Figure 5 The relationship between stability of plot biomass and
logarithm (with base 10) of N-addition rate were given in two samples,
all sample plots and (b) loop samples with intransitive structure. The
solid circle represented coordinates of plot biomass average and\(\log_{10}N\), and the solid line represented the standard deviation.
With the increase of nitrogen enrichment, the biomass stability
decreased and the state of grassland ecosystem became worser and worser
comparing with natural state (in Fig. 5a,), because environmental
filtering reordered the species dominance. When N = 1 g
N·m-2·year-1, it was conducive to
enhance biomass stability, but N ≥ 2
g
N·m-2·year-1 is the opposite.
Fig. 5b given the biomass stability in intransitive competitive
structure changes with logarithm of N-addition rates. It was found that
the stability performed an increasing trend and then decreasing.
Intransitive structure completely offset the negative effect of medium
N-addition rates (5, 10 g
N·m-2·year-1) on the stabilities.
But excessive nitrogen enrichments (15, 20, and 50 g
N·m-2·year-1) completely covered the
ecological action of intransitive competition, resulting in the level of
the three stabilities similar to that of the all samples.