||Understanding the mass-energy circulation between the chromosphere, transition region, and corona requires a detailed knowledge of the physical parameters of the plasma such as the non-thermal velocity, temperature, and density. Transition region and chromospheric emission line profiles were found to have two Gaussian components: a main core and a smaller broad component covering 25% of the line total intensity (Peter et al., 2000, A&A, 360, 761). Using data from the IRIS EUV spectrometer we investigated the line profiles of the Si IV 1394 and 1403 A lines in the chromospheric network. Based on the intensity, the network area is divided into three regions. Region 1 has intensities larger than 120 DN, region 2 - between 120 and 80 DN, and in the region 3 intensities are smaller than 40 DN (with average backgrounds less than 5 DN). The results show that there is no correlation between the intensities and the Doppler shifts in all three regions. However, the intensities and non-thermal velocities show correlations of 44%, 54%, and 46% for regions 1, 2, and 3 of the Si IV 1394 A emission line, respectively. The Intensities and non-thermal velocities of the Si IV 1403 A line have correlations of 35%, 44%, and 39% in the regions 1, 2, and 3, respectively. Region 2 in both lines has the highest correlation. This might be due to the presence of non-thermal horizontal flows in these regions. The results suggest that the dominant thermal mechanism in the chromospheric network might be via propagation of Alfven waves.