施肥对羊草草原土壤氮素转化的影响

ttttt目的ttttt养分添加是牧草生产管理的一种重要措施，为探讨施用磷对豆科牧草生长生产特征及地上—地下资源分配模式的影响。ttttttttttttt方法ttttt以优良豆科牧草柱花草为研究对象，设计正常施磷及不施磷对比试验，探讨磷对干热河谷条件下5个柱花草品种地上—地下生物量间关系的影响。ttttttttttttt结果ttttt(1)施磷促使5个柱花草品种平均磷含量显著增加(P<0.05)，同时增加柱花草的地下生物量、地上生物量和总生物量，表明磷添加对干热河谷柱花草的促生效果明显；伴随土壤磷含量的增加，柱花草根冠比减小，表明施磷导致柱花草对地下的资源分配减少。(2) 5个柱花草品种在土壤正常施磷及不施磷条件下，地上—地下生物量间关系主要呈现为等速生长关系，即5个柱花草品种地上—地下生物量在不同土壤磷水平保持相对稳定的生长模式，表明柱花草具有较好的磷耐受能力。相较而言，热研7号柱花草及热研13号柱花草对磷的施用较为敏感，为非低磷耐受品种。(3)干热河谷气候施磷、不施磷条件下，品种水平柱花草的地上—地下生物量间关系主要呈现为等速生长关系，但整体水平呈现为显著的异速生长关系，满足lnU_mass=ln1.555+0.510lnB_mass，造成生长模式差异的主要因素来自品种的差异。tttttttttttttttttt结论ttttt本研究结果提示：柱花草具有在正常施磷和不施磷条件下保持相对稳定生长模式的磷适应能力，正常施磷和不施磷对柱花草品种间差异的影响大于对品种内的影响；磷添加对干热河谷柱花草种植具有明显的促生效果，因而磷添加可作为干热河谷柱花草生产的重要管理手段，在生产中应对不同的柱花草品种进行筛选，同时设置相异的施磷栽培措施。tttt

Bivariate line-fitting methods for allometry

tttttPurposetttttNutrient addition was an important measure in forage production practice, and the aim of this study was to observe the influence of phosphorus (P) addition on the changes between aboveground and underground biomass of Stylosanthes in dry-hot valley.ttttttttttttttttttMethodtttttFive Stylosanthes varieties were plotted under traditional P addition and no P addition levels and the traits were measured in the dry-hot valleys (DHV).ttttttttttttttttttResultttttt(1) Traditional P addition level made P content, underground biomass, aboveground biomass and total biomass of five varieties average increased significantly (P<0.05). The root-shoot ratio decreased with soil P addition, showing that phosphorus could improve the growth ofStylosanthes in dry-hot valleys by allocation less biomass to underground. (2) The five varieties above-underground biomass mainly appeared as an isomeric growth relationship under the condition of P addition or no P addition. Compared with the other varieties, S. guianensis cv. Reyan No.7 and S. guianensis cv. Reyan No.13 easily changed under the condition of P addition or no P addition, showing a lower tolerance to phosphorus. (3) The above-underground biomass showed an isomeric growth relationship to varieties level, but an allometric growth relationship and shared a common pattern of lnU_mass=ln1.555+0.510lnB_mass, the distinguish traits of varieties played a key factors in the shift.ttttttttttttttttttConclusiontttttThis conclusion suggests that 5 Stylosanthes varieties are adaptor to the climate dry-hot valley. At the same time, results of P addition improving the Stylosanthes growth significantly show that phosphorus additions could be used as an important management measure in dry-hot valleys’ Stylosanthes production, under a variety selection of adaptation and a certain soil P addition.ttttttttt