中文摘要：

碳（C）、氮（N）、磷（P）生态化学计量比是生态系统过程和功能的重要特征。为探究云雾山天然草地30年恢复演替过程中不同封育年限植物和枯落物的全碳、全氮和全磷含量及其生态化学计量特征变化规律,以云雾山封育1、12、20、30年的天然草地为研究对象,通过典型样方调査研究了黄土高原不同封育年限植物和枯落物养分变异特征。结果表明：不同封育年限间,植物地上部分C∶N、C∶P、N∶P比变化范围分别为24.91～37.37、380.1～562.1、12.14～15.86,均值分别为32.51、473.6和14.64;枯落物C∶N、C∶P、N∶P比变化范围分别为37.18～47.11、755.5～885.9、16.41～22.31,均值分别为40.71、819.9、20.30。植物地上部分C、N、P含量间呈极显著相关（p〈0.01）;植物地上部分P含量与C∶N、C∶P、N∶P呈极显著负相关（p〈0.01）,与枯落物C、P、C∶P、N∶P呈极显著相关（p〈0.01）。云雾山植物N∶P比介于14～16之间,植物生长受氮磷共同限制,建议增加草地氮、磷肥的使用量。该研究结果有助于进一步了解云雾山草地C、N、P在不同组分间的相互作用规律与机制。

英文摘要：

【Objective】Balance between various elements in the ecosystem has been a focus or a hotspot of the researches on ecology and biogeochemical cycles under global change. Ecological stoichiometry is a science that combines some basic principles of biology,physics and chemistry,explores for balance of energy and balance of various chemical elements in biological systems and provides an integrated approach to investigating rules of the behaviors of various elements in biogeochemical cycling and ecological processes and their stoichiometric relationships. Ecological stoichiometric ratios of C,N and P are important characteristics of the process and function of an ecological system. 【Method】In order to explore variation rules of the contents of organic carbon,nitrogen and phosphorus in shoots and litter of plants and C∶N∶P stoichiometry characteristics during various enclosure phases of the 30 years of restoration and succession process of natural grasslands in the Yunwu Mountain,typical quadrats of grassland that had been enclosed for restoration for 1,12,20 and 30 years were set up for analysis of nutrient contents in shoots and litter of the plants in the grasslands and their relationships with enclosure age in the Loess Plateau. 【Result】Results showed that carbon,nitrogen and phosphorus contents in shoots and little of the plants and their stoichiometry varied sharply with enclosure age. Carbon,nitrogen and phosphorus content varied in the range of 388.1～437.6 mg g^-1,12.13～15.42 mg g^-1 and 0.78～1.06 mg g^-1,being 418.0 mg g^-1,13.16 mg g^-1 and 0.92 mg g^-1,on average,respectively in shoots of the plants;and in the range of 402.7～427.2 mg g^-1,8.58～11.04 mg g^-1 and 0.49～0.56 mg g^-1,being 411.3 mg g^-1,10.34 mg g^-1 and 0.53 mg g^-1 on average,respectively;and C∶N,C∶P and N∶P ratio in the range of 24.91～37.37,380.1～562.1 and 12.14～15.86,being 32.51,473.6 and 14.64,respectively,in shoots of the plants,and in the range of 37.18～47.11,755.5～885.9 and 16.41～22.31,being 40.