Interactive effects of light, water, soil type and competition on the endangered Minuartia smejkalii vary over time

Understanding drivers of species performance is crucial for their effective conservation. Despite a range of studies on the effects of single biotic and abiotic factors on plant performance, very little is known about interactions among multiple factors and their effects over time. We studied competition and abiotic interactions in an endemic species of the Czech Republic, serpentinophyte Minuartia smejkalii, over four years. In a full factorial experiment, we evaluated the performance of M. smejkalii alone, in the presence of a competitor, Festuca ovina, and under different abiotic conditions, including different types of soil, light exposure and water regime, and observed its changes over time. The results indicate very complex interactions among these factors. Competition had negative effects on the performance of M. smejkalii (1.2 times larger plants and 1.8 times more flowers in the absence of the competitor), but abiotic factors had stronger effects than competition alone. The effects of F. ovina on M. smejkalii also varied depending on whether shaded or not and soil conditions. Biotic and abiotic factors had contrasting effects on plant and number of flowers, suggesting that investment in growth and reproduction are context dependent. The size of plants grown in shaded areas was 2.7 times larger than those grown in full sun, whereas plants under full sun produced 1.7 times more flowers than those grown in shaded conditions. Type of soil did not affect plant area, but plants produced 1.5 times more flowers in non-serpentine soils. Our results suggest that the effects of competition are very complex, interact with abiotic factors and vary over time. We highlight the importance of long-term studies to identify competitive interactions and the importance of studying competition under multiple conditions. Understanding how competition might affect performance of the endangered M. smejkalii, under certain abiotic conditions (i.e. soil, water, shading), provides essential information for implementation of more efficient long-term conservation strategies.