Ecological Characteristics Of 'black Soil Patch' Of Degraded Meadow And Restoring Experiment Of Pelleted Forage Seeds In The Headwater Area Of Yellow River

The process of formation of'black soil patch'degraded alpine meadow is that soil-grass layer disappearing alpine meadow grass carpet layer off to form a bare spot in the headwater area of Yellow river. Investigations and experiments were carried out to assess the vegetation, soil characteristics of 93 different size bare-spots, and value the effect of planting pelleted grass seed on restoration of bare-spots in headwater area of the Yellow River, Tibetan plateau. The main results were as follows:Species richness of bare spot is less than normal meadow communities. The species richness of bare spot is about from 20 to 25, which most are toxic or weed plants. Once bare-patches have formed, the species richness was reduced ,which was only 20 to 25 and poisonous weeds were the main species. Compared with its surroundings, species composition of plant community in bare-patches was very different. And some species did not exist in non-degraded grassland. With increasing bare-patch area, Aconitum pendulum, Carum carvi, Euphorbia fischeriana, Ligularia virgaurea became dominant plants in it.Soil nutrients of bare-patches were lower than that of its surroundings. but some physical and chemical indexes had no significant differences. After bare-patch appeared, its soil nutrients were lower than surroundings. And a'negative fertility island'may form in bare-patch. Data analysis showed that bare-patch area had positive linear correlation with the number of mouse hole. In other words, the hyperactivity of rodents promoted the expainsion of bare-parch and it played an important part in that bare patch changed to black soil patch. Besides, mining activities of rodents accelerated the loss of soil nutrients in bare-patches and it may be the main factor that'negative fertility island'formed.Experiments of planting pelleted seed showed that pelleting significantlly(P<0.01) increased emergence value of seedling of elymus nutans, elymus sibiricus and festuca sinensis in bare-patches. It means that pelleting had some use in restoring bare-patches of alpine meadow. And the experiment provided scientific basis for seeding pelletization used for controlling black soil patch.