\begin{tikzpicture}[every tree node/.style={draw,circle},sibling distance=.25cm]
\Tree
 [.$\forall x$ 
    [.$\forall y$
        [.$\imp$
            [.$\land$ 
                [.$P$
                    [.$x$ ]
                    [.$f$ $y$ ]
                ]
                [.$Q$ $y$ $z$ ]
            ]
            [.$R$
                [.$f$ $z$ ]
            ]
        ]
    ]
 ]
\end{tikzpicture}