Does the net primary production converge across six temperate forest types under the same climate?

Quantifying net primary production (NPP) and its allocation is essential for understanding and modeling the carbon (C) cycling in forest ecosystems. We used biometry-based measurements to examine the NPP allocation for six temperate forest types with similar stand age and climate but diverse stand characteristics and site conditions in northeastern China. The forest types included four naturally-regenerated stands and two planted stands. Our objectives were to (1) compare the NPP and its allocation among the six forest types, and (2) explore the factors driving the inter-stand variability of the NPP allocation patterns. We found that the total NPP (TNPP) and NPP of short-lived biomass tissues (NPPSL) differed significantly among the forest types, varying from 709 to 927 gC m−2 yr−1 and from 364 to 594 gC m−2 yr−1, respectively. However, the NPP of long-lived tissues (NPPLL) did not differ significantly among the forest types, varying from 305 to 364 gC m−2 yr−1. These results suggested that the production of structural tissues be relatively stable under the same climate, and the inter-stand difference in TNPP be mainly attributed to the difference in NPPSL. Within the four natural stands, the foliage production was significantly and positively correlated with soil nitrogen (N) (R2 = 0.50) and phosphorus (P) stock (R2 = 0.37), whereas the fine root production was significantly and negatively correlated with soil C:P (R2 = 0.54) and N:P ratio (R2 = 0.47), implying that foliage and root production may be driven by different mechanisms. The convergence of NPPLL across forest types with different stand characteristics, site conditions and management practices but under the same climate has important implication in managing forest ecosystems for C sequestration, while the divergence of NPPSL implies that vegetation can adapt to the site conditions by changing resource-absorbing tissues production and its allocation.