Study On Distribution Characteristics And Vegetation Succession Rules Of Black Soil Beach In Maqu Gassland

Black soil beach, an extreme degradation style of alpine meadow, has become an important disaster endangering Qinghai-Tibetan plateau ecology, human production and living. To solve the current status that the definition and classification of black soil beach are relatively disordered and the fact that there is no in-depth study on causes and succession rules of this special natural entity, we investigated and studied its distribution characteristics and vegetation succession rules according to natural properties and utilization status of Maqu grassland. The major results are as follows:1. We suggest a new definition on "black soil beach "of alpine meadow based on reference resources of "black soil beach" context of situation, parse of acceptation and study on the entity characteristic of Maqu "black soil beach": The black soil beach is a kind of special grassland landscape in a given spatial and temporal range due to extreme sparsity of grassland vegetation or complete exposition which results from integrated effects of natural and artificial factors in alpine meadow. The basic characteristic is that: the total vegetation coverage is below 50%, or the sum of black soil patch areas is above 20% in the region.2. The black soil beach of Maqu grassland can be separated into six types: over-grazing, overgrazing and rodent damage, reclamation, pen of livestock, lake and pond, and soil and stone, according to its causes of formation. We confirmed distribution range and area of different kinds of "black soil beach": The total area of the first four types of black soil beach is 0.39 million hm~2, account for 83.94% of the total black soil beach area, and they are mainly distributed in winter and spring pastures and are major body of black soil beach in Maqu grassland. The distribution and area of lake and pond type depended on the variation of annual precipitation and its interannual and seasonal variation is bigger; and the distribution and area of the soil and stone type presents an increasing trend.3. Some basic characteristics of "black soil beach" are studied from aspects below in Maqu grassland: The proportion of black soil patch, vegetation cover, biomass proportion, living root biomass, soil water content and PH value are employed to describe the seasonal landscape characteristics and interannual variation characteristics of different black soil beach types.4. The study on over-grazing and rodent damage black soil beach mainly in terms of variation in plant diversity and functional groups indicates that: species diversity is significantly and positively correlated to succession years, and biomass and succession gradient present a unimodal relationship. As the succession years increase, number of annual species exhibits a decreased trend, numbers of grasses, sedges and forbs all present increased trends, but the increase magnitude of sedges is not big, whereas the increase of forbs number is sharp. Functional groups of herbage quality also vary as the succession years increase: inferior herbage biomass presents a decline trend in community, both medium and excellent herbage biomass exhibit significant increase trends and good herbage biomass peaks between four to five years of succession.