Hydrologic responses of undecomposed litter mulch on compacted soil: Litter water holding capacity, runoff, and sediment

The surface of the mineral soil is covered by the forest floor forming water absorbent layers. This is how the forest floor plays an important role in soil and water conservation. The aim of this study was to individualize three leaf litters (beech, hornbeam, and maple) applied at three density rates (6, 12, and 18 Mg ha−1) to assess their soil protection capacities. A total of nine treatments were conducted (i.e., beech6, beech12, beech18, hornbeam6, hornbeam12, hornbeam18, maple6, maple12, maple18) on skid-compacted soils in the Hyrcanian forests of northern Iran to evaluate effects at reducing runoff and sediment yield, and to determine the oven-dry weights and water holding capacity of litters. A total of nine runoff plots with dimensions of 1 × 2 m were established on the skid trails during the study period from September to December 2017 in a field experiment under natural rainfall. At the study period, 29 events with a total of 752.2 mm rainfall were measured in the open space area, that 26% of the rainfall was intercepted by canopy cover. Regardless of leaf litter species, the runoff and sediment yield significantly decreased as the leaf litter rate increased. The average runoff in litter plots of beech, hornbeam, and maple was 102.71, 94.25, and 116.87 mm, whereas the average sediment yield was 27.07, 22.33, and 36.73 g m−2 for the study period, respectively. The mean water holding capacity of beech, hornbeam, and maple litter plots amounted to 84.1, 59.16, and 25.81 mm for the study period, respectively. Our study shows that the different species of leaf litter have a diverse range of hydrological functions and litter water holding capacities, which reduced runoff and sediment yield.