Biomass allocation and growth analysis on the ramets of Phragmites communis populations in different habitats in the Songnen Plains of China
YANG Yunfei, LI Jiandong
2003, (1):
30-34.
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In the Songnen Plains of China, the reeds grow fastest in middle August. In this experiment, four research plots were chosen in the arid habitats. The first plot was dominated by reed, and in which,there was some stagnant water in July and August. The ramets of reeds grew singly, and most of them could turn into reproductive growth. Its community coverage was more than95% after the fast growing season of July. The second plot was Leymus chinensis+Phragmites communis community, where soil was alkaline meadow with stagnant water for a short time or not. Its community coverage was more than90%. Two or three ramets grew in a tuft, while most of them couldn't turn to reproductive growth, so reeds were used to make hay stored in winter every year. The third plot was on Aeolian sandy soil with good permeability and drainage on a grassland of artificial forest edge on sand dune.Its community coverage was about 50%, and two or three ramets grew in a tuft. The last plot was alkaline bareground patches, where top soil was lost completely. Soil was hard and permeability was poor.On some alkaline patches,there could form a micro-community dominated by reed, and eight to twenty ramets could grow in a tuft.Ramets were all slender and creeping stems. Its community coverage was from 20% to 40%. The results showed that four mentioned habitats, the growth and productivity of the ramets of the populations were the largest in the lowland and the smallest in the alkaline patch. The height of ramets differed 2.8 times,and the biomass differed 4.4 times in the two habitats. There were also significant difference between the other two habitats,sand soil and mixed-grass community. The integrated condition of habitat were the major factor that affected the height of the ramets of the population. Moreover, the growth condition of interior habitat was the major factor that affected the ramet biomass of the population in lowland and alkaline patch, while the integrated habitat conditions had much more effects on the ramet biomass of the population in sand land and meadow. The height of ramet was much lower in ecological plasticity than the biomass in every population. The variations of biomass allocation of the ramet in different habitat conditions indicated important strategies in the growth regulation and biomass allocation. More biomass of ramets was allocated to leaves preferentially in the four habitants, especially on sand dune. Reeds in alkaline patch had small ramets and enough growth spaces. There were 63.04% and 53.61% biomass allocated to leaves, and only 14.82% and 19.92% to the stems, although 58.31% was allocated to leaves and only 19.05% to stems to ensure the full material product in the meadow, because of the interspecific competition. But, in the lowland with better conditions where had a higher density and large coverage, only 42.1% were allocated to leaves, while 37.52% were allocated to stem to elongation of stem in order to improve the individual competition for space and light. The leaf sheath/biomass ratio of the ramets was 20.38%～26.47%, which was nearly at the same level in four habitats. There was the same regulation of the heterogeneous speed growth by power function, either in the increased height and weight of the ramets,or in the relative increased weight of the stems, leaves and the ramets of the populations in four different habitat conditions.
