Vegetation dynamics of ephemeral and perennial streams in mountainous headwater catchments Vegetation dynamics of ephemeral and perennial streams in mountainous headwater catchments

最小化 最大化

Vol17 No.7: 1684-1695

Title】Vegetation dynamics of ephemeral and perennial streams in mountainous headwater catchments

Author】Pattiyage I. A. Gomes1,2*; Onyx W. H. Wai2; Ganegoda K. Dehini1

Addresses】1 Department of Civil Engineering, Faculty of Engineering, Sri Lanka Institute of Information Technology, Malabe 10115, Sri Lanka; 2 Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China

Corresponding author】Pattiyage I. A. GOMES

Citation】Gomes PIA, Wai OWH, Dehini GK (2020) Vegetation dynamics of ephemeral and perennial streams in mountainous headwater catchments. Journal of Mountain Science 17(7). https://doi.org/10.1007/s11629-017-4640-4

DOI】https://doi.org/10.1007/s11629-017-4640-4

Abstract】Ephemeral and perennial streams of mountainous catchments in Sabaragamuwa Province of Sri Lanka and Hong Kong of China were studied for two years on vegetation dynamics. Each year, sampling was conducted during a period when ephemeral streams had low surface flows. Sampling was realized contiguously using belt transects. The standing crop biomass (hereafter biomass) of herbaceous vegetation in ephemeral channels was comparatively lower than perennials and so was the herb diversity. Herb diversity showed a peak from 1.5 to 4.5 m from the centerline/thalweg of ephemeral and perennial streams. Out of 24 herbs, only three were common for both. A peak herb biomass zone was observed in perennials in the same region where diversity peaked. In ephemerals, herb biomass increased laterally up to ~1.5 m, and was constant thereafter. Seedling experiment results tallied with the field diversity observations of both stream types, and suggested that seed dispersion was the main reason for herb colonization. Furthermore, it showed sapling emergence to be significantly higher in perennials than ephemerals. Return period of annual maximum monthly rainfall was a strong indicator of age of trees in ephemeral streams, and elucidated the possibility of hindcasting past flow episodes. Electrical conductivity was significantly high in ephemeral streams among all the water quality parameters. The contents of the water nutrients were approximately the same in both stream types. While recommending further studies on eco-hydrology of ephemerals, we recognize ephemeral streams to be valuable references in climate change studies due to their responsiveness and representativeness in long term hydrological changes.

Keywords】Ephemeral streams; Herb diversity; Biomass; Mountainous areas; Perennial streams; Sri Lanka