Dynamic changes of pear jujube stem diameter and path analysis of MDS influencing factors with full irrigation

To reveal the relationship between the variation of the maximum daily shrinkage (MDS) and the growth and development characteristics of pear jujube trees, field experiments were conducted to study the dynamic characteristics of trunk diameter for 3-year-old pear jujube with full irrigation. The path coefficients between MDS and meteorological factors (reference evapotranspiration ET0, daily mean temperature Tm, temperature at midday Tmd, daily mean vapor press deficitVPDm, vapor press deficit at midday VPDmd and net radiatio Rs) were analyzed and the main infuencing factors for precise irrigation schedule using MDS simulation equation were suggested. The results showed that the main reasons for trunk diameter changes were jujube’s life activity and the volatility of the meteorological factors. In practice, the tree’s invalid transpiration amount could be reduced and water use efficiency could be increased by pruning. Minimum daily trunk diameter (MNTD) increased significantly with fluctuation while maximum daily trunk diameter (MXTD) increased gently with time. The fluctuation intensity of MNTD was bigger than that of MXTD. Tm, VPDm and Rs had linear and positive influences on MDS as decision variables, and VPDm and Rs were the principal decision variables. ET0, Tmd and VPDmd were the bound variables which had negative influences on MDS, but the effect was not significant. So pear jujube tree’s growth and development could be improved by controlling temperature and sunshine, and VPDm and Rs should be given more consideration when establishing MDS simulation equations for precise irrigation. Some important factors that influenced MDS were not considered and these factors might include the other meteorological factors (such as relative humidity and daily temperature difference), the error of measuring and the phonological period and growth period of jujube, which were worth of further attention in further experiments.