Research On Limiting Factors Of Plant Growth In Lawu Mine

Mining development has not only brought economic benefits for us, but also influenced the ecological environment at the same time. The ecological environment in Tibet is very fragile. As a result good balance of the development and utilization of mineral resources and vegetation restoration is very important. Therefore, the research on plant growth limiting factors in mining area is of great significance mining for Vegetation restoration and construction in Tibet.This research chose Dangxionlawu Mining Area as the study object in middle Tibet, using research methods including plant investigation, the collection and analysis of meteorological data and soil sample, mining substrate analysis, cultivation experiments of elymus dahuricus, and seed treatment.The research shows that the main herbage in Lawu Mining Area are in total 17 species including Kobresia pygmea, Oxytropis pauciflora, Carex microfilea, Taraxacum officnala, Potentilla anserine, Kobresia pygmea and Poa alpine. Temperature and precipitation are the limiting factors for plant growth in Lawu mining from the meteorological data.The niche breadth and important values of different kind of communities showed that: the Kobresia in Kobresia community, Sabina procumbent has the most value; the leaflet Rhododendron in its community has the most value; the poa crymophila in the weeds community in the tailings pond has the most value. In the 3 vegetation types, the niche width of Kobresia, Sabina procumbent, potentilla bifurca linn, Elymus nutans and Potentilla fruticosa is comparably large, and potentilla bifurca linn and Elymus nutans covered widely.By determining the four kind of heavy metal elements, we could conclude that the rank average value of one-factor pollution index is that: Cd > Cu > Zn > Pb, in which Cd,Cu,Zn is in heavy pollution. The result shows that the wasteland in mining area is complex pollution of Cd,Cu,Zn.Through the determination of soil nutrients and critical value in mining area, we could conclude that the soil organic matter content there was comparably lower, and the content of P element is very low, the content of Ca, Fe, Mg, K, Zn, Cu was relatively abundant; other nutrients were obviously lower than 3 times of Critical value in nutrient deficiency. We concluded initially that the elements of P, S, B, Mn and N are possibly the limiting factors of soil nutrient.The fertility analysis of soil samples in the mine showed that after the rain erosion and exploitations, the soil matrix and mineral nutrition was low resulting in the poor overall fertility. Organic matters and quick-acting P, N were the limiting factors of soil fertilityBy the systematic research of soil nutrients, we can judge that the order of soil nutrients defeciency is P>B>N>Mo>Mn>S, in which P, B are the first limiting factors, while N is the second limiting factor.The moisture absorption experiments of elymus dahuricus showed that the moisture content of seed and temperature, limited the seed germination of elymus dahuricus to a certain extent. While the light and dark conditions experiments of elymus dahuricus showed that, to some extent light can promote the germination of elymus dahuricus seeds.From the variance analysis of adding nutrient solution, water retention agent and the water experiments, we can see that the original solution can influence the height of elymus dahuricus. By comparing the dry matter, we found that the treatment of "0.25L +0.75 original solution +100 g water retention agent,"can mostly influence the dry matter of elymus dahuricus.