  Since the launch of the Herschel Space Observatory, our understanding about
the photo-dissociation regions (PDR) has taken a step forward. In the bandwidth
of the Fourier Transform Spectrometer (FTS) of the Spectral and Photometric
Imaging REceiver (SPIRE) on board Herschel, ten CO rotational transitions,
including J=4-3 to J=13-12, and three fine structure lines, including [CI] 609,
[CI] 370, and [NII] 250 micron, are covered. In this paper, we present our
findings from the FTS observations at the nuclear region of M83, based on the
spatially resolved physical parameters derived from the CO spectral line energy
distribution (SLED) map and the comparisons with the dust properties and
star-formation tracers. We discuss (1) the potential of using [NII] 250 and
[CI] 370 micron as star-formation tracers; (2) the reliability of tracing
molecular gas with CO; (3) the excitation mechanisms of warm CO; (4) the
possibility of studying stellar feedback by tracing the thermal pressure of
molecular gas in the nuclear region of M83.
