Combined effects of moss crusts and pine needles on evaporation of carbonate-derived laterite from karst mountainous lands

The development of biocrusts and litter cover has been promoted by the vegetation restoration of karst mountainous lands in recent decades. However, the contribution of biocrust and litter to the karst terrestrial water cycle is still unclear. The interactive effects of moss crusts and pine needles on evaporation processes were explored by inserting microlysimeters (20 cm radius and 35 cm height) into the karst mountainous lands to collect undisturbed soils. Four moss crust biomass levels (0, 0.32, 0.64 and 0.96 kg m−2) and three pine needle biomass levels (0, 0.32 and 0.64 kg m−2) were used to estimate the influences of moss crusts and pine needles on evaporation losses and surface temperatures. In addition, the performances of two simplified evaporation concepts considering the interaction effects of moss crusts and pine needles were also assessed. The effect of pine needle cover on reducing evaporation rates was stronger than that of moss crusts. Moreover, the influences of moss crusts on the evaporation rate were obviously restricted by the higher biomass of pine needles, while the effects of pine needles on the evaporation rate were not highly affected by the moss crusts. Furthermore, thermal signatures showed that the pine needles had a much larger positive effect on the surface temperature (pr = 0.50) compared to the effect of the moss crusts (pr = 0.17). There was a significant relationship between the value of Ebare-soil/E0 and the mean soil water content SWCmean for bare soils. The predictive ability of the one-parameter concept (weighted average vegetation coefficient kc) was slightly better than that of the double-parameter concept (moss crust factor kMC and pine needle factor knp). The key ecohydrological role of ground cover in controlling evaporation cannot be neglected for karst mountainous land management and preventing rocky desertification.