\documentclass[11pt]{minimal}
\usepackage{tikz,tikz-qtree}
\newcommand{\xbar}[1]{$\overline{\mbox{#1}}$}
\newcommand{\features}[1]{
  $ \left[ \begin{array}{cl}
    \vspace{-1px}
    #1
  \end{array} \right] $
}
\newcommand{\f}[2]{
  #1 & {\mbox{#2}} \\
}
\begin{document}

\Tree
  [ .IP
    [ .NP [ .\xbar{N} [ .N He ] ] ]
    [ .\xbar{I}
      { I \features{\f{-}{Pst}} }
      [ .VP
        [ .\xbar{V}
          [ .\xbar{V}
            [ .V studies ]
            [ .NP [ .\xbar{N} [ .N linguistics ] ] ]
          ]
          [ .PP
            [ .\xbar{P}
              [ .P at ]
              [ .NP
                [ .Det the ]
                [ .\xbar{N} [ .N university ] ]
              ]
            ]
          ]
        ]
      ]
    ]
  ]

\end{document}