( ( The trees ) ( ( are ( evergreen ( as ( there ( is ( ( no period ) ( of ( ( drought or ) frost ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS trees)) (VP (VBP are) (VP (VBN evergreen) (SBAR (IN as) (S (NP (EX there)) (VP (VBZ is) (NP (NP (DT no) (NN period)) (PP (IN of) (NP (NN drought) (CC or) (NN frost))))))))) (. .)))
The trees are evergreen as there is no period of drought or frost.
(ROOT (S (SBAR (IN Because) (S (NP (NNS trees)) (VP (VBP add) (NP (NN water) (NN vapor)) (PP (TO to) (NP (NN air)))))) (, ,) (S (VP (VBG cutting) (PRT (RP down)) (NP (NNS forests)))) (VP (VBZ leads) (PP (TO to) (NP (NP (JJR longer) (NNS periods)) (PP (IN of) (NP (NN drought)))))) (. .)))