Aims Global climate change will increase the uncertainty of precipitation patterns and affect the growth and distribution of plants.In the sub-humid and semi-arid areas of central China,black locust(Robinia pseudoacacia)plantations are widely planted in reforestation practices.These forests are vulnerable to climate change induced water stress.This research aims to clarify the responses of black locust transpiration to rainfall and soil water conditions.Methods To evaluate the responses of transpiration to precipitation changes,we measured and contrasted sap flow of black locust trees under throughfall exclusion treatment and the non-treated control in the Huaiping plantation forest of Yongshou County,a sub-humid area in Loess Plateau.Throughfall and soil moisture for both control and treatment plots were monitored.Waterproof panels were set in April 2015 for the treatment plot which excluded about 47.5% of the precipitation during the growing season.Stem sap flow in treatment and control plots have been measured since 2014 using Granier-type sensors.Meteorological factors including solar radiation,air temperature,and relative air humidity were monitored simultaneously outside the forest stand.Important findings Difference in soil moisture developed between treatment and control plots,the mean soil moisture content in treatment plot was 23.76%,lower than 22.59%(p < 0.001,n = 31)in the control plot during the middle growing season.Sap flux densities reduced following the treatment.The mean sap flux density under general weather conditions for the treatment plot was 1.64 mL·m~(-2)·s~(-1),not only lower than 2.42 mL·m~(-2)·s~(-1) of the previous year(before treatment),but also lower than 3.38 mL·m~(-2)·s~(-1) for control plot during the same period.The response patterns of sap flux density to solar radiation and vapor pressure deficit were also different,with the trees in treatment plot showing lower sensitivities to meteorological factors than those in the control plot.Our results show that transpiration of planted black locust trees was suppressed by the throughfall exclusion.The responses of transpiration to meteorological factors decreased compared with a pretreatment period or control plot.These results suggest that decrease in precipitation will not only reduce soil moisture,but may cause decreased transpiration,decreased responses to climatic variables,and lowered productivity as well.