Vegetation Pattern Dynamics In Semi-arid Environment

In recent years,with the serious development of desertification,the protection of ground vegetation becomes increasingly important.The vegetation pattern can be seen in various types of landscapes,which can describe the spatial distribution of vegetation.Due to the variation of climatic and geographic conditions,the vegetation pattern structure becomes more diverse.The pattern dynamics in arid or semi-arid environments contribute to have a better understanding of vegetation pattern formation mechanism.To a certain extent,it can provide us some directions for vegetation protection.Along the above ideas,this paper study the vegetation pattern dynamics in semi-arid environments,the main contents are as follows:In chapter 1,the research background,research status and the main research contents of the activation-inhibition mechanism and the vegetation pattern are given.In chapter 2,we summarized four feedback regulation mechanisms existed between the vegetation and water,which can bring a brilliant light on the mechanism of vegetation pattern formation.In chapter 3,a classical pattern formation mechanism:activation-inhibition mechanism is discussed.Currently,the pattern formation principle of activation-inhibition mechanism has been applied in many fields.Thus,a Gierer-Meinhardt model with different exogenous resources is studied.Firstly,the condition of Turing bifurcation and the Turing region are obtained by employing the linear stability analysis;secondly,the basic pattern structures of Gierer-Meinhardt model are shown by using the relative theory of amplitude equations:spot patterns,stripe patterns and the mixed patterns of spot and stripe patterns.Lastly,numerical simulation testify the reasonability of the theoretical analysis.The results highlight the relation between the variation of biological tissues and the pattern formation,which provide the convenience for the dynamical analysis of vegetation pattern in semi-arid environments.In chapter 4,in order to reveal the effect of positive feedback mechanism on vegetation pattern formation,a water-biomass model in semi-arid environments with soil-water diffusion feedback is presented.Our results reveal that,as the soil-water diffusion intensity decreases,the pattern transitions:gap patterns ? stripe(labyrinth)patterns ? spot patterns emerge.More importantly,when the soil-water diffusion feedback intensity is smaller,the feedback will promote the growth of the vegetation;when the feedback intensity is much larger,the vegetation biomass will decrease and the feedback may induce the emergence of desertification.Additionally,the rainfall can also induce the pattern transition.As the rainfall capacity decreases,the vegetation disappears and becomes the bare soil state.Our findings highlight the relationship among feedback intensity,rainfall and pattern dynamics of the vegetation.In chapter 5,we summarize the main contents of this paper and give the outlook for further investigation.