松嫩平原水淹恢复演替过程中羊草无性系种群构件的年龄结构

Age structures of modules on Leymus chinensis clonal populations in the process of restoration succession after the flooded meadow in the Songnen Plains, China

对松嫩平原羊草草甸水淹恢复演替过程中不同大小羊草无性系斑块的种群构件年龄结构进行了研究。结果表明 ,羊草种群分蘖株在斑块中心由 4个龄级组成 ;最外圈层由 3个龄级组成。根茎在斑块中心和中间圈层均由 2～ 4个龄级组成 ,最外层由1～ 2个龄级组成。潜在种群冬性苗和分蘖节芽总量各圈层均由 4个龄级组成。斑块中心的分蘖株种群为稳定型年龄结构 ,向外发展至增长型年龄结构。根茎长度和潜在种群在各圈层均呈增长型年龄结构。在水淹羊草草甸的恢复过程中 ,不同大小羊草无性系斑块均呈不断扩展的趋势。在生存空间充足时 ,羊草的分蘖节在一个生长季里可以繁殖多个世代。

Research on age structure is an important part of population ecology. Dynamics of population and community can be predicted based on age structure. By using the method of dividing age classes of perennial rhizome grass according to vegetative propagation generations of tiller nodes, the age structures of Leymus chinensis clonal population modules were studied in the process of restoration succession of the flooded L. chinensis meadow,and the restoration process of the flooded succession was forecasted in the Songnen Plains of China. L. chinensis is a typical clonal plant with vigorous vegetative propagation. The seeds in soil seed banks germinated at different time and formed unequal approximate circular clonal patches, which distributed in Carex duriuscula community in the process of restoration succession of the flooded L. chinensis meadow in the Songnen Plains of China. Five classes of independent clonal patches whose radius were 10 m, 5 m, 3 m, 1 m and 0.5 m, from the biggest to the smallest, were chosen with three replicates, respectively. Two classes of smaller patches were divided averagely into two circles from the centers to the edges, while three circles were divided in three bigger patches in the same way respectively. Three samples, with area of 0.25 m×0.25 m, were taken in every circle. Divide age classes of samples and analyze data. The tillers consisted of four age classes in the center of every patch and did three age classes at the edge in L. chinensis population. The tillers of 1st and 2nd age classes accounted for 58.3%～68.8%, 65.2%～94.1% and 85.5%～94.1% in the center of the patches, in the middle and at the edge. Their averages and standard deviations were 63.5%±3.85%, 79.1%±14.48% and 91.6%±3.64%, respectively. Namely, the percentage of 1st and 2nd age classes increased gradually from the center to the edge of every patch in age spectrum. Age structures of the tillers were stable in the center of every patch and would be expansive with the growth of patches. Surplus space was decreasing with gradual increase of the tillers in inner patches while the edge of clonal patches expanded from the center of 0.5 m radius patch to 5 m, thereby L. chinensis population would become dominant species in the community. The rhizomes consisted of two to four age classes in the center of every patch and in the middle, while one to two age classes at the edge. The rhizome length of L. chinensis population was expansive age structure in every circle. The growth of rhizome accorded with the expansion of clonal patches. Potential population, i.e. total winterness seedlings and buds of tiller nodes, consisted of four age classes in every circle. 0 age classes were predominant in four age classes. The percentages of 0 age class were 27.6%～35.5%, 33.2%～41.2% and 31.6%～42.9% in the center, in the middle and at the edge of the patches. Their averages and deviations were 33.1%±3.1%, 36.4%±4.2% and 36.8%±5.0%, respectively. Namely, the percentage of 0 age class increased in age spectrum gradually from the center to the edge. The potential populations were expansive age structures in every circle, and presented expansive tendency from the centers to the edges of different radius patches, respectively. The number of potential population approached or achieved and even surpassed the present parental tillers in mid August. It still would increase gradually until the end of September, about forty days prior to dormant period. Seeds in soil seed banks were crucial to L. chinensis population continuity in the process of restoration succession of the flooded meadow in the Songnen Plains. Tiller nodes of L. chinensis could propagate several generations in one growing season if survival space was enough. Rhizome ages were their actual longevity. The process of succession could be predicted through rhizome age structures.