1. The monsoon causes major flood events in some Himalayan streams, but their seasonal predictability might reduce the resulting disturbance. We assessed seasonal change in the benthos of 16 streams in central Nepal over a gradient of declining rainfall and increasing altitude from 600 to 3800 m. All sites were surveyed on four occasions, two in winter (November) and two pre‐monsoon (June), with additional sampling during the monsoon (August) at four low altitude sites. Invertebrate abundance, taxon richness and persistence were assessed at all sites, and density and meso‐habitat distribution at the four low altitude sites only. 2. Strong seasonal variation among invertebrates was confined primarily to streams at low altitude (600–800 m) where monsoon rainfall was greatest and catchments were dominated by terraced agriculture. At these sites, a significant reduction in benthic density (on average by 77%) and taxon richness (by 20%) occurred between the winter and pre‐monsoon periods, so that invertebrate numbers were already low before the monsoon. A further significant decline occurred in all meso‐habitats during the monsoon, but the change in density was small in absolute terms. 3. Persistence in rank abundance was equally low at all sites, but turnover in composition was significantly lower at sites in semi‐natural forest than in catchments managed for terracing or alpine pasture. 4. These data provide no evidence that monsoonal floods represent major disturbance, instead supporting the view that the ecological response might reflect an adjustment to predictable flow pattern. However, catchment land use in the Himalaya appears to be a significant source of ecosystem instability, and confounds the simple interpretation of monsoon effects.
1. Macroinvertebrate drift was investigated in seven small headwater streams along an altitudinal gradient (600-3350 m) in two adjacent river systems in east-central Nepal. Study streams in the Likhu Khola were at the lowest altitude and flowed through terraced agriculture. At higher altitudes, Langtang streams flowed through catchments of forest and alpine scrub. Samples were collected every 3h over a 24h period in each stream. 2. Terrestrial macroinvertebrate drift was greatest in streams with semi-natural catchments, but was scarce in streams where trees were absent. 3. At lower altitudes drift was dominated by Hydropsychidae and Baetidae, which were most abundant in night samples, and Hydracarina, which tended to be day active. Baetidae also dominated drift at high altitudes, but here drift was increasingly aperiodic or diurnal. The composition of the drift reflected a significant correlation between the percentage abundance of taxa in the drift and benthos. 4. As in other mountain regions of the world, drift was aperiodic in fishless streams (high altitude), but strongly nocturnal in streams where insectivorous fish were present (lower altitude). However, a wide array of potentially important variables along the altitudinal gradient, such as temperature, climate and community structure, might be important influences on these patterns.
Lowland grasslands in Nepal were thoroughly surveyed in 1996-1999 to assess the status and distribution of the globally threatened Bristled Grassbird Chaetornis striata. Birds were located on foot, from elephants and from jeeps by sight and sound backed up by mistnets and tape playback. The status information was updated again by visiting these areas in 2010-2012. Bristled Grassbirds were recorded in Sukla Phanta and Koshi Tappu Wildlife Reserves, and Chitwan National Park where most of the Nepal population is confined. From the research, it was found that they were most associated with newly formed Saccharum and Imperata dominated grasslands during summer. The low numbers present during winter suggested that this species was primarily a summer migrant to Nepal. A total population for Nepal is presented based on a reliable density estimate. Loss and degradation of grassland habitat and invasion of Mikania micrantha were identified as the major threats. Further research on migratory status, better control of cattle grazing inside reserves, expansion of Protected Areas to include more grassland, and listing of Bristled Grassbird as protected under the wildlife law of Nepal for its conservation are highly recommended. DOI: http://dx.doi.org/10.3126/init.v5i0.10244 The Initiation 2013 Vol.5; 1-15
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