3.2 Density effects on above- and belowground biomass allocation
The density effects on the above- and belowground biomass allocations varied among the different species. There were statistically insignificant changes in the total biomass of S. grandis and the root biomass of S. viridis per individual with increasing density (Figure 4c, k), while the average total, shoot and root biomass of the other four species per individual showed decreasing trends with increasing density (Figure 4a, e, g, i). Density had a very limited effect on the biomass fraction of the annuals (C. glaucum ,S. viridis ) and S. grandis , and the SMF, RMF and R/S remained almost unchanged under the different density conditions (Figure 4b, d, l). In contrast, for the other perennials, density had significant effects on the biomass fractions, but these effects showed different patterns. For C. squarrosa , the SMF decreased while the RMF and R/S increased with increasing density (Figure 4f). For L. chinensis and M. sativa , density had complicated effects on the SMF, RMF and R/S; each of these indicators tended to fluctuate with increasing density (Figure 4h, j).