Die Vegetationskarte der Khumbu Himal (Mt. Everest-Südabdachung) 1:50.000

Gefügemuster der Vegetation und Probleme der Kartierung

Abstract

The map was surveyed between August and November 1982 and drafted in the scale of 1: 25,000. The differentiation of vegetation units was undertaken by physiognomic criteria. The vegetation of the cloud forest belt is quasinatural on the shady slopes (Betula utilis and evergreen Rhododendron-woodlands) and mostly anthropogenic on the sunny slopes, which are widely used for winter grazing, because here the snow melts within a few days, whereas the shady slopes remain snow-covered for several months. The potential natural Usnea-covered Abies spectabilis-forests are partly conserved due to the indigenous rules of the Sherpas, a Tibetan tribe inhabiting the Khumbu. Most forests of the sunny slope were removed by the initial fire clearing, probably 450 years ago, and have been successively replaced by grazed open woodlands of Rhododendron arboreum v. roseum and Juniperus recurva, which were degraded by extensive grazing to the present anthropogenic climax, dominated by grazing weeds such as Cotoneaster microphyllus. The potential natural treeline as indicated by forest remnants, is at 4400 m.a.s.l. on the sunny slopes Uuniperus recurva) and at 4200 m.a.s.l. (Betula utilis) on shady slopes. In the alpine belt valley-up wind is decisive for the vegetation pattern of Cyperacee-mats covering windward slopes, and evergreen dwarf Rhododendrons confined to slopes which are snow-protected in winter. In the upper alpine belt the closed cover of alpine turf has been destroyed in a patchy manner, showing open morainic substratum freely moved by periglacial processes, surrounded by a solifluction cliff on alpine turf. The open patches are not recolonized by vegetation but slowly extended by ne edle i'ee. Obviously solifluction is stronger than plant growth. Under the present climatic conditions the vegetation is unable to rebuild a new vegetation cover. This indicates a depression of the altitudinal belts and the temperature. The present 'zonal' vegetation on a closed layer of alpine turf turns out to be a relic of a climatic period which was more favourable for plant growth.