Modelling The Effects Of Different Modes Of Positive Interactions On Plant Population Dynamics

Positive interactions(facilitation)are closely related to many ecological theories,and have attracted more and more attention in plant ecology during the past two decades.However,the effects of different modes of facilitation(symmetric or asymmetric)on plant population dynamics are not well addressed.This study focused on the effects of different modes of facilitation on plant population dynamics,in specific,the density-dependent mortality process(self-thinning)and spatial pattern dynamics.Self-thinning is an important driving factor for plant population dynamics.Previous studies have shown that facilitation could affect the self-thinning line,but the effects of different modes of facilitation on self-thinning has not been studied,and the relative influence and importance of various factors on plant population self-thinning were not systematically measured.In addition,many studies have shown that positive interactions is important driving factor for spatial pattern formation,but there is no distinction between different modes of facilitation.In this study,spatial-explicit individual-based model and random forests model were used to assess the relative influence and importance of facilitation mode and other factors on population self-thinning and the stability of spatial pattern.Our results suggested that different modes of facilitation had different effects on plant population self-thinning and the stability of spatial pattern.For self-thinning process,asymmetry facilitation resulted lower and shallower self-thinning lines than symmetry facilitation.Among other factors,mode of competition was the most important factor that alters both slope and intercept of the self-thinning line,other factors were much less important than competition on the variation of slope,but were more important in altering the intercept of self-thinning line.For the stability of spatial pattern,facilitation mode was the most important factor.The stability of spatial pattern with symmetric facilitation increased with increasing stress,asymmetric facilitation can reduce the stability under high stress conditions,and completely asymmetric facilitation can cause system collapse under high stress.This study further improved the relevant theories of positive interactions in plant population dynamics,providing a useful theoretical basis for vegetation conservation and restoration in high stress areas.The study also demonstrates that the joint application of individual-based models and machine learning approaches have capabilities and advantages in studying complex patterns,provides new insights into ecology,and has broad prospects in developing ecological theories and for supporting environmental applications.