增温和氮素添加降低荒漠草原多年生植物氮素回收效率

植物营养器官在枯萎过程中将部分氮素转移到储藏组织之中,是植物适应生境的重要策略。以位于内蒙古荒漠草原的增温和添加氮素的交互试验为平台,对建群种短花针茅(Stipa breviflora)以及优势种无芒隐子草(Cleistogenes songorica)、银灰旋花(Convolvulus ammannii)、冷蒿(Artemisia frigida)和木地肤(Kochia prostrata)等5种多年生植物绿叶期和枯叶期氮浓度,以及氮素回收效率进行了研究。结果表明:增温处理下,植物绿叶期和枯叶期的平均氮素浓度提高了5.5%和11.3%,氮素回收效率显著降低了7.0%。氮素添加使绿叶期植物氮浓度显著提高了5.2%,使植物氮素回收效率降低2.9%。增温和氮素添加对植物枯叶期、绿叶期氮浓度和氮素回收效率有显著的交互作用。氮浓度和氮素回收效率对增温和氮素添加的响应在5个物种间都有显著差异,即这种响应具有物种特异性。研究表明独立的增温和氮素添加以及两者的交互作用都降低该荒漠草原生态系统中植物氮素回收效率,这些结果将为气候变化条件下荒漠生态系统氮素回收效率变化趋势的预测提供数据支持和实验证据。

Nitrogen resorption efficiency of perennial plant decreases with warming and nitrogen addition in desert steppe

When vegetative organs of plants wither, the nutrient resorption from senescing tissues to storage tissues was the most important adaptative strategy in different growing environments. The nitrogen concentration in green, senescent stages and nitrogen resorption efficiency (NRE) in 5 perennial dominant species were evaluated in a manipulative experiment conducted in Stipa breviflora desert steppe, Inner Mongolia, with treatments of warming, nitrogen addition and its interaction. The results showed that warming significantly increased nitrogen concentration in green and senescent plants by 5.5% and 11.3%, respectively, and decreased NRE by 7.0%. Nitrogen addition significantly increased nitrogen contents in green plants by 5.2% and decreased NRE by 2.9%. There was significant interaction between warming and nitrogen addition to increase nitrogen concentrations of green and senescent plants and to reduce NRE. The nitrogen concentration and NRE of the five species showed higher species-specific responses in different treatments, these species-specific responses reflected flexible adaptation of the plants to environment change. This research indicated that independently warming and nitrogen and its interaction decreased plant NRE in desert steppe ecosystem. These results will provide data support and experimental evidence in predicting the trend of NRE of desert ecosystem under climate change.