The study of transpiration change and its relationship with environmental factors at different time scales is of great theoretical significance for understanding the driving mechanism of plant growth and estimating the water consumption of stands. In this study

eight sample trees were selected from Robinia pseudoacacia forest in Caijiachuan from May 2021 to December 2021 and thermal diffusion probe (TDP) was used to measure stem sap flow of Robinia pseudoacacia. Environmental factors such as solar radiation

air temperature

rainfall

soil temperature and soil water content were monitored synchronously. The characteristics of Robinia pseudoacacia transpiration and its response to environmental factors at different time scales (hour

day and month) were analyzed. The results showed that: (1) The relationships between transpiration and environmental factors were different at different time scales

on the whole

with the increase of time scale

soil water content became the main factor affecting transpiration. And the short time scale depended on surface soil water content

while the longtime scale depended on both surface soil water content and deeper soil water content. Hourly scale

the transpiration varied with the variation of solar radiation

air temperature

water vapor pressure deficit and soil temperature

but the peak value of transpiration and the peak value of environmental factors were different in time

and the time difference was up to -180 to 30 min. Among the environmental factors

solar radiation and air temperature had great influence on transpiration. At the daily scale

the transpiration rate increased with the increase of shallow soil water content

and shallow soil water content had a great influence on daily transpiration. At the monthly scale

the effect of shallow and deep soil water content on transpiration was more obvious. (2) In this paper

models of environmental factors and transpiration at different time scales were constructed

and the fitting degree of models at different time scales was high. (3) Based on this study

it is recommended to use instruments to measure plant transpiration at small scales

while plant transpiration can be calculated by monitoring fewer environmental factors at large scales

which can greatly improve efficiency and reduce the cost of monitoring water consumption of transpiration.