干旱人工植被区藻结皮光合固碳的时间效应研究

摘要

研究了腾格里沙漠东南缘沙坡头地区不同建植年限(16、21、27、44和52a)人工植被区中发育藻结皮的净光合速率、年同碳量和累计固碳量变化特征,并分析了其与结皮生物学参数(盖度和生物量)和土壤表层0～3 cm有机碳含量的相关关系.结果表明:1)随着人工植被区建植年限的增加,藻结皮的最大净光合速率显著增加,从植被建植16a藻结皮的1.63 μmol m-2s-1增加至植被建植52a的2.81μmol m-2s-1;藻结皮的最大光合速率与结皮生物量和结皮盖度呈显著正相关关系;2)藻结皮的年固碳量随植被区建植年限的延长呈指数增加,随着人工植被区建植年限的增加,藻结皮的年固碳量显著增加,从建植16a藻结皮的C 0.2 g m-2a-1增加到52a的C 2.78 g m-2a-1;3)植被区建植后,藻结皮的固碳总量经历两个阶段的变化,建植16a到27a,藻结皮固碳总量在C 2.2～6.2 g m-2,建植44a后,固碳总量增加到C 23.9 g m-2;并且,藻结皮的固碳总量与土壤表层有机碳含量呈显著线性正相关关系.以上研究结果说明,随着人工植被固沙区的演替,藻结皮发育成熟度逐渐提高,其光合固碳能力显著提高,有利于干旱区土壤有机碳的累计.%Net photosynthetic rate, annual carbon fixation, and total carbon fixation of cyanobacterial crusts in relation to history of artificial revegetation (16, 21,27,44 and 52 years) were investigated at Shapotou, the southeast edge of the Tengger desert, and their relationships with biological parameters ( coverage and biomass) of the cyanobacterial crusts, and organic carbon content in the surface soil (0 ～ 3 cm) were also analyzed. Results show 1 ) the maximum net photosynthetic rate of the crusts profoundly increased with the history of revegetation, from 1.63 μmol m -2s -1 in the area revegetated for 16 years to 2.81 μmol m -2s-1 in the area revegetated for 52 years,showing significant positive relationship with coverage and biomass of the crusts; 2 ) annual carbon fixation increased exponentially with the history of revegetation, from 0. 2 g m -2a-lC in the area revegetated for 16 years to 2. 78 g m-2a-1 in the area revegetated for 52 years; and 3 ) the total carbon fixation of the crusts experienced two phases of variation after the revegetation; in the first phase (from 16a to 27a) low in total carbon fixation, in the range from 2.2 ～6.2 g m-2 C, and in the second phase (after 44a) high in total carbon fixation reaching 23.9 g m-2 C; showing a linear positive relationship with organic carbon content in the surface soil. The findings indicate that the maturity of cyanobacterial crusts improved along with the succession of the artificial revegetation, cyanobacterial crusts are getting more and more mature and increasing significantly in photosynthetic carbon fixation capacity, which is conducive to accumulation of soil organic carbon in arid soils.