4 2 .
Hes t Tamaki Rive r c a t c hmen t
The b ro a d a l t i tu d inal v e ge t a t ion z o n e s o f the , all o c c ur in t h i s
c a tc hmen t . S tr and ( 1 9 7 7 ) ha s a c om p r ehen sive l i s t o f t ional
s p e c i e s o c c ur r wi t hin t h e ca t c hm en t . H e n o t e s t ha t t he
h a r dwoo d f o r e s t o c c u r s t e l eva t io n s up to 6 0 0m a l i tu d e ,
a l t h e r e i s c o n s id e ra b l e overla p be twe en the t h r e e b r o a d z o n e s .
In l o ca l i t i es whe r e c l imax ex i s t s . s u c h as t h e
ha rdwo o d f o r e s t or kamahi f o r e s t . t h e t io n i s in a s t a t e
o f ra t . 1 Howev e r , t h e v e g e t a t ion i s a t many s i t e s c o n - tro l l e d e s ion , a n d i s i n v a r i o u s e r a 1 s ta g e s o f t . 1 1 ) .
ta t i o n on t h e s v a l l e y - s i d e s i s a f f t ed a dv e r s e n a t u r a l
cond i t ion s s S O L. . 1 and un s t ab l e s t ra ta , a s s ho wn in 2 .
Thi s f e s hows tha t v!h e r e the e d ec r ea se s a t t h e f o o t o f t h e
t h e r e i s a r e l a t d en s e v e g e ta t io n H e r e i t ioDs a r e
mor e s t ab l e , l l uv i um t end s t o a c c umu l a t e a n d s o i l s a r e d
Na t u r a l c o lon i sa t ion 0 b a r e sur f e s na t iv e i s In l t
domin a t e d t o t o e , ra , n e t t l e s , and f e rn s . I n 1 9 6 9 ,
the New Zea l a n d Fo r e s t S ervic e a r ev e g e ta t io n p r o g r amme w i t h exo t i c
a t s t ab i U. s s l f a c e s and conso l i d a t banks an d chan n e l
wa t er s e s . C o i s a t ion o f t h e s e s i t e s , i n t h e
former c a s e , and s and wi l l ows i n t he l a t t er s e , h a s b e en
suc c e s s f u l .
3 . 6 CLU1ATE
The Ruahine moun tain land a c o o l c l ima t e and annual rainfal l s . Wa ter i s the mos t impor tant o f ero s ion in thi s mounta in ran g e ; the r e l a t ion ship b etween mas s movement and
rainf a l l s New Z ea land w e l l e s tab l i shed ( e . g . 1 9 6 6 ; Gr an t , 1 9 6 6 ) . Ha t er , therefo r e , p l a y s an importan t ro l e in s o i l e r o s ion
4 3