Carbon Stocks and Dynamics in the Three-North Protection Forest Program, China

The Three-North Protection Forest Program is a typical cross-regional agro-forestry system in China meant to enhance the operation and management quality of the nation's forests with a particular goal of creating and enhancing large carbon sinks. Based on statistical data from phase I (1978-1985), phase II (1986-1995), phase III (1996-2000), and phase IV (2001-2010) of the Three-North Protection Forest Program and in combination with the region-scale volume-derived biomass model, we estimated the carbon density, and carbon stocks, and biomass at the beginning and the end of the period of four projects within the Three-North Protection Forest Program, analyzed dynamic changes in the carbon stocks and carbon density of forests of different types and stand ages. The results showed that in 1977, 1985, 1995, 2000 and 2010, the carbon stocks to be 176.22 Tg, 189.48 Tg, 238.82 Tg, 243.88 Tg, and 744.19 Tg (1 Tg = 10(12) g) at the beginning of the project and at the end of each of its first four phases, respectively, and the carbon densities to be 15.06 t.hm(-2), 13.76 t.hm(-2), 12.70 t.hm(-2), 16.42 t.hm(-2), and 22.94 t.hm(-2). The quality of the forests in the Three-North Protection Forest Program increased gradually. Timber forests and the shelter forests were dominant. Over time, the proportion of the carbon stocks in shelter forests gradually became higher than that of timber forests. The carbon stocks of the half-mature forests were the greatest, followed by the mature forests. The young forests occupied the largest geographic area. As these young forests mature, the Three-North Protection Forest Program may become a huge carbon stocks.