一年生荒漠植物对土壤氮素的生理响应

Physiological Response of Annual Desert Plants to Soil Nitrogen

土壤氮可利用性的季节性对植物生活史、生长和种间关系有重要影响,可确定氮素可利用性季节变化对卷果涩荠开花物候、个体生长、生物量分配及其与夏季一年生植物播娘蒿的种间关系的影响。试验模拟了均匀供氮、春季供氮和夏季供氮3种氮素可利用性的季节变化模式,并测定了3种模式下卷果涩荠开花物候、株高、生物量分配和叶片养分含量。通过比较盆栽植株在独生和与播娘蒿混生条件下的生长变化,分析不同供氮模式对种间关系的影响。结果表明：（1）供氮模式显著影响了卷果涩荠的开花物候,独生环境下,卷果涩荠的开花振幅在均匀和春季供氮处理下表现为单峰曲线,在夏季供氮处理下呈双峰形。培养方式对卷果涩荠的开花物候具有显著影响,混生下均匀供氮处理的卷果涩荠的开花峰值较独生提前4～5 d,峰值期的开花比例较独生植株高16%。（2）供氮模式和培养方式对卷果涩荠生长具有显著的交互效应。独生环境下,春季供氮处理下的卷果涩荠株高显著高于均匀供氮和秋季供氮处理,混生环境下,供氮处理对卷果涩荠的株高、地上、地下生物量、单株总生物量和根冠比无显著影响。（3）氮供应模式和培养方式对卷果涩荠叶片总氮（TN）和总磷（TP）含量及氮磷比无显著影响。当卷果涩荠与播娘蒿混生时,卷果涩荠对氮素的竞争力优于播娘蒿。结果说明,氮可利用性的季节性会对荒漠草本植物的物候进程、生长及未来的群落组成变化产生影响。

Seasonality of available soil nutrient has an important effect on plant life history,plant growth and interspecies relations. It can be confirmed that the seasonal variation of soil nitrogen affects the process of flowering phenology,plant growth and biomass allocation of Malcolmia scorpioides and its interspecies relations with Descuminia sophia. In this study,the seasonal variation of available soil nitrogen was tested and simulated under three nitrogen treatments,i. e. the uniform,spring and summer nitrogen application modes,and the values of flowering phenology,plant height,biomass allocation and leaf nutrient content of M. scorpioides under three nitrogen treatments were measured. The growth situations of M. scorpioides plants potted alone and planted in a mixed way with D. sophia were compared,and the effects of different nitrogen application modes on the interspecies relations were analyzed. The main results are as follows：（1） The process of flowering phenology of M. scorpioides was significantly affected by the nitrogen application modes,and the curves of flowering amplitude of M. scorpioides plants potted alone were unimodal under uniform and spring nitrogen application modes but bimodal under summer nitrogen application mode. Cultivation ways affected significantly the process of flowering phenology of M. scorpioides. The flowering peak of M. scorpioides plants planted in a mixed way was 4-5 days earlier under the uniform nitrogen allocation mode,and the flowering proportion at flowering peak was 16% higher that of plants potted alone;（2） There was no a significant interaction effect of nitrogen treatments and cultivation ways on the growth of M. scorpioides. The height of M. scorpioides plants potted alone was higher under spring nitrogen application mode than that under the uniform and autumn nitrogen application modes. Under the mixed environment,there was no significant effect of different nitrogen treatments on the plant height,aboveground biomass,underground biomass,total biomass of individual plants and rootshoot ratio of M. scorpioides;（3） There was no significant effect of nitrogen application mods and cultivation ways on the TN,TP and TN∶ TP ratio in leaves of M. scorpioides. The competitiveness of M. scorpioides was higher than that of D. sophia when these two plant species were planted in a mixed way. The study results revealed that the seasonality of available soil nitrogen affected the phenological process,growth and community composition of desert herbs.