干旱区生态环境知识资源中心

In arid and semiarid environments, where precipitation is scarce and mainly limited to the wet season of the year, the water contribution by non-rainfall water inputs (NRWI) may play a significant role in the water balance. Natural ecosystems are heterogeneous with a great variety of surface covers, such as stones, biological soil crusts (BSC), bare soil, trees, shrubs and other plants. To be able to understand the role that NRWI may have in a system, all the surface types involved and all the NRWI sources (fog, dew and water vapour adsorption) should be differentiated, analyzed and studied separately. This manuscript study NRWI on different cover surfaces of the soil in a natural coastal-steppe ecosystem. Automated microlysimeters were located in the field containing small Macrochloa tenacissima plants, bare soil, stones and biological soil crusts. Daily changes in the water content of the samples were registered. The different sources of NRWI were differentiated and their partial contributions to the total NRWI and to the daily evaporation were analyzed.

Each cover type showed a different response in the presence of NRWI and these responses were also dependent on the NRWI source. In turn, the surface cover influenced the subsequent evaporation the day after. The number of dew events varied with the surface cover type and water vapour adsorption occurred all days in all the covers, alone or preceding a fog or a dew event. Dew represented the main NRWI source in plants and stones, while water vapour adsorption was the main input in bare soil and BSC. Fog was a minor component of the NRWI during the study period and its partial contribution to the total input was similar for all the cover types. NRWI satisfied a great part of the evaporation in the sample, especially in plants and stones. (C) 2015 Elsevier B.V. All rights reserved.