Effects of litter cover on partitioning of natural rainfall for plantation Pinus tabulaeformis forest in the Loess Plateau of China

      Litter accumulates yearly since vegetations were widely planted for reforestation, and it plays an important role in hydrologic cycling. There is little information on the effects of litter on re-allocation of rainfall processes. Eight runoff plots were established in the Pinus tabulaeformis stand with four litter (needle-leaf) masses (0, 0.6, 1.2, 1.8 kg/m²), and the surface runoff (R), evaporation (E), infiltration and soil moisture dynamics were measured throughout the mainly rainy season from August 4 to September 28 in the Loess Plateau. The results showed that, soil evaporation mainly occurred in daytime for bare soil, and decreased with increasing litter masses, and litter cover is prone to hinder the heat and water exchange between soil and atmosphere, especially for the soil layer 0~5 cm. Litter cover greatly decreased surface runoff, and it may hinder infiltration at the beginning of rainy season, but increasing soil water storage (SWS) with deeper infiltration depth for the long run, especially for the litter masses 1.2 and 1.8 kg/m². With the litter covered, the ratio of R to precipitation (P) was less than 10%, no matter it was heavy rain or light rain. However, the proportion of R was amplified when the rainfall was intense for the bare soil. And the ratio of E to P was always below 10% for all treatments, except for light rainfall. With the increased litter masses, the proportion of R and E all decreased, and the SWS/P has well nonlinear positive relationship with litter masses, and it was proved that more than a half of rainfall was stored even for bare soil. This study may helpful to better understanding the effects of litter on hydrological response, and promotes practical measurements to the management of precipitation in a forest stand view.