骆驼刺幼苗生长和功能性状对不同水氮添加的响应

采用盆栽实验,设计干旱(30%~35%FC)、中水(60%~65%FC)和湿润(80%~85%FC)3个水分梯度以及不施氮、低、中、高4个氮素水平的完全随机组合试验,连续2年研究了不同水分和氮素添加对骆驼刺幼苗生物量、叶片和细根功能性状的影响,并分析了不同功能性状间的相关性。结果表明,骆驼刺幼苗的生物累积、叶片和细根功能性状均受到水氮交互作用的显著影响,但不同生长时期响应格局不同。对于1年生幼苗,总根系生物量在干旱低氮处理下最高,但与中水不施氮处理差异不明显;比叶面积和叶氮含量在干旱中氮处理下均显著高于其他处理,叶片组织密度值却最低;在干旱高氮处理下细根比根长显著高于其他处理,细根组织密度却明显较低。对于2年生幼苗,中水中氮处理的叶片、细根、地上和地下生物量累积均最高;比叶面积在对照处理(干旱不施氮)下最高,叶片组织密度值却最低;干旱低氮处理的细根比根长显著高于其他处理,但细根组织密度明显较低。叶片与细根功能性状间无明显相关性,但叶片与总根系生物量呈极显著正相关。叶氮含量与比叶面积也呈显著正相关,细根比根长与细根组织密度、比叶面积与叶片组织密度均呈显著负相关。这表明叶片与细根功能性状对水氮条件变化的响应并不同步,地上与地下生长的关联主要表现为叶片和根系生物量累积变化的一致性。

Growth and functional trait responses of Alhagi sparsifolia seedlings to water and nitrogen addition

A 2-year pot experiment was conducted to study the effects of water and nitrogen additions on the growth and leaf and fine root traits of Alhagi sparsifolia seedlings, and to investigate the functional trait relationships between leaves and fine roots. The experiment was a completely randomized design with three water levels drought, 30%-35% field capacity (FC); middle water level, (60%-65% FC); high water level, (80%-85% FC)] and four nitrogen (N) levels (no, low, middle, and high N level). The results showed that the biomass and the leaf and fine root traits of A. sparsifolia were significantly affected by the interaction between water and N treatments. However, the responses of different functional traits to water and N differed depending on the plant growth stage. For 1-year-old A. sparsifolia, there was no significant difference in the total root biomass between the drought and low-N treatment (51 mg N/kg) and the middle water treatment, but the total root biomass was higher in both of those treatments than in the other treatments. The maximum values of leaf N concentration (LNC) and specific leaf area (SLA) and the minimum value of leaf tissue density (LTD) were in the drought and middle-N treatment (102 mg N/kg). The maximum specific fine root length (SRL) value and very low fine root tissue density (RTD) values were in the drought and high-N treatment (306 mg N/kg). For 2-year-old A. sparsifolia, the maximum values of leaf, fine root, shoot, and belowground biomass were in the middle water and N-supply treatment. The maximum SLA and minimum LTD were in the control (drought and no N), whereas maximum SRL and very low RTD values were in the drought and low-N treatment. Leaf biomass was significantly and positively correlated with total root biomass at two growth stages, but there was no correlation between leaf and fine root traits. For the same organ, SLA was positively related to LNC, but negatively correlated with LTD. There was a negative correlation between SRL and RTD. The responses of leaf and root traits to different water and N supplies were not synchronized. The linkages between above- and below-ground growth were mainly reflected by the consistent variations in leaf and root biomass.