Impact of Herbaceous Vegetation on Recovery of a Harvested Headwater Catchment

Abstract

The processes of soil erosion and sedimentation may seriously affect mountain wetlands fed from surrounding upslope sources. In headwaters of the Jizera Mts., the potential annual loss of soil varies from 0.2 mm (mature spruce stands) to 1.2 mm (conversion to grass). Negligible sheet erosion has been observed at run-off plots covered by herbaceous layers. However, very important soil loss occurred in erosion rills originated by skidding of timber (from 0.3 to 1.2 mm/year). The critical parameter affecting the recovery of rills is their depth. The increasing depth of rills is related to a drop in both vegetation cover and number of species, and to a higher proportion of hemicryptophytes and plants forming clusters or bunches. These plants do not have a high potential to cover the soil surface, and to protect it against erosion. Thus, the process of soil erosion may be prolonged. The number of species (species richness) found in recovering rills increases significantly with the time (age of rills). From the point of view of soil protection, more shallow rills (depth from 0 to 0.25 m) can recover much better than only few deep rills (depth over 0.5 m). The shallow rills can re-grow quite fast, but in the deep rills, the spontaneous succession is very slow or even impossible. So, the rills deeper than 0.5 m require the application of reclamation techniques (stabilisation of the slope by check-dams etc.). It is evident, that environmental friendly forest practices may avoid the risk of soil erosion from the harvest of timber.