New Zealand Journal of Agricultural Research abstracts
Effect of annual weeds on the growth of perennial grass mixtures in
the alpine region of the Qinghai-Tibetan Plateau
Wei Xiaohong1,2
Dong Shikui3,5*
Long Ruijun4,5
Hu Zizhi5
Wang Genxuan1
1Key Laboratory of Arid
Agroecology of Ministry of Education
Lanzhou University
Lanzhou 730000
PR China
2School of Life Science and
Technology
Gansu Agriculture University
Lanzhou 730070
PR China
3School of Environment
Beijing Normal University
Beijing 100875
PR China
4Northwest Plateau Institute
of Biology
Chinese Academy of Sciences
810001
Xining, PR China
5Grassland Science College
Gansu Agricultural University
730070 Lanzhou
PR China
*Author for correspondence.
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. A field 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 of
weeds on LAIs of grasses declined and stabilised in the second and
third years. E+B+C, B+E+C+A, and B+E+A+P possessed relatively higher
LAIs (P < 0.05) among all grass combinations and their
LAIs were close to five when the competitive interference of weeds was
removed. Grasses were competitively inferior to weeds in the
establishment year, although their competitive ability (aggressivities)
increased throughout the growing season. In the second and third years,
grasses were competitively superior to weeds, and their competitive
ability decreased from May until August and increased in September. Dry
matter (DM) yields of grasses were reduced by 29.8–74.1% in the
establishment year, 11.0–64.9% in the second year, and 16.0–55.8% in
the third year by the competitive interference of weeds. B+E+C+A and
B+E+A+P can produce around 14 t/ha of DM yields, significantly higher (P <
0.05) than the production of the other grass combinations in the second
and third years after the competitive interference of weeds was
removed. It was preliminarily concluded that removal of competitive
interference of weeds increased the LAIs of all grass swards and
improved the light interception of grasses, thus promoting the
production of perennial grass pastures. The germination stage of the
grasses in the establishment year was the critical period for weeding
and suppression of weeds should occur at an early stage of plant
growth. The grass combinations of B+E+C+A and B+E+A+P were productive
and can be extensively established in the alpine regions of the Tibetan
-Plateau. Two or three growing seasons will be needed before
determining success of establishment of grass mixtures under the alpine
conditions of the Tibetan Plateau.
Keywords competition; growth rate; LAIs; DM yields
A03061; Received 17 October 2003; accepted 20 September 2004; Online
publication date 21 March 2005
New Zealand Journal of Agricultural Research, 2005, Vol. 48:
75–82
0028–8233/05/4801–0075 © The Royal Society of New Zealand 2005
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