缙云山针阔混交林碳通量变化特征及影响因子研究

Characteristics of Carbon Fluxes and Their Response to Environmental Factors in Ecosystems of Mixed Coniferous and Broad-leaved Forests in Jinyun Mountain

基于涡度相关技术,以2016年6月～2017年5月的通量数据为依据,分析了缙云山针阔混交林生态系统碳通量变化特征及其对环境因子的响应。结果表明:各月CO_2通量平均日变化呈"U"字形,最小值出现在7月,为-0.95 mg·m^(-2)·s^(-1),最大值在12月,为0.43 mg·m^(-2)·s^(-1),CO_2通量正负值转换时刻具有明显的季节变化规律,夏季日碳汇时间最长,冬季日碳汇时间最短;净生态系统碳交换量累积量除12月为正值(20.38 gC·m^(-2)·mon^(-1)),表现为碳源外,其他月份均为负值,表现为碳汇,碳积累量最多的是7月(-129.53 gC·m^(-2)·mon^(-1)),净生态系统碳交换、生态系统呼吸、总生态系统碳交换年总量分别为-566.49、1 196.68、-1 761.63 gC·m^(-2)·a^(-1);光合有效辐射是影响日间净碳交换量的主导因子,二者关系符合Michaelis-Menten模型,日间净碳交换量随光合有效辐射增大而降低,光合有效辐射PAR能解释14.1%～58.2%的日间净碳交换量变化,饱和水汽压差是日间净碳交换量限制因子,最适范围是0.5～1.0 kPa,过高和过低均会使日间净碳交换量对光合有效辐射的响应减弱;影响夜间净碳交换量的主导因子是5 cm土温,二者关系符合Van’t Hoff模型,夜间净碳交换量随5 cm土温增大而增加,土壤体积含水率是夜间净碳交换量的限制因子,饱和水汽压差大于或小于0.28 m^(-3)·m^(-3)均会对夜间净碳交换量产生抑制作用,但作用较小。缙云山针阔混交林净生态系统碳交换能力与相近纬度其他森林生态系统基本持平,总生态系统碳交换能力和生态系统呼吸强度则较大。

On the basis of eddy covariance technique and flux data from June, 2016 to May, 2017, the characteristics of carbon flux in the mixed broadleaf-conifer forest ecosystem in Jinyun Mountain and its response to environmental factors are analyzed. The results show that the mean inteRdiuRnal variation of monthly CO2 flux presented a 'U' shape during the study, and the minimum value is-0.95 mg·m-2·s-1 in July and the maximum value is 0.43 mg·m-2·s-1 in December. Moreover, there is obvious seasonal variation in the transition time of CO2 flux positive and negative values, among them, the time of daily carbon sink is the longest in summer and the shortest in winter;the NEE cumulant is negative and presented as carbon sink in 12 months of one year except December, in which is positive(20.38 gC·m-2·mon-1) and presented as carbon source, the largest carbon accumulation is in July(-129.53 gC·m-2·mon-1), NEE, ER and total GEE are-566.49, 1 196.68 and-1 761.63 gC·m-2·a-1·a-1 respectively.Furthermore, PAR is the dominant factor affecting the NEEd, the relationship between them is consistent with the Michaelis-Menten model, NEEd decreases with the increase of PAR, and PAR can explain the change NEEd of 14.1%-58.2%;VPD is the limiting factor of NEEd, whose optimal range is 0.5-1 kPa, because too high or too low will reduce the response of NEEd to PAR;5 cm Ts is the dominant factor affecting NEEn,the relationship between them is consistent with the Van’t Hoff model, and NEEn increases with the increase of 5 cm Ts;SWC is the limiting factor of NEEn, when SWC is greater or less than 0.28 m-3·m-3, it will inhibit the NEEn with little effect. To sum up, the NEE capacity of mixed broadleaf-conifer forest in Jinyun Mountain is basically equal to that of other forest ecosystems at similar latitudes, while the total ecosystem exchange capacity and ecosystem respiratory intensity are larger.