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Proper estimation of the herb layer annual net primary production (ANPP) can help to appreciate the role of this layer in carbon assimilation and nutrient cycling. Simple methods of ANPP estimation often understate its value. More accurate methods take into account biomass increments of individual species but are more laborious. We conducted our study in an oak-hornbeam forest (site area 12 ha) dominated by beech in NW Poland during two growing seasons (2010 and 2011). We collected herb layer biomass from 7 to 10 square frames (0.6 × 0.6 m). We collected plant biomass every week in April and May and every two weeks for the rest of the growing season. We compared six methods of calculating ANPP. The highest current-year standing biomass (1st method of ANPP calculation) was obtained on May 15, 2010—37.8 g m−2 and May 7, 2011—41.0 g m−2. The highest values of ANPP were obtained by the 6th method based on the sum of the highest products of shoot biomass and density for individual species: 74.3 g m−2 year−1 in 2010 and 94.0 g m−2 year−1 in 2011. The spring ephemeral Anemone nemorosa had the highest share of ANPP with 50% of the total ANPP. Two summer-greens, Galeobdolon luteum and Galium odoratum, each had a ca. 10% share of ANPP. The best results of ANPP calculation resulted from laborious tracking of dynamics of biomass and density of individual shoots. [ABSTRACT FROM AUTHOR]

Seasonal fluctuations of light availability, nutrient concentrations, and moisture affect plant population traits like density, standing biomass, and flowering. We analyzed seasonal changes of density and shoot biomass of the four most frequent herb species growing in an oak–hornbeam forest community, i.e., Anemone nemorosa, Ficaria verna, Galeobdolon luteum, and Galium odoratum. In 2010 and 2011 plant biomass was harvested from 7 to 10 randomly situated square sample plots (0.36 m2) in the homogenous oak–hornbeam forest community every week in the spring and every two weeks in the summer and autumn. The highest abundance of Anemone nemorosa reached over 1000 shoots per m2, of Ficaria verna 459.5 shoots per m2, of Galium odoratum 83.6 shoots per m2, and of Galeobdolon luteum 98.4 shoots per m2 (means for 2010 and 2011, based on all sample plots). We did not observe negative correlation between density and shoot biomass. Growth rates of vegetative shoot biomass amounted to 0.857 mg day−1 for Anemone nemorosa, 0.467 mg day−1 for Ficaria verna, 0.722 mg day−1 for Galium odoratum, and 0.448 mg day−1 for Galeobdolon luteum (means for 2010 and 2011). Spring ephemerals had much higher densities of shoots than summer-greens. Summer-greens reached higher biomass of individual shoots than spring ephemerals. Flowering shoots constituted only 4, 2, and 11% of all shoots for A. nemorosa, F. verna, and G. odoratum, respectively. More resource availability resulting in high shoot biomass did not translate to higher share of flowering shoots. [ABSTRACT FROM AUTHOR]

Although interactions between alien and native plant species are well studied, data on interactions between two co-existing alien species with respect to their invasibility are scarce. The aims of this study were (1) to evaluate three factors shaping abundance of the alien shrub species Cornus alternifolia: abundance of another alien (invasive) shrub species ( Prunus serotina), type of tree stand (coniferous vs. broadleaved) and distance to propagule sources and (2) to assess the potential dispersal distance of the species studied. Densities of both species were assessed within 194 experimental plots (located in experimental plantations of trees) in Rogów Arboretum (Central Poland). P. serotina occurred on 79 and C. alternifolia on 33 of the 194 plots. The furthest distance of C. alternifolia from the propagule source was 338 m. C. alternifolia reached higher densities in coniferous than broadleaved tree stands. Density of C. alternifolia depended on tree stand type and distance from the propagule source, but did not depend on density of P. serotina. Density of C. alternifolia decreased with increasing distance from the propagule source; however, this relationship was modified by the type of tree stand: densities were lower in broadleaved than in coniferous stands. The presence of the invasive species seems to neither facilitate nor limit the dispersal distance of C. alternifolia, as these two species differ in shade tolerance. The study also provided the first information about C. alternifolia potential invasiveness, because earlier this species was noticed only as casually escaping from cultivation in Slovakia. [ABSTRACT FROM AUTHOR]