【摘要】 多年冻土的发育是青藏高原冻土区生态系统稳定的基础,而多年冻土退化效应是目前青藏高原研究的热点。研究了青藏高原北部多年冻土退化过程中生态系统的变化特征。结果表明:在多年冻土退化的过程中,土壤温度逐渐升高,土壤含水量下降,有机质含量降低,植被类型表现为从沼泽化草甸演替为典型草甸,草原化草甸,最终成为沙化草地,群落植物组成从湿生或中湿生逐渐向中生、中旱生乃至旱生转变,草层高度变矮,植被盖度下降,α和β多样性均表现为先增加后减小,在草原化草甸阶段达到最大;草地植物生物量和载畜能力总体表现为降低趋势,但在典型草甸和草原化草甸之间差异不显著。植被经济类群的变化趋势表现为优良的莎草科和禾本科牧草比例下降,而毒杂草比例显著增加,牧草品质下降,饲用价值降低。更多还原

【Abstract】 Effect of permafrost degradation on grassland ecosystem has aroused interests in the scientists due to influence the processes of ecology in the permafrost regions of Qinghai-Tibetan Plateau.To gain insight into the contribution of permafrost degradation to the stability of grassland ecosystem,there is an urgent need to study the properties of grassland ecosystem in the succession stages due to degradation of frozen soil.A survey of plant vegetation was undertaken during 2003 and 2004 along the Qinghai-Tibetan Highway from Kunlunshan(94°04’ 46 ″E,35 38’ 51″ N)to the southern Tanggulashan Pass(33°07.120’E,91°52.670’N),to study the properties of grassland ecosystem in the successional stages from marsh meadow,alpine meadow and steppe meadow to desert steppe due to permafrost degradation.Fifty-five spots were selected in the successional community series.Each plots were arranged with three replicates.In each subplot,all plant species present were counted,and coverage,height(50 plants)and frequency were recorded.Biomass was measured by harvesting and drying.The species diversity of the plant communities was calculated using the Shannon-Wiener(diversity)index(H),the Pielou(evenness)index(J),and richness index(species number)(S).Three soil samplings at 0-20 cm layer were collected to analysis the soil organic matter content.Soil water and temperate were measured.Accompanying by permafrost degradation,plant species in communities transferred from wet plants in marsh meadow to drought plants in desert steppe,and height and coverage of plant communities decreased,and the richness species index(S)was not significantly different among the successional communities series,whereas evenness index(J)and diversity index(H)were significantly different(P<0.05),indicating that they first decreased and then increased,peaking in the steppe meadow.In the successional series resulted from permafrost degradation,biomass and carrying capacity generally decreased,however,they were not significantly different between alpine meadow and steppe meadow.Economic value of plants decreased,and weeds in plant communities increased in the sucessional series.Accompanying by the process of frozen soil degradation,soil temperate at 0-20 cm layers increased,however,soil moisture and soil organic matter reduced.These implied that permafrost degradation was disadvantageous to stability of grassland ecosystem in the permafrost regions of Qinghai-Tibet Plateau.更多还原