云南松幼苗生长及化学计量对遮阴和干旱互作的响应

Growth and stoichiometry of Pinus yunnanensis seedlings in response to shade and drought interaction

关键词:  云南松, 化学计量特征, 干旱胁迫, 遮阴胁迫, 变异性, 相关性

Key words:  Pinus yunnanensis, stoichiometric characteristics, drought stress, shade stress, variability, correlation

摘要:

为探究云南松(Pinus yunnanensis)幼苗生长及不同器官的碳(C)、氮(N)、磷(P)化学计量特征对遮阴和干旱处理的响应规律和适应机制,以1年生云南松幼苗为对象,采用盆栽控制试验,测定分析遮阴和干旱环境下云南松幼苗的生长状况。该试验设置0%遮阴和70%遮阴2个水平,设置正常水分(CK,80%±5%)、轻度干旱(LD,65%±5%)、中度干旱(MD,50%±5%)和重度干旱(SD,35%±5%)4个水分梯度,测定遮阴和干旱处理下云南松幼苗的生长指标及叶、茎、粗根和细根的C、N、P含量,并计算其化学计量特征。结果表明:(1)在0%遮阴条件和 70%遮阴条件下,轻度干旱的苗高、地径和生物量增量均最大; 与不遮阴处理相比,遮阴处理下叶生物量增量在各干旱胁迫处理下显著增加。(2)与正常水分处理相比,随干旱胁迫程度增加,遮阴和干旱互作下,云南松幼苗各器官中的C含量变化不显著; 叶N含量减少,茎和粗根中的N含量增加,细根N含量则先减少后增加; 叶和粗根中的P含量减少,细根P含量增加。(3)各元素的变异性大小顺序为C<N<P; C元素在茎中变异性最小且在茎、粗根和细根中均存在弱变异; N元素在叶中变异性最小; P元素在细根中变异性最大。(4)云南松幼苗各器官中的C、N、P含量之间存在普遍相关性,C含量在粗根与细根之间呈负相关,N含量在叶与细根、茎与粗根及粗根与细根之间呈正相关,P含量在叶与细根之间呈正相关。综上认为,云南松幼苗在干旱环境下生长主要受N元素的限制,遮阴减缓了云南松幼苗生长受N元素的限制,云南松幼苗通过提高对N、P的利用效率来改善幼苗的生境,并缓解干旱胁迫对其造成的伤害。建议今后在林下培育云南松苗木时,可进行适当的遮阴。

Abstract:

In order to investigate the growth of Pinus yunnanensis seedlings and the stoichiometric characteristics of carbon(C), nitrogen(N)and phosphorus(P)of different organs in response to shade and drought treatments and the adaptive mechanism, the growth of P. yunnanensis seedlings in shade and drought environments was measured and analyzed in a potting controlled experiment using 1-year-old P. yunnanensis seedlings as the target. The experiment was set up with two levels of 0% shade and 70% shade, and four moisture gradients of normal moisture(CK, 80%±5%), light drought(LD, 65%±5%), moderate drought(MD, 50%±5%)and severe drought(SD, 35%±5%)were set to determine the growth indexes of P. yunnanensis seedlings under shade and drought treatments, as well as the C, N, and P contents of leaf, stem, coarse root and fine root, and calculate the stoichiometric characteristics of their stoichiometric characteristics. The results were as follows:(1)Seedling height, diameter and biomass increment were the greatest under 0% shade and 70% shade conditions with LD; leaf biomass increment was significantly increased under the shade treatment(70% shade)compared with no shade treatment(0% shade)in all drought stress treatments.(2)Compared with the normal water treatment, with the increase of drought stress degree, the C content in each organ of P. yunnanensis seedlings under the shade and drought interaction did not change significantly; the N content in leaf was decreasing, the N contents in stem and coarse root were increasing, and the N content in fine root was decreasing and then increasing; the P content in leaf and coarse root was decreasing, and the P content in fine root was increasing.(3)The order of variability of each element was C<N<P; C element has the smallest variability in stem and weak variability in stem, coarse root and fine root; N element has the smallest variability in leaf; P element has the largest variability in fine root.(4)There was a general correlation among the C, N and P contents in each organ of P. yunnanensis seedlings. C content was negatively correlated between coarse root and fine root, N content were positively correlated between leaf and fine root, stem and coarse root, and coarse root and fine root, and P content was positively correlated between leaf and fine root. In summary, the growth of P. yunnanensis seedlings in drought environment is mainly limited by N element; shade slows down the growth of P. yunnanensis seedlings limited by N element. P. yunnanensis seedlings improve the habitat of seedlings by increasing the utilization efficiency of N and P, and can alleviate the damage caused by drought stress. It is recommended that appropriate shade be provided when cultivating P. yunnanensis seedlings in the forest understory in the future.