Influences of biotic and abiotic factors on allometry and productivity-biomass relationship in Chinese forests

Background/Question/Methods

Tree productivity (P) and biomass (M) relationship and allometric scaling function between belowground biomass (M_A) and aboveground biomass (M_A) are two important relationships not only reflect plant adaptation to the environment, but also have significant implications in global carbon cycling, climate change, and forest management. However, how biotic factors (e.g. tree age, diameter at breast height [DBH], height) and abiotic factors (e.g. elevation, latitude, and longitude) influence these two relationships has not been well investigated. We analyzed a large database on tree productivity and biomass in China to derive their relationships and tested whether these biotic and abiotic factors correlate with changes in the modeling parameters. We first split the entire database into different groups by either tree age, DBH, height, latitude, longitude or elevation. For each group, we developed the allometric model between M_B and M_A and between P and M using major axis method. Linear regression model was also applied to P and M. To test whether the scaling exponent is independent of biotic and abiotic factors, we analyzed the relationship between the model parameters and these factors. 

Results/Conclusions

We found that M_B was significantly related to M_A following a scaling function with a scaling exponent of 0.964. The scaling exponent of M_B and M_A did not vary with tree age, density, latitude, longitude, or elevation, but varied with DBH, height, and elevation. The mean of scaling exponent over all groups was 0.986. Among 57 scaling relationships developed, 26 and 37 scaling exponents were not significantly different from 1.0 at α=0.05 and 0.01 levels, respectively. The scaling exponent of P and M varied with tree age, height, and density following a quadratic pattern, but decreased linearly with elevation. Our results generally support the isometric hypothesis that M_B scaled near isometrically with M_A. There was also a significant relationship between P and M in China, but the relationship varied with some biotic and abiotic factors.