( ( During ( drought periods ) ) ( , ( ( tree roots ) ( ( ( do not ) ( ( receive ( enough water ) ) ( to function ) ) ) . ) ) ) )
(ROOT (S (PP (IN During) (NP (NN drought) (NNS periods))) (, ,) (NP (NN tree) (NNS roots)) (VP (VBP do) (RB not) (VP (VB receive) (NP (JJ enough) (NN water)) (PP (TO to) (NP (NN function))))) (. .)))
During drought       periods, tree roots do not receive enough water to function.
(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)))))) (. .)))