Impact of tree planting configuration and grazing restriction on canopy interception and soil hydrological properties: Implications for flood mitigation in silvopastoral systems

Compaction of upper soil layers by intensive sheep grazing has been connected with increased local flood risk in silvopastoral systems. A 12 week field study was conducted at the Henfaes Research Station near Bangor, Wales to compare canopy interception, soil water infiltration, and bulk density between a control pasture and two silvopastoral tree planting configurations: trees clumped in fenced-off ungrazed plots and trees planted evenly and grazed. The study's aim was to characterize the potential of these tree planting configurations to reduce local flood risk. Automated throughfall gauges were installed in each silvopastoral treatment along with a similarly designed control gauge located in the grazed control pasture. Soil water infiltration and bulk density were measured 20 times in a stratified random design for each treatment and control. Results showed that the mean soil infiltration capacity in clumped configuration was 504% greater than the control pasture and 454% greater than the even spaced configuration. Average canopy interception was higher in the clumped configuration (34%) than in the even spaced configuration (28%). Soil bulk density was lower in the clumped configuration (0.87 Mg/m3) than in the control pasture (0.93 Mg/m3) and even spaced configuration (1 Mg/m3). Results suggest that silvopastoral systems are more likely to benefit from clumped and ungrazed tree configurations than from evenly-spaced and grazed tree configurations due to enhanced infiltration, lower soil compaction, and increased canopy interception. Our findings support the growing evidence base that fenced-off tree areas in silvopastoral settings can increase infiltration and thus reduce local flood risk. This article is protected by copyright. All rights reserved.