three classes exhibit somewhat different geographic and seasonal distributions. We conclude that soil moisture “flash droughts” are indeed a composite of distinct types of rapidly intensifying droughts, and that flash drought analyses and forecasts would benefit from approaches that recognize the existence of multiple phenomenological pathways.

Effect-based water quality assessment of rivers receiving discharges from legacy mines by using acute and chronic bioassays with two cladoceran species

Information about the ecotoxicological impacts of surface waters that receive discharges from legacy mines is valuable to infer the ecological impacts on natural environment for managing mine discharges. In this study, we investigated behavioural and reproductive responses of two cladoceran species Ceriodaphnia dubia and Daphnia magna to water samples collected from metal-contaminated and reference rivers near legacy mines in Japan. The toxicity identification evaluation (TIE) of water samples that caused D. magna immobility was conducted to evaluate the key metals causing acute toxicity. The results of our water quality assessment performed using two cladoceran species demonstrated modest to significant adverse effects on their behaviour and reproduction, suggesting the potential for ecotoxicological impacts on natural populations and communities at several contaminated sites that received mine drainage. The results of TIE of water samples that caused D. magna immobility indicated likely contributions of Zn and Cu. These results imply that effect-based water quality assessments such as ours can provide direct and unique evidence of the ecotoxicological impacts of metals in river waters, which will be useful for better understanding and predicting the ecological effects of these metals in the natural environment.