Why wouldn’t all of the new varieties of the pioneer plant survive in each new Niche

Explanation:

Pioneer species are the first species to colonize a particular barren land that has been existing before but distrupted by activity such as fire. Example are lichens and lime grass.

When pioneer species are introduced into a new niche it takes time for them to get adapted to their new environment. During those period of them trying to fit into the new niche some of this plants may be lost with time reducing the population. Also, pioneer plants are mostly photosynthetic when some factors that favors photosynthesis such as temperature, light, Co2 concentration are not available there would be reduction in the pioneer species.

Competition between the old and new species may reduce it population if the old plant out compete them.

glamis thou art, and cawdor; and shalt be what thou art promis'd; yet do i fear thy nature; it is too full o' the milk of human kindness to catch the nearest way: thou wouldst be great; art not without ambition; but without the illness should attend it. what thou wouldst highly, that wouldst thou holily; wouldst not play false, and yet wouldst wrongly win: thou'dst have, great glamis, that which cries, "thus thou must do, if thou have it: and that which rather thou dost fear to do than wishest should be undone." hie thee hither, that i may pour my spirits in thine ear; and chastise with the valor of my tongue all that impedes thee from the golden round, which fate and metaphysical aid doth seem to have thee crown'd withal.  

he lacks ambition.  

he is hesitant.  

he lacks courage.  

he has moral scruples.

ur answer is in the it