Growth and reproductive characteristics of C4 weeds under climatic conditions of the Czech Republic

Climate change could promote the altitudinal spread of C4 weed species since they can benefit from warmer climate. The effects of altitude and climatic conditions (the sum of temperatures above 5 degrees C and precipitation) on the biomass and seed production of two annual C4 weeds - Amaranthus retroflexus L. and Echinochloa crus-galli (L.) P. Beauv. - were studied in the Czech Republic. We included both temperature and precipitation variables in the study since they both serve as basic indicators of climate change and thus they have the greatest impact on plant development. The experiment was carried out by sowing both weed species on m(2) area with four replicates in seven localities differing in altitude in 2010 and 2011. We found no significant impacts due to altitude on any variables measured. However, climatic factors explained 44.5% of the variation in plant dry biomass and 41.4% of the seed number produced by A. retroflexus. The same variables did not significantly contribute to the variation in above-ground biomass or seed number of E. crus-galli. These results show the impact of climate conditions to vary between species and not to limit reproduction at high altitudes.