Diversity responses to climatic factors in plant communities are well understood from experiments, but less known in natural conditions due to the rarity of appropriate long-term observational data. In this paper, we use long-term transect data sampled annually in three natural grasslands of different species pools, soils, landscape contexts and land use histories. Analyzing these specific belt transect data of contiguous small sampling units enabled us to explore scale dependence and spatial synchrony of diversity patterns within and among sites. The 14-year study period covered several droughts, including one extreme event between 2011 and 2012. We demonstrated that all natural grasslands responded to droughts by considerable fluctuations of diversity, but, overall, they remained stable. The plant functional group of annuals showed high resilience at all sites, while perennials were resistant to droughts. Our results were robust to changing spatial scales of observations, and we also demonstrated that within-site spatial synchrony could be used as a sensitive indicator of external climatic effects. We propose the broad application of high-resolution belt transects for powerful and adaptive vegetation monitoring in the future.

Quantifying within-community variability and understanding the related assembly rules are important in developing and assessing grassland restoration. Beta diversity has great potential, revealing mechanisms behind community-level changes in succession. Here, we introduce two simple beta diversity indices: Microhabitat Diversity is the Shannon diversity of patches formed by the locally dominant species, and Multiplet Diversity is the Shannon diversity of subordinate species richness categories detected at a fine scale. Using null models, we tested the biotic filtering effects of dominants on the distribution of subordinates. Based on long-term vegetation monitoring data, we tested the utility of these models in grassland restoration. Sites sown with seed mixture and developing spontaneously were compared and used as test data for exploring the proposed indices. Microhabitat Diversity was larger at spontaneously developing sites, and its local maxima reflected reorganization in the mosaic structure of the community. Species richness categories with zero or one subordinate species were typical in sown grassland, while small 5 cm × 5 cm microsites where 2, 3, or 4 subordinate species co-occured were more frequent in spontaneous succession. Contrary to expectation, a slight convergence of beta diversity measures was revealed after 15 years of succession between passive and active restorations. Microhabitat Diversity and Multiplet Diversity are simple indices that complement existing methods and provide new insights into grassland restoration.

Dominant species form species-specific fine-scale vegetation matrices in grasslands that regulate community dynamics, diversity and ecosystem functioning. The structure of these dynamic microscale landscapes was analyzed and compared between primary and secondary plant communities. We explored fine-scale monitoring data along permanent transects over seven consecutive years. Spatial and temporal patterns of dominant grass species (Festuca valesiaca, Alopecurus pratensis and Poa angustifolia) were analyzed using information theory models. These matrix-forming species showed high spatiotemporal variability in all grasslands. However, consistent differences were found between primary and secondary grasslands in the spatial and temporal organization of the vegetation matrix. Alopecurus pratensis and Poa angustifolia had coarse-scale patchiness with stronger aggregation in secondary grasslands. The spatial patterns of Festuca valesiaca were nearly random in both types of grasslands. Strong associations were observed among the spatial patterns of each species across years, with a stronger dependence in secondary grasslands. In contrast, the rate of fine-scale dynamics was higher in primary grasslands. The complexity of microhabitats within the matrix was higher in primary grasslands, often involving two to three dominant species, while, in secondary grasslands, patches formed by a single dominant species were more frequent. In the spatial variability of small-scale subordinate species richness, significant, temporally consistent differences were found. Higher variability in secondary grasslands suggests stronger and more spatially variable microhabitat filtering. We recommend that grassland management and restoration practices be guided by preliminary information on the spatial organization of primary grasslands. Enhancing the complexity of the matrix formed by dominant species can further improve the condition of secondary grasslands.

Spatial heterogeneity of species distributions modulates local interactions and dynamics, playing a key role in the development of diversity and ecosystem functioning during secondary succession. Here, we tested the cycling heterogeneity hypothesis, which predicts fluctuating spatial beta diversity, i.e., alternating periods of high and low heterogeneity during succession, driven by the changes in the abundance of dominant species. We analyzed long-term monitoring data collected annually along 52 m long permanent transects over 15 years in abandoned fields. Recovery of grassland vegetation was fast due to the humus-rich chernozem soil, the rich species pool, and the fast colonization of native grassland species from adjacent natural meadow steppe. Heterogeneity was quantified by spatial beta diversity as the mean pairwise dissimilarity among sampling units. Incidence-based (Jaccard) and abundance-based (Bray–Curtis) indices were used. We found large temporal fluctuations in spatial heterogeneity, with amplitudes reaching 80–100% of the total beta diversity range across the successional gradient. Two major beta diversity peaks were identified: maximum heterogeneity occurred during transitions between successional phases, whereas periods of minimum heterogeneity coincided with the sequential dominance of a few particular species. Bromus sterilis and Festuca valesiaca were the most important species driving heterogeneity. Similar patterns were recorded at two monitoring sites. Changing the sampling unit size computationally, varying the dissimilarity indices, or excluding dominant species had little influence on the results. Using null models, we removed the effects of species richness and abundance and found an increasing degree of spatial dependence as succession progressed. However, the corresponding beta deviations also showed non-linear, fluctuating patterns. Our results support the cycling heterogeneity hypothesis in secondary grassland succession. Increasing understanding of heterogeneity patterns provides new opportunities to optimize the temporal and spatial design of grassland restoration measures.

Litter accumulation and small mammal disturbances create specific fine-scale microhabitats in grasslands. These microhabitats serve as safe sites and regeneration niches for subordinate plant species and are important in diversity maintenance. Previous experiments manipulating litter and disturbance and studying their effects on diversity revealed complex relationships. However, little is known about the realized net effects of these mechanisms in different types of grasslands. We conducted a long-term observational study exploring these patterns and their effects in successional and mature grasslands. We applied a specific mapping technique: the presences of litter, disturbance, and living plant species were recorded in 5 cm × 5 cm contiguous microquadrats along 52 m permanent transects. Sampling was repeated annually over 10 years. Spatial dynamics and associations with subordinate grassland specialists were evaluated using information theory models. Analyses were performed at increasing spatial and temporal scales. Varying associations were found across years. Negative associations dominated the relationships between litter and local diversity hotspots, while the relationships with disturbances were mainly neutral. When analyses were repeated at longer time scales, consistent negative associations were detected between litter and diversity hotspots. Long-term relationships between disturbance and diversity were negative in old-fields and positive in the natural grassland. To collect more representative and reliable data on the role of plant litter accumulation and small mammal disturbances, we recommend long-term annual monitoring and the application of temporal scaling based on cumulative diversity.

This study investigated whether permanent and regenerative (rotational) grazing systems are associated with differences in fecal bacterial and fungal microbiota of donkeys under extensive pasture conditions. Young female donkeys were assigned to permanent or regenerative grazing, and paired fecal samples from eight animals per system were collected before pasture access and at the end of the grazing period. Culture-based microbial counts, parasitological examination, animal performance measurements, forage assessment, and bacterial 16S rRNA gene and fungal ITS amplicon sequencing were performed. Donkeys under regenerative grazing showed higher average daily gain than those under permanent grazing (378.0 ± 57.8 vs. 242.4 ± 65.8 g/day; p < 0.001), whereas culture-based fecal microbial counts and fecal egg counts did not differ significantly between systems. Beta-diversity analyses identified sampling time as a consistent source of variation in both bacterial and fungal communities, whereas associations with grazing system and its interaction with sampling time depended on the distance metric used. Bacterial communities retained a large shared core, whereas fungal communities showed stronger compositional turnover. Longitudinal differential abundance analysis identified 336 bacterial and 66 fungal amplicon sequence variants (ASVs) with significant grazing system × sampling time interactions. More positive temporal responses under regenerative grazing were observed among several Spirochaetota and Neocallimastigomycota ASVs, whereas detected Methanobrevibacter ASVs showed a more positive temporal change under permanent grazing.