Have you ever noticed the smell of rain? Why does wet soil smell so good?

The smell of wet soil plants oils released into the soil during dry periods is due. These substances accumulate in the soil and mix with geosmin, produced and released by several groups of bacteria, including actinobacteria (eg, Streptomyces) and cyanobacteria. Geosmine (from Greek “geo”, earth, and “osmin”, smell) is a bicyclic alcohol derivative of decain, and was firstly described in the 1960s (Gerber and Lechevalier, 1965). When it rains, these chemicals are released into the atmosphere and cause a special smell which is known in English as petrichor (Greek “petros”, stone, and “ikhôr” liquid flowing through the veins of the gods).


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What is connectivity?

Over the recent decades, a growing number of studies have highlighted the role of hydrological and sediment connectivity processes in relation to watershed management, topography, aspect, soil erosion (Bracken and Croke, 2007; Heckmann et al., 2010; Hopp and Mc Donnell, 2009; Parsons et al., 2996), movement of nutrients and pollutants (Keesstra et al., 2012a; Puttock et al., 2013; Okin and Gillette, 2001; Turnbull et al., 2011), vegetation (Jordán et al., 2008) or infrastructures (Jordán and Martínez-Zavala, 2008; Müeller et al., 2008; Ocampo et al. 2006). Water and sediment connectivity has emerged as a significant conceptual framework for understanding the transfer of surface water and sediment and associated substances through landscapes. With “connectivity”, we make reference to the interdependence of hydrological processes with other elements of the landscape as soil, highlighting the strong relationship among them. This relation occurs spatially at different scales (Bracken et al., 2014; Wainwright et al., 2011), from molecular to landscape processes through intermediate scales as aggregates, pedons or landforms(Brown et al., 2009; Dosseto et al., 2010; Harvey, 2002; Fryirs et al., 2007; Hooke, 2003; Lane et al., 2008; Jain and Tandon, 2010), and in a time-dependent way (Benda and Dunne, 1997; Harvey, 2002; McGuire and McDonnell, 2007; Otto et al., 2009).

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