Recent evidence indicates that extension of phenological duration of mutualistic partners could buffer negative impacts that occur with phenological shifts. Therefore, we suggest that techniques to extend the length of phenological duration will contribute to management of systems experiencing phenological asynchrony. Techniques of phenological phase extension discussed include the role of abiotic heterogeneity, genetic and species diversity, and alteration of population timing. We explore these approaches with the goal of creating a framework to build adaptive capacity and address phenological asynchrony in plant-animal mutualisms under climate change. In this study we focus on the potential to utilize abiotic heterogeneity to extend phenological phase timing via topographic effects on the duration of flowering resources. We recorded flowering time of pollinator resource species across four successive spring growing seasons (2015-2018) on paired north and south aspects in a Northern California grassland. Flowering time differences were evaluated both at the community level and within species present on both paired aspects. The role of plasticity was examined by planting genotypes of Lasthenia gracilis on paired north and south slopes.
Results/Conclusions
We found that aspect is a strong determinant of phenology, with earlier flowering on south-facing slopes. Aspect differences resulted in complementarity in timing of flowering resources across sites, as aspects that started flowering earlier also ended earlier more often than expected by chance. Complementarity between north and south aspects served to extend the flowering time of pollinator resources by an average of 4-8 days (7-15%), depending on the year. This extension can be attributed to both within species responses to aspect differences as well as species turnover. Our findings indicate that heterogeneous topography can extend overall flowering time of pollinator resources, which may support pollinator biodiversity. Extension was most pronounced at the community level, which incorporates species turnover as well as plastic and genotypic differences within species. A longer flowering phenology across a landscape may aid both pollinator and plant species to cope with these changes by buffering the magnitude of asynchrony at the landscape level. Conserving, restoring and maintaining high species diversity across topographically heterogeneous microsites may be a means of extending flowering time, and thereby supporting biodiversity, maintaining ecosystem function, and buffering the impacts of mutualism asynchronies with climate change.