基于TWINSPAN分类的三江源区称多县高寒草甸退化研究

采用双向指示种分析法(two-way indicator species analysis,TWINSPAN),选择了植被盖度、优良牧草比例、毒杂草比例、地上生物量变化值、0～25cm土壤有机质含量变化值5项与草地退化最密切相关的植被与土壤指标,对2009年称多县高寒草甸样地调查数据和退化情况进行了分析.结果表明:称多县高寒草甸退化状况可以分为6个类,及未退化、轻度退化、中度退化、重度退化和极度退化5个退化等级.在调查的63个样地中未退化样地16个,约占25%;中度退化样地25个,重度退化样地13个,中度和重度退化样地占60%左右;轻度退化样地7个,约占11%;极度退化样地2个,约占3%.随着退化等级的加重,植被盖度和优良牧草比例逐渐减少,毒杂草比例逐渐增大;地上生物量在未退化时最高,然后减少,到中度退化阶段地上生物量上下浮动,到重度退化时地上生物量明显下降;土壤有机质含量在未退化时最高,在中度退化和重度退化阶段土壤有机质上下波动幅度较大,在重度退化以后土壤有机质含量明显降低.

Research on alpine grassland degradation in the Three-river Headwaters Area based on TWINSPAN classification

The degradation levels in 2009 of alpine grasslands in Chengduo County,belonging to the Three-river Headwaters Area,were studied by using the TWINSPAN(two-way indicator species analysis) method.Among which five indicators,such as vegetation coverage,proportion of good pasture,proportion of poisonous weeds,aboveground biomass values and organic matter content value from 0 to 25 cm soil,were selected for evaluating.The investigation results showed that the alpine grasslands in Chengduo County could be divided into six categories and five degradation grades,no degradation,slight degradation,moderate degradation,severe degradation and utmost degradation.Among 63 sample plots,there were 16 no degradation plots,accounted for 25 %;25 moderate degradation plots,13 severe degradation plots,moderate degradation and severe degradation plots accounted for 60 %;7 slight degradation plots,accounted for 11 %;2 utmost degradation plots,accounted for 3 %.With the increasing of degradation severity,vegetation coverage and the proportion of desirable forage decreased,the proportion of toxic weeds increased.Aboveground biomass was the highest in the non-degraded stage,then reduced and fluctuated at moderate degradation stage,and decreased significantly in severe degradation stage.Soil organic matter content was the highest in non-degraded stage,then fluctuated greatly in the moderate and severe degradation stage,soil organic matter content reduced significantly in severe degradation stage.