Pesticide effects on the abundance of springtails and mites in field mesocosms at an agricultural site

The use of pesticides to protect crops often affects non-target organisms vital to ecosystem functioning. A functional soil mesofauna is important for decomposition and nutrient cycling processes in agricultural soils, which generally have low biodiversity. To assess pesticide effects on natural soil communities we enclosed intact soil cores in situ in an agricultural field in 5 cm wide mesocosms. We used two types of mesh lids on the mesocosms, allowing or preventing migration of mesofauna. The mesocosms were exposed to the insecticide imidacloprid (0, 0.1, 1, and 10 mg/kg dry soil) and left in the field for 20 days. Overall, regardless of lid type, mesocosm enclosure did not affect springtail or mite abundances during the experiment when compared with undisturbed soil. Imidacloprid exposure reduced the abundance of both surface- and soil-living springtails in a concentration-dependent manner, by 65-90% at the two highest concentrations, and 21-23% at 0.1 mg/kg, a concentration found in some agricultural soils after pesticide application. Surface-living springtails were more affected by imidacloprid exposure than soil-living ones. In contrast, neither predatory nor saprotrophic mites showed imidacloprid-dependent changes in abundance, concurring with previous findings indicating that mites are generally less sensitive to neonicotinoids than other soil organisms. The possibility to migrate did not affect the springtail or mite abundance responses to imidacloprid. We show that under realistic exposure concentrations in the field, soil arthropod community composition and abundance can be substantially altered in an organism-dependent manner, thus affecting the soil community diversity.

The Resilience of Polar Collembola (Springtails) in a Changing Climate

Assessing the resilience of polar biota to climate change is essential for predicting the effects of changing environmental conditions for ecosystems. Collembola are abundant in terrestrial polar ecosystems and are integral to food-webs and soil nutrient cycling. Using available literature, we consider resistance (genetic diversity; behavioural avoidance and physiological tolerances; biotic interactions) and recovery potential for polar Collembola. Polar Collembola have high levels of genetic diversity, considerable capacity for behavioural avoidance, wide thermal tolerance ranges, physiological plasticity, generalist-opportunistic feeding habits and broad ecological niches. The biggest threats to the ongoing resistance of polar Collembola are increasing levels of dispersal (gene flow), increased mean and extreme temperatures, drought, changing biotic interactions, and the arrival and spread of invasive species. If resistance capacities are insufficient, numerous studies have highlighted that while some species can recover from disturbances quickly, complete community-level recovery is exceedingly slow. Species dwelling deeper in the soil profile may be less able to resist climate change and may not recover in ecologically realistic timescales given the current rate of climate change. Ultimately, diverse communities are more likely to have species or populations that are able to resist or recover from disturbances. While much of the Arctic has comparatively high levels of diversity and phenotypic plasticity; areas of Antarctica have extremely low levels of diversity and are potentially much more vulnerable to climate change.

What Are the Most Important Factors Influencing Springtail Tetrodontophora bielanensis?

Simple Summary

Springtails (Collembola) are organisms which mainly inhabit soil and litter layers but may account for around 25% of the canopy fauna. They can be also found in dead wood, which provides nutrients for these detritivores. The springtail, Tetrodontophora bielanensis, dwells in the litter and upper soil layers. In our research, we were focused on the environmental factors influencing this springtail in forests at the landscape and site level. We found that the springtail was positively influenced by the presence of Norway spruce (Picea abies) and with greater abundance in the south-eastern part of Krkonoše (Czech Republic). The negative influence of bark coverage, the presence of fungi, and the positive influence of an increasing circumference of tree was observed at the site level.

Abstract

The springtail, Tetrodontophora bielanensis, dwells in the litter and upper soil layers. This arthropod mainly inhabits humid litter and soil and prefers a cold climate. We determined the main factors influencing this springtail in forests at the landscape level in Krkonoše and site level in Orlické hory in the Czech Republic. We used passive trunk-tree traps. These traps are highly effective for sampling flightless fauna. We used 128 traps in Krkonoše and 17 traps in Orlické hory. The springtail was significantly positively influenced by the presence of Norway spruce (Picea abies) at the landscape level. Springtails’ abundance was, furthermore, influenced by the spatial distribution of the sampling sites. The negative influence of bark coverage and the presence of fungi, and positive influence of an increasing dimension of trees were significant at the site level. We argue for a more diversified management of mountainous forests with respect to forest history. This appears to be also important for mountainous forests in protected areas.

Corridor quality affects net movement, size of dispersers, and population growth in experimental microcosms

Corridors are expected to increase species dispersal in fragmented habitats. However, it remains unclear how the quality of corridors influences the dispersal process, and how it interacts with corridor length and width. Here we investigate these factors using a small-scale laboratory system where we track the dispersal of the model organism Collembola Folsomia candida. Using this system, we study the effects of corridor length, width, and quality on the probability of dispersal, net movement, body size of dispersers, and the rate of change in population size after colonization. We show that corridor quality positively affected dispersal probability, net movement, and the rate of change in population size in colonised patches. Moreover, corridor quality significantly affected the size of dispersers, with only larger individuals dispersing through poor quality corridors. The length and width of corridors affected both the rate at which populations increased in colonised patches and the net number of individuals which dispersed, suggesting that these physical properties may be important in maintaining the flow of individuals in space. Our results thus suggest that corridor quality can have an important role in determining not only the probability of dispersal occurs but also the phenotypes of the individuals which disperse, with concomitant effects on the net movement of individuals and the rate of change in population size in the colonised patches.

Differences in collembola species assemblages (Arthropoda) between spoil tips and surrounding environments are dependent on vegetation development

Spoil tip production is one of the most extreme means of soil destruction, replacing the native soil with a coarse substrate. In this paper, we aim to determine the colonization of soil biota in new substrates, using collembola assemblages as an indicator. In Northern France, we sampled collembola communities in 11 coal mine spoil tips and their surroundings divided in four stages of vegetation development: bare soil, meadow, shrub and tree covers. We demonstrated that collembola assemblages of spoil tips were different from those observed in the surrounding native soil. Collembola communities on bare soil were characterized by pioneer (based on the Indval index) or exotic species (new in Northern France). However, homogenization occurred with development of vegetation cover. Indeed, our data showed no difference in springtail diversity between spoil tips and their corresponding environments regarding the tree vegetation cover. Using the Indval method, we defined pioneer, colonizing, opportunist or stenoecious species as a function of substrate affinities. Using the same method, we defined specialists, elective, preferring or indifferent species as a function of vegetation cover affinities, showing similarities with previously published surveys. Hence, our results were obtained by a focused analysis of species and their particularity. Finally, we discussed the interest in and the complementarity between the species analysis approach and the methodology dealing with functional traits and of its importance in the decision process of restoration and/or conservation of nature.