Water repellency under different plant species in a calcareous forest soil in a semiarid Mediterranean environment

Abstract

Abstract:Water repellency (WR) is a property that has implications on the hydrologic balance in affected soils. In semi-arid areas where water supply is limited, even slight WR may play an important role in the infiltration and spatial distribution of precipitation into the soil. Acidic and sandy-textured soils have been demonstrated to be more prone to develop WR, but there are studies reporting water repellent properties in other soil types. In the present study we investigated soil WR under four plant species in a semi-arid area with a calcareous, medium-textured forest soil. For this purpose, 160 soil samples were taken at micro-sites under different species (Pinus halepensis, Quercus coccifera, Juniperus oxycedrus and Rosmarinus officinalis). Soil WR was measured with the water drop penetration time (WDPT) test on air-dried samples. Samples with WDPT > 5 s were classified as water repellent. WR was present in 20% of the samples, and its persistence ranged mainly between 10 and 30 s. Under P. halepensis and Q. coccifera, WR occurred more frequently (40 and 30%, respectively) than under J. oxycedrus and R. officinalis (only 5% in both cases). In order to know the causes of the difference in occurrence of WR under the selected species and to establish relationships, soil organic matter (SOM) content and pH were measured for a selection of 66 samples, including all 32 water repellent and 34 wettable samples selected from those taken under the four species (n D 66). A negative relationship between WR and pH was found for all species. Moreover, in the case of P. halepensis soil samples, a positive correlation between WR and SOM content was found. A discriminant analysis allowed for the distinction between water repellent and wettable conditions in calcareous soils, based on the information provided by pH, SOM content and vegetation type. Soil pH turned out to be the most important parameter for discrimination. The hydrological and ecological implications from these results are discussed with special focus on the areas in the region extensively afforested with P. halepensis.

Biological and chemical factors controlling the patchy distribution of soil water repellency among plant species in a Mediterranean semiarid forest

“…Soil WR patchy distribution has already been reported in a large quantity of works carried out in forest soils in Mediterranean ecosystems (Martínez- Zavala and Jordán-López, 2009;Mataix-Solera et al, 2007). In agreement with these researches, our results showed a high variability in persistence of WR, around 41% of samples were repellent, and the influence of SOM content on soil WR was evident (r = 0.872 (Fig.…”

“…Ihis phenomenon is of special interest in semiarid areas, such as Mediterranean ecosystems, where water is considered to be one of the fundamental controls affecting the structure, function, and diversity of ecosystems (Rodriguez-Iturbe, 2000). In ecosystems where water resources are limited, even slight WR may play an important role in the infiltration pattems and the spatial distribution ofwater in the soil (Mataix-Solera et aL, 2007 ). WR has hydrological impacts, but also ecological consequences, with repercussions on plant growth (Doerr et aL, 2000).…”

“…WR has hydrological impacts, but also ecological consequences, with repercussions on plant growth (Doerr et aL, 2000). Ihis could be the reason why several studies single out the production of hydrophobins by plants, as a possible ecological strategy (Mataix-Solera et al, 2007 ). It is thought to be a mecharusm for improving water conservation by channeling water deep into the soil profile following preferential flow pathways (Moore and Blackwell, 1998;RobinsonetaL, 2010 ), whileatthesame timereducing evaporation due to the spatial dryness ofthe surface layer (Doerr et aL, 2000).…”

“…In the Mediterranean areas different evergreen trees (such as Pinus and Quercus) and shrubs are usually associated with soil WR under natural conditions (Arcenegui et aL, 2008;Jordán et aL, 2008;Mataix-Solera et al, 2007;Verheijen and Cammeraat, 2007 ). Ihere is a large quantity of research publications that associate soil WR with the SOM content (Doerr et aL, 2000;Mataix-Solera and Doerr, 2004;Zavala et aL, 2009).…”

“…Ihere is a large quantity of research publications that associate soil WR with the SOM content (Doerr et aL, 2000;Mataix-Solera and Doerr, 2004;Zavala et aL, 2009). Despite this, many of them suggest that this relationship could be due to the quality ofSOM (Mataix-Solera et aL, 2007;Rumpel et aL, 2004). In fact, literature has emphasized the importance of lipid fractions released to soil by plants or microorganisms (fungi) (Franco et aL, 2000;Hudson et aL, 1994;Ma'shum et aL, 1988 ), as well as the behavior of specific characteristics of the organic matter, in general assodated with moisture regimes, e.g., temporarily waterlogged soils (Fridland, 1982 ).…”