Abstract: In the vision of carbon neutrality, quantifying forest carbon sinks helps to make forest carbon strategies as well as carbon trading mechanisms, and enhance resistance to climate change, which plays a key role in safeguarding national ecological safety, achieving the goal of carbon neutrality, and slowing down global warming. Based on data collected from national forest inventory, we analyzed the trends of forest carbon stocks and carbon sinks in Heilongjiang Province from 1999 to 2018, using the continuous function of biomass conversion factors and the carbon tax method. Further, prediction for the carbon stocks of arbor forests was made using GM (1,1) model in order to obtain the predicted carbon sinks and their economic value in the year achieving the target of carbon peak. The results showed that forest carbon stocks of Heilongjiang increased from 696 billion kg in 1999-2003 to 914 billion kg in 2014-2018, with arbor forests accounting for 99.51%-99.65% of the total forest carbon stocks. Overall, the carbon sink of arbor forests in Heilongjiang Province presents an upward trend from 1999 to 2018, increasing from 16.8 billion kg·a^-1 in 2004-2008 to 17.6 billion kg·a^-1 in 2014-2018. The economic value of carbon sink shows a downward trend from 2.06 billion yuan·a^-1 in 2004-2008 to 1.66 billion yuan·a^-1 in 2014-2018 due to the variation of exchange rate. During the study period, the average carbon sink of mature forest is the largest among various age groups, and the broadleaved mixed forest is the major contributor to the forest carbon sink, accounting for 93.93% of the total carbon sink of arbor forest. With the enhancement of the afforestation, the proportion of carbon sink of the plantation forest will increase. The carbon sinks of arbor forests and their economic value in Heilongjiang by 2030 are predicted to be 18 billion kg·a^-1 and 1.89 billion yuan·a^-1, respectively.

Key words: Heilongjiang Province, carbon stock, carbon sink, carbon sink economic value