( ( During ( periods ( of drought ) ) ) ( , ( ( water ( the trees ) ) . ) ) )
(ROOT (S (PP (IN During) (NP (NP (NNS periods)) (PP (IN of) (NP (NN drought))))) (, ,) (VP (VB water) (NP (DT the) (NNS trees))) (. .)))
During periods of drought, water the trees.
(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)))))) (. .)))