5种荒漠短命植物养分再吸收对水氮添加的响应

人类活动和全球气候变化导致的大气N沉降升高和降水格局的变化,将会影响植物-土壤系统的养分循环。研究了5种荒漠优势短命植物在N添加和增加降水处理下,叶片N、P含量变化及叶片N、P的再吸收特征。结果表明:自然情况下,荒漠植物叶N、P含量相对较高(平均值分别为30.1 mg·g^-1、3.6 mg·g^-1),而叶片N:P很低(6.8~10.5);荒漠短命植物叶N再吸收率(NRE,34.08%)低于P再吸收率(PRE,73.03%);叶片养分含量和再吸收率在物种间的差异极显著;N添加对NRE和PRE没有显著影响;N添加使尖喙牻牛儿苗(Erodium oxyrrhynchum)、条叶庭荠(Alyssum linifolium)和卷果涩荠(Malcolmia scorpioides)N再吸收度(NRP)减小,使丝叶芥(Leptaleum filifolium)和齿稃草(Schismus arabicus)的NRP增加,对P再吸收度(PRP)影响很小。不同含量N添加处理对NRE没有显著影响,但对PRE具有显著影响;增加降水对NRE具有显著影响,使NRE增加(丝叶芥除外),对PRE、NRP和PRP没有显著影响,但PRE和NRP增加,PRP变化很小;N添加和增加降水对NRE没有显著交互作用,对PRE具有显著交互作用,但其变化因物种而异。总之,N输入增加和降水格局的变化,显著改变了荒漠短命植物养分状态及再吸收特征,这将对短命植物群落组成及所处荒漠生态系统养分循环产生重要影响。

Responses of Nutrients Resorption of Five Desert Ephemeral Plants to Water and Nitrogen Additions

Increasing atmospheric nitrogen deposition and changing precipitation pattern due to anthropogenic activities can affect nutrient cycling of the plant-soil system. This study focused on the effects of simulative increases in nitrogen and precipitation on foliar N and P concentrations, resorption efficiency and proficiency in five dominant desert ephemeral species. Foliar nutrient concentration and resorption efficiency differed significantly among species. The averaged leaf nitrogen and phosphorus concentrations across five desert ephemeral plants were 30.1 mg·g^-1 and 3.6 mg·g^-1 respectively, and the N:P ratio ranged from 6.8 to 10.5. The average leaf nitrogen resorption efficiency (NRE, 34.08%) was lower than the phosphorus resorption efficiency (PRE, 73.03%); N addition had no significant effects on PRE and NRE; N addition reduced the nitrogen resorption proficiency (NRP) of Erodium oxyrrhynchum, Alyssum linifolium and Malcolmia scorpioides, increased the NRP of Leptaleum filifolium and Schismus arabicus, but had little effect on the phosphorus resorption proficiency (PRP). Different levels of N addition had significant effects on PRE rather than NRE; Meanwhile, Water addition significantly increased NRE (except for L. filifolium), but had no effects on PRE, NRP and PRP, yet the PRE (except for E. oxyrrhynchum) and NRP increased as well, the PRP changed little; N significantly interacted with water to affect PRE but did not affect NRE, and the changes of PRE were different among species. These results suggest that increased nitrogen input and precipitation can significantly affect the nutrition status and resorption processes of desert ephemeral plants, which will have an important effect on species composition of the ephemeral plant community and nutrient cycling of the desert ecosystem.