  We present a detailed study of Near-IR selected galaxies in a protocluster
field at z = 3.13. Protocluster galaxies are selected using the available
mutliwavelength data with the photometric redshift (photo-z) at 2.9 < z < 3.3,
reaching a mass completeness of ~10^10 M_sun. Diverse types of galaxies have
been found in the field including normal star-forming galaxies, quiescent
galaxies and dusty star-forming galaxies. The photo-z galaxies form two large
overdense structures in the field, largely overlapping with the previously
identified galaxy overdensities traced by Ly{\alpha} emitters (LAEs) and Lyman
break galaxies (LBGs) respectively. The northern overdensity consists of a
large fraction of old and/or dusty galaxy populations, while the southern one
is mainly composed of normal star-forming galaxies which are spatially
correlated with the LAEs. This agrees with our previous study arguing the
spatial offset of different galaxy overdensities may be due to halo assembly
bias. Given the large end-to-end sizes of the two overdensities, one
possibility is that they will form into a supercluster by the present day. We
also find strong evidence that the star-formation activities of the galaxies in
the overdense protocluster regions are enhanced in comparison to their field
counterparts, which suggests an accelerated mass assembly in this protocluster.
