Plants and biological soil crust influence the hydrophysical parameters and water flow in an aeolian sandy soil / Vplyv rastlín a biologického pôdneho pokryvu na hydrofyzikálne parametre a prúdenie vody v piesočnatej pôde

Abstract

This study tested the hypothesis that the changes in hydrophysical parameters and heterogeneity of water flow in an aeolian sandy soil have the same trend as the process of succession. Three sub-sites were demarcated at the area of about 50 m x 50 m. The first sub-site was located at the pine-forest glade covered with a biological soil crust and represented the initial stage of succession. The second sub-site was located at the grassland and represented more advanced stage of succession. The third sub-site was located at the pine forest with 30-year old Scots pines and represented advanced stage (close to climax) of succession. The sandy soil at the surface was compared to the soil at the pine-forest glade at 50 cm depth, which served as a control because it had a similar texture but limited impact of vegetation or organic matter. It was found that any type of vegetation cover studied had a strong influence on hydrophysical parameters and heterogeneity of water flow in an aeolian sandy soil during hot and dry spells. The changes in some hydrophysical parameters (WDPT, R, k(-2 cm), Sw(-2 cm), ECS and DPF) and heterogeneity of water flow in an aeolian sandy soil had the same trend as the process of succession, but it was not so in the case of Ksand Se(-2 cm), probably due to the higher content of smaller soil particles in grassland soil in comparison with that content at other sub-sites. Both the persistence and index of water repellency of pure sand differed significantly from those of grassland, glade and forest soils. The highest repellency parameter values in forest soil resulted in the lowest value of both the water sorptivity and hydraulic conductivity in this soil in comparison with other soils studied. The highest value of ethanol sorptivity and the lowest value of saturated hydraulic conductivity in the grassland soil in comparison with other soils studied were due to the higher content of fine-grained (silt and clay) particles in the grassland soil. The effective cross section and the degree of preferential flow of pure sand differed significantly from those of grassland, glade and forest soils. The change in soil hydrophysical parameters due to soil water repellency resulted in preferential flow in the grassland, glade and forest soils, while the wetting front in pure sand area exhibited a form typical of that for stable flow. The latter shape of the wetting front can be expected in the studied soils in spring, when soil water repellency is alleviated substantially. The columnar shape of the wetting front, which can be met during heavy rains following long dry and hot spells, was attributed to redistribution of applied water on the surface to a series of micro-catchments, which acted as runon and runoff zones.

Effects of biological crust coverage on soil hydraulic properties for the Loess Plateau of China

“…Meanwhile, the thickness and the water repellency of moss (Tables 1 and 4) were significantly greater than those of cyanobacteria, which produced stronger water infiltration blockage Li, Tian, Jia, Zhang, & Liu, 2010;Lichner et al, 2012Lichner et al, , 2013Yang et al, 2016). The differences in the effects of cyanobacteria and moss crusts on soil hydraulic properties in this study are consistent with the results of previous studies (Eldridge et al, 2000;Graetz & Tongway, 1986;Li et al, 2002;Lichner et al, 2012;Wang et al, 2007;.…”

“…Meanwhile, the water repellency of cyanobacteria and moss crusts are approximately 6.84 and 16.04 times higher, respectively, than those of bare soils (Table 4). thus reducing the soil infiltration (Bu et al, 2013;Lichner et al, 2012). Moss is more effective in reducing the soil infiltration capacity than cyanobacteria, which is caused by the difference in the properties of cyanobacteria and moss, as will be discussed later.…”

“…Water repellency, caused by the hydrophobic tissue and exudates of BSCs, is one of the dominant features of BSCs (Lichner et al, 2012(Lichner et al, , 2013. Soil hydraulic properties can be influenced significantly by the water repellency of BSCs, especially the soil sorptivity (Lichner et al, 2012;Malam et al, 2009). Therefore, the water repellency of BSCs can be used to explain the differences in hydraulic properties between cyanobacteria-and moss-covered soils and the variations of soil hydraulic properties with cyanobacteria and moss crust coverage.…”

“…The water repellency was measured using a medicinal dropper at each test site in an "S" pattern via the water drop penetration time (WDPT) method. Detailed measuring procedures can be found in previous studies (Lichner et al, 2012(Lichner et al, , 2013. For each site, there were 20 replicates, and the mean was considered as the WDPT for that case.…”

“…Although there is considerable evidence showing that BSCs are unambiguously effective in promoting the ecological functions in arid and semiarid regions (Eldridge & Greene, 1994;Chamizo et al, 2013;Grote, Belnap, Housman, & Sparks, 2010;Zaady et al, 2000), their roles in soil hydraulic properties are not fully understood (Belnap, 2006;Eldridge & Greene, 1994). A large body of studies has demonstrated that BSCs reduce soil infiltration via the clogging of soil surface conductive pores due to the high water absorption and swelling of BSCs and the inherent hydrophobicity of some crusts (Eldridge et al, 2000;Graetz & Tongway, 1986;Li, Wang, Li, & Zhang, 2002;Lichner et al, 2012;Malam, Défarge, Trichet, Valentin, & Rajot, 2009;Wang, Li, Xiao, Berndtsson, & Pan, 2007). In contrast, some other studies have shown that BSCs can increase soil infiltration by absorbing large amounts of rainfall, increasing the entry points for water into soil via their rhizines and protonema and promoting surface retention because of the increase in soil surface variation in microtopography (Bu, Wu, Zhang, Yang, & Gao, 2013;Eldridge, 1993;Eldridge & Greene, 1994).…”