| The trials with the Old World bluestem (Bothriochloa ischaemum) rangelands were conducted at Qinyuan, Shilou and Heshun county, in Shanxi Province. The studies were carried on the aboveground biomass, regrowth yield of the main forages, rumen degradability of dominant species, the niche of the populations and the cultivation of deteriorated rangelands. It was analysed the plant population structure of the Old World bluestem grasslands. In their growth season, the aboveground biomass of treated plot were determined by artificial harvesting way with every month, and were tested their regrowth yield. Nutrient trend and rumen degradability at different development stages of dominant plant, such as Bothriochloa Ischaemum, Lespedeza davurica, Lespedeza inschanica, Artemisia vestita, Cleistogenes caespitosa were studied old world bluestem grasslands. Sixteen samples were investigated. The cluster analysis method had been used to divide the degenerated successional series of the B. ischaemum shrub grasslands 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 banded improved-pasture of highslop was conducted, and fertilizer on the surface with broadcasting, the tests consisted of 4 treatments: N90fertilizer, P60fertilizer, N90+P60 fertilizer and CK, studying the effects of different fertilizing on the Old World bluestem rangeland. The following is the chief results of this research:1. The kinds of forages on the Old World bluestem rangelands were 22 families, 74 species. There were 26 species in per meter square and the species saturation was large. The trends of aboveground biomass was of unimodal curves in every year, the high-yield season of hay was in August. The regression equation of the aboveground biomass of the Old World bluestem Rangelands (Y) between temperature (X1), precipitation (X2), and relative humidity of air (X3) is : Y= -437.76X1 + 4.99X2 + 420.53X}- 15.04 (R2= 0.7684, P<0.05) . The regrowth character of the forage on the Old World bluestem was strong. The better use of the first cutting was in July and that of the first grazing was in May.2. The Wards' minimum variance cluster analysis method was proper to the shrub grasslands. The successional series of each community might be divided into five stages, which 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. 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. The higher niche overlaps with other species on three resource dimensions showed that B. ischaemum had strong competed superiority.3. The contents of crude protein (CP) and Ash declined gradually, with the passing of development stage, but contrary result appeared with ADF and NDF. CPD of B. ischaemum and C. caespitosa at earemergence were higher than that at blooming stage, but lower in jointing stage. CPD of A. vestita at bud (76.13%), seed pod (67.04%) were higher than that in other stages, and it is beneficial to grazing in seed pod for good palatability.4. The air-dry herbage yield of banded improved-pasture was increased 176.30% ~225.60%(P< 0.01) compared with unimproved rangelands. The cover degree has been increased 41.0%. The surface runoff of the improved pasture reduced by 13.14%, and soil erosion reduced by 28.08%.5. Applying N fertilizer to the rangelands not only promoted the growth of forage grass, but also increases the grass yield. N fertilization increased forage production in Shanxi by an average of 21 kg of dry matter per kilogram N applied up to 90 kg app... |
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