A conceptual system for identifying and distinguishing different non-rainfall water fractions in agroecosystems

Most of the water input to the ecosystem comes from rainfall. However, depending on the local climatic conditions a considerable amount of water can also be produced by different fractions of non-rainfall water inputs (NRWIs), namely dew, hoarfrost, rime, fog, and the adsorption of water vapour in the soil. Such NRWIs are often neglected because they are typically small compared to rainfall on the daily scale. Nevertheless, these NRWIs provide our ecosystems with additional water, which is important for the survival of the fauna and flora in the ecosystem, especially during dry periods. 

In the past different devices were used to determine some of these fractions, based on artificial surfaces (e.g., dew or fog collector). We will present a conceptual measurement set-up that allows us to determine each non-rainfall water (NRW) component for natural surfaces of agricultural ecosystems. The method is based on precise weighable lysimeter measurement to determine the incoming water fluxes of NRW. The partitioning between the NRW components will be done based on parallel observations on the surface and air temperature, humidity, rain gauge, and dust collector. Based on this conceptual system, we will compare the temporal development and occurrence of different NRW components for eight different agroecosystems under similar climatic conditions.