紫花苜蓿生物量分配对植物-土壤化学计量的响应

C∶N∶P化学计量学在植物-土壤养分分配研究中应用广泛，但如何运用化学计量学方法来探究植物地上地下生物量分配还需要进一步研究。本研究选取榆林地区种植1 a, 3 a, 5 a, 7 a和9 a的紫花苜蓿(Medicago sativa L.)人工草地，测定了紫花苜蓿的地上、地下生物量，土壤理化性质及碳氮磷含量，分析了植物-土壤C∶N∶P化学计量特征及其对紫花苜蓿地上、地下生物量和根冠比变化的响应。结果表明，紫花苜蓿人工草地土壤C∶N,C∶P和N∶P随种植年限延长均而增加，紫花苜蓿植株C∶N,C∶P和N∶P随种植年限延长均呈现先增加后降低变化趋势。种植1～5 a紫花苜蓿种植受N限制，种植7～9 a紫花苜蓿受P限制，紫花苜蓿通过增加自身根冠比来应对日益增强的N∶P,同时庞大的根系使得土壤肥力得到改善。

Response of Alfalfa Biomass Allocation to Plant-Soil Stoichiometry

C:N:P stoichiometry is widely used in plant-soil nutrient partitioning studies,but how to use stoichiometry to investigate plant above- and under-ground biomass partitioning needs further study. In this studies,the above- and under-ground biomass,soil physicochemical properties and carbon,nitrogen and phosphorus contents of alfalfa were determined by selecting an artificial farmland of alfalfa cultivated in Yulin region for 1,3,5,7 and 9 years. The plant-soil C∶N∶P stoichiometric characteristics and their responses to changes in above- and below-ground biomass and root-shoot ratio of alfalfa were analyzed. The results showed that the C∶N,C∶P and N∶P of soils of the artificial farmland increased with the extension of alfalfa planting years,and the C∶N,C∶P and N∶P of alfalfa showed a trend of increasing and then decreasing with the extension of their growth years. Planting for 1 to 5 years,the alfalfa growth is limited by N,planting for 7 to 9 years,the alfalfa is limited by P. Alfalfa may adapt the enhanced N∶P ratio of soil by increasing its own ratio of root to shoot,while the enlarged root system makes the nutrient utilization improved at a degree of soil fertility.