Research On The Dynamics Of Biomass And Mineral Elements Of Leymus Chinensis In Grassland Turning Green Period

Leymus chinensis grassland is one of the main grasslands types in northern China, and Leymus chinensis, a primary plant in this grassland, is a very important pasture resource in northern grasslands. Taking the Bashang Leymus chinensis Grassland as an example, the paper studies the dynamics of biomass and mineral elements of Leymus chinensis in grassland turning green period as well as the correlativity between these mineral elements. The research results as follow:During turning green period in Leymus chinensis Grassland, the total biomass of the Leymus chinensis keeps ascending in this duration. After April 26, the increase of biomass enters an accelerated period. It is after May 6 that the over-ground biomass of the Leymus chinensis increases so quickly that shows the inclination of linear increase. The underground biomass keeps increase in whole turning green period.During turning green period, mineral elements(N, P, K etc) begin to keep fall, and then increase in the over-ground part of Leymus chinensis. N, P, K, Mg and Zn decline slowly before April 26. Ca and Fe decline more quickly since April 16.these elements begin to increase from April 26,and the content of N, Mg, K, P and Ca increases more quickly since May 6. The content of Fe and Zn increases very quickly from the beginning. The content of Zn declines quickly again after May 6. The content of N over 45cm maintains the declining inclination in underground rhizotaxy before April 26, and then begins to increase. The content of N in 45cm-60cm keeps decline in whole turning green period. The N content in dead root is higher than the one in living root. The content of P in 0-15cm maintains decline in turning green period, and keep increase in the other layers during turning green initial stages. On May 6, the content of P in each layer begins to fall. The content of P in living root is higher than that in dead root. The content of K, Ca, Mg, Fe and Zn maintains decline before April 26, and then increase.During turning green period, these elements, except for Zn, show significant positive correlation in the over-ground part of Leymus chinensis. The coefficient between K and Fe reaches 1.0 at the 0.01 level. In the underground part of Leymus chinensis, N does not have significant correlation with other six elements, whose correlative coefficient with K is zero. P shows negative correlation with other six elements, and the correlation is the most significant with K at the 0.01 level, whose correlative coefficient is 0.929.there are significant correlation among Ca, Mg, Fe and Zn. When we study the correlation among these elements from whole grassland community , we find that the content of P ,to some extent, limits K, Mg and Fe uptake.