No detrimental effects of delayed mowing or uncut grass refuges on plant and bryophyte community structure and phytomass production in low-intensity hay meadows

Distance decay 2.0 - A global synthesis of taxonomic and functional turnover in ecological communities

AIM

Understanding the variation in community composition and species abundances (i.e., β-diversity) is at the heart of community ecology. A common approach to examine β-diversity is to evaluate directional variation in community composition by measuring the decay in the similarity among pairs of communities along spatial or environmental distance. We provide the first global synthesis of taxonomic and functional distance decay along spatial and environmental distance by analysing 148 datasets comprising different types of organisms and environments.

LOCATION

Global.

TIME PERIOD

1990 to present.

MAJOR TAXA STUDIED

From diatoms to mammals.

METHOD

We measured the strength of the decay using ranked Mantel tests (Mantel r) and the rate of distance decay as the slope of an exponential fit using generalized linear models. We used null models to test whether functional similarity decays faster or slower than expected given the taxonomic decay along the spatial and environmental distance. We also unveiled the factors driving the rate of decay across the datasets, including latitude, spatial extent, realm and organismal features.

RESULTS

Taxonomic distance decay was stronger than functional distance decay along both spatial and environmental distance. Functional distance decay was random given the taxonomic distance decay. The rate of taxonomic and functional spatial distance decay was fastest in the datasets from mid-latitudes. Overall, datasets covering larger spatial extents showed a lower rate of decay along spatial distance but a higher rate of decay along environmental distance. Marine ecosystems had the slowest rate of decay along environmental distances.

MAIN CONCLUSIONS

In general, taxonomic distance decay is a useful tool for biogeographical research because it reflects dispersal-related factors in addition to species responses to climatic and environmental variables. Moreover, functional distance decay might be a cost-effective option for investigating community changes in heterogeneous environments.

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.

Biennial Mowing Maintains the Biomass and Functional Diversity of Semi-Arid Grassland

Understanding the functional diversity relationship between biomass and plants is a key issue in biodiversity–ecosystem functionality and the utility of grassland. We conducted a five-year mowing experiment to examine the effects of the mowing frequency on biomass, plant species, and functional diversity of a natural plant community in a semiarid region of Inner Mongolia. A secondary objective was to test whether unmowed refuge areas within plots would mitigate the disturbance effect of mowing. The result showed that mowing disturbance reduced biomass by the greatest amount with mowing once every year (M1) and the least with M2. The biomass composition of M2 consisted of a greater mass of perennial species than in the other mowing treatments but was equivalent to the control (CK). However, mowing disturbances increased the plant species richness and M2 had the largest number of species. The community-weighted means (CWM) indices indicated that M2 produced the least detrimental effects on the grassland. Retaining unmowed refuge areas appeared to be ineffective in promoting beneficial community traits under M1 mowing regimes. Based on our results, we recommend that the semi-arid grassland be mowed every other year in order to optimize sustainable production.

A global database for metacommunity ecology, integrating species, traits, environment and space

The use of functional information in the form of species traits plays an important role in explaining biodiversity patterns and responses to environmental changes. Although relationships between species composition, their traits, and the environment have been extensively studied on a case-by-case basis, results are variable, and it remains unclear how generalizable these relationships are across ecosystems, taxa and spatial scales. To address this gap, we collated 80 datasets from trait-based studies into a global database for metaCommunity Ecology: Species, Traits, Environment and Space; "CESTES". Each dataset includes four matrices: species community abundances or presences/absences across multiple sites, species trait information, environmental variables and spatial coordinates of the sampling sites. The CESTES database is a live database: it will be maintained and expanded in the future as new datasets become available. By its harmonized structure, and the diversity of ecosystem types, taxonomic groups, and spatial scales it covers, the CESTES database provides an important opportunity for synthetic trait-based research in community ecology.

Larval and phenological traits predict insect community response to mowing regime manipulations

For the restoration of biodiversity in agricultural grasslands, it is essential to understand how management acts as an ecological filter on the resident species. Mowing constitutes such a filter: only species that possess functional traits enabling them to withstand its consequences can persist in the community. We investigated how the timing of mowing modulates this filtering effect for insects. We predicted that two traits drive species responses. Species with larval development within the meadow vegetation will suffer more from mowing than species whose larvae develop in or on the ground, or outside the meadows, while species with a later phenology should benefit from later mowing. We conducted a five-year experiment, replicated at 12 sites across the Swiss lowlands, applying three different mowing regimes to low-intensity hay meadows: (1) first cut of the year not earlier than 15 June (control regime); (2) the first cut delayed until 15 July; and (3) leaving an uncut grass refuge on 10-20% of the meadow area (after earliest first cut on 15 June). Before the first cut in years 4 or 5, we sampled larvae of Lepidoptera and sawflies, and adults of moths, parasitoid wasps, wild bees, hoverflies, ground beetles, and rove beetles. Overall, before the first cut of the year, abundances of species with vegetation-dwelling larvae were higher in meadows with delayed mowing or an uncut grass refuge, with some taxon-specific variation. In contrast, species whose larval development is independent of the meadow vegetation showed no differences in abundance between mowing regimes. Species richness did not differ among regimes. For species with vegetation-dwelling larvae, a fourth-corner analysis showed an association between early phenology and the control regime. No associations were found for the other functional groups. Our results show that slight modifications of mowing regimes, easily implementable in agri-environmental policy schemes, can boost invertebrate abundance, potentially benefitting insectivorous vertebrates.

Direct and indirect effects of land use on bryophytes in grasslands

Land-use intensification is the major threat for biodiversity in agricultural grasslands, and fertilization has been suggested as the most important driver. A common explanation for the decline of bryophyte diversity with higher land-use intensity is an indirect negative effect via the increase in vascular plant productivity, which reduces light levels for bryophytes. However, direct negative effects of land-use intensification may also be important. Here, we disentangle direct and vascular plant biomass mediated indirect effects of land use on bryophytes. We analyzed two complementary datasets from agricultural grasslands, an observational study across 144 differently managed grasslands in Germany and an experimental fertilization and irrigation study of eleven grasslands in the Swiss Alps. We found that bryophyte richness and cover strongly declined with land-use intensity and in particular with fertilization. However, structural equation modelling revealed that although both direct and indirect effects were important, the direct negative effect of fertilization was even stronger than the indirect effect mediated by increased plant biomass. Thus, our results challenge the widespread view that the negative effects of fertilization are mostly indirect and mediated via increased light competition with vascular plants. Our study shows that land use intensification reduces bryophyte diversity through several different mechanisms. Therefore, only low-intensity management with limited fertilizer inputs will allow the maintenance of bryophyte-rich grasslands.