Quantitative simulation of C budgets in a forest in Heilongjiang province, China.

Recently, forest carbon (C) budgets have been significantly affected by climate variability, nitrogen (N) deposition, an increasing global atmospheric CO2 concentration, and disturbances (i.e., harvests, fires, and insect infestations). In this study, we quantitatively simulated the annual carbon balance of forests in Heilongjiang, China, from 1901 to 2013 using the Integrated Terrestrial Ecosystem Carbon (InTEC) model, which integrated the effects of nondisturbance (i.e., atmospheric CO₂ concentration, N deposition, and climate variability) and disturbance factors. The average net primary production (NPP) of Heilongjiang was 284 g C m^-2 a^-1 in 1901 and increased in 1950 to 339 g C m^-2 a^-1; a rapid increase occurred after 1980, with an increase of 48% in 2013 compared with the NPP in 1901. The average NPP of the entire Heilongjiang region increased significantly and became more stable in 2013. However, the NPP in the northern region of the Xiaoxing'an Mountains was lower than that in the other regions. The fluctuation in average net ecosystem production (NEP) was relatively large because Heilongjiang was a carbon source for many years before the 1930s and again in the early 21^st century, due to serious disturbances and intensified human activities. In recent years, NEP began to increase again, and in 2013 the forests became a large carbon sink (188 g C m^-2 a^-1). The spatial distribution of the average NEP was similar to that of NPP, though the largest increment in the average NEP from 1901 to 2013 was in the Changbai Mountains. [ABSTRACT FROM AUTHOR]