Modifying regeneration strategies classification to enhance the understanding of dominant species growth in fire-prone forest in Southwest China

Abstract

In fire-prone ecosystems, plant species having different post-fire regeneration strategies (PFRS) coexist at the local scale while showing different growth dynamics. To evaluate the effect of PFRS on species regeneration, we investigated the plant communities burned in different years in the central Yunnan Province, Southwest China. Several indicators describing plant growth and population importance were measured to compare the regeneration of four dominant tree species, including one facultative seeders (FS) and three obligate resprouters (OR). Partial correlation and mixed linear effect modeling were applied to disentangle the contribution of intrinsic and environmental factors to the interspecific variation in post-fire regeneration. We identified two subtypes of plant growth strategy in the early post-fire stage for OR species; i.e., number growth (OR ​+ ​N) priority and height growth (OR ​+ ​H) priority for sprouting stems. Generally, the FS and OR species varied in height growth rate with different temporal dynamics. The OR ​+ ​N species occupied post-fire space horizontally with more resprouts and larger coverage than OR ​+ ​H and FS species at the earlier stage. In contrast, the OR ​+ ​H species generally had far less resprouts per clump, more variations in stem height and basal diameter. Factor analysis showed that the variation of post-fire plant regeneration was not effectively explained by environmental factors (R2 ​< ​20%); however, the linear mixed models with the modified PFRS as a random effect substantially increased the explanation. The differentiated regeneration dynamics and growth priorities in the four dominant tree species indicated a critical dichotomy of habitat occupation strategy for the resprouter species during the early stage of post-fire forest restoration. Our study uncovered a trade-off between height versus number growth priority in the post-fire tree growth strategy and provides a novel perspective in understanding the living space occupying (niche partitioning) process and species coexistence in post-fire forest community assembly.