基于立木胸径生长率模型的乔木林碳汇潜力评估

Assessment of Carbon Sink Potential of Arbor Forests Based on DBH Growth Rate Model for Standing Trees

树木生长产生巨大碳汇,对于缓解碳排放带来的全球变暖等环境问题具有重要意义。为准确评估森林碳汇,基于第6至第9次国家森林资源连续清查数据建立北京市13个主要树种(组)4种形式的立木胸径年生长率模型,预测树木胸径变化的未来趋势,从而为生物量转换因子连续函数法计算碳储量提供计算依据,最终获得2050年北京市乔木林碳储量和碳密度。结果表明:8个树种(组)胸径的年生长率模型R2都大于0.900,椴树的R^(2)最高为0.960;除柳树、水胡黄(水曲柳、胡桃楸、黄菠萝)外的11个树种(组)RMSE都小于0.5 cm;除杨树、其他硬阔类和榆树之外,Bias都小于1.0 cm。胸径预测精度验证中整体R^(2)较高,刺槐最高(0.951),其他硬阔类最低(0.766)。预测2050年北京市乔木林碳储量为42.71 Tg C,碳密度为43.35 Mg C·hm^(-2)。基于胸径年生长率模型的树木生长模拟方法可以有效的提高未来北京市乔木林碳汇潜力评估的整体精度,能够为制定温室气体减排政策、实现2060碳中和目标提供基础。

The growth of trees generates a huge carbon sink,which is of great significance in alleviating environmental problems such as global warming caused by carbon emissions.To accurately assess the carbon sink of forests,a model of the annual growth rate of tree diameter at breast height(DBH)in 4 forms for 13 main tree species(groups)in Beijing was established based on the data from the 6th to 9th National Forest Inventory.This model predicted the future trend of DBH changes,thereby provided a computational basis for calculating carbon storage using the continuous function method of biomass conversion factors.Ultimately,it estimated the carbon storage and carbon density of deciduous forests in Beijing by 2050.The results showed that:8 of the tree species(groups)had a DBH annual growth rate model R2 greater than 0.900,with the highest R^(2) of 0.960 for linden;except willow and Fraxinus mandshurica/Juglans mandshurica/Phellodendron amurense the RMSE of 11 tree species(groups)was less than 0.5 cm;except for poplars,other hard broad-leaved forests and elms,Bias was less than 1.0 cm.The overall R^(2)in the validation of DBH prediction accuracy was high,with the highest for black locusts(0.951)and the lowest for other hard broad-leaved forests(0.766).It was predicted the carbon stock of arbor forests in Beijing in 2050 was 42.71 TgC,and the carbon density is 43.35 MgC·hm^(-2).The study found that the tree growth simulation method based on the annual growth rate at breast height model could effectively improve the overall accuracy of future carbon sink potential assessment of tree forests in Beijing,which could provide a theoretical basis for formulating greenhouse gas reduction policies and achieving the 2060 carbon neutrality target.