氮添加和放牧对云雾山草原优势种异速生长模式的影响

氮添加和放牧是影响草地生态系统结构和功能的重要因素。本研究以宁夏云雾山典型草原为研究对象，采用标准化主轴估计和异速生长分析，探究了氮添加和放牧干扰对草地群落中7种优势植物根、茎、叶不同构件的生物量分配对策和异速生长模式（包括异速生长斜率和截距）的影响。结果表明：在封育地，氮添加处理显著提高了物种的叶生物量；而在放牧地，氮添加则使得物种的根生物量上升，而茎、叶生物量下降；植物各营养器官生物量均随植物个体生物量的增加而增加，且只有在放牧×氮添加处理下植物叶生物量与个体生物量之间的异速生长斜率和截距发生了显著改变，其余处理下植物的异速生长斜率均无明显差异。因此，植物营养器官的生物量分配主要依赖于植物个体大小，而氮添加和放牧对植物异速生长模式的影响相对较小。

Effects of Nitrogen Addition and Grazing on Allometric Growth of Dominant Plant Species in Grassland in the Yunwu Mountains

Nitrogen addition and grazing are two important factors affecting the structure and function of grassland ecosystem. It is vital to study the biomass allocation pattern of grassland species for restoration and adaptive management of degraded grassland. This study selected a grassland in the Ningxia Yunwu Mountains as the research area. We measured the biomass of seven dominant species at individual and organ scales in grassland communities with disturbance by nitrogen addition and grazing, and used Standardized major axis regression (SMA) and allometric analysis to study biomass allocation and allometric growth patterns of these species. The results showed that:1) Nitrogen addition significantly increased the leaf biomass of species in enclosed grassland. However, nitrogen addition shifted the biomass allocation from aboveground to belowground in grazed grassland, and the root biomass increased, while the stem biomass and leaf biomass decreased specifically. 2) The biomass of each plant vegetative organ increased with the increase of plant individual biomass. Only the allometric growth slope and intercept of plant leaf biomass changed under nitrogen addition×grazing treatment, while the allometric growth slope of the others did not differ significantly. Therefore, the biomass allocation pattern of plant vegetative organs mainly depended on the individual plant size, and the effect of nitrogen addition and grazing on the allometric growth pattern of plants was relatively small.