Habitat conditions, stage structure and vegetation associations of geographically isolated subalpine populations of Salix lapponum L. (Salicaceae) in the Krkonoše Mts (Czech Republic)

Shrub communities are important components of the subalpine vegetation. We focused on habitat conditions and stage structure (flowering and non-reproducing individuals) of stands of the endangered Salix lapponum in the Krkonose Mts, Czech Republic. Habitat conditions were determined using soil sample analyses and Ellenberg indicator values (EIVs) derived from fine-scale (1 × 1 m) vegetation plots. The fine-scale plots were compared with coarse-scale releves with the occurrence of S. lapponum acquired from the Czech National Phytosociological Database. We found that S. lapponum grows on nutrient-poor, acidic soils with high relative water contents, high amounts of total nitrogen, low amounts of phosphorus, moderate amounts of magnesium and low to moderate amounts of calcium. The overall proportion of non-reproducing individuals was 35.2%, but strong variations were observed among populations (0–100%). Co-occurring species and EIVs data indicated that flowering individuals are relatively more common in humid, nutrient-rich and warmer microhabitats than non-reproducing ones. Well-developed (“typical”) stands of S. lapponum with a dominance of flowering individuals occur along alpine springs, streams and in glacial cirques (= association Salicetum lapponum Zlatnik 1928), but S. lapponum also grows along transitional mires and peat bogs and in subalpine grasslands. Coarse-scale releves were similar to “typical” stands of S. lapponum at the fine scale but were differentiated from them by high frequencies of several, mainly broad-leaved forbs and herbs typical of moist to wet and fertile soils. Threats to S. lapponum and the future prospects of its stands in the Krkonose Mts are briefly discussed.