关键词: 草地早熟禾, 聚类分析, 种子产量, 产量性状

Abstract: Rivers release large quantities of greenhouse gases into the atmosphere, which is an important link in the material cycling and energy flow of terrestrial ecosystems. Mountainous rivers are ‘hotspots’ for greenhouse gas emission, but the release of CH₄ and N₂O from those rivers has been less documented. To explore the spatiotemporal distributions and related controls of CH₄ and N₂O in middle-large plateau rivers, the seasonal variations of CH₄ and N₂O in tributary and main stream of the Yarlung Tsangpo River were examined. The results showed that the ranges of CH₄ and N₂O concentrations in the Yarlung Tsangpo were 2.3-864.9 and 8.2-23.7 nmol·L^-1, respectively. There was no significant difference in CH₄ concentrations between low-flow and high-flow periods (P=0.112), but the N₂O contents were higher in low-flow months than in high-flow months (P=0.017). River water discharge and water temperature were the major factors controlling the dynamics of CH₄ and N₂O emission, respectively. The release rates of CH₄ and N₂O in the Yarlung Tsangpo River ranged 4.3-11.1 mg C·m^-2·d^-1 and 0.16-0.37 mg N·m^-2·d^-1, respectively. The emission amounts of CH₄ and N₂O in Yarlung Tsangpo River system were 1.88-4.59 Gg C·a^-1 and 0.07-0.16 Gg N·a^-1, accounting for 1.25‰-3.06‰ and 2.17‰-4.96‰ of global river estimations, respectively. The evasion of CH₄ and N₂O in mountainous rivers need further detailed studies, which may revise the global estimation of greenhouse gas emission.

Key words: Poa pratensis, Cluster analysis, Seed yield, Yielding characteristics