# Assessing Water Infiltration and Soil Water Repellency in Brazilian Atlantic Forest Soils
## 4 Conclusions  
To improve the soil hydraulic characterization of the soils under different land uses in the Atlantic Forest of Brazil, we measured and compared the unsaturated and saturated soil hydraulic conductivity, using the MDI and Beerkan method for three land covers, namely pasture, 9-year-old restored forest, and remnant forest. This research reports, for the first time, provide evidence of SWR in the Atlantic Forest, especially in the remnant forest. Our measurements demonstrated that SWR affected the early stage of the infiltration process. The comparison between alternative methods to estimate \(K_{\text{s}}\) allowed to account for the effect of SWR on water infiltration measurements. In particular, when there are evidences of SWR, our results suggest using the SSBI method instead of BEST-steady to avoid the failure of the analysis in case of string SWR. Indeed, the SSBI method allowed to maintain the integrity of the infiltration dataset, facilitating the hydraulic comparison between different land uses. Tension  
Figure 6: Comparison of the mean saturated soil hydraulic conductivity values estimated with BEST-steady, \(K_{\text{s}B}\) (mm h\({}^{-1}\)), and the SSBI method, \(K_{\text{s}S}\) (mm h\({}^{-1}\)), and hydraulic conductivity, \(K_{\text{0}}\), \(K_{\text{-5}}\), and \(K_{\text{-20}}\) (mm h\({}^{-1}\)), values measured with the minidisk infiltrometer under a tension of \(0\), \(-5\), and \(-20\) mm. For a given plot, means that do not share a letter are significantly different according to the Tukey honestly significant difference test (\(p<0.05\)). (MDI) and ponding (Beerkan) infiltration tests provided a complementary information, highlighting a clear increase of the hydraulic conductivity, especially at the remnant forest plots, when moving from near-saturated to saturated conditions. This information is relevant to assess the infiltration recovery after forest restoration, as it signals soil structure heterogeneity and higher soil macroporosity. In addition, measuring the unsaturated soil hydraulic conductivity with different water pressure heads also allowed to estimate \(\lambda_{\text{c}}\) in the field. This approach, in conjunction with Beerkan measurements, allowed to generate better \(K_{\text{s}}\) estimates based on field measurements, and also avoided any subjectivity caused by assuming a constant \(\lambda_{\text{c}}\) value, which is often selected based on general descriptions of soil textural and structural characteristics when estimating \(K_{\text{s}}\) from ponding infiltration experiments [34]. Nonetheless, developing alternative methods for estimating \(\lambda_{\text{c}}\) is desirable for alleviating the amount of work necessary to accurately estimate \(K_{\text{s}}\). In this investigation we used the water repellency secession time (WRCT) and water drop penetration time (WDPT) to assess SWR. The SWR was observed in pasture and forest soils with higher sand content. As expected, SWR phenomena were less severe for increasing soil moisture conditions and more common on remnant forest soils. SWR has important hydrological effects, including water supply in forest ecosystems. Thus, SWR cannot be neglected in forest soil hydraulic studies and it must be accounted when developing hydrological models. Future research will focus on understanding the interactions between vegetation, soil biology and soil properties (i.e., including physical, chemical, and mineralogical properties) that are promoting SWR in Atlantic forest soils. Details on the effects of forest restoration on water repellency are severely lacking. It is also important to consider the temporal and spatial dynamic of the soil infiltration and water repellency. For example, future studies could quantify the spatial extent at the larger scale, upscaling the measurement from point to catchment scale.