Despite their small size the narrow growth rings indicate that the trees were mature plants which grew very slowly under harsh conditions.
(mature plants; grew; L:very slowly; L:under harsh conditions) (the narrow growth rings; indicate; that the trees were mature plants) Context(the narrow growth rings indicate,List([25, 57))):(the trees; were; mature plants which grew very slowly under harsh conditions)
the narrow growth rings indicate,List([25, 57))
mature plants the narrow growth rings the trees
grew indicate were
L:very slowly L:under harsh conditions
that the trees were mature plants
mature plants which grew very slowly under harsh conditions