The Challenge of Unraveling Feedbacks Between Phytobiomes and Weather

While it is well documented and intuitively obvious that weather affects the microflora of plants, the idea of a reciprocal influence – of plant microflora influencing weather – seemed farfetched until recently.  In the past 10 years, the role of certain ice nucleation active (INA) microorganisms in cloud glaciation and rainfall has become a hot topic of research. These INA microorganisms are commonly found on plants or in agricultural soils and they contribute to aerosols either as whole cells or spores directly uplifted from plants and soil surfaces or indirectly as organic components of mineral-based dusts.  While rainfall patterns depend on synoptic-scale atmospheric circulations, aerosols play decisive roles in the outcome of meteorological phenomena. Land use patterns and seasons influence the types and abundance of biological aerosols.  Geographic contexts, such as those that favor orographic clouds, can affect the magnitude of the influence of these aerosols on rainfall.  As the atmosphere is never free of these aerosols, their effect cannot be separated from synoptic scale processes under real conditions. In light of this coupling and of the variability of aerosols across space and time, it is easy to understand why the decisiveness of aerosols in the processes leading to rainfall is under debate.  Here I will present ideas for experimental approaches to disentangling the specific effects of biological aerosols on rainfall based on what is currently known about feedbacks between land surfaces, their associated microflora and rainfall.