贵州石灰岩和砂岩地区C4和C3植物营养元素的化学计量对N/P比值波动的影响

陆地生态系统植物的生长受到营养元素氮(N)和磷(P)的可利用性的限制。已有的证据表明营养元素的相对丰度将控制生态系统的营养元素循环和能量流动的速度。文章提出如下假设:为了适应环境的变化,植物具有可伸缩性地调整营养元素含量的能力,也就是营养元素化学计量比值变化的能力,植物N/P比值波动的影响不仅来源于N对P的相对可利用性的变化,也来源于其他营养元素化学计量的变化,尤其是与Ca的化学计量的变化。为了验证上述假设,本研究利用3种C₄植物和11种C₃植物,研究了植物N/P化学计量比值的波动随N与Ca和P与Ca化学计量的变化模式:对C₄植物来说,N/P比值的波动主要受生物量P与Ca化学计量变化的影响;而对C₃植物来说,则同时受N与Ca和P与Ca化学计量变化的控制,它们之间的相对控制能力的大小将决定植物N/P比值波动的变化梯度,C₄植物和C₃植物的N/P比值的波动都要受土壤pH值的影响。本研究对了解物种丰度和N对P的相对可利用性、N与Ca,以及P与Ca的化学计量之间关系具有重要意义。

VARIATIONS OF C4 AND C3 PLANT N:P RATIOS INFLUENCED BY NUTRIENT STOICHIOMETRY IN LIMESTONE AND SANDSTONE AREAS OF GUIZHOU

Plant growth should be expected to be limited by nitrogen （N） and phosphorus （P） availability in most terrestrial ecosystems. The evidence indicated that N to P relative availability, that is N ∶P ratios, can be used to indicate N or P limitation on plant growth, its variations influence vegetation composition and species richness. To characterize these ecosystem's problems, ecological stoichiometry is being used with increasing frequency. With its increasing use, recent ideas have been appeared that the law of the minimum has a direct connection with chemical stoichiometry of living biomass. For example, C ∶N ratios, an indicator of plant residue quality, and N ∶P ratios, an indicator of N or P limitation on plant growth. The relative abundance of key elements determines the rates of nutrient cycles and energy flows in ecosystems. We tested hypothesis that plants have the ability of plastic adjustments of the nutrient concentrations through stoichiometric regulations in living biomass to be adapted for the changes of environments, and that the shifts of N ∶P ratios should be determined not only by the changes of N to P relative availability, but also by other nutrient stoichiometric regulations, especially Ca, using 3 species of C₄ grasses and 11 species of C₃ plants. The relationship between the shifts of N ∶P ratios and N and Ca, P and Ca stoichiometry have been studied in this paper. The results indicated that the shifts of N ∶P ratios were mainly determined by P and Ca stoichiometric regulations in C₄ grasses, and by both N and Ca, and P and Ca stoichiometric regulations in C₃ plants; the shifts of N ∶P ratios for both C₄ and C₃ plants were, therefore, influenced by soil pH. This paper will be useful for studying the relationship between species richness and N to P relative availability, and N and Ca, P and Ca stoichiometry.