Abstract: To explore the above and below ground biomass allocation patterns of herb layer, two different forest type including the natural evergreen broad-leaved forest and Chinese fir plantation with various age classes in Fujian Province were analyzed using the logarithmic equation: lg y=b+a lg x, and the isometric above and below ground biomass allocation theory was also detected using the above and below ground biomass of herb layer. The results indicated that the herbaceous layer biomass of natural evergreen broad-leaved forest decreased with the increasing of stand age. On the contrary, in Chinese fir plantations, the total biomass of herb layer was the highest in the mature forest stage, and the total biomass was the minimum in the pre-mature forest. Additionally, the ratios of above to below ground biomass were different for the two forest types. In different forest age, the scaling exponents(a)of above and below ground biomass in natural evergreen broad-leaved forest herb layer were 0.785, 0.757, 0.760 and 1.232, respectively. The above ground biomass scaled isometrically with below ground biomass of young and mature forest herb layers in natural evergreen broad-leaved forest, with the 95% confidence interval including the theoretical value of 1.0. Furthermore, the 95% confidence interval of the scaling exponents were close with 1.0 in the middle age and pre-mature forests. For the scaling constants(b), it followed the order of mature forest <young forest < middle-age forest < pre-mature forest. The scaling exponents(a)of herb layer ground in Chinese fir forests were all consistent with the isometric biomass allocation theory. For the scaling constants(b), it followed the order of young forest >mature forest > pre-mature forest > middle-age forest. The result support the theory that above ground biomass of herb layer scales i ometrically with below ground biomass.