Effect of annual weeds on the growth of perennial grass mixtures in the alpine region of the Qinghai‐Tibetan Plateau

摘要

Abstract In the alpine region of the Tibetan Plateau, five perennial grass cultivars, Bromus inermis (B), Elymus nutans (E), Clinelymus nutans (C), Agropyron cristatum (A), and Poa crymophila (P) were combined into nine communities with different compositions and ratios, B+C, E+A, B+E+A, E+B+C, C+E+A, B+E+C+A, B+C+A+P, B+E+A+P and E+C+A+P. Each combination was sown in six 10 × 10 m plots with three hand‐weeded plots and three natural‐growing plots in a completely randomised design in 1998. Afield experiment studied the performance of these perennial grass combinations under the competitive interference of annual weeds in 3 consecutive years from 1998 to 2000. The results showed that annual weeds occupied more space and suppressed the growth of the grasses due to earlier germination and quicker growth in the establishment year, but this pattern changed in the second and third years. Leaf area indexes (LAIs) of grasses were greatly decreased by the competitive interference of weeds, and the negative effect ...