凋落物和增温联合作用对峨眉冷杉幼苗抗氧化特征的影响

峨眉冷杉林是青藏高原东缘亚高山暗针叶林的重要组成部分,其自然更新对全球变化非常敏感,是研究气候变化对陆地生态系统影响的代表性森林类型.以峨眉冷杉幼苗为研究对象,以开顶式增温小室(Open top chambers,OTCs)和电热棒联合的方式增加环境温度,人为添加不同类型凋落物(A,75％峨眉冷杉针叶+25％杜鹃荚蒾灌木叶凋落物;B,55％峨眉冷杉针叶+45％杜鹃荚蒾灌木叶凋落物),共设置4个处理:(1)凋落物A+增温T(A-T);(2)凋落物B+增温T(B-T);(3)凋落物A+环境温度TO(A-T0);(4)凋落物B+环境温度TO(B-TO).研究增温和两种类型凋落物联合作用下峨眉冷杉幼苗的生理生态响应特征.得到以下结果:(1)在环境温度下,A型凋落物情景下的冷杉幼苗的电导率、丙二醛和脯氨酸含量、超氧阴离子自由基产生率比B型情景下高;而可溶性糖和淀粉含量、超氧化物歧化酶(SOD)、抗坏血酸过氧化物氢酶(APX)和过氧化氢酶(CAT)活性比B型凋落物情景下低.说明在当前环境温度下,B型凋落物比A型凋落物更加适合冷杉幼苗的生长.(2)在A型凋落物情景下,增温处理显著增加了冷杉幼苗叶片的自由脯氨酸含量和过氧化氢浓度;在B型凋落物情景下,增温处理显著降低了冷杉幼苗丙二醛、自由脯氨酸含量、可溶性糖和淀粉含量,增加了超氧阴离子自由基产生速率.可见,与A型凋落物相比,增温使得B型凋落物情景下的冷杉幼苗膜伤害程度减小.(3)不同类型凋落物与增温的联合作用均降低了冷杉幼苗的可溶性糖和淀粉含量.与A-T处理相比,B-T处理下冷杉幼苗叶片的电导率、丙二醛和脯氨酸含量更低,而POD、APX、GR、CAT抗氧化酶活性却更高.研究结果表明,针叶成分相对较少的B型凋落物更有利于峨眉冷杉幼苗适应未来气候变暖情景.

Antioxidative responses of Abies fabri seedlings to litter addition and temperature elevation

Abies fabri (Mast.) Craib is an endemic and dominant species in typical subalpine dark coniferous forests, which mainly distributed in mountain regions of Western Sichuan, China. Due to the great sensitivity of the regeneration capacity to the climate change, it becomes the one of typical forest for studying effects of climate change on terrestrial ecosystem on eastern Tibetan Plateau. To asses how Abies Fabri seedlings may respond and adapt to future climate changes, we investigated the effects of temperature elevation and litter addition on the antioxidative responses of A. fabri seedlings. Temperature elevation was created by the combined use of open top chamber (OTCs) and electrical bar, and litter was artificially added in different types. Thus, four treatments were performed in this study: 1) litter A + temperature elevation T (A-T); 2) litter B + temperature elevation T (B-T); 3) litter A + the ambient temperature T0 (A-T0); 4) litter B + the ambient temperature T0 (B-T0). A stands for the mixed litter by seventy-five percentage of A. fabri woodly litter(Woodly, W)and twenty-five percentage of Azalea viburnum shrub litter (Shrub, S); and B, the mixed litter by fifty-five percentage of A. fabri woodly litter(Woodly, W)and forty-five percentage of Azalea viburnum shrub litter (Shrub, S). The results showed that: 1) under the ambient temperature, the electrical conductivity, the malondialdehyde (MDA) and proline content, and the rate of superoxide anion radical (O₂^-) of A. fabri seedlings is higher under litter A than litter B; the soluble sugar and starch contents, the superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) activity of A. fabri seedlings is lower under litter A than litter B. These results suggested that litter B will be helpful to the growth of A. fabri seedlings; 2) temperature elevation markedly increased the proline content and hydrogen peroxide (H₂O₂) of A. fabri under litter A. However, under litter B temperature elevation significantly decreased the content of malondialdehyde (MDA), free proline, soluble sugar and starch contents, and increased rate of superoxide anion radical (O₂^-). Obviously, the oxidative damage of A. fabri seedlings suffering from temperature elevation is lower under litter B than under litter A; 3) the interaction of litter and temperature elevation reduced the soluble sugar and starch contents of A. fabri seedlings. The electrical conductivity, the malondialdehyde and proline content of A. fabri seedlings in B-T treatment is lower than the A-T treatment; the peroxidase (POD), ascorbate peroxidase (APX), glutathione (GR) and catalase (CAT) activity of A. fabri seedlings is higher in B-T treatment than in A-T treatments. These present results suggested that litter B with lower needles proportion will be helpful to A. fabri seedlings to future climate warming.