| Community dynamics of alfalfa grassland of abandoned lands in the upstream area of Shiyang Rive |
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| DOI：10.7606/j.issn.1000-7601.2011.04.42 |
| Key Words: alfalfa abandoned land community dynamics functional group upstream area of the Shiyang River |
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| Abstract: |
| In order to study the degradation process and community dynamics of alfalfa (Medicago sailva) grassland in the alpine areas of NW China, we surveyed alfalfa grassland communities in the Hanquangou valley in the upstream area of the Shiyang River from 2003～2009. The results showed that, the community coverage decreased, the community density increased, the aboveground biomass varied with the single peak curve during planting the alfalfa. With the weeds invading grassland communities, the number of species increased from 7～17 during 7 years, and the Compositae species took dominant proportion. Alfalfa showed natural thinning after 5 years, the grassland quality declined, so parts of the alfalfa grasslands lost utilization value, and Leymus secalinus become the dominant species. The degradation process of alfalfa grassland could be divided into three stages, i.e., alfalfa grassland stage (2003～2004), transitional stage from alfalfa grassland to natural grassland (2005～2007), and secondary natural grassland stage dominated by grasses (2008～2009), they indicated early phase, medium phase and late phase, respectively. |
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