Tussocks created by Carex schmidtii in sedge meadows may be able to support biodiversity because of their structural complexity. Concerns about diversity loss and the potential to restore species-rich tussocks led us to investigate how tussocks foster high species richness and affect composition. We investigated vegetation in paired plots on and between tussocks of C. schmidtii, and measured environmental factors on and between tussocks. In all, 79 taxa were found in the sedge meadows. Species richness was higher on rather than between tussocks. During the growing season, the tops of tussocks were above the water level, whereas the area between tussocks was flooded. Soil temperature, organic carbon, soil total P and litter depth were higher on rather than between tussocks. Soil water content and soil total N were lower on than between tussocks. Species richness on tussocks increased with increasing tussock basal area, height and surface area. Based on canonical correspondence analysis, plant composition was mostly related to field water depth, organic carbon and tussock basal area. We conclude that tussocks enhance species richness by increasing surface area, and support a diversity of co-occurring species by creating at least two distinct microhabitats.

Question: What environmental variables and plant–plant interactions affect mire bryophyte distribution and does the surrounding landscape with human disturbance play a role in the mire bryophyte distribution? Location: Jinchuan mire, Northeast China. Methods: We studied the spatial distribution of bryophytes in 100 1 × 1 m quadrats in the mire. Spatial variables were simulated by analysis of the distance-based Moran’s eigenvector maps (dbMEM). Variation partitioning analysis was used to reveal the relative contribution of spatial and environmental variables to bryophytes. The relationship between environmental variables and bryophytes was tested by redundancy analysis (RDA). We used co-occurrence and niche overlap models to detect interactions among bryophytes. We also studied the influence of the surrounding landscape on the distribution of bryophytes in relation to water chemistry. Results: The eight bryophytes occupying part of the mire had both a general distribution trend and a local spatial structure. Over 40% of the total variation in cover among bryophytes could be explained by spatial and environmental variables. In this fraction, the environmental variables explained 29.7% of the variation, of which only 4.5% was not spatially structured. RDA showed the contribution of dwarf shrub cover (SC), Na, and P to the bryophyte distribution was relatively large. Concentration of Na and SC decreased gradually from north to south, and contributed most to the variation in species composition along the first axis. The concentrations of P decreased from east to west, and contributed along the second axis. All the bryophyte species were spatially isolated but with large niche overlaps, indicating that the bryophyte community was structured by interspecific competition. Conclusion: Sodium mainly originating from the volcanic hill and P from the paddy fields were the main environmental factors affecting the bryophyte distribution. Concentrations of Na and P showed spatial structure, and resulted in induced spatial dependence (ISD) playing a major role in the spatial structure of the bryophyte community. Dwarf shrubs affected by nutrient distribution in the mire significantly influenced the bryophyte distribution in the mire. We conclude that the surrounding ecosystems had important influence on bryophyte distribution via nutrient influx. Furthermore, competitive interactions exacerbated the spatial separation of bryophytes.