# Assessing Water Infiltration and Soil Water Repellency in Brazilian Atlantic Forest Soils
## 1 Introduction  
The United Nations has declared the period 2021-2030 the decade of restoration to scale up existing initiatives, such as the Bonn Challenge, to restore degraded ecosystems [1]. It is expected that restoration will not only help to slow climate change through carbon sequestration, provide food, and increase biodiversity [2], but will also have hydrological benefits because of the perceived association between forest cover and soil hydrological ecosystem services [3, 4]. In this context, it is necessary to better understand the consequences of forest regrowth on soil hydrological processes, such as water infiltration, which is fundamental to maintain productive soil-water-plant interactions,and also to control soil erosion and runoff, soil moisture content, and groundwater recharge in the ecosystems [5; 6; 7]. Estimating saturated and unsaturated soil hydraulic conductivities is crucial for interpreting and modeling soil hydrological processes. In addition, knowledge of these properties may provide information on the impact of land use on soils characteristics [8], which are rarely considered in studies of forest restoration [9]. During the last years, many infiltration methods and devices have been developed to determine soil hydraulic properties [10]. Among them, the Beerkan method [11] is becoming very popular in soil science because it constitutes a simple and an inexpensive way to determine the saturated soil hydraulic conductivity, \(K_{s}\), in the field [12; 13]. On the other hand, the mini-disk infiltrometer (MDI) is a routinely used method for measuring infiltration rates under negative pressure head in the field. The MDI is easily transportable and easy to use on hillslopes, thus, it substantially facilitates the replicability of the measurements [10]. Our previous study in the Atlantic Forest of Brazil [14] used the Beerkan protocol at three land covers, namely pasture, 9-year-old restored forest, and remnant forest. Our results showed that water repellency impacted water infiltration, yielding convex shaped cumulative infiltration curves. However, this observation was not carefully assessed. Similarly, many studies on tropical soils have reported some indirect effects of water repellency on water infiltration, such phenomenon is still poorly documented, especially in comparison with temperate regions [5; 15; 16; 17]. Soil water repellency (SWR) or hydrophobicity is a transient soil property with which soils increase the resistance to wetting and infiltration. It is spatially and temporally very variable [18; 19]. This is caused mainly by amphiphilic molecules produced by plants and organism, and generally occurs after forest fires or dry periods. Other factors that can be related to water repellency are the soil texture, soil temperature, pH, water content, soil organic carbon, land use, and plant cover [18; 19; 20; 21]. In addition, recent research highlighted that climate change could increase the water repellency of soils, due to the increasing occurrence of extreme events such as droughts, which create the soil conditions (i.e., high temperatures and low soil water content) that promote the water repellency [22]. Currently SWR is receiving increased attention in the scientific literature, due to the important hydrological effects. For example, SWR reduces infiltration capacity, increases runoff rates as well as leaching of agrochemicals and soil erosion, also it can affect negatively the crop production, nutrients, and plant-available water [17; 23; 24]. On the other hand, SWR has positive impacts on soil aggregate stability and organic carbon sequestration [22]. [PERSON] and [PERSON] [17] reported the benefit of SWR for the arid and semi-arid climates, considering that this soil property reduces the loss of soil water by evaporation and allows the rainwater to reach deeper depths. Despite these efforts, our understanding of SWR is still limited [18], especially when subcritical phenomena occur.