基于BIOME-BGC模型的秦岭北坡太白红杉林碳源/汇动态和趋势研究

Carbon Source/Sink Dynamics and Trend of Larix chinensis in Northern Slope of Qinling Mountains Based on BIOME-BGC Model

为了解秦岭北坡太白红杉(Larix chinensis)的碳源/汇动态,运用BIOME-BGC模型模拟了1959-2016年太白红杉生产力、碳储量和碳利用效率(CUE),并利用气候情景设定方法预测碳源/汇功能的未来趋势。结果表明,58年间太白红杉的平均净初级生产力(NPP)、初级生产力(GPP)和净生态系统生产力(NEP)分别为328.59、501.56和31.42gCm^-2a^-1,平均碳储量为35.38kgCm^-2a^-1,平均CUE为0.65;除1960-1961、1969-1970、1997-1999年为“碳源”年外,绝大多数年份为“碳汇”年,年内呈现“碳源-碳汇-碳源”的变化特征,碳储量总体增加,潜在固碳能力较为稳定。GPP、NPP、碳储量的正向作用排序为气温上升>CO2浓度增加,NEP的正向作用排序反之,降水增加对生产力和碳储量增加起反作用,气温升高对CUE起反作用;气温和CO2浓度是北坡太白红杉生长的限制因子,气温的限制性强于CO2浓度,未来气温或CO2浓度升高有利于碳汇功能发挥,降水增加减弱碳汇效果。RCP4.5、RCP8.5情景下太白红杉生产力和碳储量在21世纪呈上升趋势,RCP8.5上升幅度略大于RCP4.5,潜在固碳能力仍较强;1-3月和10-12月为“碳源”月,5-9月为“碳汇”月。这揭示了气候变化背景下气温、降水和CO2浓度对太白红杉碳源/汇的影响方式,气温和CO2浓度上升是碳汇的促进因素,降水增加为阻碍因素。

Climate change and elevated CO2 concentration affect productivity and carbon balance of forest ecosystems. Timberline tree, Larix chinensis is extremely sensitive to climate change. In order to understand the carbon source/sink dynamics, the BIOME-BGC model was used to simulate the productivity, carbon storage and carbon use efficiency (CUE) of Larix chinensis in the northern slope of Qinling Mountains during 1959-2016, and the future trend of carbon source/sink function was projected by climate scenario setting method. The results showed that in the past 58 years, the average NPP, GPP and NEP were 328.59, 501.56 and 31.42 g C m^-2a^-1, respectively. The average carbon storage was 35.38 kg C m^-2a^-1, and the average CUE was 0.65. Except that 1960-1961, 1969-1970 and 1997-1999 were “carbon source” years, the rest were “carbon sink” years, showing the characteristics of “carbon source-carbon sink-carbon source” during the whole year. Overall, carbon storage increased and the potential carbon sequestration capacity was relatively stable. The positive effects of GPP, NPP and carbon storage were in the order of temperature increment > CO2 concentration enhancement, while the opposite effect of NEP had adverse order. Rainfall enhancement had counteraction on productivity and carbon storage, and temperature increment had a negative effect on CUE. Temperature and CO2 concentration were the limiting factors for the growth of L. chinensis in northern slope of Qinling Mountains, and the limitation of temperature was stronger than that of CO2 concentration. In the future, the increase of temperature or CO2 concentration will benefit the function of carbon sink, and the increase of precipitation will weaken the effect of carbon sink. In the RCP4.5 and RCP8.5 scenarios, the productivity and carbon storage of L. chinensis showed an upward trend in 21 century, and RCP8.5 increased slightly more than RCP4.5. The potential carbon sequestration capacity was still strong. January to March, October to December would be “carbon source” month, and May to September would be “carbon sink” month. These revealed the effects of temperature, precipitation and CO2 concentration on carbon source/sink of L. chinensis under the background of climate change. The increase of temperature and CO2 concentration were the promoting factor for carbon sink of L. chinensis, while the increase of precipitation was the limiting factor.