Effects of fertilization and irrigation on vascular plant species richness, functional composition and yield in mountain grasslands

Mid- and long-term responses of land snail communities to the intensification of mountain hay meadows management

Background

Species-rich semi-natural grasslands are impacted by the severe land-use changes that are affecting mountain regions, compromising their high biodiversity value. In particular, sprinkler irrigation and increased fertilisation stimulate vegetation growth, modifying and homogenising habitat conditions for ground-dwelling invertebrates. Among them, land snails have been largely understudied despite their commonness and vulnerability to small-scale habitat alteration. This study investigated the mid- and long-term responses of land snail communities to management intensification of montane and subalpine hay meadows. Mid-term effects were studied using a randomised block design experiment, mimicking an intensification gradient with different levels of irrigation and fertilisation applied during 5 years. Long-term effects were examined relying on an observational approach that consisted in comparing snail communities in meadows managed intensively for > 20 years with those from the 5-year experimental module.

Results

We show that management intensification initially boosts snail densities, but erodes species richness by − 35% in intensively-managed meadows in the long term. Contrary to our expectations, drought-tolerant (xerophilous) snails benefitted from grassland intensification, whereas mesophilous species accounted for most species losses due to intensification in the long run, indicating that the latter may be especially sensitive to the hostile microclimate conditions abruptly prevailing in a meadow after mowing. Soil pH was also a principal determinant of land snail occurrence, with almost no specimen recorded in acidic meadows (pH < 5.5), while plant diversity favoured overall snail abundance.

Conclusions

Despite the fact that xerophilous snails appear tolerant to management intensification, we found that several drought-sensitive species are lost in the long term. We conclude that the preservation of species-rich land snail communities in mountain hay meadows requires the conservation and restoration of low-input grasslands on basic soils for preventing further species losses of gastropod fauna.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-022-01972-4.

Drought, nitrogen deposition and arthropod herbivory modify plant establishment dynamics after soil disturbance

Global change projections predict more recurrent and intense drought coupled with more frequent soil disturbance events and increased levels of N deposition related to intensive land-use. How these abiotic drivers interact with each other and with biotic drivers in determining plant community dynamics is still unclear. Our study aimed to disentangle the roles of biotic and abiotic drivers in plant natural succession after soil disturbance. We carried out a factorial field experiment in which we performed soil disturbance in two seasons and manipulated drought, N deposition and herbivory. After each disturbance event, we monitored plant establishment dynamics. The species composition of plant communities established after disturbance was different in the early and late season trial probably due to different phenology of species from the seed bank. Depending on the timing of disturbance, plant communities responded differently to drought and N. In particular, seedling emergence and growth appeared sensitive to water stress only in the late season trial. Irrespective of the other treatments, arthropod herbivores increased the number of plant species established after soil disturbance. N generally had a negligible effect on plant community dynamics. We only observed positive effects of N on plant biomass in in the late season trial when there was a high water availability. Under future global change, we expect drought to affect plant establishment after soil disturbance by interacting with biotic and abiotic drivers. In particular, we showed that overlooked drivers such as timing of soil disturbance and arthropod herbivory will play an important role in shaping novel plant communities. Our results stress the critical need to adopt a multiple factor approach when assessing global change impacts on plant community diversity, composition and recovery ability.

Nutrients recovery from fresh liquid manure through an airlift reactor to mitigate the greenhouse gas emissions of open anaerobic lagoons

Open anaerobic lagoons are widely used for liquid manure storage and treatment, with excess greenhouse gas (GHG) and odor emissions. In this study, liquid manure was valorized through hybrid nitrogen and phosphorous recovery as value-added products using an airlift reactor. Also, the organic load of liquid manure was reduced before discharging into anaerobic lagoons, which simultaneously mitigated GHG emissions. The results showed that 14.5% of total nitrogen (TN) was recovered as ammonium sulfate, while 38.8% of TN and 79.3% of total phosphorus (TP) were recovered as phosphorus-rich sludge. After the pre-treatment in the reactor, the odor could be controlled effectively due to a 94.2% decrease in total VFAs. In addition, 59.0% of COD was removed, which decreased the theoretical modeled GHG emissions by 51.7% compared to the traditional direct discharging. The application is promising for upgrading anaerobic lagoons of liquid manure.

Direct and Indirect Effects of Management Intensity and Environmental Factors on the Functional Diversity of Lichens in Central European Forests

Using 642 forest plots from three regions in Germany, we analyzed the direct and indirect effects of forest management intensity and of environmental variables on lichen functional diversity (FDis). Environmental stand variables were affected by management intensity and acted as an environmental filter: summing direct and indirect effects resulted in a negative total effect of conifer cover on FDis, and a positive total effect of deadwood cover and standing tree biomass. Management intensity had a direct positive effect on FDis, which was compensated by an indirect negative effect via reduced standing tree biomass and lichen species richness, resulting in a negative total effect on FDis and the FDis of adaptation-related traits (FDisAd). This indicates environmental filtering of management and stronger niche partitioning at a lower intensity. In contrast, management intensity had a positive total effect on the FDis of reproduction-, dispersal- and establishment-related traits (FDisRe), mainly because of the direct negative effect of species richness, indicating functional over-redundancy, i.e., most species cluster into a few over-represented functional entities. Our findings have important implications for forest management: high lichen functional diversity can be conserved by promoting old, site-typical deciduous forests with a high richness of woody species and large deadwood quantity.