Figure 1The structure of intransitive networks could be divided into five simple forms: short loop (a), nested loop (b), long loop(c), independent loop(d) and cross loop(e). The big brace means that the networks have nested loop always along with structure of long loop, independent loop or cross loop. Nodes in network represent species (letters), and red arrows point to less competitive species.
The structure of the intransitive network was divided into five simple forms: short loop (only one loop of three species, in Fig. 1a), nested loop (a large loop embedded with a small loop in Fig. 1b), long loop (all species fall into the loop, in Fig. 1c), independent loop (there are at least two loops, and no species shared in them, in Fig. 1d), and cross loop (at least two loops with shared and unshared species, in Fig. 1e). In the real plant community, the competitive relationship among species was very complex, and its competitive structure was often not a single structure. In the sample plots investigated, there were six kinds of loop-structure combinations of the five simples (in Tab.1), among which the short network, accounting for 23.04%, while the nested network, accounting for 76.96%, in 191 intransitive networks. The short network and the nested network are mutually exclusive, representing relatively simple network and more complex one, respectively.
Table 1 The kinds of combination of the simple loop structures are distributed. The short network, accounting for 23.04%, only contains short loop. The nested network, accounting for 76.96%, contains combination of other simple structures in addition to nested network, and there were five kinds of such combinations.