Understanding the effects of weather parameters on the population dynamics of an endangered geophyte supports monitoring efficiency

Abstract

Due to their complex life-cycles geophytes are often neglected or mistreated during monitoring and conservation activities, despite they are important elements of early-spring communities. Their life-cycle is often strongly affected by weather parameters, i.e. temperature, precipitation, and light, but the main and combined effects of these parameters are often contradictory and show high intra-annual variability even within species. Deeper knowledge about the biotic and abiotic factors affecting the population dynamics of geophytes is needed to support the designation of evidence-based effective conservation plans. In our study we aimed to explore the link between weather parameters and population dynamics of Colchicum bulbocodium Ker-Gawl., an endangered and strictly protected geophyte. We monitored three phenological phases (flowering, assimilation, fruiting) of in total 1,069 individuals in Hungary, in permanent plots for six consecutive years. The effects of temperature- and precipitation-related weather parameters, as well as plot characteristics on the response variables were studied with generalized linear mixed models. Our results showed that phenology of C. bulbocodium was more strongly related to the actual weather than to the lagged effect of weather parameters of the previous year. Increasing temperature and lack of cold periods had negative effect on all phenophases. We highlighted that population estimation based on the number of flowering individuals in a single year can underestimate population size by 40–83%. Monitoring in years following wet and cold springs and cold winters could increase the accuracy of population estimations of the flowering individuals, while surveys in cold springs can estimate reproduction success the most accurately.