The Bothriochloa Shrub Grass Population Niche Research,

Studies on the niche of population in Bothriochloa ischaemum shrub grassland Abstract Sixteen samples of six hills were investigated. The cluster analysis method had been used to divide the degenerated successional series of the B. ischaemum shrub grassland for grazing. The niche breadths and niche overlaps of main populations on the gradients of soil water, soil pH value, and soil nitrogen content were measured using the formulas described by Shannon-Wiener and Pianka. The results showed that the Wards?minimum variance cluster analysis method was proper to the shrub grassland. The successional series of each community might be divided into five stages, that were light grazing, proper grazing, moderate grazing, serious grazing, and extreme grazing. With the changes of grazing intensity, the dominant status of main plant population would be variance. B. Ischaemum had very high dominant status in each community, and in extreme grazing stage the dominant status was the highest. Thymus mongolicus had higher dominant status in serious and extreme grazing stages. Artemisia vestita had the highest dominant status in proper grazing stage and the lowest dominant status in extreme grazing stage. With the increase of grazing intensity, Carex subpedjformis and Lespedeza inschanica would degenerated, and L. inschanica would disappear at last. Lespedezafloribunda would not be seen in extreme and light grazing stages. Lespedeza dahurica could hold certain dominant status in each community. The average niche breadth of B. ischaemum ,which was greater than other species, was 0.905. L. dahurica had the second average niche breadth. These indicated that B. ischaemum and L. dahurica had the highest capability to endure cold, dry climate of north and defoliated by animals. The higher niche overlaps with other species on three resource dimensions showed that B. ischaemum had strong competed superiority. Potentilla supina had lower niche overlaps with other species and its average niche breadth was only higher than L. floribunda. These showed the lower capability of adapting adversity of P. supina, L. floribunda, and L. inschanica. B. ischaemum and L. dahurica will be the first selected species when the B. ischaemum shrub grassland should be improved.