  With the aim of providing the complete demography of galaxies in the local
Universe, including their nuclear properties, we present SPRING, a complete
census of local galaxies limited to the spring quarter of the Northern sky
(10h< RA <16h; 0< Dec <65). The SPRING catalogue is a flux- and volume-limited
sample (r < 17.7 mag, cz < 10000 km/s) of 30597 galaxies, including the Virgo,
Coma and A1367 clusters. To inspect possible secular and environmental
dependencies of the various nuclear excitation properties (SF vs. AGN), we
perform a multidimensional analysis by dividing the sample according to (i)
their position in the (NUV-i) vs. M* diagram,(ii) local galaxy density, (iii)
stellar-mass, (iv) halo-mass of the group to which galaxies belong, and (v)
neutral Hydrogen content. We present a new calibration of the optical
diameter-based HI-deficiency parameter employing a reference sample of isolated
galaxies. At intermediate distances between Virgo and Coma, we identify a
ring-like structure of galaxies constituted by three large filaments. The
fraction of HI-deficient galaxies within the filament suggests that filaments
are a transitioning environment between field and cluster in terms of HI
content. We classify the nuclear spectra according to the four-line BPT and the
two-line WHAN diagrams, and investigate the variation in the fraction of AGN
with stellar-mass, as well as their colours and environments. In general, we
observe that the mass-dependency of the fraction of Seyfert nuclei is little
sensitive to the environment, whereas the fraction of star-forming nuclei is a
steeper function of M* in lower-density environments and in blue-cloud
galaxies. We find that the fraction of LINERs depends on galaxy colour and, for
logM* > 9.5-10, increases in galaxies belonging to the green valley.
