基于Biome-BGC模型的西双版纳橡胶林碳收支模拟

Simulation of carbon budget in rubber plantations in Xishuangbanna based on the Biome-BGC model

以西双版纳橡胶适宜种植区(海拔550—600m)的橡胶林(Hevea brasiliensis)为研究对象,应用参数同化后的Biome-BGC模型模拟了1959—2012年橡胶林的碳循环。结果表明,(1)与涡度相关监测结果相比,橡胶林年总初级生产力(Gross Primary Productivity,GPP)、年总呼吸(Total Respiration,Rt)的模拟精度分别为98.37%和90%。由于对年GPP的过低估计和对年Rt的过高估计,年净生态系统交换量(Net Ecosystem Exchange,NEE)的模拟值比实测值低157.35 g C m^(-2)a^(-1)。但若考虑干胶碳(139g C m^(-2)a^(-1)),模拟值与实测值十分接近;(2)橡胶林在模拟进行的前8年里因异养呼吸较高,以碳排放为主,NEE平均约357 g C m^(-2)a^(-1);之后转为以碳固定为主,NEE平均约^(-1)46 g C m^(-2)a^(-1);(3)橡胶林在40年的更新周期中可固定碳1835 g C m^(-2),是一个弱的碳汇。但与热带雨林相同周期固碳6720 g C m^(-2)相比,仍为碳源。以上结果为深入了解橡胶种植对区域碳循环的影响提供了科学依据,建议当地政府一方面要有计划的对老胶林进行更新,以维持当前橡胶林生态系统中的碳平衡;另一方面要注重对热带雨林的保护,从而实现区域经济和生态环境保护的协调发展。

The carbon （C） cycle in rubber plantations, which are located in a suitable planting region （altitude 550-600 m） in Xishuangbanna, was simulated using the Biome-BGC model for the period 1959-2012. We obtained the following results. （1） Compared with the actual measurements, the accuracy was 98.37% and 90% for the simulated annual gross primary productivity （GPP） and total respiration （Rt）, respectively. Because of an underestimate of GPP and an overestimate of Rt, the simulated annual net ecosystem exchange （NEE） was 157.35 g C m-2 a-1 lower than the measured value. However, the accuracy was greatly enhanced when dry rubber C stock （139 g C m-2 a-1） was taken into account. （2） During the initial 8 years, rubber plantation acted as a C source because of the higher heterotrophic respiration rate, with an average simulated NEE of 357 g C m-2 a-1. Subsequently, however, the balance changed to C sequestration, with an average simulated NEE of -146 g C m-2 a-1. （3） Rubber plantation sequestrated 1 835 g C m-2 during a 40-year rotation length, which is lower than that in tropical rain forests, which fixed 6 720 g C m-2 a-1 during the same period, indicating that rubber plantations established in areas of former tropical rain forest might lead to C release, even during a complete life cycle. These results enabled us to gain a better understanding of the impact of rubber plantation on the local carbon cycle. In order to reach a sustainable balance between the regional economy and environmental protection, it is suggested that the local government should not only regenerate older rubber plantations in a planned way to maintain C balance in the rubber plantation ecosystem, but also pay considerable attention to the protection of tropical rain forests.