Altitudinal trends in the diatoms, bryophytes, macroinvertebrates and fish of a Nepalese river system

摘要: SUMMARY 1. Hydrobiological changes were assessed along an altirudinal transect of eighteen to twenty-three tributaries from 600 3750m in two adjacent river systems east-central Nepal. The incorporated catchments under terraced agriculture at the lowest altitudes Likhu Khola, through streams forest, alpine scrub and tundra higher Langtang. 2. Diatoms, bryophytes, macroinvertebrates fish all showed pronounced altitudinal assemblage composition as shown by TWINSPAN DECORANA. A few taxa restricted high altitude, but many more occurred only lower where taxon richness increased substantially despite catchment disturbance agriculture. 3. Diatoms characteristic altitude mostly motile, epipelic or episammic Navicula Nitzschia spp., which occur typically greater electrolyte nutrient concentrations. Those steeper sites included attached Fragilaria spp. prostrate Achnanthes tolerant turbulent flow. 4. Cover bryophytes varied within type; springs supported dense mats, unlike fed ice glaciers. Taxa confined low those humid subtropical conditions. 5. Invertebrate families occurring a range burrowers pool dwellers. Numerically, filter feeding Hydropsychidae Simuliidae dominated forested catchments, whereas grazing baetid mayflies tundra. 6. combined density biomass least six species Khola 23–250 (per 100m−2), 86–1282 g wet mass 100 m−2), respectively. No found Langtang streams, probably because torrential headwaters prevented colonization. 7. Our data confirm that transitions stream biota are Himalaya Nepal, likely reflect wide array potential influences.