Drivers of field-saturated soil hydraulic conductivity: Implications for restoring degraded tropical landscapes

David Falk; Leigh A Winowiecki; Tor-Gunnar Vågen; Madelon Lohbeck; Ulrik Ilstedt; Justin Muriuki; Alex Mwaniki; Aida Bargués Tobella

doi:10.1016/j.scitotenv.2023.168038

Drivers of field-saturated soil hydraulic conductivity: Implications for restoring degraded tropical landscapes

Sci Total Environ. 2024 Jan 10:907:168038. doi: 10.1016/j.scitotenv.2023.168038. Epub 2023 Oct 24.

Authors

David Falk¹, Leigh A Winowiecki², Tor-Gunnar Vågen², Madelon Lohbeck³, Ulrik Ilstedt⁴, Justin Muriuki⁵, Alex Mwaniki⁵, Aida Bargués Tobella⁴

Affiliations

¹ Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå SE-901 83, Sweden; World Agroforestry (ICRAF), P.O. Box 30677-00100, Nairobi, Kenya. Electronic address: dsefalk@gmail.com.
² World Agroforestry (ICRAF), P.O. Box 30677-00100, Nairobi, Kenya.
³ Forest Ecology and Forest Management Group, Wageningen University, P.O. Box 47, Wageningen, the Netherlands.
⁴ Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå SE-901 83, Sweden.
⁵ Kenya Cereal Enhancement Programme - Climate Resilience Agricultural Livelihoods (KCEP-CRAL), Ministry of Agriculture and Livestock Development, P.O. Box 30028-00100, Nairobi, Kenya.

PMID: 37879476
DOI: 10.1016/j.scitotenv.2023.168038

Abstract

Water security represents a major challenge in East Africa, affecting the livelihoods of millions of people and hindering sustainable development. Predicted increases in rainfall intensity and variability are expected to exacerbate water insecurity and land degradation. Improving soil infiltrability is an effective strategy for addressing water insecurity and land degradation. Research on soil infiltrability is often highly localized; therefore, scientific understanding of the drivers of infiltrability on larger spatial scales is limited. The aim of this study was to understand the main drivers of infiltrability across five contrasting landscapes in Kenya. We measured field-saturated hydraulic conductivity (K_fs) in 257 plots and collected data for variables representing soil properties (sand content, soil organic carbon (SOC) and pH), land degradation (grazing pressure and presence of erosion), vegetation quantity (woody aboveground biomass), and vegetation quality (functional properties and diversity). We used generalized mixed-effects models to test for the effects of these variables on K_fs. Median K_fs for the five sites ranged between 23.8 and 101.8 mm h^-1. We found that K_fs was positively associated with sand content (standardized effect 0.39), SOC content (0.15), and functional diversity of woody vegetation (0.09), while it had a negative relationship with the presence of erosion (-0.24) and grazing pressure (-0.09). Subsequently, we conclude that infiltrability can be enhanced through using land restoration strategies which specifically target parameters that affect K_fs. The results further support that K_fs is not solely dictated by inherent soil properties, and that management interventions which boost SOC, reduce erosion, and minimize unsustainable grazing can help address water scarcity by restoring soil hydrological function.

Keywords: Functional diversity; Infiltrability; Kenya; Land degradation; Soil organic carbon; Water security.