Abstract:

On an oak forest and grassland in the Tongshan forest farm in Nanjing, 4 sets EM50 were installed to measure the soil volumetric water content with which the Daily Average Soil Volumetric Water Content (DASVWC) was calculated at depths of 5, 15, 30 cm, respectively. Simultaneously air humidity was measured at the height of 2 m. By analyzing the vertical-temporal variable quantity, variations of DASVWC and their correlation with meteorological factors were found to be affected by precipitation, air temperature and humidity and DASVWC. The variation pattern was different from that in the Yellow River watershed, where variability of DASVWC at the 0-5 cm layers was lower than that at the 15 cm and 30 cm soil layers, while variability of DASVWC at the 0-5 cm layers in this study sites was higher than that at the 15 cm and 30 cm soil layers regardless of types of land use. DASVWC at the 0-30 cm soil layers in the oak forest was lower compared with that in the grass land, indicating that DASVWC at the surface soil layer decreased with increase of plant coverage. During rain intervals in different seasons, DASVWC exponentially decreased with time very significantly. The daily decrease in DASVWC showed multifactor linear regression with DASVWC, air temperature, humidity in each period.

Key words: oak forest, grass land, soil volumetric water content, daily average soil volumetric water content, land use type