中文摘要：

【目的】研究施肥对土壤-微生物-植物系统化学计量学特征的影响,探究土壤-微生物-植被系统的＂内稳性＂,为黄土高原植被恢复提供科学依据。【方法】基于长期试验（2004年开始）,在2种植被恢复系统（自然恢复系统和人工恢复系统）中,设置3种肥力水平（无肥,不施肥;低肥,施用45 000kg/hm^2有机肥;高肥,施用105 000kg/hm^2有机肥）,2015年9月采集2种植被恢复系统中不同处理的土样以及灌木优势种叶片（自然恢复系统中为沙棘,人工恢复系统中为柠条）,分析不同土壤肥力水平下2种土壤-微生物-植物系统碳、氮、磷化学计量比值特征及其相关关系。【结果】在2种植被恢复系统中,随着肥力水平的升高,土壤有机碳、微生物量碳、微生物量磷含量均明显提高;土壤、微生物量及植物叶片C/N总体增加,微生物及植物叶片N/P明显减小。相对于无肥处理,高肥处理下沙棘和柠条群落土壤C/N、C/P、N/P的变化幅度分别为40%,49%,7%和12%,27%,13%;微生物量C/N、C/P、N/P的变化幅度分别为80%,14%,50%和36%,9%,34%;叶片C/N、C/P、N/P的变化幅度分别为10%,23%,14%和40%,9%,31%。相对于自然植被恢复系统,在人工恢复系统中土壤养分与优势灌木叶片化学计量比的相关关系更强。【结论】在坡地侵蚀环境下施肥,可一定程度上提高了土壤肥力水平,改变土壤-微生物-植物系统生态化学计量特征,进而可能改变土壤-微生物-植物系统的物质循环,影响土壤质量演变和植被演替进程。在植被恢复过程中,人工植被恢复系统比自然植被恢复系统能更快建立土壤-叶片养分互馈关联。

英文摘要：

【Objective】The impact of fertilization on stoichiometry and internal stability characteristics of soil-microorganism-plant system was explored to provide basis for vegetation restoration on the Loess Plateau.【Method】Based on a long-term experiment since 2004,three fertility levels（no fertilizer;low fertilizer,45 000kg/hm^2;and high fertilizer,105 000kg/hm^2）were set up in two vegetation restoration systems（natural restoration system and artificial restoration system）.Soil and dominant shrub species samples were collected in September 2015.The dominant shrub species was Hippophae rhamnoides Linn.innatural restoration system and Caragana intermedia in artificial restoration system.Carbon,nitrogen,phosphorus stoichiometry characteristics and the relationship within two soil-microorganism-plant systems were studied.【Result】In the two vegetation restoration systems,there was significant increase in contents of soil organic carbon,microbial biomass carbon and microbial biomass phosphorus with increase of soil fertility level.C/N ratios in soil,microbial biomass and leaf were increased while N/P ratios in microbial biomass and leaf were decreased significantly.After high fertilizer treatment,the changes of soil C/N,C/P,and N/P ratios were 40%,49%,and 7%in Hippophae rhamnoides Linn.community and 12%,27%,and13%in Caragana intermedia community.The changes of microbial biomass C/N,C/P,and N/P ratios were 80%,14%,50% and 36%,9%,34%,while that of leaf C/N,C/P,and N/P ratios were 10%,23%,14% and 40%,9%,31%,respectively.Compared with natural restoration system,there was a stronger relationship between soil nutrients and dominant shrub leaf stoichiometry in artificial restoration system.【Conclusion】Stoichiometry characteristics of soil-microorganism-plant system can be changed by improving soil fertility through fertilization on slope land,then the matter cycling in soil-microorganism-plant system may be altered followed by evolution of soil quality and the vegetation succession.Compared with natural vege