Study On The Types And Grade Partition Criterion Of "Black Soil Type" Degraded Grassland In The "Three-River Headwaters" Region

Field investigation was roundly implemented on the 52 types grassland of 7 groups in 3 subformations of the alpine meadow in the"Three-River Headwaters"Region. The criterion classification for the alpine meadow degraded grassland and types and grade criterion of were elicited by using quantitative classification (TWINSPAN) and the DCA (Detrended Correspondence Analysis) sort-ing method.Meanwhile the most plant community and succession sequence of"black soil type"degraded grassland were studied .Also the characters of community and soil chacacters in the different degraded grassland were studied, the resume measures of the different types and degraded of"black soil type"degraded grassland were also concluded by reading correlated literatures.The results were follows:First: Quantitative classification to the alpine meadow degraded grassland in the"Three-River Headwaters"Region basiced on the index of eximious pasture proporation, esculent pasture proporation, proterozoic vegetation cover, degraded indication species proporation, bareland cover, jeopardize of rodent and organic matter proporation were studied, the result showed that there were five degraded levels of the alpine meadow in the"Three-River Headwaters"Region. The index of bareland cover, esculent pasture proporation, jeopardize of rodent,the proporation of degraded indication species and organic matter proporation could explain status of the degraded grassland with proportion of 98.769% .So we could establish the degraded criterion of the alpine meadowni the"Three-River Headwaters"Region. In practical application the index of bareland cover, esculent pasture proporation and degraded indication species proporation can differentiate status of the degraded grassland conveniently and veraciously.Second: The"black soil type"degraded grassland could be compartmentalized three types by gradient: bottomland(gradient range form 0°to 7°), slowgoing-sloping(gradient range form 7°to 25°) field and steep sloping field(gradient beyond 25°).Each type was divided into light"black soil type"degraded grassland, middle"black soil type"degraded grassland and Heavy"black soil type"degraded grassland by bareland cover and esculent pasture proporation.The bareland cover was 40 percent to 60 percent in light"black soil type"degraded grassland and 60 percent to 80 percent in middle"black soil type" degraded grassland, while it was above 80 percent in Heavy"black soil type"degraded grassland. The esculent pasture proporation in light"black soil type"degraded grassland was 10 percent to 15 percent, but only 5 percent to 10 percent in middle"black soil type"degraded grassland .It was less than 5 percent in Heavly"black soil type"degraded grassland.This paper suggested that the measures of fencing and establishing artificial grassland should be taken in order to resume the productivity of the degraded grassland.Third:The main plant community of"black soil type"degraded grassland were: Lingularia virgaurea and Aconitum pendulum, Polygonum sibiricum and Potentilla anserine, Artemisia frigida and Microula pseudotrichocarpa, Polygonum sibiricum and Pedicularis kansuensis, Morina chinensis, Aconitum pendulum. The succession sequence of"black soil type"degraded grassland were form Kobresia to Poa to Poa and weeds to weeds to noxious plant community.Forth: Upground vegetation and soil nutrient varied obviously during the degraded prosess of alpine meadow. And the jeopardize of rodent is rampancyly, plant diversity decreases rapidly.The herbage yield was only 13 percent of undegraded grassland, vegetation cover was 45 percent, 60 percent to 80 percent of its plant species were noxious plants,the nutrient and soil organic matter decreased heavily.Those noxious plants had no value to the grassland stockbreeding and threatened the health of ecosyeterm arrounding.