Carbon storage, net primary production, and net ecosystem production in four major temperate forest types in northeastern China

Temperate forests in northeastern China play a key role in the national carbon (C) budget; however, this role has been poorly quantified. The objective of this study was to quantify C storage, net primary production (NPP), and net ecosystem production (NEP) in four major temperate forest types in northeastern China. The four forest types include a primary mixed broadleaf - Korean pine (Pinus koraiensis Siebold & Zucc.) old-growth forest and three mid-aged regenerating forests, i.e., a secondary birch (Betula platyphylla Sukaczev) forest, a Korean pine plantation, and a Dahurian larch (Larix gmelinii (Rupr.) Rupr.) plantation. Total C storage differed significantly among the four forest types, with the highest storage (315.4 t C.ha(-1)) in the old-growth forest. Soil organic C accounted for 55%-70% of the ecosystem C, whereas vegetation C accounted for 28%-43% of the ecosystem C. Soil organic C storage in the two plantations was significantly lower than that in old-growth and secondary birch forests. The allocation (aboveground and belowground) of NPP, but not the total NPP, differed significantly among the forest types. Litterfall (44%-60%) and fine root production (43%-47%) contributed the largest proportion of the aboveground and belowground NPP, respectively. The highest NEP was in the Korean pine plantation (328.0 g C.m(-2).year(-1)), followed by the old-growth (311.9 g C.m(-2).year(-1)) and secondary birch (231.1 g C.m(-2).year(-1)) forests, with the lowest NEP in the Dahurian larch plantation (187.9 g C.m(-2).year(-1)). These results suggest that the major forest types are currently C sinks and Korean pine plantation establishment can be a promising approach for increasing C sequestration in northeastern China.