温度增高、CO2浓度升高、施氮对蒙古栎幼苗非结构碳水化合物积累及其分配的综合影响

蒙古栎(Quercus mongolica)是中国东北地区天然次生林重要组成树种, 研究该树种幼苗有机碳积累及碳库容对未来气候变化的响应, 可为预测未来气候变暖情景下蒙古栎林的天然更新及幼苗的培育提供科学参考。该文旨在探讨CO₂浓度和温度升高综合作用对蒙古栎幼苗非结构性碳水化合物(NSC)积累及其分配的影响。实验环境条件用人工气候箱控制, 控制条件如下: 1) CO₂浓度倍增(700 μmol·mol^-1), 温度升高4 ℃处理(HCHT); 2) CO₂浓度正常(400 μmol·mol^-1), 温度升高4 ℃处理(HT); 3) CO₂浓度和温度均正常, 即对照组(CK); 每个气候箱幼苗分别在3种氮素水平下生长: N2 (15 mmol·L^-1, 高氮), N1 (7.5 mmol·L^-1, 正常供氮)和N0 (不施氮), 一共为9个处理。研究结果表明, 1) HCHT共同作用对NSC积累无促进作用, 但改变了植物各器官中NSC的分配比例, 叶片中可溶性糖和淀粉的积累明显增加, HCHT下N2水平有利于NSC的积累。2) HT明显影响了蒙古栎一年生幼苗NCS的积累和分配。在N2水平下, HT明显促进NSC的积累, 并增加了在主根中的分配比例。3)植株各器官可溶性糖含量的动态变化因处理不同而异。主根淀粉含量随时间逐渐增加, 而细根淀粉含量随时间逐渐减少。在未来气候变暖的情况下, 土壤中大量的氮供给, 可能将促进蒙古栎幼苗的生长、增加其碳库容和抵御不良环境的能力, 进而提高其天然更新潜力。

Combined effects of elevated temperature,elevated [CO2] and nitrogen supply on non-structural carbohydrate accumulation and allocation in Quercus mongolica seedlings

Aims Quercus mongolica is the main secondary forest species in northeastern China. Study of the responses of its organic carbon accumulation and storage capacity to climate changes may provide a scientific basis for predicting community regeneration and growth. Our aim was to determine responses of non-structural carbohydrate (NSC) of Q. mongolica seedlings to the combined effects of elevated CO₂ concentration, temperature and soil nitrogen. Methods We used three artificial climate chambers whose environmental conditions were 1) CO₂ concentration elevated to 700 μmol·mol^–1 and temperature elevated 4 °C (HCHT), 2) temperature elevated 4 °C and CO₂ concentration unaltered (HT) and 3) temperature and CO₂ concentration unaltered. Three different soil nitrogen concentrations were used to determine effects on the dynamics of NSC in one-year old seedlings during the growing season: N2 (15 mmol·L^–1), N1 (7.5 mmol·L^–1, i.e., the normal nitrogen supply) and N0 (no nitrogen). Important findings The HTHC treatment changed the proportion of NSC partitioned to different organs of the seedlings and increased the accumulation of sugar and starch by the seedlings. N2 supply increased the accumulation of NSC, but there was no promotion effect on the accumulation of total NSC of the seedlings. The HT treatment significantly affected the accumulation and allocation of NSC of the seedlings, promoted the accumulation of NSC of the seedlings and increased the proportion of allocation of NSC to taproots under N2 supply. The dynamics of the soluble sugar content were different among the three treatments in different organs of the seedlings. The starch content increased in taproots, but gradually decreased in fine roots. Added nitrogen may promote the growth of Q. mongolica seedlings with future climate warming, thereby increasing their carbon storage, ability to withstand adverse environmental conditions and potential natural regeneration.